LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

lost low end torque with long tube install

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Old 08-13-2007, 01:09 PM
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lost low end torque with long tube install

When My car was stock it used to break the tires loose if I stomped on it from a dead stop. Now after all my mods especially the headers it wont spin the tires from a stop. Would a tune help me regain some of my low end torque back?
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Old 08-13-2007, 01:28 PM
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I would think that the 2.73s would be your problem, but if you were chirping with 2.73s before the LTs...that's odd. Could be when you were "stock" you had crappy tires that didn't stick. I have heard..not confirmed that some headers are "too open" and don't keep enough backpressure, which can rob you of some low end torque. But I still think you'd chirp with LTs.

When I bought my 96 used, it still had the Goodyear GAs on them...I could spin them all day, and the car was stock. But those tires are far from sticky.

Quickest way to get the chirp back....change to 3.73s in the rear. It'll go nicely with your converter. If that doesn't cure your lack of chirp....check to see if your V8 is really a V6 in disguise.
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Old 08-13-2007, 01:33 PM
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Originally Posted by WestCoast96Z28
I would think that the 2.73s would be your problem, but if you were chirping with 2.73s before the LTs...that's odd. Could be when you were "stock" you had crappy tires that didn't stick. I have heard..not confirmed that some headers are "too open" and don't keep enough backpressure, which can rob you of some low end torque. But I still think you'd chirp with LTs.

When I bought my 96 used, it still had the Goodyear GAs on them...I could spin them all day, and the car was stock. But those tires are far from sticky.

Quickest way to get the chirp back....change to 3.73s in the rear. It'll go nicely with your converter. If that doesn't cure your lack of chirp....check to see if your V8 is really a V6 in disguise.
Or maby it's that famoue 2.1L Lt1 everyone is talking about these days
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Old 08-13-2007, 01:39 PM
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Forget chirping, you can't absolutly roast the tires through first into second with a stall and 3.73 gears something is really wrong You have a 3000 stall, it should easily roast your tires if you "stomp" it. Somethings definatly wrong
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Old 08-13-2007, 02:49 PM
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Check your knock counts; knock counts pull timing causing the car to bog off the line.
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Old 08-13-2007, 04:35 PM
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LTs increase low end.
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Old 08-13-2007, 04:46 PM
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I would suspect you might have a mechanical issue going on that is causing a lack of power.
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Old 08-13-2007, 05:17 PM
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Too bad you don't have a before/after dyno sheet to actually verify this "loss." The only things which really could have changed before and after a header install is false knock which would retard your timing and/or you could have burnt some wires. But I'm going to be honest, when I first did my cam and other bolt ons and still had the 273 gears, it was tricky making the tires spin even from a stop!
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Old 08-13-2007, 05:53 PM
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I think I might try the lt4 knock module, And maybe a mad z28 tune. It has to be timing related because if I use the juice off the line it wont go anywhere it will smoke the tires for as long as I hold down the gas. The other thing that changed is I got better tires, Fuzion zr's maybe that made it a little harder to spin the tires? I can power brake it just fine and burnt the tires its just from a dead stop when I floor it it just goes with no wheel spin. Oh and my power is down due to my high altitude of 6000 feet, And even though the converter is a 3000 stall it only flashes to areound 2400.

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Old 08-13-2007, 07:11 PM
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The LT4 KM made even more KR that the LT1 KM for me.
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Old 08-13-2007, 07:47 PM
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So should I just get a madz28 tune? And skip the lt4 km?
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Old 08-13-2007, 07:49 PM
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Originally Posted by WestCoast96Z28
some headers are "too open" and don't keep enough backpressure, which can rob you of some low end torque.
Faulty information. Back pressure does not increase low end torque. scavaging due to narrow tubing does. That's why you lose low end with big headers.
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Old 08-13-2007, 08:01 PM
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Originally Posted by WestCoast96Z28
I have heard..not confirmed that some headers are "too open" and don't keep enough backpressure, which can rob you of some low end torque. But I still think you'd chirp with LTs.

engines do not need backpressure!!!

end of story. done never mention it again.



sorry man, it's just a pet peave of mine. i hate that myth







pyro, you seem to have similar mods as me, 2.73's, 125 shot (mine's wet) stall (mine's 2800), long tubes, exhaust (true duals here).

if you're running nitrous like that, i would suggest running autolite 103's instead of hte 104's. the cooler heat range will potentially save your engine.

i also installed my headers and stall recently. i can't break my tires loose like i used to either. but i have also gotten 275's falkens now versus the bald 245 kumho's i had on there before. so i'm assuming that's the difference


what has your car run before. i'm interested in finding out who has fast 2.73 cars. i ran my 11.9 on stock manifolds and stock stall too. havent been out to the track after these mods. hoping for 11.6's with a lower 1.5 60' maybe even a high 1.4
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Old 08-13-2007, 09:04 PM
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I have never had this car at the track. I plan on going this Friday just to see what she will do. It probly wont be much concidering my altitude. My next mod will be a madz28 tune. I believe I am getting kr from the long tubes and offroad exhaust, The tune should take care of that.
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Old 08-14-2007, 08:25 AM
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i got a pcmforless tune on mine. although more for the nitrous, my gas mileage seems to have gone up a bit too.
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