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What gear to dyno in a 6sd...

 
Old 04-19-2018, 03:14 PM
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Default What gear to dyno in a 6sd...

Hello everyone,
I have a 2000 Miata 6spd and we are supposed to dyno close to a 1.00 gear ratio as possible but all I see are people dyno'ing their cars in 4th. So is it customary to dyno always in 4th?
Also if dyno'd in 4th compared to 5th in my set up what would be the difference?
1st - 3.76:1
2nd - 2.27:1
3rd - 1.65:1
4th - 1.26:1
5th - 1.00:1
6th - 0.84:1
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Old 04-19-2018, 03:36 PM
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The car will make slightly more power on the dyno in 5th, both because of the higher gear ratio and because there's less loss in the transmission (the 1:1 ratio is achieved by directly coupling the input & output shafts together with no gear teeth involved) The 1:1 gear is also strongest (for the same reason) which is another good reason for dynoing a high power Miata in it.

I always use the 1:1 ratio.

--Ian
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Old 04-19-2018, 03:37 PM
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Very little, if any
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Old 04-19-2018, 03:57 PM
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Thanks for the input guys. I will dyno the car in 5th.
It is on May 3rd. I will post the numbers in the Dyno section.

2000 Miata
fm2 kit (old school kit/with the 4 extra injectors ,the Red intercooler piping and running a Link ECU )
gt2554r Turbo
11psi @ 2800rpm -
2.5 exhaust all the back to the muffler. (fm kit with the turbo exhaust muffler with dual tips.
Any guesses on power?
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Old 04-19-2018, 03:59 PM
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180-220
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Old 04-19-2018, 03:59 PM
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Between 180whp and 250whp depending on dyno. 350whp+ if it's a Mustang dyno.
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Old 04-19-2018, 04:05 PM
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I made a max of about 230 with that kit, although I had a 2560 on it and ran 15 psi. 180 if you're running the default conservative timing map, there's 20-30 more if you've got the octane and testicular fortitude to do it.

--Ian
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Old 04-19-2018, 04:15 PM
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5th, always.
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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Old 04-19-2018, 05:33 PM
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So I went back to dig through my dyno charts and my memory was a bit off (hey, it was 10 years ago). My best dyno chart with the old Link kit was 218:



Once you get those kits up to around 240-250 rwhp the stock ECU starts throwing MAF overvoltage codes because it doesn't believe how much air is going through the MAF sensor any more. If the boost spiked badly then I would get those.

I have a 245 rwhp dyno from the same plumbing but replacing the Link with a Hydra.

--Ian
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Old 05-03-2018, 01:18 PM
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Old 05-03-2018, 01:21 PM
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Old 05-03-2018, 01:31 PM
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72 degrees 83% humidity 720 feet elevation .

The boost was fluctuating causing the small dips - now after re-setting the WG Sensor - it is stable .
‘So this is with using the conservative mapping from Flyin Miata . So next on the agenda is to smooth out and hopefully fatten up the power curve by putting some timing back in .

I am installing a wideband A/F in a week - when it comes in . Then back to the dyno.

I have no A/F readings from the Dyno run .
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Old 05-03-2018, 04:11 PM
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Nice numbers, congrats. That drop in torque from 4000-5000rpms is unusual. Maybe an overboost, or needs some fuel/timing adjustments. If you're still on the stock timing map there's most likely some decent power left in it with more timing.
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Old 05-03-2018, 04:44 PM
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Originally Posted by pdexta View Post
Nice numbers, congrats. That drop in torque from 4000-5000rpms is unusual. Maybe an overboost, or needs some fuel/timing adjustments. If you're still on the stock timing map there's most likely some decent power left in it with more timing.
That's probably the boost controller spiking, the algorithm in the Link Piggyback is not very good.

--Ian
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Old 05-03-2018, 11:03 PM
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Torque curve fluctuations of that size are almost entirely caused by unstable boost control, as the OP said
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Originally Posted by codrus View Post
Basically I've come over to the camp of "If something is a reliability problem on the track, just ask Andrew and do what he says".
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