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    Re: Time For GIAC ECU Tuning?

    Alex, For factory tuned turbos the ECU can cope with 95RON and the timing will retard to cope etc with no damage.

    For RS Tuned cars their is a specific warning (see below) which states that 98RON must be used and if it is not available an Octane booster must be added. When I picked up my first engine in '97 and was heading to Italy (then land of teh 95RON) they actually gave me four cans of booster to use !

    So with the new mapping there is no enough ceiling (or is that "floor") for the ECU to wind back the timing enough to cope with lower than 98RON.

    I know they always comment on the fuels in the US and that is one of the reasons they are not interested in selling much over there.

    Interestingly they recently did the first North American 997GT2 with the 600PS tune and when they read the factory mapping it was so different to European that they actually had to install a GT2 engine onto the engine dyno and redo the programming, apparently it was all emmissions related stuff, but their comment was it was like comparing a Mercedes ECU to a beetle's (whatever that means !)

    oct.jpg

     

    Cannga

    I had thought of trying to explain why I think RS Tuning (and Ruf to a great extent) are so different to your two "big guns" in the US but I don't really know where to start since I guess it begins with what the cars are used for and tuning "for a market". You had some interesting questions about drivability which is 100% what RS and Ruf cars are about rather than peak power numbers.

    When Todd Z was selling parts for Powehaus, RS (Mr Schmirler) was busy inventing the Porsche twin turbo concept which went on to be the Ruf Yellowbird. RS use a very expensive (to buy and run) engine dyno set up which is the only way to tune and test engines to perform - the proof of this has to be the past and continued provenance of his race engines..... They are crazy money but should not be spoken about in the same breath as GIAC or EVOMS IMO ;)

    Have a look at the video below and ponder whether there are any US Porsche engine builders who have the facilities and knowhow to create such a monster...

    http://thepiratebay.org/torrent/3308571/Jurgen_Alzen_Motorsport_996_turbo(700hp)_1_Lap_Nurburgring

     


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For GIAC ECU Tuning?

    TB993tt:

    Alex, For factory tuned turbos the ECU can cope with 95RON and the timing will retard to cope etc with no damage.

    For RS Tuned cars their is a specific warning (see below) which states that 98RON must be used and if it is not available an Octane booster must be added. When I picked up my first engine in '97 and was heading to Italy (then land of teh 95RON) they actually gave me four cans of booster to use !

    So with the new mapping there is no enough ceiling (or is that "floor") for the ECU to wind back the timing enough to cope with lower than 98RON.

    I know they always comment on the fuels in the US and that is one of the reasons they are not interested in selling much over there.

    Interestingly they recently did the first North American 997GT2 with the 600PS tune and when they read the factory mapping it was so different to European that they actually had to install a GT2 engine onto the engine dyno and redo the programming, apparently it was all emmissions related stuff, but their comment was it was like comparing a Mercedes ECU to a beetle's (whatever that means !)

    oct.jpg

     

    Toby, so are you saying that if I use anything else apart from Shell V-Power (99 RON) then I am actually damaging the car?  This certainly isn't what Parr indicated to me:

    CarGraphic can only guarantee their figures when using 98 RON fuel, and after the upgrades have been done, it is definitely best to keep to this as strict as possible. No fuel system internals have been changed or modified so it should work with standard UK 95 fuel but we have not tested this so we can guarantee the results or effects. Especially with the European fuels, they do prove inconsistent at times.

    I do go out of my way to do this anyway, but I sometimes have to settle for 97 'super' at times from BP etc.

     


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    Re: Time For GIAC ECU Tuning?

    Alex........good question ?

    Could be a number of answers to this one:

    * You know I told you before about the stuff CG selling is not identical to what RS will sell you ? Maybe the CG mapping is slightly less aggressive and is OK with 95RON ?

    * Maybe CG/Parr do not really know and have not considered it ?

    * Maybe CG/Parr have considered it and decided that for UK use (ie no 5th/6th gear prolonged runs up to vmax in sub 25DegC ambient) it will not be a problem ?

    *Maybe RS just like to put warnings/disclaimers wherever they can so that they can wriggle out of prblems if they occur ?

    I would guess at the third one......

