[s-cars] Fuel Pressure Test Results
CaptMagu at aol.com
CaptMagu at aol.com
Tue Jul 27 09:09:54 EDT 2004
Dave , Ned and all
I thought I would respond to Dave's off and online queries online for wider
dissimenation and of course flaming. First off, thanks for your findings Ned.
And thanks Dave for your energy in this matter. I know its probably fueled by
your desire for an answer to your problem but you are definately a driven man!
Here in the rarified air of Evahboost and Denver, most of us don't have
fuel/detonation issues. That changed for me when I ventured down to sea level with
the Happersized wundercar last year for the ACNA Nationals. First of all, I
couldn't run full boost on my old software because I was getting premature MAF
cut because of the denser air. I had to pull the boost back to 22 lbs. Even so,
when I had the car on the dyno to baseline my fuel pressure at sea level, I
noticed a disturbing trend in the air/fuel ratio and fuel pressure. After 6000
rpms the AFR would climb beyond 12.0 towards 13.0 and the fuel pressure would
drop from 88 psi down to about 80psi(I did and do have a fuel pressure gauge
under the hood). The dyno tech stated that many of the 1.8 liter Audis that he
had dynoed required a replumbing of their fuel lines to get to horsepower
levels beyond 350 hp. He said that my AFRs were very similar to the 1.8s and some
of the other cars he dynos. His suggestion was to replumb with larger lines
and get a high flow fuel pump. I never did get any detonation but I do closely
monitor boost, AFR, and EGT.
To review, when I got back to Evahboost, I had several discussions with Dave
Jones at ASW about how we might remedy this issue. His solution was to borrow
what they had done with their European Car Challenge 1.8 and S4 cars. We
incorporated a fuel reservoir under the hood that is fed by the stock pump, the 044
Bosch Motorsport high flow pump, and larger fuel lines from the reservoir to
the fuel rail. This approach does not require the very time consuming and
therefore expensive replumbing of all the fuel lines from the tank forward. At the
time of these mods I knew I was going with larger injectors, new
software(custom dyno tuned), to eventually feed a new turbo(GT 35R) with tubular exhaust
manifold.
These are my findings and solutions, now let's look at Dave's issues. First
of all, the stock fuel pump was never designed to handle RS2 power levels. That
said, your pumps are probably well within their design criteria. I think that
some of your recent voltage findings and thoughts might prove fruitful. I
would try this first. If it doesn't work, I'd go with the 044 pump. I'd also get
a wideband AFR gauge for monitoring and analysis.
Hap, talkin dahkine fuelflow in Evahboost, Maguire
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