666cody666

i have a 85 gsl and i wanted to do a tII swap later down the road and i knew about 12at's but never thought of doing one till a week ago. my question is are the 12at motors less reliable at 500hp then a 500hp 13BT motor? also it like just a bolt in engine if you get the jdm engine?

Naegleria_Fowleri

There are too many loose variables in your questions. It is 100% dependant upon how well the engines are built and how much effort is put into it. The engine is bolt in pretty much, but because it is fuel injected you need to have an ecu to run the fuel injection system, whether it be the stock system or otherwise.

666cody666

i thought they were carbed cuz one guy had one for sale with a modded nikki on it?

Naegleria_Fowleri

The jdm 12at's are definitely fuel injected. I was looking into buying them a couple years back when I first got my '83. I ultimately decided it wasn't worth it. If you want to turbo your 12a, it will cost about the same amount as going with a 12at with a standalone system, along with buying a front mount, and all the other necessary things to make good power out of it.

Atop of that, the 13bt is the best route to go because most of the 12at's came out of automatic Cosmo's (iirc), which means you would need to buy all new clutch, flywheel, pp, and all of that jazz as well. Then you have wiring. If you are going to go through all that trouble, why not get a 13bt for the same cost and have even more power? Last I checked, which its been a good year, the 12at's were running for around 1,200 bucks or something like that.

Then you have the entire problem of actually being able to get your hands on one. That was the second reason I didn't want to get one. I played back and forth with 12at's with Corksport for a good two months and ultimately said to hell with it as they were never calling me back and acted like I was the biggest nuisance in the world trying to get my hands on one. Again, it has been at least a year since I was looking into them.

666cody666

hmm i geuss it would be the same. i just had the thought of beening different at have a 12at with 250hp then go for 500 later down in life. the thing with the 13b swap i would have to look for a se front cover and get that front mount from racing beat, but i geuss for more power why not put the extra work.

Naegleria_Fowleri

Yeah, if you don't want to do that there are lots of people who turbo the 12a themselves, which is what you saw with the modified nikki carb. That works out really well too, and you can make tons of power through that. The only problem with that is that you have to have the carb shipped out to be boost prepped by someone like Robert at Rotaryshack.com, maybe Rx7Carl or Sterling could do it too (I've not heard of them boost prepping). Then its pretty much just piecing turbo parts together since there aren't any official kits by any means.

If you go that route you can also buy kits to fuel inject the 12a as well, which works well for higher horsepower 12a turbos. There are a ton of options out there for you to go to.

I am currently building a streetported 12a that may eventually get boosted, but after the streetport is done I am dropping it in my '84. After that is done I am going to do a 13bt in my '83. Just keep searching until you find out exactly what you want to do. Your options are limitless.

666cody666

do you have links to the ppl who have feul injected kits for the 12a?

Naegleria_Fowleri

No I don't. Its never been one of the setups I've ever considered, so I never looked it up.

trochoid

iTrader: (6)

http://www.tweakit.net/shop/

666cody666

hmm fuel injecting my 12a sounds awesome and makes me want to do a 12at motor swap even more but only money will tell

680RWHP12A

it dosnt have to be fuel injected ti go fast.. BLOWTHROUGH

steve84GS TII

I REALLY think his original question is moot......based on the specs he desires.

Most people dont realize how much 500HP is!!
It really doesnt matter which engine you select because at 500HP your gonna have thousands upon thousands of dollars invested in engine upgades,fuel/spark management,safety gear,drivetrain and cooling.Choose which ever engine you like,they are both designed from the factory for forced induction, and both will need working over, to safely and reliably make that much power.

If you wanna keep your HP goals in the realm of 300-350 HP, so you dont have to completely rebuild you chassis/drivetrain.....then the 13BT is a good choice.It can safely make that power in stock form with bolt ons and a T04 turbo.The twin injector sets,better manifolds and vastly larger aftermarket support make it the better candidate,along with the fact that its a larger displacement engine.

