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Lost power at 7700 rpm on dyno

1948 Views 15 Replies 10 Participants Last post by  holmz
Just come back from the dyno, i got a boe supercharged work's fine 2 year ago i pulled 349whp and now 330whp but the power and torque go down at 7700 rpm.
I try stock and stage2 cam from mwr and alway same thing.
Did somebody have same problem or can help
me ??
The plug are gap to 20. My computer is not stock ,i don't remember the name it's a blue box v-2 ( i think ).

Thank's for your help !
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Same dyno?

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Yes same dyno !!
Same head,spring,valve ....
We try the same programation and it's the same !!
Fuel starvation?
I blame that on bad gas / high rpm knock pulling tming. If you have some E85 in your area, put 10% in your tank and see if that changes things.
Why would u put in e85? That would make him run leaner. We don't know what his a/f ratio is. Putting in a little racing fuel or 100LL avgas might help if it is pulling timing due to knock. If he is already got a weak fuel pump or maxed out injectors, i think e85 could help make a hole in a piston.

Show us a chart of a/f ratio
Yes same dyno !!
Same head,spring,valve ....
Same head, spring, valve with how many more miles on them?
Air filter ok? Bost drop? Fuel flow and filter? The drop of a few hp over two years may not be that much of an issue but the drop in the graph would be to me. Adding hp to cars does make parts wear faster...
I got 94 octane gaz mixed with 114 octane gaz in it, so the knock is not the problem, i don't see lost of pressure on the gauge,my head is like brand new,is it possible the valve spring coming soft ??
When i put the mwr stage 2 cam i got a lot of black smoke untill the wideband said 12.2 to 11.8 at full trottle.
With the stock cam i got less black smoke but alway's smoking at full trottle.
My catch can are ok.
My surge tank is ok.
Cam look's good.
The plug are gapped to 20.
We try with no air filter and no exhaust and the same curve !!
So when you changed cams, I'm assuming you re-shimmed and reset the lash.
Then did you retune your ECU to move the VVL changeover rpm and retune your ECU to change the VVT map (intake cam timing)?

Without doing both of these, the car will not run correctly.

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LJ60 is right about we need to see air/fuel and knock count if possible. That violent of a dip looks like a safeguard is tripping.
It sounds like you'r running an EFI standalone EMS (the blue box).

Given that it's an EFI.

1) You're running 100% closed loop. you're not giving us 02 info. Have you checked this (AFR)? If the WB02 is not in good shape, then the EFI will enrich or lean the mixture all the way to redline with bad data from the wideband. It's critical that the WB be replaced every year or so. It could just be that the EFI is dumping fuel or pulling fuel from the motor due to poor WB inputs.

2) It may be misfiring. Depending on when the EFI was built and what model it is, it may need a crank trigger update.

3) It's not knock. The EFI doesn't use knock input.

4) Since you have EFI, you can hook the EFI up to a windows laptop and actually fetch nearly all engine data. Dyno plots without data is of no help in helping us help you.... There are videos on my website in the techwiki that go over some of the EFI features in addition to the software required.

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Thank's i try to find the dyno sheet with the air fuel and i post it here
Thank's i try to find the dyno sheet with the air fuel and i post it here
The other item that is usually pertinent is the spark advance.
So AFR and spark advance.
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