4.8 boost letdown
4.8 boost letdown 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
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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
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
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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
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
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Joined: Mar 2014
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From: Ohio
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.
To those who said 600 won't happen on 15 psi, its been done before.
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?
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?
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Joined: Mar 2010
Posts: 519
Likes: 2
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.
To those who said 600 won't happen on 15 psi, its been done before.
