dyno'd today..
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
dyno'd today..
not to happy about it..
mods. lt4 355, comp 280xfi, shorty headers, 52mm tb, no cats 3in slp exhaust, 30# svo's..
well it only put down 287hp/277tq? does that seem right.. no spiking or sounds of it running wrong. just ran a 12.7@111.9 with a 1.99 60 2 weeks ago? i would have thought it would be in the 330-340rwhp range? and i would think i would notice a loss in hp.. dunno.
mods. lt4 355, comp 280xfi, shorty headers, 52mm tb, no cats 3in slp exhaust, 30# svo's..
well it only put down 287hp/277tq? does that seem right.. no spiking or sounds of it running wrong. just ran a 12.7@111.9 with a 1.99 60 2 weeks ago? i would have thought it would be in the 330-340rwhp range? and i would think i would notice a loss in hp.. dunno.
Le Mans Master
Joined: Apr 2000
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From: DrunkDefender
CI 1-2-3-4-5-6-7-8 Veteran
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St. Jude Donor '07-'10
236 241 .552 .547 113° with 1.6 rockers, is this the cam you have?
You should be making alot more power but more than that your trap speed seems very low. I trap 115mph with less mods and a smaller cam (the hotcam). What dyno was this done on? A mustang dyno perhaps? I know that the operator of a mustang dyno can input some variables that will make the numbers go up or down if they dont know what they are doing. FWIW, before I put headers on mine I put down 301rwhp on a mustang dyno.
I'm curious about the rest of your motor though, what compresion ratio, heads ported? Valvetrain? Who tuned it etc etc. What were your shift points and can you post a dyno graph?
Just my opinion but if you have no cats why not go ahead and run some longtubes? I had a catback with stock manifolds and went 112mph. With longtubes I went 115mph with no other changes.
You should be making alot more power but more than that your trap speed seems very low. I trap 115mph with less mods and a smaller cam (the hotcam). What dyno was this done on? A mustang dyno perhaps? I know that the operator of a mustang dyno can input some variables that will make the numbers go up or down if they dont know what they are doing. FWIW, before I put headers on mine I put down 301rwhp on a mustang dyno.
I'm curious about the rest of your motor though, what compresion ratio, heads ported? Valvetrain? Who tuned it etc etc. What were your shift points and can you post a dyno graph?
Just my opinion but if you have no cats why not go ahead and run some longtubes? I had a catback with stock manifolds and went 112mph. With longtubes I went 115mph with no other changes.
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
i just got a set of em longtubes in the mail two days ago.. and my cam is a 230/236 with .576/.571 lift but regardless.. its 10.4:1 compression cause went to forged pistons and the heads and intake are untouched as far as ported.. i have 10308 vavle springs and comp pro mags and a pcm for less tune. i have put maybe 50 miles on the car since its been to the drag strip and there is no difference in how the runs. i can post a graph later.. there is no afr graph though. but it was puffing bits of black smoke here and there as any car does. so i know it wasn't too rich or too lean at any point. i know the shorties are a big cork but i would think it would have dynod more than that cause i have beat cars that have dyno'd comparable numbers to their 1/4 mile times that were higher numbers than that. and have beat ls2 gtos at the dragstrip consistantly, granted tehy are heavier but its a comparison. btw it was a mobile dynojet. i will have better times this weekend cause i a getting slicks.
Melting Slicks
Joined: Apr 2007
Posts: 2,616
Likes: 111
Well, I don't know but your trap speeds are suggesting a little more than the dyno is giving credit; trap speeds on the strip (1/4 mile) are the true measure of performance in my opinion....my 355 is trapping 111-112 but my tune is off and is running pig rich at WOT........I have not had a dyno run/tune since the miniram install...look at my mods.....
Oh BTW.....that trap was before the air pump delete too........I'm not sure how that will improve things, but........FWIW
Oh BTW.....that trap was before the air pump delete too........I'm not sure how that will improve things, but........FWIW
Last edited by 856SPEED; Jun 1, 2008 at 12:23 PM.