    I am presuming that the mapping tables allow a range of timing from extreme advance to extreme retard and that if you go high one way (ie advance) then it means you can't go as low the other way (ie retard) so if in 6th gear 35DegC ambient you are running WOT in Bavaria and your IAT on stock intercoolers goes to 80DegC there may not be enough in the 95RON to stop the onset of knock in these conditions.

    I would just use 97+RON and not worry

    BTW RS map using VPower 100RON so you can see how far "out" the 95RON will be...

     


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For GIAC ECU Tuning?

    Hmmm - what octane boosters did RS-Tuning give you Toby?  I think I need to start carrying some in the car with me for emergencies!  Most octane boosters don't add more than about 1.5 RON though, so 95 would only go to 96.5.

    I have just emailed back the question to Parr so I am interested to see what they respond with.


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    Re: Time For GIAC ECU Tuning?

    TB993tt:

    BTW RS map using VPower 100RON so you can see how far "out" the 95RON will be...

    So ideally I need to add octane booster to 99 RON V-Power here in the UK as only the rest of Europe gets 100 RON V-Power

    Saying that I am pretty sure 100 RON V-Power was not out when RS-Tuning brought my kit out.  So I assume they used 98 RON back then...


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    Re: Time For GIAC ECU Tuning?

    Alex

    Don't worry, just use 97+RON, you won't have any problems....

    Have a read of the link below, about octane boosters, its very interesting:

    http://members.rennlist.com/951_racerx/OctaneBoosterComparison.html


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For GIAC ECU Tuning?

    Alex

    After reading that link I posted and a bit more research I have ordered a box of the NF stuff for use on speed days etc.....

     

    http://cgi.ebay.co.uk/8x-NF-Nitrous-Formula-Race-Octane-Booster---Up-to-6-RON_W0QQitemZ370117507387QQcmdZViewItem


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For GIAC ECU Tuning?

    Parr's response:

    I`ve double checked with CarGraphic and using 95 RON shouldn`t damage  your engine in any way. The ECU upgrade that was carried out was designed with 98 RON, so their BHP figures can only be quoted when using this fuel. All your fuel system components are the same, and have been designed with 95 RON in mind, however when possible we would recommend using the 98 RON fuel, but don`t worry about 95 on the odd occasion


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    Re: Time For GIAC ECU Tuning?

    Alex_997TT:

    Parr's response:

    I`ve double checked with CarGraphic and using 95 RON shouldn`t damage  your engine in any way. The ECU upgrade that was carried out was designed with 98 RON, so their BHP figures can only be quoted when using this fuel. All your fuel system components are the same, and have been designed with 95 RON in mind, however when possible we would recommend using the 98 RON fuel, but don`t worry about 95 on the odd occasion

     

    What does "don't worry about 95 on the odd occasion" mean ? This is super flakey IMO - what happens if that "odd occasion" is the 6th gear high temp 'bahn blast I mentioned before - "odd occasion" should not enter it, it either is 100% safe within the timing/knock detection safety nets or it is not and if it is not then knock can destroy an engine in micro seconds....


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For GIAC ECU Tuning?

    Protomotive 997 turbo

    http://www.youtube.com/watch?v=3zWS1orB6Z8


    Re: Time For ECU Tuning?

    For those new to this (like me), what Toby is talking about is the concept of ignition timing.
    My basic level knowledge (any expert feels free to correct and add): Ignition timing and boost are the 2 major parameters that tuners manipulate to get more power out of your car. Ignition timing determines how efficient the engine is and how much power could be achieved. Grossly the concept is that advancing ignition timing is good, as long as there is no knock/detonation (very bad -- this is combustion when the piston is moving up), so what you do is advancing the timing until there is knock, then you back off -- retard the timing.
    For example, with 95 RON gas, the timing is retarded, otherwise there would be knock; for 98 RON gas, by definition more resistant to knocking, the timing is advanced (more power).

    So the tuners create ignition timing "maps" for each level of octane rating. How does the engine know what octane the gasoline is? It does not, since there is no such thing as an "octane" sensor. What it does know is how much knocking there is, as measured by the knock sensor. If it doesn't sense any knocking, it would use, say the 98 map. If it does sense knocking, it would use a map with more retarded timing, for example the 95 map.

