[241]

Hmm....So I have my car running 350HP and 400lb/feet of torque.

What will happen to the performance of the car if I leave the HP the same and find mods that add alot more Torque?

[dave-r]

I think you are confused? If you increase torque you are increasing horsepower unless you are making your peak torque at much lower rpms.

Read this;

http://challenger.mpoli.fi/phpbb/viewto ... 3936#13936

It should help you to understand.

[241]

I think you are confused? If you increase torque you are increasing horsepower unless you are making your peak torque at much lower rpms.

Read this;

http://challenger.mpoli.fi/phpbb/viewto ... 3936#13936

It should help you to understand.

How can I promote peak torque at low RPMs?

[dave-r]

Why do you want to? Do you want to pull a heavy load at slow speed? Did you actually read and understand the link I gave you?

To make low rpm torque you normally fit a camshaft with less duration. This will lower the rpm where you make peak torque. It will also lower your HP and reduce the top speed you can run.

Making your engine bigger (more inches) will increase torque. Put another way. burning more fuel and air increases torque. So anything that makes the engine more efficent will increase torque and HP.

[241]

Why do you want to? Do you want to pull a heavy load at slow speed? Did you actually read and understand the link I gave you?

To make low rpm torque you normally fit a camshaft with less duration. This will lower the rpm where you make peak torque. It will also lower your HP and reduce the top speed you can run.

Making your engine bigger (more inches) will increase torque. Put another way. burning more fuel and air increases torque. So anything that makes the engine more efficent will increase torque and HP.

Torque at low RPMs = good acceleration, ok bud?

[Christer]

Torque at low RPMs = good acceleration, ok bud?

I think that a balance between torque and hp is the best cure for a street engine. Let´s play with the thought that you increase the stroke and decrease the bore. This will probably add torque at lower rpm:s and give max hp at lower rpm:s. Will you get a quicker car? Probably not. The engine will not be as revving as before, and the top-rev will be lower....and you will be a dissatisfied runner-up.

[dave-r]

Torque at low RPMs = good acceleration, ok bud?

Only if you want to accelerate 0-30mph or some low speed like that and at the same time sacrifice top end speed.

I explain all this in the article I gave you a link to. Why do you think dragsters make huge horsepower?

A diesel truck will make HUGE amounts of torque at low rpm. You wana bet how well that accelerates?

[dave-r]

I have had another think about this while I was walking the dog.

It is quite difficult to get your head around some of these ideas. Well I find it difficult anyway.

What made your original question hard for me was you stated you wanted to increase torque but keep HP the same.

Generally when you increase torque you also increase HP because HP is a factor of torque X rpm. I guess, now that I have thought some more about this, that it might be theoretically possible to increase lower rpm torque a bit and leave peak torque (and the torque after peak) the same. In this case the car would accelerate a bit quicker in the rpms below peak torque because HP will have increased at those rpms too.

However I think in real life it would be difficult to make any changes that did not effect the torque or power curve over the whole area.
Without inputing the data into a desktop dyno or something like it it is difficult to see what the end result might be?

I have the details of my engine in a desktop dyno. I decided to see what the effect of fitting a stroker crank would be. I guessed that the increased capacity would increase torque and power over the whole rpm range and make the car go faster. Making the engine bigger should make it faster yes?

No. In fact adding a 4.15-inch stroke crank would give me peak torque at lower rpms and therefore power would be down and the car would run slower in the quarter mile.

One thing we have not mentioned is gears. Putting a lower gear in your axle will increase torque at the wheels proportionally. A 10% lower gear will give you 10% more torque.
This will give you harder acceleration. But again - you get nothing for nothing - it will lower your top speed by 10% too.

All this is explained in that thread I gave you the link to.