i am making a turbo setup for my 12a. i have a turbo off
a late moble 300zx twinturbo. This should work well.
i can make an exhaust manifold. i am unsure about blow-through and draw-through setups any help would be welcome. it will be cardurated. was thinking about a
older datson 240 side draft carb?

 

The only Draw through setup I know of is a 12A Elford turbo but that uses a SU carb...

I'm helping with a 12A turbo project, and we decided to go for blow thru on that one. Going to use a Weber Sidedraft for this project.

Good luck

 

I have a 12a turbo blow through setup done by rotaryshack (aka 680rwhp). Havent got the engine in yet, but if youre going with a 4 barrell nikki, it will need some modifications. I believe if you use a side draft webber, they require no modifications. You will also need a new intake mani if youre shooting for a blow through. You also need a front cover with an oil return. This project is not for the feint of heart...... especially when it comes to drilling holes in your block



Peace

 

Had experience with the Elford set up when they first came out 20 years ago, masses of turbo lag and very difficult to set up right. Knowledge has come a long way in 20 years on turbos!

Would not recommend going the twin turbo route as getting the right balance is a problem. OK in theory and with lots of research, but why do you think many people are going back to the single turbo set-uo?

 

The 300ZX Turbos are VERY small. They will not flow enough for a 12A, even stock port. Remember, a Rotary is a big air-pump and will out flow that little turbo designed for 1.5 Litres of Piston engine (half of the 3 liter 300Z engine)

Don't reinvent the wheel, use a healthy stock 13BT manifold and Turbo, and you'll be good for 250-300 rwhp.

I recommend a Webber sidedraft or a Holly 650 (in that order) for a blow-through setup.

There's some guys on the board that can offer you a whole "kit", so keep looking around.

 

What if you treated each housing as a separate "engine" with its own little turbo? I, too, have come into possession of 300ZX turbos and was wondering if they could keep up with a rotary. I was thinking one, but DF just saved me....

 

What if everytime you decided to go to your kitchen from your bedroom, you walked out the back door, ran around the house a couple of times, and then walked back in, through every other room and then finally to the kitchen?

Seems like a lot of work to go just to the kitchen doesn't it?

Mario - again, don't reinvent the wheel. Just use a 13BT and manifold. It was made just for that.

If you want a custom manifold for a 12A, or a custom manifold just for the use of a bigger turbo/external wastegate - I can get them for $350 plus shipping - custom made for your application.

 

i know im goign to get proved wrong. but df, you said use a 13bt manifold with a 12a block.. they dont line up do they? i know 12a headers dont work with 13b engines and so on.. please explain...

 

You simply have to oval out the moutning holes, weld on a 12A exhaust flange to the 13B maifold with the ears cut off, or, just make a custom adapter.

~T.J.

 

diagrams/pictures? im interested for knowledge reasons.

 

moremazda did this, search for him and you see. maibe PM him and he probably give you pics

 

if i do a blow through setup what do i have to do with the carb? i know about a rising rate fuel pressure regulator. do you have to box the entire carb up to keep the boost from blowing back through the carb?
i can fabricate my own manifold to bolt to any turbo flange. if the 300zx turbo is not big enough what should i use. i was thinking about a t-3 but they have so much lag. i like the small turbo for its quick response.
i am not going to build a 300hp monster. i just want have some fun on my way to work every day.

 

12A Turbo Write Up.

 

i have done tons of 12a turbos!!! do not do draw-through!!! it only works good on alcohol cars,you cant intercool it , blow-through you can!

directfreak is right , the nissan turbo is too small for the rotary engine....get a 13b turbo/manifold and slot the holes, it works great and there cheap!blow through a weber or a nikki, it will be fast!

 

i just read that whole thread! its a good write up. i would like to do that with my motor, but i dotn want to throw out the s5 13b n/a idea. i would like to know the amount of money to do this..


680.. could you give an appox. cost of this? is a t3 too big for a streetported 12a? what kind of numbers (besides the 680rwhp) have you put down with customers and yourself with a blow threw setup?

 

i just posted some dyno results on a customers daily driver, blow through 13b... we were impressed with the power it made, considering the motor was stock!

223rwhp
and 214 torque!

 

Everyone told me a T3 was too small even for a stock port? That and I thought T3 was jus the bolt pattern designation because you can get the turbos in all kinds of sizes...I could be way wrong though. Maybe T3 is that flange type/size AND the turbo design?

~T.J.

EDIT: Heres the thread where everyone said they were too small: https://www.rx7club.com/forum/showth...hreadid=116271

 

from: https://www.rx7club.com/forum/showth...hreadid=155969
what is your stand on intercoolers jeez

draw through doesnt work well? what about the bae turbo kits and corvairs to start with...

 

Woah there cowboy...He didnt say that he HAD to intercool his car...He just stated that with a blow through it opens the option. We all know that its not MANDITORY to intercool a turbo car (stock 12AT), but it does help a little if it in the budget, and with that car he built, it wasnt. Also, he didnt say that the draw through didnt work well, he only said it works well on alcohol cars (whether thats true I dont know). That, and just because everyone (BAE and the Corvair) is doing it doesnt mean its the best way to do it. Go search the forum and see how many people use draw through setups...I think its fairly well known that draw throughs just dont work as well as a blow through. Sorry if I sound like Im attacking you, but it sounds like youre attacking him for no real reason .

~T.J.

