Need HP/Torque insight

[Roostmonkey]

I'm just curious about the relationship between hp and torque. I see guys with like 230 hp and over 300ft/lbs. My car dynoed at 325hp and 320ft/lbs and I'm wondering what variables allow mine to be nearly equal (hp/ftlb's) while others can vary so much.Also, I got my #'s at 13 psi, is it safe to say that things will remain somewhat equal if I bring it up to say 16 psi?

[Guest asad137]

hp = torque * RPM / 5252

 

Your HP will vary a lot depending on where in the RPM range you make the torque. Tons of torque at low RPM can lead to a very low peak hp number; conversely, a modest amount of torque at high RPM will give lots of hp.

 

Asad

[JMortensen]

I think the turbo L6 guys show low hp and big torque because the stock cam is so tiny. The high strung NA L6's make their power up top, so they have higher hp than torque. So like Asad said, basically if you make your power on the bottom end you'll be torque heavy, and if you make it on the top end you'll be hp heavy.

[mobythevan]

the rule of thumb: torque heavy engines are fun to drive on the street, daily drivers

[Roostmonkey]

My dyno doesnt seem tp be consistant with what your saying

[thehelix112]

Roostmonkey,

 

Yours is somewhere in between. You have a nice flat torque curve throughout much of the rev range. A good thing for a street car. What cam do you run?

 

Dave

[Guest bastaad525]

I'm just curious about the relationship between hp and torque. I see guys with like 230 hp and over 300ft/lbs. My car dynoed at 325hp and 320ft/lbs and I'm wondering what variables allow mine to be nearly equal (hp/ftlb's) while others can vary so much.Also, I got my #'s at 13 psi, is it safe to say that things will remain somewhat equal if I bring it up to say 16 psi?

 

Sounds like your'e talking about my motor

 

you can make a lot of torque but make relatively little HP. Diesel motors are like that. It's because they make all their power down low, and don't or can't rev up to higher RPM.

 

The thing with my setup is that it makes great torque, 300 ftlbs flat as a table from about 2800 to 4200rpm. But then it falls off very quickly, partially because, at the time I dynoed, my boost controller was sucking and I was dropping boost from 14 down to 11psi by 6000rpm. Other issues might include that the stock T3 is really past it's efficiency at such high boost at high rpm, and also I have a crappy exhaust that's restricting flow.

 

You can make a lot of HP but little torque. The trick is to make the torque NOT fall off until very high in the RPM range. Think Honda engines... they use Vtec to extend the range that the engine makes good torque, and if you look at a typical honda vtec dyno, they make a super flat torque curve, from very low rpm all the way up to redline, the torque hardly drops at all.

 

And since torque x rpm / 5252 = horsepower, you end up with way higher hp than torque.

 

That's why hot cams make more HP as well. I found when I upgraded the cam in my non turbo Z motor, the torque peak number was almost EXACTLY the same, but the torque peaked later, and held steady until later in the RPM. The result? Almost 20 more HP.

 

I've always felt that the motor that makes roughly equal amounts of torque and HP are the best motors... their not 'grunters' like my engine, and dont need to be revved crazy high to get you moving either.

 

L28's non turbos usually default more torque than HP, but some breathing mods almost always change that around.

 

L28 turbos almost ALWAYS make more torque than HP, at least on the stock turbo they do, because at high rpm the thing just runs out of breath.

[Roostmonkey]

helix

Its the stock 81 cam...all internals are stock.

 

bastaad...I was talking about your motor. Just as an example, but ive seen numbers very similar in other cars.