Stock L98 numbers
12-10-2003, 08:31 AM
#16
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Join Date: Apr 1999
Location: Diamondhead, MS
Posts: 467
Originally posted by 90rocz
From what I've seen about the LT1's, most of the improvements were aimed at moving the Peak Power numbers higher in the RPM band. Such as "shorter intake runners", "taller intake ports", "Swirled combustion chambers", and cam timing to help support it. It makes the power band more "Peaky" tho, killing off some low end torque, which isn't a really bad thing in the "traction department".
Some "improvements" tho have been a thorn in the LT1's side, such as the shorter wheel base, engine location, "Optispark, other than the "Blue-Death", it has been know to self-destruct if it spends too much time above 6000 rpm...
The TPI as it's designed maintains a broader more usable power band/torque curve, and that is what I believe accounts for it's ability to compete effectively with LT1's. It's the "Average" power numbers that really moves the car down the road...
I'd love to be able to plug in a Power Programmer to my ROC and mess with fuel, spark and shift parameters tho.
From what I've seen about the LT1's, most of the improvements were aimed at moving the Peak Power numbers higher in the RPM band. Such as "shorter intake runners", "taller intake ports", "Swirled combustion chambers", and cam timing to help support it. It makes the power band more "Peaky" tho, killing off some low end torque, which isn't a really bad thing in the "traction department".
Some "improvements" tho have been a thorn in the LT1's side, such as the shorter wheel base, engine location, "Optispark, other than the "Blue-Death", it has been know to self-destruct if it spends too much time above 6000 rpm...
The TPI as it's designed maintains a broader more usable power band/torque curve, and that is what I believe accounts for it's ability to compete effectively with LT1's. It's the "Average" power numbers that really moves the car down the road...
I'd love to be able to plug in a Power Programmer to my ROC and mess with fuel, spark and shift parameters tho.
12-10-2003, 03:04 PM
#17
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Join Date: Feb 1999
Location: Springfield,OH. U.S.A.
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Nothing I can say about that sheet...but NICE!
Looks like you maybe did just a little PP tuning too??
I usually see the LT1's torque curve start a little lower at 1500 and drop off similar to yours at 4500.
I just said the were more peaky, not extremely peaky...
Yours is not the typical stock LT1 sheets I see, around here anyways. I don't have one here to scan but they're usually a "little" more peaky than that and tend to fall of more on top, stock, due to the factory tuning kinda "fat" on top end.
After leaning out the fuel (PP) on top they usually look a lot more like what you've got..
I'm NOT trashing LT1's, just defending my 'lil TPI....
Here's some Stock L98 numbers, can't get the sheet to work..
2000 271 110
2250 274 119
2500 285 136
2750 294 158
3000 307 173
3250 308 193
3500 312 206
3750 305 214
4000 296 225
4250 287 231
4500 276 235
4750 268 239
5000 248 225
The TPI rpm range is only roughly 500 rpms shorter than you too..
Looks like you maybe did just a little PP tuning too??
I usually see the LT1's torque curve start a little lower at 1500 and drop off similar to yours at 4500.
I just said the were more peaky, not extremely peaky...
Yours is not the typical stock LT1 sheets I see, around here anyways. I don't have one here to scan but they're usually a "little" more peaky than that and tend to fall of more on top, stock, due to the factory tuning kinda "fat" on top end.
After leaning out the fuel (PP) on top they usually look a lot more like what you've got..
I'm NOT trashing LT1's, just defending my 'lil TPI....
Here's some Stock L98 numbers, can't get the sheet to work..
2000 271 110
2250 274 119
2500 285 136
2750 294 158
3000 307 173
3250 308 193
3500 312 206
3750 305 214
4000 296 225
4250 287 231
4500 276 235
4750 268 239
5000 248 225
The TPI rpm range is only roughly 500 rpms shorter than you too..
12-10-2003, 03:17 PM
#18
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Join Date: Feb 1999
Location: Springfield,OH. U.S.A.
Posts: 2,947
Some facinating(sp?) facts, I've been doing more research into my TPI and I remebered once I read it, but had forgotten over the years...
