RAD951

I am having problems with my car at high rpms or at full boost. Here is the deal, whe I am fully boosting to 15 psi, the air/fuel ratio goes to lean around 15 psi only if I keep it on full throttle. This happens mostly on the highway when I fully press the gas pedal and the boost starts to kick in, the air/fuel moniter decreases to lean linearly during the time being at 15 psi. I am running autothority stage 2 chips, cone filter, tesxtpipe, shimmed wastegate 5 mmm, port and polished head. What could be the deal with this? Is the the autometer air/fuel monitor or the regulator?

Toolmaster

RAD -

Is we make the assumption that your chips were burned specifically for your modifications, then you may have a fuel pressure regulator or damper problem.

What's the pressure at the fuel rail? Many people with your modificaitons have also invested in adjustable fuel pressure regs, with great success.

HTH!

Alan C.

I doubt that the Autometer gauge is that accurate. My last dyno run indicated 13.5 onboard while the horeba on the dyno showed 12.2.

The autometer probably isn't bad for a historical ref. point but I wouldn't trust it past that point.

Alan

RAD951

The stage 2 chips are for a stock 951. I added everything else afterwards. The chips weren't specially burned for me. I think I may need a fuel pressure regulator. Do you think I need that "rising rate" AFPR, or a 3 bar FPR?

The autometer is not pin point accurate, but its an estimate. However, it shouldn't go down to lean the way it does when I am hitting full boost. I can see clearly I have a fuel problem, or my O2 sensor is bad.

The chips run a little into the rich side when accelerating, just how autothority said it would, however, it goes to lean as the seconds pass when I am at 15 psi.

Its like I am not holding fuel pressure after being at 15 psi a couple of seconds. Also, after it goes to lean at 15 psi, my gauge stays at lean for a minute even if I am just cruising. I think the problem is that the regulator works fine even at acceleration, until at full boost were I need a steady fuel feed. I think it gives out when the demand for fuel is needed most and then it takes a while for the fuel pressure to get back to normal. Thats why it takes a minute for the air/fuel ratio to get back to normal.


I really don't want damage the engine running lean at high rpms. I guess I can dyno the car and check out the air/fuel ratios just to be on the safe side and to see if the air/fuel monitor is working properly. While I am there, I guess I will check how much Hp I am making.

Any more suggestions?

Russ Murphy

[quote] the air/fuel moniter decreases to lean linearly during the time being at 15 psi. <hr></blockquote>
I'm assuming that you're accelerating constantly and the rpms are increasing all the time you're at full boost and the a/f ratio is falling. If you can supply enough fuel at 3000rpm's and 15 psi but not at 5000 then maybe you're at the limits of your fuel delivery system as opposed to weird fpr functioning. Try a $36.00 3.0 bar fpr first.

RAD951

Where or who do I need to speak to to find those $36 3 bar fuel regulators?
Appreciate it.

Danno

"The chips run a little into the rich side when accelerating, just how autothority said it would, however, it goes to lean as the seconds pass when I am at 15 psi."

My question is similar to Russ's. During these 'seconds passing' is your RPMs increasing? If it goes lean as your RPMs increase, then injector duty-cycle may be maxing out. If it goes lean as the RPMs stay constant at full-load (like top-speed run), then you may have some other problems.

Paragon Products carries the 3-bar FPR. Also you might want to turn down your ignition timing -3 degrees using the FQS in the DME.

RAD951

Danno, yes it goes lean as the rpms stay constant, only at going 100+ mph. Its sounds like the fuel supply at that time decreases or doesn't meet the requirements of a steady flow of fuel. I think its that regulator, I will try the 3 bar regulator first.

Also, why do I need to turn back the timing -3 degrees and how do I do it clockwise or conterclock wise. Where is the screw located on the dme? And wich way do you turn to advance timing and retard?

Danno

Hmmm at 100mph, you're far from full-throttle so the DME should be dithering your fuel mixture? If anything, it should show a sweeping back-and-forth motion...

superjet.1

very simular resuts from my 951 i added and adjustable fpr and it did the trick but im still maxing out the injectors.so im investing in larger injectors.