Real HP

[jdenn47]

I have a 86 Vette with cast iron heads and the rated HP is only 235.
Is that a true HP fiqure as a lot of V6's today have more than 235 HP?
I have heard that they rated HP differently due to all the Pollution Crap they had on it back then and it would be more equivalent to near 300 HP by todays standards. Any feedback ?

 

[SSTibet]

I have a 86 Vette with cast iron heads and the rated HP is only 235.
Is that a true HP fiqure as a lot of V6's today have more than 235 HP?

I am by no means an expert on this. But I have followed threads here and in other forums saying that the Hp figures are measured / stated per SAE standards and it is the power at engine output with all accessories attached (hence all of the emission stuff, air conditioning, heater, etc.). I have also read that GM states its power ratings somewhat lower than designed power due to some customer liability issues.

I have also read that Hp is stated at the rear wheels, but I do not think that is true.

Cheers,

Selim

P.S. You may refer to Ken, side admin, who is a true expert on these matters.

 

[redc4corvette]

ON the L98 motor well it's just a truck motor and is a torker for pulling big loads.
I think it's over rated at 235 hp..

 

[vetteboy86]

Actually if you have an 86 with cast iron heads the hp rating is 230 hp, big deal right. I think they are a little underated. I was sitting at around 260 rwhp per a G tech meter, and stock motor. Either way you look at it, you are sitting at 6 second car to 60, which isn't bad for a 20 year old car. If you want you can purchase a cheap Gtech meter. They are a good toy to play around with.

Craig

 

[Edmond]

The rating that is given is the power at the flywheel. The situation you're talking about where they started rating them different was back in the 70's where they measured hp without any accessories or pollution items on it.

In the case that people talk about RWHP, it's usually after someone has measured it, be it on a dyno or a G-tech like Craig has done. I think some people will call it real world horsepower because it's what hits the ground.

Yes, there are many V6's that are out there today. If you're concerned about them outrunning you, don't. Comparing a Corvette to a V6 isn't a fair comparison, especially when you factor in the age difference. What L98's are known for are for it's massive torque that peaks around 3200 rpm.

And there's nothing wrong with bolting on a few exhaust mods like a set of long tube headers and a nice free flowing catback system. That could get you 30 horsepower. If you still have the stock exhaust on there, it's very restrictive and only flows out of one outlet on each muffler.

 

[warren s]

Dont forget that its touque that makes a car accelarate, horsepower has more to do with how fast it will eventually go. Many V6s can make lots of horsepower these days but it doesnt mean the car is very fast. Gearing and light weight combine to make some small cars with not that much advertised horsepower pretty quick.

The SAE NET horsepower is the standard for compairson. Only recently has the access to dynos been so great that people can compare rear wheel ponies.

Some engines were rated (gross) on the dyno not even installed in the car, and some were rated below their power peak for various reasons.

The switch to SAE NET in the early 70s produced lower numbers because the engines were installed in the car as you would buy it. Horsepower was measured at the flywheel.

 

[04c5ragtop]

I remember a line I read somewhere - "Horsepower moves cars on the showroom floor, torque moves them on the track".

Tim

 

[Edmond]

You also have the advantage of rear wheel drive. It'll take more work to pull something than to push it.

 

[vader86]

YES, the 86 is accurately rated in NET HP terms at the FLYWHEEL, as are all cars since the mid 70s.

It puts down about 200 at the rear wheels, and using 15-18% drivetrain loss, you'll come out with about 230-235. (depending on heads and transmission)

The 86 will smoke nearly all mustangs and any V6 i've come up against, remember you also have 330 lb-ft of torque that will get you moving alot faster than your opponents.
However, the torque number, on my car at least, is not correct. The car puts down a little over 300lb-ft, and I found, after my dyno testing, that the car puts out about 350lb-ft at the flywheel. This number will vary from car to car a little though.

 

[Vettefan87]

So my Gtech meter was about 65 HP wrong when I got about 265 at the Rear wheels with only doing a chip, airfoil, and mufflers, since I know those mods are probably good for ten or so that makes it 50 off? Can somebody explain?

 

[vader86]

The G-Tech is notoriously inaccurate, I would only buy one to measure my times if I lived a very long way from a racetrack.

 

[ProEMTPFF]

I've searched the threads for info on the G-Tech. I know I saw a thread that had a link with the G-Tech cheap. Anyone know where to get one cheap??

 

[Vettefan87]

http://www.softwareandstuff.com/CES10539.html

 

[ProEMTPFF]

Thanks......are they "fairly" accurate?

 

[G Winter]

Thanks......are they "fairly" accurate?

never tried one but some in here say it gives a good idea. something to base changes on .

 

[Vettefan87]

I don't know people say that they are way off and should not base any results on actual HP ratings. So buy at your own risk I guess. I have one and like it.

 

[redc4corvette]

The people that say it is way off don't know how to work it that is a fact.
Mine if I set it up is more accurate then the 1/4 mile track .
I used my G- tech at the track and the roll out was wrong and the track on the tower side was only 1270 feet not 1320.
The track has surveyed ,the problem was corrected it after 30 years .Now I am the ass hole that would protest all the time . But everyone racing now thinks I an ok guy and all is well now.
Change always hurts.

 

[Mad-Mic]

i'm gonna add this thread to this post. it is the same thing and has alot of other info that i posted and don't feel like copying pasted

http://www.corvetteactioncenter.com/forums/showthread.php?t=61708

 

[garycr14]

One thing you have to keep in mind is that all engines are not created equally. The rated horsepower is 230, but you could easily have 250 in your particular engine. Depends on how "clean" the casting of the heads are, how well the gaskets happened to match up, and a dozen other things that can make a big difference inside an engine. Becase of the torque, L98's are pretty fast off the line, but they do tend to flatten out (at least without mods) above 4200 rpms, which is why porting heads, changing exhaust sysem, headers etc...can be important for increased performance with this engine. The best way to have your car measured is with a good dyno, the gteck's are ok, but they need to be used on flat surface for accurate readings, and most roads are not really all that flat so the readings can be thrown off some. But good enough to use when modding your car, as long as you track it on the same stretch of road after each mod.

 

[Mad-Mic]

One thing you have to keep in mind is that all engines are not created equally. The rated horsepower is 230, but you could easily have 250 in your particular engine. Depends on how "clean" the casting of the heads are, how well the gaskets happened to match up, and a dozen other things that can make a big difference inside an engine. Becase of the torque, L98's are pretty fast off the line, but they do tend to flatten out (at least without mods) above 4200 rpms, which is why porting heads, changing exhaust sysem, headers etc...can be important for increased performance with this engine. The best way to have your car measured is with a good dyno, the gteck's are ok, but they need to be used on flat surface for accurate readings, and most roads are not really all that flat so the readings can be thrown off some. But good enough to use when modding your car, as long as you track it on the same stretch of road after each mod.

yeah they do but with just a few mods......... 02 M6 Firehawks go down

http://www.corvettekillstories.com/photogallery/albums/Mad-Mic/Racing/87%20Vette%20vs%2002%20Firehawk.wmv

this is leaving it in D from around 65 mph letting the trans shift itself. usually i manual shift and shift at 5100 rpm. it just pulls a tad harder.