That the TPI was first designed and produced for the L98 Corvette. And in '85 the F-Body engineers raided the Vettes parts bins and installed Vette parts on the LB9 305, thus the TPI Z28 was born!..They also lower the IROC/Z's and installed the fat Vette tires and quick ratio steering gears, among various other parts. Ultimately enabeling the IROC to pull an .92!!! on the skid pad. (A poor man's Vette...)
So the TPI wasn't designed for the 305 as many even I had grown to believe, it came from the Corvette. And for the next years to follow the Corvette got all of the goodies ONE year ahead of the F-Bods, but the F-Bods did get them. And when the Vette went to the C5, mid-mounted tranny, the F-Body actually produced MORE RWHP!!!due to the drivetrain lossed the Vette encurred.
That the TPI was first designed and produced for the L98 Corvette. And in '85 the F-Body engineers raided the Vettes parts bins and installed Vette parts on the LB9 305, thus the TPI Z28 was born!..They also lower the IROC/Z's and installed the fat Vette tires and quick ratio steering gears, among various other parts. Ultimately enabeling the IROC to pull an .92!!! on the skid pad. (A poor man's Vette...)
So the TPI wasn't designed for the 305 as many even I had grown to believe, it came from the Corvette. And for the next years to follow the Corvette got all of the goodies ONE year ahead of the F-Bods, but the F-Bods did get them. And when the Vette went to the C5, mid-mounted tranny, the F-Body actually produced MORE RWHP!!!due to the drivetrain lossed the Vette encurred.
12-10-2003, 05:03 PM
#19
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Join Date: Apr 1999
Location: Diamondhead, MS
Posts: 467
I do think I had a "good" one. That dyno was one day after I was at the track. Ran a 13.50@103. It was the only time I ran it at the track with the stock 3.42 gears.
Most LT1's that I've seen are about 5-10 less HP but the torque is about the same.
What is really amazing is the TPI F-Body came out the same year as the Vette. Usually there is a lag of a year for it to trickle down.
Also, no tuning on my car at that time. If you look at the end of the graph, you'll see how jagged it is. The guy doing the dyno was bouncing off the rev limiter
As an aside, when I had the HPP+ and 4.10 gears, it dynoed almost the same numbers. Again a day after the track, and it went 13.18@104.
Most LT1's that I've seen are about 5-10 less HP but the torque is about the same.
What is really amazing is the TPI F-Body came out the same year as the Vette. Usually there is a lag of a year for it to trickle down.
Also, no tuning on my car at that time. If you look at the end of the graph, you'll see how jagged it is. The guy doing the dyno was bouncing off the rev limiter
As an aside, when I had the HPP+ and 4.10 gears, it dynoed almost the same numbers. Again a day after the track, and it went 13.18@104.
12-10-2003, 05:33 PM
#20
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Join Date: Oct 2003
Location: Was TX, now in Portland, OR
Posts: 537
Originally posted by 90rocz
It makes the power band more "Peaky" tho, killing off some low end torque, which isn't a really bad thing in the "traction department".
The TPI as it's designed maintains a broader more usable power band/torque curve, and that is what I believe accounts for it's ability to compete effectively with LT1's. It's the "Average" power numbers that really moves the car down the road...
It makes the power band more "Peaky" tho, killing off some low end torque, which isn't a really bad thing in the "traction department".
The TPI as it's designed maintains a broader more usable power band/torque curve, and that is what I believe accounts for it's ability to compete effectively with LT1's. It's the "Average" power numbers that really moves the car down the road...
The AVG numbers move the cars, yes, but who uses 2000 rpm when you're racing? No one that I know of. The average torque in your racing rpm range is what moves your car. It's the area under the curve of the rpms you use to race at that is important. Of course low end torque is really fun too, of course. L98s have a little more peak torque than LT1s stock I believe, so they hang real nicely for a while, but they fall off at higher speeds because the L98 has to shift gears sooner than the LT1. Same thing when comparing an LT1 to an LS1. They have slightly less low end tq, but longer top end, so they pull us LT1s at the big end.
Just for comparison's sake, stock LT1s dyno from 240 rwhp ('93) to 265ish rwhp (96-97) bone stock.
