Couple Runs, NPB at 11.2

[Foose04]

First want to thank Darryl and Zach for taping a couple runs. I enjoy looking over the video's just as much as I do racing, so thanks again.

Made a new best, that said I've hit a wall and the trucks making the same power even as boost rises. Pretty much at the same power it did with the old 70mm turbo, even at the same boost now 76GTS.

First off I've found couple problems. If you notice in the video's, the truck is pretty damn quiet on the back half and second run. Well my first Jegs brand cutout stopped working and now this one is closing during my runs. It's nearly shut after a pass. My after cutout exhaust is less then impressive press-bent 2.5inch piping and another muffler.

Other then exhaust I think the LS6 valve springs may be opening up when boost is at or around 14-15psi, so there is no gains above that? Thoughts?

Here's the runs : http://youtu.be/aSKJSHVN-rw?hd=1

[CINDERBLOCK]

trucks running good man... I couldnt make the trip up there this weekend. Went to Bowman instead.

[1iron]

I'm not sure what you are saying about boost opening the valves. Never heard of that. More boost = more power. If a small turbo can make the same boost it should make the same power if everything else is the same.

[98nbmz]

Boost doesn't matter so much as backpressure. A car with a more efficient turbo system (less backpressure) can actually get away with less spring.

As an example 20lbs of boost going through the intake isn't going to effect anything when the valve is on the seat. When the intake valve opens you have flow into the cylinder and pressure is trying to equalize between the intake and the cylinder. As you reach intake valve closing the compression cycle starts and pressure in the cylinder immediately eclipses pressure behind the intake valve.

On the exhaust side however you may as an example have 40psi backpressure. As the exhaust valve is closing your intake valve starts opening (overlap) and there is still 40psi on the back of the valve but little pressure in the cylinder to balance it. At this point you can bounce the exhaust valve causing a drastic loss in rpm/power.

For the hyd roller stuff that's going to see 20psi boost I usually run a spring with around 400lb/in rate so I can get 200lbs on the seat and 425 or so over the nose. Seat pressure is what's important here.

That is very generalized and like anything else should be decided on when selecting the rest of the parts for the combination. I can say with certainty that 918's will not be enough for a turbo LS1 that will see 20psi boost

Taken from ls1tech, maybe itll help

[silver fox]

Check your waste gate or blow off valve. The spring might be getting weak and can't hold the increase pressure.

[chrisheltra]

Congrats. Your slowly creeping up on the 10's just like me. Its frustrating as hell isn't it?

[bwelch]

How much air are running in the hoosiers?

[Foose04]

Hoosier's were run at 13 cold, around 14 after a pass.

My boost reference is measured at the manifold, so the wastegate and BOV are working fine.

I have a bottle kneck for sure though. I can share HPTuners logs, but I got about 1.5MPH gain going from 14psi to 19-20psi boost. Also I only used a couple more % fuel, so the way I see it, the air's not moving through the engine.

Thanks for the info 98nbmz, i'm going research more on the springs.

Chris, it is a little frustrating. Seems like I "should" have had it a few trips ago.

[1iron]

Originally Posted by 98nbmz

Boost doesn't matter so much as backpressure. A car with a more efficient turbo system (less backpressure) can actually get away with less spring.

As an example 20lbs of boost going through the intake isn't going to effect anything when the valve is on the seat. When the intake valve opens you have flow into the cylinder and pressure is trying to equalize between the intake and the cylinder. As you reach intake valve closing the compression cycle starts and pressure in the cylinder immediately eclipses pressure behind the intake valve.

On the exhaust side however you may as an example have 40psi backpressure. As the exhaust valve is closing your intake valve starts opening (overlap) and there is still 40psi on the back of the valve but little pressure in the cylinder to balance it. At this point you can bounce the exhaust valve causing a drastic loss in rpm/power.

For the hyd roller stuff that's going to see 20psi boost I usually run a spring with around 400lb/in rate so I can get 200lbs on the seat and 425 or so over the nose. Seat pressure is what's important here.

That is very generalized and like anything else should be decided on when selecting the rest of the parts for the combination. I can say with certainty that 918's will not be enough for a turbo LS1 that will see 20psi boost

Taken from ls1tech, maybe itll help

So the cutouts not staying open might be the issue?

[Foose04]

It's not helping thats for sure, but I still feel something else is holding me back.

[chrisheltra]

Whats the seat pressure on the LS6 springs?

[Foose04]

90 lbs. @ 1.8 in., 295 lbs @ 1.250 in., .570 in. Maximum Lift

[98nbmz]

I bet its the springs/seat pressure. Why not do a cam and spring swap?

[chrisheltra]

Maybe Randy will chime in here because my memory is a little fuzzy here but I think Lightning heads stock are 90# and usually if increasing the boost past 18 psi it is recommended that you upgrade the springs. IIRC mine are 120#. I'm unsure if springs and valves and all that jazz respond differently because of different head design and 90# is sufficient for you or not, but that may be were some of your issues are coming from. Not enough seat pressure and your turbo is pushing the valves open which will cause some boost bleed off. This is all purely speculation and not a professional diagnosis.

[BAD BOB]

it could be pushing the valves open. when i put the stock heads on mine it was need to have the springs replaced to a set of dual springs with good seat pressure.

So what is the issue that you are having? just that the new turbo isnt doing any more than the old? and the exhaust, depending on what is on it, does have that much effect on the turbo unless its really restrictive. my car runs through full exhaust and does pretty good

[98nbmz]

Look at patriot extremes not too expensive at 250 bucks

[Foose04]

Yeah the main issue is 13.5-14psi run 11.3@119-120. Last run was mostly 20psi, ran 11.2@119. No knock, same timing, safe a/f's. The only reason it went 11.2 was because of the better 60, the HP the truck is making is staying the same.

I'm pretty sold on it being a spring problem though, atleast I hope so.

[chrisheltra]

Originally Posted by 98nbmz

Look at patriot extremes not too expensive at 250 bucks

I wouldnt touch patriot with your pecker.

[BAD BOB]

i got some from texas speed and they were around 350 but said to be very good for my application with the turbo. just try them and see what they do

[98nbmz]

Or Ford

Originally Posted by chrisheltra

I wouldnt touch patriot with your pecker.