PaulFitzwarryne

NZconvertible. Sorry I suddenly remembered reading a previous post on another thread about the 12at where you gave data on your Cosmo with that motor.

NZConvertible

Not disagreeing with you, just pointing out how easy it is to get more power out of them with very little money. The stock exhaust and intake are very restrictive, and even when the turbo was stock, these mods made a huge difference. And that's without an IC or any mods to the primative EFI system!
Since any transplant would almost certainly involve the same intake and exhaust mods as I did, this is realistically what you can expect.
But for our American friends the limited availability and relatively high cost of these old motors probably makes your other options a smarter idea. You'd certainly need aftermarket engine management to go much further (you'd be unlikely to get the ECU anyway), so it would end up being a bit expensive.

PaulFitzwarryne

I think the answer to Maguire's original question is that going the 12at route would be expensive compared with a 13bt transplant. A modified 12at has potential but they are getting old and more than likely need a rebuild.

If you want to go turbo on a 12a, keep to a blow thru on a good carb, and a 13bt or custom manifold.

Having said that, just to be different I am still going to have a serious look at the 12at as NZConvertible did, or a hybrid as Adsy has done. Its illogical as it ends up more expensive than a 13bt transplant and has about 15% less power!

Maguire

iTrader: (1)

okay, so it seems to me that a bigger carb, and a blowthrough would be the best anwser to my question. Should i get a stock turbo off a fc, fd? or should i go for an after market one? Holley or weber carb. which is going to be better for the 12a turbo? what other little stuff am i going to need to make this all cometogether?

Thanks,
Shawn

PaulFitzwarryne

[QUOTE]Originally posted by Paul Fitzwarryne
[B]BACKGROUND TO FITTING A TURBO IN A SA OR FB

. The best current option is to start with a S3 12A upgrade the carby to something like a Weber or Holley, get a custom exhaust manifold and mount a S5 turbo on it Then all you need is a log style plenum and a front mount. According to REVHED you should get close to 300rwHp although 200rwHp is a more typical streetable target.

My preference is for the Weber primarily because I am used to them, my first turbo experience being some tghirty years ago with twin 45s. In reality there is little difference in performance from fitting any of the top carbs if they are jetted properly. Therefore go with your local expert's advice.

PaulFitzwarryne

[QUOTE]Originally posted by Paul Fitzwarryne
[B]BACKGROUND TO FITTING A TURBO IN A SA OR FB

. The best current option is to start with a S3 12A upgrade the carby to something like a Weber or Holley, get a custom exhaust manifold and mount a S5 turbo on it Then all you need is a log style plenum and a front mount. According to REVHED you should get close to 300rwHp although 200rwHp is a more typical streetable target.

My preference is for the Weber primarily because I am used to them, my first turbo experience being some tghirty years ago with twin 45s. In reality there is little difference in performance from fitting any of the top carbs if they are jetted properly. Therefore go with your local expert's advice.

PaulFitzwarryne

Sorry about the double post, my laptop went into a loop two hours later after a satellite drop out, and started transmitting sent messages. Unfortunately I did not pick the error up in the 30 minute time limit allowed on the Forum. If I said it twice, it must be true!

At least its not as bad as one of my friends, he sent out a rather sexy message to his girl friend but hit the ''send to all ' command There were over 200 puzzled recipients, including his wife.

peejay

No need for a bigger carb if you're goign with a blowthrough application.

Bigger carbs are good on N/As because they reduce pressure drop through the carburetor. Losing 2psi (4" of vacuum) at the top end is a big deal when you only have 14.7psi of atmospheric pressure to play with.

When you have a turbo pressurizing the air, the point is moot. You can have 10psi of pressure drop if you had a carb small enough, and you could still have enough manifold pressure to destroy the engine.

As proof, Mazdadragracing.com uses a stock Nikki (modified for proper fuel delivery) and stock intake manifold on a bridge port engine, with a BIG turbo in blowthrough configuration, and they run high 10's...

PaulFitzwarryne

Peejay- in your opinion is there a trade-off between turbo size and carb size for a blowthrough application?

I did a search on this point and got nowhere. Most of the comment I have received is that in a street situation with boost relatively low, its best to keep to a medium sized turbo with a slightly better flowing carb.

Obviously going with a Nikki has cost advantages if a big turbo gives the same or better net pressure.

peejay

As I understand it, smaller is better for turbo applications, to a point anyway. I used to follow the BLOWTHRU mailing-list and they were reporting that then they turbo'ed their 351W's they would have to remove their 850cfm Holleys and swap on 600cfm Holleys for best results. Again, as I understand it, you get much better throttle response off-boost, which means the turbos spool up faster. Under load, of course, the turbos are supplying sufficient additional pressure that it doesn't much matter that there's a larger pressure drop through the carburetor - the turbos handily make up for that.

