turbo and WOT injector
Gary.Kaklikian at compaq.com
Sat Aug 26 11:28:17 EDT 2000
I thought it was time I enter this discussion. First, the disclaimers:
I am definitely not an expert on the 10vt
Most of the work on my car was done by an experienced Audi tuner
And, yes, I've spent more money on this damn car than I ever imagined
But, after a year of f@#$ around with turbos, exhaust, fuel, etc - an
exasperating, costly exercise -- I think we finally got the car right. I
guess I was naive in thinking the 4000 turbo conversion would be simple, but
really, we pushed the envelope on this motor and consequently all the
If any of this is of any value to anyone, great; if not, then just delete
it, but please don't revert to name calling.
First my conclusions:
The K24 is useless if you want any kind of mid-range and top-end performance
You will run out of fuel with the CIS if you increase airflow and/or boost
A bypass valve setup and electronic boost controller are invaluable.
MC-2 with ported/polished head, Piper cam, K26 modified with 944T compressor
wheel, 2-piece EM, Scorpion downpipe, very open custom exhaust, 944T
intercooler, plunger-type bypass valve, large oil cooler, Profec B boost
controller, W5DPO plugs, custom programmed ECU, wg spring, etc
With this setup, the stock CIS will run out of fuel at ~8 psi boost. I can
see this with scary high EGT's, lean on the A/F gauge, hesitation, vapor
This is with the stock MC-2 CIS, but using the older-style internal,
plunger-type fuel pressure regulator. Shimming the fuel pressure regulator
helps a little.
Using Mercedes V8 injectors or running a vacuum line to the CPR did not
Two Motronic injectors (3B motor) mounted in a pipe between the intercooler
and throttle body and controlled by an ERL MF2 injector driver
(http://www.aquamist.co.uk). I have the MF2 set to start pulsing the
injectors ~8psig, and it has individual pots for fuel in 1000-rpm
increments. My car builds boost very quickly but the additional fuel is not
required until 4000-7000rpm, the most at 5000-6000. A second fuel pump (930
turbo) was added after the UrQ pump.
I now run up to 17psi boost and have plenty of fuel. Granted I don't have a
precise way to tune the MF2, but I've found that the car runs best with A/F
mixture well into the rich zone under WOT/full boost.
On a lower compression motor or in cooler temps, lower altitude (I'm at
5000ft+), I'm sure you could run more boost.
The MF2 works. I don't know whether or not I am getting ideal fuel
all cylinders. Sampling of the spark plugs has not revealed any problem, but
I'm really reluctant to shut the motor down abruptly at WOT at full boost.
It would be nice to able to tune the car on a dyno, as well as to have an
ECU with user-adjustable ignition curves. .
I know the CIS would keep up fine with a stock MC-2 with a stock K26 to
probably 14psi boost. But if you increase the airflow of the motor
substantially, fuel WILL be a problem. I would estimate the CIS could give
you maybe 220hp, whereas I'm probably getting 280 or so. The nice thing I
like about using an auxiliary fuel system is that it allows you to retain
the smooth idle, part-throttle operation, and fuel economy (relatively
speaking) of the CIS, plus, if it fails you can "limp" home on low boost.
My car will redline very quickly in the first three gears, less quickly in
4th and 5th, yet has enough torque to pull from 2000rpm in 4th. Turbo lag is
non-existent above 3500rpm and boost actually starts to build at about
2700rpm. Throttle response, torque, and power delivery led a co-worker who
is a Mustang guy to remark that it feels like a prep'd V8.
Brandon Grantham at Rimmer Superchargers in Colorado Springs is an ERL
distributor and has successfully installed the MF2 on many of his
Another plug -- Amsoil 20W/50 Racing oil actually lowered my oil temps and
made the motor run noticably smoother.
86 92 S4
> From: Buchholz, Steven[SMTP:Steven.Buchholz at kla-tencor.com]
> Sent: Friday, August 25, 2000 1:07 PM
> To: 'qlist'
> Subject: RE: turbo and WOT injector
> ... it seems to me that this is precisely what we are trying to do ...
> assuming that the rear cylinders are running lean as compared to those in
> front ... remember that we are augmenting the fuel provided by the CIS ...
> this isn't a lot of extra fuel, just enough to richen up the engine when
> running under high boost ... and providing a bit more to the rearmost
> cylinders than the front ones ...
> Steve Buchholz
> San Jose, CA (USA)
> > Isn't the problem reversed with the single injector? Fuel is heavier
> > air and that would tend to make it richer in the rear cyl's if the fuel
> > in the airstream at/near the TB.
> Quattro mailing list Quattro at audifans.com
> To remove yourself, change to digest mode, or temporarily stop delivery
> please visit the web interface at
More information about the quattro