Ds.Motorsports

Motor is a built 6.0 iron block 10.8:1 to 11:1, fast 102 intake unported, NW 102 tb, prc 237cc cnc heads w/hollow stainless intake valves, solid exhaust valves, tsp custom grind cam 227/234 .629 .615 114lsa, procharger 1500hp 5" intercooler, 1 7/8th tsp long tubes with dual 3" x pipe with spintech mufflers, in my 99 trans am, t56 car McLeod twin disc clutch, moser 12 bolt, car was tuned by jorge at JMS racing, made 810whp and 720 trq at 15lbs of boost on a 4.25 blower pulley no belt slip, traction loss or boost leaks, 93 octane and alky control meth injection, went to go 3.90 blower pulley (18 to 20psi of boost) with recommendation from bob at brute speed , car only gained 1.5lb of boost bringing me to 855whp and 790trq, trying to figure out where my problem is, does anyone have recommendations?

Fyi i thought maybe air filter was restriction, back to back comparisons on dyno jet dyno, removed air filter lost 40whp, put back on, i gained the 40whp back, no heat soak

@Tony @ Mamo Motorsports any input?

Tony @ Mamo Motorsports

First thing that comes to mind (somewhat stating the obvious) is the lack of any of my products....heads, valvetrain, ported intake, custom cam etc....included in this build.....LOL

Seriously.....I could have been alot more help to you prior to your selection of parts than after.....my purpose built MMS 235 NFI heads would have been kick azz on a built like you have described. I suspect your familiar with them.....heads I built/designed specifically with boost or nitrous oxide in mind with a specialty exhaust port / exhaust valve larger than you would find in a typical set of cathedral heads to help evacuate the exhaust side of a boosted or spray engine which really determines how much power is made possible by either form of power adder.

That shameless plug aside I feel your cam is way too light on exhaust split for that type of boost (should have been twice that at a minimum IMO.....at least 14 degrees larger than the intake and potentially more depending on heads....maybe a touch wider on the LSA as well), but what you describe with removing the air filter is very strange and I would spend some time trying to figure out whats happening with that. Is the engine detonating some from the additional airflow of the filter removed and that is potentially hurting power.....or is the air filter helping to act as a radiused entry and that is why power is being added by keeping it in the system. You need to do some digging there.

I would also recommend you run this on race gas and meth to eliminate fuel as part of the problem you are experiencing (is the fuel your using fairly fresh?). You have alot of static compression and getting the proper octane to this engine at those levels of boost is going to be important, You really should be feeding this engine straight E85 IMO.....or at a minimum convert the car to flex fuel so you can really get at the tune when you have the opportunity to run the better fuel closer to straight E85.

Good luck sorting this out but the couple of things I mentioned would be some of the first places I would look.....also make sure your plugs are gapped tightly also and are cold enough that they aren't a potential source of detonation. In fact I would be pulling all of them to see how happy they all look.....they should all be burning and looking very similar if the engine is happy from bank to bank. Another one of those must check items early in the diagnosis.

Next time get me involved before you build your combo as I would have liked the opportunity to have earned your business

Regards,
Tony

ddnspider

iTrader: (26)

LOL@Tony.....pretty random to just ask to solve the problem and don't use any of your parts. The airfilter pull losing that much power is super wierd too as mentioned.

WTF?

Check boost pre intercooler.

NitrOmm

iTrader: (1)

Are you using an Aster Bracket ? Seems to me the first thing to look at would be the belt slip. It can be deceiving with no signs of dust etc.. I don't think you can get 18-20 lbs without some method to mitigate the belt slip on the 8 rib for our cars. Your numbers @ 15# as well 16.5# sound correct. I cant speak to the air filter anomaly ?? but a 3.9" pulley will certainly make that belt scream for help.

Ds.Motorsports

Yes the aster bracket with a gates RPM belt and no belt slip, i looked on hp tuners on the map sensor reading and ny innovate boost gauge climbs up smooth and holds 16.5 until redline, also check for boost leaks, couldnt find any, quite a few people are leading to intake manifold runner design, since it is cathedral port they dont offer race runners or mid length runners like they do with sqaure port and LS7, not to mention i did blow an fuel rail hold down knurl out of the intake, my guess was from the positive pressure pushing on the injector at higher boost levels, i fixed it but since that happend i am going with a @Frankenstein low pro billet intake manifold for peice of mind and not burning my car down from a fuel leak, was going to do holley hi ram but i am a street car with urethane mounts so i would risk cracking a windshield

Bob@BruteSpeed

iTrader: (16)

Very strange problem, but like I mentioned in our e-mails, unless that FAST 102 is cracked I don't see it being the problem. An inefficient intake design often will make more boost, although be down on power. Found that out twelve years ago when the guys swapped out an LS2 intake for a FAST 92. Lost two psi of boost but picked up power big time.

You don't really have an F-1A-91, do you? I noticed that in the thread title. Bob