carlos_hiraoka

..... a good way to test the "power" figures of your cars, maybe running on the track (on the straight lines) against a proper track car ..... something like a 911 GT3 RS, with roughly 420bhp (because of the two 30 mm air restrictors) or a 911 GT3 Cup, 380 bhp, car. Both can be bought through your local PORSCHE dealer



Carlos H.

[Edited by carlos_hiraoka - 7/1/2002 6:46:09 PM]

Mellow Yellow !

iTrader: (1)

Mmmmm.....

Just back from Well Lane with the posse after a group rolling road day and achieved far less than expected.

I was told this though.....

Rollers are set up for rear wheel, front wheel and AWD cars....it is difficult to measure the true power on RA's due to the electronic centre diff ???? i.e; the power is not equal to all corners ?

Hey, what do I know.

It's true to say that many cars did not meet their expected torque figs which then lead the operator to assume a recuring problem with the rollers elements (or something)

I achieved a mere 289 lbs torque @ 333 bhp !

Bearing in mind the mods I have this was of course dissapointing.

Thoughts

Andy.F

If you lock the centre diff it should be OK ?

Is it Well lane that has the long duration run ? 40 -50 seconds ?

Also, what was the temperature compensation ? (Pf - Pn)

Andy

johnfelstead

run the diff set open on the TypeRA.

I dont see why youre that disapointed chris, you dont have anything on the car that would warrant you seeing much more than that. Scoobs dont do torque.

I think the power is quite respectable considering the mods you have. FMIC dont give you more power, they just make it more consistent when temperatures build, the limiting factor is how much air the turbo can breath, not the type of intercooler you have. Standard headers wont flow much more than you got either.

Dont forget, in standard spec the STi5 only produces 280BHP, it doesnt have the quoted 300PS.

Mellow Yellow !

iTrader: (1)

Mmmmm....

I suggested locking but they were against that.

I appreciate your thoughts John but I'd have thought the mods currently on the car i.e; MD 191 Turbo, 550 injectors, FMIC, uprated fuel pump/oil pump, GEMS ECU, etc...would've given me a lot more

Maybe not....

As always it feels so much quicker on the road as we both know, I s'pose the power gains over money spent don't seem beneficial

Going back to my P1 days my engine was STD apart from panel filter and zorst and concentrated on it's handling,that did OK....this time I thought I'd go for both set up AND power = unbeatable

johnfelstead

take a look at Matt Oz's power plot for a standard STi5 typeR using an open diff http://dyno.scoobynet.co.uk/PSjap/matt_osborne.htm and you will see the REAL gains you have made. Matt's car was superb, it's engine felt exactly like mine does at the moment, i drove his car and remember the feel of it well.

As you know, rolling roads are hopeless at giving you real true data, so dont be too cheesed off as on the road your car is a big improvement over standard, you know that from the side by side test we did!

The problem these days is that everyone is claiming big BHP and torque and 95% of those claims are bull$hit. What you have with your setup, especially now you have the gems, is a safe engine that has a great delivery of power, thats what really matters.

The FMIC gives bugger all power and can increase lag, what it does give is a consistent power that wont drop away as the laps on track increases.

By the way, we need to do another side by side test as i just replaced my filter, which was filthy! I have also got the Automatic intercooler sprays working, some muppet had plugged the wrong connector into the Auto Switch, i wouldnt be at all surprised if its been like that since new, probably done when they wired up the rear fog light switch. It now Eats water!

Mellow Yellow !

iTrader: (1)

dhorwich

mellow,

Did anyone get any pics from the RR day at well lane..!!

Dan

mikeesingh

iTrader: (3)

chris, what boost are you running?
steve normally knocks the boost down above 6000rpm on the gems,
so your BHP wont be very high (mine drops from 1.3bar to 1.1bar after 5800rpm)

mikee

Mellow Yellow !

iTrader: (1)

Pics should be coming up soon

Mike...I'm running 1.5 bar down to 1.3....

I hit 333 bhp with 290 lbs torque....

However and this is a contentious issue methinks...I keep getting told that we should've run the centre diff @ 50/50 and not fully backed off as we did....thus giving it nearer 80% rear wheel drive...

What do I know....I know the thing is far,far quicker than the P1 ever was

Andy.F

Scoobs don't do torque ???????

How come I've got 343 lbft at 1.5 bar on a std turbo then ?? On the same rollers that gives a decat uk 220lbft or a PPP 240lbft.

Conservative mapping me thinks

johnfelstead

I so love the acuracy (or rather lack of it) of rolling roads.

Andy.F

Much preferring the deadly accurate seat o pants meter I presume

submannz

We only use a rolling road to check top speed of the car or to run in an engine.

[Edited by submannz - 7/1/2002 5:14:44 AM]

[Edited by submannz - 7/1/2002 5:15:35 AM]

Mellow Yellow !

iTrader: (1)

Mmmm....

I think in conclusion the readings were not acurate due to a few wrong set ups initially re; my motor....gearing...diff...

However, it feels so much quicker than my P1 ever did and it comes into it's own as you quite rightly pointed out John....on the road and track

That's where it really matters Just watch it go round Donno next Sunday at the SIDC day

mutant_matt

I'm pretty certain PE ran it in Full Diff Lock mode.....

R19KET

Chris,

Just what were you expecting ?

Circa 330bhp from 1.3bar is there, or there abouts. The torque figure is lower than I'd expect, buy I believe Well Lane admitted they had a problem with the torque readings, before they started the day.