    The question is then, did RS Tuning create the ECU using 95 RON gas? If it does not, then the concern is one, whether its map would provide enough retardation, and two, even if it does, it may not be that good since they didn't fine tune it by actually using 95 RON gas.

    I hope I am making sense and this doesn't sound like senseless rambling. Smiley There is a much better explanation in Wikipedia.


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    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Time For ECU Tuning?

    Wikipedia article on ignition timing:

    Ignition timing, in a spark ignition internal combustion engine, is the process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity.

    Setting the correct ignition timing is crucial in the performance of an engine. The ignition timing affects many variables including engine longevity, fuel economy, and engine power. Modern engines that are controlled by an engine control unit use a computer to control the timing throughout the engine's RPM range. Older engines that use mechanical spark distributors rely on inertia (by using rotating weights and springs) and manifold vacuum in order to set the ignition timing throughout the engine's RPM range. There are many factors that influence ignition timing. These include which type of ignition system is used, engine speed and load, which components are used in the ignition system, and the settings of the ignition system components. Usually, any major engine changes or upgrades will require a change to the ignition timing settings of the engine.

    Setting the ignition timing

    Timing light

    "Timing advance" refers to the number of degrees before top dead center (BTDC) that the spark will ignite the air-fuel mixture in the combustion chamber during the compression stroke. Retarded timing can be defined as; changing the timing so that fuel ignition happens later than the manufacturer's specified time. If the ignition timing, specified by the manufacturer, was to be set at 12 degrees BTDC and it was adjusted to a number lower than 12 degrees BTDC, it would be retarded. In a classic ignition system with breaker points, the basic timing can be set statically using a test light or dynamically using a timing light.

    Timing advance is required because it takes time to burn the air-fuel mixture. Igniting the mixture before the piston reaches top dead center (TDC) will allow the mixture to fully burn soon after the piston reaches TDC. If the air-fuel mixture is ignited at the correct time, maximum pressure in the cylinder will occur sometime after the piston reaches TDC allowing the ignited mixture to push the piston down the cylinder with the greatest force. Ideally, the time at which the mixture should be fully burnt is about 20 degrees ATDC. This will utilize the engine's power producing potential. If the ignition spark occurs at a position that is too advanced relative to piston position, the rapidly expanding air-fuel mixture can actually push against the piston still moving up, causing detonation and lost power. If the spark occurs too retarded relative to the piston position, maximum cylinder pressure will occur after the piston is already traveling too far down the cylinder. This results in lost power, high emissions, and unburned fuel.

    The ignition timing will need to become increasingly advanced (relative to TDC) as the engine speed increases so that the air-fuel mixture has the correct amount of time to fully burn. As the engine speed increases, the time available to burn the mixture decreases but the burning itself proceeds at the same speed, it needs to be started increasingly earlier to complete in time. Poor volumetric efficiency at lower engine speeds also requires increased advancement of ignition timing. The correct timing advance for a given engine speed will allow for maximum cylinder pressure to be achieved at the correct crankshaft angular position. When setting the timing for an automobile engine, the factory timing setting can usually be found on a sticker in the engine bay.

    The ignition timing is also depending on the load of the engine with more load (larger throttle opening) requiring less advance (the mixture burns faster). Also it is depending on the temperature of the engine with lower temperature allowing for more advance. The timing the mixture burns depends on the Octane rating of the fuel and also the air/fuel ratio.

     

    Dyno tuning

    Setting the ignition timing while monitoring engine power output with a dynamometer is one way to correctly set the ignition timing. After advancing or retarding the timing, a corresponding change in power output will usually occur. A load type dynamometer is the best way to accomplish this as the engine can be held at a steady speed and load while the timing is adjusted for maximum output.

    Using a knock sensor to find the correct timing is one method used to tune an engine. In this method, the timing is advanced until knock occurs. The timing is then retarded one or two degrees and set there. After achieving the desired power characteristics for a given engine load/rpm, the spark plugs should be inspected for signs of engine detonation. If there are any such signs, the ignition timing should be retarded until there are none.


