LS7 FAST 102 running out of steam?
Teching In
Joined: Nov 2009
Posts: 5
Likes: 0
Teching In
Joined: Nov 2009
Posts: 5
Likes: 0
Thank You all for your input and ideas!
I am trying to validate or unvalidate the need to look at spending all that money on a sheet metal intake.
If folks are saying it is not the intake, and can show they have been able to feed a naturally aspirated engine through the FAST 102 intake, to and past the levels I am at, then the problem must/may be something else.
I know I need the car to be able to pull 7,200 - 7,500 rpm to get me through the 1/4 mile with my 4.10 gears.
I am trying to validate or unvalidate the need to look at spending all that money on a sheet metal intake.
If folks are saying it is not the intake, and can show they have been able to feed a naturally aspirated engine through the FAST 102 intake, to and past the levels I am at, then the problem must/may be something else.
I know I need the car to be able to pull 7,200 - 7,500 rpm to get me through the 1/4 mile with my 4.10 gears.
Teching In
Joined: Nov 2009
Posts: 5
Likes: 0
Teching In
Joined: Nov 2009
Posts: 5
Likes: 0
Some more information, if I understood the shop correctly.
The car is just over 570 rwhp at 6,500 rpm. Started stumbling bad @ 6,600 rpm. Removed fuel to get the car to pull to over 7,100 rpm, but this causes the power to drop all the way down to 310 rwhp at 7,100 rpms.
Prior to rebuild, the car would peak out around 525 rwhp at ~ 6,500 rpm, but would hold the power pretty well to 7,100 rpm.
The car is just over 570 rwhp at 6,500 rpm. Started stumbling bad @ 6,600 rpm. Removed fuel to get the car to pull to over 7,100 rpm, but this causes the power to drop all the way down to 310 rwhp at 7,100 rpms.
Prior to rebuild, the car would peak out around 525 rwhp at ~ 6,500 rpm, but would hold the power pretty well to 7,100 rpm.
Cam specs are - 243 247 LSL 112 + 4.
I will look up valve size when I get home. I can say that the valves are the hollow stem steel variety from MAST, and the springs are their top of the line.
As far as coil bind, the springs were set-up by the shop that did the heads to match the cam.
I will look up valve size when I get home. I can say that the valves are the hollow stem steel variety from MAST, and the springs are their top of the line.
As far as coil bind, the springs were set-up by the shop that did the heads to match the cam.
What lift is the cam?
Did you upgrade injectors?
What spark plugs are you running?
What is your fuel pressure?
What fuel are you running?
Are you tuning with HP tuners? EFI Live?
Did you upgrade injectors?
What spark plugs are you running?
What is your fuel pressure?
What fuel are you running?
Are you tuning with HP tuners? EFI Live?
The lift numbers on the cam are .661 in for both the intake and exhaust.
On one of the notes from the guy who did the heads, is says...
Distance from max lift .050 to .075 to coil bind.
I hope that answers your question...
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Verdad Gallardo What lift is the cam?
Did you upgrade injectors? yes - Siemens 52.5 lb injectors. Doesn't seem to be a fuel problem. Pressure is good. Injector duty cycle is fine. And it goes crazy rich, not lean.
What spark plugs are you running? I don't know this for sure, but I think TR55's. I will tell you that the shop that has the car came to the track with me, swapped in new plugs and tightened the gap at the track. It did not fix the problem. Our initial thought was that is was spark related. Have changed plugs, wires, and coils... hasn't corrected problem.
What is your fuel pressure? Mid to upper 50's. Once it takes it's initial dip from low 60's to mid 50's it holds.
What fuel are you running? Pump gas 93 octane. Almost always Shell V-power.
Are you tuning with HP tuners? SD Tune with HP Turers.
Did you upgrade injectors? yes - Siemens 52.5 lb injectors. Doesn't seem to be a fuel problem. Pressure is good. Injector duty cycle is fine. And it goes crazy rich, not lean.
