Put my car on a RR today...

[The Fatty]

Had a run at Dave Baskervilles rolling road today. He has a MAHA LPS 3000 PKW Rolling Road.

It only had one run, is this normal? For some reason I was expecting it to be done in every gear?

Here's a copy of my printout, apparently 180.4bhp ATF which is good news! But can someone who knows a little more about these calculations tell me if that's correct for an actual reading of 136.8bhp ATW?

Here a video of my run the sound was amazing inside of the building! lol.

 

[Chip-mk1]

On a dyno dynamics which is what I normally use, a reading of 136.8bhp ATW would equate to 161bhp ATF

I dont see how you can possibly be losing as much as 24% of your power through your transmission, unless your clio is 4wd?


ZERO correction factor at this time of year sounds like a load of nonsense too, considering most dynos correct back to 25 degrees, which would be a few degrees minus multiplier on a day like today.

 

[Scottie203]

most places run cars 3 times when just doing power runs mate and he won't run it in every gear,normally they do the run in 4th from about 2k to virtually the red line,seems like you got good figures though

 

[Chris.C]

Car does sound great on there mate,

What's the spec dude?

like chip said the transmission loss does seen quite high though.

I had my car on the rollers the other day too, I wasn't allowed inside the room though
due to their health and safety etc and it was a small room they had to keep all shut etc etc i could only watch through a window llol mine was done on a hub dyno, I ended up with 152.5bhp ATW. No flywheel figure was given though.

 

[The Fatty]

On a dyno dynamics which is what I normally use, a reading of 136.8bhp ATW would equate to 161bhp ATF

I dont see how you can possibly be losing as much as 24% of your power through your transmission, unless your clio is 4wd?


ZERO correction factor at this time of year sounds like a load of nonsense too, considering most dynos correct back to 25 degrees, which would be a few degrees minus multiplier on a day like today.

Thanks Chip. That's what I suspected. I was expecting to have a figure above 145+ ATW. Is it possible to work out what it would have been with the missing correction you mention above? Or is that something that can only be computed at runtime?

most places run cars 3 times when just doing power runs mate and he won't run it in every gear,normally they do the run in 4th from about 2k to virtually the red line,seems like you got good figures though

I think it must have been 4th he was in for it to max out at 110MPH. He only ran it once though

Car does sound great on there mate,

What's the spec dude?

like chip said the transmission loss does seen quite high though.

I had my car on the rollers the other day too, I wasn't allowed inside the room though
due to their health and safety etc and it was a small room they had to keep all shut etc etc i could only watch through a window llol mine was done on a hub dyno, I ended up with 152.5bhp ATW. No flywheel figure was given though.

Its a blueflame exhaust cat-back. Everything else is standard. 152ATW is what I thin mine should be at as well, so I think I might have a problem if that's the case of the RR was not setup right. I might take it to some other chaps in Barnstaple to see what figures they come out with.

Out of interest Chip, where do you get yours done (as your in the SW)?

I have bought a RS Tuner, will this be able to tell me anything useful as to why the power is down if its not related to timing?

 

[Munson]

IIRC dyno runs are best done at a ratio of as close 1:1 as possible, which in most cars is closest to fourth gear.

 

[Chip-mk1]

Correction factor should be something like 0.98 or so on a coldish day, so knock about 3 off the wheels figure to apply it yourself.

But I just wouldnt take any notice of that set of rollers personally.


I tend to use Mtech as its a dyno dynamics, another set in the region are at alan jeffries


I dont actually take too much notice of RR figures though TBH, I just use it as a tool, so long as I have the most that I can when im mapping, thats fine, wouldnt matter if it read in bananas so long as I have more bananas when I come out than go in.

Its pretty daft the way people compare readings from different rollers on different days.

Clios temperature correction algorythm for fuelling on the F4R isnt great either, so you will find that on a hot or a cold day at WOT you actually get slightly different AFR, and hence the engine makes more or less power accordingly, a temp correction factor will attempt to say what the car should have done at a set temperature but if the car isnt running as well in terms of fuelling at one temp as another because the ecu is a bit on the simple side, then its going to effect that figure too.

TBH there are endless reasons why its all just a nonsense really to compare readings from summer on one rollers to winter on another etc, but forums seem to love a figure, lol

 

[Chip-mk1]

IIRC dyno runs are best done at a ratio of as close 1:1 as possible, which in most cars is closest to fourth gear.

Yes on most JC5 boxes the 4th gear is almost directly one to one.

But it depends on your rpm and final drive if that is suited to the rollers or not, if you have a car where 1:1 ratio in the box means its at nearly 200mph on the rollers like my mates cossie is (uncommon but just an example) then the rollers will end up outside of the speed that they are accurately calibrated for as well, so it needs to be a compromise between aiming for 1:1 gearing and keeping the simulated road speed sensible.


