n20z28

iTrader: (3)

Ok guys I been on hunt for 600hp on less than 15lb... my setup is a 02 4.8 with basic boost upgrades has a little on larger side cam 224/228 tx speed on 114 with 918s.... ls6 intake ... the turbo is a t4 tc78 non ic but I got water meth my iats are around 95-105 under boost... timing is 14° at wot and high 20s pre boost... my last dyno was 481/483tq on 15lb and the car hp levels out around 5000rpm .... any ideas y I can't seam make more

krwyellowZ28

iTrader: (10)

sub'd for answers.

Photochop

iTrader: (74)

More info if you could. What trans/converter (if auto), what fuel, whats the fuel system consist of, what wastegate, and what dyno

n20z28

iTrader: (3)

M6 car... 44mm WG ... 91 oct with water meth ... dyno jet dyno

n20z28

iTrader: (3)

Stock fbody lines walbro 450 with 80lb inj so far its 55% duty cycle

71 chevy

iTrader: (18)

600 whp at 15 psi will not happen. And certainly not with the amount of timing you're running

99z28383

iTrader: (1)

I agree, especially without some better flowing heads.

jay_rich

iTrader: (8)

Seems pretty low for a M6 car. Stock rear? Whats the AFR's like? Post a graph.

Also what A/R is that TC78, I assume the 68mm turbine version?

Im gonna say toss the 918's in the garbage and put a real spring on the car. My old 383 LT1 was floating 918's tossed in pac1218's and it picked up 60+whp. Similar springs but Comp had some issues with 918's before. id never use them.

Jay

stock48

iTrader: (17)

On gas It takes a lot more psi of boost to make the power without an intercooler.

n20z28

iTrader: (3)

I'm starting to think it is a valve spring problem Jay. we played with on the dyno tried running it up to 12 .2 no power increase it seemed to like it the most around 11.0.... yes its .96 ar

n20z28

iTrader: (3)

before I got the TC 78 I was running a god speed t76 with a 63 mm wheel .81 AR and I managed to get about the same numbers now then upgraded to Turbonetics and it picked up just a little... I assume the wheel was too small on the Godspeed was why my power fell off at 5000 figured it was choked up now switching to a bigger unit and it does the same thing so I know I have another problem

n20z28

iTrader: (3)

I understand the e85 takes more timing but I figured with 91 and 50/50water/meth mixed it would be more than sufficient

boostpower

Sounds like a valve float. Look into replacing your valve springs. Big cam plus boost you need good amount of spring pressure.

stevieturbo

You say you're using 50/50...but how much actual quantity are you spraying ?

JoeNova

Valve springs are likely the problem. How much water and meth isn't going to cause power to drop at 5000. With that can on a 4.8 it should pull to 7000. You're giving up 1200 or so RPM worth of power gains.

To those who said 600 won't happen on 15 psi, its been done before.

n20z28

iTrader: (3)

Meth t nozzle one is 625 other is 175... so 800ml pump starts at 4 psi and full on at 8-10psi

Forcefed86

iTrader: (4)

There's no way your making 300whp on motor at 5k rpm NA with that 4.8 setup. Best case scenario you'll double NA HP at 15ish psi. So if you limit your self to 15lbs you need to be pushing 300+ NA at the wheels to hit your goal.

As said, try the correct springs and rev it out more. I don't think the LS6 intake will make very good power over 6800 will it? Why are you limiting boost to 15lbs?

turboventura

If you lower the boost and it revs higher, or raise the boost and it levels out sooner I would think valvesprings, doubt the turbine is choking out at that level on a 4.8

95bowtie

**** I made 610/540 on just 10# 18* with e85 and a big *** cam with 15* of overlap. Rearmounted t6 76/85 old school tv series garrett

jurezgez

I'm starting to think it is a valve spring problem Jay.