now before you flame me for not searching,i have already searched with no helpful answers.

now i'm in the process to start gathering parts to put an s/c on my car and before i spend money on a lost cause i want to know how the 12a in my '85 will handle the boost,and a safe psi,i always hear boost in, apex seals out wtih 13b's but i have never heard very many horror stories with the 12a.

also when it comes to the carb,should i tune the stock carb for the boost ,modify it,or should i switch to a different carb?

one last thing i should mention is this will a DD and a weekend auto-x/gymkhana warrior.

thanks for any help in advance,and sorry for my lack of knowledge regarding carb's

 

Seriously you searched? if you did you would have found 340913273240938741 topics on the subject.

They're all the same, good parts, safe tuning, no problems. And if you were actually concerned about auto-x/gymkhana (esp, gymkhana) you'd skip the turbo altogether.

 

He did skip the turbo. He said S/C reffering to a Supercharger

 

two good reasons 12a's outlast 13b's...

the rotors are shorter and the apex seals are 3mm stock. this makes them short and fat compared to long and skinny.

would you rather fight Brock Lesner or Yao ming?

boost away...

 

yes i searched,maybe i didn't use very good keywords.like firebirdslayer666 metioned, i am skipping turbo,because a S/C setup would better suite the auto-x/gymkhana area giving me the low end bump i would need to get out of the corners.i may be new here, but i'm not a noob when it comes to these sort of things

Thanks for that very helpful bit of info sen2two,that gives me a better peace of mind about it


Now i just need alil info about how i should go about the carb setup,if the stock carb can handle it with some tweaking/modding.If you can point me to a thread regarding boosting with a carb and what to do with the hoses going to the air cleaner when switching to a carb hat,I would be in your debt,

And thanks again guys for the help so far!

 

When it comes down to it, boost is boost. If you search for S/C related threads, then I am not surprised that you didn't find much as turbos are a lot more common. What you want to do if running a carb is to search for "blowthrough (or blowthru) turbo" or similar terms. Also search for "boost prep", "carb boost prep", etc. There are a lot of guys running a blowthru turbo with good success. You are basically doing the same thing..just replacing the source of the boost. Holley and Webers are probably the most common carb for doing this, but some have boost prepped the stock Nikki.

If you play it safe on timing (search for locked dizzy or locked distributor), get enough fuel (enough pressure/flow from pump, boost prep carb), and don't go crazy with the boost, the 12A can do quite well.

Have you really looked into the S/C setup? What type are you planning to run? I know that many who have run the Camden S/Cs have been a bit disappointed with power and dealing with the heat produced.

Good luck.

 

oh boy another supercharger setup.

If your gonna go with a charger and a 12a I would go with the 5" charger it put out less heat for one. I had more fun with the 5" 650 holley at the track.
The 7" charger put out a lot more heat. and it almost the same size as your 12a.
the only problem with a carbed setup was the floats in the corners.

unless you thinking EFI, but i don't think atkins is selling the EFI setup any more because it don't ****** WORK. believe me, I've been there.

I just got done puting a 7" camden on a 13b 1\2 bridge with a 650 dbl pumper. we will see how it works out. your money would be better spent on a turbo setup.





This is the 7" on the 1\2 bridge

 

thanks for the help guys! I plan on using a toyota s/c unit out of either the mr2's(sc12) or previa van(sc14) and putting it where the a/c compresser currently resides.i have already determined a pully setup seeing as the s/c's used a ribbed belt opposed to the v belt that the 12a use's,so no problem there.

But i will be searching/reading up on blowthrough setups and go from there,Thanks again guys,yall gave me some very informative help!

 

Way too small. Might try an Eaton M90 or something of that sort.

 

instead of using a roots style charger. you could always get a centrifugal style charger. looks like a turbo. but you would mount it like you would your AC or Power steering. takes up much less space. you could get any random one and have a mount made.

http://auto.howstuffworks.com/supercharger4.htm

 

The Eaton M90 came on the Super Coupe Thunderbirds of the early 90's just as an FYI so they aren't too hard to find. Pretty good size supercharger and being an Eaton/Magnusen it's built solid. These you would use as a Draw Thru set up carb wise. Just like Sen2two said, you could always use a centrifugal style supercharger and set it up like a Blow Thru turbo.

 

M90s don't like to have gas flowing through them. It has to be either EFI or blow-through.

