Dastek Unichip...
Discussion
Dave, Interesting you should say that about Powerstations rollers. My E30 M3 Sport Evo (Stock 238PS but most dont make much above 230BHP) was fitted with Motec ECU which deleted the vane air flow meter and ran A/N. When mapped on Powerstations rollers it made a claimed 261.3bhp fly uncorrected. Wheel power was 192.4bhp uncorrected. 68.9bhp does seem a lot to loose in the transmission and tyres. What I couldn't understand was the coastdown losses were added to the uncorrected wheel figure then the whole lot was corrected to DIN 258.5bhp. I would have expected the measured power at the wheels to be corrected and then the coastdown losses added as air and baro has no effect on coastdown.
This was the same at Northampton Motorsport where on a s
tty day the car was measured at 175bhp wheel uncorrected with a transmission loss of 41 giving 216bhp uncorrected. This was corrected to 228bhp DIN.
A point to note is when I applied DIN correction to the wheel figures using the environment data from the supplied graphs, both were within 3BHP of each other. So two sets of rollers reading similar, but providing massively different transmission losses.
Something else worth considering is the rate of acceleration during the test. When an engine and drivetrain is accelerated power is being consumed by everything in the chain from the front pulley to the wheels. For example, it may require 10bhp to accelerate the 100kgs of rotational mass at 100rpm/sec. If you accelerate that 100kg rotational mass at 200rpm/sec then more power is consumed. What is measured by the rollers is what is left over from accelerating the drivetrain. The faster you accelerate the less is left over. A change to the rate of acceleration the dyno allows will affect the end result.
Steve
This was the same at Northampton Motorsport where on a s
tty day the car was measured at 175bhp wheel uncorrected with a transmission loss of 41 giving 216bhp uncorrected. This was corrected to 228bhp DIN.A point to note is when I applied DIN correction to the wheel figures using the environment data from the supplied graphs, both were within 3BHP of each other. So two sets of rollers reading similar, but providing massively different transmission losses.
Something else worth considering is the rate of acceleration during the test. When an engine and drivetrain is accelerated power is being consumed by everything in the chain from the front pulley to the wheels. For example, it may require 10bhp to accelerate the 100kgs of rotational mass at 100rpm/sec. If you accelerate that 100kg rotational mass at 200rpm/sec then more power is consumed. What is measured by the rollers is what is left over from accelerating the drivetrain. The faster you accelerate the less is left over. A change to the rate of acceleration the dyno allows will affect the end result.
Steve
It's engine power that is affected by atmospheric conditions and this is the figure that must be corrected to DIN standards. If you make the assumption, which is of course false to start with, that adding 'coastdown' losses to actual wheel bhp gives you actual flywheel bhp then it can only be this final figure that merits correction. As coastdown losses bear no scientific relationship to true transmission losses occuring when the engine is powering the transmission the entire premise is flawed to start with but it's the closest a rolling road can come to 'guesstimating' flywheel bhp from wheel bhp. It's discussed in detail on my site.
Ramp rate does indeed play a part in affecting wheel bhp as you say. Only steady state power figures with the engine held at a fixed rpm can be considered as true bhp measurements. Anything else is affected by inertia. However if the ramp rate is chosen wisely and the car is in a high gear the effects should be minimal and should be allowed for inside the dyno software to some extent. It also depends on whether the operator has input a reasonable figure for the vehicle's inertia. It may well be that it's these factors not being used properly that lead to a normally accurate system like the Dastek not working at all in the case I described previously.
Back in the day when all we had were ancient Clayton waterbrake rollers and Heenan and Froude waterbrake engine dynos none of this nonsense played any part. All you could take were steady state wheel figures and no one had thought of coastdown losses as a fudge back to flywheel power. Every roller or dyno read the same, assuming it has actually been calibrated, and everyone knew where they stood. Nowadays it's little more than a lottery how many bhp you get told your engine has. As big numbers help sell tuning products there is pressure to apply large coastdown losses and big correction factors to what might have otherwise been realistic wheel bhp numbers. The average punter is unfortunately too uninformed or too disinterested to question anything they get told. Bragging rights down at the pub are more important to them than science.
