ok since hp=tq*rpm/5252 it would be safe to say that if i have hp figures and rpm then i can figure out the torque for a given rpm?

if hp at 4500 rpm's is 349 then it should be 349=tq*4500/5252 which equals 349*5252/4500=TQ? is that correct?

 

Well if my algebra is correct then yes you did that properly...

 

your algebra is correct

 

well that just made my day... that means i'm putting out over 400 lbs of torque. woot woot

 

So you have 50 more torque than your whp? Is that correct?

 

well the dyno session got cut short cause of head lift and on this run it was only revved to a little over 5k.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by flip1199 &raquo;</TD></TR><TR><TD CLASS="quote">well that just made my day... that means i'm putting out over 400 lbs of torque. woot woot </TD></TR></TABLE>

I don't believe that you can take one formula and apply it to all engines. Your algebra was right, but I don't see how there is a universal formula for power output of different engines.

 

Is it common to have that much more torque than hp on a boosted motor?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by frostman79 &raquo;</TD></TR><TR><TD CLASS="quote">Is it common to have that much more torque than hp on a boosted motor?</TD></TR></TABLE>
it all depends on what set-up you have

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IHateJDM &raquo;</TD></TR><TR><TD CLASS="quote">

I don't believe that you can take one formula and apply it to all engines. Your algebra was right, but I don't see how there is a universal formula for power output of different engines. </TD></TR></TABLE>

Well the universal formula for horse power is "(Torque x Engine speed) / 5,252 = Horsepower" this formula applies to ALL engines. so i don't see how it wouldn't work with my setup....

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by frostman79 &raquo;</TD></TR><TR><TD CLASS="quote">Is it common to have that much more torque than hp on a boosted motor?</TD></TR></TABLE>

Nope, not for a honda. but i'm sure if my head didnt lift and i was able to keep revving my hp would have been higher.

 

V8's usually make more torque than HP, even over 5252 rpms, where 4 cylinders usually make more HP than torque. By the formula using one constant (5252), it's assuming the properties of all engines are the same. Just look at a b18c1 vs a b18b. The b18b is capable of more torque mainly because of a different rod/stroke ratio (among other things), let alone considering an example where there are 8 cylinders vs 4. I'm sure the formula is a decent estimate, but I wouldn't go running around telling people that you made over 400 ft/lbs of torque until you have a dyno chart (pull all the way to redline) to back it up.


Modified by IHateJDM at 9:56 AM 6/16/2005

 

It's not a "decent estimate" - it's the way HP is measured, whether it's a weed whacker or a Civic or a 747.

If he made 349hp @ 4,500 rpms, he was making 407 ft/lbs. of torque at that point as well. No ifs, ands, or buts.

So congrats. Now fix it and get a full dyno done . . . .

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IHateJDM &raquo;</TD></TR><TR><TD CLASS="quote">

I don't believe that you can take one formula and apply it to all engines. Your algebra was right, but I don't see how there is a universal formula for power output of different engines. </TD></TR></TABLE>

Yes, there is. There is a fundemantal mathmatical relationship between horsepower and torque. I don't think you can directly measure horsepower (well, not in rotational form, linear form is a different story); first a torque value is obtained by a dyno then converted to a horsepower figure via the above formula somewhere.

Additionally, below 5252 rpm any IC engine's torque number will always be higher than its horsepower number, and above 5252 rpm any engine's horsepower number will always be higher than its torque number. At 5252 rpm the horsepower and torque numbers will be exactly the same . . . so the hp and torque lines on a dyno plot will always cross at 5252 RPM's.




Modified by red92s at 4:25 PM 6/16/2005

 

HP is a function of Torque. Torque = lb/ft. This is a definitive measurement. HP = the amount of work in a given time.. and to figure this out, you use the torque formula listed above.

HP = (torque * RPM) /5252

This is also the reason *all* dyno's cross at 5252 RPM's. After that, you'll have more HP than torque. There is no way around it, it's a math formula to figure out HP.. there is no real physical measurement of HP like there is torque.

Now your peak torque on some engines may be higher than the peak HP, most likely caused by a massive drop in torque right before and continuing after the 5252 RPM mark, or because the engine doesn't rev very far past 5252... but either way after 5252 the engine *will* dyno a higher HP than torque. Below 5252, the torque *will* be higher than the HP. At 5252, they *will* cross.

It's the same reason if you had two engines with identically and ideally flat torque curves, and you dyno'ed them but one was limited to 8200 rpm, and one managed to rev out to 10,000 RPM, one would read a torque of let's say 200 with a HP of 312 @ 8200 RPM, while the other car which also had a flat torque curve of 200 would have a peak HP of 380 @ 10,000.

Best way to see the "fomula in action" is check out a couple of dyno's. I know some dyno's are incorrect, such as my brother's which showed a crossover point of almost 6000, which is impossible since HP is a fixed math formula, but you'll get the idea of where they cross and how HP is calculated based on the torque.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjr162 &raquo;</TD></TR><TR><TD CLASS="quote"> I know some dyno's are incorrect, such as my brother's which showed a crossover point of almost 6000, which is impossible since HP is a fixed math formula, but you'll get the idea of where they cross and how HP is calculated based on the torque.</TD></TR></TABLE>

that's one thing that did throw me off. i've seen a lot of hp/torque numbers that don't fit the model, but I jumped to the conclusion that the formula was wrong, instead of the more logical idea that they dyno is off. Thanks for the correction .

 

There are some god damn morons in this thread.

It doesn't matter if you are comparing a steam-powered horseless carriage to a B18C5.

HP=torquexRPM/5252

You will NEVER EVER EVER IN A ELELVENTY BILLION YEARS have ANY kind of rotational engergy, out of any engine on earth, making more torque then HP above 5252. Similarly, you will not have more HP then torque below 5252 RPM.