Lastly, Steve S whilst having a very good reputation, is also well known for being very conservative.

It also seems that WL weren't loading the RR very much, and people weren't getting the same boost they would see on the road. Two examples would be Steve, and Christian. Steve runs circa 1.5bar, and Christian 1.6bar, but on the RR their boost only reached 1.25, and .95bar respectively !!

Your 1.5/1.3bar, is this on the road, or did you see it on the dyno ?.

Mark.

Steve vRS

R19KET,

Could the theory above explain this thread too?

http://www.scoobynet.co.uk/bbs/threa...hreadid=109141

Regards

Steve

R19KET

Steve,

I assume you ran at Well Lane too, then. I've been led to believe, that WL made it clear (at least to some people) that they had a problem with the torque figures, their dyno was producing, and that they were reading on the "low" side (comparatively).

I suspect that Sundays WL figures are pretty meaningless, but if you want to check a "comparative" torque figure, against the BHP figures, see how this works,

Pick an RPM point, and take the BHP figure, then

5252 x bhp div' rpm = ftlbs.

Also check that bhp/ftlbs cross at 5252 on your dyno graph.

Maybe someone could post a dyno print out from the day.

Mark.

STi wanna Subaru

iTrader: (1)

This was my print out from Well Lane



MY99 UK Turbo, Full De-Cat and a Dawes

STi wanna Subaru

iTrader: (1)

And a quick mess in Paint gives this overlay

Steve vRS

If the torque measurement is out, how can the power figures be accurate seeing as how one has a direct relationship to the other?

Steve

Pavlo

BHP in imp units is defined as you said, so the torque curve will always cross the bhp curve at 5252 or whatever.

The rolling road, or any other dyno measures torque (inertia type measures accel rate to give torque) and speed, and calculates power. This is true of an intertia dyno, water brake or eddy current dyno, all the same. Although an innertia dyno shouldn't read low unless it's drive is knackered. Brake type dynos can read low because the force load cell used to determine torque can be out of calibration due to a number of reasons.

Brake type dynos should be regular calibrated with calibration weights and a torque arm, readings should be corrected for zero offset and slope at the known torque provided by the calibration weights and torque arm.

If the torque is reading low, then so will the BHP. If Well Lane's dyno is reading low torque, then it's reading low, period.

Results should also be corrected for temp, barometric pressure AND humidity (often forgotten when corrected by hand calc).

Paul

R19KET

Well based on the posted graphs, torque, relative to bhp is correct. If there was a problem with torque only, I would expect to see bhp/ftlbs crossing at a strange point, but they don't. I'm no dyno expert, so someone may well be able to correct me.

Paul has correctly stated that bhp, and torque, are directly related to each other. So if the torque figures are incorrect, so are the bhp figures. In this case, allegedly low.

Given that WL said that the torque figures were incorrect, I would totally discount the reliability of ANY power numbers, and purely use them to COMPARE car, to car on the day.

Mark.

Pavlo

Agreed Mark. I know of people that use a benchmark engine (bench dyno) to make a comparative analysis against. It works for them, but I would say the best way is to make sure the dyno/RR is regularly calibrated for speed and torque. Inertia dynos can read low if a bearing goes, introducing an extra load that the software isn't expecting. Although I image that an extra load would show up as additional drivetrain loss.

I'm not too clued up on RRs so maybe someone can shed some light (but I did develop a 30kw eddy current bench dyno for racing karts).

Paul

Andy.F

I think most of the 4 wheel dyno's in the UK are Eddy current type.

The run duration can also change the output, long run = more heat soak, not just to engine components but to tyres which heat up and absorb more power.

I'm with you guys on the torque figure though, it is the torque the rollers measure, then multiply by speed to get power figures.
Or do they ??? Do eddy current units actually measure the power produced by the 'generators' then divide by rpm to get torque ? mmmm, I wonder

Sorry, just having a wee discussion with myself

johnfelstead

My point was that RR are hopeless at giving real power/torque figures. They are only good for changing things on the day and seeing what diference that made, and even that is dubious due to heat soak issues.

The best use of a RR is to diagnose problems under load, but that doesnt bring the money in or allow you to talk bollox down the pub, hence all these RR shootouts.

I have held this opinion for years and always been flamed for it, but thats the way it is!

Andy.F

What do you think of these G force meters John ? They seem to give an accurate measure of acceleration, just like your SOP meter

R19KET

Paul,

If there's one thing I have learnt, it's that RR figures are a load of tosh, and should be taken with a pinch of salt.

IIRC, the last time Steve M ran at WL, he got 349bhp, then ran at PE, and got 315bhp. I remember geting 284ftlbs/298bhp on one RR, then 3 days later getting something like 377ftlbs/340bhp on another RR !!! I've got the printouts, so it must be true

My current engine has been mapped on an engine bench dyno, so it will be fun seeing what it does on a couple of RR's.

Mark.

Pavlo

A bench dyno should be fairly repeatable, not much to infulence the results unduly.

The problem for car engines is the ancillaries and exhaust induction. Most setups don't allow for the full production exhaust to be in place. Kart engines are easy, 'cause they are so small.

How did you get on with putting the induction/exhuast in place and keeping it all cool? I have seen images of enignes with red hot turbos, and when I was at uni the zetec would run a cherry red manifold on the dyno.

Paul