Boost'n

I was planning on getting a sc300 real soon, but its kinda hard finding a 5 speed. Could anyone here tell me what is the disadvantage of turbocharging a automatic vs. 5 speed?

slowtan

I was talking to Jarett/ Powerhouse racing and he says that you can turbo an automatic up to 400Hp with no problems or no mods needed to your tranny. A 5 speed can hold up to more power. He was going to sell me a Supra single turbo kit with intercooler for $5,000 but I needed some custom piping that was going to cost me an extra $200 - 600 . After hearing those prices I decieded to work on my stereo system .

I rather have reliable car with a good stereo than a speed demon that would be extremely loud , poor on gas , and un-reliable .

I already have Chevy truck with a supercharged 383. I don't need 2 vehicles with extreme power .

I am keeping my car looking stock but performing and sounding a little better .

I am plan to get an intake system and a SAFC..

Bean

iTrader: (1)

don't listen to him Boost'n that truck won't touch a turbo'd SC300

What he heard from PHR is correct. The automatic won't launch as hard until you get a torque converter...
Your 1/4 mile times will be much more consistent with a automatic...

when built and setup correctly; an automatic becomes a drag racing tranny... the 5-speed or 6-speed is MUCH more fun to drive though

Slick Lex Coupe

Something else to consider with the auto is that you can't go any faster than 140mph. A stock 300 runs up there pretty quick so a 400+ hp one would be right up at redline in top gear in no time at all. 140mph is fast, but I would want faster with a high power car. I like the late night highway runs.

Mudvayne

i'm also thinkin about this (turbo w/ auto).

isnt there a way around the top spd of 140? either with ecu or gear ratios or something in an auto? i'm not all that experianced with thses cars so i would like to know.

and after the turbo kit, what is a good TC for the sc300?

thnx, peace

Lex Luthor

You are not limited to 140mph with the automatic, the auto will launch more consistently as Bean said, but what everyone seems to forget is that there is virtually no boost dropoff between shifts, at least once the shift firmness is straightened out, making it a better choice for drag use, and that is why I plan to build an auto. The stick is definitely more fun though, nothing like diving into a back mountain road, hitting the curve as you downshift and heel-toe....

amati5

From what i understand which could be wrong, turbo charge kicks in at certain rpm . With a manual trans, you can get to that rpm quicker than the auto trans can. Also, with the manual trans, you can stay on certain gear to maintain your engine speed at that rpm so the turbo can be ready for your immediate demand.

I would think auto trans work better with super charger (belt driven) which is active at all any rpm. It'll cost you more money for gas though

Can someone confirm this?

Thx

SC300T

Here's my .02.....With a small to mid sized turbo, T60, To4e, or so, you'll spool at 2000 rpm with good exhaust and stock compression. With the torque this setup makes, the flash stall will be significantly higher than stock, say 2400 rpm or so... As soon as you stomp the pedal, you'll be at this rpm or higher, which puts the turbo well into the boost range. Its true that you'll get a little lag, but by the time the turbo spools fully at 3000rpm, you'll forget about even considering a supercharger. Between 3000 and 7000 rpm it will be a nice wide power band that is well suited to automatics.

The other benefits to an automatic is that it will launch better, be more forgiving on the rest of the drive train, yield consistent performance, and won't drop boost between shifts.

Holding the automatic in a lower gear manually, you can keep the RPMs up as high as you need... You don't really need to have the revs all the way up in most cases, you can just pull it out of 4th o/d... 3rd will give you enough RPMs to build boost quickly.

As you increase HP over 500rwhp, you can just give it to SP to have them build the automatic and replace the diff with a Supra TT Automatic LSD... No need to buy a $6000 Supra 6spd.

That said...I still like my fussy manual...

Lex Luthor

Scott, exactly my point, thank you.

SCV8

I'd probably get an auto for a turbo project,that way the lag from a larger turbo wouldn't be a bog,but instead tuned to work with a torque convertor.Just my .02.
Plus,there wouldn't be any closing of the throttle on upshifts.

SC300TURBO

iTrader: (2)

turbos are faster than SC....the lag on a turbo is so minimal in a small to midsized turbo its not even worth noting...and besides for daily driving you have that STOCK driving range for snow or rain...or just fuel economy.....and when the boost kicks in...hold on...these motors were made for turbos...please add tham and have fun...see why im such a happy person all the time


that was from slowtan/......nothing could be more untrue....my sc300 is VERY quiet and makes over 500rwwhp....you hear a very slight rumble from the exahust....many on here have seen or been in my car and can vouch.....and my car is a daily driver that takes me from miami to atlanta every year for nopi nationals......i have 127k on my car and drive it hard as ****...she has never let me down yet....so turbos...high hp on an sc300 are reliable and quiet if you get a toyomoto kit.....you wont regret it...Jeff

Slick Lex Coupe

How aren't you? With the exception of changing gear ratios in the transmission you are. A differerent rear end may give some extra mph up top, but will not be anything drastic. As far as I know all SC300 autos are redline limited to 141 mph. It's not a rev or speed limiter, the car is just out of gears.

Lex Luthor

You say changing rear end ratios won't do anything drastic? Go from a 3.92 ring and pinion to a 2.73, and tell me it didn't make a drastic difference on the top end. Slick Lex Coupe, if a stock SC3 is limited to 140mph (not electronically, mechanically) that would mean it takes about 170 rwhp to push the SC3's body (can't recall the drag coefficient, i'm sure someone here can) through the air at, for instance, 6500rpm. If you are making 200rwhp more at that given rpm, whether stick or auto, regardless of rear axle ratio, it will now be far easier to push the vehicle's weight and aerodynamic drag through the air, resulting in a higher vehicle speed per engine speed, assuming there is more hp available throughout the power band. Jeff, I never realized you've never had a failure since she's been turbo, that's one strong testimonial.
- Jon

Slick Lex Coupe

Lex Luthor,

The change in rear end you posted definately makes sense, but isn't that a drastic drop? Most likely you would use a one of the Supra TT rear ends. Does anyone know what ratios they are? You are right about the drag. I forgot about the whole drag to hp ratio. Now that we are really getting into this does anybody have what they think would be a reasonable guess of the top speed of a mid size turbo'd SC300 with auto and Supra rear end?

SupraCoup3

.31 drag co-ef. w/ front spoiler
.32 w/out

pop pop cherio