DYNO RUN RESULTS!

G1 · Post by G1 » Mon Apr 19, 2004 12:29 pm

sorry to add confusion guys, but UAS may be confused themselves.

looking at one of the dyno graph for a tip gpx, only 120kph was reached, which would indicate that the test was done in 2nd. no?

i think manuals may have been done in 3rd as well, especially since if you look at silentbob's he didn't even reach 180, which probably means rev limiter was reached before the speed limiter

so in 3rd gear manual, do we hit the rev limiter first or the speed limiter? if latter is the case, what rpm did we reach (theoretically)?

ruchi · Post by **ruchi** » Mon Apr 19, 2004 12:59 pm

A manual FTO does just under 160kmh in 3rd, given that the graphs go well beyond this speed there are three posibilities:
1) The tests were done in 4th for manuals
2) Substantially larger tyres have been put on the cars
3) The dyno has a large percentage error

Given that UAS said the test was done in 4th for a manual, this would appear to be accurate based on the dyno graph, as the top speed is faster than what is possible in 3rd and the graph cuts out before we see the dip in power that occurs once you pass the peak power output of the engine, which means the speed limiter kicked in first, which is what would also happen if the car was in 4th gear.

For a manual, in 3rd the car would rev all the way to 8,200rpm and hit 158kmh, in 4th the speed limiter would kick in at 180kmh when the revs are around 7,000rpm. The later seems more consistant with the graphs posted so far.

salacious · Post by **salacious** » Mon Apr 19, 2004 1:01 pm

G1 wrote:sorry to add confusion guys, but UAS may be confused themselves.

looking at one of the dyno graph for a tip gpx, only 120kph was reached, which would indicate that the test was done in 2nd. no?

i think manuals may have been done in 3rd as well, especially since if you look at silentbob's he didn't even reach 180, which probably means rev limiter was reached before the speed limiter

so in 3rd gear manual, do we hit the rev limiter first or the speed limiter? if latter is the case, what rpm did we reach (theoretically)?

120kph is approx what the rev limiter is on a 4 spd tiptronic in 2nd (I worked it out to be nearer 130)
3rd should be about 175kph.

In a manual or a 5spd tiptronic you'll hit the rev limiter in 3rd but you'll hit the speed limiter in 4th and 5th.

Brian

G1 · Post by G1 » Mon Apr 19, 2004 1:10 pm

so looks like tips were done in 2nd, and manuals done in 4th

i wonder why silentbob's didnt reach the speed limiter in 4th, either it was done in 3rd, or his gear ratio is different, or his wasn't redlined.

so does anyone know if safc-ii delimits the speed? in which case we should look at TJ2709's graph

ruchi · Post by **ruchi** » Mon Apr 19, 2004 1:41 pm

Based on the rev limiter kicking in at 8,200rpm, here's the figures for a 4 speed tip
1st - 71 kmh
2nd - 133 kmh
3rd - 203 in theory, but due to speed limiter 180 kmh @ approx 7,250rpm

G1 · Post by G1 » Mon Apr 19, 2004 1:58 pm

ok i think i found what *might* confirm that we did not reach our maximum peak (for manuals only with speed limiter)

this stolen from mivec.co.uk, shows that after a flat spot there is another peak...

and if you convert his bhp @ wheel which look like roughly 155, this is roughly 115kw

so mikey, how was your peak power reached? is yours de-limited?

and our torque curve should also keep dipping down, but it doesnt get that far on ours

GPXXX · Post by **GPXXX** » Mon Apr 19, 2004 2:34 pm

Mine was done in 3rd gear, but it is not speed-delimited... (my AFC is way too old to be THAT clever LoL)

...does that mean i could have had more if i removed the speed-limiter?

G1 · Post by G1 » Mon Apr 19, 2004 2:39 pm

no, coz yours was done in 3rd, and didnt hit the speed limiter

i bet you felt pretty good about your results until now (j/k)... actually a std manual gpx should be getting under 100kw, so youre still ahead mikey... and i heard that 4th gear is the std gear to do dyno tests since its closest to 1:1, but too bad our cars have the speed limited...

so in theory, i should be getting about 110+kw @ wheels, so should be able to get sub 15s 1/4 mile times... what do you guys reckon?

richardH what mods are on your car? and have you done a 1/4 mile time?

GPXXX · Post by **GPXXX** » Mon Apr 19, 2004 3:01 pm

frankly i couldn't care less about my results, coz at the end of the day it all depends on how well you can put every single bit of that HP onto the ground so trust me, whether if i have 5 kw at the wheels more or less than anyone - the bullshit stops when the throttle drops...

like i said before, the graph is there as an indication for tuning purposes only and again, as mentioned many times before by others (which i cbf'd going into greater detail) every dyno is different so you're really comparing apples to oranges...

i will try to get it dyno'd again before and after the turbo is fitted to see what sort of differences it made...

ruchi · Post by **ruchi** » Mon Apr 19, 2004 3:04 pm

That graph also doesn't go all the way to the rev limiter. If it did you'd see the power curve continue to drop.

G1 wrote:i heard that 4th gear is the std gear to do dyno tests since its closest to 1:1

I assume you're refering to gear ratios, and if so, why does this matter, as regardless of whether the gear ratio is 1:1 the final drive ratio will be different depending upon transmission (A/M) or make of car. What am I missing here?

G1 · Post by G1 » Mon Apr 19, 2004 3:17 pm

fair call, i was just having a go at ya

like i said i wouldnt seriously compare to anyone who didnt come to dyno day... it was interesting to see the huge difference between tip and manual... i wish more gpx manuals turned up though...

im just eager to get sub 15s 1/4 mile time, and i think my odds are getting better, though i dont wanna try until im pretty sure i'll get it...

