engine building? Hp or torque for the street...

[Hack]

snip. You feel torque, snip
Daniel

I agree for the most part with everything you said except this. You feel acceleration, which is related to HP, not torque.

Also the anti Hack quote is incorrect. If someone makes an average of 1,000 ftlbs of torque between 1,000-2,000 rpm they will get waxed by the next guy making 500 ftlbs between 3,000-6,000. The rpm numbers are what you need to figure HP, which gives a more complete picture than torque numbers.

 

[SoCalCruising]

Hack: my point was that is you model the engine for a certain hp, but limit the torque, then you may be forced to make the hp at high RPMs. Then I said that is costly. I didn't argue with your premise, only the cost of that premiss when not planning for enough torque, or enough at low/mid RPMs. You switched the argument to ave. hp in your desired RPM band, which is a better measure.

I have a diesel, too. I know about high-torque, low RPM motors and speed. My case is the cost of making the hp at very high RPMs.

 

[bnickel]

torque=amount of work being done
HP= how fast the work is getting done

you can't have one without the other...PERIOD.

for a street engine the work needs to be performed at lower RPMs, below about 5-6k RPM and the torque curve needs to be fattest about in the middle of that range with peak torque occurring about in upper third of that range.

an engine that makes all of it's power higher than 6K is not a street motor and will not produce good driveability on the street no matter what you do to it.

torque is king on the street as long as hp is able to keep the engine in the appropriate RPM range of the torque peak.

 

[Hack]

Hack: my point was that is you model the engine for a certain hp, but limit the torque, then you may be forced to make the hp at high RPMs. Then I said that is costly. I didn't argue with your premise, only the cost of that premiss when not planning for enough torque, or enough at low/mid RPMs. You switched the argument to ave. hp in your desired RPM band, which is a better measure.

I have a diesel, too. I know about high-torque, low RPM motors and speed. My case is the cost of making the hp at very high RPMs.

We're probably thinking the same thing but partially saying it differently.

Of course there's no reason to try to limit torque, because you want good horsepower, which is based on torque.

I didn't feel as though I switched my arguement with regards to adding the word (average), just tried to clarify. If you have a high peak HP but HP is low everywhere else, your engine will not function well. I try to be brief, but sometimes meaning can suffer..

I think a lot of people confuse good HP at low RPMs (through out the RPM range you want to use) with torque. You do need a nice flat power band to accelerate a car well.

 

[Hack]

torque=amount of work being done
HP= how fast the work is getting done

you can't have one without the other...PERIOD.

for a street engine the work needs to be performed at lower RPMs, below about 5-6k RPM and the torque curve needs to be fattest about in the middle of that range with peak torque occurring about in upper third of that range.

an engine that makes all of it's power higher than 6K is not a street motor and will not produce good driveability on the street no matter what you do to it.

torque is king on the street as long as hp is able to keep the engine in the appropriate RPM range of the torque peak.

Ok, your definitions at the outset are correct. So you want the work of accelerating your car to be done quickly - meaning you want HP. I don't understand why you keep talking about torque. Torque says, "yes I will be able to make it through the quarter mile." HP says, "this is how quickly I will get through."

I agree 100% that you want the engine to function between 2k and 6k rpms for street driving. A good build for the street maximizes the average horsepower in that range.

You haven't said this in the post I quoted, but some people seem to think that torque gets you going and HP takes over. That is not true. HP is what accelerates a car. The more HP the faster the car accelerates.

 

[bnickel]

Ok, your definitions at the outset are correct. So you want the work of accelerating your car to be done quickly - meaning you want HP. I don't understand why you keep talking about torque. Torque says, "yes I will be able to make it through the quarter mile." HP says, "this is how quickly I will get through."

I agree 100% that you want the engine to function between 2k and 6k rpms for street driving. A good build for the street maximizes the average horsepower in that range.

You haven't said this in the post I quoted, but some people seem to think that torque gets you going and HP takes over. That is not true. HP is what accelerates a car. The more HP the faster the car accelerates.

wrong, torque is what moves the car and get's it moving, HP only determines how quickly that torque moves the car. if a car has 500 hp and only 300 lb/ft of torque it's not going to move the car very well, conversely if a car has 300 hp and 500 lb/ft of torque it will move out very nicely. there is a reason why the Buick GS 455 was the muscle car it was...510 lb/ft torque even though it only had 360hp. the 428CJ was the same way as was the 426 hemi.

on the street TORQUE is KING.