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    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)


    Re: Time For ECU Tuning?

    cannga:

    The question is then, did RS Tuning create the ECU using 95 RON gas? If it does not, then the concern is one, whether its map would provide enough retardation, and two, even if it does, it may not be that good since they didn't fine tune it by actually using 95 RON gas.

    RS-Tuning and Ruf would have created the ECU mapping based on 98 RON petrol.  Just like Porsche did for the stock Turbo to achieve the 480 PS from the factory, but Porsche would have done extensive testing with lower octane petrol also that the tuners would not have.

    So the real question is can the tuners re-map still adjust downwards for lower octane petrol just like the stock car can?  I guess the answer to that is yes but the re-map is more sensitive to such changes and so is not recommended.

    I note in the Turbo's Drivers Manual it talks about what fuel to use.  It says you should use 98 RON,  but 95 RON is ok as the engine can adjust the timing downwards.  It then goes on to talk about how it can use 91 RON but then Porsche approved octane boosters should be used - and they actually quote a Porsche part number for this!

     


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    Re: Time For ECU Tuning?

     

    A good readable explanation Can - thanks for clarifying 
    I will share my simplistic thought process on timing as it may help others who are similarly handicapped J
    The piston comes up towards the combustion chamber and when it is a top dead centre this is 0 degrees.
    If the spark fires before the piston hits TDC then this is advanced timing and because the piston is still “squashing” the mixture upwards as the spark is fired it makes it a more efficient burn as more fuel/air mixture can be squirted in the greater volume (compared to TDC) which is there.
    The retarding bit is a bit more simple, simply the spark fires when the piston has gone past TDC and is on the way down. Once the piston is on the way down the compression ratio of the engine (ie how much “squash” the mixture had) rapidly diminishes so for example if there was too much boost (on a fixed boost explodamotor for example) the ECU lets the piston drop past TDC and fires the spark when the compression ratio (squash) drops and this makes it a safe burn. It is this high compression ratio (brought about by too much boost for the static CR) which in combination with heat needs the combustability of the 98RON+ otherwise the knock will occur.
    I understood there were limits to how far the ECU can retard from the furthest advance setting, (I think it was 7 degrees on the 993tt engine) so the further advance you go the less retard is available and with the tuner engines the retard available is not enough to cope with the lower RON fuels…

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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For ECU Tuning?

    TB993tt:

     

    A good readable explanation Can - thanks for clarifying 
    I will share my simplistic thought process on timing as it may help others who are similarly handicapped J
    The piston comes up towards the combustion chamber and when it is a top dead centre this is 0 degrees.
    If the spark fires before the piston hits TDC then this is advanced timing and because the piston is still “squashing” the mixture upwards as the spark is fired it makes it a more efficient burn as more fuel/air mixture can be squirted in the greater volume (compared to TDC) which is there.
    The retarding bit is a bit more simple, simply the spark fires when the piston has gone past TDC and is on the way down. Once the piston is on the way down the compression ratio of the engine (ie how much “squash” the mixture had) rapidly diminishes so for example if there was too much boost (on a fixed boost explodamotor for example) the ECU lets the piston drop past TDC and fires the spark when the compression ratio (squash) drops and this makes it a safe burn. It is this high compression ratio (brought about by too much boost for the static CR) which in combination with heat needs the combustability of the 98RON+ otherwise the knock will occur.
    I understood there were limits to how far the ECU can retard from the furthest advance setting, (I think it was 7 degrees on the 993tt engine) so the further advance you go the less retard is available and with the tuner engines the retard available is not enough to cope with the lower RON fuels…

    Sorry TB993tt, but your explanation of ignition timing contains too many incorrect assumptions and misunderstandings to be allowed to stand as it is. I am also not an engine specialist, so the information below may not be correct in all details and most certainly not exhaustive, but it will be nearer the mark:

    The ignition point is conventionally quoted in terms of degrees before TDC (top dead center) between the compression and power strokes, but ignition always takes place before TDC, so it is not the case that “advance” and “retard” refer respectively to points before and after TDC.
     
