Highhat

Here is why I believe you cant completely rely on a dyno reading without a reference point. This is an 11 sec car, but the dyno only shows 337HP at RW, when it should be 450HP.

I think this low reading is attributable to high stall loose converter (3500). Any one else agree?

See this article: http://www.converter.com/whatsnew_dynamometer.htm


But in any event, it is useful as a comparison, as my head swap gained me 45hp and 50TQ over a greater range:


(388ci, 11cr)

dgruenke

I thought the torque curve on the stroker engine was supposed to be flatter than that.

zwede

The absurd torque readings below the stall speed are obviously due to slippage, but the hp reading is reasonable. A well setup car will run 11's on that kind of rwhp.

Highhat

Thanks.

ajrothm

The torque is that high due to the multiplication of the stall. The stall is definetly killing off some HP up top but. Lots of factors contribute to rwhp loss. Drive shaft/half shaft weight, gear ratio, tire type, type of oils used in the drive train, parasitic losses from the fan/fuel/water pumps etc.

The reason that car will run 11s is because its going to leave really good(assuming the car hooks). 500lbs tq at 2800, thats an instant hit, I bet that thing 60's in the 1.50s some where assuming the chasis is setup.

What all is in the motor?

427Hotrod

This is also a Mustang dyno..they read a lot lower than a Dynojet does.


JIM

Highhat

You think the stall is going bad?

Motor:

388ci, 11cr
Dart Pro 1 215, Super Mod Ported
CompCam XS-290S; 1.6 roller rockers
Victor Jr, 1inch tall, plus 1inch HVH Supersucker, & 1/2"phenolic
Holley 950HP
Turbo 400, 3.70 rear; 3500 stall
MSD ignition

big_G

Yes, mine dyno'ed about 50 hp less on a Mustang dyno...Must be the name.

MotorHead

Mustang dynos are about 10% less. 450RWHP in a C3 is close to 575HP on an engine dyno.

ajrothm

Damn I didn't even notice it was a Mustang dyno...LOL they definetly read lower


I don't think there is anything wrong with your car at all. On our LS1 cars, when we can "lock" a big stall converter, they will gain 20-30rwhp when using a 3600-4000 stall and locking the converter over letting the converter stall and flash. Not to mention a TH400 eats lots of HP also. If your car was a 4spd I bet it would make 375rwhp at least, and thats on the same Mustang dyno, on a DJ it would probably be 400rwhp which is 500 crank HP or so.

Either way that TH400 with that converter is what makes that car run 11s.

You have a copy of the time slip or remember the run? I am curious. How much does the car weigh? I want mine to run 11s also with a TH400.

PNK

Have to agree with Motorhead here my engine was dynoed at 585HP and the chassidyno showed 449 RWHP

Budman68

What kind of 11 did you run. 11.98 or 11.3? Looks like your close to 400 at the crank, so that should be close to 11's, but your torque curve is strange for a 388. Should be a lot flatter.

zwede

Buddy: That torque curve is typical of a high-stall converter. They all do that.

ajrothm

EXACTLY. COMPLETELY different then a manual car powerband/torque curve

I am curious as to the details of the 1/4 runs and the raceweight. I have him around a theoretical 481hp at the crank. Thats probably a little low considering how loose his converter is. I bet he is really making around 500hp at the crank which is typical for a good 383.

ajrothm

Thats about a 23% parasitic loss in the drive train/fan/pumps etc. Thats pretty damn good. I am assuming your car is a stick with an electric fan and fuel pump. I bet that sucker HAULS ***!

Budman68

Interesting, Why would you want an automatic behind a 383 then...??? Seems like you would want to build a bullet proof 8000 rpm 350, then waste money on a 383 torque monster with an auto. I've always been confused with this 383 thing. Help me out.

zwede

I don't know why anyone would want a slushbox.

zwede

Was the chassis dyno a dynojet or mustang? Also, what standard was used for the engine dyno? It's easy to make an engine dyno show 10-15% high or low by playing with accessories, coolant and air temps.

MotorHead

Mine seemed to come out about the same 547 HP on the engine dyno
and 427 RWHP on a dynojet looks like 23 % loss too

gerry72

Why wouldn't you? You build a combination and that's what makes the car right. And it costs far more to build an 8k rpm engine than it does to build one for a much lower rpm. Naturally aspirated high rpm engines are very peaky with narrow torque curves that are nearly unliveable on the street.