Mr DJ

Hi all, as anyone had their car tested on a rolling road?
subaru quotes 265ps and 257lb ft torque about 261bhp after ppp mine only got 242bhp and 240 lb ft,
very upset! so i took it back to my dealer who run the usual plug in thing. and gave it the all clear, they changed a valve as a matter of course but said it was ok before.

Any one help, Mr prodrive would be nice?

Regards ,Darren

Bob Rawle

where was it rolling roaded ?
bob

korky

My 02 STi PPP was recently rolling roaded near York and gave only 280PS although torque was nearer the mark.

I would suggest inaccurate RR as the car should deliver as near as damn it the book figures (subject to petrol and atmospheric conditions)

Just my tuppence worth!

Korky

Mr DJ

The rolling Road was done at Engine Advantages in whitam Essex run on optimax from new 7000 miles now, also a cold sunday morning, with many other cars, all seemed to reach expected outputs and most over. brand new roller (seemed to still have the stickers on)

perfect morning realy i guess.

I will be contacting E/A to ask if they have any certification but as my car was the only one to come up low I dont no what that will achive, but at least I will be able to forward this to prodrive when they sugest the RR was inaccurate.

Regards Darren

FLAT ERIC

iTrader: (1)

This has cropped up before with the rollers at EA (Page 6 & 7).
LOW READINGS HERE

Your readings should get better as the miles build up though.

This was mine on 28 June this year at Power Engineering :-
Mark (Flat Eric) 03 Stealth Wagon - 247bhp / 249lb/ft torque
Mods: PPP (<4,000 miles & on a hot day)

And this was on 15 Nov this year at Power Engineering :-
Mark (Flat Eric) 03 Stealth Wagon - 253bhp / 252lb/ft torque
Mods: PPP (>8,000 miles & on a cooler day)

As you can see the figures are rising with the miles.Still not got the 260 horses that Prodrive say are in there,but it's early days yet & we are heading the right way.

Mark.



[Edited by FLAT ERIC - 12/16/2003 1:41:14 AM]

Butty

iTrader: (2)

I too had "low" results at EA using "untypical" transmission losses.
My Forester had 168 bhp at the wheels and got converted to be 203 FW bhp/ 187 lbft.
A trip to PE next month again saw 169 ATW but they made it into 259 FW/ 236 lbft .
The transmission loss curve used then impacts on your torque figure.

What ATW figure did you get? Compare that with ATW figures on dynoscoobynet and this may make you feel better

Nick

[Edited by Butty - 12/16/2003 10:15:13 AM]

Scratch

iTrader: (1)

Pbone also had low readings there too. I think they said 240BHP or some from Sti8 PPP, and suggested he take it back to the dealer. He got 303BHP a couple of weeks ago at PE.

My MY98 got 171 at the wheels which they equated to 203 at the flywheel which is way off the mark. RiSKy's WRX got 175 at the wheels at GForce which they equated to 247 or so at the flywheel.

EA are way out for flywheel figures.

MadMark

I have been debating the PPP and was at the same RR day as Flat Eric - but my car (03 WRX) got 252bhp and 235lb/ft of torque and it's bog standard except for a Prodrive backbox and a Green Cotton panel filter ....

Jza

HEAT SOAK!!!

Jza

Jiggerypokery

Get a mug, or a friend, to spray this on your i/c during the test, then you can't blame heatsoak. Just make sure to keep it away from the air intake.

DaveR5gtt

The problem here is the fact that you will never get a true reading from a rolling road, the Hp is just a calculation which is difficult to get spot on but very easy to get way out, best way is to find out what a std motor should produce at the wheels (subaru figures) and work on that.

Heats soak also plays a big part with turbo'd motors on the rr's

Dave

Mr DJ

Thank everyone for your replies, Jza and dave don`t want to sound thick but whats heat soak?
On the day I took my car to E/A it was a very cold morning so more dence air and surely more BHP?
also on the day RB5 250bhp/inport wrx with filter and back box 262bhp? type R 290bhp and the list when on all around or better than expected, so either they were all on a good day and i was having a nightmare, or prodrive dont do what they say!
Thanks again for all your replies will give it some thought.

Regards, Darren

hades

Any number of things can throw off rolling road figures. You can get a few bhp difference in measured power by altering tyre pressures. The one that really surprised me was seeing a slightly modded early STi gain something like 30bhp on the same RR on the same day. All he did was got his suspension geometry put right, as the power wasn't going down square onto the rollers first time round. Incorrect calculation of gear ratio can also sod up your torque figures, as I found out when I mysteriously "lost" 20 lbft - it's only when I compared curves I discovered the problem.

If the car is running right on the road, that is much more important IMHO than "pub talk" figures it gives on the rollers.

Edit to correct muppet mistakes with the bold etc I should go to bed!

[Edited by hades - 12/17/2003 11:58:47 PM]

DaveR5gtt

Like hades has said there are many diffent variables when it comes to rolling roads inc your tire pressure.

heat soat is where the heat from the block etc transfers to the outer elements of the car including compression housing and intercooler, thus making the air hotter than normal entering the engine. this can often be felt after sitting traffic and as you pull away the car doesn't seem as quick to pick up.