Ramp rate does indeed play a part in affecting wheel bhp as you say. Only steady state power figures with the engine held at a fixed rpm can be considered as true bhp measurements. Anything else is affected by inertia. However if the ramp rate is chosen wisely and the car is in a high gear the effects should be minimal and should be allowed for inside the dyno software to some extent. It also depends on whether the operator has input a reasonable figure for the vehicle's inertia. It may well be that it's these factors not being used properly that lead to a normally accurate system like the Dastek not working at all in the case I described previously.
Back in the day when all we had were ancient Clayton waterbrake rollers and Heenan and Froude waterbrake engine dynos none of this nonsense played any part. All you could take were steady state wheel figures and no one had thought of coastdown losses as a fudge back to flywheel power. Every roller or dyno read the same, assuming it has actually been calibrated, and everyone knew where they stood. Nowadays it's little more than a lottery how many bhp you get told your engine has. As big numbers help sell tuning products there is pressure to apply large coastdown losses and big correction factors to what might have otherwise been realistic wheel bhp numbers. The average punter is unfortunately too uninformed or too disinterested to question anything they get told. Bragging rights down at the pub are more important to them than science.
Pumaracing said:
The VR6, at least the 2.9 engine, is not the ideal choice on which to conclude a dyno is accurate. The 2.8 certainly puts out close to its claimed
Probably something daft like 120 at the wheels and supposedly 180 or more at the flywheel.
Precisely right!Probably something daft like 120 at the wheels and supposedly 180 or more at the flywheel.
They all had aftermarket intakes and exhausts, so 180 may or may not be right ish. I did ask the operator, a nice bloke he is too, about the low @wheels figure, because the PH missive said the same thing when I posted my dyno sheet of 2 years ago. Can't remember what he said now but did say in a different gear you'd get different @wheels figure and then different run-down losses but it works out at the same estimate figure.
I rate how powerstation send out pdfs of the dyno results after their dyno days; a nice touch and it seems they're putting themselves out there for criticism too, bravely!
Anyway, anyone want to run my car showing lambda please?
Edited by Pentoman on Wednesday 19th November 15:02
Pumaracing said:
One day I'll have to ask Gerry at Dastek what jiggery pokery it takes to achieve this but it makes it bloody difficult to compare such rollers to anyone else's. It also makes it impossible to use my normal trans loss equations which of course rely on accurate wheel numbers to produce reasonable flywheel 'guesstimates'.
Dave Baker
Puma Race Engines
Dave, if you go on the MLR forum and do a search under Gerry Gaffney you will find he has put alot of time and effort into posting up why he believes its best to measure power at the flywheel and not rely "too" much on power at the wheels. I am a believer of this too, especially since owning the Dastek dyno and having used other dyno's. Alot of the percieved "guestimates" are infact measurements read by the dyno on coastdown. Obviously there are such things as transmission inertia and tyre pinch on very high powered cars which no-one can ever measure accurately on the dyno as each car is different, so an average of that is taken. But what it does do is cancel out alot of the unknowns and produce much more consistent power at the flywheel figures.Dave Baker
Puma Race Engines
Generally, if we see a car which has been on Powerstations rollers, we will see alot more power at the wheels, but much less power at the flywheel than thiers. This isn't to say thier rollers are crap and mine are the best as every dyno should be treated as a tuning tool and the same dyno should really be used when comparing upgrades, etc. But as Warrens M3 only made 252bhp on Powerstations dyno where it made 260+bhp consistantly on our Dastek dyno, if nothing has changed with Warrans M3 since I mapped it, I would have expected over 275bhp on Powerstations, so to me atleast, there is something wrong with the M3.
EDIT: Just read the rest of this thread, should have done that before posting the above LOL. My Dastek does produce very similar, if not, the same figures on different ramp rates. Even conducting an inertia run will give similar, if a little higher, figures to a loaded run. For what its worth, I recently ran a modified Audi S2 (4WD) in 3rd gear which is the recommended gear to use for 4WD's, and it made 290bhp, Ran the car up again in 4th, but used the next slowest ramp rate and it produced 291bhp. The boost profile was slightly different as more boost was seen at the same RPM than the 3rd gear run, but apart from that, the graphs looked the same. I have to say, I was pretty gob smacked when I saw the results.
