allset
Go Kart Champion
very simplified:
more timing advance is what creates power, it allows for more force on the down stroke. Boost is an means to an end, that end being HP created by the downstroke to the crank
Last edited:
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GTI Data Logging Compendium
- Thread starter A_Bowers
- Start date
very simplified:
more timing advance is what creates power, it allows for more force on the down stroke. Boost is an means to an end, that end being HP created by the downstroke to the crank
Arin@APR
GOLFMK7 Official Sponsor
Max possible boost on a turbo will always look like a triangle when plotted against RPM. The k04 is not large enough to hold 24 PSI all the way to redline. If one were to pick the boost level capable at redline, they would really limit loads of mid range boost and more importantly, mid range power.. This is where you spend most of your time driving, so we are giving you more "area under the curve" so to speak. By ramping in boost quickly we are able to get you moving quickly when you hit the throttle to pass on the highway.
Arin@APR
GOLFMK7 Official Sponsor
Stage 3+ runs more boost than the k04. Which makes more power? ;-)
When you start getting into very high octanes, you can easily reach A point where ignition is advanced so far, it hurts power.
allset
Go Kart Champion
sorry man, I'm frustrated beyond words...
A_Bowers
Moderator
NBD, I know things can get heated, I'm just trying to direct them to the appropriate threads.
Hi
This is a very interesting thread.
I thought I'd attach some logs of my 2011 GTI with the following mods: Apr K04, Apr intercooler, ITG large intake, 76mm full exhaust, and devils own water injection.
For comparison, I have logs at sea level and 1800m above sea level. These were done on the 104 octane file.
This is a very interesting thread.
I thought I'd attach some logs of my 2011 GTI with the following mods: Apr K04, Apr intercooler, ITG large intake, 76mm full exhaust, and devils own water injection.
For comparison, I have logs at sea level and 1800m above sea level. These were done on the 104 octane file.
Attachments
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ImageUploadedByTapatalk 21366882153.725693.jpg
Wow. That's quite a difference!
B
Bronson@APR
Guest
I posted it in the other thread but I'll do it here too, you want the most powerful combustion possible. The formula to make torque is f(x) = YBoost + XTiming + ZAir/Fuel, where f(x) = combustion.
For every combustion, you're exerting torque on the crankshaft by the force against the piston. Advancing timing, running leaner (to an extent with the appropriate hardware) can increase power. In my experience, an FI engine is going to prefer boost pressure due to it's engine characteristics and original design intent. This is why larger turbo cars will make more power (in simple terms). You can run as much timing as you want and run the car lean, but eventually you're just going to need more air to continue forward.
All 3 components have a sweet spot, for boost it is the turbos effective range, timing is mean best timing (MBT) range and lambda is lean best torque. Moving one of the 3 components effects the other 2 and the relative effect on the combustion which also moves with engine speed. The key is to sit on a dyno and spend time finding where it all fits together, it isn't unusual for 2 different tuning companies to end up with a different solution and use different methods while both making good power, everybody is ultimately handicapped by hardware. You're not tuning for pressure, timing or a certain lambda, you're going for the highest overall mass air flow rate.
I assure you it is all much more complex than this, largely because of the ECU in these cars (MED17) but this is a general/simple break down of tuning philosophies and what makes power. I figured I'd type up these few paragraphs because the forum members made this thread to learn and share data, one of the things that drew me to APR was their willingness to share info on these public forums, so I figured I'd continue the trend.
grambles423
Automotive Engineer
Formula Just for people to see it:
Brake Horsepower (Watts) = N*Displacement* (RPM/2)* nc*nm*nth*nv*Qhv*(F/A)*Air Density
N = Number of cylinders
Displacement = Bore*Stroke*pi/4
RPM/2 = Must be placed in Revs/Second = RPM/2 * (1/60 {s/min})
nc = Combustion efficiency = about .98-.99 on newer cars (can be calculated further, but these estimations are fine)
nm = mechanical efficiency = Function of RPM/heat/etc range of about .8-.93 (can be calculated further, but these estimations are fine)
nv = volumetric efficiency (what percentage is your TB open?)= 100% at WOT (Possibly a little more depending on the flow. Most I've seen is 108%)
nth = thermal efficiency = 0.8*(1-[compression ratio^(-.35)])
Qhv = Heating value of the fuel = 43,000,000 J/kg
F/A = Fuel Air Ratio
Air Density = Pressure Entering / (287.2 J/kg-K * Intake Air Temperature)
Pressure Entering = Atmospheric Pressure * Pressure Ratio (This is a function of RPM) - J/m^3
A_Bowers
Moderator
Awesome synopsis Bronson.
B
Bronson@APR
Guest
Timing isn't simple on these cars, largely in part to the complex ECU.
I assure you, there is much more than 1 timing map, there is also many maps to regulate how timing is compensated for, how it is pulled, the sensitivity of the knock recognition and even how quickly it is added back after it was pulled. Heck, there is a max referenced load request 2d map that is used under knock recognition that sets a cap on multiple 3d maps used when the ECU senses the driver is requesting torque and another that is used with no knock recognition. For every component that makes power, there is a secondary map to be referenced if the ECU recognizes a knock event.
The philosophy of every tuner is different, it isn't a simple answer to determine one tuner is more aggressive because there's so many different variables that need to be looked at. They both can be more aggressive in different ways.
Anyway, the timing pull you see in VCDS isn't indicative of engine damage or a true knock event. The tiny microphone (aka knock sensor) filters a lot of noise, mainly because engines are noisy and to decipher what is dangerous and what is normal operation. The ECU knows when each cylinder is coming to TDC, it focuses on this noise per each cylinder. It was originally calibrated by the OEM based off of much testing, it is determined by engine bore, a host of other engine properties and the amplitude of the noise picked up on it's respective knock recognition graph. The OEM knows what knock sounds like, they have it dialed in perfectly. They base CF off of avoiding harmful engine knock, they have it set so that in all engine operations, pulling -12 per any one cylinder is enough to bail itself out given proper running conditions and that you're using the minimum required AKI fuel.
So let's say that 50 units of sound is a *possible* knock event, you could say that if the engine recorded 39 units of sound on cylinder 4, it would show -1.5 CF on cylinder 4. It would pull 2 units of -0.75, as it pulls timing by increments -0.75 degrees, and in the timing maps you add timing by increments +0.75. This would then in simple terms, be added to adaptation data after enough events and driving cycles. So the ECU has 16 units of -0.75 before it gets to the point where there is any potential harm.
This isn't a textbook explanation, just something I felt like writing on a Thursday morning to clear up any questions about timing pull and timing advance.