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turbo on an automatic....

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16K views 70 replies 32 participants last post by  str8upclownen  
#1 ·
ok people, I'm sure some of you have a good detailed responce to this guys post. help me out here. I could give him a 2 word responce, but i'm sure it wouldn't be what he's looking for...lol here it is...

"please convince my freind that. . ..
it is not a good idea too turbo his 91 AUTOMATIC n/a
i keep on telling him, but since i am still new with my mr2, he wont believe me.
will you guys who know more, let him know why???"
 
#2 ·
Why not? This is the best idea, yet! The torque converter of the automatic transmission allows the engine to rev to about the desired RPM range under a slight load and build up boost before launching. I am not sure why you are trying to talk him out of it.

Just kidding...God No. Don't use an automatic in anything but your father's Oldsmobile. It is a sports car! It has a high reving engine that will greatly benefit from 5 gears to find the correct RPM point.
 
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#5 ·
Yeah, geez. I mean, sure, all the really fast muscle drag cars use automatic transmissions, but they're totally different from the MR2. TOTALLY DIFFERENT. And hey, there's absolutely no fun in installing an aftermarket transmission controller and paddle shifters. No fun at all...
 
#6 ·
I think you guys saw 'automatic' and stopped reading.

If the car is an automatic NA already, putting a low pressure turbo on it would be an easy path to more power. Problem is, most people who want forced induction can't fathom stopping at 'low pressure'.

Despite what you read, automatic transmissions aren't the horrible beings that people make the out to be. From a practical standpoint, he needs to consider 1) how much power can the transaxle ultimately handle (I don't know the answer to that, but would presume it is much less than 170whp) and 2) how much money is he willing to spend (turboing a 5SFE has been done successfully and it ain't cheap)?
 
#9 ·
David/Bill...let us know when you start racing with an automatic. :)

Like you are pretty much saying...an automatic like the ones in your basic stock cars are good for muscle cars with big engines and low end torque, but I don't think they are good with a roadster style car with a a 4 cylinder high reving motor that you may take to the track.

I have built Pontiac Trans AMs with and without Automatic Transmissions. The 455CI, I put an 3 speed automatic and it would light the tires as much as I wanted from a stop through all 3 gears. The 400CI, I put a Doug Nash 5 Speed and it was a very different car.
 
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#10 ·
unless he pairs the motor with a sequential manual transmission (with an automated clutch and without the use of a torque converter), there's no point really...even if the stock auto tranny can handle the boosted power, the slow shifts and the not-so-smart tranny ECU would bog the car down (hence; no point really).
 
#11 ·
I'm trying to consider why someone would want to do this. Generally, it's because they either can't drive stick and don't want to learn or they have a disability that prevents them from being able to properly drive a manual transmission car.

Would an automatic be a completely different beast from a manual? Absolutely! But that wasn't the question.

Turbos and automatics actually tend to go very well together. You can stay on boost while it shifts and avoid some of the lag that you get when you aren't abuse shifting a manual. Would the ECT in the MR2 be a good match? I have no idea - but I'm not going to simply jump on the 'automatics suck' bandwagon when there are many scenarios in which it wouldn't.

My Corvette has a 4 speed and I wish it were Automatic. The Auto available for my particular car was a Powerglide 2 speed...and I think I'd still prefer it for that particular car.
 
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#12 ·
You would think a forum of enthusiasts wouldn't be so blind when you mention the word "automatic". Most modern automatic transmissions can shift faster than you can on your best day. What in the hell does having a big torquey motor have to do with anything? Based on people's assumptions, you would think they haven't driven an automatic transmission since 1962...

Given that Toyota has 5 and 6 speed automatics, it's certainly not a matter of not having enough gearing. Seriously, how cool would a 6 speed paddle shifted 3sgte be? I wasn't kidding when I said you can get an aftermarket transmission controller and paddle shifters and have buttloads of fun in an MR2. Screw two-steps and launch control. How about programming a transmission to shift at the right RPM every single time? How about never ever missing a shift again? How about completely predictable runs down the strip every time? How about fast fast fast downshifting on the track without dealing with worn synchros, imperfect rev matching, and tons of weight shift?

Nah, it's a slushbox. Couldn't possibly be any benefits to that. Let's just throw the whole idea out and never explore it. After all, everyone knows that the best of the best innovate by never trying new things and always sticking to the old and familiar and comfortable.

http://www.powertraincontrolsolutions.com/content-4.html
 
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#13 ·
Blueroo said:
You would think a forum of enthusiasts wouldn't be so blind when you mention the word "automatic". Most modern automatic transmissions can shift faster than you can on your best day. What in the hell does having a big torquey motor have to do with anything? Based on people's assumptions, you would think they haven't driven an automatic transmission since 1962...

Given that Toyota has 5 and 6 speed automatics, it's certainly not a matter of not having enough gearing. Seriously, how cool would a 6 speed paddle shifted 3sgte be? I wasn't kidding when I said you can get an aftermarket transmission controller and paddle shifters and have buttloads of fun in an MR2. Screw two-steps and launch control. How about programming a transmission to shift at the right RPM every single time? How about never ever missing a shift again? How about completely predictable runs down the strip every time? How about fast fast fast downshifting on the track without dealing with worn synchros, imperfect rev matching, and tons of weight shift?

