Tom400CFI

With a '91 L98 stick shift car, there is one rear axle ration option. Neither 2.59 nor 3.43 are it.



You enter driver "skill" and suddenly there is no limit to the range of possible times. The OP asked what the CAR can do. So to eliminate "Driver skill", which ranges from guys like Evan Smith, Jamie Furman and Ranger...to the guy that launches at the drag track in reverse...we look at what the best results are from that CAR, and then we can see what the CAR can do. When we do this, we typically try to examine a car as close or exactly like the one being asked about; a '92 LT1 stick. We don't typically go looking for cars with different engines and then try to extrapolate data from something with 55 less hp and apply it to something else.


We're talking about the CAR..what the CAR can do. Who said it was "fast"? What does that mean, anyway? I bought my C4 b/c it was fun.


'70 was an LT-1, '92 is and LT1. Here is the LT-1 350 vs. LT1 350 vs. L98 350 comparison. The LT1 wins that shootout.

ddahlgren

Are those numbers corrected or not? They are so close to published numbers that I would think corrected. I have run a 1970 LT-1 on a dyno and it made a good deal more than 300 hp. stock. It seems hard to believe they were 50 hp. wrong and in the ZR1 trim they were rated at 370 hp. and no idea what got them there.

1stVetteFinally

The ZR1 didn't have a LT1, it had a LT5. While the LT5 may have been a 350 CID V8, that was about the only things it had in common with the LT1.

http://www.zr1netregistry.com/Inform...gineSpecs.aspx

ddahlgren

Have been comparing C3 lt 1 vs. C4 lt1 and yes there was a C3 ZR1
http://www.corvetteblogger.com/2008/...-Corvette-ZR1/

johno504

the LT4 was tested at 4.9, don't think any stock lt1 will beat that.

Tom400CFI

Say....WHAT?? I have no idea what you're saying there. Do you? Where did the "ZR1 (ZR-1?) come from in this conversation?

I'm sure that you DID see more than 300 hp on a dyno w/an LT-1....just like you would also "see more than", if you put an LT1 on a dyno with open headers, no exhaust and no accessories.

It's weird to me that this needs explaining. The graph above was apparently done using "Net HP" rating; all accessories and stock type exhaust in place. How can we determine this? Well, the '70 LT-1 was originally rated at ~370 hp...yet in the graph it made ~300. The LT1 was rated at 300 net hp and it made 3-low teens in that graph -pretty close to it's net rating.


Now let us observe another test...this one would be more like the one that you must have ran where you saw "good deal more than 300 hp. stock." That would be a GROSS hp measurement with all accessories removed, open headers, no exhaust and optimized conditions, fuel and tune. Under these conditions, you'll see that the LT-1 and the LT1 both returned just about 350 hp, in THIS TEST

Bottom line? The '70 LT-1 and the '92 LT1 both made about the same power, how ever you measure it.

ddahlgren

It came from the fact they also made a 370 hp (claimed) 350 between 70 and 72 that was a gen1 w/carb etc and came in a ZR1 C3 option. If the C4 LT1 has an electric water pump and the only electrical load is ignition injectors and water pump the A/C is off to rack for the power steering pump to drive I fail to see more than a couple of hp. of accessory load. We never ran a power steering pump or A/C unit on the dyno alternator was generally not connected with a carb no fan but did have the water pump connected. The reason I as about correction factors used is the date on the bottom of the sheet is 1990. A C3 would of had cast iron exhaust manifolds and doubt if GM is so silly to test without them. We always asked for the exhaust manifolds that fit the chassis and usually not nearly enough room for a complete exhaust system. But that is not 50 to 70 hp either. The difference between advertised and listed on that sheet is between 14 and 20 % and that is a pile that exhaust or accessory does not explain away.

GREGGPENN

I understand what you are saying and wonder the same thing. Best I can figure is GM is using Trump math to promote what they want to.

For the two modern cars (engines), you'd have to think they were posting dyno numbers with accessories mounted. If they used stock manifolds, we also know 70s was way worse...handicapping their performance.

Even if GM "corrected" 1970's numbers (as shown here) to modern numbers, how did the peak change? And, why IS IT so much lower than expected. IIRC, 15% off pre-corrected HP numbers would drop the 1970 to something like 317hp @ 6k rpms. The graph isn't representative of either (peak location or amount).

I've often complained about these GM charts and this one is no exception.

