Dyno Results inside! (and questions)

[Jimbo]

So had my car dynoed earlier, had a mate take it in for me anyway
Apparently the operator wasnt happy with no rev counter and basically said the results wouldnt be the most accurate, he took some settings from my mates print out.

Anyway pulled 156bhp which is fine
And only 198ftlbs

Now im definitely dubious of the torque reading. Does anyone know the reason they cant be accurate with out the rev counter??

Cheers

[silverzx]

Regardless of your questions it looks like a pretty nice curve to me.

[toseland]

158,, there would be other bulges if mine was pushing that sort of power.. =D

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At a given RPM the full load torque of the motor is calculated thus

T = [HP x 5252] / rpm

T = torque (in lb-ft)
HP = horsepower
5252 = constant
rpm = revolutions per minute


basic calculation says you should have 221ft/lb of torque at 3705RPM, but thats just based on his calculation

it is also the reason that on EVERY SINGLE dyno run, the torque will also drop below the HP at 5252RPM

so you need to know the exact RPM of the engine to work out the actual torque for the given HP, hence not having a tac, would cause the operator issues.

[mr_fish]

would of thought you would be going faster than 105mph at 5400rpm?

[Jimbo]

I know mark, still cant see him revving it that hard, generally sound pretty harsh after 5k

Cheers toseland for info, makes me feel a bit better

[Ruan]

Well, with 198lb.ft I'd say that's actually a good result...

Does your car do 5420RPM though whilst under heavy load? I'm going to say it won't do that RPM with load on the engine and wouldn't make that much power up there, if anything your power figure will be slightly up from actuality.

You need to understand that the torque is what they're reading - the measured torque IS accurate unless their drivetrain loss equation is wrong... Which it usually is... Just take the ATW figure and add about 17% on - their drivetrain calculation is about 19%, so again, your torque figure is actually up...

If I do a quick bit of mathematics to give you an ATW figure - if we take your 19.11% drivetrain and rotating mass loss figure - I'm going for the highest percentage I can get to give you the biggest results () - I'm also going to use the uncorrected values because ISO/DIN barometric correction IMHO is bullshit, especially on turbo engines.

198.7 (Lbf.Ft) - 37.95 (drivetrain loss max) = 160.7 Lbf.Ft ATW (peak)

They reckoned on your power ATW being 126.5HP.

That's starting to sound quite like it, take the Torque produced at peak power which to me looks about 174Lbf.Ft ATF

So 174Lbf.Ft ATF - minus our 19.11% drivetrain loss equals 140.75 Lbf.Ft produced at peak POWER.

Peak power was made @ 4455RPM (we're going to have to assume this figure, sounds a little high to me)

So calculation for power is (Torque(Lbf.Ft) / RPM) * 5252 = (140.75 / 4455) * 5252 = 165.93HP ATW.

So even if your drivetrain loss is slightly more than originally thought... If you don't know what RPM it was done from, you simply can't tell - this is why chassis dynos are such crap!

For the record - my dyno results I corrected with 15% transmission losses - that's the standard for FWD cars, it's near IMPOSSIBLE to measure drivetrain loses, you can estimate the static losses, but not dynamic... If you want to compare your results IMHO just correct at 15% and then they're comparable - that means that the power your car puts to the road is measured in the same way as my car... Therefore your results are comparable - if I go for a 19% transmission loss, I'm making like 190hp!

[Ruan]

basic calculation says you should have 221ft/lb of torque at 3705RPM, but thats just based on his calculation

Not so - you're confusing peak power and peak torque - two very different things.

He was making 174Lbf.Ft at peak power ATW.

[Jimbo]

Wow! Cheers ruan you always confuse me

My mate made more torque on his t2
And im considerably faster than that?

[toseland]

basic calculation says you should have 221ft/lb of torque at 3705RPM, but thats just based on his calculation

Not so - you're confusing peak power and peak torque - two very different things.

He was making 174Lbf.Ft at peak power ATW.

i just thought about it, i pulled the RPM for peak torque, and used the peak power as calculation (which wasnt 3700, it was 4455 rpm) so the figure quoted is correct, however might not be accurate.

