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Thanks guys. And sorry for all the confusion. I think I am still confused myself.

Emre, I tried your suggestion and you're right. I did a running test at approx 65kph and I got a reading of 5.5 sec which is mathematically correct. However, doing a standing start test gave consistent 100 kph+ terminal speed in conjunction with the time logged.

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Not much to be confused about here Toby,

You are simply measuring the distance covered which in this case 0-100 meters. As you discovered you will cover 100 meters at 5.5 sec cruising at 65km/h. If you did it on the freeway cruising at 100km/h you would have a reading of 3.6 sec. As your first post says, doing it from stand still gave you constant 6 - 6.3 sec. results. These readings have nothing in common with the published 0-100km/h times of the manufacturer.

If you did the run over 0-400 meters, you would have a reading arguably comparable to 1/4mile times taken at a drag strip. Your reading would not be very accurate for the reasons stated above.

The terminal speed you are referring to may just be the peak hold of your speed reading. Depending on where you got your power source from this may reset each time you turn your ignition off, but during driving it will just display your highest speed since the car has been started.

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I Have a HSK type 1 turbo timer. It does 0-100kph, 0-200kph, 0-300kph. 100m, 200m 400m. 100kph - 150kph amongst a few others. Doing 0-100 i have gotten 4.7 down a big hill (be good if it was on flat ground). On flat ground around 6.6seconds to 100. Id say it is moderatly accurate. It reads of the wheels speed though.

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My car was a AUTO so it has 4.3:1 dif ratio

Biger type supra front mount intercooler

VL T3 turbo with T4 59mm front wheel & race bearings & housing machined to suit

hks suppa dragger exaust 3" from dump pipe back

K&N filter with sectioned off in engine bay with a air dam from M-SPEC front spoiler feed into the sectioned partition with air filter (Nice cold air induction setup)

I am using 265/35/18 rears..

I am using a Apexi speed meter (not blue screen)

When i did the 4.77 there was no wheel spin. A freezing cold night and i got a real good launch (Churp when the clutch let out and I did not wheel spin)

I got a 13.28 second quarter mile also... about 5 mins after the 4.77 run.. however the launch was NO WHERE NEAR as good as the launch with 4.77 0-100.. so a good launch over the quarter may be interestly close to the 12.s.. Yes ??? Who knows..

With the auto dif i am on the rev limiter in second gear at about 101 - 102km per hour... its really zippy.. (I cant get huge wheel spin by flooring it in frist as soon as i floor it im on the rev limiter and have to go to second then i just get traction.. but if i launch hard with the clutch it wheel spins like nothing else so i have to take the starts easy or il end up doing a high 5 second 0-100)

Using standard AUTO computer so 12PSI spike is the biggest i am getting.. probably 9 - 10psi boost.

Question I have is.. I have a HKS f-CONV computer sitting at home... If i install it. get it tuned on 18 PSI.. if im doin low 13's now.. what will the tune take me down too?

If you guys think ive got about 200rwkw now.. what would the tune get me ??? Its just the stock computer with the 12psi boost cut :)

Yes i realise that my speedo would be out because of the 4.3:1 ratio HOWEVER the apexi speed meter allows you to adjust it to the correct setting. (My speedo on the dash is wrong but the speed meter speedo is correct as ive checked it with varios other cars on the road)

My friend was also counting the 0-100 time and he said the speed meter stoped timing before he could say 5.. So i dare say its pretty acurate.

Not bad for a engine thats done 170,000kms... 169,000 of that was done with a Auto gearbox.. so hopefully my engine still has alot of life left in her..

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ohhh.. best time with auto was 13.57 quarter mile and 5.75 0-100km/h

Then i installed the high flow turbo which slowed the times down to 14.08 - 14.4 and 0-100 in 5.9 - 6 seconds.

I dont know why the turbo upgrade SLOWED me down with the auto but it seems to be doing a awesome job with the 5 speed...

Anyone have any ideas / explenations ?

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Originally posted by MrMayhem

if it reads through wheels ..... its a joke

Why would that be? Assuming that you've correctly imputted the size of wheel, should this be a more accurate way of judging when the car actually hits 100kph compared with the accelrometer in the G-Tech?

Just an observation, I have an Apexi RSM installed in my Supra and a G-Tech to take between cars and under the same conditions, the readings can be up to half a second apart with the G-Tech readings being the faster one. My times are 4.7 to 5.1 (according to the RSM) depending on conditions as traction is a BIG problem with the Supra even with S03s. I can't tell for sure which one is more accurate but I tend to trust the RSM numbers more just because it is reading off the wheels.

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Taking the reading at the wheels means that if your spinning the wheels all the way to 100, your going to get faster times. ie. your wheels will be doing 100km/h, but the car won't be :P

The only real way to do it is one of those bolt on speed sensors that 'watch' the ground and take the reading from that.

Of course there's other ways like using cops radar, 1/4 mile strip to get speed at 60' and TS etc.....

J

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That's not true at all. Your wheel spinning at the start up is irrelevant unless you're measuring 0-400 times. Why? because in calculating 0-100 times you're not measuring distance, you're measuring how fast the wheel is spinning in order to attain a speed of 100kph.

Say you're running 235/35/18 with an outer tyre diameter of 26 inches, the RSM will be looking for a wheel rpm that when multiplied by pi X 26/0.0225 (inches to metre) x 60 (min per hour) will give you the figure of 100,000 metres/hour. The RSM will stop when it detects that your wheel is spinning at that speed so unless your wheels were spinning at this ridiculous rpm right at start up (in which case you'd already be looking at the scenery sideways), the RSM can't be confused by the wheel spinning.

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Jay, missed your assumption that you're spinning all the way to 100kph. Yes you're right if your car's spinning all the way to 100 but I doubt many performance cars on the street can lay that sort of claim. My BPU++ Supra puts down 415rwhp on 98 Octane fuel which you might say, is not a lot, but as a guideline this car will chirp its wheels in second gear with ETC off and settle down at around 70kph but it is still unable to spin its wheel all the way to 100kph. If a GTR is to do that on all 4 wheels, I guess we're talking about at least 600rwhp :P Hence for most mere mortals, I think the RSM should work just fine.

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mtam22 - no worries dude. Spining the wheels to 100km/p is possible. I've done it in my skyline, although I'd say the cheapie tyres (at the time) would have had alot to do with that :D

I can just touch 100km/p in the top of 2nd gear. I found that out one day when I was dragging a VN. Dumped 1st gear, it just spun, flicked it into 2nd and floored it and I watched the speedo spin around to 100 then I heard the dreaded, da da da da as it bounced of the rev limit :) LOL

But yeah, as you said, as long as all the correct information is entered in, and as long as there's no wheel spin at 100, it should be pretty much spot on.

J

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i wreckon if i tried i could hit the speedo in less then 3 seconds to 100ks from stand still.. but it would be just huge wheel spin on rev limited second gear dump....

But when you do a 0-100 you dont drive it like that to get the fastest possible time

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