Bottom line, if you want to know what power your engine makes, tough cause you cant accurately do so, its simply not possible, even if you stick it on an engine dyno it wont be accurate as then it wont be your exhaust and it wont be characteristic of the airflow in your bay etc, all rolling roads should say "somewhere vaguely in the region of" just before the BHP figure IMHO!

 

[Chip-mk1]

PS, the main reason for running up a few times is to check the figures level out, with a standard clio inlet manifold for example they are a massive heat soak in your intake setup, so it takes a few runs to bring them back down to a sensible operating temperature if your car has been idling for ages, it can easily equate to 5 or even 10bhp difference after a few runs.

 

[Munson]

And thus I'd never take my car to a rolling road. I just don't get it. I'm happy knowing that, to me at least, it's fast. When I switch from my OEM 350ps map, to my 375ps map, I can feel the difference at higher rpms. I don't need a printout. Even if, in reality, my 375 map is making "360"...who cares. The number means little, and the drive means everything.

 

[The Fatty]

hmm. At 136.8 ATWs though (even if the numbers are not directly comparable to others), does this not indicate that something isn't right on the engine?

 

[Chip-mk1]

More likely it just indicates something not right with the rollers.

Dan put his RS2 and 197 cams clio on the rollers at TSR recently and got a similar difference between wheels and flywheel which would have me questioning the rollers, but he knows that its 24bhp more on the same rollers than his old clio did, so a good indication that its making the sort of power he hoped for (168 for his old one, 192 for the new one)

Best way to see if yours is putting out what it should, go to a RR day with other clios, same rollers on the same day should make for a good comparison.

 

[Owen_m]

Dyno will give you a true figure of the engine its self. Not of the engine with limiting factors such as exhaust/intake...

we have a 5% margin for results, there calibrated dyno's so thats a fairly true, figure of what an engines power is. unlike a rolling road like chip said

if i was tuning an engine, i'd be using the same dyno every time so you can get a true idea of what you gained. not a false one from using different dynos.

 

[The Fatty]

Dyno will give you a true figure of the engine its self. Not of the engine with limiting factors such as exhaust/intake...

we have a 5% margin for results, there calibrated dyno's so thats a fairly true, figure of what an engines power is. unlike a rolling road like chip said

if i was tuning an engine, i'd be using the same dyno every time so you can get a true idea of what you gained. not a false one from using different dynos.

Is that not a false high though? Surely you wan to know how much power it give WITH the limiting factors?

 

[Owen_m]

well the way i see it is, its what the engine is truly capable of. Which i personally think is better to know. Also the factory horsepower figure will have been worked out on a dyno. (how there exhausts etc were set up for testing i don't no). I just feel it give you a better representation of the power of the engine.

By false high, i meant if you're using different RR's every time, you change something and map it. the margin for error is bigger so i would use the same rolling roads each time? like scales.

I could weigh 13stone on one set and 14 stone on another set. well thats my reasoning anyways.

 

[Chip-mk1]

Is that not a false high though? Surely you wan to know how much power it give WITH the limiting factors?

But then you have a gearbox in the way, so you cant measure it accurately anymore, lol

On some dynos people do actually fit the complete exhaust and intake system, but it still doesnt mimick the airflow etc.

 

[Owen_m]

Is airflow really going to make that much difference? surely were only talking about the 1/2 horsepower thats accounted for within the error of the dyno?

 

[Chip-mk1]

Is airflow really going to make that much difference? surely were only talking about the 1/2 horsepower thats accounted for within the error of the dyno?

Depends on the car and on its intake setup and what speed you are talking about, not ever going to be a huge amount though, was just giving an example of yet another way in which a dyno and the real world differ.

Bottom line is, dyno is VERY useful for tuning an engine to be the best it can be, and a reasonable indication of approx how much power it makes.

 

[Owen_m]

Totally agree chip. Aim for the best power on the dyno and the rewards will be reaped in the car.
I've only ever tested diesels for ships and trucks and stuff like that. (apprentice) love it though. So air flow isn't an issue when you have a massive turbo.

 

[.Kev.]

Got to love the old Bum dyno, the car feels quicker so it must be ok.

 

[Owen_m]

Totally agree chip. Aim for the best power on the dyno and the rewards will be reaped in the car.
I've only ever tested diesels for ships and trucks and stuff like that. (apprentice) love it though. So air flow isn't an issue when you have a massive turbo.

 

[Dan519]

typical MAHA loses tbh. Powerstation does the same or worse. Bad system.

 

[Gary172cup]

Sorry to spam but owen m empty your inbox please.

