First some background. 2000 TA built 348 9:1 comp. Cartek 243 4xxb heads Cartek blower cam Procharger D1SC, RPM stage 6 4l60, Twin255 walbro pumps. 2bar MAP Speed Den. tune, NGk TR6 gapped to .036 ,

Last week i took it to have it dyno tuned. Made 600 hp with 14.5 psi pump gas AFRs were 11.5 11.7. 15* of timing. The plan was to max it out on pump gas then drain the tank and retune for e85. Well i was told i didn't have enough injector for e85. I was running 84# at 77%DC.

Now the problem ! I swapped out the injectors for 120#an i also swaped out a 3.85 pully for a 3.40 in order to make more boost. Now making 16+ psi

so back on the dyno Pump gas in the tank we start making some hits, baby steps up in boost and rpm once we hit the 14.7 psi mark the power drops boost went up to as high as 16.5 mph went up but power fell. Never even made it back to 600hp. I think 550 was peak hp at 5100 rpm @ 14.7 psi.

Now the guy tuning the car cant figure it out he says everything looks good. Afrs were steady at 11.4 timing was 15* AIT was under 125* Supercharger belt wasnt slipping boost was rising smoothly.

He tells me it might be valves floating. Now im not sure what springs are in Carteck stage 3 heads but imagine they be good enough to make more than 16psi.

The car shop tuning the car uses hp tuners speed density tune. Im thinking something was wrong with a setting or maybe a map sensor thing.

You can see from the dyno graft the power climbed smooth until 14.7 psi then it dropped off quickly. The old combination never made it to 14.7 but it made 600 at 14.5 psi @ 6300. I never made it to 6300 with the smaller pully it hit 14.7 at 5100rpm then nose dived.

Any thoughts ???i Valve springs not good enough ??? or tune error?? or what??

 

6 speed trans?

 

stage 6 rpm 4l60e

 

"hit the 14.7 psi mark "...That's the end of the resolution of a 2 bar MAP sensor. [I didn't see what sensor you are using.]

 

Could easily be valve float. How old are the springs?

 

Springs are at least 7 years old heads were installed in 2005 car has sat mostly since then . They might have 500 miles on them. I know cartek used comp 921 dual springs in all there heads. I just find it hard to believe that it craps out exactly at 2 bar 14.7 psi. I don't know enough about hp tuners to know if a setting with in hp tuners is causing the issue. my tuner says its not anything to do with the map sensor.

 

May be spark blowing out, it takes alot to fire e85. Whats the plugs gap at?

 

never made it to e85. This all happened while tuning on pump gas. However ngktr6 strait out the box I checked the gap at .035. Probably to big huh.

 

Maybe could tighten the gap a little, but I don't think that would solve the issue.

It sounds like it has everything to do with the map sensor. Like Geezer said, that map sensor is probably at its limits.

 

I'm confused here. Why would the car make 600 on 14.5 psi and only 550 with 14.7 with a swapped pulley. If you're in fact running only a 2 bar then its at its limits...only making more boost. Doesn't sound like the map to me. That would only keep you from making more boost. Like stated above, drop the plug gap a bit and swap out your valve springs as well as the map. Are you intercooled? If so, can you do a boost leak test some how? I'm not familiar with S/C setups like turbo applications.

 

I run my tr6 at .026 at 20psi on e85

 

" That would only keep you from making more boost.".. Huh?

Op.. Do you know what bar the MAP sensor is?

 

Should have been more specific. If you over run the map, it will not read...correctly. Causing issue's trying to run more boost. Just like a Maf will loose signal if you over run it. In that case, you can't tune for a/f and **** goes south real quick.

 

If the car sat with the springs loaded that long they are definitely weak.

 

It wont loose the map signal if you max it out. It will just keep thinking its at max. You just have to know what boost its making with a boost gauge and adjust fuel and timing according.

 

i didn't read it very well but you said you shrunk the pulley. Is it possible you are experiencing belt slip now that you have a smaller pulley and less surface area to grab on to? I am just throwing this out there. I am at work and will need to read it better when I get home....

 

I think the reason for the hp difference is we made 600hp at 14.5psi at 6300 rpm on the 84# injectors tuned to 11.7 afr 16* of timing.
Then we switched the injectors out for 120# so we could run e85 how ever we still had to retune the pump gas tune first Also for the bigger injectors and smaller pully ion the blower. I don't think we ever got the timing back up to 16 because of the issue with the power palling off at 14.7 at 5100 rpm.

I did pull the plugs out today they were gaped at 36 and one was 26. The straps were slightly overheated so I think a colder plug is in order.

I put some ngk br7ef plugs in and gapped the to 22.
Going back on the dyno to see what happens

 

belt did slip at first I had to install next size smaller belt. We can see from dyno chart (witch also monitors boost) that the boost climbed nice and smooth up to 16.5 @ 6300 rmp.

You can also see the mph climbed nice and smooth witch indicates there was no tire slip either.

im still thinking plug gap is the problem one more hit on the dyno with the new plugs should tell me something.

 

Boost is there 16.5 and climbing. Afrs are steady at 11.5 ish. no boost leaks. power drops of instead of rising once boost hits 14.7. just so happens to do so at 5100 rpm. so from 5100 and up the power is going down>.

 

Is your second pump on a hobbs switch? Is it possible that a vacuum line going to the hobbs switch that runs the second pump some how got disconnected? That happened to us out of the blue and car nose dived. We thought the pump went bad. It just came loose so no signal to turn it on.