Hmm, my point was that the Dyno is a good tool for measuring the engine's response to a modification. The fact that it only registered a 15hp gain indicates a problem, the Dyno is doing it's intended job.

weigh the bottles.

 

I weighed the bottles at Allen's shop. The full one had 9.5#'s and the one that didn't get filled all the way weighed 6#. We ran dyno runs on both bottles. Didn't seem to make much difference. I know the weight was there, I'm just not sure of the pressure + it was cold.

 

??How big are your bottles??

 

They hold 10# when full.

 

my 10lb bottle weighs 15lbs empty. ~25lbs full.

 

I doubt the exhaughst is the problem. My guess is ignition, bottle pressure, or valvesprings. I would start with the plug gap, and check the wires first. That is cheep and easy.

 

Valve springs are brand new comp cams 918's or whatever the latest and greatest replacement for the 918's happened to be. Wires are stockers with 9000 miles on them. I'm taking the bottles back to the guy that filled them in the morning. I think he has a way of checking pressures. I'd sure like to find out that low pressure was the culprit. Easy fix. I'm going to get Allen to send my stock plugs back to me unless he's already trashed them. I'll at least check the plug gaps.

 

Even though we installed new springs, I've seen springs limit hp

 

I had time to check a few things on my truck today. I tapped the exhaust just behind the X pipe and just ahead of the mufflers. I found 4psi of exhaust back pressure at 5500 rpm and WOT. Boost pressure was about 7.5psi.

Also tapped the intake tube between the throttle body and the MAF. Found 3 inches of vacuum there at WOT, 5500rpm, and 7.5psi boost.

Which one is worse? Exhaust back pressure or intake restriction? Leaning toward taking care of the exhaust first by adding some cutouts and then corsa mufflers when they become available. What can be done about the MAF?

 

Let's sd tune it and take that maf out.