Centrifugal blowers won't going to give you the midrange a Roots blower will, which is the more important thing for an autocross/gymkhana car.

 

the m90 crossed my mind,and is on the list,but coming from aw11 mr2's i lean more towards the sc12/14,seeing as they can put a decent amount of boost with different size pulleys,can be had just as easy as the m90 and is more suited towards my power goals.right now i'm just looking for a semi decent increase in power,and i've seen the potential of the sc12/14's first hand.

Now regarding draw through carb setups,i really don't like the idea of ready to go fuel air mixture being compressed in an s/c or turbo,it makes very uneasy,never know if it gonna work as planned or if it decide's to become a bomb,lol,no offense but it's just not for me.

 

It's going to be very difficult to try and do a roots/blow thru style set up. I don't believe I've ever seen one. Rotary's flow alot more air than a normal piston motor so you have to take that into account when looking at anything for boost. Most factory superchargers are probably too small and don't flow enough CFM to keep things happy. Same goes for turbochargers.

 

Why would it be difficult? Same as any other blow-through supercharged setup. The M90 can be mounted in any orientation, so that makes things easier.

But yeah, an MR2 blower probably won't even boost on a rotary.

 

Unless you plan to mount it sideways on top of the block where the rats nest was, I don't think you'd have room to mount ther blower on top of the carb and still have a decent intake manifold. Then you hace to figure out a way to rig the intake to the blower. I'd love to see how that set up is supposed to work cause I don't see it happening

 

you have a point there about the cfm's,i tend to forget that the rotary can flow as much air as a large 4 cyl,or small 6 cyl,lol

and on the mounting, i would be ditching the a/c compresser and mounting the s/c there,and just build/buy a carb hat.it's pretty much gonna be like a 12at but s/c instead.i have no clue if that makes since or not,but it does in my head,lol.

now regarding the intake,should i put an intercooler in,i've heard of guys put intercoolers on their stock 12at's and they say it just dosen't run the same,or is that cause they are used to the respose of the stock setups less than a foot of piping?

idk if any of this makes

 

It makes sense to me. My concern is whether it would interfere with the header. A centrifugal blower could go there easily, but most Roots superchargers are pretty long. Also, better make sure to wrap the header and use good heat shielding.

If it were me, I'd consider mounting it on top of the engine, upside down, and relocating the alternator to the side.

As for an intercooler, it's up to you, but personally I wouldn't bother unless you're pushing more than 10 PSI. It probably wouldn't be worth the extra cost and complexity. Response isn't something I'd be too worried about, since it's already going to be inherently better than that of a turbo.

Since it'll be blow-through, don't forget some sort of blow-off/bypass valve.

 

Try this one on for size. A RX3 drag car.

 

Remember he said he wants to mount it in the A/C compressor location, which is on the driver side. A centrifugal would look exactly like bad83 posted with the RX-3 drag car. Wouldn't need to worry about the header at that point. A roots style just wouldn't work any other way besides a draw thru on these cars.

 

D'oh. When he said 12AT, I was thinking air pump. That's what I get for not having AC or an air pump for so long.

But I'm quite confused why you think you can't do a blow-through Roots blower. It would look exactly like the setup posted above except... instead of a centrifugal supercharger, there would be a Roots supercharger.

 

just buy my 12at and call it a day

 

The supercharger would need to be mounted upside down first of all. If he went with a Camden styler unit it may work, with the intake needing to be fed to what is now the bottom of the supercharger. If it's an Eaton or any other supercharger designed for fuel injection, the intake for it is on the back of the blower. With the steering linkage and everything that's there, I don't see how it could be made to work. Now there are aftermarket blowers that have the intake/throttle body on the front side and the pulley is shaft driven to the back, but now you're way out of the OP's price range for the build. Not to mention you've just made it impossible to change spark plugs without taking the blower off.

 

I went out and took some measurements on my car just now. It's going to be a very tight fit due to the length of the M90. You can apparently get different length drives for them, and getting a shorter one would help immensely, possibly allowing you to mount it on top of the engine as I previously recommended. With the standard one, the only place I can realistically see it happening is on the passenger side above the header.

Perhaps a better option would be an M62. It's a bit shorter, and should still work alright on a 12A.

 

Took me a little bit of digging, but I found a rotary with a M90.

http://www.youtube.com/watch?v=VY4yu...eature=related