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Road Racing FD losses power

Old 09-12-04, 09:06 AM
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Road Racing FD losses power

Before messing up my current tune I would like to hear some opinions on how to proceed to fix the following:

Setup: 93 FD, GT3540, street port, all cooling mods (dual 25rowOC, ducted rad, etc), 100 octane leaded blend (93UL&110L), Power FC and datalogit, about 400whp, NGK racing 11.0, HKS twin power.

During a 15min heat all tempertures are always kept OK (water 100C max and air about 80C max at end of heat). Therfore, overheating is not a/the problem.

Now here's the issue:

During the first 8 minutes (about 9.5 track miles) the car runs perfectly with plenty of power and consistent within the rev range 3500 to 7500.

After that (as tempertures start to reach above mentioned max) the car develops hesitation from 3500 to about 5000 then it produces good power again up to 7500. As you go on it may affect the 5000 to 7500 range also.

Has someone been able to fix this with datalogit air temp / water temp vs. INJ and IGN so as not to affect the current maps.

Any recommendations on how to proceed with the Power FC or any other reason I may not be considering?

Thanks
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Old 09-12-04, 09:30 AM
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Question

What IC are you using (didn't see it in your list if I missed it)?
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Old 09-12-04, 09:39 AM
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Sorry to miss that...

It is the large racing stock mounted intercooler with duct (M2, Pettit, Peter Farrell).

Battery relocated to behind passenger bin.

Thanks for your interest...
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Old 09-12-04, 11:54 AM
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Sounds like something is heatsoaking after a few laps and dropping off your performance.

I've ridden in cars using the larger SMIC's (M2/ASP's) , I'm using the Pettit Coolcharge II, and never noticed them losing power through their sessions, however they are using the stock twins rather than a single. I've heard of the some of the smaller SMIC's heaksoaking towards the end of sessions causing some lose in power.

You said your air temps seem ok, so maybe it's ignition coil related?
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Old 09-12-04, 12:54 PM
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Mahjik, after a 15min aggressive high boost session what air temps do you see, just for comparison.

As is mentioned, I see about 80-83C running in about 92F ambient summer climate. I feel this is about right. Cooler will be better but difficult in my weather, high boost, and hot track conditions.

What do you mean regarding the ignition, fails after hot?

Would it be possible that just becomes too rich after hot? Unfortunately I don't have a wideband installed ....dumb right.
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Old 09-12-04, 06:12 PM
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Originally Posted by gustavofd3s
Mahjik, after a 15min aggressive high boost session what air temps do you see, just for comparison.
Unfortunately I can't tell ya as I'm not using a programmable ECU with a monitor (using a Pettit rechipped stock ECU).

Originally Posted by gustavofd3s
What do you mean regarding the ignition, fails after hot?
Well, maybe not fail, but not work as effiecently as cooler. Have you tried disconnecting the HKS and see if that makes a difference on the track?

Originally Posted by gustavofd3s
Would it be possible that just becomes too rich after hot? Unfortunately I don't have a wideband installed ....dumb right.
I suppose if a thermosensor wasn't reading correctly once too hot, the PFC could go into a limp type mode. I would assume that it would be much more noticeable effect if that were the case.
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Old 09-12-04, 10:28 PM
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Originally Posted by gustavofd3s
Before messing up my current tune I would like to hear some opinions on how to proceed to fix the following:

Setup: 93 FD, GT3540, street port, all cooling mods (dual 25rowOC, ducted rad, etc), 100 octane leaded blend (93UL&110L), Power FC and datalogit, about 400whp, NGK racing 11.0, HKS twin power.

During a 15min heat all tempertures are always kept OK (water 100C max and air about 80C max at end of heat). Therfore, overheating is not a/the problem.

Now here's the issue:

During the first 8 minutes (about 9.5 track miles) the car runs perfectly with plenty of power and consistent within the rev range 3500 to 7500.

After that (as tempertures start to reach above mentioned max) the car develops hesitation from 3500 to about 5000 then it produces good power again up to 7500. As you go on it may affect the 5000 to 7500 range also.

Has someone been able to fix this with datalogit air temp / water temp vs. INJ and IGN so as not to affect the current maps.

Any recommendations on how to proceed with the Power FC or any other reason I may not be considering?

Thanks
Is your fuel pressure ok? The pump may dieing.
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Old 09-13-04, 08:34 AM
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Timing is retarding

The PFC retards timing when both water temps air temps reach specific temps. I had Chris Carlisi who owns a data logic delete the timng retard function. Also your air temps are 80C? If you are reading that number from the PFC Com. you are to hot........
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Old 09-13-04, 10:05 AM
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Your air temps are very, very hot. Even in 103F weather, I was topping out at low 70s C air temps, with a much smaller IC.

As others mentioned, the PFC retards timing when the air gets too hot. However, it sounds like you have more of an issue than that. Are your boost levels consistent when the power issues occur?
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Old 09-13-04, 10:55 AM
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I run a M2 Meduim SMIC and temps usually top out at 60-65, even after 40 min on the track in 80F heat. With water injection I expect them to be in the 40's. We will see.
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Old 09-14-04, 09:00 PM
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It seems that intercooler heatsoaking is mostly my problem. Based on your info 80C is higher than I thought was expected for hot climate and high boost at the track.
Power is plenty up to the hesitation. Boost remains consistent at 18-20psi.
I will try to get more fresh air (somehow) into both the intercooler Large race stock mount and the air filter by removing signal lamps, headlamps, etc. and try it out to compare.
Also I will try to adjust for a leaner condition above 70C to 80C to see how the motor handles.
Let me know about any other things that may help out to operate at 70 to 80C if any.
Thanks
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Old 09-15-04, 04:16 PM
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18-20 psi? ouch... try turning it down a bit for the track?
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Old 09-16-04, 12:22 PM
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Originally Posted by John Magnuson
18-20 psi? ouch... try turning it down a bit for the track?
Yes, running that boost with those temps AND leaning the motor out is asking for a rebuild. I run 12lbs on the track and can usually keep up or beat any car out there.
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