666cody666

ya blowthrough would a good idea

666cody666

well the motor that i get wont be running 500hp all the tim eonly at the track or when i want to blow people away

vipernicus42

iTrader: (4)

It doesn't matter how often you end up at 500hp, you have to realize that to even have 500hp at your flywheel for a 10sec run down a 1/4 mile track you're going to need to change basically everything about the car.

The clutch, pressure plate, transmission and rear end won't take that kind of power for any length of time in stock form.

And depending on how you plan to make that power, the engine probably won't either. You can't just take a stock 13bt, shove a huge turbo and some NOS on it and expect to effortlessly make 500hp. Many parts of the engine are going to have to be changed and a full rebuild is definitely in order before you start. I can guarantee that if you force a stock engine even just past 300hp without rebuilding it you'll probably have a short lived motor.

So careful consideration will have to go into every part of your engine build (like I did in my "Ultimate 12a" build thread) as well as porting and the turbo setup you do. I don't know much about them but choice of intercooler, fuel management system, etc.. will make a huge difference.

Think hard about exactly what the car will be used for. 500hp IMHO wouldn't be streetable, and definitely won't be cheap. We're talking thousands of dollars, and hundreds of hours of time invested in it.

Jon

Naegleria_Fowleri

You definitely need to listen to these guys. Atop of that, no one really needs 500 horsepower. Why is it that you think you need that much power? Your car would be plenty quick with half that. A lot quicker than you are apparently thinking it to be. 500 horsepower is a pretty ridiculous number when talking in terms of first gen 7's. Its pretty ridiculous for any 7. No one needs to go that fast unless it is a track only car.

666cody666

so what everyone is saying here is that around 250-350 hp on a 13bt or 12at(maybe) would be enough. well i think it would be a backup to have a engine that can do 500hp just to make sure you beat anyone. also i want to beat one of my dads friends that is drag racer and he has a camaro that does 10 or 11 i belive so....

steve84GS TII

The way you say that......just really puts a picture of inexperience in my head.
Im sorry,Im not trying to be-little you or be condecending,but you dont seem to get it.
If you are going to shoot for 500hp "just to have sometimes...in case" then you are still going to have to build the entire car to handle it "all the time". I really dont think you understand how much 500HP is.That kind of power can twist a chassis,snap an axle, or kill you THE VERY FIRST TIME you use it.So that means you must build the car under the assumption that it is going to be subjected to 500HP ALL THE TIME.What good is having the power,if you are playing russian roulette with your drivetrain and life.

300HP in a lightweight FB chassis is plenty quick.It doesnt require you to make enormous changes to the body or drivetrain,and it is quite reliable and cost effective.I have plenty of experience in this field,as I drive my S5 TII powered 84 every day.I commute,road trip and goof off occasianally in it and have racked up 6 years and over 40,000 miles of successful and safe operation with plenty of thrills.
Theres no reason to need 500HP in a street driven 1st gen.......even if your ONLY goal is to be the fastest car on the road. Any rich chump with a turbo Vette or blown Camaro will be able to best you.In my experience,there is always someone faster and richer,so its more fulfilling to build a well balanced,safe and capable vehicle.....but thats just my opinion.

Naegleria_Fowleri

Just out of curiosity, how old are you? You sound like you are very young. Owning a car should never be about winning everything. It shouldn't be about going as fast as possible all the time. Its primary function is to get from point A to point B. We sports car owners, and more over, Rx7 owners chose our cars not because they are fastest in the world but because they are fun cars. I can understand wanting to have a faster car because as well all know, first gens are far from fast; but building a 10 or 11 second car is an enourmous task. It requires planning beyond planning. It requires top dollar and top experience in everything because if one thing goes wrong at those speeds you are dead. You have to consider the fact that no matter how fast you can go, there will always be someone faster. Your thinking is really naive, and I'm sorry if I come off as a total *******, but I think you really need to set your priorities elsewhere.

PaulFitzwarryne

There is minimum difference in reliability between a 12AT and 13BT properly set up for 500hp, however the 12AT will cost marginally more.

