Gross Horsepower LT-5

[mrx86]

Hello Guys.

a question:

OK the Stock 90 ZR-1 have 375 HP.
And the "Gross Horsepower" Rating is for this Engine ???
440 HP or less ?


What do you think?

Bye
Mrx86.

[Kevin]

there's a section in the drivers book and the coffee table book, I think, that talks about this. I don't have either with me right now or i'd be able to answer you. if you have the two books i'm talking about, they're in the owners kit, you can find them yourself. i'm sure someone else can get it to you before I do which will be tomorrow at the earliest

[XfireZ51]

Hello Guys.

a question:

OK the Stock 90 ZR-1 have 375 HP.
And the "Gross Horsepower" Rating is for this Engine ???
440 HP or less ?


What do you think?

Bye
Mrx86.

Are you asking about not SAE CORRECTED? Or gross without accessories?

[1990 quasar blue]

I believe the answer he's looking for is without accessories. If memory serves it's 425 but I'll have to double check.

[ghlkal]

I have the coffee table book here, but I can't find gross numbers (although I may have missed it). It does state 375 SAE net on a number of pages though :)

[mike100]

The SAE numbers seem like a much more practical measure. There was so much going on gaming the system to cheat the insurance companies..or maybe the other way around faking the funk to lure customers with overrated claims.

the 1970 hemi was rated at 425 hp at 5000 rpm (officially), but I heard it made 470hp if you revved it out to 6000 rpm...and probably more than 500 if you put headers on it.

[tomtom72]

Our 375 and then 405 ratings are what used to be called "gross" hp back in the old days of the 60's & early 70's.

The OE's used to rate each type engine without any accessories in a test cell. That was the number they gave to the world at large as how much hp the motor produced. I guess the insurance industry used that number for the risk level of a car???? Anyway there was much skullduggery going on. In 1971 the SAE folks wanted some accessories to be included; by '72 it was agreed that a motor should be tested with all it's accessories in place and with the exhaust manifolds and later CATs in place ( I'm 100% sure about the CATs ) and that hp figure would be called SAE corrected net hp. They were trying to get as close to "as installed" as they could to give a hp figure. I figure that would include W/P, Alt, A.I.R. pump, P/S, exh manifolds, all emissions' controls and programing. Anyway, since 72 all engines are tested in this formula (?) to give apples to apples numbers and no funny stuff.

As an example, since I had one of these, the 70 C3 LT-1 yielded 370 hp @ 4800 rpm; a 71 C3 LT-1 yielded 330 hp @ 4800 rpm; a 72 C3 LT-1 = 255 hp @ same rpm. The only running mechanical changes were larger combustion chamber heads for 71 & 72 vs 70; cams were made a bit milder as time went on proly due to CC size, 64 cc chambers in 70 to 76 cc chambers in 71 & 72. The blocks, pistons & rings & rods and piston top ring to deck measurement at TDC remained the same. Im my 72's owners manual the graphs for hp and T/Q stopped at 4800 rpm unlike our graphs that run out to the real peak rpm points. So I'm guessing that the SAE also eventually required the OE's not play games with the rpm that they used to get a max reading.

:cheers:
Tom

[Kevin]

tom,
I don't believe that's true. http://ateupwithmotor.com/automotive-terms/47-gross-versus-net-horsepower.html

i used to know what the gross rating was since I hung around with classic muscle car guys but I've long since forgot it

[mrx86]

OK

how much have the "90 ZR-1" SAE Gross Horsepower
without accessories now ???


90 LT-5 ZR-1 5.7L Stock:
SAE NET Horsepoer = 375HP
SAE GROSS Horsepower (without accessories) = "unknown spirit"


some specialists say 440 HP.

has not measured?
(measurement method as in 60 years...)



Bye

[Hog]

Gross hp
SAE net 70's
SAE "Certified" Power started with the LS7 in 2006 which is rated at 505hp/470 lb/ft SAE Certified using the J2723 which is a voluntary 3rd party rating in addition to the J1349 rating of Aug 2004.

http://www.sae.org/certifiedpower/details.htm

The 375hp and 405 hp LT5's are rated using SAE net hp, certainly not gross rating methods.

