LT4 LT4 "real" HP

[JimRo]

Good but used thread!! Mine (96CE) only mod is a K&N with an opened air box dyno'ed at 308 rear wheel. This will equate to appx. 368 at crank. I have heard many times that the 330 rating was given so the LT4 would not overshadow the LS1 coming out in 97. The LT4 stock not to mention a few simple mods can easily run with the LS1. The LT4 has the potential to be a real monster.

Jim

 

[boulderlt4]

I have heard many times that the 330 rating was given so the LT4 would not overshadow the LS1 coming out in 97.

Jim

I've also heard that they didn't want to **** off the ZR-1 guys who had just paid up the butt for their cars the year prior!

 

[CKA_Racing]

I've also heard that they didn't want to **** off the ZR-1 guys who had just paid up the butt for their cars the year prior!

I think this comment is way off. The ZR1 is still slightly faster and it's a totally different unique engine. Most ZR1 owners think the ZR1 is above all the others. That's find with me, what ever floats your boat. Just pointing that out because with that kind of thinking it would be hard for the LT4 to get them upset. :L

 

[JAGSFAN]

Horsepower

MY LT4 CONVERTIBLE DYNOED AT 315.7 RWHP WHAT DOES THAT EQUATE TO IN HORSEPOWER AT THE CRANK .iN 4TH ITS TOP SPEED WAS 148 SO HOW FAST WILL IT GO?

 

[6 Shooter]

Top speed is achieved in 5th gear, in the 170's . . .

MY LT4 CONVERTIBLE DYNOED AT 315.7 RWHP WHAT DOES THAT EQUATE TO IN HORSEPOWER AT THE CRANK .iN 4TH ITS TOP SPEED WAS 148 SO HOW FAST WILL IT GO?

Stock LT4 Top Speed Thread

 

[wx briefer]

If 'auto performance test lab' in Atlanta, Ga. dynoed a stock LT4 at 375 rWHP, they need to check their equipment!!!! End of story.


Of course, during good atomospheric conditions (high pressure and cold temps) my LT4 did 363 RWHP. This is not an atmospheric corrected reading. One must use a correction factor to be reasonable in comparisons.

 

[LT4BUD]

Been a long time since I have seen a from the factory stock LT4......ones with simple bolt on mods,,,cat-backs, K&N filters, etc are usually right around 300 hp at the wheels....mine went 295-299 on its 3 pulls.....didn't make the magic 300

so....well biggers mods....now 365-370.....more to come

 

[Hib Halverson]

There's no question that there's plenty of urban legend about LT4s being underrated by GM.

There seems to be a fair amount of information here that tends to support that idea, however, none of the dyno numbers listed are acompanyed by the correction factor which is a critical issue. Rear wheel power and torque numbers must be expressed in SAE-corrected form to be relevant in a conversion to flywheel power/torque. Also, the conversion is an approximation as the conversion factor is an average at best. For C4 manuals, it's 18%. Lastly, no one's posting where these engines are making peak power.

One number I certainly question is the one just above. Was that 360 hp on a chassis dyno?

Then there's the LT4 with the Hot Cam and a Corsa exhaust that's only doing 314. Again, is that a chassis dyno or an engine dyno number?

 

[LT4BUD]

Lastly, no one's posting where these engines are making peak power.

When mine was "near stock"...the 295-299rwhp was right at 5800rpm, in agreement with GM's max hp rpm

 

[Roadster Guy]

Hib should to a Print or Internet article on the LT4!!!

"There's no question that there's plenty of urban legend about LT4s being underrated by GM."

Hib, I enjoy your articles. Here's a suggestion for a new one. There are many circumstantial bits of evidence and numerous claims and dyno printouts concerning the LT4 lurking about on the net. Everyone has seen something on this subject somewhere. And it has become accepted fact that many LT4's produce more HP and torque than GM claimed at the time.

But I have never actually seen a magazine article or a section in a Corvette book for that matter that deals head on with the issue of actual stock LT4 HP and Torque. I have only seen numerous links on the net. Mostly, these links are dyno test claims and as you asked above, are they accurate and adjusted correctly? Most engines that were under-rated by GM are discussed in magazines and Corvette books. To my knowledge not the LT4.

I think you should do an article with background and incorporating controlled dyno tests on the LT4 engine. I think it is an interesting subject and it may consolidate a number of theories and finally substantiate or denouce most claims. You could title it something like this: "The LT4, A Legend in the Making or just another Urban Legend?"

Anyone else think Hib should take it on?

 

[wx briefer]

Hear! Hear! I agree!


And not to appear sarcastic in my enthusiasm, but also include how LT1 edit is used to increase HP. More specifically, in what areas does the computer on the '96 OBD2 take its que? I am always looking for another tweak or two. ;-)

 

[jcs44]

Well, after all the responses to this post and some research on other sites, it appears that an average stock LT4 can be expected to deliver about 300rwhp and and a little more than 300rwt. This equates roughly to 355hp at the crank and 360 ftlb torque. Not too shabby for an engine rated at 330/340 (hp/tq).

Thanks for all your replies. JCS44

 

[code5coupe]

There seems to be a fair amount of information here that tends to support that idea, however, none of the dyno numbers listed are acompanyed by the correction factor which is a critical issue. Rear wheel power and torque numbers must be expressed in SAE-corrected form to be relevant in a conversion to flywheel power/torque. Also, the conversion is an approximation as the conversion factor is an average at best. For C4 manuals, it's 18%. Lastly, no one's posting where these engines are making peak power.

I think that is the big overlooked point; all the hp numbers being "proven" on a chassis dyno are just educated guesses.
Until someone puts about 100 fresh LT4's on a engine dyno (and that will never happen), it is all speculation and a lot of wishful thinking.

As far as the 18% rule goes, I'd like to know where that comes from because I think it is a bit high....I'm guessing (key word) that it's more like 13% drivetrain loss.
Larry