 

im saying this dude needs to pick a side on intercooling, not mean not attacking, but it seems like hes against em, then wham no cant go draw through cause you cant use one. yes i know ic isnt mandatory, i didnt say it was.

he said "only works good on alcohol cars" as in only those and not pump gas users like me. i pointed to 2 obvious draw through setups. nobody here runs them but that doesnt mean that they arent great, search more than this forum and you will find some

go search the forum? bah what do you think i've been doing. thats why im questioning 680's flip floppin standpoint on ic's.

not attacking him for no real reason, not attackin him at all. the rotary shack ordeal is over as far as i know....

gamble

 

Here are the negatives of a draw through turbo system:

Draw through turbo systems are old technology whos time has come and gone. Since the carb sits in front of the turbo there is no way to effectively intercool it. Not saying its impossible but very difficult. You wouldn't want fuel going through your intercooler would you? There are two really big concerns with these systems though. If the outside temperature is below about 70 degrees or so, the carb may actually ice over. You may wonder how this is possible when it is so warm outside. The carb stays relatively cold when the turbo is sucking air through it that fast. This is good for the lack of heat through the carb but the increase in air speed freezes the fuel on occasion. You might drive it hard and then stop at a light or turn the car off. The fuel may freeze in the carb for a short time. If you live here in Houston and drive your car only in the summer (about 9 months of the year here!) then you will probably be OK. The Corvair and similar systems used a coolant passage through the carb to heat up the carb to prevent this from happening. This also heated up the incoming air. Why the hell would you want to introduce more heat to a turbo system? The draw through systems also suffer from increased lag and are harder to start. Not only are you trying to send fuel down the intake manifold, but you are also hoping that enough fuel makes it through the not spinning yet compressor blades on its way to the engine. If you think a rotary floods easily now, wait until theres a turbo behind the carb! The last BIG problem with the draw through system is that unless your turbo was specifically designed for this application by being built with carbon seals, it will self destruct. Your average turbo is not designed for this and fuel will eat away at the turbo seals destroying it. I don't know of any stock turbos on modern cars that have the carbon seals. Turbonetics offers most of their turbos with the carbon seal option though if someone still needs to do this. A carb is a restriction. Even more so in front of the turbo. Since it is a venturi it relies on an air restriction to function properly. Generally a carb will flow about 10% less air than an equivalent sized throttlebody. A restriction has a greater effect in front of a turbo than behind. I hate arguing about this point so heres why. It is true that the same amount of air will pass through the front of a turbo as it will behind it. This is simple physics. What you put in you have to get out somewhere. The thing that most people don't realize is that the air is going slower after it leaves the turbo! The reason is that the turbo has compressed the air. The only way to compress it is to slow it down. The same restriction after the turbo will be effectively less. Even though there is the same total volume of air it is now compressed into a smaller package and moving slower through the carb. Get that carb off the front of the turbo and put it where it belongs!

Here are the good things about a draw through system:

You don't need a blow off valve. When you close the throttle plate there is no place for air to back up in front of the throttle plate since there is no pressure there. It is simple. More or less the same thing as using a roots style blower under a carb except with a turbo. You won't need to raise your fuel pressure. Still works under a vacuum. Just change the jetting. Damn this was a much shorter list than all the negatives!

I hope this helps add some info about draw through systems. They can be made to work but they will never work as good as a blow through system.

 

May I suggest that you guys pick up a few Corky Bell books and spend the cold weekend studying up?

There have been a few VERY good points made in this post (thanks, Rotarygod), and a few umm.... "misled" folks who are obviously regurgitating what they have misinterpreted off this and other forums.

I don't want to get too heavily involved with this thread, but I will state my point on one aspect of custom turbocharger kit design. I would not try to push down more than .5 bar on a (daily driven) rotary without some sort of intercooling, period. EVER. The danger of detonation is too great, and with no fuse to blow before the motor does (ie - head gaskets on a piston motor will blow before the rings 3/4 of the time), I simply wouldn't risk it. Of course, that could also be due to the fact that I live in central Texas, and drive my vehicles very hard, and don't like to have to worry about reliability.

I am helping Gamble to set up his turbo 12A, and using an intercooler on his system is a given. Yes, it makes the plumbing slightly more difficult, but the intercooler itself is cheap, and easy to mount. With goals of ~250 RWHP initially, we never even thought twice about the IC issue.

EVEN THEN, we may add water/alcohol injection at some point to determine how much it helps...

Other cars I am working on:

Del Sol 1.5L (under 500 dollar budget) - no IC is needed, since we will be running .5 bar at the max through a small, somewhat efficient IHI turbo. System also utilizes an FMU and piggyback fuel pump to lower costs. This is a daily driven/autox car, so a nice bump in HP across the useable band is all that is needed. Fuel economy is important, and should be reduced by less than 10% at most.

240SX 2.4L (under 1000 dollar budget) - a nicely polished Starion IC was found for 50 bucks, and since goals of 10-12 psi (on race gas) for 230-240 RWHP and high 13 second time slips were needed, so was the IC. Larger injectors, S-AFC, big fuel pump, and expensive custom manifold for the T3 make this kit a little more expensive, but it will be a very, very nice alternative to SR20DET, CA18DET, and RB swaps. Once the motor is rebuilt with forged pistons and rods, goals of 350 RWHP will be attainable with a relatively cheap turbo (~600 dollars extra). This kit has been budget-designed with long-term goals in mind.