AJGls1

didnt think wastegates should be seeing vac?

jtotheizzo

The Wastegate reference location argument is as old as turbos. I definitely dont want to get in the middle of that but I will say what I did. I chose to run the reference to the cold side piping before the intercooler. My theory there was I wanted as much control as I could get over the wastegate as I intended to run low boost. I also believe that since most wastegate manufacturers say they should not see vacuum that it was a good idea to listen to them. I don't see any real difference in getting the reference from either side of the intercooler. If there is a huge drop across it I will just turn the boost controller up or use a different spring.

All of that said I will say that I am running a very similar setup. Same turbo, same motor, same intercooler, and piping. With stock Valvesprings, running similar boost and timing (and having major boost leaks I later fixed) I was trapping 115 in the quarter. At my weight that is good for 450 tire. Taking into account how slow my setup spooled on that run (5 seconds to hit 10 psi) I am betting it was really pushing 500 or so.

While it is true your mileage may vary I am not sure I would think valve springs at this point. There is something very fishy going on here. I find it odd that you cant even make gate pressure with a less than optimal gate setup. Everything I am seeing here looks like you should overboost.

Where are you referencing your boost gauge from?

PontiacPOWA

Ding ding ding!

You're floating the stock valve springs dude. All this talk about boost leaks and exhaust leaks... His boost leak is through the valves. Its holding at 10 lbs and 3500 rpm, but as rpm rises the stock springs cant hold both the rpm, and the boost. Put some aftermarket springs in there and i bet you pick up 100hp and decrease spool time dramatically.

racinea64

i think thats what i'll do i shouldnt have to have it re tuned for stiffer valve springs right?

JoeNova

A whole lot of boost has been pushed through the stock valve springs before. 7 PSI with a stock cam shouldn't be stressed them.

Its probably a good idea to upgrade them for some head room, but unless they have 200k+ miles I wouldn't be so sure to call them out.

racinea64

i was gonna go with Z06 cam and springs it seems to be a good fit for forced induction and it dont cost an arm and a leg plus you can get away with not having to cut the spring pockets for clierence.

Forcefed86

iTrader: (4)

Thats a pretty big assumption. Guys running 22+psi on stock valve springs on some LS1's with factory springs. Not seeing valve float till 5800 or so RPM. LS1's came with a more aggressive cam too. I'm not saying valve springs aren't a good idea, but I'd bet there's another problem.

8* of timing is stupid low. Post a picture of your timing map. You should be around 24* at 1psi. Tapered to 14-15* until around 10psi IMO. Then start taper it down to 11-12* by 16-18psi. You'll see a HUGE jump in power with a little timing. You're nowhere near where you need to be. Again... sounds like your tuner is clueless.

Rogue Status

iTrader: (1)

I totally agree, but the valve springs can't be helping matters. I am all about eliminating variables. It needs springs anyways, so throw in some .600 lift rated springs and hit the dyno again, look for a change. If it is minimal, keep looking.

From the looks of the crossover, charge piping, and watsegate placement the setup is far from ideal. I do however remember Denmah's truck with the 88mm turbo and the worst crossover I have ever seen (he knew it was bad too) and that thing still made a metric ton of power for what it was.

One thing to look at, did you put the seal ring in the wastegate? If it is constantly leaking that would absolutely cause the turbo to be SUPER laggy and would go unnoticed with the fender exhaust as I am sure it is not quiet under the hood.

brandon6.0

iTrader: (32)

well like forcefed said timing being extremely low for the amount of boost your running will kill power like crazy. copy what he said he knows his ****.

Timing being low will make that 5.3 feel like a lazy dog out of boost. Timing should easily be around the 15* mark with 7-10psi.

JoeNova

I must've missed the 8 degrees bit. That's about 10 degrees low for 7 PSI. That's quite a bit of power, torque, and spool being left on the table.

jay_rich

iTrader: (8)

Timing is extremely low. Mine is set to 26 degrees under 105kpa. Then from 105-225 KPA I transistion from pulling 2.5 degrees to around 18 degrees at 225kpa. Its a pretty linear pull.

Also I have been driving mine more lately. I am seeing positive pressure around 2600rpm on my GT45, I would say around 6psi by like 3200rpm.

Stock 5.3L, LS6 cam, BTR dual springs, 3800 triple disk, 4l80e.

Jay