Rolling Road - what does it do?

[Terry Field]

I'm going to put my Xflow onto a rolling road soon. What is done to the car during the test and what benefits can I expect?

 

Terry

 

Q783 OOR. Team Lotus colours with flares.

[I.Mupferit]

If you don't know, why are you putting your car on the rolling road 🤔

 

Brent

 

2.3 DURATEC SV. In the final weeks of gestation. SVA booked. 😬

[Bradbys]

AFAIK, the rolling road is just that...

 

Its a road that rolls so that you can power the engine up under load - it essentially alows you to "drive" the car at say 70 mph, but have it at a standstill so that you can make adjustments to mixture, needle sizes etc.

 

It should alow you to fine tune your engines performance, and get a power reading at the end (not that these are really ever completely acurate).

 

Expect lots of noise - fumes - engine revving....

 

Brill 😬 😬 😬 😬 😬

 

Edited by - Bradbys on 1 Apr 2005 17:02:48

[charlie_pank]

It does more than that as you can configure the resistance, you can (within the limits of your engine) run the same throttle positions with different engine speeds whilst measuring the power output allowing you to perfect the maps for your engine.

 

Edited by - charlie_pank on 1 Apr 2005 17:21:24

[V7 SLR]

That's not what he asked. I think Brent's question ought to lead to more info from the original poster then we can help with a properly informed answer.

[JasonL]

Your car to be thrashed within an inch of it's life - well for a few seconds anyway 😬

 

1.6 Vx Blydenstein available for sale after Le Mans. here

 

R300 due 14/04/05

[Terry Field]

OK let me ask the question again in a more precise way.

 

I have just installed a new engine. The builder suggested that I put it on a rolling road at an early stage at a speed not exceeding 4000 rpm in order to get it set up properly. Now I am happy that the timing is about right, the carbs were rejetted by the engine builder to suit the engine and I have checked that they are in balance. I am not sure how good the mixture setings are though, and it is spitting back through the carbs probably a bit too much. The valve clearances are accurately set.

 

So, if I put it on a rolling road which, if any, of the above (timing, fuel mixture, balance etc) do they check, and what else do they check as well? Is there any view on whether it is actually worth doing it at such an early stage in the life of the engine.

 

Terry

 

Q783 OOR. Team Lotus colours with flares.

[davidvoas73]

Re what they check.. All depends on the operative, suggest you ring round explain what you want to achieve and see what response you get. I bet someone more knowledgable will come along in a mo and recommend someone for you....

 

Re the mixture .. If it's an Xflow then I guess it's not on electronic ignition, is the engine pinking? if so the mixture could be lean or the timing is out. Whats the fuel consumption like? Visual emissions test could help indicate if it's rich - also you can often tell by the smell - I can't quite describe it - sorry. After a normal run - pop a spark plug out - whats the colour - a light brown means the mixtures about right, black = rich , very pale = lean/hot.

 

Hope this helps....

[Mick Day]

Why is it that people rely on rolling roads so much; why not use a dyno in the 1st place?

[Tony Martyr]

The better name for a rolling road is a chassis dynamometer. A rotational dynamometer is a device that resists, controls and measures the torque produced by a prime mover. It also measures the rotational speed and thus allows the user (or its own control system) to calculate uncorrected power.

A good quality chassis dyamometer is capable of simulating the road load equation of the car being tested. The most important term to get right is that defining the air resistance which has a velocity squared term: if you get it correctly set it means that at a given wheel speed on the rolls, indicated as a road speed in the vebicle, the engine in loaded as it would be on the road. There are some improtant sources of inaccuracy on the small roll units used by the aftermarket but it is still a valid tool for mapping the ecu.

The advantage of a well calibrated chassis dynamometer is that you are measuring the torque at the drive wheels with the transmission losses measured. Once again there are some important sources of experimental error, the most under-estimated being that caused by slightly different diameters of the drive wheel tyres when fitted to a LSD car.

An engine dynamometer measures the torque at the flywheel.

[Billy Bonkers]

From what you said I personally wouldn't bother with a rolling road setting at this stage. You are only setting it up for the 500 miles running in period.

 

If, as you say, you're confident and happy with the timing and jetting but it's spitting back then the only thing you might want to do is adjust the idle mixtures. Your local garage will probably let you use their gas analyser for half an hour to check and adjust the mixture if you want.

 

I'd get it tuned on the rolling road after it's run in.

 

Bear in mind that you might also need to re torque the head bolts and reset the valve clearances at some point in the running in period. I'd do that before rolling road technician does his stuff

 

The technician will adjust your timing and carbs (replacing fuel jets and air corrector tubes as required) to give as near as possible optimum performance throughout the operating range of the engine. He uses feedback from exhaust gas analysis, ignition and engine speed data, and from the torque applied to the rollers by the car wheels driving them. Unless you specifically ask him he will not be inclined to experiment with alternative sizes of intake chokes because he'd have to set up all the jets for each venturi, and that takes ages. Some places don't charge for replacement jets etc, others make a nominal charge.

 

Power at the wheels is a calculated function of measured torque and rpm. The only mechanical aspect of your car's performance the rolling road machine measures is torque at the wheels, and that is subject to calibration of the machinery, which is always suspect. I wouldn't trust the quoted numbers but it's still a very good tool for optimising performance since it's only relative measurements that are needed.

 

Engine flywheel power is often also quoted after a rolling road session following correction for transmission losses, but I wouldn't take it too seriously. They will claim that the computer has measured and corrected for the transmission losses by allowing the car to freewheel to a standstill. It's an estimate, and is there to make you feel good.

 

[Terry Field]

Billy, That's just the sort of stuff I wanted to know - thanks

 

Terry

 

Q783 OOR. Team Lotus colours with flares.