[Ruan]

I think what you're trying to say is - if he made peak power at 3705RPM - then he should have 221lb.ft there - however he made peak power at 4455rpm - therefore he has 175ish at peak power (btw, that's head maths, not calculator maths, CBA)

[Ruan]

And remember yes - a GT15 will make more bigger, laggier, older turbo...

Power = (Torque / RPM) * ~constant~

Notice:





Notice the Diesel is making over *NINE HUNDRED* pounds-feet of torque, but "only" 500hp...

The Nissan GTR is only making 500 and something lb.ft, but is making close to 700hp - this is the difference between torque, RPM and power...

Liken it to bench pressing...

Torque says - I can bench press 250kg once.

RPM says - I can lift *a* weight 500 times a minute.

POWER says - I can lift 250kg, 500 times per minute.

That is the difference... So all the plonkers who say "I don't need power, I've got lots of torque" - means that they don't understand how any of this works.

[mikey b]

Just out of intrest were is the gt 15 bit from jimbos is a gt1752 of a petrol would the petrol one have much difference on a dyno can vouch for jimbo that this think goes f***

[Piggy]

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Does seem a low figure for a GT17 mind

[mikey b]

I spoke to the lad that took it for jimbo and I think the dyno operator was taking it easy as he really did not like the fact that he had no rev guage but who know over 150 so pretty good and it getting broken in the next few weeks

[Ruan]

My point is... Smaller turbos equal more torque...

Bigger turbos make higher power at higher rpms... My point was that a gt15 will make higher torque figures than older t2s...

I. E. A larger petrol turbo is likely to produce much less torque...

[silverzx]

Woah woah woah.

SMALLER TURBO > LARGE TURBO!

[Piggy]

aaahhhh....but just....well, just GTB /thread

[Ruan]

Smaller turbo will make more torque than a bigger turbo at a lower RPM given the same power output - yes

More like:

CORRECTLY SIZED TURBO > FAT BLOWER.

For those who tl;dr:

The torque is right, horsepower may be off.

[Piggy]

Still seems low on torque, at whatever RPM. A GT17 should do better than that surely.

[Ruan]

End of the day, it's off a 2.0 LPT petrol... Was never designed to spool at low RPMs or move a vast quantity of air at high pressure, I have experience of this turbo remember! It's got a compressor designed for lower boost levels (sorta 7psi) and a turbine designed to move lots of air without causing much restriction.

Hence why a GTB2056VL will literally kick the pants off an older 2256, because it's newer, more appropriate for the engine, more appropriate for the application...

[Piggy]

ahhh, I missed that it was a petrol GT17 originally

[mikey b]

End of the day, it's off a 2.0 LPT petrol... Was never designed to spool at low RPMs or move a vast quantity of air at high pressure, I have experience of this turbo remember! It's got a compressor designed for lower boost levels (sorta 7psi) and a turbine designed to move lots of air without causing much restriction.

Hence why a GTB2056VL will literally kick the pants off an older 2256, because it's newer, more appropriate for the engine, more appropriate for the application...

Agree but think it's about time you put ya know how and brains into a big bhp xud not much left of the chronic boost team at the shows anymore

[Mac22]

I took it to the garage .. The guy wasn't pleased there was no rev counter and he basically based it on my xud with t2, I told him he has a gt17 bigger turbo and I'm guessing he did what he could, but he couldn't go all out with no rev counter. Tbh my reading when I did mine day before read he was doing 4605rpm at 91 mph.. And 2555 at 50.7 mph

[Frosty]

Think they do the power runs in 4th gear though so that will explain the rev against speed

[Ruan]

End of the day, it's off a 2.0 LPT petrol... Was never designed to spool at low RPMs or move a vast quantity of air at high pressure, I have experience of this turbo remember! It's got a compressor designed for lower boost levels (sorta 7psi) and a turbine designed to move lots of air without causing much restriction.

Hence why a GTB2056VL will literally kick the pants off an older 2256, because it's newer, more appropriate for the engine, more appropriate for the application...

Agree but think it's about time you put ya know how and brains into a big bhp xud not much left of the chronic boost team at the shows anymore

Meh, time and money my friend...

