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Discussion Starter #1
Found this when trolling through Dyno Day results and am using it to highlight my question on transmission losses on Evo's

Owner: Evo400 : VI GSR
ECU : Gems (mapped by sam ellesar) 1.6 - 2.0 bar
Piper cams, evo400/evo-7 Turbo Dynamics turbo, 5 Zigen exhaust, evo400 induction
Running Shell Optimax
Owners Expected Flywheel Figure : 400 bhp
Actual Power : 298.3 bhp ATW / 2340 Tractive Effort
Flywheel Guestimate : 392..5 bhp

It has been debated that 24% transmission loss is too high but if you used say 20% as a loss, then this 400 BHP car would then only be 373 BHP ????

So is this car 373 BHP--393 BHP or 400 BHP

A
 

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Totally agree with Aidy and more importantly, who cares. We ahve been over this so much. Use the ATW figures for real comparisons and "estimated" flywheel figures for bragging. :)
 

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Re: Re: Transmission losses "again"

Aidy said:
Until the engine is put on an engine dyno no-one will ever know.
And unless the engine is ever used outside of a vehicle it's the ATW figures that are the important ones anyway. I could have an 800bhp Norris monster under the bonnet, but if I'm using the worlds most inefficient transmission and only getting 180bhp / 160ftlb to the wheels then I'll still be slower than a stock Evo ;)
 

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Re: Re: Re: Transmission losses "again"

NumptyScrub said:
And unless the engine is ever used outside of a vehicle it's the ATW figures that are the important ones anyway. I could have an 800bhp Norris monster under the bonnet, but if I'm using the worlds most inefficient transmission and only getting 180bhp / 160ftlb to the wheels then I'll still be slower than a stock Evo ;)
True - and the transmission would melt :crackup:
 

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Discussion Starter #6
Simon7extreme said:
Totally agree with Aidy and more importantly, who cares. We ahve been over this so much. Use the ATW figures for real comparisons and "estimated" flywheel figures for bragging. :)
I agree ATW and Tractive are the real world numbers.

Merely curious as to why some people on MLR [arguably the most educated forum on dyno results] still use "estimated" numbers when speaking/posting about their cars or ability to tune.

A
 

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Evo 396 said:
I agree ATW and Tractive are the real world numbers.

Merely curious as to why some people on MLR [arguably the most educated forum on dyno results] still use "estimated" numbers when speaking/posting about their cars or ability to tune.

A
The reason is that most people like to compare with Mitsubishi std figures which are always quoted as at the flywheel.
I think however that on this forum at least, people are starting to come around to the idea that the ATW figures are really what you should be comparing from a rolling road rather than go through the fun and games of guessing a transmission loss figure

Andy
 

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AndyF_RSX said:
The reason is that most people like to compare with Mitsubishi std figures which are always quoted as at the flywheel.
I think however that on this forum at least, people are starting to come around to the idea that the ATW figures are really what you should be comparing from a rolling road rather than go through the fun and games of guessing a transmission loss figure

Andy
Some of us use a proper engine dyno, because it is more accurate than a RR and is a much mre useful development tool.

the downside is the cost :mad: , but engine dynos are the daddies :cool:
 

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Evo 396 said:
Found this when trolling through Dyno Day results and am using it to highlight my question on transmission losses on Evo's

Owner: Evo400 : VI GSR
ECU : Gems (mapped by sam ellesar) 1.6 - 2.0 bar
Piper cams, evo400/evo-7 Turbo Dynamics turbo, 5 Zigen exhaust, evo400 induction
Running Shell Optimax
Owners Expected Flywheel Figure : 400 bhp
Actual Power : 298.3 bhp ATW / 2340 Tractive Effort
Flywheel Guestimate : 392..5 bhp

It has been debated that 24% transmission loss is too high but if you used say 20% as a loss, then this 400 BHP car would then only be 373 BHP ????