At the end of the day All RR results have to be taken with a pince of salt, the only true BHP reading is from a dyno bench.

Cheers

Dave

TonyBurns

iTrader: (3)

If it feels great on the road then there isnt a problem
most RR are very inacurate, and your biggest benefit is airflow which your not getting.

Tony

JackClark

I agree with Dave, why don't people use the wheel figures? Mine got 180.5 at the wheels - 01 PPP.

RB5SCOTT

Engine Advantages rollers are reading about the same as Power engineering now! They were wrong as they were reading low but have since been calibrated.

I should know i was the test car, 382bhp 314lb/ft at power engineering and on the same day i got 381.5bhp 322lb/ft on Engine advantages rollers since they had been calibrated.

PPP on wrx's have always performed low on rollers, Prodrive claim they have correct figures, i think they are figures from a bench dyno. You have also got to remember that maximum boost is rarely reach on the rollers

Mr DJ

Thanks all again, my tyre preesures were cheked the day before, geometry don`t no but guess its ok and at the wheel about 195 bhp ish by my graph and 240 lb ft @ 6230 rpm.
I would be intrested when you had your car tested Scott for calibration and who actually certificates the figures,is it an officiall body or self regulating.
Can any one tell me where i can have the geometry check other than subaru. I live about 1 minute from scoobysports in Basildon.

Thanks Again
Regards Darren

hades

In which case, speak to scoobysports or xtreme scoobies, either should be able to sort you out. Whilst it may improve your RR figures (but make no difference at all to the actual pwoer), you'll notice a lot bigger improvement in the handling if your geometry is put right.

Scott's car must have done the test on both rollers around late October; it had gone a step further (or a step too far? ) at the PE RR day on 12 Novmber.

johnfelstead

On the STi8 PPP the inlet temperature of the air as it enters the turbo is measured, it uses the temp sensor in the MAF to do this. Not sure if the WRX PPP has the same setup, maybe bob or mike wood can confirm but i would suspect it does.

Prodrive has set the PPP so that when the inlet temp (not charge temp!) gets to 40 degrees c it reduces the maximum boost the engine can run, this is done to protect the engine from det and this is why they can waranty the engine for 3 years without doing a custom to the car remap. Remember this is an off the shelf remap and all engines do differ slightly. If you were getting a custom remap there would be less need for this 40 degrees safety boost cut.

So the important thing for you when RR a PPP is to get good airflow to the airbox inlet if you want to see good power, it is not charge temp related boost cut, charge temp is not measured by the ECU.

The most eficient way to drop the inlet temp when doing a RR is to ram air the airbox inlet and then to run the car on partial throttle for 2 minutes at 2000rpm, this cools down the intercooler from around 70 degrees to 15 degrees, by the end of a power run its going to be back up to 40 degrees charge temp.

Try this and i bet you will see a jump in power.

RB5SCOTT

John i can't see the maf reaching temperatures of 40degrees at this time of year. I would of thought that things would have to get extremely hot for the maf to read that high because all its doing is sucking ambient air through the filter.

EA have quite a powerful fan too

johnfelstead

Maybe Scott, its surprising how much heat soak you can get into the airbox from letting these cars sit idling though, which you have to do prior to the RR run to get oil/water temp into safe regions. It's usefull to have access to a delta dash, as you can then monitor intake temp and make sure heat soak of the intake isnt an issue before the power run.

RB5SCOTT

Mmmm the glory of deltadash or secs

Mr DJ

Scott and John.
This all sound good but on the day (a very cold day might I add, low single figures) all the other cars were run the same,left runing about the same(a few minutes) and all had about a 12 mile run 20 minuets before the test,from the same meeting point.
I must agree that an off the shelf item will be variable but £1600 for an easily achieved 22bhp insted of 40 as quoted! Just a little upset. I wonder if this is legal advertising, should they not say between 20 and 60bhp increase depends on how your luck`s going?

Thank for listening to my moaning and all the advise.
had the car`s geo checked, all ok.

Regards Darren

chrisp

How many miles has the car done, impreza need upto 10K to really loosen up ?


[Edited by chrisp - 12/20/2003 5:51:55 PM]

Bob Rawle

I think the trip point for boost reduction is 38 degrees, its very easy to see that on a rolling road, you only need the fans to come on once and bingo, as a suggestion take it to PE and get a comparitor done, if Merv is around (Ecutek) he can Deltadash it and confirm that this is happening or not.

There are many reasons for low power, the ecu is only one of them.

An engine dyno is just a likely to be inaccurate (read different) on a cell by cell basis as anything else. Same rules apply, find one and stick to it ... use as comparitor only. There are cells around that could be considered "accurate" but they live in the premises of Formula one companies and the like in the main. Accuracy is about traceability to a recognised standard, unless you can do that then the statement can't be made, callibrated is not accuracy I'm afraid as it usually means within manufacturers spec not a traceable standard. (NPL or the like)

Bob

Mr DJ

Crisp is at 7000 miles now
regards Darren

chrisp

7000 is still pretty low for the engine to be fully loosened up.