Extremely Low Dyno
Thread Starter
Joined: Nov 2001
Posts: 5,649
Likes: 9
From: Warr Acres, OK
Extremely Low Dyno Any idea what might be wrong here. This is the result of a TSP forged LS1 long block, TSP stg 2.5 243 heads, Trick Flow cam 228/230/ .585/.585 112 +4, Fast 90 and TB, underdrive pulley, green top 42 lb injectors, 85mm MAF, lid, pace setter headers into 3" dual exhaust with a H-pipe then through some mufflers dumped infront of the axle. The car is a 98 Z M6 with the stock 10 bolt rear and 4.10 gears. Car was tuned today by me and nothing looked wrong in any of the logs during the pulls. Timing was run with 26, 28, and 30 degrees of timing with no difference between the 28 and 30 pulls, The numbers went up with 28 over the 26 pull. The car runs and drives fine according to the owner. I'm sure he will chime in here after I post this. We are thinking the problem is in the exhaust with the H-pipe and the mufflers he is using. The car owner will have to post the brand and type of mufflers. These are more like a cam only stock intake car's numbers. Not what I would expect from the built engine that is in this car with these parts. I will post the HPT logs if it will help.
Last edited by 2xLS1; Feb 23, 2008 at 07:12 PM. Reason: Clarify last line
may help may not...idk i ran my car at the track with a 3"y into a cutout,then went to a true daul x pipe setup with 1 chambers dumped....car slowed down....id bet its in the exhaust...my car has a y back on it now....
Hey fellas, this is my car that 2xLS1 tunned on today.. He's tunned plenty of cars & does a great job with great results, knows his ****.. So please, no tunner bashing if that's what you're thinking about replying with, cause I'm 100% confident it's not in the tune.. I just went back & looked at the details on the mufflers I'm running & they clearly say for applications up to 325hp, didn't catch that when I put them on.. Not sure if it's the cause for the below average dyno#'s of a built h/c car, but it definitely seems possible.. By the way the exhaust from the lt's back consists of 3" into the h-pipe & from the h is 2.5" pipe into 2.5" Mac flowpath mufflers.. I'm gonna put my set of 2 chamber race series flowmasters & x-pipe back on, as well as making the rest of the exhaust 3"... Maybe it will free up the restriction, maybe not.. Or could it possibly just be the result of a stingy dyno? The graph he posted is sae, the std #'s were 384rwhp/364rwtq.. I try not to get to hung up on dyno #'s as they never really tell the tale like mph at the track does, which I have not yet taken it to.. But these #'s do seem pretty low for a 6spd h/c car with full bolt on's, but at the same time the car feels really strong on the street & that's what has us kinda baffled.. Please feel free to chime in with any comments or suggestions, thanks guys!
-Mike
-Mike
Last edited by MM98; Feb 23, 2008 at 06:31 PM.
Yeah the graph is smooth as it can be & there is 0 knock retard throughout the pulls.. Everything in the hpt logs check out as well, except for the wall it looks like it's hitting at 6k on the dyno sheet.. Tunning was done on a in-ground dynojet.
-Mike
-Mike
Last edited by MM98; Feb 25, 2008 at 06:37 PM.
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Thread Starter
Joined: Nov 2001
Posts: 5,649
Likes: 9
From: Warr Acres, OK
I had Mike jump in the car and mash the gas while I checked the TB after the 1st pull even though the log showed 100%. I didn't check for the cam hitting anything but it definately would not open any further by hand. I've neve heard of having to cut the cam but this was is not the Fast 90 TB. Mike, what brand is it again?
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mac flow path mufflers shouldnt be that much of a issue i had them on my mustang at 435/517rwhp/tq mine were 2.5 header back and my dads got them at 505/440 on his stang and he has headers 2.5xpipe and 3in catback.
Weird, good timing no KR, AFR right on. Nice flat hp curve.Did you check fuel pressure, the hp seems too low to be running out of fuel pump but it's a possibilty. I used to run a 228/230 XER and was 420+ with AS 5.3 heads and with a 9". The 4.10's are taking some hp maybe 5-8?