G1 · Post by G1 » Mon Apr 19, 2004 3:38 pm

ruchi wrote:That graph also doesn't go all the way to the rev limiter. If it did you'd see the power curve continue to drop.

G1 wrote:i heard that 4th gear is the std gear to do dyno tests since its closest to 1:1
I assume you're refering to gear ratios, and if so, why does this matter, as regardless of whether the gear ratio is 1:1 the final drive ratio will be different depending upon transmission (A/M) or make of car. What am I missing here?

yeah it looks like it didnt, but peak power should have still been reached at least...

as for the gear ratios, im not entirely sure myself because im not technical enough, but i have heard from more than one source, that dyno readings in 3rd and 4th give different readings, one has advantage over the other, i think 4th give higher readings... so mikey, maybe in 4th you could have made more now that i think about it... unless i got it the wrong way around

anyway ive spoken to UAS, and i asked them to describe the one with the safc-ii, and it kept going over 180 onto 190, and was continually making power. they are willing to let me go on and test 3rd gear so that should be interesting.

GPXXX · Post by **GPXXX** » Mon Apr 19, 2004 4:12 pm

G1 wrote:fair call, i was just having a go at ya

im just eager to get sub 15s 1/4 mile time, and i think my odds are getting better, though i dont wanna try until im pretty sure i'll get it...

i knew you were, but i'm not gonna play... LoL..

seriously Jiwan, i really think you should be able to get sub 15s on your manual GPX easily as is in its current trim... why not just head over to Eastern Creek / WSID or something and have a go and get some numbers?

GPXXX · Post by **GPXXX** » Mon Apr 19, 2004 4:26 pm

G1 wrote: as for the gear ratios, im not entirely sure myself because im not technical enough, but i have heard from more than one source, that dyno readings in 3rd and 4th give different readings, one has advantage over the other, i think 4th give higher readings... so mikey, maybe in 4th you could have made more now that i think about it... unless i got it the wrong way around

hmmm, perhaps it's something to do with the gear ratios...??

then again i failed physics back in VCE so done hold me against this theory LoL...

G1 · Post by G1 » Mon Apr 19, 2004 4:49 pm

yeah like i mentioned, 4th is closest to 1:1 ratio, so they choose that normally

ruchi · Post by **ruchi** » Mon Apr 19, 2004 5:02 pm

I don't believe it is gear ratios as the output will be the same regardless of what gear you have it in, and as I said in reply to G1's comment of a 1:1 gear ratio in 4th (Manual) and 3rd (Automatic), this discounts the final drive ratio, so it doesn't appear to be that.

I'm more than willing to admit that I could be wrong, and that a 1:1 ratio could be the reason, but if so what am I missing, and likewise what about the final drive, and what about the fact that very few cars actually have an exact 1:1 ratio?

The only reason I could see for this 1:1 ratio would be because of inertia, but no one has rasied that.

Doing a quick search on the net, the only valid reason I could find is wheel slippage. If you were to do the test in 1st or 2nd, there is a higher chance of the wheels slipping against the rollers than there would be in 3rd or 4th, as the rate of acceleration is faster. If the wheels slip then the dyno reading will be wrong.

So why not use top gear, the only valid reason I can find is that in top gear the speed at the highest RPM range is often beyond that recommended by the dyno manufacturers.

So it would appear they pick a high enough gear to minimise wheel spin, but a low enough gear that their dyno doesn't fry it's bearings

Perhaps G1 you can ask UAS when you go back and see if they can actually explain the reason behind it.

Anyone else able to shed any light on this?

GPXXX · Post by **GPXXX** » Mon Apr 19, 2004 5:05 pm

c'mon peeps i wanna see more dyno charts dammit...

G1 · Post by G1 » Mon Apr 19, 2004 5:20 pm

yeah even the dudes and dudettes from overseas

ruchi · Post by **ruchi** » Mon Apr 19, 2004 6:28 pm

OK, it would appear that the 4th (manual) / 3rd (automatic) gear setting for a dyno is based around inertia. Change the gear and you'll alter the inertia (the ability of the engine to change the motion of the running gear / wheels / dyno).

I was surprised to learn that most dyno's don't actually measure hp, rather they calculate it. So although your engine is actually producing the same amount of HP, the dyno will give you different results depending upon the turning power of the gear you are in.

In practicle terms this means that this introduces yet another inaccuracy into the equation and provides yet another reason not to take dyno figures as gospel.

Based on this, you'll get a more accurate reading on a tip FTO as 3rd gear has an exact 1:1 ratio, and the manual will have calculation errors (as will most cars) because it does not have an exact 1:1 ratio.

After reading what I did today, I now have only one word to describe someone who brags about their dyno results: wanker!

(this is a general comment, it is not aimed at anyone on this forum

).

Interestingly enough, the home dyno kit which a number of people on this forum have mentioned doesn't suffer from this problem as it accounts for all the various gear ratios as part of its calculations.

RichardH · Post by **RichardH** » Mon Apr 19, 2004 6:31 pm

GPXXX wrote:c'mon peeps i wanna see more dyno charts dammit...

Okay, here's one...

<img src="http://www.ftowa.com/images/workshopart04_7.png" border="0" />

This was one done on Home Dyno from crank angle sensor. Second gear run. It was performed the same day as a real world dyno run, then I tweaked the various settings to calibrate it... so it matched the real graph as closely as possible.

Real world dyno gave 161.4 bhp atw (at 7700rpm). I've got the sheet at home, but never bothered to scan it. I can if ya want.

- Rich

PS. Note that the actual values on the torque curve don't mean anything. This is an 'at-the-wheels', whereas we'd want to talk about flywheel torque. But the curve is the same shape regardless, so useful to look at.