On another note, its pointless for me to comment on other peoples rollers, there was a big blow up a while ago with Dastek vs DynoDynamics, but at the end of the day, they both are superb machines if used in the correct way. We researched and trialed alot of different makes of dyno's and we ended up with the Dastek. If I was to purchase another dyno, it would have to be a Dastek. But a DynoDynamic operator would probably say the same for thier dyno. At the end of the day, they are designed to help tuners tune engines without the need for removing the engine.
Steve, are the Northamptons rollers the same make as Powerstations?
Hope this helps
Edited by ShepsM3 on Monday 17th November 21:21
Edited by ShepsM3 on Monday 17th November 21:23
Vixpy1 said:
Ah, Unist
I agree.tFit a decent aftermarket standalone instead or remap te OEM ECU. I had a unichip fitted by an apparently "good" company to my old MR2 turbo, needless to say the ringlands collapsed, engine rebuild required.
Piggys backs don't give absolute control and so are no good on active, complicated ECU'. Standalones are the way forward.
Edited by Herman Toothrot on Monday 17th November 22:49
Herman Toothrot said:
Vixpy1 said:
Ah, Unist
I agree.tFit a decent aftermarket standalone instead or remap te OEM ECU. I had a unichip fitted by an apparently "good" company to my old MR2 turbo, needless to say the ringlands collapsed, engine rebuild required.
Piggys backs don't give absolute control and so are no good on active, complicated ECU'. Standalones are the way forward.
Edited by Herman Toothrot on Monday 17th November 22:49
Later CAN BUS type cars cannot be converted to stand alone so easily these days, necessitating ECU remaps and piggyback systems. Its horses for courses, but please don't slam the Unichip because of a bad experiance with your engine.
The Unichip version Q gives just about all the control thats needed now.
Edited by ShepsM3 on Monday 17th November 23:36
Fair enough, but i'll stick with standalones far easier to use. After the disaster with the MR2, I decided I'd prefer to know exactly what the so called experts are doing so went on MoTeCs training course, so I can make my own alterations as needed and make sure the experts done their job properly (chances are they won't have got it spot on to take into account the particularly cold or hot days etc). Unichip don't distribute software unlike standalone manufactures, so if i pop a decat on, or raise the boost etc I just remap myself with no bother. If you've a unichip off to the dealer again. They are not such a cheap solution when you factor that in.
Herman Toothrot said:
If you've a unichip off to the dealer again. They are not such a cheap solution when you factor that in.
Thats true, but honestly, I don't think that is such a bad idea. I have set up stand alones in the past, only for the owner to fart about with it, only for them to return it red faced many times. Motec is mega expensive to start with, but once you have it and you have done the course, then that will obviously work for you. Megasquirt... its fun, but can be complicated and I know tuners who won't touch it. lol. (Early versions that is)
Edited by ShepsM3 on Tuesday 18th November 17:18
ShepsM3 said:
only for the owner to fart about with it, only for them to return it red faced many times.
True, that must be kept in mind don't fiddle if you don't A) Understand B) have a Wideband, C) have some sort of knock detection.Thing is its obvious some people should never contemplate touching an ECU,.. like the guys who had to come back to you,.. did they not think to make a backup of your map before they fiddled? I know a couple of mappers and they have all experienced this, so I guess there are quite a lot of stupid people about.
Herman Toothrot said:
did they not think to make a backup of your map before they fiddled? I know a couple of mappers and they have all experienced this, so I guess there are quite a lot of stupid people about.
Well, you'd think so wouldn't you. I always save the maps, so its generally not a problem. Its the ones who also change the characteristics of the engine (like cam timing) which then totally throws things out the window. The problem here is the customer nails you down on price for mapping, so, however good practice it is, you can't waste time going round the engine taking notes of adjustments and measurments made before it got to me, but I do tend to mark stuff now because of it. Vixpy1 said:
Paul, What sort of Aftermarket ECU stuff have you been mapping?
I may have something of interest to you
All sorts of stuff... although I am always interested in anything you want to tell me about I may have something of interest to you
I have emailed you my numbers Edited by ShepsM3 on Friday 21st November 22:04
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