    The use of these terms goes back to the days of distributors and contact-breaker points, when the points were set to open at a “static” point which might typically have been about 5 to 10° before TDC, according to manufacturer’s recommendations. Depending on the quality of the fuel available, it might be possible to advance the static timing point a couple of degrees to increase torque without causing pre-ignition or “knocking” or it might be necessary to retard the timing a couple of degrees to eliminate knocking.
    Additionally, distributors were typically equipped with (a) a system to further advance the spark with increasing engine speed using centrifugal weights, plus (b) a system to further advance the spark with decreasing inlet manifold pressure (normally aspirated engines), thus constantly adapting the ignition timing to actual engine speed and load conditions during operation. At high speed and load conditions, the ignition point might be more than 40° before TDC. It would never be after the static point mentioned above, therefore also never after TDC.

    The “compression ratio” of any given engine is a fixed figure, so to speak of it diminishing during the operating cycle is incorrect and only serves to confuse the issue.

    Modern electronic ignition systems have, of course, made the distributor and its centrifugal and vacuum advance systems with all their sensitivities to production tolerances, wear, air leaks, etc., redundant. They rely, like electronically controlled fuel injection systems, on being able to take the timing data they need out of electronic three-dimensional “lookup tables”. If a knock-sensor detects pre-ignition as a result of low grade fuel being used, then the timing of the spark is temporarily delayed or “retarded” to a point where knocking no longer occurs.
     


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    fritz


    Re: Time For ECU Tuning?

    fritz - thanks for the extra lesson - I still like my simplistic "overview"

    Regarding the compression ratio, it is an issue which does need to be "confused" in a turbo engine IMO since the importance of the effective CR as a consequence of boost is an important component in the timing isuse and by retarding the spark it does effectively reduce the CR from the fixed figure doesn't it ? Isn't this the primary mechanism by which knock is defeated ?


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For ECU Tuning?

    TB993tt:

    fritz - thanks for the extra lesson - I still like my simplistic "overview"

    Regarding the compression ratio, it is an issue which does need to be "confused" in a turbo engine IMO since the importance of the effective CR as a consequence of boost is an important component in the timing isuse and by retarding the spark it does effectively reduce the CR from the fixed figure doesn't it ? Isn't this the primary mechanism by which knock is defeated ?

    This is getting too complex for a forum post, and I'm not really the right person to try to explain it anyway. Smiley  You do seem to be confused about some of the technical terms you use, and about the combustion process.  

    Where to start? Smiley

    You will agree that the "mechanical" compression ratio always remains fixed for a given engine. (Internal volume of combustion chamber and cylinder with piston at BDC : volume of combustion chamber with piston at TDC).

    Where a turbocharged engine is concerned, the air is additionally compressed before it gets into the cylinder. The ratio of the volumes of the air before compression in the turbo and after compression varies with the operating conditions (load, speed, etc.), so there is no fixed "compression ratio" for a turbocharger. However, for the sake of this explanation, let's assume a "momentary" compression ratio of 1.5 for a given set of operating conditions.
    Combine this ratio of 1.5:1 with a "mechanical " compression ratio of 8:1, for example, and you arrive at an "Effective Compression  Ratio" of 12 to 1. (Volume of cool free ambient air before induction into the turbo to volume of compressed air in combustion chamber with piston at TDC.

    Due to this higher Effective Compression Ratio, this same basic engine operated first with and then without the turbocharger could not be operated efficiently with the same injection/ignition control software. (We'll leave the valve timing and lifts out of this completely!). I think you were alluding to this difference in your post.

    So both the Compression Ratio and the Effective Compression Ratio for a given turbo engine under a given set of operating conditions are "fixed" before the air/fuel mixture is ignited, and therefore cannot be influenced by the ignition timing.
    What can be influenced, and what you probably had in mind when you referred to "reduce the CR", is the pressure peak in the combustion gases during the power stroke. Earlier ignition causes "pre-ignition" of the mixture, resulting in a very high "inefficient" pressure peak which does not add to the torque available at the flywheel. Later, optimal ignition timing results in smoother, more efficient combustion, and lower shock loads on the piston, wrist pin, bearings, etc...

     

     

     


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    fritz


    Re: Time For ECU Tuning?

    Fritz

    Why is this stuff too complex for a "forum post" -I am interested what you think this forum is for, should we not be attempting these subjects on here ?