Nah, it's a slushbox. Couldn't possibly be any benefits to that. Let's just throw the whole idea out and never explore it. After all, everyone knows that the best of the best innovate by never trying new things and always sticking to the old and familiar and comfortable.

http://www.powertraincontrolsolutions.com/content-4.html
Click to expand...
Excellent post!

bill
 
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#14 ·
Neither 5SFE auto or 5speed trans will burn out unless he leaving every red light at 7000rpm. He will have to use a 3SGTE from an automatic 99-02 Caldina. Which would be a good swap correct me if I'm wrong but the Caldina last gen. 3SGTE engine makes some where around 240hp/200lbs.
 
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#16 ·
I don't want to spend $4-5K to swap for used engine and transmission. I have a car with a perfectly good motor already. I don't want to win drag races. If I can pick up a kit for $600-700 dollars from some one on this board and get a 50hp gain (a nice upgrade for the price if you ask me) why shouldn't I do it. Are all the gains of adding a turbo going to be lost because I have automatic transmission?
 
#17 · (Edited)
David Hawkins said:
Would an automatic be a completely different beast from a manual? Absolutely! But that wasn't the question.
Click to expand...
The original request was about turbo charging the '91 MR2 w/ the stock automatic transmission. To be pedantic, the OP actually asked for convincing arguments to not turbo charge an automatic. It still is a good challenge to make opinions and one of the reasons that I like this forum.

Blueroo said:
You would think a forum of enthusiasts wouldn't be so blind when you mention the word "automatic". Most modern automatic transmissions can shift faster than you can on your best day. What in the hell does having a big torquey motor have to do with anything? Based on people's assumptions, you would think they haven't driven an automatic transmission since 1962...

Given that Toyota has 5 and 6 speed automatics, it's certainly not a matter of not having enough gearing. Seriously, how cool would a 6 speed paddle shifted 3sgte be? I wasn't kidding when I said you can get an aftermarket transmission controller and paddle shifters and have buttloads of fun in an MR2. Screw two-steps and launch control. How about programming a transmission to shift at the right RPM every single time? How about never ever missing a shift again? How about completely predictable runs down the strip every time? How about fast fast fast downshifting on the track without dealing with worn synchros, imperfect rev matching, and tons of weight shift?

Nah, it's a slushbox. Couldn't possibly be any benefits to that. Let's just throw the whole idea out and never explore it. After all, everyone knows that the best of the best innovate by never trying new things and always sticking to the old and familiar and comfortable.

http://www.powertraincontrolsolutions.com/content-4.html
Click to expand...

billwot said:
Excellent post!
Click to expand...

Actually...I think the point of the post is not good in relation to the original post. We are talking about a Toyota MR2 NA transmission. This is NOT a good automatic to make a point. From what I can tell, we are also only talking about slapping a turbo on a relatively bone stock MR2 5SFE w/ an automatic. Given that information, would you still answer the same way?

I agree, not all automatics suck, but we are not talking about a modern 5 or 6 speed transmisison. We are also not talking about an manumatic. I have built good automatics (TH400 w/ shift kit) for a muscle car for the purpose that it was designed. I have been in PowerGlides, 5 speed and 6 speed automatics. The recent trucks have 7 speed. If you want to go down the route of picking a good automatic for a turbo car, then you can justify it with what you have said. You will also need to make sure the transmission was designed for strength and not just increased fuel milage. The first TH700s sucked. They were built for fuel economy. The same goes for many Toyota transmissions. While we are at it, we can discuss the CVT transmission as well.

Suggesting that people haven't driven in a car with a good automatic transmission due to an answer about the original post is getting off topic. It has nothing to do with my experience in various automatic transmission cars. I have experienced many, many automatic transmission and manual transmission setups.
 
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#19 ·
TheHorniak said:
its a toss up. a fully aftermarket controlled auto would be sick with paddles.allowing hard shifts and everything. but if its a stock controlled stock auto then i dont see the fun in it, at all.
Click to expand...
That might be possible? The last years of the Caldina did come with a controlled auto trans. (tiptronic is what I think you call them?) There was a paddle shifter kit for sale on Spyder Chat a while back.
 
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#20 ·
#21 ·
billwot said:
Do you have some evidence/documentation to validate that statement?

bill
Click to expand...

I think the complete lack of evidence is point enough...don't you think. :) At what point do you recommend using the A241E automatic transmission?

From the schematics that I have seen between S54, E153, and A241E, it is clear that the E153 is much beefier than the other 2. This is clear just in the drawings and not by measuring anything. By my experience of breaking automatics (such as TH350) with an engine that has 500HP and the relative comparison of an A241E to the TH350, I am confident that an A241E is not designed for 250+ HP. You may go with the A541E that was designed for the more powerful Solara.
 
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#25 ·
billwot said:
Nope. The auto tranny is fully capable of handling 200-250 WHP.

Strip-only drag racers have been using suto trannies for years.

bill
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I have just heard differently, otherwise i might do an automatic =)
This may be a good thing to try someday so I can speak from personal experience.
 
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