 

[Foxfan88]

wrong, torque is what moves the car and get's it moving, HP only determines how quickly that torque moves the car. if a car has 500 hp and only 300 lb/ft of torque it's not going to move the car very well, conversely if a car has 300 hp and 500 lb/ft of torque it will move out very nicely. there is a reason why the Buick GS 455 was the muscle car it was...510 lb/ft torque even though it only had 360hp. the 428CJ was the same way as was the 426 hemi.

on the street TORQUE is KING.

but wouldnt the 500 hp and 300 tq engine smooth out in the upper rpms??

 

[brianj5600]

Y'all are goofy!

 

[brianj5600]

Oh, and when I had a motorcycle dynoed, they only could get hp #s w/o an input from the tach. It seems that a dynojet dyno measures HP and calculates torque. Go figure.

 

[bnickel]

but wouldnt the 500 hp and 300 tq engine smooth out in the upper rpms??

smooth out? it would probably pull harder in the upper RPM like around 7000-7500 RPM which isn't good for a street motor

 

[jerry S]

I guess this could be a tech question, but sort of talk.

What would result in a more fun street car:
flat tq curve around 450 with 350hp
or
flat tq curve around 450 with 500hp

Your choices are like asking "who would you rather have wild sex with: "Prudence McFrump or Jessica Alba?"

No brainer. It is choice 2 in both cases.

 

[Hack]

wrong, torque is what moves the car and get's it moving, HP only determines how quickly that torque moves the car. if a car has 500 hp and only 300 lb/ft of torque it's not going to move the car very well, conversely if a car has 300 hp and 500 lb/ft of torque it will move out very nicely. there is a reason why the Buick GS 455 was the muscle car it was...510 lb/ft torque even though it only had 360hp. the 428CJ was the same way as was the 426 hemi.

on the street TORQUE is KING.

"HP only determines how quickly that torque moves the car"

EXACTLY. If you don't care how quickly your car will accelerate, build for torque only.

The Buick GS wasn't that fast. Modern cars with much less torque but more HP will walk all over it. Look up examples and they will make my point.

 

[Helmantel]

It's the rear wheel torque that accelerates the car.

For rear wheel torque, you need either engine torque or low gears (and thus high rpm). Since both engine torque and rpm contribute equally to engine horse power, you could say that to win races, you need to look at horsepower. That assumes of course that gearing is optimum.

More accurately, you should say that the goal of a race engine is to have as much hp under the curve in the rev band that is going to be used.

 

[brianj5600]

I curious which one only makes 350hp. Dyno charts I have seen at that level, hp and tq are similar. I thought also that torque was good for pulling a trailer and hp was good for acceleration. A turbo throws it all out the window because you get both.

 

[10secgoal]

Didn't we already have some huge thread about this ? My car has always dynoed low. 275hp and 363trq to the rear. But it ran 12.1's all day. My sig is just me being a smart ass to people building 500 8k spinning "street cars." Torque is a blast. Spinning the tires while you are already moving at 65 mph is kinda fun.

 

[Hack]

Didn't we already have some huge thread about this ? My car has always dynoed low. 275hp and 363trq to the rear. But it ran 12.1's all day. My sig is just me being a smart ass to people building 500 8k spinning "street cars." Torque is a blast. Spinning the tires while you are already moving at 65 mph is kinda fun.

Just because your car dynoed with a torque number that's higher than the HP number at a certain rpm doesn't change the physical laws of the universe and make torque responsible for the quickness of your car in the quarter mile. You are probably making a lot of HP at lower RPM than most people which makes it more usable on the street, though. Similar to having a big block but without all the weight.

As far as spinning the tires at 65 - sounds scary and impressive. I've read about your car build and I love it. I hope some day I will complete a complicated project like that. However I will always build a car to hook up and handle. I prefer acceleration to spinning tires. I will probably never build a car with the crazy HP like yours for that reason. I'll just read about yours with awe and respect.

Getting wordy here but I want to make sure everyone realizes that I respect what you and others on here have accomplished and I would never take anything away from that. I just wanted to make a point about HP and torque. It's more theoretical than practical in some ways, but I still think it's useful knowledge for people to have.