    The way you pop up every time I attempt a simplistic answer to techy stuff is quite amusing, you start by telling me I am misunderstanding and confused then go on to explain the subject much better than me but essentially the same thing...... Why don't you post this stuff in the first place ? You seem to lack the confidence and only come out to play when you can start your post with some (pretty silly) put downs - I bet you are a real hoot to have around

    You still didn't tell me whether I was correct in saying that the effective CR decreases when the timing is retarded - by virtue of the piston falling away from the combustion chamber and TDC, does this happen or am I just confused ?


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For ECU Tuning?

    TB993tt:

    Fritz

    Why is this stuff too complex for a "forum post" -I am interested what you think this forum is for, should we not be attempting these subjects on here ?

    The way you pop up every time I attempt a simplistic answer to techy stuff is quite amusing, you start by telling me I am misunderstanding and confused then go on to explain the subject much better than me but essentially the same thing...... Why don't you post this stuff in the first place ? You seem to lack the confidence and only come out to play when you can start your post with some (pretty silly) put downs - I bet you are a real hoot to have around

    You still didn't tell me whether I was correct in saying that the effective CR decreases when the timing is retarded - by virtue of the piston falling away from the combustion chamber and TDC, does this happen or am I just confused ?

    I've already regretted the fact that I bothered to respond to your first post, but I guess I'm committed now. I wrote that this topic is too complex for a forum post because, in order to get points across briefly and clearly, the participants need to have some knowledge of the physics involved and a clear understanding of the terminology used.

    It would not be productive to comment on your second paragraph, so I'll restrict my answer to the "techy" points.

    I did in fact address your theory re "effective CR decreasing when timing is retarded".  I'll just quote the summary:

    "So both the Compression Ratio and the Effective Compression Ratio for a given turbo engine under a given set of operating conditions are "fixed" before the air/fuel mixture is ignited, and therefore cannot be influenced by the ignition timing.
    What can be influenced, and what you probably had in mind when you referred to "reduce the CR", is the pressure peak in the combustion gases during the power stroke".

    On re-reading that, I still think I'd explained it fairly clearly within the limitations of an internet forum post, but again it comes down to a question of correctly understanding the terminology used in order to be able to follow the explanation. If a basic knowledge of the physics involved cannot be taken as a given, then a thorough explanation would involve writing a post of text-book length and, as I implied in my first post, I don't see myself as an academic anyway. Saying that in plain words is not in any way meant to be a put-down. It's just that I generally try to avoid being so subtle that my message gets misunderstood in a flowery text.  

    You started your first post on this particular topic with the sentence: "I will share my simplistic thought process on timing as it may help others who are similarly handicapped".
    If you seriously believe that others will not join in with their own 2 cents if they consider that your thoughts are more inclined to mislead others than to help them, then parhaps you need to review your own concept of what the forum is for.


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    fritz


    Re: Time For ECU Tuning?

    I think you are right about the terminology - you have not written anything so far which IMO conflicts with what I was trying to say but obviously my terminology is not good - your explanations are more technically correct but things like compression ratio for me in a turbo motor would always mean the actual CR which is present at each ignition not the fixed (is that called static ?) CR which I guess I thought everyone knew is a given ?

    You wrote this:

    "So both the Compression Ratio and the Effective Compression Ratio for a given turbo engine under a given set of operating conditions are "fixed" before the air/fuel mixture is ignited, and therefore cannot be influenced by the ignition timing.
    What can be influenced, and what you probably had in mind when you referred to "reduce the CR", is the pressure peak in the combustion gases during the power stroke".

    Again I am sure your terminology is correct but what you call "pressure peak" can easily be related to effective CR present at each ignition and I was trying to make it simple Smiley

    Also the effective CR can be influenced by the ignition timing (not for that stroke but following strokes) since the boost will be reduced by the ECU if following an ignition if knock onset is detected (although I am pretty sure the ECU cannot reduce boost fast enough and it is timing which is retarded first) So is it not corect to say that if one had fixed ignition timing on this engine and knock was detected then the ECU would reduce boost and hence effective CR ?

    Can anyone else step in and tell me if my explanations really are that bad and incoherent ?