Maguire

iTrader: (1)

what is s3? And just so you guys know. im trying trying to build the fastest car in the world like most of you guys. I just want a fast car. I want to aim for about 200-230hp. And get it the most cost effective way. Like i said. im poor. oh yeah, and if it all possible im going to get the carb first. and then add the turbo later. will that work without being a pain in the ***?

RIXSEVEN

I don't know about turbocharging a 12A. I think it should remain how it is. Mabey a new exhaust, but turbocharging it seems like it is taking away from the cars origional beauty. This is only my opinion though.

peejay

Most cost effective way to get 200-230hp is a larger street port or a bridge port, and no turbo.

On one hand you'll need to spend a few hundred bucks on a better induction system, on the other hand you'll easily spend as much buying a proper fuel pump and surge tank and regulator if you go turbo.

Maguire

iTrader: (1)

Im going to put 3" exhaust on it.

I dont really see how street porting would be cost effective. Ill spend more money rebuilding the engine than it will take to put a holley racing beat carb on it. I added up the cost for all the parts and service for street porting from mazda racing.com. the total is well over 2 grand. Plus shipping from Louisville, to california. add another $400. I dont know why i would want to do that when adding a larger carb and a turbo would still be under $1800. And about then same performance, and still decent mileage.

peejay

I paid $100 to street port my engine... $90 for gasket kit, $5 for Hylomar, and tax.

PaulFitzwarryne

A street port is cost effective:

1. if you take out and strip the engine your self, the cost is then mainly that of getting an expert do the porting; or
2. if you are already having the engine rebuilt, then the additional cost of porting is relatively minimum.

If neither of these apply, the cheapest way to performance is to go blow through. Do what Peejay posted, custom the exhaust manifold, add a big turbo and keep the stock Nikki and inlet manifold.

However a word of warning. Your 12a is most likely getting to be an old engine. Adding a turbo is going to put a lot of stress on it, so very quickly something is going to go either sigh or bang. Unless its in good condition, having a rebuild with a street port could end up being the most cost effective way.

Plus insurance companies do not like turbos being added and will really bump up your premium, or refuse to pay a claim if you dont tell them. Whose to know about porting!

PaulFitzwarryne

What is an s3?

The Gen 1 came in 3 series.
1. 1979 to Oct 80 model years 79 and 80
2. late1980 to Sept 83 model years 81, 82 and 83
3 .late 1983 onwards model years 84 and 85

All series 1 were coded as SA22C
Series 2 and 3 were coded SA22C or FB depending on the market.

There were significant differences betwwen the Series, minor differences between the year models, and occasional improvements during the year. There were also differences between export destinations, and between Japanese and export markets. I did a rough estimate at one time and came uo with about 55 different specifications fot first gen RX-7s!

Maguire

iTrader: (1)

I have an 85 with 150k. Is that too many miles for turboing this late?

Hehe, like im going to notify state farm and tell them i just turbocharged my car. hehee

Peejay, how did you only pay $100? Did you already have the parts?

PaulFitzwarryne

The cost is not doing the port, a simple grinder task if you beg borrow or steal a template.

The time and cost is taking the engine out, stripping it down, putting it back together, installing and tuning it.
Getting it down professionally is a major task and should be part of a rebuild on a 150,000 mile engine.
Look up one of the engine rebuilder sites for local cost information.

The engine you have would not be a good candidate for just adding a turbo.

Sterling

I have some questions that I hope you'll all indulge me, as they are pertainant to supercharging.

I will soon be starting a project mating an Eaton M-90 (1.5 liter, 14K redline) blower to my 85 stock 12A (70K miles).
I will be blowing thru my Yaw modded Nikki, using the best intercooler I can get, and am contemplating water injection.


Can I expect to "equal out" the stress put on my 12A from my supercharger by the addition of a pulley and seperate (small) belt mounted exactly 180* to where the blower pulley is, and set at exactly the same torque?
This seems logical to me, and if it's so, then I would design a set-up that will enable me to basically 'turnbuckle' the tension, and it will be equal on both sides.

Are there any other bearing load tricks that I can do in my application to help extend longevity; for example, bearing mods known to work or even just a good choice of lubricant. This includes the possibility of machining an extension for the front housing with an additional bearing in it. (IE, I am totally open to suggestions and ideas, but especially seek what's been proven to work.)


The boost question is relative in that I read about turbos stuffing 14 psi into these tiny engines. But this is in small spurts, if I'm not mistaken. Just how long can these engines tolerate such heat and pressure? What is the highest boost an unmodified US stock 12A (85) can handle at high RPMs all day long...with a turbo?...With a supercharger?
(This is already assuming timing is at it's optimum for it, the bestest-ever intercooler...ideal set-ups.)