The 92-97 LT1 5.7 had a net raing of 300hp, which was about 377-78 gross hp which made it the highest output SBC in history eclipsing the 375hp fuelie 327 and 370hp LT-1 350.

peace
Hog

[Hib Halverson]

The only gen II LT1 which made 300 SAE net was the version in Corvettes and it was available from 1992-1996 with automatics and from 1992-1995 with manuals. That engine never made "377-78" gross at the flywheel. More like 340-350 on a good day.

The Camaro used a less powerful version (275-hp SAE net) of the Gen II LT1 from 1993-1997. There also was an even milder version (260-hp SAE net) used in the Caprice and Impala of the mid-90s.

The Gen II LT1 was, also, not the most powerful "traditional" (Gen 1/Gen II) SBC. That honor goes to the LT4, used in 1996 manuals. It made 330 SAE net about about 370-380-gross hp.

For the record, on SAE net vs. gross power ratings...

Up until the early 1970s car companies rated engines by measuring their torque output with an engine dynamometer than mathmatically deriving the horsepower.

Engines were tested in a manner which had them making the highest possible power output. They were set-up on the dyno with all accessories except the coolant pump removed. They were run with open exhaust. Prior to the early 1960s they used stock exhaust manifolds and after that, racing exhaust headers. The fuel and spark curves were optimized for highest performance. They were run with no exhaust emissions controls. They were run in high-octane, leaded fuel. The intake air temperature was as cold as possible.

In the early 1970s, all the car companies agreed to abide by a new SAE standard which required them to measure "net power". Once again, the ratings were arrived by measuring torque output on an engine dyno, but the engines were run the same way they were configured when installed in a production vehicle. This meant with all accessories (power steering pump, A/C compressor, alternator, etc) installed and operating along with any exhaust emissions controls the production engine may have used. Full stock exhaust systems were installed. The fuel and spark curves were calibrated to production intent. Unleaded pump gas was used. Intake air temp. was 77°F.

The difference in testing methods could amount to 50-hp.

[mrx86]

Hello Mr. Halverson

do you think the 90 LT5 5.7l have 425 gross hp ?

[Hib Halverson]

Hello Mr. Halverson

do you think the 90 LT5 5.7l have 425 gross hp ?

If the engine was run with no accessories other than the coolant pump, optimized fuel and spark cals, optimized cam timing, 70°F IAT, 180° ECT, on higher octane fuel, with headers and open exhaust, yeah...about 425.

[Dynomite]

Up until the early 1970s car companies rated engines by measuring their torque output with an engine dynamometer then mathmatically deriving the horsepower.


Here ya go for those that are not aware of the math :cheers:

Tech Info - LT5 Horsepower and Torque Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660568)

[Hib Halverson]

Here ya go :cheers:

Tech Info - LT5 Horsepower and Torque Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660568)

Thank you "Dynomite" but I was already aware of the math.

Impressive collection of material you have in that thread on the CF.

[Kevin]

found it.

http://i190.photobucket.com/albums/z181/cigarmanpa/photo-2.jpg

[scottfab]

Well that's "gross".
sorry, couldn't help it.

found it.

http://i190.photobucket.com/albums/z181/cigarmanpa/photo-2.jpg

[tpepmeie]

Don't quote me on this, but I read in an old Legend magazine about the development of the LT5, and believe it was stated they were seeing 445 SAE with open headers on the dyno.

[Kevin]

Don't quote me on this, but I read in an old Legend magazine about the development of the LT5, and believe it was stated they were seeing 445 SAE with open headers on the dyno.

too late, just quoted you

[zr1mom]

The next gen ZR-1if it wasn't killed off would have been 450hp.

[Dynomite]

Thank you "Dynomite" but I was already aware of the math.

Impressive collection of material you have in that thread on the CF.

Thank you.....I appreciate and study ALL of your technical posts and technical references (very well written) :handshak:

I am aware of your familiarity with the math and technology. I provided the information sources (same in this post) for those that are not as familiar and have an interest in additional technical information regarding Horsepower :thumbsup:

Here is some more technical information directly related to LT5 Horsepower. All of which is updated on a continual bases with updates noted at the bottom of each post. ;)

This includes the Signature -Solutions- (http://www.zr1.net/forum/showthread.php?t=16778) with updates noted at the bottom of each post.

Tech Info - LT5 Modifications/Rebuild Tricks (500+hp) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html) (100 Posts)

Tech Info - LT5 Eliminated Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html)
Tech Info - LT5 Added Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html#post1579114180)
Tech Info - LT5 New Rebuild Issues (Lifters and Camshafts) (http://forums.corvetteforum.com/c4-zr-1-discussion/2942622-tech-info-lt5-new-rebuild-zero-compression.html)
Tech Info - LT5 Timing Chain Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/2942674-lt5-tech-info-timing-chain-and-engine-pulses.html)
Tech Info - LT5/ZR-1 Technical Calculations (http://forums.corvetteforum.com/c4-zr-1-discussion/3117790-tech-info-lt5-zr-1-technical-calculations.html#post1581660565)

http://i287.photobucket.com/albums/ll142/dynomite007/LT5/Blingzz.jpg (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html)

[ghlkal]

found it.

Nice catch ... where is this page from?

[Kevin]

Nice catch ... where is this page from?

the small, hard bound, "drivers book" that came in the owners kit.

[Kevin]

The next gen ZR-1if it wasn't killed off would have been 450hp.
i thought i'd heard closer to 500

[Hog]

The only gen II LT1 which made 300 SAE net was the version in Corvettes and it was available from 1992-1996 with automatics and from 1992-1995 with manuals. That engine never made "377-78" gross at the flywheel. More like 340-350 on a good day.

The Camaro used a less powerful version (275-hp SAE net) of the Gen II LT1 from 1993-1997. There also was an even milder version (260-hp SAE net) used in the Caprice and Impala of the mid-90s.

The Gen II LT1 was, also, not the most powerful "traditional" (Gen 1/Gen II) SBC. That honor goes to the LT4, used in 1996 manuals. It made 330 SAE net about about 370-380-gross hp.

.
Obviously I was referring to the 92-96 Y-body Vette LT1, although there isnt much different power productionwise between the F-Body and Y-body LT1(cam, exhaust, air intakes). There were 315hp F-body LT1 engines with optional intakes and exhausts.

You are correct about the LT4 being the highest output GEN I/II engine. The material I was referencing was written in 1994 hence my oversite of the LT4 which was used in the 96 Vettes and the 135 1997 Camaro/Firebirds(which actually use a stock LT1 F-body calibration, for emissions, without the Vette LT4's 6412 rpm rev limit, along with extrude-honed stainless steel exhaust manifolds and balanced and blueprinted longblocks UNLIKE the stock 1996 Y-body LT4's). The LT4 was a great engine, LS1 power in the standard 4" x 3.48" GEN I/II package. 1997 LT4 SS Camaro runs high 12's same as a a stock LS1 equipped 98-02 Camaro, both equipped with the T-56 trans of course.

I respectfully disagree about your LT1 hp assertions.
The 1970 LT-1 was rated at 370 gross hp.
The 1971 LT-1 was rated at 330 gross hp(less cr)
The 1972 LT-1 was rated at 255 SAE net hp. (little difference to the 71 LT-1).
The 92-97 LT1 Y-body engine outputs more gross hp than any GEN I engine, even the 70's 370 hp LT-1 and the 60's 375 gross hp L84. This fact is in print by sources including GM.

To complete the GEN II story, yes, the LT1 was used in the 94-96 B-body(Caprice/Wagon/9C1 Police PAckage,Impala SS, Buick Roadmaster/Wagon), 94-96 Cadillac Fleetwood. Although these LT1's used iron heads which flow slightly more than the aluminum Y/Fbody cousins. All 94-96 iron headed LT1's used the same 191/196 0.412"/.428" 111ºLSA which is also shared by the 1996-2002 L30 Vortec 305 230hp at 4600rpm/280 lb/ft torque at 2800rpm, and 96-2003 L31 Vortec 350 with 255 sae net hp at 4600rpm/330 lb/ft torque at 4600rpm.
This same roller cam is also used in the other "baby" GEN II engine, the 94-96 4.3l 265 cid V8 RPO L99 that made 200 sae net hp and 245 lb/ft torque used in the B bodies. This engine got better fuel economy than the 5.7 LT1. The 4.3 V8 uses a 3" stroke crank and special length 5.94" PM rods coupled with 3.736" Vortec L30 305 pistons to get to the 265 cid. If this 3" 2 piece RMS crank is dropped in any 1 piece RMS 4" bore block and you now have a more modern 5.0 302 SBC engine. GMPP built a GEN II 302 that made over 420hp with 7000rpm capability.



peace
Hog

[mrx86]

OK

The 90 ZR-1 LT5 / 5.7L have Stock SAE Gross 425HP and 375HP net.

