I recently had the car (99my + Link ) on a rolling road and the analysis showed it to be running very rich on boost which was obviously holding some power back. As the Link was mapped on the road it seems logical that there could be differences due to the operating conditions for each method.
It would be nice to hear of experiences or opinions regarding each method and, if anyone has done both with the same set-up, what differences were found
JohnD

 

John,

You have to be VERY carefull with how you read the fuelling measured on a RR, it can vary dramatically.

Firstly, whilst you can map a car correctly on the road (given enough space !) you cannot map a car correctly on a RR alone. It must be checked, and adjusted on the road, where the car will be driven in it's "real" enviroment.

One major issue, will be the cooling fans, especially if you have a TMIC. I've yet to see a setup than can come close to replicating the airflow we would see on the road.

So, if the IC is running at higher temps than you would see on the road, the intake charge temps are higher, the intake air density lower = less air. Less air = richer AFR.

However, if you have a FMIC, the RR fans will be far more effective, and intake temps will be very similar.

Another issue, will be BOOST. It's very common to see a lower boost limit on the RR, than you would see on the road. In this case, you have a similar problem. Lower boost, less air. Less air, richer AFR.

These things need to be taken into account.

Mark.

 

I mapped a Pug engine once on a Dyno.
It ran ace, then ran like a big pile of poo on the real road.
As said above, cars often run over-rich on the dyno.

A really good MAP will be a combination of road and dyno work.
It would take probably 15-20 hours to get a decent MAP done from scratch.

 

totally agree, all of our competition vehicles are mapped in the 'real world' so that you can replicate the kind of use they'll see, only time we tend to use rollers is to trace faults, etc.
alyn - as performance

 

John

The main problem with the rollers is that you cannot replicate the load impossed on the engine and this is why the boost will often be lower.

If you consider that 4th gear, 20mph to 120mph, takes about 5-6 seconds on the rollers, this would take a lot longer on the road, as a result of the increased resistance. This increased resistance will create high boost and higher temps, both of which will require more fuel to retain safety.

Like Mark said, the rollers can be a valuable mapping tool, but a final map will always need to be achieved from real world conditions.