At 5252 RPM, they will always be the exact same. ALWAYS! NO DYNO SOFTWARE ON EARTH WILL EVER EVER SPIT OUT A DYNO WHERE THIS IS NOT TRUE.

<FONT SIZE="10">EVAR</FONT>

Again, there is no exception to this. Ever. If you think otherwise, you read the dyno wrong.

The laws of physics that govern this universe do not care if you have M4d VTak. yo.

IF you see the specs on an engine, and peak torque is higher then peak RPM, ALL that means is that the torque peaks at a low RPM, and then falls off rather steeply above 4000-5000 RPM. It does not mean that you have some crazy *** weird setup, or that you are a mullet-loving IROC-Z driving redkneck, or that you need to lengthen the injector pulse another milisecond to run 9's.

&lt;--- in a bad mood so **** off!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Greyout &raquo;</TD></TR><TR><TD CLASS="quote"> NO DYNO SOFTWARE ON EARTH WILL EVER EVER SPIT OUT A DYNO WHERE THIS IS NOT TRUE.

<FONT SIZE="10">EVAR</FONT>

Again, there is no exception to this. Ever. If you think otherwise, you read the dyno wrong.
</TD></TR></TABLE>

You should never post without reading the entire thread.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Greyout &raquo;</TD></TR><TR><TD CLASS="quote"><FONT SIZE="10">EVAR</FONT>
</TD></TR></TABLE>
I have seen many dynos that don't match the model, as stated in my previous post. I'm not reading them wrong. The dyno plots i'm referring to were obviously off due to mechanical or software error on the dyno's part. That was the entire reason I doubted the formula.

 

You read the dyno wrong.

I will paypal you all the worlds riches imediately if you can post one dyno that is like that.

 

I agree with you 100%. The formula is solid, and you will never see torque numbers higher than hp numbers above 5252. Period.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">

I have seen many dynos that don't match the model, as stated in my previous post. I'm not reading them wrong. The dyno plots i'm referring to were obviously off due to mechanical or software error on the dyno's part. That was the entire reason I doubted the formula.</TD></TR></TABLE>

The reason you THINK you have seen dyno graphs that dont have the same HP and TQ #'s at 5252 rpm is because the scale for the graph might be different. The scale hp is on might be going by 10's and the TQ side of the graph might be going by 5's. This would cause the lines to cross at a different place but if you read the graph the actual NUMBERS for HP and TQ are the same at 5252 rpm.

 

no, some dyno's are just flat out wrong when printed to paper. My brothers, for example, which was done at tempest racing, crossed at almost 6000 RPM. This is the reason *he* also thinks that whole "they cross at 5252 always" rule isn't real. His dyno is mis-leading them. For one reason or another they are off. Maybe the listed "Torque" and "HP" are actually two other readings they mislabeled, or if the printout shifted things a bit high, but either way the dyno is doing exactly what the other guy and I are saying... it is lieing about the crossover point and is therefore incorrect.

 

you are talking about honda four cyclinder engines not a ford v-8 .... the difference in torque curves is greater from 4s to v8s it has to do with displacement efficencies of the engine --- a honda ivtec or vtec 4 banger makes more peak horsepower up top then it does torque -- period you will never see a 200-240 peak hp na honda engine hold anything beyond 160-164 ft. lbs. of torque... cause it has to do with peak power coming from the cam profile switch and not from the engine in general... that is why a v-8 which displaces 4.8 litres can have 300 whp and 320 ft. lbs of torque while hondas vtec trick does nothing more than increase the amount of air/ fuel being burned speeding up the process and making more power from this....

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjr162 &raquo;</TD></TR><TR><TD CLASS="quote">no, some dyno's are just flat out wrong when printed to paper. My brothers, for example, which was done at tempest racing, crossed at almost 6000 RPM. This is the reason *he* also thinks that whole "they cross at 5252 always" rule isn't real. His dyno is mis-leading them. For one reason or another they are off. Maybe the listed "Torque" and "HP" are actually two other readings they mislabeled, or if the printout shifted things a bit high, but either way the dyno is doing exactly what the other guy and I are saying... it is lieing about the crossover point and is therefore incorrect. </TD></TR></TABLE>

Post your brother's dyno sheet.

 

The only way your brothers dyno sheet doesnt cross at 5252 is if the scales are different on either side of the graph. Other than that i would say the guy that dynoed your brothers car just used MS paint to make a mock dyno graph

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by specialedition &raquo;</TD></TR><TR><TD CLASS="quote">you are talking about honda four cyclinder engines not a ford v-8 .... the difference in torque curves is greater from 4s to v8s it has to do with displacement efficencies of the engine --- a honda ivtec or vtec 4 banger makes more peak horsepower up top then it does torque -- period you will never see a 200-240 peak hp na honda engine hold anything beyond 160-164 ft. lbs. of torque... cause it has to do with peak power coming from the cam profile switch and not from the engine in general... that is why a v-8 which displaces 4.8 litres can have 300 whp and 320 ft. lbs of torque while hondas vtec trick does nothing more than increase the amount of air/ fuel being burned speeding up the process and making more power from this....</TD></TR></TABLE>

The issue has to do with where the torque increase falls because of the VTEC switch, which also happens to fall in the higher RPM range, which causes a higher mutliplier in the HP = (torque * RPM) / 5252, so of course the HP rating will be alot higher in a honda than the peak torque rating will be.

Also, I mentioned about the Dyno print outs can be "wrong"... wrong as in either mislabeled by the person running the dyno, or "wrong" in the aspect of different scales used between the two which would lead someone who didnt' know better to think the 5252 rule doesn't exist. I understand what you two (the last two posters) said, and its' the same thing I was trying to say