Topn Speed?

[Philly#1 Lex]

Say I wanted to achieve a 170-180mph top speed in a SC400. Is it possible? I mean I will have a an R154, 1UZ( Stock rev limit 6300rpm), ANd I am undecided on whether to keep stock 3.9 gears and and LSD, Supra 4.27 will make me lose top end or Supra 3.2(Not Sure) a lose some quater mile quickness I am assuming. How can I calculate a Top speed? I dont know R154 gear numbers or I would try to find a calculator online. Any questions or hints. Thanks

 

[Zuffen]

Unless you live in Germany or the Northern Territory in Australia there's nowhere to legally do 170MPH. At this speed they don't just take your licence they also lock you up and perhaps never give your licence back.

I generally figure 120MPH is the limit of survivability in older cars when things go wrong.

I'd be curious where you could/would do that speed.

 

[Philly#1 Lex]

I would be doing that speed in germany.

 

[Peewee]

Based on a 627mm tyre height, you'd need a 3.5:1 diff to do 175mph @6300 in 5th with an R154

Assuming a 650mm tyre height (for the hell of it), you could just get away with a 3.7:1 diff.

 

[Zuffen]

I haven't gone quite that fast in germany but I've gone close.

Have hit 150mph in The Northern Territory.

Things rush up at you very fast at that speed.

I've survived a blow out at 135MPH (on the road not the track) and don't want to do it agian. Perhaps that's why my first wife left?

 

[Philly#1 Lex]

Peewee what diff would you recommend I use? My tire sizes are 265/35/ZR18 in the back and 245/40/ZR18. Rims are 8.5 in the front and 9.5 in the rear. Could any of the Supra's diffs help me ? Thanks. And Zuffen I have done 150mph quite a few times on the highways in Europe. I know things come up very quick. And I have also had a blowout at 100mph with my little s#*! basket Fiat, and It wasn't fun. I know the risk envolved, thanks for the heads up as well.

 

[sniper]

Supra can go 300K, 187ish mph easy so im sure the 400 can do it. But realisticly, you are probibly going to need more then gear ratios, you are going to need more power. That that kinda RPM, the 1UZ doesnt make good power and if you over rid the stock rev limit to get more revs, it wouldnt do much because again, it makes no power up there NA. So i would suggest looking into FI, either a blower or turbo. Nitrous wouldnt be smart at that high in the revs for a long period of time. You can get the gears to take you to 180 but i dont think the power is going to be there, so either you wont hit it, or you will wait a looooooooong time. Example, my SC430 only did about 147 down a 1.5 mile ish, road. And i was at 147 for quite a while and it just seem to have the power to keep going.

 

[Philly#1 Lex]

The Car will be turbo'ed. I am aiming for 500-600 RWHP for the SC400. Thats why I wanted to know the gearing. I think with that much power I should be able to go more than the stock 150mph. Just need to know if the SC4 3.9 ratio and a R154 will take me there or not. Or could I swap in one of the supra's diff w/lsd and knock out two birds with one stone.

 

[Murphy]

You should be able to do well over 200mph with that much power.

 

[Philly#1 Lex]

With a R154 and what gearing?

 

[Murphy]

I don't know about the gearing, I'm in the figuring stage on that too. My main interest here is land speed racing. With 500 rwhp theoretically you should be able to do 219 mph.

Spreadsheet is attached and you can play with the numbers yourself. Frontal area and Cd are correct for your car.

 

[Murphy]

Here's another spreadsheet that will let you calculate your speed in any gear. This should solve your gearing question.

 

[Philly#1 Lex]

does anyone know the r154 gear numbers?

 

[Murphy]

right here: http://www.toysport.com/Technical Information/Transmissions.htm

 

[Philly#1 Lex]

Thanks Murphy. That's very helpful. The R154 will be more than enough for my needs. Now time to figure out how much horsepower I need to reach those speeds. Do have any more of Those Helpful calculators do you?

 

[Murphy]

The two I posted should be all you need for those calculations.

The first one I got from www.mayfco.com , click your way to the analysis page, very good stuff there.

 

[sc400173mph]

Say I wanted to achieve a 170-180mph top speed in a SC400. Is it possible? I mean I will have a an R154, 1UZ( Stock rev limit 6300rpm), ANd I am undecided on whether to keep stock 3.9 gears and and LSD, Supra 4.27 will make me lose top end or Supra 3.2(Not Sure) a lose some quater mile quickness I am assuming. How can I calculate a Top speed? I dont know R154 gear numbers or I would try to find a calculator online. Any questions or hints. Thanks

you can do it stock. I know not to many people can believe that but its true. I had a 92' SC400 stock, auto, and on a 4-5 mile long straight road I saw the needle hovering around 170mph. at the end is about a 10 degree turn and the steering was about 100lb harder to move than normal, I almost drove into lake superior's bay harbor. B4 93'= no speed limiter this was about 10 years ago and I would never do something that stupid again so no need to tell me it was stupid....I know it was.

 

[spf_lexus]

Underside aerodynamics are often overlooked as a way to raise top speed w/o adding any hp. Lowering the car an 1.5" will really help you keep climbing as well as a front bumper splitter and a rear diffuser.