Power logs 2nd gear vs 3rd vs 4th

[EspenW]

Did some new power and torque measurements with the MR Dyno. For the first time, I also included a 4th gear pull, but limited it to 5300rpm because that was approaching twice the speed limit. Still, that pull produced the highest whp number, even though 5300rpm is well below the rpm of peak power.
Slightly above 2bar peak boost on Turbonetics E50 turbo with E85 fuel in the tank:

Numbers uncorrected for 12 deg C ambient:

408ps og 562nm at the wheels in 4th gear (limited to 5300rpm)
406ps og 530nm in 3rd
401ps og 510nm in 2nd

The graphs show that 3rd and 4th gear pulls will produce pretty similar results, even though 4th gear numbers are still higher. I guess 4th gear would have produced approx 415-420hp at the wheels if the run had been taken to redline.
In 2nd gear the torque curve suffers greatly, because the turbo spools approx 1000rpm later.

A new Porsche Cayman S that wanted to strut its stuff got beaten. With a sound margin.. nice engine tone in that Porsche, though.

Interestingly, peak G-force in 4th gear was 0.45G. That is 10% more G-Force than I recorded peak in 2nd gear on a 350hp 4.2L S6+, just in case someone had forgotten why we like turbos

Graph 1 shows torque at the wheels in 2nd vs 3rd vs 4th gear
Graph 2 shows power at the wheels in 2nd vs 3rd vs 4th gear

[Bram]

Always dyno the S2 in 4th gear. This gives always the best result, however not every rolling road likes these high speeds. I ended up with 10 extra HP running in 4th gear vs. 3th gear. Also spoolup is better.

[Rusty]

Don't forget that inertia of the drive train is effectively higher in lower gears due to higher acceleration rates, this will make a small difference, consistent with the numbers you have. Also, drag effects are not strictly linear so there will be further discrepancies there. These in car dynos like GTech etc. are basically limited by the available road and speed limits, better to get raw data from a second gear run and use that for comparison so that there is no unknown maths in the background, you won't get pub numbers but the data will be easy to compare.

[mcandmar]

Your supposed to use whatever gear is closest to a 1:1 ratio, i.e. 4th in a 6speed S2.

[Rusty]

If you want to do 4th gear runs on a public road then you're 130mph is not a good idea unless you're on a clear motorway and even then it's not quite what PC Plod would see as sensible

On the road, for power runs anyway, you're better off in 2nd or 3rd if it's a straight stretch. For torque runs then you can use 4th or 5th as torque will be lower down the revs.

[mcandmar]

Oh right, i was thinking dyno runs not g-tech

2nd gear sounds sensible since you have to account for aerodynamic drag, i would guess that would be rather substancial with a 4th gear run

[avants2turbo]

how accurate are the G-tech meters?

[Rusty]

Things like GTechs make allowances for aero I think.

No power dyno is gospel really but if you know what it was before then you can wuantify after.

I use a 5Hz GPS receiver, my phone and racechrono software, total cost £45 for the QStarz BT 818. You can then do all the calculations yourself and use the VBox software to measure any performance metric you want, a bit more effort but put the remaining £200 towards beer, pies or tuning

[GazzaG60]

anybody recommend how to get good results from my G-tech. not used it yet.

[A80Avant]

espenw are those numbers that the Mr dyno produces or that you made through accel.results on an excel sheet?

What input does Mr dyno uses to produce results @ wheels? does it compensate for losses or is this a clean number?

[EspenW]

how accurate are the G-tech meters?

Car & Driver did a big test a while back:
http://www.caranddriver.com/reviews/...s_work_feature

Used correctly, G-Tech and the like will be very accurate and will report acceleration figures that are spot on with the track. Horsepower measurements are a matter of programming the correct vehicle weight. This is where most errors are generated by people using listed weight or purely guessing the weight of their car.

I use a MR Dyno meter that was designed by the company that makes the Mustang Rolling Roads, and they are supposed to produce overlapping numbers (the Mustang loads the car similarly to the load that it will see on the road).

Here are some other results that I have gotten from various cars:

S6 with 034 GT3071R setup, 3" exhaust and Evo manifold: 355whp
Stock RS2: 253whp
Remapped RS2: 283whp
Tuned S6+ (326hp stock): 254whp
80 Avant 2.0E (115hp): 88whp
Mini Cooper S: 135whp
Scirocco 1.4TSi 131whp
Chipped 1.8T Quattro: 159whp
Chipped and tuned Golf VR6: 155whp

[Rusty]

Turn off roll-out for a start, not required for anything other than 1.4 mile times with a timing beam. Make sure it's securely mounted, correctly calibrated and that you give the car a firm launch to make sure it's got the message.

[EspenW]

espenw are those numbers that the Mr dyno produces or that you made through accel.results on an excel sheet?

What input does Mr dyno uses to produce results @ wheels? does it compensate for losses or is this a clean number?

These are numbers from the MR Dyno. It compensates for aero losses (I program aero force at three different speeds, and it generates a loss curve).
I have not programmed in rolling losses (approx 12hp at 95mph), as I want the numbers to be comparable to whp numbers off a Mustang (or other loading) dyno.

[A80Avant]

that is very good,at least you are getting repeatability!!!

are you sure you cant go any higher with advance with E85?
how many degs are you now from 3800 to 7000rpm and what is your boost?

[EspenW]

that is very good,at least you are getting repeatability!!!

are you sure you cant go any higher with advance with E85?
how many degs are you now from 3800 to 7000rpm and what is your boost?

The repeatability is fantastic. I can produce perfectly overlaying graphs on back to back runs, especially on NA engines (turbo engines and especially ones with WGFV) will have boost pressure that fluctuate some between runs.
Peak boost is 2bar, and comes in right after 4K.
Timing:
3960rpm: 17.3
4280: 16.5
4600: 15
4920: 15.8
5160: 16.5
5480: 17.3
5840: 18
6200 and to redline: 20.3

There is definitely gains to be had from timing, but I'm running 2bar instead of 1.7bar, and that means it requires less timing that what is the case at 1.7bar.