Fueling limitations of the 2.0T FSI and lack of gains from exhaust and testpipe discussed....

[bhvrdr]

I was conducting testing on my car last year and came to a conclusion that it appears many others are now seeing. Many people who add testpipe and exhaust on STOCK programming have seen HUGE gains so we know gains can be seen there and it has little to do with programming. EXAMPLE OF THIS: Stock programmed 2.0T FSI car run baselined and with testpipe only added.... But, when people add perf software and then an exhaust and testpipe very little gains are seen. I suspect this is because a very well tuned program is pushing the max fueling by itself. APR and other companies will have a fuel pump and other options available. EXAMPLES: Stock programmed vehicle baseline versus dyno of same vehicle with APR software... Now take this same vehicle and add a full 2.75" exhaust with straight through mufflers. Very little if any gains are seen. In fact an insignifican 1 hp is lost with adding this exhaust... Now, lets even add a very high quality 200cpsi Milltek/HJS high flow catalytic converter to this same vehicle... Again, a loss of about 1hp and a gain of about 1tq compared to this car with only programming on it. Some tuners have suggested this is just due to programming not being optimized or that this situation isnt happening and if you removed the exhaust you would see losses in power. This isnt always the case though. There has to be another variable. Currently APR is taking advantage (and has been for a year) of adding fuel pressure. There are programs available running 125bar or so instead of the stock 110bar of fuel pressure. This has a benefit of running the car closer to its window of fuel spray. This is an advanced technique that many other companies are not taking advantage of. Still, it is not enough. APR has also developed a high pressure fuel pump that will come fully assembled and bench tested. I spoke with them over a year ago when they were considering different fueling options and an idea they had been testing was a retrofit for OEM pumps. They abandoned this idea due to research into the high pressure fuel pump tolerances and handling safeties. They will not allow a customer to take on the risk of modifying a part that sees 1600psi of pressure and if failed could cause major compoenent failure. So they have taken on the burden to have pump made from the OEM pumps and fully assembled in the appropriate clean room conditions and also bench testing each and every unit prior to shipment. Keep an eye out for these options... http://www.mjbmotorsport.com/fsifuel.html

[ChrisEVO]

This is the kind of technical info that I really appreciate. Not claims, but solid evidence of gain s or lack thereof.

I'm on the APR stage 1 flash and was wondering what kind of realistic gains I might find with an exhaust. Seems I've found my answer.

[OneEyedJack]

First of all thanks for the information!!

You mention APRs running the stock fuel pump up to 125bar and you also indicate that it is not enough. Are you saying they are still experiencing lean conditions when run at this pressure and boost levels within the operating range of the stock KO3? Or are you saying that you would prefer larger gains that are just not possible with the chip and higher operating pressure of the stock pump? I am assuming that this is where the larger high pressure fuel pump would become beneficial.

On another note, the lack of any gain on the exhaust side is (to me) not suprising. I doubt any additional time will allow the ecu to 'adapt' to an exhaust setup. I think your results demonstrate that the stock exhaust is capable of adequate flow even with tuner software. I am sure many will disagree but I have yet to see any proof a larger free flowing exhaust does anything but remove $1000 from a wallet. A larger exhaust defintely has its place, but to see any gains, in this case, requires a larger turbo.

[bhvrdr]

First, I just want to clarify that with APR programming the car will NOT run lean even if one experiences "fuel cut". You may have heard of individuals experiencing this phenomena and it is not a lean condition at all. On the contrary, APR has retained all fuel safeties so what people experience in this fuel cut condition is the ECU safely reducing power to PREVENT any such lean condition. SO the car will not run lean or dangerous in any manner. There is another company who has actually chosen to lean the car a bit but that is their philosophy and I havent seen a rash of blown motors from it so it may be ok.

But to answer the question about is 125bar enough, the answer is basically no that there is still room for more power but a higher capacity fuel pump is required. To this point the vehicles are NOT tuned to their max potential. Each and every tuner has taken some measure to tune around the fuel limitations. Some have leaned out the fuel, some have simply tapered power where necessary. This is likely why the exhaust gains on top of performance softrware are not seen. Remember that on the 1.8t motor it was common to see 10hp/10tq gains at the wheels on a quattro car just adding the catback Thermal exhaust. I'm not sure why this car could not benefit as much if not more. First, it is a turbo car and we all know turbo cars love large exhausts and second the OEM exhaust on the 2.0t is very similar to the 1.8t exhaust yet the 2.0t clearly has the potential for greater output. For now I agree with your assessment though that the best money spent for power related upgrades is likely on doing only software until fueling is addressed.

[dreese]

I'll second that. I'm new to the Audi, just getting a new A3. Lurking on a couple of other Audi forums, I was disappointed by the lack of "empirical" testing offered as I tried to research performance enhancements. I'm an old phart but had fun over the years doing some tweaks-where you got a bang for the buck.
As a previous hemi owner, we contributed cars and money to have various setups run on a dyno to see what really worked. Quick note--the stock 05 Dodge Magnum came engineered with an exhaust and paper air filter that couldn't be beat by any after market upgrade in that time frame. Thanks again!