1st time racing my dmax: 15.703 @ 86.

DAVe3283

Heavy & Slow
Sep 3, 2009
3,733
305
83
Boise, ID, USA
I got to do 5 passes at Firebird International Raceway today.
- 1243 ft elevation
- 8300 lbs "race weight" (I ran with everything I carry everyday)
- 45 psi in the rear tires, 65 in the front
- 2WD launches @ 1500 - 1700 RPM (didn't want to risk my front end)
- 3 engine limps :eek::confused:
- 2 new tunes written on the track :cool: I love EFILive!

My best time was a 15.703 @ 86.36 MPH (timeslip attached, video below). I was running against a buddy's 1997 Mitsubishi 3000GT (base engine).
[YOUTUBE]BVxYHhwLm14[/YOUTUBE]

The limps were caused by a "P0088 High Fuel Rail Pressure". For some reason it didn't like holding 179 MPa for 1/4 mile. I dropped the commanded pressure to 174 MPa, which did better, only limping once when I ran 2 consecutive passes without turning the truck off first. I guess I need that LBZ CP3, regulator, and pressure relief valve I have been wanting...

I also attached the log of my best run (you can see it limp at the tail end when the fuel cuts out but the throttle is still 100%). I didn't want to do many more because I think my transmission is starting to hate me, and I DON'T want to limp that!

So, any suggestions? I know I need a transmission, and it is next on my list. I probably could have run a TON more fuel, the tune I ran clouds out the sun back in Prescott, but was barely a haze at Firebird. Overall I was pleased for a completely homemade tune. In retrospect, I wish I had done a run stock to see how much my tune really helped.
 

Attachments

  • Timeslip.jpg
    Timeslip.jpg
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  • Quarter Mile - 15.703 @ 86.36.zip
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Sep 8, 2008
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I don't know what the limit is for the fuel pressure too high code but im sure you are hitting it. The lb7s and LLYs run a max pressure of 159mpa.

I don't think trying to go higher will help you any, flow does not increase much with a small change in pressure like that. Also, the fuel pressure relief valve might start opening at that pressure and the more it opens the eaiser it starts to open next time.

With my LLY with my stock trans I was running pw under 2000us. Anything over would limp in 5th, but at a lower rpm where more torque was being made.
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,733
305
83
Boise, ID, USA
If I have any more problems with the relief valve opening, I'll drop the pressure back to stock. As it is, I find that it makes the truck smoke a little less, but not really go any faster. I am all for reducing smoke when it doesn't make me slower!
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,733
305
83
Boise, ID, USA
I think that just limits the peak vs. fuel pressure, so they can reduce pressure if the fuel gets too hot. Mine is set to 180, but I still tripped the limit once (without going over 178). What is weird is I didn't see a drastic drop in rail pressure when it limped. The computer commanded a very low pressure, and eventually, the actual pressure dropped down to match. It didn't seem like a mechanical valve was opening...
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,733
305
83
Boise, ID, USA
I don't know what the limit is for the fuel pressure too high code but im sure you are hitting it. The lb7s and LLYs run a max pressure of 159mpa.
You are probably right about too much pressure for the stock components. I am going to turn down the desired pressure to stock until I upgrade/replace my CP3, etc.

I don't think trying to go higher will help you any, flow does not increase much with a small change in pressure like that. Also, the fuel pressure relief valve might start opening at that pressure and the more it opens the eaiser it starts to open next time.
For some reason what you said here didn't register last time I read it... and now that you mention it, it matches what I saw. The first time I was able to hold 179 MPa for most of the pass, then I was only able to hold 174 MPa for most of the pass. So, I am turning the pressure back to stock.
With my LLY with my stock trans I was running pw under 2000us. Anything over would limp in 5th, but at a lower rpm where more torque was being made.
I am still below 2000us, realistically, the tune I made is fairly mild. I might bump it up some, but I like how it runs now, so I don't see much of a need.

Thanks for the advice!
 

FMOS

Hard Up
Nov 19, 2008
352
0
0
Fort McMurray, Alberta, Canada
I'd look into shimming your FPRV. Or getting a PPE race "valve". It will eliminate the whole pressure relief issue. It might even happen at stock pressures now that it has popped once or twice.

Ya your right, after I looked at that table it doesn't make any sense for this application. (B1011).

Its probably just some tuning thats not jiving because of the increased FP.
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,733
305
83
Boise, ID, USA
I'd look into shimming your FPRV. Or getting a PPE race "valve". It will eliminate the whole pressure relief issue.
Sadly, those appear to only be for the LLY and newer. Mine is an LB7. Makes me wonder if this problem is somewhat rare on the LB7?
It might even happen at stock pressures now that it has popped once or twice.
I hope not! I ran back up from Phoenix today, and I am pretty sure it was up at 160 MPa (stock) for quite a while, and it didn't have any problems. Let's hope that it doesn't in the future... especially if no one makes a shim kit or replacement!
Ya your right, after I looked at that table it doesn't make any sense for this application. (B1011).

Its probably just some tuning thats not jiving because of the increased FP.
I left my B1011 with the limit of 180MPa, but I don't think it will matter since it will no longer command over 160. I don't think having yours at 200 will cause any problems either, unless your fuel got REALLY hot. As long as the higher temperatures restrict the max pressure, it should be fine.

Finally, how do I know if the relief valve physically opened, or if the computer just freaked out? Does it only throw the code when it opens? I attached a log of right where it limps, if it helps.
 

Attachments

  • P0088 Limp.zip
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