Rolling Road Results

that was corrected for a very hot intake temp. A very clever set of rollers

Yes, most RR's have it, its a fudge factor..but at least it is there on paper that it made 222 at the fly.

That corrected figure is just for the temp at the air filter it doesn't take into account the 40 centrigrade increase in charge temp over what the engine normally sees on the road - worth another 20bhp easily. And as I said these rollers read very low the 43bhp transmition loss is much lower than I've ever seen on the rollers for a car with a UN1 gearbox - 50-60 bhp normally in my experience. I'd like to get a standard car on there and see what it puts out - I'd lay money it would be well under 200 bhp. The 190 kw at the wheels uncorrected is 255 bhp more at the wheels - more than an A610 has at the flywheel I think thats pretty impressive.

Sorry yes I should ha vebeen clearer, at the intake not at the throttle ie not the MAT reading which WAS effing hot

The DIN standard takes into account air temps going into an engine, but this does not work or apply at all to turbo cars..

For instance, if the ambient temps are 50 degrees, then any N/A car has air going into the engine at 50 degrees, but on a turbo car, air temp at the inlet has nothing to do with air temp in the engine, as we all run different levels of intercooling, one car may have 80 degrees, the other may have 60, so no 'correction' factor is accurate on a turbo setup, hence why most people ignore it..


The figure measured for transmission loss is academic, as you have an 'at the wheels figure'. Now any ATW figure is the total of everything combined - you only need the transmission loss run, to tell you specifically what the trans losses were, but it all equals the same. If the power at the wheels is 190 and the losses 30, then its no different to the losses being 60 and the power at the wheels being 160. It all equals the same.

on a turbo car, air temp at the inlet has nothing to do with air temp in the engine,

Our survey says......

Not true. Drop the inlet temp by 20 degrees and you'll drop the charged temp by 20 degrees (roughly speaking) because the same temperature air flows over your intercooler as goes into the intake!

If what you're saying were true, then Tony should be seeing the same MAT reading on the rollers or on the road.... and there's a yawning chasm between them

Tony is understandably interested in "proving" flywheel figures because that is what is so often banded around, not least by yourself.

[stephendell]

What are we all sitting up so late talking about horsepower for!!

By the way have you seen the lastest user 91tbrick's interests in his profile Be afraid... be very afraid...

My understandng is that the uncorrected figure is the actual power on the day, while the corrected power is the potential power all things being equal used for direct comparison with vehicles tested on different days or at different rolling roads.

While we are all in anorak mode seems there are plenty of different standards.. When is a horsepower not a horsepower...

A little light reading:

http://www.dynamometer.fsnet.co.uk/why- ... gh-low.htm

Not so light:

http://www.scielo.br/scielo.php?pid=S16 ... ci_arttext

And somewhere in between:

http://neptune.spacebears.com/opine/horsepwr.html

I think Tony has the right idea. The rolling road he used is pretty local to a few of the GTA's in the South East. Maybe when enough are on form we can have a rolling road day and see what some of the standard and modded cars produce on the same day on the same rollers. If we get some magazine interest perhaps they might pay for it.

Perhaps we should go and have a few trial runs first though to make sure there aren't too many red faces or disasters

Not true. Drop the inlet temp by 20 degrees and you'll drop the charged temp by 20 degrees (roughly speaking) because the same temperature air flows over your intercooler as goes into the intake!

Martin.....Tony's 'intercooler' (ie, his pre rad for the chargecooler) is at the front of the car, so no where near the '58' degrees at the back of the car...

You're right, I'm off to bed

[stephendell]

Watch out for 91tbrick, he could be hiding underneath with a shovel

Watch out for 91tbrick, he could be hiding underneath with a shovel

He's a Volvo owner - big boot for dumping the bodies...

The DIN standard takes into account air temps going into an engine, but this does not work or apply at all to turbo cars..

For instance, if the ambient temps are 50 degrees, then any N/A car has air going into the engine at 50 degrees, but on a turbo car, air temp at the inlet has nothing to do with air temp in the engine, as we all run different levels of intercooling, one car may have 80 degrees, the other may have 60, so no 'correction' factor is accurate on a turbo setup, hence why most people ignore it..

But the mass airflow temp is measured at the throttle body so surely this is very close to the temp of the air going into the engine - it was 85-90 centigrade on the power run - much to hot to get an accurate reading, when the car is actually on the road it runs 40-50 you can't tell me that won't make a considerable difference to the power. What I also didn't post was that all these figures were taken with an air-locked chargecooler system - it actually boiled after the last measured run and dumped loads of coolant out of its header tank. Doesn't seem to have been working properly since it was reinstalled after the engine build.

The DIN standard takes into account air temps going into an engine, but this does not work or apply at all to turbo cars..

For instance, if the ambient temps are 50 degrees, then any N/A car has air going into the engine at 50 degrees, but on a turbo car, air temp at the inlet has nothing to do with air temp in the engine, as we all run different levels of intercooling, one car may have 80 degrees, the other may have 60, so no 'correction' factor is accurate on a turbo setup, hence why most people ignore it..

But the mass airflow temp is measured at the throttle body so surely this is very close to the temp of the air going into the engine - it was 85-90 centigrade on the power run - much to hot to get an accurate reading, when the car is actually on the road it runs 40-50 you can't tell me that won't make a considerable difference to the power. What I also didn't post was that all these figures were taken with an air-locked chargecooler system - it actually boiled after the last measured run and dumped loads of coolant out of its header tank. Doesn't seem to have been working properly since it was reinstalled after the engine build.

No, if you increase the air temp into an inlet by 20 degrees, you might see a gain of 8 degress on charge as its the temps around the pre-rad which are most important. We can't say what a car could be 'on the road' as if we stuck a normal GTA on the rollers with a standard intercooler, the charge temps would be even higher than yours as there is no airflow through the standard unit, at least a CC still has somekind of coolant flowing through it...

End of the day we can't test for power figures 'on the road' - the only means we have is on a RR, so its the only figures people can use.

that if my car is making 311 on the rollers with everything extremely hot then it is making considerably more than that when I'm out on a clear road on a cool day - we all know how much quicker turbo cars feel on a cool day and the temps these cars reach on the rollers are much higher than on even the hottest summer day. Do you not agree?

that if my car is making 311 on the rollers with everything extremely hot then it is making considerably more than that when I'm out on a clear road on a cool day - we all know how much quicker turbo cars feel on a cool day and the temps these cars reach on the rollers are much higher than on even the hottest summer day. Do you not agree?

Not if there is a bottleneck..

Its not hard to explain, all components have a phyisical flow limit, and I keep going back to turbochargers as a reference..

If we have a turbo that maxes out at 300bhp, and on the rollers the turbo is making 80 degrees chargetemps doing it, then going out on the road when its only 20 degrees does not magically make the turbo do 340. The max it can do is 300, no matter what you do with it..

Likewise you can map a car on the rollers very hot, and think 'it will do alot more on the road' where in reality, the moment you take it on the road it dets straightaway as you needed to advance the ignition so much on the rollers to get the power you can (hence the glowing manifolds in daylight) - Then that amount of advance is too much for 'on the road' 20 degree charge temps so you have to retard it or lower the boost pressure and your back to square one again...

I have loads of friends with Nissan 200's, on the rollers tuned for peak power, then the moment they go on the road, they get det. Cool air is great, but not if you have too much ignition to start with.

What you need to do is get those twin turbo manifolds on your 3.0, then 300bhp + is far easier (as long as then the turbos arent the restriction..)