Rolling Road day
24 February 2001

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The FTO Owners Club first official rolling road day was held at Aldon Automotive in Birmingham. There premises were ideally located enabling a lot of people to attend, not to mention the fact that they are speciallist engine tuners so they know what they were talking about.

The car park was filled with FTO's ... a good turn out of 34 FTO's. It's always great to see so many in one place! We got a good selection of models which was an essential part of the day - we'd be able to see comparative figures for just about every engine and gearbox combination.

 
Richard Batty's beast on the rollers
 
 
 
My ear-bleeding FTO on the rollers (before it got a wash :)
 

Dawn's tidy FTO on the rollers

 

 

Here's Richard pretending not to be worried.

You have no idea how nerve-wracking the experience is ... your FTO at 8,000rpm with you standing feet away from it is definately a brown-trowser job. Of course for onlookers it's extremely good fun!

 


The car was run up to speed to calibrate their rollers and then the throttle was pushed into the carpet. As the run progressed we saw a graph appearing on the computer readout. As the revs rose higher and higher, on MIVEC cars the ear-splitting noise after 5,500rpm was just incredible.


My FTO JUST squeezed onto the rollers. I reckon that's 4mm clearance there!


Own up - who spent hours cleaning their engine bay? ...and a picture of my interior.

The trophy winners

Dave Hughes, winner of the FTO GT2 challenge.
The challenge was to drive a virtual FTO (on the PlayStation) and record the fastest lap in a Teaivon Trampio FTO (378BHP) on the High Speed Ring. Dave's time was 53.582.

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Impressive until you remember that Dave & Martin have been playing the game for months :)
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Stuart Mutch, award for the Most Outstanding FTO.
Decided upon by the freelance photograper, Stu won the award because his car is simply a freak :) He got the same top bhp figure as the most powerful manual FTO, with minimum mods! 192bhp at the flywheel. Nice.
Steve Hemming, award for the Most Powerful Automatic FTO.
Steve's figures were an impressive flywheel figure of 188bhp much to the annoyance of Dawn Woodward and Noel Brennan: )

Dave Wilson, award for the Most Powerful Manual FTO.
My figure was 192bhp at the flywheel, same as Stu, but the bhp curve was much flatter and the torque line was quite a bit higher throughout the range.


We're in a magazine!!!


This photo was taken by Zoe, a freelance photographer for Japanese Magazines. She has kindly let us use it.


The GlassWorks

The next stop was for refreshments. Martin had arranged with a pub just down the road from Aldon to take us in, feed & water us.


The Landlord even closed most of the car park so we could all get in line!


FTO's always attract attention wherever they go, ecpecially in numbers! Unfortuantely I always attract the wrong attention and like in this pic above I'm paranoid about leaving it anywhere. However these kids were just interested in what the cars were :)

Thanks to Martin While, Gary Nelson, Aldon Automotive and The GlassWorks for the great day!


A word on Rolling Roads or "Chassis Dynometer's" (from my PERFORMANCE page)

The car is driven onto a set of rollers so that the driving tyres are resting between two steel cylinders. The torque is measured at different speeds at the wheels. The same equation in the part above about torque / bhp can be used to calculate bhp at the rollers by knowing the torque and the rpm of the rollers. If the engine rpm is measured simultaneously then we can know roller speed at a particular engine speed. The BIG problem is that there is a possibility of tyre slip is taking place. Remember these are smooth steel rollers which over time get quite polished. As the effects of tyre slip are complex we'll not go into them here but what I do know is that you can get some really strange bhp figures from highly tuned engines on narrow tyres and the readings are invariably too high not too low.

 

 