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Race Director
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From: O'Fallon Missouri
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
another car dyno'd consistent with what it has previously dyno'd so i don't know. about the detonation.. it was small amounts of black smoke and if it were detonating wouldn't it have showed on the graph?
Le Mans Master
Joined: Feb 1999
Posts: 9,916
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From: South Carolina
St. Jude Donor '03 & '05
I think some datalogging is in order here. This is a common camshaft for pcmforless to tune, as I have a very similiar one in my 396LT1, 425rwhp.
The timing curves are probably close, and I run 11.1to1 comp, and LT's with an auto.
Puffs of black smoke do indicate running lean/detonating and the engine compensating.
I had this happen on a dyno and it turned out to be a loose O2 sensor wire. No check engine light or anything and it was intermittent, and dropped my rwhp to 365!!!
So, do a thorough look over, and check your engine at night with no lights to see if you can see if the plugs and wires are causing little sparks, or anything to verify no problems.
LT4 engines use OBD2 and they are very sensitive to misfires.
Ans check that everything is tight, O2 sensors, plugs, injector wires on correct, anything.
Just my 2 cents.
The timing curves are probably close, and I run 11.1to1 comp, and LT's with an auto.
Puffs of black smoke do indicate running lean/detonating and the engine compensating.
I had this happen on a dyno and it turned out to be a loose O2 sensor wire. No check engine light or anything and it was intermittent, and dropped my rwhp to 365!!!
So, do a thorough look over, and check your engine at night with no lights to see if you can see if the plugs and wires are causing little sparks, or anything to verify no problems.
LT4 engines use OBD2 and they are very sensitive to misfires.
Ans check that everything is tight, O2 sensors, plugs, injector wires on correct, anything.
Just my 2 cents.
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
this has run the same since the day i put it together. i have rolled raced a 320whp car that i beat and recently raced a c6 and was dead even.. i had the crank angle sensor tuned off so if it is misfiring there is no way of detecting, just knock counts. i will have to plug it in to see if i can find anything out. but i have felt no loss of any sort. car sounds fine and runs strong. on a 100 shot i have literally ran off from an over 415+whp srt4 on 21#'s with a 57 trim from a roll. there is no way on earth that i would have beat these cars with 287rwhp as a baseline. i seriously think that the guy wasn't pressing the pedal down all the way.
Drifting
Joined: May 2005
Posts: 1,370
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From: Raleigh NC
Other than the shorty headers, you should have close to the same setup as me and Dr. Evil. Mine made 354 on the dyno, but it also traps 115 to 117 with an occasional 118. Sounds like you need a dyno tune!
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
There have been 2 different people on this forum that have had the same problem. Both of them turned out to be the timing chain was installed 1 tooth off. They both seemed to run fine but were way down on hp.
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
i know. like i said i got a set of EM long tubes in the mail that still need to be put on and the reason i went with them is because of how fast your car was going with them. i am already in the process of building a 383 for it and it won't be getting the long tubes with this motor.. i have only gone the the drag strip with this car 2 times so it was alot of learning. with slicks i should net much better results cause i can't come out of the hole with anything more then 2000rpms with my current tires.. with the slicks i will be able to really launch it and get the numbers it should be getting. i will be getting a dyno tune with the next setup for sure because that number is an embaressment and a dissapointment considering all the work that is done to the car was done by myself. and to have the dyno guy, not knowing one spec about my car, tell me that that number is about right for the car and that the dyno can't tell that its a corvette, i took everything in me to not hand him his teeth in a cup.
Race Director
Joined: Apr 2000
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From: Texas
What kind of dyno? If it was a Dynojet dyno, you're way low. If it was a Mustang dyno, you're right on the money.
edit: Never mind, just saw it was a mobile Dynojet. Looks like the dyno was miscalibrated.
edit: Never mind, just saw it was a mobile Dynojet. Looks like the dyno was miscalibrated.
Last edited by 96GS#007; Jun 1, 2008 at 08:43 PM.