Power, Torque and rolling roads

[stats007]

It's just that Sym, Graham and myself have all done power runs and the graphs only show our peak power (Hp) output and losses but no torque figures at all.

I asked the guy who operates the rolling road if we could have a torque reading, he just said no and wouldn't explain why.

:bannana:

 

[Dieselman]

Huh!

If you have either the power or the torque figures, and the rpm figures then you can calculate the other figure easily.

Most RR measure the torque and calculate the power from that.

What are you trying to say?

 

[vixpy1]

The hp are torque figs are directly related. one is always calculated from the other. If you know the hp at a particular revs, then you can calculate torque at that point easily.

See not reason why a dyno could not give both torque at the wheels and torque at the flywheel, providing the dyno can be told the gear ratio or has a live tacho monitor. We certainly always give torque figs, thats what most of our customers are interested in!

Autos can cause problems for Dynos sometimes though.

 

[rees_A]

How much is a rr session? and can you get any perf benefits from having one done? ie. can tweaks be made to the setup depending on results to obtain max power. I've a C36 that I've had perf cats put on recently so would like to know if they have made a difference and how much power my car actually has.

 

[GrahamC230K]

How much is a rr session? and can you get any perf benefits from having one done? ie. can tweaks be made to the setup depending on results to obtain max power. I've a C36 that I've had perf cats put on recently so would like to know if they have made a difference and how much power my car actually has.

In my experience a power run session on a decent dyno dynamics RR is about £55. Don't expect any "tuning" unless you are paying more and going somewhere with experience and the equipment for your car.

 

[vixpy1]

How much is a rr session? and can you get any perf benefits from having one done? ie. can tweaks be made to the setup depending on results to obtain max power. I've a C36 that I've had perf cats put on recently so would like to know if they have made a difference and how much power my car actually has.

We charge £42.56+vat for a session. We mainly do diagnostic work, almost all modern cars require remapping to get more power out of modifications. Best way is to simply chip it, but be wary of who chips it . So, yes we can tell you how much power and torque your car has.. and yes we can check the fueling to see if its healthy, yes.. there is very little we can do to the car to make it faster,

I have had a number of requests for a Merc RR day, which would bring the price per car down significantly. Will be having a word with the mods to see if its possible.

Charlie.

 

[Mark300SL]

I have had a number of requests for a Merc RR day, which would bring the price per car down significantly. Will be having a word with the mods to see if its possible.

Charlie.

I'm always up for a RR day ..........

Though I tend to bring the little 1600 FWD thing just to wind people up

Mark

 

[R Phillips]

I thought BHP= torque X RPM divided by 5252 ?

 

[Will]

I thought BHP= torque X RPM divided by 5252 ?

Yep - Mark mentions this on the first page

HTH,

Will

 

[R Phillips]

Sorry, I just read the bit about "what's the point measuring peak torque and quoting BHP"

 

[RichieRuss2000]

Forget the maths...

Lb/Ft is what you feel in the back (G)
Revs is how long you feel it.... :>

Give me 8K revs and 400 LB/ft or whatever the new 6.3 engine delivers!

 

[BenzedUP]

 

[Howard]

Ha Ha - guess you've never seen Marks CRX turbo then......

350 bhp in something weighing 900 kgs , crazy little car, i wouldn't say it sucks..... you should have seen it a Bruntingthorpe......

I've got a video of it chasing a 911 round the track, and reeling it in slowly... both drivers were experienced so it wasn't a question of a good driver versus a bad driver....

 

[Adrian66]

Please forgive the probably stupid question, but what is the ideal setup for torque and power? It sounds like a small engine with less torque can produce the same power as a bigger engine with more torque if you rev the small engine high enough, but does this mean you need to be using 7k+ to keep up with the larger engine? What would tell you that a car can pull hard from stationary without needing 4k and then keep pulling until the rev limiter? Any thoughts on the ultimate compromise? My old 4l chimaera used to go very well from stationary (electrics permitting), but on icy roundabouts it could sometimes get a little too entertaining, and power a little later in the rev range could have been more helpful.

 

[Dieselman]

Please forgive the probably stupid question, but what is the ideal setup for torque and power? It sounds like a small engine with less torque can produce the same power as a bigger engine with more torque if you rev the small engine high enough, but does this mean you need to be using 7k+ to keep up with the larger engine? What would tell you that a car can pull hard from stationary without needing 4k and then keep pulling until the rev limiter? Any thoughts on the ultimate compromise? My old 4l chimaera used to go very well from stationary (electrics permitting), but on icy roundabouts it could sometimes get a little too entertaining, and power a little later in the rev range could have been more helpful.

In reality the old adage is still true.
"people buy cars for the BHP then drive the torque"

BHP is only good for combating the effects of continuous resisitance, e.g. wind resistance, whereas torque gives accelleration.

In other words a car only uses BHP for top speed whereas all other driving conditions use the torque.

 

[andy_cyp]

So when we having a gtg at the rolling road vix ????

Ide love to come there.

 

[yoshii]

what's a horse ? )

 

[Uberwagon]

From how I understand my Traction Control working if a big difference in wheel speed is felt between the front and back it literally turns off 4 cylinders? This is on my 500E.

How would this be gotten round on a rolling road, just disconnect the TC system?

Dave!

 

[Mark300SL]

You shouldn't see wheelspin on the rollers therefore the T/C wont be operating . If it really does break free of the rollers then an accurate measurement cant be taken anyway


Mark

 

[Uberwagon]

It wont break traction, I mean that if there is a speed difference between the front and rear wheels the TC will engage wont it?

Dave!