Guys, I'm confused.

I've been looking over the past 2 Rolling road results and have come up with a few questions.

How come 2 almost identical cars (in terms of transmission) can have such a different power correction applied to the PAW figure.

Pete had 173 PAW corrected to 304 (+131)
The P1 had 191 PAW corrected to 293.5 (+102.5)

both cars had an air temp of 41 deg C ???

Secondly

Sams EVO7 had 237 PAW corrected to 371 (+134)
November - EVO5 had 242 PAW corrected to 333.5 (+91.5)

How come such a large variation in correction ?

I noticed that the air temp on Sams EVO7 was up at 56 deg C !
Surely that gives a false correction as the FM intercooler is going to be running a lot cooler than that.

Is it the case that,on the rolling road, FMIC cars have a double hike in claimed flywheel hp, firstly from the blast fan cooling the charge and secondly from the hot air exiting the FMIC heating up the dyno temperature monitor for an even greater correction factor ?

It would also appear that the November and January days were very similar conditions as Hamish's Skyline had exactly the same figures both days ( 0.5 hp difference !)

I have also noticed a few differances in charts that I'm a bit wary off. My Vectra was first up at Star in September where it recorded 185.5bhp & 206lb-ft, the car was standard with 1000miles on the clock and as standard should have 170bhp, the air temp showed as 51degrees and transmission loss off 42bhp, but when it was back up on the 20th is recorded 168bhp and 190lb-ft with tranmission loss of 48.5bhp, the only changes were a Magnex cat-back exhaust and a change from 16"-17" wheels which have a very slightly lower rolling radius. The air temp was 23degrees. It seems a massive loss (17.5bhp & 16lb-ft) thorugh so little change when the graphs themeselves are fairly similar both graphs are here: http://www.vpccscotland.co.uk/davespics.htm.

Will be back at Star this sunday so gonna have a word with jim and see if he has any ideas as to why there is such big differance, the 1st chart seems a long way.

Davey, changing from 16" to 17" where the overall diameter is even slightly changed will make a diff. to the flywheel power, also if you went for slightly wider rubber this could cause the calculations to be way out. The rollers measure torque at the wheels on the known rolling mass of the rollers. The rest of the figures is calculated out by the machine where the results can be off due to oil drag in the gearbox /axle, as well as underinflated tyres which give a larger deformed contact area with the rollers (on the rollers the wheel has two contact patches, where on the road it only has one, so this in itself give larger losses)

The only real way you could have seen a 'true' change with you add-ons is if you accurately recreated the conditions of you first run, intake temp, engine temp, egt, tyre pressures blah, blah...blah.

You will see varying results in diff. cars due to their transmission set ups. Even though the car looks stable in the rollers, my Evo was transferring power to get grip as it spun up, as most 4*4's do, again more losses that cannot be calculated.

Hope this makes sense or I could be talking total Keeche ;)

The Rollers are only a good guide as to how your car is running and it would take ages to set it up for a totally accurate run.

Anyone add to this? Sam!!??

...John

Yeah thought the different wheels would make a differance but not as big a differance we will be back this sunday for another run now the superchip upgrade has been done and it will be running with the 17" again so will be able to see an accurate comparison between the last one and this one, we're back again at the end of March where I'm planning to run on the 16" so that should give a good indication as to what the actual differance is.
I'm not overly concerned with the readouts as you say its only really a guide, its more the shape of the grpahs I'm really interested in it was just weird looking at the 2 graphs, Ill have a chat to Jim at some point as well see what he thinks. :)

hi cosie
i think you have figured out the rolling road game. cars with front mounts win period. because the rollers put so much load on the car and therefor the inlet temps will go up much higher than on the road. so while the AIT in your car may reach even more than the 50 degrees ( actaully alot more as you probably now ) on the road at least all subarus will be reaching the same temps on the rollers ie 51-52 i think that what most cars ran. but because the itercooler will probably get more air on the the road than the rollers the they both should be cancelling them selves out. that is why the rollers is pretty accurate for standard subarus.

however if you have a FMIC you tend to get an advantage.

the evos are different. first they have a front mounted intercooler, also they have a lot of electronic diffs, basically all these diffs are going to add to the transmission loses. the 6 has got rear AYC and a front LSD and the obvious centre. the 7 has got in addition to that an active centre diff. so they will always have more trasmission loses than the scoobs. so always more power on the rollers :). also my evo 7 has got automatic intercooler waterspray which was on that also will help.

you should try to compare power at the wheel but even this will vary from a car to car. the more you rev the car the more power at the wheel you may get but this theoratically will heat up the transmission fluids more and you should end up with probably less trans loss :confused: so they should cancel each other out but most of the time they don't !!!!!

things mentioned like wheel size, tyre pressure the number of poeple in the car all make a difference.


and as for pete's car the again ? same power at the wheels but huge transmission loses on the same car, i think he had a different fly wheel though?

my head hurts. basically the best thing is to compare power at the wheel on your car between mods, forget other people results.
and if you want to see how fast your car is take to track or the strip.

and if you want to get big bhp to impress the boys get an EVO OR a skyline and stop your moaning:D ;)


sam

[Edited by Sam Elassar - 1/31/2002 1:28:22 AM]

Not moaning Sam :D just trying to get my head round the inconsistent results :rolleyes:

After all, if I only wanted the power to blow away an EVO I would have just kept my Cossie :p:

It's something called 'character' that attracts me to the scooby :)
I just don't feel drawn to an EVO or Skyline in the same way.

