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Interesting Rolling Road results !


mattcony
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On Saturday afternoon I went to Awesome GTI in Manchester for a Uk-Mkiv’s Rolling road day, I had originally forgotten about this even but then I spotted it on the forum at lunch time so jumped in the car and headed down to see what was happening.

Plenty of cars had turned up, GolfGirls car was there as well and had been on the rollers earlier, I got chatting to one of the guys operating the road and asked if they had any slots left to which he replied “a couple” so I whipped out the plastic and joined the Q, they have just installed a new DynoJet 4x4 rollers so the figures should be pretty good.

Most of my mods are handling really, power wise I just have the 6463 remap and a Milltek straight through system and she managed 208bhp @ the wheels

constante1.jpg

constante.jpg

From whats on the Awesome site GolfGirl is Running AMD stage 2, Milltek straight through system & a K & N short ram air intake

bowden1.jpg

bowden.jpg

All the other peoples figures / Pictures and soon to be videos are posted on Awesoms site http://www.awesome-gti.co.uk/rollingroad/rr.ukmkiv_14.01.06.html

Cheers

Matt

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Once a car has run past it's peak power and torque, there's no point in keeping increasing the revs, so you're probably seeing the result of the driver taking his/her foot off the throttle when the car gets to 6800 rpm, rather than the rev limiter kicking in. IIRC, the max rpm my car did both times it's been on the AmD dyno is 6800 or 6900 rpm.

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[ QUOTE ]

Once a car has run past it's peak power and torque, there's no point in keeping increasing the revs, so you're probably seeing the result of the driver taking his/her foot off the throttle when the car gets to 6800 rpm, rather than the rev limiter kicking in. IIRC, the max rpm my car did both times it's been on the AmD dyno is 6800 or 6900 rpm.

[/ QUOTE ]

Fair point. When I was at Awesome between Christmas and New Year for the open RR sessions, Jim didn't seem to back off in any of the cars - except for the RS6 auto which refused to hold a gear to the limiter. So from that I assumed that they ran everything to the limit. confused.gifsmashfreakB.gif169144-ok.gif

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[ QUOTE ]

Once a car has run past it's peak power and torque, there's no point in keeping increasing the revs, so you're probably seeing the result of the driver taking his/her foot off the throttle when the car gets to 6800 rpm, rather than the rev limiter kicking in. IIRC, the max rpm my car did both times it's been on the AmD dyno is 6800 or 6900 rpm.

[/ QUOTE ]

This is exactly right Mook.

I`ve been to Awesome today to have my GTI mapped, and I watched Jim do this on the RR. He then explained to me that he just powers-off once the engine has hit peak power, as it`s pointless going any further, which, as you say, explains the sharp drop-off. 169144-ok.gif

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Nice to see some actual at the wheels results. I get tired

of seeing random guesses at the crank horsepower and no

mention of wheel horsepower at all.

Now check this out. Bunch of R32's in all states of tune

running on the exact same model dyno (rolling road).

http://forums.vwvortex.com/zerothread?id=2394800

Have dyno results for:

Stock, Chipped, flapper mod, exhaust, cams (and various combinations

of these) plus HPA FT360 turbo, HPA FT400,

HPA TT Stage 2, EIP Stage I low and high boost, EIP Stage IV,

VF-eng Stage I, VF-eng Stage II. 17-18 cars all told.

All numbers results are *at the wheels*.

VW told HPA that the drivetrain loss during all wheel drive operation

is about 23%. So take any of these at the wheels numbers and

divide by 0.77 to get a rough estimate of crank hp.

E.g. Stock.. 202awhp / 0.77 = 262bhp.

Or. EIP Stage IV.. 580awhp / 0.77 = 750bhp. wink.gif

ian

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BTW, it's not pointless at all to run it to redline on the dyno.

It's useful to know what your torque curve looks like beyond the power

peak. When you're racing you want to bracket your shifts around the

peak power, not shift right *at* peak power. While racing you

spend 90% of your time between 5000 rpms and redline. Even with

a falling torque curve you usually produce more accelleration in

a low gear at high rpms (beyond power peak) than you do in a higher

gear with lower rpms and higher engine torque. This is because

the tranny is a torque multiplier and torque to the ground is

roughly engine torque x tranny gear ratio x final drive ratio.

ian

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Welcome back Ian 169144-ok.gif

I disagree re the 23% loss (I think it's more), but will need to dig out the dyno tests I had done on the calibrated dyno at AmD in the UK.

