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Old 05-07-2004, 20:41   #1 (permalink)
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Flat Spot at 4000rpm

Had the 'fox' on the dyno yesterday for the first time and picked up a flat spot which starts at 4000rpm and ends at 4500rpm, the torque and power curves show this funny loop (identical on both curves). Three runs on the dyno and exactly the same little loop.

Any of you guys had this and is there a fix???

Cheers,
Al
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Old 05-08-2004, 04:15   #2 (permalink)
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Re: Flat Spot at 4000rpm

Quote:
Originally Posted by Redhawk
Had the 'fox' on the dyno yesterday for the first time and picked up a flat spot which starts at 4000rpm and ends at 4500rpm, the torque and power curves show this funny loop (identical on both curves). Three runs on the dyno and exactly the same little loop.

Any of you guys had this and is there a fix???

Cheers,
Al
ave you been losing sleep Al? Mr Batten and/or GTP-330 are probably the best to seek advice from mate
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Old 05-08-2004, 21:24   #3 (permalink)
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Re: Flat Spot at 4000rpm

Quote:
Originally Posted by Redhawk
Had the 'fox' on the dyno yesterday for the first time and picked up a flat spot which starts at 4000rpm and ends at 4500rpm, the torque and power curves show this funny loop (identical on both curves). Three runs on the dyno and exactly the same little loop.

Any of you guys had this and is there a fix???

Cheers,
Al
I would need to see the dyno sheet to make a comment but im guessing as apposed to an actual flat spot its more than likely a point of either the manifold or the pipes or even cams going on or off tune...On the GT for example theres a spot on the dyno graph where its point of climbing tapers of a little then starts to climb again. Changing headers on a GT will actually make this LUL as i like to call it lift up a bit in KWs but it in itself will remain in the same position.(same rev range)...
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Old 05-08-2004, 23:24   #4 (permalink)
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Re: Flat Spot at 4000rpm

Quote:
Originally Posted by Redhawk
Had the 'fox' on the dyno yesterday for the first time and picked up a flat spot which starts at 4000rpm and ends at 4500rpm, the torque and power curves show this funny loop (identical on both curves). Three runs on the dyno and exactly the same little loop.

Any of you guys had this and is there a fix???

Cheers,
Al
Mate it could be knock sensor operation, the computer may be retarding ignition timing around the peak torque area. Try some good octane booster if this improves the power dip in the dyno graph, then you can be sure that the original dip in the power graph was ignition timing related. Worth a try for your own peace of mind.

Peter

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Old 05-09-2004, 11:25   #5 (permalink)
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Re: Flat Spot at 4000rpm

Looks like a roller coaster ride....

Did those guys use the dyno correctly, I havn't seen anything like that before.
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Old 05-09-2004, 13:23   #6 (permalink)
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Re: Flat Spot at 4000rpm

Haven't seen the dyno, but sounds very much like a case of valve bounce.

Regards.
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Old 05-09-2004, 16:04   #7 (permalink)
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Re: Flat Spot at 4000rpm

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Originally Posted by GT-P
Looks like a roller coaster ride....

Did those guys use the dyno correctly, I havn't seen anything like that before.
Now I'm worried!

From what I saw Barry, yes he had set the dyno up correctly.

Will ring you later today.

Al
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Old 05-10-2004, 03:06   #8 (permalink)
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Re: Flat Spot at 4000rpm

When mine was dynoed, its curve is one nice long gradual increase, mine seems to be strong at the 4k mark. Id be looking into it, as Peter said, look at the fuel and boost it if you think its down.
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Old 05-10-2004, 03:24   #9 (permalink)
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Re: Flat Spot at 4000rpm

Thanks for the posts guys,

I personally reckon the dyno is the fault, cannot feel any flat spot when driving the car, she powers through 4000 - 4500 range in 1st, 2nd & 3rd (have'nt taken her on the highway to check 4th.........yet!).

Getting her checked at D & T Performance on Wed, will let you know the results!
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Old 05-10-2004, 05:14   #10 (permalink)
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Re: Flat Spot at 4000rpm

Quote:
Originally Posted by HSV
Haven't seen the dyno, but sounds very much like a case of valve bounce.

Regards.
lol @ 4000rpm???? dont think so dude....nah its going to be a case of dyno me thinks.. Its ok its booked in to D&T for a run on wed i believe .. Ill meet you there and have a chat
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