FrenchBoy

Got this today,
my apologies if anyone has seen it before.

There are some interesting points raised.

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Subaru
Technical Service Bulletin

Subject: PPP Tests
Model: Sti

We are becoming increasingly aware that owners of the above vehicles and others equipped with a PPP are taking their vehicles for a rolling road test and being advised of varying results on power output.

A rolling road test is very difficult to rely on to give an absolute figure of the output an engine is producing particularly when it is only possible to measure at the road wheels instead of the flywheel. There are also too many variables in how the test is undertaken including how much air is being blown at the car, which is rarely sufficient and the temperature at the intake/intercooler.

As a precaution against engine damage, the PPP is designed to reduce boost if the intake temperature becomes too high and this occurs as soon as 40 degrees is achieved. This can occur for example whilst a vehicle is parked for no more than a few minutes, even when the ambient temperature is low. For example, in a 4 degree ambient the intake temperature can rise to 51 degrees after 11 minutes with engine merely idling. This could easily happen prior to a vehicle being rolling road tested unless it was being monitored properly to ensure everything had re-stabilised, otherwise the engine power data obtained is unrepresentative.

When our supplier undertakes tests on rollers the figures quoted for a Sti (302bhp/305ps) are consistently obtained but this is only after making absolutely certain everything is as it should be before commencing. If the intake temperature is too high, a Sti will typically provide indications of only 285bhp/290ps very easily. An owner is then of the impression that his vehicle is under performing!

If you receive a complaint of this nature, the owner should be in a position to provide a rolling road test data log. Should it be apparent that the test was carried out with intake temperatures at or above 40 degrees an owner should be advised why the test results show a lower output than anticipated.
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Jiggerypokery

So, does anyone have RR figures which show 285bhp or less with an intake temperature of <40 ?

DBY

Over the last twelve months there have been loads of people posting on here my" 03 STI only made 275/285 on so and so rollers". Mike Wood from Prodrive then posts about the potential problem of heat soak as per the tech article above, Then you min't get people taking the **** about this problem as it's well known.

Regards

John

TonyBurns

iTrader: (3)

Does this mean that my scoob has considerably more power than a PPP'd car then
All scoobs will cut the boost back when the temps get high, its common sense if you dont want to blow your engine up, the 2 PPP'd STi's that ran on sunday were both around the 285 mark, one a MY02 and the other an MY03, their torque figures were impressive though with both being over 300lbs.

Tony

STi wanna Subaru

iTrader: (1)

Tony, are you ill???? A perfect chance to tell the world what scoob you have and you didn't!!

Dazza's-STi

I was a little concerned about my car and was wondering if my 2k had been spent wisely...

I RR it just for that reason, not simply relying on Subaru's word that it made the figures...
As it was the car ran 313bhp on a cold morning, i hadn't left the car running so soak was negligable... just a quick warm up before the rollers... I was a bit dissapointed was the torque figure of 275 though ... not sure the reason behind this... i was wondering if someone with some engine knowlege could explain...
Dazza

PS it was running on optimax at the time, and no other additives.

MJW

I can't understand why people place so much faith in RR's given the substantial differences in results between each respective RR. It's like measuring your d1ck ... you really want it to be mahooosive but will ultimately be disappointed with the actual figure

StevietheG

I agree with MJW.....there are too many variables to compare like for like.

Mike Wood stressed that they are in control of every aspect of the RR testing before they proceed. I wouldn't pay any attention to output figures as long as boost is correct the power is there!

ozzy

I can see why some people may feel like complaining. Their idea of having the car RR'd is to provide some evidence if it's performing or not. I agree the tests have too many variables to be taken as Gospel.

Still leaves some doubt between "ideal condition" figures and real-life. If you spend £2K for 300bhp upgrade, you'd like to belive this is actually achievable in normal everyday conditions. OK, you don't expect the same results in mid-summer to mid-winter, but the PPP is sold and marketed on it's figures.

Stefan

Neilo

Frenchboy.....when you put yours on the rollers a few weeks back....what was the torque figure that you got? I forgot to ask you at the time but would be interested to know as although the bhp on mine was significantly up, the torque wasnt, so was wondering if your torque was up but bhp wasnt?? if you get what i mean!!

Mine was 234lbft.

Cheers,
Neil.

Dazza's-STi

How would i be able to tell i have the boost correct...? accuratly?

Neilo

I think at the end of the day its how the car feels to you to tell you if the money was justified.....i think a lot of the problem lies in the fact that people are having the PPP fitted before they actually get the car so they dont even know what a "standard" one is like....and consequently they do not know the difference the PPP provides.