Tom400CFI

Guys. THINK. See the independant, third party test I linked above? Where both engines were w/in 3 hp of each other? How can that be? If GM was TRUMPing up numbers, than how does the SuperChevy test come out with such similar results to the GM test?(other then the displacement of numbers created by the differing measuring methods of net vs. gross)


C4 doesn't have an electric water pump. It has a gear driven water pump, a belt driven PS pump, alternator and AC compressor pulley. It also has cast manifolds, cats, dual exhaust with three mufflers and factory tune. Saddled with that, it makes ~300 hp at the crank. Remove that (minus the water pump), instal LT headers and an optimized tune, and you get 350 hp at the crank...or at least Super Chevy did. There is your C4 diff between NET and GROSS hp.


Right. That is what we call, "Gross hp". You had to run the water pump b/c you can't over heat the engine. And you probably didn't have an electric sitting on the shelf.



This is undecipherable. What does 1990 have to do with C3 exhaust manifolds?? Where do you get "advertised" and "listed on that sheet"? I think you're talking "Gross" vs. "Net"....but it's hard to tell. GM has PLENTY of room in their dyno cell for full exhausts; it's how they dyno every engine RPO that they produce. It's really hard to tell WTF you're saying, here.


If you take a '70, 370 hp LT-1 and install factory '70 LT-1 manifolds, full exhaust, alt, smog, FAN, and tune, you're going to end up w/around 300 hp at the crank...about what GM measured in that graph above.

Dude...you wondered earlier:
I promptly slapped up a graph for you... FROM GM...from the horses mouth and now you need to argue about that too? While confusing yourself with net vs. gross hp ratings? Yikes.
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Need more evidence that both motors make the same power? I think you do. HERE IS A TEST comparing a Porsche 911 and a '70 LT-1 'Vette. Look about 1/2 way down at the 1/4 mile results:
Forget about the Porsche, and ignore the ET; we know that was hampered by tires of the day LOOK AT THE TRAP! 101.
And
http://www.facebook.com/HotRodHarrys...51254903213160
...is another data point, again just under 1/2 way down...
....I trap 101 here in UT (elevation) in a '92 LT1 which is a heavier car. How can that be, folks? If they aren't about the same hp...then how can that be?


.

QCVette

Below are a couple of pages from GM 1992 advertising brochures.

One states that the LT1 has "the highest net horsepower for any production-car small block in Chevy history".

The other states it has a 50 hp increase from '91 and more power than the '70 LT1.

GREGGPENN

I have to apologize. I was on my way out the door and spent a couple minutes looking at the graph and typing my prior reply. Looking again, I understand the graph (better). It's a bit surprising the LT-1's net is almost 20% less than gross but I can live with that. The OTHER test linked seemed too much of an approximation. But, that's OK too.

I can easily accept that a modern powerplant will outperform the one from the past....though I'm also surprised at the duration used in 1970. Wow! Can't say I ever knew that!

I guess the other question is how dahlgren could have seen over 300rwhp from an engine that nets 300 on an engine dyno? Must not have been stock! My belief in that statement was one of the reasons I had trouble with the graph. Another reason was the day I drove both an LT1/L98 (back in 1998). The graph at the top of this page shows an LT1 having 90hp more than an L98 above 5k rpms. After adding 100hp to my L98, it's SUPER obvious how much more powerful it is now. The day I drove both (stock), they didn't seem that much different....though I was new to Corvettes. I may not have gone much above 5k rpms but I have to think I hit the 4-5k rpm range.

I dunno....Maybe I did the "power" runs in 2nd gear?

On the opposite side of the fence, after I owned the L98 for a few years, it started to feel like a dog in 3rd gear. That's why it's a 383 now. The closest I came to a 70 Corvette was my 68 GTO. IIRC, I think it was rated at 350 gross hp.

I'll say this though.... The other BIG reason I have a 383 now is I ran my buddies Acura TL back in 2007. From a stoplight, it wasn't a contest. HOWEVER -- on the hwy -- I couldn't pull away from it.

Seems like a car with 90 MORE HP COULD.... Awww....Nevermind!

ddahlgren

I never said it was rear wheel power. I said dyno. A chassis dyno is a vehicle dyno as it takes into account everything in the system including the engine. The downside side is a tire change will change rwp.

This sort of blows the graph away
https://en.wikipedia.org/wiki/Chevrolet_LT-1
If these were done back to back the thing it would imply is the correction factors would use the same system and they would use similar exhaust systems.
This is what I would have suspected to be true.
The only thing I would take note of is camshaft design changed radically in the 20 years from 1970 to 1992 and it is hard to compare a roller to a flat tappet due to rate of lift.

