NITROUS OXIDE ( nos / n2o ) advice forum

Hi brainboxes, before I go and talk bollox on another forum (cos something is niggling at me) please confirm.
If you increase engine torque, surely you MUST be increasing BHP - RIGHT!

Let me explain, the BMW840 over the years had 2 engines, a 4.0 & 4.4
BMW state they both had 286BHP, but the 4.4 had more torque, is someone telling porkies for insurance reasons?
Please help to put this myth to bed guys.

It depends what you do to the engine mate. You can tweak an engine to make a tad more bhp but with a lot more torque... I guess in the greater scheme of things that a tuned engine with improved torque would possibly see an increase in bhp ??

But the ratio of bhp to torque will change. My last engine was 200hp with 210 ft/lbs. But on nos it did 400hp with 540 ft/lbs.

Cheer Pel, Its a debate on the bimmer forum, but no one can conclusively proove it, although to help, I found this calculator: http://www.metaris.com/hydCal/RPMHP.asp

PEAK BHP is ONLY 'related' to PEAK TORQUE it is NOT 'DIRECTLY' linked

You can have one engine with a huge LOW RPM PEAK torque and low relatively PEAK power at high RPM.

Power is torque multiplied by RPM, so if an engine makes say a PEAK torque figure of 500 ftlbs at say 1,000 rpm (as an extreme example to prove the point) but then tails off to say 100 ftlbs at 10,000 rpm, the end result would be entirely different to an engine that made 500 ft lbs PEAK torque at 10,000 rpm.

These figures are unrealistic but hopefully get the point across.

The torque curve of an engine depends on numerous factors, so 2 SLIGHTLY different engines, could well produce higher or lower torque figures, in conjunction with higher or lower power figures and any combination thereof.

torque in lb/ft is always the same as horsepower @ 5252rpm(where the 2 lines intersect on a dyno print out), so if your 4.4 made its peak torque @ 3500rpm, the torque line would have fallen by the time it intersects with hp @5252rpm. And if your 4.0 made it's peak torque @ 4500rpm, it would still be reasonably high. Hard to explain but in short,the answer is yes, you can have different torque but the same horsepower.

When I stroked my engine from 5.0 to 5.8, I had the same torque but gained 70rwhp, the reason for that was I put a bigger cam in at the same time which pushed the peak torque up the rev range. The torque I would of gained by stroking was lost by the bigger duration camshaft, but increased hp substantially.

Paul

Forget about Torque vs Horsepower Richard, instead of that throw this subject into the discussion; transient response.
Transient response is the amount of time required for an engine to accelerate from point A in the powerband to point B.
We all want an engine that accelerates like mad from A to B right?

Well, a man called Larry widmer took this principle and spent close to 30 years developing racing engines to the next level and produced a thing called the soft head.
This soft head technology allows you to increase the break mean effective pressure in the combustion chambers to insane levels and at the same time virtually eliminate detonation.
Larry admits they regularly deliver engines to customers not knowing what horsepower, torque, static compression it has. They simply concentrate on transient response because in their eyes this is the single most important thing of an engine.

Link: http://www.theoldone.com/articles/The_Soft_Head_1999

There`s also lots of info on this matter in the archive and article sections. It certainly was an eye opener for me.

steam engines produce maximum torque at 0 rpm.

(glad to help)

think of it this way... you are trying to undo a tight bolt, you have a 1m long bar on it and apply 100N force. torque = 100Nm you put a 2m long bar on it and apply 100N force torque = 200Nm.
you have increased the torque but the force is the same. power is the rate of doing work.

Torque is how big your hammer is, Power is how often you hit the nail


(i'll get my coat, i'm going back to lusting after SB75 kits......)

Yes and no!

Yes... if you were to look at the entire operating range of the two example engines that you mention, you absolutely will make more hp at every point that the higher torque engine does better.

No... this does not necessarily mean that you will make more peak hp.

If this or none of the other explanations above make it clear, I can try and explain it a different way!