Hi Guys,

Some of you have helped me out (as I'm in the UK) with questions about Vortech S/C which is set to be installed soon

Chatting on 350zuk.com, I raised a comment about US often quoting RWHp whereas we Brits like the crank Hp - which can't actually be measured on a rolling road dyno but is scaled by a 'fudge' factor of about 17%.

Got the following comment back:

"Thats all good and well, but the figures that the US guys claim are WHP are actually equivalent to our crank figures. They are renowned for inflating figures in the US. How could one US APS TT zed produce 420 at the wheels at the same boost pressure as mine?? impossible. Spoke to Peter at APS about this, and he agreed with me. All US figures are actually comparable with our flywheel figures."

This surprised me especially the Peter Luxon bit. Care to put the record straight.

 

seems like a pretty simple answer to me. not sure what the difference could be. i highly doubt that a u.s. registered car gets a dose of "team america" and makes more power, hahahahha. to me it seems alot better to get the figures from the tire and alot better to tune the motor in that fashion also. about the only guys still trying to use crank hp is just the engine builders themselves. getting a whp figure and guessing your crank hp with 17% makes no sence.
maybe you guys need better tuners there, hahahha. many dyno printouts have been posted here, check it out.

 

edited my opinion

 

Well, it's probably that we mostly use DynoJet numbers and they may have used load based type dyno's number. So our hp numbers look inflated.

 

It does make sense to use 17%, as this is the drivetrain lose percentage. So if you make 400rwhp, then take 400/.83 and this equals 481 crank HP.

 

I've been away from my PC for a bit and on re-reading this post, it might appear that I posted to try to be controversial - given Booger's 'Edited My Reply' for example.

However, that was NOT my intention. It is in fact my belief that this view on UK vs US dyno figures which is often perpetuated in the UK is an URBAN MYTH.

When I posted for first time about a month back I followed through an entire history of a Vortech-installed car's posts (it was SungNamZ's actually) and post initial install his WHp figures of about 320-330 are entirely consistent with the 370-380 Crank Hp figures often quoted in the UK.

I am no expert on Rolling Road Dyno's but they are bits of kit which are presumably all calibrated. Like a post above, I cannot see in whose interest it would be to inflate figures - in the long run.

Just my 2 pence (2 cents!)

 

The comment doesnt make a whole lot of sense. Dynojet numbers are most common in the US, and those are definately measuring WHEEL hp...not crank hp. For instance, when I had my bone stock 350Z, it made 226whp, although the engine is rated at 287 CRANK hp. That seems convincing enough for me.

 

I deleted my post becuase I feel that DynoJet numbers [ whats used here in the USA ] are closer to crank HP . Most Vortech guys saying they have 400whp are actually closer to 345 to 365whp on a Load base dyno . And guys that dyno on Load based add 12 to 17% to make thier numbers closer to DynoJet numbers . Its hard for people to get away from the higher numbers...bragging rites..you know

 

Cheers Booger. I didn't realise that with DynoJet - I think we do use load-based dynos here in the UK. Having said that Sharif's Dynojet number of 226 RWhp stock is almost exactly same as our guys get here on load-based dynos - in fact 233 is about the norm. So its still a bit of a confused picture.

Below is a link which I have used to gain some insight - its from the website of the only (yes the ONLY!!) APS installer in the UK:

http://www.g-force-motorsport.co.uk/...surement2.html

Thanks for your input - its interesting to understand different perspectives

 

Booger, I think some clarification is in order.

A dynojet does not measure crank hp, and neither does a load based dyno, such as Dyno Dynamics or Mustang. Both of them are measuring wheel hp, but measure then in a different manner.

If a dynojet measured crank hp, then the guys with stock Z's would be dynoing close to 300hp. As mentioned, I dynoed 226whp when stock, on a DynoJet. That sounds precisely like whp to me.

The reason some operators scale their load based dyno numbers, is to make them comprable to the industry standard dynojet numbers. There is nothing wrong with this, as long as its disclosed. But both are still measuring whp and not crank hp.

 

I don't believe Booger was saying that Dynojet measured Crank HP just that the Dynojet numbers (wheel HP numbers) were more like Crank numbers (i.e. inflated) compared to Load-Base Dynos (wheel Hp numbers). I'll probably get shot for this is if its not what Booger meant

My comment related to the fact that you (Sharif) has produced some numbers (226 WHp) on a Dynojet which were very consistent with our WHp numbers on Load-Based dynos here in the UK - so my confusion related to whether DynoJet numbers really are inflated compared to Load-Based dynos in the first place.

I think Crank BHp (crank torque) numbers should be dismissed for drivers - they are no doubt relevant for engine designers to understand the stresses on the crankshaft under the induced rotational acceleratrion - but for drivers, the wheel HP (wheel torque) is of key importance to determine the rotational acceleration of the wheels and hence the straight-line acceleration of the car on the road.

 

"underpressure" is probably best qualified to answer this question. He is the East coast sales rep for Dyno Dynamics, and he gets this question all the time. He has used all of the various dynos, and has made some conclusions based on his experience. We use a DynoDynamics dyno, and I can tell you for certain, that it reads roughly 13% lower than a dynojet. We have tested cars on the same day on both a DynoDynamics machine, and a Dynojet, and have come to this conclusion. Now, we do correct our numbers +13% to account for this. Stock 350Z's 03-04 dyno between 225-235whp on this load based dyno WITH the correction factor.

Many dyno operators will scale the restuls 13% but not inform the customer. You should ask your dyno operator if they use a correction factor.

 

That is interesting - but it does sound as if you guys have had this discussion many times before. So time for a 'Search' with apologies.

For the record, the tuner here uses 'DynaPack' which apparently is a 'wheels-off' load-based dyno?

 

I didnt mean A DynoJet reads crank HP.....but is CLOSER to crank HP . And a load based Dyno would be closer to a real whp reading . Just stating an observation I see between the two . Your right... I dont know Jack about Dyno's . Its just there is such a wide gap between the two it hard to compare them and make heads or tails out of all of it

 

I agree is can be confusing at times. But a dynojet doesnt even read close to crank hp....on the 350Z, its about 15-20% shy of crank hp.

 

I dont know about other load based dyno's...but the Mustang stock Dyno's [ that Ive seen , and its hard to get anyone to post them ] are around 190 to 200whp . And most of the stock Dynojets are around 235 to 245whp that Ive seen . Does that gap get even wider as you introduce FI and increase the hp by 100 to 130hp ?

 

no i do understand that part, typically 15% for m/t, and 20% for a/t. my point was if they are getting the hp figures from the tire also, it really doesn't matter on the crank hp as it will always just be a close guess, maybe, lol. the Z may even be lower due to the composite driveshaft or lightened flywheels and clutch, or light wheels. just too many variables to be accurate.

 

End of the day, the key bit is what is the increase resultant from a mod. So if you have a dyno that reads 300 WHp and increases to 360 WHp or one that reads 1WHp and increases to 1.2 WHp does it matter - the relative performance increase is the same? Stick to the same dyno, I guess

 

A Dyno Dynammics dyno without any correction, will read about 190-200whp on a stock 350Z. The important thing to note, is whether a correction factor is used, in order to achieve "dynojet-like" numbers.

Any way you slice it, dyno numbers (load or intertia) are not even close to Crank HP numbers, as the orginal post suggested. And that is the point I was trying to make.