20bhp off std on the rollers - need ideas

[Kevin Bacon 5]

Not necessarily. Since HP is the *rate* of work and torque is the *amount*, you still need sufficient *power* to sustain that amount of work at any given rpm, especially high rpms.

 

In an ideal world, torque and power would be equal and climb at a perfect 45 degrees on the plot.

[PhatVR6 0]

who cares about HP. just take it down the 1/4mile and time it.

 

mine felt alright on the road, but when it ran a 14.9 1/4 I knew it wasn't running right even though it felt pretty quick on the road. got it fixed, and now I'm dying to run it again to see how much difference it's made.

 

sure, a rolling road would have told me it was down on power too, but it'd have probably worked out more expensive, and wouldn't have been as much fun either.

 

mine runs great now, despite a slight flat spot at 4000rpm and a rev limit at 6600rpm, but I know a chip will fix that.

 

And strictly speaking I should have less transmission losses, as I'm using synthetic fluid and a semi straight cut gearbox (i.e. less friction between the teeth).

 

Saying that, I do have a dyno day planned next month, so power and torque graphs and figures coming soon!

[davidwort 0]

Not necessarily. Since HP is the *rate* of work and torque is the *amount*, you still need sufficient *power* to sustain that amount of work at any given rpm, especially high rpms.

 

In an ideal world, torque and power would be equal and climb at a perfect 45 degrees on the plot.

 

I agree but in even easier to understand language, how about:

you need good torque over a wide rev range or area under the curve on the rr graph?

 

 

David.

[dr_mat 0]

Ok, perhaps I should have clarified my point:

 

"But at the end of the day, the torque curve is the one you're interested in, power is secondary."

 

this applies for acceleration performance at speeds well below the point when wind resistance becomes significant.

 

Top speed is more or less purely dependant on power output set against coefficient of drag (i.e. wind resistance). (Assuming logical choices have been made in terms of gearing and so on of course.)

 

(Being pedantic: torque is of course the Force applied, or at least the potential force, not the work itself. Force*distance is work.)

 

For most people with Corrados on British roads, the wind resistance factor doesn't become significant most of the time I'll bet. (130mph+ day to day? You must be insane!)

 

So in other words, I'm not disagreeing with you Kev, and you're not disagreeing with me. (Just for those that claim we always argue..) ;)

[Kevin Bacon 5]

So in other words, I'm not disagreeing with you Kev, and you're not disagreeing with me. (Just for those that claim we always argue..) ;)

 

LOL....

 

We need to get rid of that reputation ASAP!

 

And keep your eye on that cheeky wee skamp Tom because he's already produced a 'Kev n Matt' picture based on the two grumpy gits from the Muppet show. Expect it to appear on here very soon.......

 

P.S Steering is still superb...... guess it was the rack then :wink:

[dr_mat 0]

P.S Steering is still superb...... guess it was the rack then :wink:

 

That's what I wanted to hear.. :)

[Henny 0]

yup, that's the equation dr_mat (although it's sometimes said to be 5252rpm :? )

 

What you ideally want is a nice steady high torque figure from idle all the way upto redline... none of this pratting around with gaining torque through the revs, or sudden jumps in torque as V-TEC kicks in etc etc etc... just a constant wave of torque.... 8)

 

BHP doesn't really give you a reasonable idea of what an engine is capable of... An electric motor as used on a train produces almost NO torque at 5250 rpm so has a stupidly low BHP figure at that point... however, at almost 0 rpm, the torque it can produce is HUGE but this also gives a very low BHP figure... If your car can out pull an unladen train, I'm not gonna mess with it! ;) :lol:

 

Even if you had torque and BHP graphs for 2 engines, you still wouldn't know which was fastest on a road unless you added a time line in there too to show the accelleration... I was sooo suprised how much faster my car felt before I got the rolling road setup compared with how it was originally, the reason behind this was the difference in speed it goes up through the revs. It was actually running quite badly until the chip was written, and on the way home I just couldn't stop laughing! :D 8) the acceleration through the revs is just a revalation compared to how it was before! :D

 

Gearing also has a huge amount to do the way a car drive (as Phat will preach to anyone who will listen, and rightly so! ;) ) The altered ratios in my car mean that the acceleration comes as a constant wave in each gear, and you hit the next gear smack bang in the peak torque range and off you go again! :D I can't wait to see what she'll do on a set of rollers, track and strip... should give some of you lot some idea as to how things don't always equal out with big BHP numbers... ;)

 

It's all a series of compromises which you need to get right to make sure that you get the maximum torque, BHP and acceleration out of your engine with a touch of reliability thrown in too! ;) :D

[PhatVR6 0]

too true. my old golf, with only 207BHP was a good second quicker than most 250BHPish supercharged VR6's I've seen.

[PhatVR6 0]

no one has mentioned traction issues yet either..............

[Scott 0]

no one has mentioned traction issues yet either..............

 

True good point... I have traction issues with my Pug 306 TDi that has 145lbft torque at just 2200rpm... does that count? :lol: :lol:

 

Mucho wheel spin......

[dr_mat 0]

We felt that traction issues were even further OT than discussions about power, torque, gearing and wind resistance... ;)

[pablo_vr6 0]

surely a measure of bhp is still useful to say if a car is doing its power or not? That was the purpose of the run to see what the baseline was and if action needs to be taken.

 

it wasnt to see if i could faster than my mates car - I can race him and find that out ;)

[Kevin Bacon 5]

Yeah I agree, if VW quote 190 at the fly then it would be nice to see that, not 171!

 

K

[dr_mat 0]

Yep, of course. Just take the "flywheel" figure with a large pinch of salt and use the "wheel" figure as the basis for your discussions.

[VR6 0]

So in other words, I'm not disagreeing with you Kev, and you're not disagreeing with me. (Just for those that claim we always argue..) ;)

 

LOL....

 

We need to get rid of that reputation ASAP!

 

And keep your eye on that cheeky wee skamp Tom because he's already produced a 'Kev n Matt' picture based on the two grumpy gits from the Muppet show. Expect it to appear on here very soon.......

 

P.S Steering is still superb...... guess it was the rack then :wink:

 

Well I'd hate to disappoint.........lol

[Scott 0]

LOL LOL :lol:

[dr_mat 0]

That's nothing like me! Ridiculous... :)

But I did always admire Waldorf and Stadtler's sense of humour.... ;)

[stevemac 0]

Yep, of course. Just take the "flywheel" figure with a large pinch of salt and use the "wheel" figure as the basis for your discussions.

 

That sentence should have been close to the top of this thread.

 

The only noticable thing is how much torque at the wheels & where it occurs in the rev range. Anything else is just pub/forum talk !!

[Kevin Bacon 5]

LOL, I'm glad Matt is the short grey haired one :lol: