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Discussion Starter · #1 ·
I am running out of suggestions to fix a problem I have been having with my vehicle.

Here are the ignition/other important specs:

MSD6AL ignition
HVC coil
MSD 8.5mm plug wires
NGK 8 Vpower plugs &/or NGKR ZFR7F11 plugs - gap adjusted between 27 & 32
Hondata 4B using p75ecu
720cc/min RC injectors
AEM fuel rail/ FPR - base pressure @ ~45
Inline & intank Holley fuel pumps
Full tank of C-16 VP racing fuel

Here is the problem:
The vehicle patters, or flutters past ~5500 rpm. This occurs under non-boosted, and boosted condition. Under boosted conditions, the maximum boost reached is ~1.17 kg/cm2 (even when the boost controller is set anywhere between 1.35-1.75 kg/cm2).

This first occured on the dyno. The vehicle was working fine @ ~ 1.65kg/cm2 and made 486whp (on a mustang dyno). The next run was @ 1.7 kg/cm2, where the vehicle ran smooth and made 491whp. After that, the only change that was made was ~2% fuel added after 7000rpm. The next run, the fluttering occurred, and no increase in power was seen after 5500rpm (ie. max power occurred @ 5400rpm - 355whp, power curve was flat after that point). Also lambda readings were around 11.8-12.2:1 for the duration of the run. No ignition timing changes were made from the good run to the poor run.

To try to fix the problem, the following things were tryed:

-plug gap was changed from 32 to 27
-NGK 8 Vpower plugs were replaced with new NGKR 7F11 plugs
-another set of MSD plug wires were tryed
-Blaster3 coil was tryed instead of HVC coil
-6AL was replaced with Mallory Digital ignition
-p75 rom was replaced with a p28 rom using a non-vtec map
-distributor was swapped with a distributor from a different functional vehicle
-O2 sensor was replaced with a different O2 sensor

If you have any suggestions about the problem, I would like to hear them.
For more info on my setup visit:

Thanks in advance,

H23A turbo prelude
491whp & 401ft-lbs on mustang dyno
traction limited run = 12.3 @ 118mph with terrible 2.2sec 60ft time
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