Just my thoughts...

Neil

johnfelstead

Ah but Tony, thats the whole point, they all DONT cut back boost when they get hot. Prodrive as part of the PPP remap have changed the factory settings with regards to inlet temp compensation, a stock STi will still try and produce full boost irespective of inlet temp.

It's a pretty rubish setup as a whole anyway on the Subaru engines with regards to monitoring inlet temps, as there is no charge temp sensor on these engines, and it's charge temp you should be monitoring and compensating for, not air filter inlet air temp. The only plus side of monitoring air filter inlet temp is you are being kind to the turbo, as the hotter thinner air needs to be worked harder by the turbo to produce the boost, so it will be saving the turbo life a little. But with regards to det protection, inlet temp doesnt matter, it's charge temp that really matters, and the Subaru ECU doesnt monitor that. They are obviously relying on the active knock control strategy to control det, which is a very clever setup, but also a bit risky as you are compensating for a problem (ie a detting engine telling the ECU to back the ignition off via knock count levels) rather than stopping the engine detting pro-actively by dropping boost when charge temp increases.

You also find when you RR an engine, as the rpm rises the inlet temp reading drops, because the air rushing past the sensor cools it, at the same time the charge temp is skyrocketing, because the turbo is working the air harder as the boost climbs. So from that alone it's a backwards setup too really. Get a delta dash log done on your engine when you drive on the road too, inlet temp drops as you go up through the revs, when you change gear inlet temp jumps up in a spike and then starts to drop again as the rpm rises again.

It's a good idea to install a charge temp gauge on your car IMHO, as that tech bulitin shows, sitting in trafic makes the temp rise quickly due to heat soak of the IC, it will go above 70 degrees in a few minutes on a summers day, half a mile of light throttle driving will drop that back to 30 degrees, so it teaches you to be kind to your car if you know what is going on.

So in summary. The PPP setup is doing the best it can to protect the engine with the level of sensor input available, but Subaru really should install charge temp sensors on these engines, that would be a much safer strategy IMHO.

johnfelstead

Buy a boost gauge, SECS monitor or Delta Dash. Delta Dash will tell you most acurately, as you are logging the engines parameters in real time.

StevietheG

Dealers can drive car with select monitor, preferably two people in car, floor throttle in 2nd or 3rd and this should show boost pressure in graph function. Think it should be 18.1!! But at 313 bhp..........wow! Do you need to check???!!!

MadMark

Yup it is a well known problem - and you can sometimes feel the power ramp back up again when pulling away from traffic lights where you have been stationary for a while!

As regards G-Force - they run the cars bonnet up with the biggest cooling fan / extraction system I have ever seen and they have a probe that measures intake temp etc - so I simply don't believe that Prodrive or Subaru can completely hide behind this.

A PPP STi that produces 285 instead of 305bhp is a difference of 4.92%
A WRX that produces 224 instead of 261bhp is 14% down ....

Trades Descriptions Act anyone???

MadMark

OK - Same RR that French Boy used - my standard 03 WRX (with only a Prodrive BackBox), produces 260bhp!!

Please explain .......

FrenchBoy

Neil,

my torque figure was almost exactly the same as my power output.

The intake temperature was 20 degrees.

StevietheG

Exactly the point! There is no rhyme nor reason to the figures!

wrxmania

224BHP is the standard for a WRX???? although many have made much more on the rollers with very little if anything done.

Mine made 240 with a backbox when the car was new.

In reality, it is all figures for a car used on the road in standard road conditions. I know people want what they pay for but telling the difference in normal driving between 285BHP and 300 must be a challenge for even the best driver.

I may be wrong.


Brian.

FrenchBoy

Brian,

Mark was reffering to a WRX ppp (261bhp - claimed)

micared

Imo, if more people were to follow johnfelsteads advice about monitoring charge temps, the world would be a safer place for the subaru engine...It's relatively easy to rig up the equipment to do this, and, in my case, has certainly had a profound effect on the way I treat the car above certain temps. Excellent advice, john.

MadMark

Yup -sorry should have pointed that out ....... MM

Jiggerypokery

"A PPP STi that produces 285 instead of 305bhp is a difference of 4.92%"

-6.55%

Jiggerypokery

Not really I can tell when I have the aircon on in my WRX03PPP without looking at the switch.

MadMark

Whoops quite right - input wrong numbers ..... point is still the same - big difference! Not

wrxmania

Whoops,



Stupid me - get you now,

Brian.