[mikey b]

End of the day, it's off a 2.0 LPT petrol... Was never designed to spool at low RPMs or move a vast quantity of air at high pressure, I have experience of this turbo remember! It's got a compressor designed for lower boost levels (sorta 7psi) and a turbine designed to move lots of air without causing much restriction.

Hence why a GTB2056VL will literally kick the pants off an older 2256, because it's newer, more appropriate for the engine, more appropriate for the application...

Agree but think it's about time you put ya know how and brains into a big bhp xud not much left of the chronic boost team at the shows anymore

Meh, time and money my friend...

Yep know what ya mean would be be good if you and Darren got an epic derv out again but know what ya mean bout money mines cost me far to much you going to make an appearance at pugfest

[Niall]

This thread is actually really interesting! Cheers Ru, learnt quite a lot from your explanation.

That is the difference... So all the plonkers who say "I don't need power, I've got lots of torque" - means that they don't understand how any of this works.

Ive heard this a lot and its always confused me. As far as i understand it, the more torque you have, the more power it feels like you have (i mean the more of a kick in the back of the head you get when you boot it) but I've learnt this just isn't the case. It may feel quick due to a boot of torque but in reality, its not. Like for instance last year i had a VW tiguan which FELT like it had some power and a shit load more than a 6. In reality once i pulled up next to Ed at the lights in his almost standard 6, i got dicked all over big time and i had 70lbft more torquez.

[toseland]

thats the thing.. horsepower is what sells cars.. torque is what wins races, as torque is a measure of the actual turning force about a pivot,

Torque is what is responsible for getting you there faster, (0-60, 30-70 etc) Horsepower is just a nifty measurement to give the engine itself some context (they go hand in hand however)

you have to appreciate tho, that engine specs on paper mean jack really unless its the same car, with the same gearing, under the same conditions, at the same time, etc etc

he might have had a lower power band, closer gearing, etc etc.. but his GTi would have struggled 4up with luggage where i am betting the tiguan would have felt almost identical as it did when empty.. THATS the beauty of torque

[Ruan]

thats the thing.. horsepower is what sells cars.. torque is what wins races, as torque is a measure of the actual turning force about a pivot,

Torque is what is responsible for getting you there faster, (0-60, 30-70 etc) Horsepower is just a nifty measurement to give the engine itself some context (they go hand in hand however)

you have to appreciate tho, that engine specs on paper mean jack really unless its the same car, with the same gearing, under the same conditions, at the same time, etc etc

he might have had a lower power band, closer gearing, etc etc.. but his GTi would have struggled 4up with luggage where i am betting the tiguan would have felt almost identical as it did when empty.. THATS the beauty of torque

Not necessarily - That's why you have a gearbox. That's what affects torque to the wheels - that's why a Honda VTEC motor making 200hp is still accelerating as fast as a Diesel motor making 200hp at the same road speed - it's just that usually the Diesel engine has a more usable powerband than the VTEC motor - the actual torque *figure* is nothing to do with it, that's the curve.

It's the same reason that if you wanted you could use a 200hp VTEC engine spinning at 9000rpm but only making 116lb.ft to apply 500lb.ft torque to an object a gearbox gearing it right down - yet you can also use a big arse lazy 200hp Diesel motor that makes say 900lb.ft torque at 1150rpm, but gear it up and it'd also apply that same 500lb.ft torque to an item - they're both making 200hp - just at different engine speeds.

The speed of the output shaft of the two engines would STILL be spinning at 2100RPM.

Always.

This proves that one engine is not better than the other in terms of work done at one given power output.

One engine is not doing more work than the other - the Diesel won't be applying more torque to the final shaft, the Honda wouldn't have any more problems with it utilising the 500lb.ft...

It's just that the Honda will be using way more fuel, you're spanking the shit out of it, it's not going to last, it's hard to keep it up there... The Diesel is doing 1150RPM! It's going to sit there all day doing that!

OK my point is extreme as you can see, but you can see it's not just peak figures... It's all about the curve.

[toseland]

haha yeah i appreciate that, thing is, a "proper" torque and HP discussion is beyond the scope of *most* people (and i dont mean that in a negative way, i am talking about advanced physics and theories, vectors, angles, frictional co-efficients.

i like nice, smooth curves above 300 lol