I agree it's road/track performance that really matters. Looking forward to meeting you at Knockhill ;)

cc

[Edited by Cosie Convert - 1/31/2002 11:14:46 AM]

I am sure you would leave us all if you just drove a std Scooby round Knockhill from what I hear of your racing successes.

cossie
i know you are a much better driver than me but you just can't beat BHP :) roll on the next knockhill ;) :)

You just can't beat BHP ? That's not what you said to Keith with the 480 BHP Skyline ;)

I'd better start writing a new 'excuse book' for first Knockhill meet ;)

hi CC

i was just winding keith up, i came across couple of over 450bhp skylines in the bast but i have to admit that keiths car is one of the few cars that i have seen that is modified to a very high standard. it all goes back to few months back when i was speaking to the skyline boys and they were saying that my next upgrade to my scooby should be to get a skyline and that was with a 320bhp scooby what a cheek ;)!!! so that is why all the banter. but it is very harmless and friendly really.

as for your good self, even if you second name is shumachar i don't see how you can make up for 70bhp at the wheel at least( i am guessing here what did you get? ). you maybe able to corner quicker but i can break better and travel faster in a straight line?.

if you do, obviously i don't have enough straight line advantage and it should be time to mod the car further :D this strategy always worked for me :).

i think your best chance though is to catch me early on in the day before i start getting used to the car.

sam

[Edited by Sam Elassar - 1/31/2002 5:14:58 PM]

This will be fun! CC didn't run at Star that day, but is running about the same boost as you on a TD05 and holding it all the way in a lighter car. It did pull rather well I thought - understatement. Now his driving ability against your good brakes and intercooler and better handling..... WILL be fun!

[Edited by john banks - 1/31/2002 5:13:52 PM]

Sam,

how many flashes will CC have to give you before you let him past :rolleyes: :p ,he may not have the power to pass you on the straights,but will you let him past and keep up with him in the bends?

judging by the tone of your keyboards ( u and john) i may just take a sicky for the next track day :)

quote "but it is very harmless and friendly really" :p

but it is :p are you and john CC little helpers now :p :p is that all because i don't have my scooby in more, i just don't fit in the mob :D

No m8. But he did happen to have rather a lot of success at Knockhill.... don't say we didn't warn you. I am not a track monkey, but I know that folk with racing experience tend to kick ass. One of the instructors at Knockhill drove me round in that 1.8 Westfield and it was flying past EVERYTHING on track. Now I know it feels quick and is quite quick, but he was really making "good progress".

Sam m8 you are a better driver than I will ever be, and I look forward to passengering in the 7 with you!

[Edited by john banks - 1/31/2002 5:50:51 PM]

a 1.8 westie at knockhill in the fry is a leathal weapon, they are so quick that we can't actually compete with. ask T-UK there is one that used to come to most of the hot marques days and it was by far the quickest car there until it starts to rain, and then he just used to spin at the hair pin all the time.

CC limiting factor will be his understeer, unless the car has got an upgraded suspension.

Being an RA it has the alloy bottom arms which improve the castor. Shox n Springs ? god knows but it's pretty firm, perhaps too firm ?
22 mm rear ARB and 2Deg front camber should help sort out the understeer :)

Crap brakes :eek: but I can always use Sam for that ;)

Oh, did I mention that I used to race Stock Cars ?!!

[Edited by Cosie Convert - 1/31/2002 6:06:12 PM]

definitly taking a sicky :D, it will be fun regardless. and that joke about using me as your brakes is not even funny :eek: what will it tell the wife!!!
:)

sam

:D said it would be fun.

The psychological race is fun anyway !!

LOL @ CC's new brakes :D

Sam,

one of the most impressive cars I ever remember round K/hill,other then jf's plastic pig ;) ,was that BMW Z2 M3 and it was p1ssing down at the time :eek:

now now, 3 on one is not fair, i need some back up here. i kept up with JFs car for few laps it was snowing at the time :) and i have over taken the M3 thing ok it kept up after that for a lot of laps but was never faster although it had a power and probably weight advantage.

I kept up with an M3 in a 406 the other day :p I felt very clever ;)

M3 are pretty heavy.

[Edited by john banks - 1/31/2002 6:23:00 PM]

Not quite true Sam

I know of a 250BHP Calibra Turbo that lapped Goodwood consistently FASTER than a 450BHP Cosworth.

..... wasn't me that came up with that quote (or a quote along them lines), cant mind the fella's name now :rolleyes:

I need MAJOR tuition. I have put far too much effort into only mildy modding my car compared with learning to drive. The car way outstrips my capabilities - just letting John Harley drive it made me realise that, along with the way even hot hatches give me bother in the wet even!

great the now i have got a whole team of people against me. :)

sam

john,

this was a Z3 roadster thing.

Sam,

be honest,the track was flooded in places,what would have happened if it was dry ;) ,not slagging you off,but the car was a surprise considering the conditions,at the time.