To get to a reliable 500hp 12AT, first start with a rebuilt engine, fully dowelled and make the following upgrades as a minimum:-
1. large street port;
2. add two extra injectors, all four large capacity- say 1600/800cc;
3. large turbo, with add-ons such as BOV, RRR, boost controller, turbo timer etc.;
4. large sized front mounted intercooler;
5. digital fuel/ignition ecu;
6. custom header and efficient 3 1/2" exhaust;
7. deleted rats’ nest, airpump etc;
8. light steel flywheel and high pressure clutch.
9. stronger gearbox, such as a Supra with custom drive shaft;
10. stronger diff, such as from Hi-Lux;
11. large front mounted oil cooler;
12. shorter but wider radiator with extra core;
13. performance Bosch fuel pump and Pieburg pre pump, with surge tank;and
14. upgraded coils, ignition wires etc.

That takes care of the engine. Next upgrade tires, wheels, brakes, springs, shocks, bushes, struts, instrumentation etc., not forgetting body modifications, better seats and possible roll cage.

As for total cost, I would suggest the cost of a rebuilt 12AT would be about 30% of the project budget. It would be a great project if you have the money and mechanical/electronic skills.

500hp is just streetable, but unless you are going to use it for weekend track work the power will be very rarely used. I find my 220rwhp 12AT engine set-up ideal for a daily driver, and am only going 300+rwhp on my wife's car as an excuse for occasional weekend hill climbs events.

EDIT. The above suggested 12AT engine set-up will get you into high 10s low 11s with track only tires on a regular basis. An initial budget of $8,000-$10,000 would be realistic depending on how much work you do yourself.

666cody666

i know you have to build the car to handle it.

i am only 16

i know that 500hp might be a dream for me for a long time but its a thing i want to do later maybe not in this rx7 but others i get. this one i would be good with 300hp for point A to B.also i dont want to be striping my interior out, i want it to look stock all over. for that money part i know how much it costs cuz i have talked to ppl who have 500hp and they have put thousands or money in for rebuilds and parts they broke. so i might be a dumb teenager(not saying you all think that) that doesnt know anything but i know what i want to be having that power later in life.

666cody666

thank you wait whats a RRR? and it that 1600cc ont he primarys and 800cc on the secondary's? also why not all 1600cc?

mckinneyml

What's possible horse power out of a stock 12AT? Maximum, realiable, PSI on stock turbo?

What's required to get a 12AT in-between 300-350 hp?

PaulFitzwarryne

Straight stock is around 145hp at 6psi. With stock ports and turbo, but FMIC and 10psi then around 180hp with an upgraded fuel only ecu. With better header/exhaust possibly around 210-220hp after which you start running into turbo and injector capacity limitations.

To get to a reliable 350hp 12AT, first start with a rebuilt engine, and make the following upgrades as a minimum:-
1. medium streetport;
2. add two extra injectors, all four medium capacity- say 800/550cc [my preference is 13B plate]:
3. T04 turbo 60-1 compressor, P trim with 0.88 housing, plus add-ons such as BOV, RRR, boost controller, turbo timer etc.;
4. large sized front mounted intercooler;
5. digital fuel/ignition ecu;
6. custom header and efficient 3" exhaust;
7. deleted rats’ nest, airpump etc;
8. light steel flywheel and high pressure clutch;
9. SA style front mounted oil cooler;
10. shorter but wider radiator with extra core;
11. performance Bosch fuel pump and Pieburg pre pump, with surge tank;and
12. upgraded coils, ignition wires etc.

Once the stock two injector system has been changed to a four injector system, modification follows the same route as the 13BT but only producing 90-92% of the power.A large FMIC is essential to get safe boost.

PaulFitzwarryne

Rising rate regulator; used to increase fuel pressure/flow as turbo boost increases.

No , primaries are always smaller than secondaries.

There is a arithmetric formulae to work out best total injector capacity for a given maximum hp, usually based on .50 BSFC and 85% duty cycle adjusted according to whether its NA or turbo. You then divide by the number of injectors and estimate the required primary/secondary ratio to give effective control over the power range to get the optimal air/fuel proportions.