Carputing LT1/4 edit
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: Carputing LT1/4 edit (1996man)
how hard is it to up the timing on LT4s? wouldnt that give you quite a bit more power? i understand if it gets to hgihg you will need a higher octane but it would be kinda nice to be able to do that at the track
Unfortunately the aftermarket has done a great job of convincing everyone that a quick little program change nets a bunch of hp. Ain't that easy. The stock programming is damn good on the later C4s, especially the '96s.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Re: Carputing LT1/4 edit (96GS#007)
:iagree: The tool really works great when you start making mods to the engine. That is when you will see the big numbers. As GS#007 states, the GM calibrations are pretty spot on from GM, and its one reason our Vettes has 2 knock sensors versus the F bodys single knock sensors. They may have changed this for 96 and 97 model year F bodies but prior to that they had single sensors.
I remember way back when EFI High Performance chips first started coming around and the what the ads said. I guess it sorta stuck on us and really its a big marketing thing with them, and its made people like Hyper-Crap and JET stinking rich as well! I did a read on a so called stage 3 JET chip once on a L98 car, all they did was bump the timing maps across the board 3 degrees! And it cost the guy $350! Heck he could have bumped the base timing up 3 degrees and got the same result, and even if he purchased a Snap On Distributor wrench (not needed) to loosen the distributor, and a manual to tell him how to do it, he would have been money ahead!
I remember way back when EFI High Performance chips first started coming around and the what the ads said. I guess it sorta stuck on us and really its a big marketing thing with them, and its made people like Hyper-Crap and JET stinking rich as well! I did a read on a so called stage 3 JET chip once on a L98 car, all they did was bump the timing maps across the board 3 degrees! And it cost the guy $350! Heck he could have bumped the base timing up 3 degrees and got the same result, and even if he purchased a Snap On Distributor wrench (not needed) to loosen the distributor, and a manual to tell him how to do it, he would have been money ahead!
Race Director
Joined: Oct 2000
Posts: 14,063
Likes: 1,166
From: N. Alabama
Re: Carputing LT1/4 edit (96GS#007)
LT4 programming is spot on! On the dyno, using an A/F ration sensor, I found that with the stock 48MM TB, hot cam, headers, slp claw intake, random cats I got an A/F of 12 something (not really good). However, with only a change to 52MM TB the ratio went to a near perfect 13.5 throughout the entire RPM range using stock programming. I do need to get the idle up since it is way too low and rough with the 52. Oh yeah, I got 340.8 HP and 334.5 torque. :thumbs:
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: Carputing LT1/4 edit (southern_son)
LT4 programming is spot on! On the dyno, using an A/F ration sensor, I found that with the stock 48MM TB, hot cam, headers, slp claw intake, random cats I got an A/F of 12 something (not really good). However, with only a change to 52MM TB the ratio went to a near perfect 13.5 throughout the entire RPM range using stock programming. I do need to get the idle up since it is way too low and rough with the 52. Oh yeah, I got 340.8 HP and 334.5 torque. :thumbs:
Race Director
Joined: Oct 2000
Posts: 14,063
Likes: 1,166
From: N. Alabama
Re: Carputing LT1/4 edit (96GS#007)
How so on the lean by .5 point? Does the probe in the tail pipe not read accurately? And by what law of physics does the Dynojet probe read off by a given .5 point?
Race Director
Joined: Apr 2000
Posts: 15,344
Likes: 4,009
From: Texas
Re: Carputing LT1/4 edit (southern_son)
How so on the lean by .5 point? Does the probe in the tail pipe not read accurately? And by what law of physics does the Dynojet probe read off by a given .5 point?
Furthermore as you pointed out above, a single probe is used to measure the AFR. This measurement is therefore the average of 4 cylinders on one side of the car. An H or X pipe will affect that further. By definition, some cylinders will be leaner than others. Cylinder scavaging, intake reversion, etc will also affect this. GM addresses this by adjusting the fueling balance on each cylinder. This table is also in LT1 Edit.
One other consideration...A lean mixture is hotter and leads to detonation, especially since tuner programs tend to increase the timing over stock.
Personally I error on the side of caution but hey...it's your money.
Racer
Joined: Apr 2003
Posts: 383
Likes: 0
From: triangle NC
Re: Carputing LT1/4 edit (96GS#007)
I just thought I would add to this thread that I gained over 40 rwhp by having my car tuned on a mustang dyno with lt1 edit. Mods are in my sig. 335rwhp and 328rwtq on a stock head, stock displacement engine. By porting my maf it made the car run quite lean. Adding fuel really helped her. Also if anyone ever has there car tuned on a dyno, the tuner should have wb o2's in each bank in my opinion.
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Race Director
Joined: Oct 2000
Posts: 14,063
Likes: 1,166
From: N. Alabama
Re: Carputing LT1/4 edit (96GS#007)
You know 007, if someone were to take a multi-probe EGT gauge off of an airplane manifold and tap into the header runners then the absolute mixture could be established. However, I find it difficult to fathom THAT much difference between the cylinder temps in the vette as my old carburateur fed continental in my airplane did not display very much difference at all. Of course, I guess I could get a laser temp analyzer focused on it, too. You do bring up an interesting hypothesis but where does this .5 value obtain its validity?
