Well, here goes:

Ran the car at full boost for the first time, and when I say full boost I mean 16-17.5PSI since the boost controller stopped working on its own, so I couldnt lower the boost , but anyways:

645RWHP @ 6350RPM @ 16.5-17PSI of boost on my twin turbo 427 on 93 octane pump gas WITH filters off. mid 11AFR, decent timing. I almost commited suicide.

The last dyno session the car did 575RWHP @ 7.5PSI and I thought that was insanely low, this was with the filters/aircleaners.

A few things to note are:

1- All of the dyno sheets ive seen of those turbos on 427s seem to max out at 5500 and drop off after that, yet on my dyno runs they were maxing (and flatlining at 6400RPMs).

2- The twins boosted like a centrifugal on the dyno, with boost maxing in the very upper RPM range and power was EXTREMELY linear, with the HP graph looking more like it was drawn with a ruler. So im wondering if its a case of "manipulating dyno load" to get the car to fully boost sooner, which it should do by about 4000rpms with those turbos.

3- We definitely went beyond compressor efficiency range with IATs reaching 221F at 17PSI on the top of 4th, yet thats not completely the problem with the car not making the power it should be making even at midrange with the turbos in their sweet spot. FYI, we turned IAT vs spark off and barely saw any knock even at those skyrocketing temps. My IAT sensor is working fine.

My goal was to run about 730-750rwhp on pump gas, and then add some race gas and meth (which I dont want to use on the street) and make a magical number. Especially that TTi came up with a bigger turbo upgrade for the kit.

facts:
2.5inch turbo downpipes (hard to fit bigger ones, but not IMPOSSIBLE)
wastegates routed back to exhaust
turbonetics t3/t4 .82 a/r

The only things I can think of right now, before adding meth injection and ruining my original plans are:

- dumping the wastegates to the atmosphere and lowering exhaust backpressure in that small 2.5inch pipe.
- try to fit a bigger exhaust, and run an x-pipe to equalize between both banks. car has no h nor xpipe currently.
- adjust the boost controller to 13.5PSI, and adjust the boost gain so boost ramps up as quickly as possible


Other than that, im completely out of ideas, and im short of about 150RWHP from my target HP, taking into consideration my target HP is 730-750RWHP, and not 645RWHP with no filters on.

dyno, is a dynodynamics calibrated to read like a dynojet.
ambient temps were 93deg F.

Any help would be appreciated.

 

post the dyno runs and hpt log files. With the boost controller plumbed correctly you should have pretty solid boost off of spring pressure.

Your ideas may help minimally but right now there is a major problem somewhere for you to only be seeing those numbers.

Once you've had enough just ship the car to me and I'll get it straightened out for you.

 

Could be so many things. Boost leak is one. Burst knock, Knock Retard etc. If you scanned the proper things during your dyno runs, there's a good chance someone will be able to figure out what's wrong.

 

How does the "seat of the pants" feel on the street?

 

This will have no effect after the turbos as the turbos will smooth out the individual exhaust pulses into a realtively steady output.

The bigger exhaust would help out but IMO that is frosting on the cake. You are missing some cake right now.

Can you post your last dyno run chart?

Jim

 

Sounds way off. I was making over 900 wheel at 16.5#.

 

u may need to log the input shaft and compare to the output shaft it almost sounds like u may be blowing threw the tranny or your converter

 

1.lean up your afr

2. your turbos are small.

 

That doesn't explain the 100-200whp the car is lacking....not to mention mid 11s isn't exaclty conservative on a high hp turbo car.

I do however agree that t3/t4 turbos are a tad small for a 427.

 

i lost hp going that low of a afr. put good gas in it lean it up and it will gain hp.

 

boost leak is highly unlikely, especially if you see how everything is tightly fit and clamped, but I wanna check the BOV for signs of leak. Now again, it has to be too obvious if its loosing this much power, but its not.

The tuner was saying something about valve stems leaking

 

Trust me my exhaust pulses are nothing like smooth, which also gives the wideband a hard time, im also doing it for the sake of the smoother exaust note.