The 1968 Camaro ZL-1 7L Stock have SAE Gross 425HP and 376HP net.

The 1971 Dodge Challenger 7L HEMI have SAE Gross 425HP and 350HP net.

The 1968 Ford Mustang 7L GT500KR have SAE Gross 400HP and ??? HP net.



properly ?

Mrx86

[mrx86]

OK

The 90 ZR-1 LT5 / 5.7L have Stock SAE Gross 425HP and 375HP net.

The 1968 Camaro ZL-1 7L Stock have SAE Gross 425HP and 376HP net.

The 1971 Dodge Challenger 7L HEMI have SAE Gross 425HP and 350HP net.

The 1968 Ford Mustang 7L GT500KR have SAE Gross 400HP and ??? HP net.



properly ?

Mrx86


http://img543.imageshack.us/img543/1682/54037937.jpg

[Corbusa]

Interesting stuff , Thanks guys !!!!!

[Hib Halverson]

(snip) There were 315hp F-body LT1 engines with optional intakes and exhausts.
And what company put such an engine in a production vehicle?
I respectfully disagree about your LT1 hp assertions.
Disagreement respectfully noted
(snip)The 92-97 LT1 Y-body engine outputs more gross hp than any GEN I engine, even the 70's 370 hp LT-1 and the 60's 375 gross hp L84. This fact is in print by sources including GM.
Ok. If it's in print and GM released the info is should be a simple task for you to post some facts to support your disagreement or at least direct me to some location on the web where I can read those facts.

[Hib Halverson]

Don't quote me on this, but I read in an old Legend magazine about the development of the LT5, and believe it was stated they were seeing 445 SAE with open headers on the dyno.

Actually, if that was in the old Legend magazine, whatever article that was must have been talking about the Record Run engine which, slightly modified, made 440-hp.

Also, no engine could make "445 SAE with open headers" because the SAE test standard mandates a full exhaust system.

Stock LT5s made 375-hp SAE net or 425-hp gross with open exhaust.

The next gen ZR-1 if it wasn't killed off would have been 450hp.

The so called "third generation LT5" which would have gone to production for 1995 had additional improvements, including variable valve timing, and would have been rated at 475-hp SAE net. The development program which was that engine ended when the ZR-1 was killed.

[XfireZ51]

Didn't SAE net rating start in 1971? I believe that was part of the reason, along w lower compression, that the 71 LT-1 was rated at 330 v 370hp for the '70 LT-1.

[tpepmeie]

Actually, if that was in the old Legend magazine, whatever article that was must have been talking about the Record Run engine which, slightly modified, made 440-hp.

Also, no engine could make "445 SAE with open headers" because the SAE test standard mandates a full exhaust system.

Stock LT5s made 375-hp SAE net or 425-hp gross with open exhaust.



The so called "third generation LT5" which would have gone to production for 1995 had additional improvements, including variable valve timing, and would have been rated at 475-hp SAE net. The development program which was that engine ended when the ZR-1 was killed.


Gawd Hib you are full of yourself. I shall dig through my stack of magazines tonight to rebutt you. No, on second thought I have better things to do with my life.

[Hib Halverson]

Didn't SAE net rating start in 1971? I believe that was part of the reason, along w lower compression, that the 71 LT-1 was rated at 330 v 370hp for the '70 LT-1.

Could be wrong, but my understanding is that GM began using the SAE-net rating system for 1972.

I remember that it was low compression for unleaded gas in 1971 and SAE-net in 1972.

[Hog]

And what company put such an engine in a production vehicle?

Disagreement respectfully noted

Ok. If it's in print and GM released the info is should be a simple task for you to post some facts to support your disagreement or at least direct me to some location on the web where I can read those facts.

1995 Firehawk, LT1 rated at 315 sae net hp.

1994 Chevrolet Power-The Official Factory Performance Guide" 1994 General Motors Corporation Page 10

There is an actual reference to an actual gross number for the GEN II LT1, but I cant locate it at this time.

peace
Hog

[Hog]

Didn't SAE net rating start in 1971? I believe that was part of the reason, along w lower compression, that the 71 LT-1 was rated at 330 v 370hp for the '70 LT-1.

