Went to the dyno, with an UNLOCKED torque converter (which is why numbers come out low, that is NOT what the car really puts out, but at least I can see the power and torque corves). Usually actual 1:1 vs. unlocked converter is a 15-20% difference on some cars, the car has trapped 117mph with 3350lb with me.

1st of all, dynojet's suck! went with 16psi from the street and at dyno it was 14psi since no load, afr was also in the mid 10s (11's on street). I did another two runs, the 3rd was at about 18psi, still rich in the 10s, same exact curve, however the same power output at higher rpms 5500+!!! as if there is something holding the engine back after certain boost.

After 5600RPM all curves ended up the same (so weird). Looks like there is a big restriction at 5440 rpm where it suddenly drops. Can this be a manifold issue? I know my timing was low as well but damn. There was also no knock either. AFR mid 10s, timing aprox 16's, meth/water injection (7gph+2gph@150psi)

Setup:
This is a rear mount turbo maxima with swapped VQ35, wiseco 8.8:1, eagles, HR HG, stock DE cams, and no variable cam timing (I am using VQ30 fixed timing sprockets/chain). AFR in the 10s, Timing max at 16-17deg.
Charge pipe 2" to the IC then 3" from IC to engine. Exhaust from engine to the turbo is 2.5" all mandrel bent, no resonator, no cats, nothing just piping to the turbo. Out the turbo is 3" into a Dynomax VT muffler which is basically an open downpipe (so this is def not the cause).

My theories on why HP is not increasing:
- Possibly the manifold, but will the manifold cause a choke like that?
- I thought maybe the turbo is running out of breath but my MAF voltage increases with higher boost and never drops off, even at the RPM's where the dyno shows lack in power, so Im ruling out the turbo.
- I may be spraying way too much meth/water(more water) killing my power.

Side note: I know the turbo is very laggy as per dyno graph, I have since changed to a smaller turbine housing which has lowered the full boost mark 1000rpm's (full boost at low 4k now)

what yall think is the issue here?


Just in case, turbo specs are:
compressor
60mm inducer
84mm exducer

turbine
76mm inducer
62mm exducer

 

its breaking up on top. misfiring or something. possibly your water/meth setup. check your plugs and plug gaps too. the loopdy loop at the end of the red pull means your car actually lost RPM for a moment. thats a bad miss.

 

BTW does a built VQ really need water/meth at 350whp??? i would just turn that stuff off right now to eliminate a factor until everything else is sorted.

and what make is your turbo.. you listed specs but what is it?

 

Well i wouldnt say 350whp but I agree, I think I am spraying too much water/meth for my low compression, I am def going to reduce that alot. The car felt very smooth and no noticeable misses audible or that one can feel, but perhaps combustion wasnt very efficient due to too much injection. Spark plug gap is at .037 @ 16V.

The turbo is an HX40 Holset, on the dyno it had a 18cm^2 turbine housing, which some say equates to about 1.2AR or so.

 

Your exhaust manifold also can be small.

 

Like sasha said in the other post: your turbine housing will be your restriction point on that turbo which will choke it up top.

you said 2.5" exhaust from engine to turbo but does that include headers? stock manifolds are tiny and will restrict.

 

Turn the water/meth off and gap your plugs down to .028

 

2" IC piping is good for about 500cfm, after that it turns in to a restriction as the air speed goes past 304mph.

 

I understand about the turbine housing but its impossible, it is enormous. I do have stock vq30 headers, a little better than 3.5 headers but still stock. That might be my next change. Like mentioned I will take off the meth, meatbag how come you suggest reducing the gap? I haven't had misfire.

 

You running Utec? They are notorious for spark blowout due to weak coil pulse... even mine did it at times at only 380-400 whp.

 

what kind of power would 500cfm be at?

 

Nah, I have an emanage ultimate. And a voltage booster on the coils, I think my ignition is pretty strong .

 

Can the motor be misfiring without a person feeling it?

 

OK so I have something to rule out, it is not the headers. Here is why, this is a dyno of a buddy of mine where he had a stock block 3.5, same cams/heads/timing equipment, no methanol, at around 9psi with a smaller turbo HX35(12cm turbine). On his dyno he has the EXACT same drop of power at 5400rpm. This also rules out spark blowout, misfires. Its getting closer to be two things, either the intake manifold just plain sucks, or the 2" diameter piping (which he also had) is not good enough. However at only 9psi he still got that drop in power, i seriously doubt 9psi would be an issue on 2" piping so I rule that out too. I guess I either get a Z manifold from one of you guys lol, or get a custom one.

 

so he's using less psi but he's on a smaller turbo. Smaller turbine on a smaller turbo would cause a restriction at lower psi.

My room mate is putting an hx40 on his turbo coupe (firebird). He has it back in ohio right now so when he brings it back in a month or so i'll take pics comparing it to my 6765 precision. It's smaller than my 6765 so it's not as huge as you think.

 

It has similar spec as a 6262 (its probably bigger than 6262), and I am pretty sure a 6262 will not choke. I am positive it is not my turbo.

Smaller is the new .70AR Bullseye T3 housing I just got, and larger is the 18cm^2. Dyno was with the big one (note: height looks huge because its internally WG, .70ar isnt.)

 

you have a loopdy loop in your dyno graph but you say the car isnt misfiring?

thats a miss! and based on how you complain about the dynojet and boost controller setting, that means youre on a 248c... 248c is a big *** intertial dyno and it will really momentum its way through some missfiring. to see it on your graph there, means its decently serious.

you may not feel it in the seat of your pants, but according to your graph its only happening for the last 500rpm of your pull... and for such a brief moment and through all the noise and excitement, you might not feel it in your *** right away.

i used to run .043 gap on one heat range colder plugs on my stock engine. and made the smoothest 467rwhp anyone ever saw... BUT that was only 9psi. You are at twice that boost. Also, based on how your higher boost run, as it gets towards redline, and it drops down and does no better than the lower boost... that looks VERY VERY much like an ignition system weak link.

 

Thank you very much for your input. Although I have narrowed down the issue to both intake manifold and cam timing (too much overlap maybe), I will still disconnect the meth and lower the gap.

Since I wont be able to do cams anytime soon, for now I will be putting a an MREV2 along with spacer (Got a great deal). Then see how the curve changes.

 

BMW M30 (3430ccm) with M5 head and HX55 (22-or 23 ccm turbine house). Ok this is in front, your is at the back, but I think the Hx40 is small for you. But I still say your exhaust header is the problem.

 

Pictures of your piping?