Poor man's dyno

[jonytom]

Picked up on the 'poor man's dyno' (PMD) on Spyderchat this week. Thought I'd give it a try.

For anyone not familiar with this see  m http://www.spyderchat.com/phpBB/viewtopic.php?t=10167 m . Basically you start off on a flat/straight piece of road at 2000rpm in third gear. You then floor the accelerator and start timing at 3000rpm. Keeping in third you stop the watch at 6500rpm.

You do this a few times to even out any stop watch anomolies.

I realise the idea here is to compare against your own times - before/after modifications, but I'm a little confused by other results.

I managed 10.9 seconds - car is stock '03 apart from Markiii inlet duct and TTE lowering springs. Conditions were good, around 12 degrees C, I had an almost full tank and I'm about 14.5 stone (I'm tall!).

On Spyderchat it looks like average stock times are around 8.5 seconds - looks like I'm v slow! Gear ratios maybe?

There again, a search here showed Rusty getting 12 seconds with an '03 fitted with inlet duct and H&S twin exhaust. Conditions on his run looked very similar, and he's lighter than me!

See -  m http://www.mr2roc.org/phpBB2/viewtopic.php?t=4062 m

Any idea why these times should vary quite so much? Am I reading this all wrong? Anyone else got comparative results?

Incidently, as this test takes you over the national speed limit, it should only ever be conducted on private ground, with the permission of the owner!
     s:wink: :wink: s:wink:

[Tem]

On Spyderchat it looks like average stock times are around 8.5 seconds - looks like I'm v slow! Gear ratios maybe?

US Spyders have faster gearing than EU Roadsters, you can't really compare them.

[spit]

Yep, the US/JSpec MR-S 5-speed has a 3rd gear ratio of 1.392 compared to 1.310 in the Euro, and final drive 4.312 vs the Euro's 3.941.

There again, a search here showed Rusty getting 12 seconds with an '03 fitted with inlet duct and H&S twin exhaust. Conditions on his run looked very similar, and he's lighter than me!

I'm wondering if Russ has done the bum dyno again since chipping and ECU reset?

[Anonymous]

My best time was 11.9 with the H&S air pipe and H&S twin - basically 1s slower than your time. I'm just wondering if that could be accounted for by having the roof down for all the tests. Might worth dropping your down for a run to see what difference it makes.

Spit - good point, I've not round to doing a PMD with the Unichip yet - I'll post the results when I do.

[Anonymous]

The 2 was feeling quite eager so I went for a quick PMD run. Averaging my times gave me 11s dead. My absolute best run was 10.66s. The stretch of road that I've been using has a slight upwards gradient but nothing major. These results were performed with half a tank of fuel and the roof up. For anyone looking back at the old post at my previous results, please note that since then, I've fitted a Unichip and also gutted my precats.

Really I should find another stretch of road where i can perform equal numbers of runs in both directions and then average the results to negate any gradient effects but I can't think of anywhere at the mo. In any case Jonytom your results are pretty good considering that I've got a few more mods than you  s:) s:)

[jonytom]

Main reason I tried the PMD was because fitting Markiii's pipe seemed to have made a big difference. Trouble is I didn't pick up in the PMD thing until after I'd fitted the pipe - so no previous runs to compare with.

Only thought is that my rear tyres (stock Yoko's) are right down to the bone. Getting v scary in the wet but grip is better than it's ever been when dry.

Maybe I'm getting a bit extra push from these? Or it could just be the pipe. Or I'm just hopeless with the stop watch!!!

Anyway, going to keep doing this as I add more to the car.

[Anonymous]

This should satisfy your curiosity:

http://www.mr2roc.org/phpBB2/viewtopic.php?t=4062&highlight=pmd