12-10-2003, 06:19 PM
#21
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Join Date: Apr 2002
Posts: 908
If someone would host it, i have a graph that might be of considerable interest in this discussion. I have a TON of dyno graphs on my computer from most years of f-bodies, mustangs, imports, etc. After comparing cars with similar setups and those of stock setups i came up with some averages and plotted these. They may not be perfect, but they're pretty good indications of what the general behavior of these engine are. The particular graph i have in mind is one comparing a stock L98 to a stock LT1... no mods at all. You'll see that there is a lot more to that 500rpm difference than what the mind first thinks
To be honest, I'm very skeptical about a stock, unmodded L98 putting down 239rwhp. With cold air induction and full exhaust yes, but not completely stock. I have a number of stock and slightly modded L98 dyno graphs (these are actual graphs, not some engine analyzer/dyno software junk). Not one single stock car pulled more than 220rwhp. The bolt-on cars with stock intakes got closer to 250rwhp. Upgraded runners gained a few horses, mainly in the upper rpms.
One reason why some TPIs hang like they do with the LT1s is that they're about some 3-400lbs lighter.
Not bashing or anything, just curious as to why the big difference between that "stock" L98 and all the other ones i've seen. Just calling it as i see it.
To be honest, I'm very skeptical about a stock, unmodded L98 putting down 239rwhp. With cold air induction and full exhaust yes, but not completely stock. I have a number of stock and slightly modded L98 dyno graphs (these are actual graphs, not some engine analyzer/dyno software junk). Not one single stock car pulled more than 220rwhp. The bolt-on cars with stock intakes got closer to 250rwhp. Upgraded runners gained a few horses, mainly in the upper rpms.
One reason why some TPIs hang like they do with the LT1s is that they're about some 3-400lbs lighter.
Not bashing or anything, just curious as to why the big difference between that "stock" L98 and all the other ones i've seen. Just calling it as i see it.
12-10-2003, 09:21 PM
#22
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Location: Diamondhead, MS
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Originally posted by Fast Caddie
One reason why some TPIs hang like they do with the LT1s is that they're about some 3-400lbs lighter.
One reason why some TPIs hang like they do with the LT1s is that they're about some 3-400lbs lighter.
The TTA has Lexan T-Tops so if I had glass tops, it would be even closer.
12-10-2003, 09:49 PM
#23
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Join Date: Jul 2003
Location: cinci
Posts: 3,772
Originally posted by RobsWS6
I don't think the spread is that much. I know my 96 WS6 Formula weighed 3650 with me in it. And my 89 TTA weighs 3550 with me in it.
The TTA has Lexan T-Tops so if I had glass tops, it would be even closer.
I don't think the spread is that much. I know my 96 WS6 Formula weighed 3650 with me in it. And my 89 TTA weighs 3550 with me in it.
The TTA has Lexan T-Tops so if I had glass tops, it would be even closer.
i'm pretty sure it gained about 100-150 pounds on average or so...which would likely result in about a tenth to 15 hundredths difference in times
12-10-2003, 10:50 PM
#25
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Join Date: Feb 1999
Location: Springfield,OH. U.S.A.
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Fastcaddie, not all L98's came with the same heads, some came with cast iron copies of the L98 Vette heads. I believe that, along with other features like dual cats, and a couple of different cams, stronger tranny cores, even the variances in factory fuel pressures, acounts for the differences. The same reasons some L98's ran "Low" 14's, while most went "mid" 14's...
I listed one of the highest I've seen, b/c it ran times similar to my stock times.
My car weighed 3620lbs with me in it and a 1/4 tank of gas, but my is "ALL" power with A/C...
I listed one of the highest I've seen, b/c it ran times similar to my stock times.
My car weighed 3620lbs with me in it and a 1/4 tank of gas, but my is "ALL" power with A/C...
Last edited by 90rocz; 12-10-2003 at 10:53 PM.
or send me an instant msg on aim, sn: smokin iroc z
12-11-2003, 04:58 PM
#27
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Join Date: Nov 2000
Location: Grandville/ Grand Rapids, Michigan
Posts: 1,003
Originally posted by RobsWS6
I don't think the spread is that much. I know my 96 WS6 Formula weighed 3650 with me in it. And my 89 TTA weighs 3550 with me in it.