 

[jjones82]

MAHA dyno's - these (it's said) are set up to accurately measure flywheel power and always produce much lower "at the wheels" numbers than other dyno types. To quote from another forum:-

"The maha dynos have 2 contact patches per wheel. What the maha does is measure how quickly the car can spin the dyno and produce a "power at the dyno" figure. This figure should ideally be ignored as its not a power at the wheels figure. Its called wheel power on the dyno chart, but the thing to remember the dyno has 2 contact patches per wheel. Your car on the road doesnt."

 

[SharkyUK]

Don't pay attention to the ATW reading as MAHA does things differently (in terms of calculations); this isn't the actual wheel power of your car. I posted up a full explanation elsewhere on another thread but can't find it at the moment. I'll post up if I can find it.

EDIT: Found the post. Here's the explanation I was provided with (using one of my old dyno charts as an example).

The important values to note are the Wheel Power (PWheel) and Drag Power (PDrag). The two values are added together to arrive at the Engine Power (PEng).

PEng = PWheel + PDrag

Once the engine power is known, it is then normalised (corrected) to give a flywheel horsepower value - in this case the Corrected Power (PNorm).

It is the PNorm flywheel value that is of interest because the PWheel value is NOT an at the wheel power figure (as is typical when usually talking about dyno readings, hence the source of confusion).

Once the power run has hit the apex (the point at which peak power has been made), the operator clutches in and selects neutral - the vehicle gradually coasting to a standstill. During this coasting phase, the dyno measures the drag due to losses through gearbox, diff dearings, etc. and - most importantly - the tyres against the rollers. It is important to note that the drag is huge on the rollers and more so than experienced when on the road! The reason being that (on the road) the tyre sits flat against the road surface with a single contact patch. On the rollers it has two contact patches either side of the tyre which causes additional deformation and increased drag.

The drag curve is measured with the MAHA system (rather than calculated) and is exponential. The curve will get steeper the faster the car goes. And without the drag curve, the PWheel figure is meaningless (and often the source of confusion!)

Cheers!

 

[The Fatty]

Thank-you very much for that sharky, saved me another run on another RR! Using your chart, my Pnorm must also be around 182.X as well as your figures are very close, so very happy with that.

 

[SharkyUK]

Thank-you very much for that sharky, saved me another run on another RR! Using your chart, my Pnorm must also be around 182.X as well as your figures are very close, so very happy with that.

No problem, mate.

I used the MAHA rollers at PowerStation (which are known to be a little bit generous) but seemingly consistent over the years I've been going there. It's the consistency I've been interested in as I can reasonably gauge the effectiveness of mod's I've had done (rather than just chasing the figures). That's why there are 3 lines on my graph - highlighting that my mod's have seen steady improvements each time. Anyways, I digress... LOL!

Cheers.

 

[Chip-mk1]

The problem with the dipping the clutch and measuring the losses way of doing things is that the losses when running down arent the same as the losses when under load.

For example, take your clio, add a 100bhp nitrous kit to it.

Run it up on the rollers, and it WILL be losing more power through the transmission now as the cogs are pressed harder together and hence generate more friction, but the moment you dip your clutch, it will measure the losses the same as it did before the nitrous was fitted as on the run down it will make no difference.

Extreme example of course, but applies equally to any other reason one engine makes more power than another (cams, mapping whatever)

Thats why I like the dyno dynamics, it already KNOWS it wont be able to make the measurement accurately, so doesnt even bother trying and instead just adds a fixed percentage known to be vaguely in the correct ballpark.


As you say though and as I have already mentioned too ,when developin a car/engine all that matters is that you keep measuring the same way, and see if things improve or not, just dont then try and compare it to another set of rollers where it could read 10bhp different for exactly the same engine.

 

[The Fatty]

Yes I understand and agree with the consistency being the key point Now Sharky has explained why the ATF figure is so low, at least now I know my car's timing is out (which was the goal of this exercise as I was worried it was underpowered). Means I can get on with doing other things to it instead of worrying about getting the timing/cambelt changed again Chip I want a turbo wont be able to afford it for a while though, hopefully that kit you talked about will be finished and in production by then

 

[Dan@SJM]

More likely it just indicates something not right with the rollers.

Dan put his RS2 and 197 cams clio on the rollers at TSR recently and got a similar difference between wheels and flywheel which would have me questioning the rollers, but he knows that its 24bhp more on the same rollers than his old clio did, so a good indication that its making the sort of power he hoped for (168 for his old one, 192 for the new one)

Best way to see if yours is putting out what it should, go to a RR day with other clios, same rollers on the same day should make for a good comparison.

It was a MAHA dyno too.