Also, how do these figures change with things like water injection?

Thank you, and I hope I have'nt impeded the discussion too much with my blower questions.

Sterling

Directfreak

iTrader: (2)

Sounds logical - Is there any way you could use an exisiting pulley area? Like the previous location of the Air Pump or the A/C = so you won't have to fabricate such a mount. Mazda probably worked out the bearing tension with those two pieces mounted on relatively opposite sides. Check how Atkins rotaries mounts theirs, maybe they got something else worked out that we haven't thought of.

Since you're doing a blow-thru application, with an intercooler, you could put the Supercharger where the A/C previously went and route the forced inducted air into the nikki with a little "turbo" bonnet to pressurize it.
It would look very similar to a Turbo in this regard.

Obviously, this would not work with a draw-through system.


To run 14PSI all day on a stock (high compression) 12A motor will probably not be wise. YES, there are people who run 22lbs+ all day on 12A's here in Miami, on daily driven cars. Those that I know of were rebuilt engines (not tired) andare using a more sofisticated method of fuel injection.

For you to run such high boost on a blow through turbo/supercharger, - you will have to run a significantly high amount of fuel (rich) and timing retard. Since you don't really have anything to retard your timing when under boost, the car will have to be set for correct timing under boost only. Which means that off boost it will run like ****, and your EGT's will probably be high during day to day driving.

If you run lower boost - like no more than 6 to 8 lbs, I believe you will be suprised at how much power that little 12A can put out - especially if intercooled well. At 8 lbs of boost with a 13BTurbo on the 12A, you could easily be at 225 hp. That's quite alot for a first gen, over 200% more power than stock will really wake up performance. A similarly setup supercharger should yield similar perfomance.

The small spurts of boost are designed to be no more than 15 seconds at a time for turbocharger applications, according to Corky Bell. A supercharger, would probably be putting out more heat all day beacause of it's continuous boost. So on a motor constantly seeing boost, you probably will have a shorter lifespan, - just like on Third Gen's with the Twins. You can drive a single-turbo car all day without ever getting into boost if you drive it right.

Water injection is a tool used to run higher boost, and reduce the risk of detonation. Several of the big Turbo guys swear by them (Rice Racing /500 hp) on their applications. Basically a fine mist of water mixed with (damn, I forgot) could be used to be injected into the fuel mixture when under boost, via a (boost) pressure switch. The system appears to work, however you do need to keep a large container in the car full of this stuff, and hope you don't run out of it while under boost.
Since you tune your car for water injection (higher boost/reduced detonation risk), if you run out of it in the middle of a boosted run, it would be like leaning out under boost - NOT GOOD.

For This reason alone, I am not even considering a water injection system. Besides, that is for serious horsepower. Good tuning could make up a lot of the benefits earned by such a system in the first place.


No problem, hope I helped in some small way.

Sterling

Now...
Unfortunately, the Eaton is a pig compared to the 12A, and there's simply no room for it except on top. I will have to relocate the alternator to where the AC pump was.
Fabbing a special pulley-plus-idler pulley deal does'nt bother me too much. I think it does make alot of sense, but I'll research it more.

Remember, I'll be utilizing the bypass valve that comes on the Eaton. (Neat) Apparently it {the bypass dashpot) reads manifold vacuum, and opens the bypass while cruising. Howeever, with my need to tinker as well as be a controll freak, I will figure out a way to remotely bypass the pypass! IE, from inside the car, I will be able to turn the blower on "all the time", "only during acceleration" or "completely bypassed".

As far as the water injection, I will go ahead and build my manifold with tapped places for the H2O injectors, and we'll see. I think that it won't be such a problem to run out of water. I can utilize the float switch from a window washer resevoir, and hook it up to the electric solenoid that is on the bypass dashpot, if need be. I can also hook it up to the "Seatbelt" light switch. (Damn thing don't work right anywayz...Always coming on for no reason!)

So there are ways to ensure you don't blow things up.

I think I will shoot for 10 psi first, and work on getting that as cold as possible by trying different ICs. I would like to see 8psi of cool air out the other side.

According to Eaton, Magnuson, and Magnacharger, the Eatons only use 1/3rd on one HP when the bypass is open.
My application with the M-90 will draw about 50 +/- 5 HP from the engine under hi RPM boost.

It really not too bad as far as roots blowers go.
Thanks again for the info.
I do have more Qs, but a lightening storm is a comin'!!!

zaridar

iTrader: (3)

Whats the max boost you would want to run on a 12a with race apex seals?