The 1970 LT-1 was rated at 370 gross hp.
The 1971 LT-1 was rated at 330 gross hp(less cr)
The 1972 LT-1 was rated at 255 SAE net hp. (little difference to the 71 LT-1).

The net rating started in 1972, which is why the 1971 330 gross rating now became 255 net hp in 1972 without major engine differences. The reason for the compression drop was the upcomming switch from leaded fuel to unleaded fuel. Leaded fuel is a high temp lubricant and antiknock agent. Using unleaded fuels in a head without hardened seats will cause the valve seat to recess very quickly. Catalytic converters came in 1975 and lead will coat cats rendering them useless. So GM had to start making changes in their engines to get ready for the upcomming emissions regulations.

So the Vortec 350 that is in my 96-98 GM trucks which are rated at 255 sae net hp @ 4600rpm and 330 lb/ft at 2800 rpm is actually matching the output of the 1971-72 LT-1.

peace
Hog

[mike100]

From 5 minutes of looking into it, 1997 camaro SS and Firebird WS6 LT1's were rated at 305hp. regular Z28 models were 285hp for 96,97 and 275 for the earlier years btw.

The SLP firehawk and SLP SS Camaro got the LT4 in 97 just before the switch tho the LS1 on the f-body.

[Paul Workman]

1995 Firehawk, LT1 rated at 315 sae net hp.

peace
Hog

Yeah, I ran across one of those driven by a couple gals. It was right after I had finished my top end porting on the Z (somewhere in the 400 at the wheels area) The Firehawk was impressive, and I guess the gals thought they were picking on some ordinary C4, but they were entirely overwhelmed by the Z.

But, back on topic, there's gross and SAE net and RWHP and RWHP "under the curve". JMO, but HP at the wheels, where the rubber meets the road is the only meaningful measurement. Everything else is just so much hot water generated that means nothing, far as performance goes, methinks.

P.

[tpepmeie]

Ok I found the article. March/April 1998 Legend magazine. Page 14 is an article by Graham describing the 93MY changes.

"405 bhp was realized in GM Test 1 spec, which means with full vehicle inlet and exhaust system,

in GM Test 20 form, ie., dyno headers and no inlet restriction the 1993MY engine produced 445 bhp with optimized spark and fuel (LBT/MBT)."

So we have two different GM test specifications, with a 40bhp difference with headers and optimized tuning. What I don't know is what atmospheric correction factor GM uses for each of these tests. I believe it is probably 77F / 990mbar (SAE J1349) conditions, but I can't certain.

Doesn't really answer the original poster's question, but offers some insight into the difference with open headers/intake.

[efnfast]

I must agree with Paul, all this manipulation of numbers is meaningless. As Paul said, "where the rubber meets the road". SAE corrected or not, me and the guy next to me are breathing the same air when the right foot hits the floor.

[tpepmeie]

I must agree with Paul, all this manipulation of numbers is meaningless.

You clearly mean that it is all *meaningless* to you, right? If it were meaningless to everyone, we wouldnt have a lengthy thread here, right?

[efnfast]

It just seems there are so many interpritations of hp.
With and without headers or exhaust.
Same for intake.
Air quality.
What day of the week it was, ect,ect.

[Hib Halverson]

Ok I found the article. March/April 1998 Legend magazine. Page 14 is an article by Graham describing the 93MY changes.

"405 bhp was realized in GM Test 1 spec, which means with full vehicle inlet and exhaust system,

in GM Test 20 form, ie., dyno headers and no inlet restriction the 1993MY engine produced 445 bhp with optimized spark and fuel (LBT/MBT)."

So we have two different GM test specifications, with a 40bhp difference with headers and optimized tuning. What I don't know is what atmospheric correction factor GM uses for each of these tests. I believe it is probably 77F / 990mbar (SAE J1349) conditions, but I can't certain.

Doesn't really answer the original poster's question, but offers some insight into the difference with open headers/intake.

Glad you found the article, "tpepmeie".

Seems I was wrong about the early engines...375 SAE net and 415-hp (rather than 425) gross seems to be the case.