Wouldn't the graph show a lean condition if I was runnning out of fuel up top & possibly some knock retard?? The pump is the factory unit with 145K on it.. The car feels good on the street, but when it was on the dyno in 4th at about 6.2k, it kinda sounded like it was taking a bit longer to get to the 6.8k rev limiter.. Kinda like something was holding it back.. Dunno, gonna redo the exhaust AGAIN & take it to the dyno where my tunner does all of his tunning on.
Wouldn't the graph show a lean condition if I was runnning out of fuel up top & possibly some knock retard?? The pump is the factory unit with 145K on it.. The car feels good on the street, but when it was on the dyno in 4th at about 6.2k, it kinda sounded like it was taking a bit longer to get to the 6.8k rev limiter.. Kinda like something was holding it back.. Dunno, gonna redo the exhaust AGAIN & take it to the dyno where my tunner does all of his tunning on.
I was running out of fuel (Stock TPI) pump and my afr graph wasn't showing a lean condition. Might want to upgrade to a walbro 255 with a h/c car.
Originally Posted by Mazzenger
I cant believe your stock fuel pump is still working.My 98 pump went out when i hit 375rhp. 4.10 chew up a little. Could the dyno read it wrong?
Very doubtful, the car idles & drives perfect.
Last edited by MM98; Feb 25, 2008 at 06:40 PM.
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From: Gateway International Raceway
What combustion chamber size are your heads? What head gasket are you running? Compression ratio?
I doubt the fuel pump is causing this but with that many miles would not hurt to upgrade.
How did you break in the motor? I would do a compression test or a leak down or both.
When you hit the wall at 6000 it seems your cam should pull past 6200 or so, maybe you are running out of air? Do you have an 85mm MAF? Did you get flow numbers on the heads? The intake should not be your problem.
It could be the exhaust I guess, only one way to find that out...take it off and dyno.
I doubt the fuel pump is causing this but with that many miles would not hurt to upgrade.
How did you break in the motor? I would do a compression test or a leak down or both.
When you hit the wall at 6000 it seems your cam should pull past 6200 or so, maybe you are running out of air? Do you have an 85mm MAF? Did you get flow numbers on the heads? The intake should not be your problem.
It could be the exhaust I guess, only one way to find that out...take it off and dyno.
What combustion chamber size are your heads? What head gasket are you running? Compression ratio?
I doubt the fuel pump is causing this but with that many miles would not hurt to upgrade.
How did you break in the motor? I would do a compression test or a leak down or both.
When you hit the wall at 6000 it seems your cam should pull past 6200 or so, maybe you are running out of air? Do you have an 85mm MAF? Did you get flow numbers on the heads? The intake should not be your problem.
It could be the exhaust I guess, only one way to find that out...take it off and dyno.
I doubt the fuel pump is causing this but with that many miles would not hurt to upgrade.
How did you break in the motor? I would do a compression test or a leak down or both.
When you hit the wall at 6000 it seems your cam should pull past 6200 or so, maybe you are running out of air? Do you have an 85mm MAF? Did you get flow numbers on the heads? The intake should not be your problem.
It could be the exhaust I guess, only one way to find that out...take it off and dyno.
Last edited by MM98; Feb 25, 2008 at 08:01 PM.
i don't think it is the exhaust. the rating is 325 hp each,correct ? with a 228r cam on a 112+2,stock 90/90, tea 5.3 heads (57cc) through a hooker catback i made 436/402. before going through the trouble of changing out exhaust setups again i would find another dyno and make a few pulls.unless the dyno is very stengy your setup should put down 420+
i agree with others, you may need a fuel pump also.
i agree with others, you may need a fuel pump also.
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From: Gateway International Raceway
I still think a compression test is in order. You will probably get around 190psi or so (just a guess) Tony Mamo is good at calculating that with respect to the cam. Compression test is too easy not to do. I am sure that TSP degreed the cam when they installed it...but it never hurts to check it.
BTW...sorry I missed the 85mm MAF in the first post.