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Author: Subject: A question about dyno read outs
Shooter63

posted on 23/3/15 at 07:14 PM Reply With Quote
A question about dyno read outs

This is my first question post so please be gentle and if I've posted in the wrong place sorry

I've just picked up a sylva stylus and was given a dyno readout sheet with the paper work and something doesn't look right, the point where the torque and bhp lines cross is not at 5250 rpm?
I come from a bike back ground and always thought that if the lines didn't cross at that rpm then the dyno was out or something?
Can any of you fine chaps help?

Shooter63

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theduck

posted on 23/3/15 at 07:25 PM Reply With Quote
BHP and Torque are related, and as you say should cross at 5252rpm
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will121

posted on 23/3/15 at 07:53 PM Reply With Quote
Just looked at my 2 litre zetec ones in various states of tune and all cross at 5250, don't know why hopefully some one with more knowledge will explain
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Jenko

posted on 23/3/15 at 08:06 PM Reply With Quote
:-) check that the scale is not on the same axis....I suspect he torque is on a different axis :-)





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Alfa145

posted on 23/3/15 at 08:40 PM Reply With Quote
Just looked at my zetec graph and it crosses at 5250ish too. Post up a pic/scan of it and lets see as it might be looking at the wrong scale/axis?

Was it a just a power run or part of a tuning run?

[Edited on 23/3/15 by Alfa145]

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Ugg10

posted on 23/3/15 at 09:02 PM Reply With Quote
Surely this is dependent on the axis for power and torque being used. I assume from the previous comments that they may cross around this point if both rear wheel (or is it calculated fly wheel, that would also make a Difference) hp and torque lb.ft are plotted on the same numerical scale. If ether is on a different scale then they would cross at a different point.





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softfeet

posted on 23/3/15 at 09:33 PM Reply With Quote
Power (hp) = [Torque (lb ft) x Engine speed (rpm)] / 5252

Therefore at 5252 rpm, the power and torque figures (in hp and lb ft respectively) will be equal.

The constant 5252 is derived as follows:

One horsepower is defined as 33,000 foot pounds per minute.

33,000 / (2 x pi) = 5252

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will121

posted on 23/3/15 at 09:44 PM Reply With Quote
quote:
Originally posted by softfeet
Power (hp) = [Torque (lb ft) x Engine speed (rpm)] / 5252

Therefore at 5252 rpm, the power and torque figures (in hp and lb ft respectively) will be equal.

The constant 5252 is derived as follows:

One horsepower is defined as 33,000 foot pounds per minute.

33,000 / (2 x pi) = 5252



I knew someone would explain a logical reason

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The Black Flash

posted on 23/3/15 at 10:37 PM Reply With Quote
quote:
Originally posted by Jenko
:-) check that the scale is not on the same axis....I suspect he torque is on a different axis :-)


Must be this.

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HowardB

posted on 24/3/15 at 08:18 AM Reply With Quote
This forum is fantastic,. learn something new everyday





Howard

Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)

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jeffw

posted on 24/3/15 at 08:42 AM Reply With Quote
frequently this is a display issue on the graph or the power runs where in Nm/PS etc, ie not HP which is where the the constant is derived from.

Anyway....post up the graph and lets have a look.

[Edited on 24/3/15 by jeffw]






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will121

posted on 24/3/15 at 05:44 PM Reply With Quote
quote:
Originally posted by will121
Just looked at my 2 litre zetec ones in various states of tune and all cross at 5250, don't know why hopefully some one with more knowledge will explain


Here's one of mine


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Shooter63

posted on 25/3/15 at 09:56 PM Reply With Quote
Thanks for all the answers, I've been in touch with the dyno operators who have sent me a read out, the car made 159.5 bhp on the rollers with the torque crossing at 5250 rpm.
So alls well that ends well.

Shooter63

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coozer

posted on 25/3/15 at 10:01 PM Reply With Quote
I seem to remember some big cc v8 readouts having a massive flat torque line that was constantly above the horsepower line?

Sure my 430 HP daf truck makes a fairly constant 1200ft/lbs of torque at 1300rpm...





1972 V8 Jago

1980 Z750

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