The SAE net is SAE J1349. I've heard of the other test, but never knew what the GM designation was nor do I know the correction, but I'd say you're right on 77°F. It wouldn't make sense that GM would use two different atmospheric corrections.

[scottfab]

I must agree with Paul, all this manipulation of numbers is meaningless. As Paul said, "where the rubber meets the road". SAE corrected or not, me and the guy next to me are breathing the same air when the right foot hits the floor.

I'd have to agree also but I suppose there'd be a few it means something to just like regular C4s with a ZR-1 badge on them [-X
HP #s are great talking points but ETs are better :blahblah:

[Dynomite]

You clearly mean that it is all *meaningless* to you, right? If it were meaningless to everyone, we wouldnt have a lengthy thread here, right?

:thumbsup:

The numbers are meaningless to those that do not understand the numbers or the "manipulations" of the numbers (the math) ;)

Most designs that I know start with manipulations of numbers (math) of some sort. And we (some of us) can get pretty close to the end result where the rubber meets the pavement with the math :cheers:

The GM Engineers did not design the engine and drive train by running ETs (trial and error) I would guess. They did the math :D

[Hib Halverson]

(snip)
But, back on topic, there's gross and SAE net and RWHP and RWHP "under the curve". JMO, but HP at the wheels, where the rubber meets the road is the only meaningful measurement. Everything else is just so much hot water generated that means nothing, far as performance goes, methinks.


I must agree with Paul, all this manipulation of numbers is meaningless. As Paul said, "where the rubber meets the road". SAE corrected or not, me and the guy next to me are breathing the same air when the right foot hits the floor.

I'm not so sure we should rush to accept the idea that chassis dyno numbers are a true "benchmark" of engine performance.

There are many factors which skew chassis dyno numbers but have nothing to do with engine performance. In no particular order, some of them are:

1) tires...casing design, tread configuration and tread compounding. (I once did a back-to-back test of two tires just comparing tread confiuration and compounding-the tires were both on the same casing design-and the differece was 5-hp at the wheels. Same dyno, same pressure, same vehicle, some IAT and ECT, and tests 10-min. apart.)
2) tire pressure
3) dyno type, inertia or brake
4) single roller, two rollers or no rollers (direct connection to axles)
5) roller surface
6) wheel spin or lack thereof
7) trans type
8) trans lubricant and lubricant temperature.
9) rear axle ratio, lubricant and lubricant temperature
10) powertrain mountings
11) coolant temperature and temperature rise during test
12) different in IAT of more than 7°F regardless of correction
13) technique of dyno operator
14) condition of dyno

So, you see...chassis dyno numbers should be taken with a "grain of salt". They are embraced by the aftermarket performance industry and the enthusiast community because chassis dynos have been well-marketed by their manufacturers, they're loved by the automotive press and widely used by tuners. Chassis dynos are cheap and easy and perfect for bragging rights but fraught with potential inaccuracies.

I'm first to admit to using chassis dyno data all the time. Sometimes I strive to eliminate as many of the potential inaccuracies as possible. Sometimes I don't, but I know in the back of my mind that engine dynamometers are far more accurate devices for comparisons.

As for corrections...the belief that atmospheric corrections don't make a difference is just ridiculous. In fact, when I look at chassis dyno data, I'm more concerned with whether or not a correction has been applied and if so, what correction than I am with the inaccuracies of chassis dynos.

Recently, I was discussing a particular engine modification package with an aftermarket vendor. I asked for some of his confidential test data and he provided it. Same engine, same dyno, same test run...the engine made 646.0-hp "standard" corrected and 613.9-hp SAE-corrected.

See why the aftermarket and braggers like "standard" corrected data rather than SAE-corrected?

But, SAE-corrected is much more characteristic of the real world because of its use of 77°F for intake air temperature.

Lastly...
(snip)
HP #s are great talking points but ETs are better :blahblah:

ETs are either the most inaccurate way to bench mark engines or the most accurate way to benchmark the whole "package"...driver and car.

Do drivers are bragging about their engines. The first driver who majorly sucks on the starting line and has crappy tires but has a really good 350 in a ZR1 might go 13.2 The other driver who gets really good 60-foots, has his/her tire configuration just perfect but has a so-so 350, can run a 12.8.

