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Discussion Starter · #1 ·
When I hear forged pistons ,big end bolts,new conrods I think big outlay !!
This is for the guys who want more horses.
What about more torque?
Would I need all this forged business ,upratted con's better bottom end?
Could't I just put in a MOTEC managment ,a 34 mm restrictor.?bigger cooling requirements.
and get some fast ecceleration.
What would I expect to loose off top end?15 mph aint much I can only do 140 now.
I would need a good clutch I know this .
I,m interested in going the other way from Bhp,most talk is of BHp, but a fast excelerating car isn't all down to horses.
Rally cars are quick ,but not alot of top end.
If you want to go quickly surely the torque aspect is more important.
Some one explain a little .
I dare say all go hand in hand to a point,but thats bollx cause I know of a group N E3 with nearly 400lbft torque,running 280 ish horses.


cheers

Paul s
 
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Discussion Starter · #2 ·
Paul,
BHP is torque x RPM , engines produce torque not BHP , BHP is the rate of work done.

Torque is the thing that shoots u up the road , so if yr motor knocks out 400 Ft Lbs it will still stress the internals to the same extent even if only developing 280-300 BHP.
 
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Discussion Starter · #3 ·
Evoboy,

Do you reckon that big end bolts the first way forward?
All the forged pistons ,lightened con rods etc ,once I get around 320 bhp although the torque figure may be around 290 lbft.
I think what I'm asking is I know roughly how to get more Bhp ,but its turning things on its head and getting the torque increase with out pushing the HP much higher.
There must be a manner in which this could be done.The only way I have read about is with a management system and turbo restrictor,as they do on the rally cars.
But as most gradually increase the HP. How could I gradually increase the torque? with out upsetting the increase in HP.
 
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Discussion Starter · #4 ·
Shorty,

Using Evoboy's formula of bhp |EQU| torque x revs(which is right), if you up the torque then you will automatically get more power at any given revs. I think what you're trying to get at is restricting the maximum power which means restricting the torque at high revs but not in the mid range. I think this is what the restrictors on rally cars do, although I'm not sure if there are other ways to skin this particular cat.

Steve.
 
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Discussion Starter · #5 ·
Actually,
- Maximum acceleration at any speed occurs at the HP peak.
- Maximum acceleration in any gear occurs at the torque peak
- HP |EQU| torque * RPM / 5252
- torque |EQU| HP * 5252 / RPM
- torque |EQU| HP at 5252 RPM

(torque is measured in ft-lbs to use 5252 as the magic number)

This is why on a print out from a rolling road torque and bhp should cross at 5252 revs!

http://g-speed.com/pbh/torque-and-hp.html for a good primer on torque and hp.
 
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Discussion Starter · #6 ·
Hey you know what? That fits in with my RR graph! http://www.ltregister.f9.co.uk/graphics/happy1.gif border|EQU| 0 align|EQU| absmiddle >

I knew there was a relationship between power and torque, but could never remember what it was. Thanks!
 
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Discussion Starter · #7 ·
mine too chunky.

where is your peak torque?
mine's around 3,500 rpm which seems a bit low, espescially after reading the article mentioned by howardb
 
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Discussion Starter · #8 ·
Peak torque comes in at 3840rpm on my printout, although as they say in magazines, at least 90% of that is on tap from 2750 to 6000rpm
 
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Discussion Starter · #9 ·
Thanks Howard,one long explanation ,but worth the reading,and printing off for safe keeps.
Perhaps just another gear box may do the job.
I can now play around with some figures.Although I will have to read the damn thing 20 times before it sinks in.BIT THICK ON THE SCIENCE U SEE.
Any way glad you came up with this .

cheers

Paul s
 
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Discussion Starter · #10 ·
Hey Howard !
Just checked my printout from weekend and yes indeedy .... they both cross at just over 5000rpm.....Amazing http://www.ltregister.f9.co.uk/graphics/happy1.gif border|EQU| 0 align|EQU| absmiddle >

Does that mean that my figure of 341bhp and 294lbs must have been correct ? [img]http://www.ltregister.f9.co.uk/graphics/happy1.gif border|EQU| 0 align|EQU| absmiddle >
 
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Discussion Starter · #12 ·
I think this just goes to prove how unreliable rolling roads are. There is a good write up about rolling roads in the March issue of CCC magazine. One interesting thing that they say is the biggest rolling road loss is the car tyre. The tyre is compressed in two places by the rollers. The tyre construction, diameter and pressure all have an influence on rolling road losses and therefore can affect power output readings .

C2GSR: The other thing is that if the power and torque lines do not cross here (rpm of 5252) on the graph then somebody is telling you porkies . I recommend you visit your local WHSmiths and have a quick read!
 
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