     


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    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For ECU Tuning?

    TB993tt:

    I think you are right about the terminology - you have not written anything so far which IMO conflicts with what I was trying to say but obviously my terminology is not good - your explanations are more technically correct but things like compression ratio for me in a turbo motor would always mean the actual CR which is present at each ignition not the fixed (is that called static ?) CR which I guess I thought everyone knew is a given ?

    You wrote this:

    "So both the Compression Ratio and the Effective Compression Ratio for a given turbo engine under a given set of operating conditions are "fixed" before the air/fuel mixture is ignited, and therefore cannot be influenced by the ignition timing.
    What can be influenced, and what you probably had in mind when you referred to "reduce the CR", is the pressure peak in the combustion gases during the power stroke".

    Again I am sure your terminology is correct but what you call "pressure peak" can easily be related to effective CR present at each ignition and I was trying to make it simple Smiley

    Also the effective CR can be influenced by the ignition timing (not for that stroke but following strokes) since the boost will be reduced by the ECU if following an ignition if knock onset is detected (although I am pretty sure the ECU cannot reduce boost fast enough and it is timing which is retarded first) So is it not corect to say that if one had fixed ignition timing on this engine and knock was detected then the ECU would reduce boost and hence effective CR ?

    Can anyone else step in and tell me if my explanations really are that bad and incoherent ?

    As I thought, you are using "CR" when you are really thinking of "pressure".  Whereas pressure is a property measured in units such as pounds per square inch (to use the old Imperial units), compression ratio is just an "unit-less" figure expressed, for instance, as "10.5", meaning a ratio of  10.5 to 1.
    You'll probably think that I'm just being a nit-picking pedant again when I say that confusing those two things ist like trying to add together  yards and hours in an arithmetic calculation, and is the sort of thing which would make a physics teacher cringe. Smiley

    What you are trying to describe is the process whereby, when a sensor detects knock in an engine, the ignition timing is retarded for subsequent power strokes, so that the pressure rise in the combusting gases in subsequent cycles is not so rapid that it causes pre-ignition.

    Limiting boost pressure is not used to eliminate knocking, but to restrict mean effective cylinder pressure (which is directly proportional to engine torque) to a level which the engine can mechanically withstand.

    I think any others reading this who could usefully add to the discussion are very wisely staying well away. Smiley  Ferdie, you coward. Smiley


    --

    fritz


    Re: Time For ECU Tuning?

    You are of course right about my use of CR and being a pedant

    What you are trying to describe is the process whereby, when a sensor detects knock in an engine, the ignition timing is retarded for subsequent power strokes, so that the pressure rise in the combusting gases in subsequent cycles is not so rapid that it causes pre-ignition.

    No I don't think this is what I am describing, I mean the ECU reduces boost BECAUSE of the knock detection (which obviously has the effect of reducing pressure rise....

    Limiting boost pressure is not used to eliminate knocking, but to restrict mean effective cylinder pressure (which is directly proportional to engine torque) to a level which the engine can mechanically withstand.

    But the ECU does also reduce boost for higher IATs and I presumed in response to knock detection also - is this not the case ?

    It would be great for others to join in

     


    --


    2009 997 GT2 RS Tuning 542PS/736NM


    Re: Time For ECU Tuning?

    Fritz and Toby, thanks for the interesting info.

    I would recommend anyone planning to do an ECU tune to read some of the postings here. Ignition timing (and boost) is central to ECU tune, and understanding at least the simplistic view makes the process more educational. You are already spend the $$, might as well learn something.

    FWIW I think *my* simplistic view is vastly more simplistic than Toby's simplistic view, and therefore is "better."  


    --
     

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + ECU Tune (???) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)



    Re: Time For ECU Tuning?

    cannga:

    Fritz and Toby, thanks for the interesting info.

    I would recommend anyone planning to do an ECU tune to read some of the postings here. Ignition timing (and boost) is central to ECU tune, and understanding at least the simplistic view makes the process more educational. You are already spend the $$, might as well learn something.

    FWIW I think *my* simplistic view is vastly more simplistic than Toby's simplistic view, and therefore is "better."  

     

    Extract from Wiktionary entry for "simplistic":

    "simplistic implies simplicity to excess".

    Are you sure that you still want to claim that distinction? Smiley


    --

    fritz


    Re: Time For ECU Tuning?

    ^^^ I simply want to point out the the elegant simplicity of my post, but perhaps was guilty of being overly simplistic.  Smiley


    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + ECU Tune (???) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)



    Re: Time For ECU Tuning?

    cannga:

    ^^^ I simply want to point out the the elegant simplicity of my post, but perhaps was guilty of being overly simplistic.  Smiley


    And I just used the Wiktionary definition of "simplistic" to jokingly query the virtue of simplistic interpretations but, as so often happens on the internet, this appears to have been misunderstood. Smiley
    It's not worth doing a post-mortem examination on, so let's just forget it.   Smiley
     


    --

    fritz


    Re: Time For ECU Tuning?

    Back to regular programming. Again I am an amateur so any expert PLEASE feel free to correct as needed.
    The discussion of ignition timing  leads to another major topic: the fundamental difference between how GIAC and EVOMSit (the 2 US big guns) load their ignition timing maps, and how users interact with the program.

    >>>>>>>>>>>>>>>>>>>>
    GIAC: Remember the first post of this thread, right? It's about the Flash Loader used by GIAC. In fact, what the Flash Loader is, is simply a memory bank that stores many different ignition timing maps, 4 maps for lower octane gas (91), 4 maps for mid level octane gas (93), and 4 maps for really high octane gas (race).
    The claimed benefit of this system: The maps are closely grouped around the target octane level. I believe "higher resolution" is the pharase that was used to describe this. So if you are running on 93, you load the 93-specific maps, which in fact has 4 maps designed for 93 to 98 octane, and so on. If you then swich to race gas, you HAVE TO use the Flash Loader to load the 4 maps specific to race gas.
    If you have done your homework and read the posts on ignition timing above, you would now think: in theory, the potential danger of this system is that it would be bad if you load the race gas maps and accidentally have 91 gas in the car's tank. In practice, there was an anecdotal report that this has happened without resulting in damage.

    >>>>>>>>>>>>>>>>>>>>>>>
    EVOMSit: All the ignition timing maps for different octane levels are loaded in your car, from 91 to race.The car will switch automatically, using feedback from the knock sensor, to a map appropriate to the gas that's in the tank. You don't have to do anything when you switch from say 93 gas to race gas; the car switches automatically. Incidentally, a majority of ECU tune is like EVOMS -- automatic switching, and the Flash Loader concept is basically used only by GIAC.

    Which system is better? I don't know.

    --

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + ECU Tune (???) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)



    Re: Time For ECU Tuning?

    Go for the EVO !


    --

    Doug

    Houston, Texas USA 

    997TT ...RUF550


    Re: Time For ECU Tuning?

    TT Gasman:

    Go for the EVO !

    Pssssss... please don't give my secret away! Your valuable experience helps; thanks again. (TT Gasman is one of the few people, perhaps the only one, who have driven 3 different ECU tunes: GIAC, FVD, and now, his fantastic Ruf conversion.)
    Kidding aside, we'll see how I like it but yes EVOM has come on the US tune scene in a big way. I am mildly shocked that they announced their 47th EVT700 conversion -- announcement here. That's a lot of cars! Even more shocking considering they just come on the scene 6-7 months ago.

    For those who don't know: IIRC the EVT700 is the same ECU tune package that is in forum member shavster's car -- the car with the beautiful Matini Racing wrap job that was reviewed in a magazine a while back. This package includes all 4 stages of upgrading, that I will touch on later: exhaust, header, intercooler, bigger turbo. Yes these 4 stages comprise sort of a nutty scale. The higher you go, the more nuttty you are.  Smiley


    --
     

    Regards,
    Can
    997 Turbo + Bilstein Damptronic (Review) + ECU Tune (???) + Cargraphic Exhaust (Heavenly Race Car Noise Smiley Review)



    Re: Time For ECU Tuning?

    FVD??  Not sure, but  I did drive the PES, which may be the same thing.


    --
     

    Doug

    Houston, Texas USA 

    997TT ...RUF550


     
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