The TTA has Lexan T-Tops so if I had glass tops, it would be even closer.
I don't think the spread is that much. I know my 96 WS6 Formula weighed 3650 with me in it. And my 89 TTA weighs 3550 with me in it.
The TTA has Lexan T-Tops so if I had glass tops, it would be even closer.
My Iroc, fully loaded with my stereo system 1/2 tank of gas and me in the drivers seat weighs in at 3705. The stereo system weighs 60ish lbs. So, I'm lookin at about 3650 with me in it. A little closer to 3600 with less gasoline at 8lbs per gallon.
12-11-2003, 09:47 PM
#28
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Join Date: Jun 2003
Location: Just outside of "D-town"
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Originally posted by 90rocz
Fastcaddie, not all L98's came with the same heads, some came with cast iron copies of the L98 Vette heads. I believe that, along with other features like dual cats, and a couple of different cams, stronger tranny cores, even the variances in factory fuel pressures, acounts for the differences. The same reasons some L98's ran "Low" 14's, while most went "mid" 14's...
I listed one of the highest I've seen, b/c it ran times similar to my stock times.
My car weighed 3620lbs with me in it and a 1/4 tank of gas, but my is "ALL" power with A/C...
Fastcaddie, not all L98's came with the same heads, some came with cast iron copies of the L98 Vette heads. I believe that, along with other features like dual cats, and a couple of different cams, stronger tranny cores, even the variances in factory fuel pressures, acounts for the differences. The same reasons some L98's ran "Low" 14's, while most went "mid" 14's...
I listed one of the highest I've seen, b/c it ran times similar to my stock times.
My car weighed 3620lbs with me in it and a 1/4 tank of gas, but my is "ALL" power with A/C...
Most of this is correct so i have to be gentle
...N10 (dual cats) was available as a package...and the the differnce between a L98 running a 14.8 to a 14.0 was as easy as checking a few boxes...the slow L98 were the first year cars and the 88's...with single exhaust and 2.77 gears they were hi 14's...the porkers (GTA's) were probly a little slower..a lightweight formy would be 2 tenths faster or so....with the G92 box checked, youd get N10, J65, JG1, KC4 and most importantly 3.23 gears..this package was the low 14 second cars....then in 91 when SD was introduced and there times picked up 2 tenths average..with G92 they were capable of 14 flats..the fuel pressues only changed slightly when GM went from MAF to SD
12-12-2003, 02:57 AM
#29
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Join Date: Mar 2003
Location: Miami, FL
Posts: 691
u'd be lucky to run those numbers though... our cars don't run exactly the same as they did from factory if they were still stock... a little wear and tear will knock it down a few tenths within 10 to almost 20 years, wouldn't you think? i took my car down to moroso, 1990 iroc-z, fully loaded 350, G92, 3.23 gears... the works, weighing in at 3600 lbs with me in the car and not much gas. what did it run? 15.2 to 14.9... but then, by luck, i cagged a 14.8, and all it had was free ram air and flows. without it i probably ran low to maybe even mid 15's. reason being my cats were clogged and probably so are my fuel injectors. car only had 95,000 miles on it. then i ran a 14.5 with all the crap in my sigs and crappy tires. not to mention that along with our engines being 10-20 years old, so are our tranny's... even when rebuilt, they still aren't the same. i wish i was running low 14's stock though... i guess ill gain the power i used to have when i get new fuel injectors and rebuild my L98... waiting for the flow to put in a 383 or 396 stoker kit on it, though. any way you put it, if you go out and buy yourself a iroc-z/z28, and you run in the 14's, you should be DAMN happy you've gotten that far with a car that's aged. if i were back in 1990 and i bought my car back then, im sure she'd be running low 14's, but since im not, and the owener who had the car before me didnt take care of her, i've gotta do with whatever she's got in her.. which still isnt what she had before when she came from the show room. u'd probably be really disapointed if you bought a stock iroc-z/z28 and thought it would run low 14's... not when your car has aged
