2.7T fuel delivery capacity question (longish)
 

Started with APR 93 Octane program in 2.7T A6 6-speed. Fried turbos and elected to install K-04's for reliability. I plan to add exhaust, DP's etc... but for now, just the ECU/Bipipe and the K-04s.

After installing, I did a log of Block 2 (15 degrees (f), at sea level) just to be sure... and saw just over 300g/sec of air mass and a reported injector period that was longer than the time required for 2 revs of the engine (1 intake cycle) at high RPMs...

Here is data for a 1st-2nd run.

RPM/Load/Inj On Time/Air Mass/blank/calc duty cycle

720 21.1 3.4 8.69 2
1720 33.8 4.08 16.97 6
1920 75.2 8.84 46.53 14
2520 87.2 8.84 71.47 19
3320 118.8 12.24 128.61 34
4400 170.7 18.02 244.94 66
5760 180.5 27.2 303.06 131
6560 135.3 17.34 248.83 95
6040 9.8 1.36 2.92 7
4200 133.1 13.6 188.58 48
4600 191.7 27.54 265.19 106
5080 183.5 26.86 268.64 114
5560 174.4 25.16 283.28 117
6080 167.7 24.14 295.31 122
6400 157.9 22.78 291.42 121
6760 143.6 19.04 282.25 107
7000 106 11.22 206.83 65

Some of the duty cycle calcs are over 100. This means, I think, that the ECU is trying to keep the injectors open for longer than the time available and that I am running leaner than the ECU wants at high load/high rev. I guess this hints that I am past the linear operating range of my Software/fuel system.

Have anyone here logged Block 2 for this purpose?

Is there a guideline or spec of the upper limit (air mass g/sec, or HP) with which the stock EFI system can keep up?

I want this car to last, and lean running is a fast way to meltdown!

I'd appreciate any advice or comments!

Well if you put in K04's I sure hope you had a chip tuned for it
 

because your sucking in alot more air then the chip is tuned for. Even on a 1.8t they tune a chip for a 5 bar fpr to add more fuel which means they can also lower the injector pulse since the injectors will be 15% larger with the bigger FPR. You want to try to keep the injector pulse below 20's to keep it from running at 100%. You should see the #'s I pull on my 2 liter with the K04, I hit inj pulse of up to 35ms but my block 002 does not read out calc duty cycle.

Re: Well if you put in K04's I sure hope you had a chip tuned for it
 

I will be changing my chip ASAP. I figured that the MAF would keep up with the higher air flow, but did not fully appreciate the increased capacity of the K-04s until I ran the logs...

I have contacted O.CT and they are going to work up correct software for my car. They have assured me that the K-04's will be quite happy in this config with stock fuel system, but that to go any farther will require updated fuel pressure regulator etc... depending how far I want to go!

BTW Duty cycle was calculated using Excel. I divided the injector duration by the duration of 2 revolutions of the engine (one intake stroke per two revolutions), and got the figures I put in the table. (I think I got it right).

Thanks for your feedback. I will post results once I get the new software.

Fuel flow @ 100% duty cycle in the 2.7t is about 26 g/sec - so...
 

300 g/sec of air is still richer than 12:1 air/fuel ratio, so you're probably still safe. However you are approaching the limit, anything over 310-320 and I'd start to worry. You really need bigger injectors with K04s, especially once you get more aggressive tuning.

Yeah I think you did it right (more)
 

by the way, there are chipped S4s out there running 100% duty cycles even on stock K03
turbos. The better tuned K04 cars are flowing in excess of 340 g/sec air, so you'll definitely be wanting those bigger injectors along with software.

Thanks
 

I feel a bit safer at this point, and will be very careful plotting the future! Next steps will be DP's, Fuel Pressure/injectors, etc... with a goal of 360-375HP with a good strong and flat torque curve.

I have no doubt that the turbos are up to the task, and need to get the breathing in line.

To go further than 375 or so, I'll probably need RS-4 fuel and air systems, along with bigger IC's.
Not something I'll do casually!!!

Thanks again

I calculated 20.8 gm/sec at around 3.5bar fuel pressure, 100% duty cycle ;)
 

Why 3.5? Because at 0 boost no vacuum,(edit) it's FPR is rated at 4 bar. With high boost, fuel pressure will track the boost until things can't move inside the stock FPR anymore. That's a little under 5 bar. However, at 1.4bar boost for example, the effective pressure of the fuel with respect to the manifold is 4.9bar - 1.4 bar = 3.5bar, so that's how much fuel pressure is available to push into the pressurized manifold.

With 300gm/sec of air, that's about 14.4 : 1 ratio

but what do I know, I don't have an S4 so this is all just guestimates for our future big turbo project on the S4 ;P

News to me - I thought the FPR always maintained 4bar relative

No, 4 bar is relative to us. That's why it slightly goes up to around +1 bar from 0 vacuum...
 

but it will not track high boost, only the first 7 -9 (edit) psi of boost. A true rising rate FPR calibrated to the S4 is the only way to track it.

BTW disclaimer, all my numbers are from my actual measurements, so excuse me if it doesn't match advertised numbers somewhere :)

Log your O2 sensors and EGTs.....
 

Someone over on the S4 forum had put K04's on her car, and it was setting DTCs for EGT's too high.

K04s will have much cooler air coming out of them since they are more efficient.
Cooler air = Denser air = More fuel needed.