Peak power RPM difference between Rolling roads

[Greeny.]

Could someone explain why my car would make peak power at different RPM's on different rollers? The obvious explanation I think would be that they were done in a different gear? Can someone confirm? I made peak power at 6500RPM on one set and around 7200RPM on another.

Cheers,
Dan

 

[lesley]

Cold limited? Different rollers

 

[Greeny.]

Around 89mph on one and 112 on the other?! Someone explain to my simple head

 

[Cupman29]

One was in 3rd and one in 4th. 4th is usually the gear used for power runs.

 

[Ian_s]

Are the graphs speed or rpm? 6500 sounds about right, 7200 is too high.

 

[Greeny.]

7200 gave better results, meh.

 

[Grandpa Joe]

I've had this on a previous car. Peak at 6600 when it was mapped and the next place I took it to it was 7000.

Just had my 172 set up on the Pipers and peak is at 6400 on the Dyno Dynamics rollers at RS Tuning.

 

[Dan@SJM]

Could even be down to where the operators calibrated 2000rpm

 

[Greeny.]

I've had this on a previous car. Peak at 6600 when it was mapped and the next place I took it to it was 7000.

Just had my 172 set up on the Pipers and peak is at 6400 on the Dyno Dynamics rollers at RS Tuning.

​What did you get mate?

 

[Chip-mk1]

Probably either on the cold map still like Lesley mentions, or roller/engine speed sync like dan mentions.

 

[Grandpa Joe]

184 bhp and 173 lb/ft. That's with the cams, ported head, 182 manifold, matched inlets and ITG filter behind the headlight.

I could take it on other rollers and make more power though!

 

[Greeny.]

184 bhp and 173 lb/ft. That's with the cams, ported head, 182 manifold, matched inlets and ITG filter behind the headlight.

I could take it on other rollers and make more power though!

Torque figure seams really high for those mods and im sure you could get whatever figure you wanted if you liked Its all about the before and after on the same rollers tbh.

 

[Chip-mk1]

Torque figure seams really high for those mods and im sure you could get whatever figure you wanted if you liked Its all about the before and after on the same rollers tbh.

If you set the rollers sync wrong it will increase torque figures by the same % it lowers rpm by.

People take rolling road results far too seriously without knowing if the person using it actually knows what they are doing, and a lot of them dont, and even the ones who understand often wont be that fussed when its just a quick power run.

Its a tool, and not everyone knows how to use it properly just cause they own one.

Put a 172 on the rollers, rev it to 4K while telling the rollers to sync at 3K, and viola you will get 200lbft of torque at around 4Krpm on your graph, and your peak power will come in about 1200rpm sooner.
Your engine hasnt changed though, just a nonsense result.
Extreme example of course, but its VERY common for the sync to be out by a couple of hundred rpm.

 

[Greeny.]

Ye makes sense, and also makes sense in what I said that a before and after on the same rollers on the same day with the same operator before and after the work has been completed is probably the best way to see if you've gained anything or not.

 

[Adamm.]

Sounds like your worrying too much, chuck the printout in the bin and enjoy the car for what it is. Not all about this or that power, unless your genuinely worried about it being low on power or something I wouldn't worry.

 

[Grandpa Joe]

I got the same figures as Andyman got on the same rollers 4 years ago with the same mods. So maybe its just the way they run them there.

 

[Greeny.]

Im not worried, I was orignally asking why my car made its peak power at different RPM's, which has now been answered Adam.

 

[Chip-mk1]

Ye makes sense, and also makes sense in what I said that a before and after on the same rollers on the same day with the same operator before and after the work has been completed is probably the best way to see if you've gained anything or not.

Unless he WANTS you to have gained something of course (like if its him that has sold you a product or service), in which case there are all manner of ways in which he can make sure it looks like you have done so.

If someone sold you a pill to make your knob longer, would you be happy that it was only them that measured to decide if they had or not with their ruler used how they want to use it?

 

[Greeny.]

If someone sold you a pill to make your knob longer

This is highly unlikely.