What is transmission loss?
Well all mechanical systems suffer from friction and a proportion of the power fed into a system will get dissipated by friction and turn into heat and noise. Note the key phrase there - "power fed into a system". For there to be a loss there must be an input - simple and obvious yes but we'll see the relevance in a minute. When your car is parked overnight with the engine switched off, the transmission losses are obviously zero. When the car is running then some proportion of the flywheel power will be lost in the gearbox, final drive, drive shaft bearings, wheel bearings and tyres. For a given mechanical system these losses will usually stay close to a particular fixed percentage, let's say 10% for example, of the input power. So if the car is cruising and developing 20 bhp then 2 bhp will get absorbed as friction - under full power, say 100 bhp, then maybe 10 bhp will get absorbed. Now it is true that not every component in a transmission system absorbs a fixed percentage of the input power. Some components like oil seals and non driven meshed gears (as in a normal car multi speed gearbox) have frictional losses which are not affected by the input torque. These losses do increase with speed of course but at a given rpm can be taken to remain constant even if the engine is tuned to give more power. Finally, the biggest source of loss in the entire transmission system of a car is in the tyres - they account for half or more of the total losses between the flywheel and the rollers. Each set of driven gears, i.e. the final drive gear or the particular gearbox ratio that you happen to be testing the car in, only absorbs about 1% to 2% of the engine's power. Ok - so how do these software systems that supposedly measure transmission losses so as to "predict" back to the flywheel bhp work. The power curve at the wheels is taken in the usual way as explained above. Then, at peak rpm, the operator puts the car into neutral and lets the rollers slow down under the drag of the tyres and transmission. The software then measures this drag (or "coast down loss") as "negative" power and adds it to the wheel power to get back to the supposed flywheel power. BUT - and hopefully you've all spotted the problem now - the engine is not feeding any power into the drivetrain while the car is in neutral - in fact it isn't even connected to the drivetrain any more!! Whatever drag this is that's being measured it has nothing at all to do with the proportion of the flywheel power that gets lost as friction when the engine is powering the car in the normal way. The engine could now be an 800 bhp F1 engine or a 30 bhp mini engine for all it matters because it isn't connected to the gearbox or feeding any power into it. Obviously this "coast down loss" is something to do with the transmission and tyres but it is not the true transmission loss - in fact this coast down loss should never be expected to change for a given car at a particular rpm regardless of how much you tune the engine whereas a true transmission loss will increase as the engine power increases because it is dependent to a large extent on the amount of power being fed into the transmission. As the engine was tuned to give more power the "true" transmission losses must have also increased to some extent but these chassis dyno systems don't, and can't, show this happening.
So is there any way of really measuring the true transmission loss of a car?
Yes - only one - by measuring the flywheel power on an accurate engine dyno, the wheel power on an accurate chassis dyno and taking one away from the other. There is no way of finding out the true transmission loss just by measuring the power at the wheels. So hopefully that's got you all thinking a bit more now instead of just taking for granted the "flywheel" figure you were given last time you took your car to the rollers. Even worse is the fact that some of these software systems allow the operator to just programme in the percentage of transmission loss he wants the system to add to the wheel figures. So if that isn't a nice easy way to show some big fat flywheel bhp then I don't know of a better one. It's certainly a lot easier than actually doing some proper development work to make the engine perform better - just dial in a bigger transmission loss and there you go - the same wheel bhp now turns into a bigger flywheel bhp - happy customer, happy dyno man - just a shame it was all sleight of hand. See the end of this article if you doubt that this sort of thing really happens.
So what should you do when you take your car to a rolling road?
Firstly, make sure you get printouts that show the wheel bhp and not just the flywheel bhp. Then at least you can see if they look sensible in comparison. If you have a desperate need to know the flywheel bhp then you will have to estimate it - there's no other way short of using an engine dyno. The corrections you need to make for cars with manual gearboxes are these: The average front wheel drive road car with between 100 and 200 bhp loses about 15% of the engine bhp as transmission losses. The average rear wheel drive road car with between 100 and 200 bhp loses about 17% of the engine bhp as transmission losses. The increase in % loss over front wheel drive is because the differential has to turn the drive through 90 degrees at the back axle which soaks up a bit more of the engine's power. 4wd cars will have higher losses because of the extra differentials and other power transmission components. A reasonable estimate of an average 4wd car's losses might be 22% to 25% of the flywheel power but it isn't a subject I have sufficient data on to be definitive. What your own specific car loses is anyone's guess - yours is as good as mine - but it shouldn't be far from the figures above. For sure though, no car in the world, unless it has flat tyres and a gearbox full of sand, loses anything like 30% of the engine's power in the transmission and tyres as many rolling road operators would try to have you believe. So take the wheel figure and divide by 0.85 for FWD or 0.83 for RWD and that will get you as close to the true engine bhp as you are ever going to know. In general though it is fair to say that low powered cars have higher % losses than high powered cars. For example, a 60 bhp Fiesta will have around 14 to 15 bhp total transmission and tyre loss whereas a 90 bhp XR2 will only have about 17 to 18 bhp loss - a smaller % obviously. By the time you get to RWD cars with engines in the 300 to 500+ bhp range, losses can eventually drop to as little as 12 to 14% or so. Another rule of thumb I use which is quite accurate is to treat the losses as being 10% of the flywheel power plus 10 bhp for FWD and 12% plus 10 bhp for RWD cars. This equation "loads" low powered cars more than high powered cars which is more closely like what happens in reality. Remember, these percentages are not "gospel" - they are good realistic averages.

Most of the pics on this page were taken by Steve Hemming and Martin While. Thanks for letting me use them.


Visit the Links section and look for the FTO Owners Club Resource to see some more rally photos

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