Interestingly on your race-track comment, in the R32, I stick between 4,000 and 6,000 rpm all the time - the close ratio 'box on the R32 lets you do this consistently. I've tried loads of different styles, all on the same track (Donington) and this is the quickest way for me to get round the track with the setup on my car - not necessarily for anyone else, though!

beerchug.gif

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Wow what a great post on Vortex to be able to look at the same set of rollers running the same model of car, from what I can see on average you can see what wheel BHP gains variouse bits have on the R, I would say roughly

Wheel BHP gains seem to be,

2-3bhp for an induction kit,

10bhp for a remap / chip

22bhp for cams

Lots for Turbo's 169144-ok.gif

Was EIP's big beast really 582bhp @ the wheels EEK2.GIFEEK2.GIFEEK2.GIF

Cheers

Matt

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Ya, the EIP Stage IV proof of concept car will spin the tires

through the first 4 gears or so.

Drivetrain loss varies *highly* depending on dyno. The 4 wheel

Dynojets (which just have 2 massive rollers of fixed/known size

and no additional braking) generally show the lowest loss (as

low as the stated 23%) and ones like the MAHA dyno show the highest

(sometimes in excess of 35%). AmD's has a MAHA dyno. The MAHA dyno,

in my opinion, is inherently flawed because it attempts to measure

drivetrain loss during coast-down while Haldex is disengaged

which can't possibly be the same as while it's under

load (with Haldex engaged). Regardless of whether it's erroring on

the high or low side, there's simply no possible way that

the drivetrain loss is the same during both engaged and disengaged

times (if it was, then the whole concept of Haldex would be

pointless). Looking at back to back runs on the same car on a MAHA

dyno, you can see the "measured" drivetrain loss vary by up to 10hp,

and runs with different R32s or the same on different

days, the difference can be even higher, which leads to wildly

varying BHP numbers. I think in the end the MAHA ends up with

reasonably close BHP numbers by special "calibration", more than

solid repeatable measurement. By comparison, there are runs on the Dynojet

where there's no more than a 1-2hp variation between 3-4 runs,

provided the car is supplied with sufficient cooling. And because

the Dynojet requires no additional calibration (the mass of the drums

never changes), it's pretty useful for comparing the power of

cars in different locations (such as the Dynojet pulls at

the top of this thread, compared to those in the Vortex thread).

BTW, if you still want to believe that the drivetrain loss is higher

than the stated 23% then adjust all crank hp numbers *up* accordingly. wink.gif

E.g. 202whp for stock R32 / 0.70 (assuming 30% drivetrain loss) = 288hp.

Hmm. Probably not. wink.gif

ian

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And to keep this in a semi separate discussion..

If you're shifting at 6000 rpms, you're throwing away power, in

at least the first 3 gears. Yes the torque curve is falling

(it's falling all the way from 3500 rpms onward), but multiply

the engine torque by the total gear ratio and you're still

putting more torque to the ground at 6500 rpms in say.. 3rd gear

than you are at say 5700 rpms in 4th gear at the same road speed.

Torque to the ground = instantaneous accelleration.

Horsepower is just a measure of how high into the rpms you can

continue to make useable torque. If you're shifting before

the power peak, you're doing *less* total work, thus going slower

than you could be.

I'll do a shiftpoint analysis using VAG-COM one of these days

but I know that what what it'll show is that for 1st, 2nd and 3rd

gears you should shift at the rev limiter, and by the time you get

to 4th, *maybe* you short shift by a couple hundred rpms, and a bit

lower still for 5th.

BTW, the reason we *feel* like we should short shift, is because

our bodies are more sensitive to changing rates of accelleration

not to absolute accelleration itself. So if the positive rate of

accelleration is decreasing (follows the shape of the torque curve)

we actually feel as though we're slowing down. It's not true.

The butt dyno is wrong.

ian

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