Tom400CFI

Wow. This shouldn't be this difficult. Are you masquerading as "Phoenix'97" now?

No one said a THING about chassis dyne's until you just brought it up. No one had talked about chassis dynos. What he HAVE talked about is NET hp vs. GROSS hp. Are you aware of the difference between the two?



How does that "blow the graph away"??? The graph absolutely does no such thing. The hp rating listed in the link is GM's GROSS hp rating. The graph would have been measured using NET hp rating. Are you aware of the difference between the two?



Cam shaft design is in NO WAY, going to affect how we measure hp. How we strap an engine to a dyno and measure it's output. It may affect the torque and power output of the engine (as does heads, intake exhaust and every other component in an engine)...but it doesn't change the method or accuracy of our measurements.

Tom400CFI

Thank you for actually looking at the graph and the other data, and THINKING. That simple step is too much for most posters, unfortunately, so I appreciate that you carefully reviewed it all again.

How did dahlgren see over 300rwhp from an engine that nets 300 on an engine dyno? Easy. I already explained that above; GUYS....NET vs. GROSS. O.K.? NET vs. GROSS. The "legendary 1970 370hp LT-1" that we are talking about, was measured in GROSS hp. GM measured it back in '69 on an engine dyno, with:
*Open headers
*No smog pump
*No alternator
*No fan
*No air filter/housing and in fact, likely a velocity stack on the carb
*Likely some kind of under drive pulley on the water pump.
*Optimized tune and I've heard possibly with high octane fuel.
^GROSS hp, people. GROSS. That's how it was done 'back in the day'.


We don't do it that way anymore. Today we measure the engine hp, on an engine dyno (not a chassis dyno), and we do it as installed. As installed, people. That means, full exhaust, full intake, all accessories and loads and the same EPA cert'd tune that will end up in the car, all on 91 octane gas.
^This is NET hp, folks. NET.


SO...the LT-1 in the graph was re-tested by GM in '90, using the NET system; all accessories, exhaust and intake in place...and the result was around 300 hp, in that configuration. And there is your ~70 hp.

As for "The OTHER test linked seemed too much of an approximation"...say WHAT!? That was an actual dyno test of the two engines! How is that an "approximation"? It's not. It's actual measurement of the two engines performance, using the GROSS hp method; no accessories on either engine, open headers etc. Equipped as such, they both produced ~350 hp.


Come on Greg....The SOTP meter? Really? Now THAT is what we call..."too much of an approximation". First, the graph doesn't show a 100 hp diff; it shows ~60 hp diff; hp scale is on the right side of the graph. Second, I don't really want to get into this, but the reason you FEEL the huge diff between you L98 and your 100hp+L98 is that you massively increased tq in your L98, to gain your 100 hp. You feel the tq. When you drove the L98 & LT1 back to back, you feel the tq...which is about the same for both engines. The DIFF, is that in the LT1, the tq doesn't fall (plummet) at 4500 like the L98; it just keeps on going at about the same rate. You don't really "feel" that, so much. The diff in "feel" is that you shift an L98 at 4500-500, you shift an LT1 at 5800. See why the SOTP meter don't mean squat? B/c it don't work! ^This is getting WAY off track, though....


If you still can't get a grip on these two ways of measuring hp, go back to my post above an please have another look at TRAP SPEEDS. TRAP SPEEDS tell the hp story....and the LT-1 and LT1 both trap right around the same speed in similar weight cars.

So let's review what we've got:
*A graph from GM showing about the same hp for the LT-1 and the LT1, measured in NET hp. Maybe you don't "believe GM"? We also have:
*Marketing piece from the LT1 era clearly stating the comparison between the LT-1 and the LT1...but we don't believe GM, right? So:
*A engine dyno shoot out from SuperChevy showing the same hp for the LT-1 and the LT1, measured in GROSS hp. Maybe GM and Super Chev are lying? Well, we also have:
*Trap data, showing that both cars trap right about the same speed -102ish?

What do you think guys? Can you wrap your heads around the fact that the LT-1 and the LT1 produced damn near the same hp yet? But we see different numbers in their original ratings due to the methods used at the time?