What spark plugs are you running? I don't know this for sure, but I think TR55's. I will tell you that the shop that has the car came to the track with me, swapped in new plugs and tightened the gap at the track. It did not fix the problem. Our initial thought was that is was spark related. Have changed plugs, wires, and coils... hasn't corrected problem.
What is your fuel pressure? Mid to upper 50's. Once it takes it's initial dip from low 60's to mid 50's it holds.
What fuel are you running? Pump gas 93 octane. Almost always Shell V-power.
Are you tuning with HP tuners? SD Tune with HP Turers.
• Has a 274cc intake port
• Has a deck thickness of .750"
material = 2.200" 5/16 Premium Hollow Steel Race Valve (5.450")
•Lightweight hollow steel intake valve
•Provides superior valvetrain stability
Launching!
Joined: Dec 2003
Posts: 251
Likes: 2
From: Portland OR
SD tune on an E38? With HP tuners? Presumably, using the bluecat VE table calculator? I personally will not do SD tunes on the E38, because of the difficulties in getting the VE table equations to match up closely enough to what you want. And if you get a "seam" - mathematical discontinuity - between patches in the VE range, it's very possible to drive the ECU haywire. Just my personal take - I'd rather sacrifice a few HP on the dyno and gain the safety and consistency you get with a MAF.
But my guess is, you don't have a VE table range boundary all the way up at 6500 RPM, and I'd still suspect valve train ...
But my guess is, you don't have a VE table range boundary all the way up at 6500 RPM, and I'd still suspect valve train ...
To truly set it he needs to find out exactly what each springs solid height is and then shim each one accordingly. Every manufacture has tollerances they are small but they are there.
yeah it does. I would suggest getting them all equall and maybe try shimming to .040 and see what happens. Coil bind is a tuning parameter.
To truly set it he needs to find out exactly what each springs solid height is and then shim each one accordingly. Every manufacture has tollerances they are small but they are there.
To truly set it he needs to find out exactly what each springs solid height is and then shim each one accordingly. Every manufacture has tollerances they are small but they are there.
The old hollow 2.20 valve MAST used weighs around 107 grams which is not exactly light. The stock LS7 valve weighs around 77 grams. That's a big difference.
Staging Lane
Joined: Sep 2008
Posts: 58
Likes: 0
From personal experience I don't believe his intake is a restriction depending on who it was ported by. On my own personal car there was no kpa loss on a 441 LS7 with All Pro Heads and an extremely healthy cam (more than likely larger than the OP's) although I have 4" piping from the throttle body down to the filter on my C5.
Cheers
Well, I am starting to think my best option might just be to swap to a 3.73 or 3.91 gear. I don't want to throw a bunch of money trying to figure out how to get the dang thing to run to 7,200 - 7,500 rpm. Maybe I'll just gear it to run through the traps at a lower rpm where the damn thing will run.
Opinions on pros / cons of this are more than welcome!
Opinions on pros / cons of this are more than welcome!
On The Tree
Joined: May 2004
Posts: 104
Likes: 0
From: Denver CO.
From what you describe, removing a ton of fuel, it sure sounds like a VE table tuning issue or reversion. If you are not getting enough air into the cylinder to match the fuel, you will go crazy rich. Reversion can be caused by either not enough duration on the exhaust to get the gases out at that rpm, plugged exhaust, or mismatch between the intake and cam timing. Retarding the cam might give you more RPM but if the exhaust duration is too short, you won't see a big difference. Problem is that fixing it means a different cam.
From what you describe, removing a ton of fuel, it sure sounds like a VE table tuning issue or reversion. If you are not getting enough air into the cylinder to match the fuel, you will go crazy rich. Reversion can be caused by either not enough duration on the exhaust to get the gases out at that rpm, plugged exhaust, or mismatch between the intake and cam timing. Retarding the cam might give you more RPM but if the exhaust duration is too short, you won't see a big difference. Problem is that fixing it means a different cam.