 

I have a rule not to ignore things even if they're "unlikely". That's when you go all around the world only to find out that it was something that you ruled out without checking. A pressure test of the system would be the way to find out. Cap off the turbo inlets and throttle body and put any kind of connection you choose to apply compressed air to the system. Hoses tear, blowoff valves get hung open, bad intercooler weld, one turbo locked up (highly unlikely), one turbo compressor wheel broken. **** happens.
Valve stems leaking? Either you misunderstood him or you need to tell him to .
Do you have logs of the dyno runs or no?

 

Jim, you dont wanna look at the tune but again we were not tuning properly, just wanted to make sure we cleared off that machine-gun misfire issue from last time. Other than the crap tune, on WOT AFR starts at 11.3 and ends up at the high 11's because actually fuel pressure was dropping (which ill take care off).

ill re-route the boost controller (it was working fine, until I changed something). Ill have it set at 13PSI, and have the gain on and ask the tuner do change the dyno load settings, I want to see the car making max power before 6000rpms to know the graph is fine, and not not dropping at all.

right and there is a very big chance I end up sending the car to you man >.<

 

Well, ill go ahead and check if thats the case.

thing is, why would the kit max out at 6400 and not at 5600 where it should. Im guessing the curve should start sooner, boost earlier make its power (725ish) and drop after 5600rpms to where it is now at 6400. My guess is it should make more power at 6400 with lower boost while keeping it in its efficiency range. but what do i know.

im pretty sure thats what he said

 

a friend of mine said this is a low 700 car when we had the car at 575rwhp, and hes not a friend that drives a suburban either, he has a modded z06 as well.

I know the car will rip on the street, but its definitely not doing the dyno number it should be making before I consider it "fine"

 

The car will make a little more power with a leaner mixture at midrange along with the boost controller ramp and dyno load, however it was kinda lean at the top, almost touching 12 because I figured out FP was dropping up high, which I am not to worried about at least for the time being.

 

If you don't have solid boost control the power curve will match the boost creep.

If you have say, a solid 6psi boost from 3600-6600 it will likely peak closer to where you expect it.

Does the car pull smoothly at WOT? With those #'s it almost sounds like it's down a cyl or 2.

 

this is whats happening, definitely. I remember previously, the car felt like it wanted to lift itself off the dyno due to how fast the turbos spooled, I had the boost controller set-up properly last time though.

Car pulls smooth, but tuner kept on looking for issues, he says he could feel the car misfiring, well it was at the beginning, the plugs arent new ones either, we were adjusting the drivability and thought of doing WOT, it took the car about 10mins of idling for the plugs to clear up and run to redline. I used a misfire config file I got off HPT forums, and we figured out cyl#1 plug was gone, swapped that one and gained a bunch, but it was still low on power.

Now again, what im trying next is to set the boost controller and gain properly, if the car has steady FULL boost from 3500-4000 up to redline, it should be maxing at where turbos of those size will, and drop after that. The 212 degree F IAT@ 16.5psi was definitely not nice either, so im thinking MAYBE 645RWHP at a boost level way out of compressor efficiency and further away from the turbos "normal" peak HP and pump gas doesnt sound too bad lol. Will try again in a few days.

I asked the dyno operator to get the car to boost quicker with some more load, he said hes setting the car to whatever load it will see on the street, I dont know how true that is however, taking into consideration hes just adjusting the load **** and not taking the cars weight, aerodynamics and other parameters into account (which is not as simple thing to do either i think).

Anyways, coming up next is proper boost controller gain, more dyno load, and a few things checked up, fresh set of plugs and some luck? >.<

 

You can try the car in a higher gear on the dyno if the dyno can not load it properly. I am not trying to question your approach but sometimes people get hungup in recent events, when finding these problems remember to goto the basics, you need 4 things..

Air - Check for boost leaks (run turbos in a very inefficient area of map)
- Check for exhaust restriction (will lead to less air for same boost)
- Check for intake restrictions (will lead to less air for same boost)

Compression - Piston/Valves (easy enough to check with a leak down tester)
- ensure valve float is not lowering effective compression

Fuel - Best way is through a wideband - use two if you are unsure

Spark - Ensure your plugs are not fouled / properly gapped
- Ensure the computer is not pulling to much timing
- Ensure base timing is good
- Ensure your coils are getting the current required
- Ensure your dwell settings are correct
- Ensure no wires are burnt/damaged and resistance is good
- Ensure quality RPM signal through pull (coils are being told to fire)

Hope this helps to uncover your gremlin.