So...who's got the best motor?
But...who's got the best ET?

[scottfab]

ETs are either the most inaccurate way to bench mark engines or the most accurate way to benchmark the whole "package"...driver and car.

Do drivers are bragging about their engines. The first driver who majorly sucks on the starting line and has crappy tires but has a really good 350 in a ZR1 might go 13.2 The other driver who gets really good 60-foots, has his/her tire configuration just perfect but has a so-so 350, can run a 12.8.

Sounds like a line of hair splitting to me.
ETs can be the best way to measure overall performance there is.
Sure some exceptions can be brought to bear but there's many more exceptions that can be added.
Why even the effect of the moons gravity has an effect and the
imperfections on the asphalt under the right rear wheel. There
could even be a mosquito hit the windshield and slow it down.
Same driver running two different cars on the same night could even have
different wind conditions, a huge fly hit the windshield plus the major effect of 0.01oz of more fuel in one car vs the other. gezzzzzz
Seems like an exercise in futility to me.
A huge amount of meaningless exceptions can be added to dyno derived HP numbers too but I won't go there right now.

HP numbers are a fine metric but so is how many dimes you have in
the change holder. Being able to wave bye bye puts the "P" in performance. It's all together a better metric whether it's SAE or standard or pure air guitar corrected numbers.


So...who's got the best motor?
But...who's got the best ET?

Whose got the shiniest dimes in the change holder?
Depends on the quality of the eye looking at it and the ambient air quality that the light goes through. But it should be SAE corrected air quality else
it's all for naught. And one should use proper wide spectrum light to test with and of course the angle of reflection should be at 90deg +/- 0.0000001 deg or the error will be so great that all bets are off. :bootyshak
Which is the better car?
1. 10,000 rpm V8
2. 502ci V8
3. 1800lb with driver
4. first over the 1/4 line

Answer: depends on which one I'm sitting in and Voltage measured at the spark plug of course. :)
Any hair that is split can always be split again until it looses meaning.

[XfireZ51]

Pretty much why you judge power on basis of trap speed not ET. Trap speeds can vary based on track setup.

[Paul Workman]

The trouble with standards, are there's so many to chose from:

J1349 circa 1972, June 1990, 2004 (crank hp)
J1995 (gross hp)
J607
J2723 certification spec
VCA (UK certification spec)

And, NONE of these address AVERAGE torque or hp at the wheel!

Bottom line: You can measure at the crank, or you can measure at the wheels, or somewhere in between. But, trying to predict one from the perspective of the other is full of variables as to make an absolute prediction either way almost folly.

I believe the trick is to pick the one that best fits the application, make the measurements as a base case for comparison to future improvements or modifications.

Examples: Engine builders with clients paying for results aren't interested in driveline losses. Drag racers aren't interested in peak hp at the crank, they're interested in trap speed (and ET to a lesser degree).

To get J1995 (crank net hp) I have to pull the motor. But, considering inertia of drive line hardware (including rotating mass), the hp number derived is significantly removed from how the car is going to actually perform, at least where differences are subtle.

For seat of the pants fun and a more accurate indicator of drag race result prediction, the inertia dyno measuring output at the wheels is a much better fit. However, quarter mile trap speed is a very good indicator for performance comparision! It isn't perfect either, but it does take into consideration "power under the curve" which is largely overlooked when in a pissin match over gross vs. net vs. shaft vs. wheel horsepower ratings.

Where the rubber meets the road is where real performance is demonstrated...I think is the main point ... at least it is for me. I'm not saying either isn't important in their own right - engine builders have their point of view and race drivers have a different perspective on output. But, trying to predict either from opposite ends of the drive line (read: is it SAE 15% standard loss or some other 18% standard) is where things get fuzzy really fast.

Hib...You said Barney measured 413 at the wheels. You used 18% drive line loss to predict you have about 504 net hp at the crank. My 90 Z measured 432 hp at the wheels, using SAE/Marc's 15% drive line loss, my net crank calcs to be 508 hp. Now, going on net crank hp and nothing else, I imagine it would be a near toss-up in the quarter mile, all things being equal. Care to race and compare??

P.

[Fully Vetted]

:happy1:

[Dynomite]

Care to race and compare??

P.

