I had my C5/LS1 tuned a few weeks back. Greatly improved it. The tuner told me that it was missing at certain points, etc. which was expected.

At 5500 rpm the TQ and HP basically fall off the chart and the engine shakes wildy.

For the most part I stay away from 5500:woowoo: but it makes me question the cause.

I'm thinking fuel starvation (fuel pressure too low, can't push enough fuel into all cyls, so half are not firing).

My thought is that if I find the cause I might actually extend the powerband.

Thoughts? Opinions?

:patriot:

whole bunch of possibilities - if the tuner can't tell you why and left it that way - first thing to replace is the tuner.

whole bunch of possibilities - if the tuner can't tell you why and left it that way - first thing to replace is the tuner.

Hmmm....

It's a reputable shop.

Get a fuel pressure gauge on it even if it's a simple mechanical one and you have to tape it to the windshield.

Go for a drive @ WOT. Make sure the fuel pressure doesn't drop below 55 PSI at any time - bring a co-pilot to help if necessary. If it does it's either the pump or the filter both of which are in the tank.

If not, check the plugs they should be gapped around .045" naturally aspirated and .028" - .034" for a blower/turbo. Tighter for higher boost.

OR an even better idea, bring it by our shop and we'll diagnose/fix it for you.:thumbsup3:

Get a fuel pressure gauge on it even if it's a simple mechanical one and you have to tape it to the windshield.

Go for a drive @ WOT. Make sure the fuel pressure doesn't drop below 55 PSI at any time - bring a co-pilot to help if necessary. If it does it's either the pump or the filter both of which are in the tank.

If not, check the plugs they should be gapped around .045" naturally aspirated and .028" - .034" for a blower/turbo. Tighter for higher boost.

OR an even better idea, bring it by our shop and we'll diagnose/fix it for you.:thumbsup3:

Thanks - I'll see about a pressure guage. Any recommendations?

I'm really afraid to bring my car to your shop. I'm fairly sure it'll cost me way too much - with the new heads/cam/intake, etc. I'll just have to have once I get there. :happy0045:

:patriot:

Thanks - I'll see about a pressure guage. Any recommendations?

I'm really afraid to bring my car to your shop. I'm fairly sure it'll cost me way too much - with the new heads/cam/intake, etc. I'll just have to have once I get there. :happy0045:

:patriot:

Well we have about 5 engine builds going on right now. We can add yours to the list too... :D :D :D

As to a guage: If you want to get by inexpensively, stop by Harbor Freight they have a fuel pressure gauge set for around $10-20. It's certainly accurate enough for a quick check. Or AutoZone and the like will lend/rent tools. :thumbsup3: