Power loss problem...dyno results included...need input.

[I30tMikeD]

I would like some input on what some of you technical savy Infiniti owners think about my top end power loss problem.

I got a dyno done last week and the results showed a major problem with high rpm torque loss.

I imagine most of you are not really familiar with I30/Maxima mods but I have a variable intake manifold along with the JWT ECU with a 7200 rev limiter. The VI makes it possible to hold power all the way to redline. Everything on my dyno looks normal till 4.5K rpms when my torque drops like a rock.

The link below is a dyno of two different maximas with the basically the same mods as myself. The first one is a VI along with the extened redline and the second is a VI w/o the extended redline. These are just to show how my power curve "should" look.

http://69.193.109.74/car/jwtecudyno.jpg

http://memimage.cardomain.net/...l.jpg

Here is my dyno. The first run my butterfly valves for the VI did not open. I am having issues with my rpm switch not opening the VI. The second run is with the butterfly valves zip tied open. So basically the first run is how things should look up to 5k rpm's or so and the seond run is how things look after 5K rpms or so. The fact that the VI did not open is a mute point to my problem.

http://memimage.cardomain.net/...l.jpg

I am losing 25 whp from 6K rpm's to redline where as I should be loosing about 4-5 whp. Something is going very wrong at 5K rpm's.

This is a new/used motor I put in about a month ago. I don't think it's a engine problem since I able to make about the right amount of peak torque, and if I had a couple bad cylinders that would not be happening.

Things I have checked so far and that are fine are vacuum, plugs, fuel filter, coil packs, air filter, knock sensor, and exhaust leaks.

1996 I30t 5spd

IntakeCattman equal length headersVIJWT/ECUFidanza flywheel

Any insight would be much appreciated

Mike

[I30tMikeD]

oh, and my guess is either a clogged/broken cat or for some reason I am getting massive timing pull.

[texasoil]

possibility/suspicion? whatever is keeping VI from operating is also keeping ignition timing from advancing all the way.

[I30tMikeD]

The VI is just ran off vacuum....but your on to something I figured out earlier today.

It might be hard to know what I am talking about if you have never seen how us maxima guys get these nonstock VI's to work. We tap off a vacuum hose and use a vacuum canister with a built in check valve. A rpm switch is used to power a solenoid that releases the vacuum to pull the butterfly valves open.

Without a working check valve, I basically have a path for my vacuum source to pull air from the atmosphere. But this will only happen when I hit 5.4K rpm's because that is where my rpm swith is set to.

So, everything is fine until I hit about 5.4K rpms and my rpms switch activates then all of the sudden I have a vacuum leak. Unmeterd air is entering the manifold, and since I am taping my vacuum off the FPR hose it will mess with my fuel pressure. I think that is what is causing my power loss.