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The mkiv Supra Owners Club

More power isn't giving better ET


SimonR
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Hmmm. In September last year I got a quarter-mile time of [email protected] (60ft 2.423). The only mods at that time were HKS FCD and a Blitz DSBC set to approx 13psi. I had an open diff with skinny 225 tyres. I was getting wheelspin on one side off the line (which turned out to be a suspension problem - now sorted).

 

Since then I have added: 440cc injectors, FMIC, Emanage, LSD, 275 rear tyres and turned the boost up to 17.5psi. I dyno'd at 290rwhp@1 bar so I'm guessing that at 17.5psi I should be well over 300rwhp. Torque was 300lb-ft at the wheels from 3,000-6,000rpm at 1 bar and that's bound to be up also at 17.5psi.

 

So why, at the Pod yesterday, was my best time [email protected] (60ft 2.420)? I accept that I'm a crap driver and that it was v hot yesterday but I must have at least an additional 80rwhp since last year. I can't believe that would only take .16 seconds off my time. Plus I had no wheelspin so no time lost there.

 

This isn't really a question about tuning, more about why I can't seem to translate extra power into better times - even having cured the traction problems.

 

The only thing that I can think of is that I had the Emanage set up at 1 bar and that moving to 17.5psi could have thrown out the AFR so the power is actually down.

 

Any ideas? All help gratefully received as this is starting to wind me up. :mad: I'm thinking of moving to a big single but there's no point if it's not going to get me better ETs.

 

It's a Soarer TT by the way. Stock is supposed to be 280bhp (crank). Ceramic turbos, parallel not sequential.

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The run last year was at Crail. It was a hot day for Scotland, probably 20-22C. The dyno run was done when the Emanage was installed by Thor earlier this year. As I remember, it was a cold, wet day. Would it make that much difference?

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I think I understand. You're saying that an Emanage map that was set up on a cold wet day for 15psi could give odd results at 17.5 psi on a hot dry day like yesterday? Cold damp air being more dense than hot dry air, therefore carrying more Oxygen?

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I see, charge temperatures and density. Some of the other guys there yesterday were spraying their intercoolers with water before each race. I had read that spraying CO2 or Nitrous onto the IC can make a difference but I never realised that temp/density of air could make that much difference. I wonder if there are any formulas for calculating to what degree (no pun intended) power is affected this way?

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you will drop a serious amount of power due to heat. It must have been 30degrees or above at Pod and that will knock a lot of power out of the car. A good FMIC will help but they only help once air flows through them, otherwise its just hot air running through the system.

 

The ideal day for pod is around the start of September when its cloudy with a following wind. The air is cooler and denser, the track has been warmed up nicely for the summer and is normally treated and the following wind can reduce the 1/4 mile time nicely.

 

JB

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As i understand alot of people came away with low times yesterday because of the heat. It was my first try at a drag strip yesterday but i didn't get what i was really expecting. :(
you mean high times.

 

How did you do James? What time and trap speed?

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  • 4 weeks later...

what sort of weight is your car? do you have things like cold air feed. you get your 60 foot times down and should take loads off your time. took me ages to get out of 13`s into 12`s each time i went i was knocking a couple of tenth`s off my time.

 

what sort of revs are you launching at?

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That standard weight is 1560kg. The stock airbox is behind the headlight and I've made some home-butchery mods to increase airflow plus K&N filter. It's not so much short of power as crap off the line. I power-brake, rev it 3,000 then release. All that happens is that the revs bog down and slowly rise until I'm in the power and then it's away. No traction probs - 275's with LSD.

 

I've bought an HKS GT3040 to replace the stock ceramics so I should see another 100bhp from that when it's installed. Next step might be a high-stall TC if the budget can stand it.

 

Perhaps you can answer me a question, Mark. I'm a bit confused about how a TC should behave. Is it the case that if I power-brake and then wind up the revs more and more I will eventually hit the stall point and the wheels will start to spin? Or will I just knacker the TC?

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it allows you to hold on line with more revs for mor boost off line. you get to a certain stage then wheels just start spinning so you back off a bit. its about same weight as supra.i noticed after getting higher tc that it would light tires up so easy, but if you sat on line giving it more revs you will also have more heat building up which is what kills the gearboxes.

 

on stock stall you can get to about 2000 rpms before tires start spinning on spot.thats where some sticky tyres come in handy.

best 60 ft i had on cheap kumos was 2.050

 

do the soarer have a a340 auto????????????

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Took Mmarks advice at ROTORSTOCK II Shakespere County Raceway in May this year, got my best run with headlight out think that may have helped the air feed although it was unlimited runs there did bout 5runs just got quicker and quicker. Called it a day at 12.890 @113.18, got 2nd fastest time out of the collection Jap car driving chums i went there with. Was the fastest until mate Tom's last run in an R33 GTR pulled a 12.4 outta the bag.

 

It was reasonably warm at Rotorstock, but didn't run my car at the last JapShow, it was way too hot Sat and Sun so i just watched the track and got heatstroke instead!

:violin:

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