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Location: Enginetuner.co.uk Plymouth Dyno Dynamics RR Engine machining and building EcuTek SimTek mapping
Posts: 2,306
Excuse me, but an alternative viewpoint doesn't mean I'm knocking anyone!
It's hard to bandy opinions with anyone who doesn't actually own a dyno, but rather has fleeting glimpses of someone else's, particularly if they have a vested interest, as we all do! I recall using the words "pretty much mimics", which means as close as you'll get in that environment. Of course, when you go faster, you have to shove more air out of the way, although I don't know of any tuner who bothers to allow for wind direction or speed, which makes a huge difference.
I still fail to see how anybody could figure that scarcely any test carried out on the public road could be considered scientific, considering the rampant variables involved.
According to some, the only way to achive testing heaven would be to have a dyno cell that goes up and down by a couple of hundred feet, subject to wind and rain, sh-te thrown on the tyres at random intervals, along with the occasional suicidal pedestrian thrown in for good measure.
As I keep saying, WE have the option to test how we like, any time we like. Road. Track. Dyno.
No dyno? no options...
Incidentally, I owned one of those Maha dynos for 20 years. You could enter frontal area, weight and rolling resistance calculated from charts. Interesting!
Very interesting to read about the different engine loadings produced when accelerating on the road compared to rollers. I can see how rollers couldn't exactly duplicate the variable loads produced in open road acceleration.
But supposing you road map a car using a long stretch of flat road. What happens when you later accelerate up a hill, or down an incline? Surely the loadings are then quite different And what about in very windy conditions? Wouldn't it be true that a strong tailwinds would produce different loadings to a strong headwind? Now I'm really confused
The mass of the car vs torque output is the primary loading with regard to acceleration. Hills/wind may affect this by say +/- 10% this level of variation is acceptable. Same if you are 4 up instead of on your own, things will differ slightly.
From the accel curve I posted you can see there is a 100% change in accel from low to mid rpm, on the road this will still happen in proportion regardless of inclination or wind.
On the rollers it would stil be a flat rate and therefore at least 50% error on actual.
Location: Enginetuner.co.uk Plymouth Dyno Dynamics RR Engine machining and building EcuTek SimTek mapping
Posts: 2,306
Andy F says a variation of plus or minus ten per cent is ok, due to wind and gradient variations when road testing.
There was me worrying about two per cent!
I think he's just confirmed what I always figured.
Location: Enginetuner.co.uk Plymouth Dyno Dynamics RR Engine machining and building EcuTek SimTek mapping
Posts: 2,306
Andy, you are talking rubbish now. You might have got away with that if all we did was run up in just one dynoplot format, but you know and I know there are much more useful test procedures and data available than that.
When you used our rolling road, you seemed quite happy with the results, unless you are now telling us that in actual fact you did a crap job on all five cars?
We set up the Adrenaline Motorsport Murtaya kit car today. ( All Impreza mechanics, but 400 kg lighter! ) We used the dyno and road driving to get where we wanted to go, and we are track testing this weekend. Now what's wrong with that?
I think we all know how clever you are, so don't over egg your pudding old chap. I'd hate to think you come out of this looking pedantic. ( or narrow minded )
Location: Enginetuner.co.uk Plymouth Dyno Dynamics RR Engine machining and building EcuTek SimTek mapping
Posts: 2,306
Hi there Jock! Not at all, I've been full of praise for my peers in this thread, I'm just defending my position, same as all the others!
I think it's time we all acknowledged the many difficulties involved in this very technical area. It wouldn't be so bad if all we had to contend with were mapping issues. That's the easy bit! the problems come with the wild card you hadn't thought of, like loose clips, split hoses, bad connections, duff dump valves etc. etc. Never mind the daft things the owners do, like fitting the wrong parts then expecting you to deal with it, connecting bits up wrong, bringing cars in with no fuel in the tank... you have to have eyes everywhere and your wits about you and no kidding!
I've been saying for years that we in the Motor Trade have to know more about our job than Doctors do, there's certainly a big enough enquiry if one of our patients dies!
When you used our rolling road, you seemed quite happy with the results, unless you are now telling us that in actual fact you did a crap job on all five cars?
Alan:
Just out of interest, I assume all of the five cars were running without MAFs???
also
I think that even the most ardent proponent of road mapping has conceded, on more than one occassion that "you need the rollers to get the last 10-15bhp" Is that your understanding?
I've been saying for years that we in the Motor Trade have to know more about our job than Doctors do, there's certainly a big enough enquiry if one of our patients dies!
Location: Enginetuner.co.uk Plymouth Dyno Dynamics RR Engine machining and building EcuTek SimTek mapping
Posts: 2,306
Well ducked there Andy... you have more moves than Ali, more tricks than Shumacher and better lines than the bloke in the corner shop on Coronation Street... If we weren't getting more power now out of all five cars you originally did for us, I'd believe every word you said!
I've been saying for years that we in the Motor Trade have to know more about our job than Doctors do, there's certainly a big enough enquiry if one of our patients dies!
If one of your patients dies don't you guys normally use the excuse that they were a smoker and were pretty long in the tooth anyway ?!
Quote:
When you used our rolling road, you seemed quite happy with the results, unless you are now telling us that in actual fact you did a crap job on all five cars?
Alan:
Just out of interest, I assume all of the five cars were running without MAFs???
also
I think that even the most ardent proponent of road mapping has conceded, on more than one occassion that "you need the rollers to get the last 10-15bhp" Is that your understanding?
I'm going in for a remap soon - I am sure that my legs are misfiring at about 4mph and a slight hesitation before accelerating hard out of the office chair
Location: @Junc 12, M40 Warwicksh; 01926 614522 CV33 9PL -Use 9GX for Satnav. South Midlands Simtek ECu dealer
Posts: 5,612
Quote:
Originally Posted by dynamix
I'm going in for a remap soon - I am sure that my legs are misfiring at about 4mph and a slight hesitation before accelerating hard out of the office chair
That'll just be wind! save a fortune on mapping try ' Deflatine '
It could be my Caffeine injectors have reached their maximum duty cycle and are causing me to lean out over 3 random thoughts per min. I will get it checked out along with the Exhaust system David - thanks for the tip
That is not my generally experience. Some cars benefit from trying to "find" power on the rollers, but I have had many instances of mapping on the road and feeling that the "tune" was too agressive on the rollers.
Some cars benefit from the rollers post mapping, but for a number of these cars, I would say that the difference is that the car owner is not in control of the car, or in paticular the throttle.
Ecutek cars are a different beast, as they generally run closer to the knock threshold all the time, as they have active ignition control. And while you can make good power on a few runs, you will often find the ECU has different ideas on the road, sometimes giving more, sometimes less timing than acheived on the rollers.
The instant feedback of the rollers is good, but I have had some serious problems with my car, even on rollers that boast about how easily they can run cars with serious power. And TMIC cars are an absolute pain to run on the rollers representatively.
However, as I've said, I seek to improve the situation for my own purposes. I will still not care paticularly for rolling road shootout results.
Paul
Quote:
Originally Posted by harvey
Alan:
Just out of interest, I assume all of the five cars were running without MAFs???
also
I think that even the most ardent proponent of road mapping has conceded, on more than one occassion that "you need the rollers to get the last 10-15bhp" Is that your understanding?
And what about in very windy conditions? Wouldn't it be true that a strong tailwinds would produce different loadings to a strong headwind? Now I'm really confused 
if only these expensive dynos were so clever !
Classic!