856SPEED

R

ddahlgren

Actually post 31 directly mentioned rwhp. Yes they are the same the graph does no show that it shows the LT-1 below the LT1 in al respects. Yes I would easily believe a SALES brochure to make the latest on better. No I am not Phoenix LOL

Every time I see a sales pitch I immediately switch to 'it slices dices peels and even cut a can the slice meat so thin your mother inlaw will never come back'. GM has something to sell Super Chevy has not and there is a difference. What would it matter if the LT-1 had an under drive water pump pulley? That is just conjecture anyway the LT1 has none. Do you think the magazine would bother to hook up anything not needed on either engine and a LT-1 and LT1 both run just fine on 93 octane fuel. Again do you think the magazine would bother to change fuels for 2 simple runs? Nope little chance of that. I did notice the LT-1 was ahead of the LT1 in both torque and hp.

Do you have some dog in the outcome I don't as don't own either one or care to. In all sincerity just show me anything sales related tht the one built 22 years ago is just as good as the new one we are selling so have made 0 progress in 22 years.

Tom400CFI

Sigh....

It's incredible that you don't recognize this, but the new car is better because it matches the performance of the old one, while getting three times better fuel economy, and producing less than one-tenth the emissions. Additionally, it will go right on by 300,000 miles. 1970 wont. Most of that was actually covered in the marketing literature above that you're scoffing at and trying to discredit. Read much?

​​​​​​​
With each post, you show us how little you actually know. In spite of your "racing" background.

​​​​​​​Trap speeds. Any thoughts on that? I am asking a rhetorical question. I don't actually want to know how you could Slaughter that data.

GREGGPENN

Hey guys....Sorry I didn't assume dyno meant engine dyno (in ddalgren's comment specifically). I always assume rollers...though I DID assume the GM graph was an engine dyno comparison....especially considering the numbers! For that graph, I DID look at the scale on the right -- for HP. I'm not THAT dumb! (OK...OK...don't start a poll. LOL!!!)

Anyway...If you extend the L98 hp line to a point under the LT1 peak, you'd been looking at 315/225. That's 90hp using my math. I realize it's not "peak-to-peak", but the difference is bigger than the amount normally attached to the L98=>LT1 upgrade.

I always look at the "area under the curve" which applies BOTH to TQ and HP. When I've objected to GM's graphs it's because they are geared toward HP differences -- which aren't as easy to feel! Right? You said it! Chassis dynos are more "horizontal" in their scale. As such, I relate to what I see/feel better.

Still, I'm surprised I didn't notice that 5krpm HP difference back in the 20th century! Then again, I didn't drive them AFTER reviewing dynos and looking for those differences. I was SO young and dumb...at 40! As for the torque, I guess you made my case for going after torque in a street car!

I'm sorry...shouldn't have said THAT.....j/k.

As for my comment about approximation, I'm referring to the fact (in your link to the HotRod article) it states they built an engine similar to the 1970 Corvette. THAT was the "approximation". They didn't actually use a 1970 Corvette engine. It doesn't bother me or discount the graph (which I admitted looking at incorrectly the first time. Plus, I really DID think ddalgren referred to a roller dyno). My comment about "approximation" just means the graph could have stood alone. It means I would have appreciated a direct comparison better. (I've seen too many articles where I questioned the results....FWIW.)

The only thing I'm left wondering is why GM didn't advertise an LT1 at 315 hp versus 300? I've seen roller dynos of C3's -- which I had compared to my car already. (I also looked at the BBC dynos from back then). Anyway...I was already aware of their "deficiency" compared to newer cars. One has to think owners of newer generations look at ours the same way....which undoubtedly led to the OP's original post.

DGXR

Nowadays a stock LT1 6-speed isn't very competitive for drag racing. It is fast, but lots of other vanilla cars (late models) are also fast. Some Japanese sport sedans will do just as well. Where the C4 shines is in the handling/cornering and in the overall driving experience. It feels like a *real* sports car, low and torquey and very responsive. The steering wheel is thick and the effort is high. This sporty feeling is missing from a lot of later sports cars which feel too insulated (the C5 is included here). Too much cushiness in later models. The C4 is more raw, it's a great driver's car and that is how I enjoy mine the most. I love rolling on the throttle in 4th gear, right from idle... the torque is so strong and so smooth.

93Rubie

I like the general they cannot run 13's nonsense. I have the time slips to prove otherwise.

FYI, my LOADED with options 93 weighs about 3300lbs not sure where 3400 came from.

Also my calculated 0-60 time using my 1/8th mile time and speed according to wallace racing is 4.56 seconds on a 1/4 mile track on street tires. NOT drag radials just decent summer performance tires. So even on a slow day under 5 seconds.