930 CIS WUR tuning woes.

[Yeahdoug]

Having trouble getting it rich enough near redline. The car has a slightly larger turbo (K27 7200) that was set at 1 bar. We installed an adjustable WUR and set it up close to the stock one for a baseline. The problem is we cannot get it any richer above 6000 RPM. It starts at 10.0:0 at low boost when the fuel enrichment kicks in. Runs 11.0:1 up to about 6kish when it quickly goes to 13.0. We've made a few boost enrichment adjustments on the WUR and it hasn't changed a thing. The control pressures all behaved correctly after the adjustments. With more boost enrichment the delta between warm and boost went up. Boost enrichment control pressure is under 15 psi which is 10 psi under where we started tuning it at. This 10 psi drop gave us no difference in AFR between the two boost enrichment pressures. Warm pressure is at 48 PSI, so we have a huge pressure drop for enrichment. The mixture adjustment only influences the midrange and lowend. Nothing we've done has helped get the peak AFR down. The boost was lowered to .9 bar and was still lean. The car dyno'd in the 340 whp range. Does it need the fuel head modified? Should we be looking at maybe a pump problem. I would have thought the stock system with an adjustable WUR would be OK for 340 whp. Seems like there is some fuel limitation that is none WUR related that we're up against.

[Yeahdoug]

Oh and thank you!

[T77911S]

perhaps some more info:
do youu have a header
is your system a lambda system or euro
any other mods done

how are the AFR's when driving normal

you dont need the FD modified for that HP. rebuilt maybe. (flowcontrol)
try this as a test. remove the vacuum line to the BOV/DV and see what it does. i had a synapse on my car and it was going lean as the RPM's went up. just curious to see if yours does it too, (is your intake system original)

your pressures are really out of whack. you should not have to run that low. 3.2bar CP is low for what ever system you have.

check for intake leaks. check the IC connections and intake bolts. also check your boost retard. make sure it works. if you have it connected, remove the idle vac retard, (but this depends on the year of the car which you did not tell us)

you can also check the fuel pump flow rate OUT of the FD. (the return to the tank).
while you are at it, check the flow rate to the WUR. i think that one is 225 ml for 1 minute (?)

[jbrown]

Sounds like you need fuel head modified. I went thru the same thing had my fuel head modified and was good to go. You can also fix that rich condition under start of boost. Going into the 10's you are giving up power. You should go with BL solinoid for the rich condition. It does wonders.
If you are interested I just went EFI and have a modified fuel head on the shelf. I will sell it at a good price... John

[RarlyL8]

Your warm pressure is too rich indicating an adjustment problem with the mixture, or WUR, or weak fuel pump. 340whp should not require either modified head or adjustable WUR if your WUR and FD are both fresh. If they are old you will have problems. I would check the pump output and system pressure first. If the system pressure is at the bottom of spec find out why, do not just shim the pressure regulator as that is a short term ban-aid.

[Yeahdoug]

Thanks for the replies and ideas. Car does have headers. Only O2 sensor is the AEM UEGO between the turbine outlet and muffler of the aftermarket exhaust. Everything seems to seal up nicely on the intake side when we take our time. It is pretty obvious when we have a leak at we lose some of our boost.

This is not my car. I'm just helping to tune it on the dyno. This is my first time with CIS as most of my experience is with McLaren, Bosch (EFI), and AEM EMS systems That said, I understand how it works and believe that there might be a fuel flow issue somewhere.

I know the control pressure is really low. The stock regulator was also at 45 PSI warm which is why we set it there since the car ran well on the stock turbo setup. Just for a baseline with the adjuatable wur. We ran the enrichment pressure drop slightly more than the stock WUR to account for the extra boost with the new turbo. Then when it was still lean we kept adding more and more boost enrichment to no effect. I'm also aware that 10.0 is way rich and we are for sure giving up lots of power. My goal was to get it safe under WOT first and work from there since it is all a balancing act, but nothing we did added fuel up top.

We'll have to dig into the other parts of the fuel system. We will try the flow test and see if it meets the stock specs. We should also make sure the fuel system pressure is within spec.

I've read/heard a lot of mixed things about needing fuel head modifications at this power level. Some say yes, some no. Seems like there are big differences between cars.

[RarlyL8]

What are the Bosch part numbers on the WUR and FD?

[T77911S]

what BOV or diverter valve are you running.


BRIAN,
could it be something with the throttle switch?
when it goes WOT does the computer drop the frequency of the FV even more to richen it up?

[patina]

Originally Posted by T77911S

what BOV or diverter valve are you running.


BRIAN,
could it be something with the throttle switch?
when it goes WOT does the computer drop the frequency of the FV even more to richen it up?

The engine is an '86 and it is the factory diverter valve.

[RarlyL8]

'86 with OEM fuel distributor and WUR with Lambda disabled?
I'd still check the fuel pumps first. You have to verify the system pressure and flow rate are in spec before moving forward.

[Alan L]

I just did a dyno and tuning run on mine (380rwhp at 0.8 bar.). I got mine excessively rich at the top end by tweeking the WUR about 3/4turn soft. Then had to dial it back from there. You should have plenty of fuel available. Something else restricting the flow. (There is a screen in the WUR feed as well).
Alan

[oilonly]

Yes that is one fine screen leading into that tiny valve. My friend who had a low mileage 930 was having problems with his car even had his pumps changed for no reason. Problem was clogging screen in the WUR.