I doubt you would want to race with me :D

I did the MATH :sign10:

Cliff

The 500 hp LT5 Rebuild (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp.html)
1991 ZR-1 (LT5) Performance (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-4.html#post1581690515)

[Hib Halverson]

(snip)
Hib...You said Barney measured 413 at the wheels. You used 18% drive line loss to predict you have about 504 net hp at the crank.

That's correct. Actually, that session was three passes on the Dynojet at K&N Engineering near the end of the period when the car was a "project vehicle" for "Vette Magazine." It was two runs at 410 and one at 413. There were also a few in the high 400s, but that was with a different calibration.

My 90 Z measured 432 hp at the wheels, using SAE/Marc's 15% drive line loss, my net crank calcs to be 508 hp. Now, going on net crank hp and nothing else, I imagine it would be a near toss-up in the quarter mile, all things being equal. Care to race and compare??

P.

Well, uh...(choke)...:-D

I don't know how this thread ended up being a wee-wee length contest. I thought we were talking about how GM has rated engines, the differences between the old "gross" power rating system and the current "SAE net" power rating system and the ins-and-outs of comparing power output using dynos.

But...I will conceded, Paul, that your weenie is bigger.

Likely you'd wipe my sorry butt all over the track seeing as you have headers, shorter gears, more power to the ground and significant drag racing talent revered by most here on the ZR1 Net Forum.:notworthy

[scottfab]

.....snip.....
Where the rubber meets the road is where real performance is demonstrated...I think is the main point ... at least it is for me.
...snip..
P.

Well put.

[A1990]

Pretty much why you judge power on basis of trap speed not ET. Trap speeds can vary based on track setup.

I think this pretty much sums up this discussion, there is no one right answer as Dom ends up arguing with himself. :handshak:

[Fully Vetted]

Yeah, I was trying to figure that out. Thought it was just me...

[Paul Workman]

Well, uh...(choke)...:-D

I don't know how this thread ended up being a wee-wee length contest. I thought we were talking about how GM has rated engines, the differences between the old "gross" power rating system and the current "SAE net" power rating system and the ins-and-outs of comparing power output using dynos.

Ins-and-outs of comparing power output via dynos...WAS exactly my point!

Engine output and how it is measured has been a delema for real engineers for some time, hence references to the evolvement of various SAE standards for measurement, and their revisions over time. And, I was agreeing (somewhat, perhaps) with you with regard to the ambeguity ("grain of salt", you said) that results between direct vs. indirect measurements.

You misunderstood my piont; no dick-measuring at all. Take "yours and mine" out of the discussion and say A = 504 net chp via 18% correction between the tire and the flywheel, and B = 508 net chp via 15%. That amounts to a 1% difference in net chp - well within the margin of error to the point of being essentially the same.

However, measured at the tire, B = 4% more than A. We can agrue the differnces between dynos too, but all things being equal, which horse are you going to bet on in a race? Again...reinforcing your agruement regarding (essentially) the pitfalls of extrapolating measurements via indirect methods, and my point that measurements at the tire are much more indicative of motor output, but terminal velocity resulting from WOT accelleration testing is probably superior to anything else we have to determine real performance, i.e., where rubber meets the road...maybe.:o

Interesting discovery... In boning up on SAE standards re this topic, I ran across "taxible horsepower". Essentially a British standard where a horsepower tax was levied on manufactures where the number of cylinders and bore diameter were the key ingredients in the calculation. As result, Jaguar (and others) motors in the 50s were built with fewer cylinders and strokes significantly longer than bore diameter. Eventially, the standard was relaxed in order to compete effectively with other world manufactures that were trending toward over-square bore/stroke via bore diameter. Another example of govenment and unintended consequences. Makes ya wonder what sports cars would be like w/o any restrictions, huh? Supercharged V12s or V16s maybe?

Anyway...I agree w/ others that this topic has probably been beat to death...long ago.

P.

P.

[Blue Flame Restorations]

Beaten like a drumb.:blahblah:

You can lead a horse to water..............but if the horse thinks he knows everything there is to know about water.....................

[scottfab]

... snip...
But...I will conceded, Paul, that your weenie is bigger.
...snip...


Definitely time to close this one.
But that Hib quote would be a nice addition to Paul's signature :jawdrop:

[QB93Z]

This discussion has run its course. The tread is now closed.

Jim