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MG MGF Technical - Road Dyno

Does anyone have any experience or opions about this device.
Ken Waring

Never heard of it.., but reading up, just seems to many options for decent testing.

Fair enough, you might bolt on a big turbo and exhaust etc and get 30-40 bhp.. great.

But that's not really what we use dyno's for.. is it?

In my experience you put your car on a dyno, get the figures, whack in your new air filter and find out if its any better.
With this.. you wouldn't know.

Is my car more powerful..? ..well it says it is, but was I steering the same line and the same pace, are my tires hotter/colder than earlier (expansion).. which side of +/- 5hp was each figure?

How powerful is the car? Well, is the road truly flat? compared to my mate.., does he has ever so slightly higher inflated tyres/more tread?

Seems a bit of guess work to me..
You could probably get close.., but the manufacturers figures'll do that for you.
Neil H

Hmm - this is an accelerometer with an electrical take off from the electronic rev-counter signal. Pretty straightforward stuff - reminds me a little of the RaceTechnology AP-22 module that is quite popular.

You need to know the mass of the vehicle, the frontal area (I see that you need to enter all these values - so that's a good thing) and in order to estimate power at the flywheel, transmission losses need to be calculated... The descriptions on the site are in parts somewhat misleading IMO, but the equipment should do the job. No idea how sensitive this is though - the point that you make Neil. Also, it may be sensitive to lateral acceleration forces, and road surface...

Might be a decent purchase - if it is at the right price? Looks as though they're asking 85 quid for it... I guess that's half the price of the AP-22 (reviewed at - and the RaceTechnology website: - although you'll need a laptop to use with it. I wonder if there is a direct comparison between the two products somewhere on the web?
Rob Bell


I've taken a look at the AP22 write up. That seems to be based on accelerometer transducer. There are lots of inexpensive devices capable of this. The Road Dyno just uses effectively change of RPM related to time, so lateral acceleration shouldn't be an issue. It seems that both of these devices are rather expensive when all they do is record a series of values over time. Processing the resultant data with well published automotive formulae doesn't appear to difficult. I think you just need a portable PC and some input signal conditioning.

What did you think was misleading?


I take your point about the variables but then you have this problem with all dynos, temperature, pressure humididty etc. So how accurate are any of these measurements? Different dynos, quite differrent results. If they are all considered to be comparative tools then a crude method used under the same conditions may be just as effective in showing a change, improvement or otherwise.
A high number of samples(Road Dyno approach) means not such a crude method I think but a couple of additional parameters to consider.
Ken Waring

I used a similar device a little while ago which you set up and stuck to the windscreen, no connections needed except 12v from the cigar lighter socket.
It measured BHP, 0-60, 0-100 and 1/4mile time and speed.
I was doubtful about how it worked accurately so borrowed it rather than bought one.
It takes a few attempts to get it right but it does seem to be accurate.
We tried it on my 220 Turbo, then my ZT, and then we tried it out in an Esprit Turbo. I havent had a chance to get the 220 on a drag strip so when it came back with a 13.9 second 1/4 it seemed a bit quick but when it gave a reading of 16.9 for the ZT it did'nt seem too bad. The Esprit read 12.8 but we got a bit of wheelspin in 1st and 2nd.
The BHP figures were cack, they changed everytime we tried it.
0-60 times were about right too.
The one I tried retails at 120, worth the money if you keep modding your motor.
Steve Tyler

I agree that the costs of these products do seem somewhat expensive for what they are offering - no idea about what the details of the increased costs are...?

An accelerometer might be better as a kit based on rpm alone would artificially overestimate engine power if there were tyre slip. Having said that, an accelerometer would underestimate power if the tyres were slip. Best option might be to have both?
Rob Bell

This thread was discussed between 28/11/2003 and 30/11/2003

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