So is this car 373 BHP--393 BHP or 400 BHP

A
this is why chris @ WRC TECH never quotes anything other than ATW'S which is totally right . power figures are very subjective and i really believe that if the dyno cannot match the dataloggings that we see from the road how can the said plots be correct ?? i recently had a customers car run on a OWEN /daztek dyno . before we data logged the times in gear from 2000rpm to 7000rpm . in 4th gear the car on road took 10seconds on the dyno in the same gear it took 19seconds . why ???? and better still how could you ever map a car successfully using this type of setup . the WRC TECH type dyno (dyno dynamics ) actually runs the cars @ faster than road accelerations . typical is 6/8 seconds . this has a effect on boost and how it is mapped. steve simpson always ends up resetting the boost after a dyno session because that type of dyno allows boost to be made faster than on road therefore overboosting if not corrected .

dave
 

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Evo Too said:
Some of us use a proper engine dyno, because it is more accurate than a RR and is a much mre useful development tool.

the downside is the cost :mad: , but engine dynos are the daddies :cool:
in a recent corespondance with superflow europe i asked the question

1 engine mapped on the superflow engine dyno made x hp and torque . same engine then fitted to car and run on there state of the art chassis dyno .

question : do they both make the same numbers ?

answers on a postcard !!

answer fron superflow

Dear Dave,

This is not the eeasiest question to answer.
It is more or less depending on your expectations. Normally we would say YES
but with minor differences. Both our engine and chassis dynos are measuring
so precise that there will always be difference between those two results
due to measured and unmeasured losses.

so as you see norm superflow are saying that yes the figures can be compared succesfully but the figures will always be +- a hp or too either way .
from the horse's mouth i should say !!

dave

even they would not comit to saying what is the definative tool

:D
 

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I'm only going to run with ATW figs at the WRC Tech Dyno Weekend.

When I publish the results we will run ATW figs and a separate section for PTP (Pub Talk Power).

This will save a lot of mindless bandwidth on here afterwards anyway!
 

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evo400 said:
in a recent corespondance with superflow europe i asked the question

1 engine mapped on the superflow engine dyno made x hp and torque . same engine then fitted to car and run on there state of the art chassis dyno .

question : do they both make the same numbers ?

answers on a postcard !!

answer fron superflow

Dear Dave,

This is not the eeasiest question to answer.
It is more or less depending on your expectations. Normally we would say YES
but with minor differences. Both our engine and chassis dynos are measuring
so precise that there will always be difference between those two results
due to measured and unmeasured losses.

so as you see norm superflow are saying that yes the figures can be compared succesfully but the figures will always be +- a hp or too either way .
from the horse's mouth i should say !!

dave

even they would not comit to saying what is the definative tool

:D
Hi Dave, I'm not arguing with what Superflow or you say - far from it. :)

What I am saying is that it is a lot easier and quicker to develop an engine on a bench dyno. Naturally, when the engine is finally installed into the car, the tuner will make appropriate tweaks to optimise the dynamic response. He should, however, not have to make any significant changes to the map.

Ideally it would be good to have a bench dyno and a RR side by side under the same roof - then the % losses could be quantified for engines of different ouputs.

It is just more expedient to experiment with turbo, cam and manifold setups on a bench dyno.
 

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Try a dyno run with tyre pressures set at 30psi. Measure ATW power.
Try another with tyre pressures set at 20psi. Measure ATW power again.
Think they'll be the same?!
 

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Russs said:
Try a dyno run with tyre pressures set at 30psi. Measure ATW power.
Try another with tyre pressures set at 20psi. Measure ATW power again.
Think they'll be the same?!
No, they won't. That is why G-force and other good RR outfits do your tyre pressures before the run.

However - the very geometry of the "2 roller per wheel " system means that more power is soaked up by the RR than by a normal "tyre on tarmac" contact patch.

This is one of the reasons why the guys in the US get higher readings on hub dynos than our RR ATW figures here.
 

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Fairy nuff, but that wasn't quite my point.
There are waaaaay too many variables at play in ATW dyno figures. Tyre pressures, tyre temps, gearbox oil temp, viscosity etc etc etc etc.
Surely better to measure coast down at the end of each run and calculate transmission losses that way, a la Dastek dyno?
 

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Russs said:

Surely better to measure coast down at the end of each run and calculate transmission losses that way, a la Dastek dyno?
no because the engine is no longer attached to the drivechain so you are not measuring full losses.

there is no true ''exact'' way to calculate transmission losses without doing a bench dyno and then a chassis dyno on the same car.

everyone of them will be slightly different
 

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WULLIE said:
no because the engine is no longer attached to the drivechain so you are not measuring full losses.

there is no true ''exact'' way to calculate transmission losses without doing a bench dyno and then a chassis dyno on the same car.

everyone of them will be slightly different
Oh yes there is its called a transmission dyno. superflow make then just as they do engine dyno's

dave
 

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evo400 said:
Oh yes there is its called a transmission dyno. superflow make then just as they do engine dyno's

dave
how do they work then??

power unit on the the gearbox and something on the hubs showing a lower fig??
 
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