Where can i find a turbocharger for a 12a?
07-18-02, 12:36 AM
#1
Where can i find a turbocharger for a 12a?
I know that they used to make them for the japanese model. And my step-brother saw one on ebay, but it was over before i could bid on it. Are there anyplaces i could order one from? and is it a pain in the ***?
Thanks,
Shawn
Thanks,
Shawn
07-18-02, 05:02 AM
#2
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BACKGROUND TO FITTING A TURBO IN A SA OR FB
There are several options to having a turbo charged engine stating with the Jspec 12at.
The 12at was designed in 1980-81 as the first turbo charged and EFI rotary engine. It retained the four port induction system of the pre1981. The concept was to provide more power in the low-mid range for vehicles like the Cosmo and Luce. The engine was not designed as a high revving sports car motor, although some 400 RX-7s equipped with it were sold in Japan during 1984-5 when sales were lagging.
The 12at engine and gearbox were somewhat over-engineered and so can handle more hard treatment than the later13bt. Its output is in the range 135-140 hp, while the Hitachi's HT18S-BM turbo gives a maximum 6.2lb boost with power coming in at 1500rpm, declining from just over 6000rpm. It came with a stronger clutch and drive train with a more overdrive .791 fifth gear. The compression was 8.5-1 compared with the 12a of 9.4-1.
The 12at was not designed for serious performance, thus the ports and turbo are small. The analogue fuel injection control unit was made by Nippon Denso and is linked to a Mitsubishi Electric digital emission control computer, but there is no control of the ignition. Fuel input is by 2 x 800cc injectors. There is no intercooler which helps with limiting turbo lag due to the short distance. Apart from some early engines, there was a good electronic boost linked dizzy.
CHANGING TO A 12at
The 12at was a great street engine for its time, and along with the strong tranny easily bolts straight into a previously 12a engined RX. About the only real change needed is adding an EFI fuel pump, such as a Hi Flow Bosch, and high pressure fuel lines. Its performance in stock form will be slightly better than a 13b gsl se. At 355lbs, there is also about a 25lb weight saving.
MODIFYING A 12at
Many people have tried modifying a 12at or adding a turbo to a 12a. One problem in evaluating their success is the lack of comparable dyno information and mixtures of din, SAE JIS etc. What follows is based on various sources including trying to make sense of contradictions and outputs measured in different ways.
The first step is replacing the stock 12a exhaust system and some of the emission equipment. This should give another 15-20hp
The first serious modification is adding a larger turbo. You can run the 12at Hitachi HT18S-BM turbo, with a 13bt compressor wheel & cover. At 12PSI it will give you about 210rwHp nearing the limit of the stock EFI. It is best to use a S5 turbo, which is equivalent to a small T04/large T03.
Add an intercooler. The stock manifold will need replacing, then you can install a front mounted intercooler from a Gen 2. If you want serious power then you can weld two stock ICs together. This gives about 225rwHp
Replace the analogue computer and knock control. The 12at works well with any recent injection computer system such as Haltech, MicroTech, Wolf or SDS, while some good fuel maps are available.
It is possible to use the entire induction and EFI system from an S5. The intake manifold will need an adaptor plate, and the exhaust manifold will need to be custom built. With all mods at 12PSI boost you will be getting a reliable +300rwHp on a street car.
If the budget allows, a further option is you can add water injection.
Presumably the engine is being rebuilt so take the opportunity for some porting. A 12a spec streetport would be a substantial improvement. Unfortunately, data on the12at is very, very limited so looking at 13b date would be useful. But as Peejay has said on another thread, you can never have too large a port on a turbo!
HYBRID MODIFICATION
Due to the difficulty of obtaining good 12at parts, a great way to go is a hybrid engine modification using a mixture of 12a, 12at and 13b parts. Using 12at low compression rotors, 12a components with their bigger inlet/exhaust ports and inlet, and 13b centreplate for the fuel injector bungs. The counterweights should be from the 12at or you will need to balance the rotating assembly.
One person who has successfully used this approach is Adsy01.
ADDING A TURBO TO A 12A
The most complex modification would be to follow all the above steps but just use 12a and 13b parts. The main change is to use 12a rotors and counterweights. The question is really why go down this track unless you are totally allergic to the 13bt?
A simple solution frequently tried in the past is to add a bolt-on turbo system to a 12a. Many earlier tuners, like Elford, Pacific Turbo and TWR, produced bolt-on kits. Unfortunately they are no longer in production so custom made systems are the only way to go. 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.
WHICH OPTION FOR YOU
The 12at is a great 1980s engine and represents a turning point in rotary history. But be warned, the engines are generally worn and not cheap. The need for a full rebuild is to be expected. Whether you want to go down that track is a personal choice of whether you want to stick with the Gen 1 or go retro with a modern engine in a lightweight classic body. Going down the genuine12at road is an expensive journey, a bolt-on turbo is the cheapest, mid way is to copy Mike P29 or AJC 13b and use a Cosmo Jspec 13bt with updated electronics and turbo.
Good luck, you will need timr and money
There are several options to having a turbo charged engine stating with the Jspec 12at.
The 12at was designed in 1980-81 as the first turbo charged and EFI rotary engine. It retained the four port induction system of the pre1981. The concept was to provide more power in the low-mid range for vehicles like the Cosmo and Luce. The engine was not designed as a high revving sports car motor, although some 400 RX-7s equipped with it were sold in Japan during 1984-5 when sales were lagging.
The 12at engine and gearbox were somewhat over-engineered and so can handle more hard treatment than the later13bt. Its output is in the range 135-140 hp, while the Hitachi's HT18S-BM turbo gives a maximum 6.2lb boost with power coming in at 1500rpm, declining from just over 6000rpm. It came with a stronger clutch and drive train with a more overdrive .791 fifth gear. The compression was 8.5-1 compared with the 12a of 9.4-1.
The 12at was not designed for serious performance, thus the ports and turbo are small. The analogue fuel injection control unit was made by Nippon Denso and is linked to a Mitsubishi Electric digital emission control computer, but there is no control of the ignition. Fuel input is by 2 x 800cc injectors. There is no intercooler which helps with limiting turbo lag due to the short distance. Apart from some early engines, there was a good electronic boost linked dizzy.
CHANGING TO A 12at
The 12at was a great street engine for its time, and along with the strong tranny easily bolts straight into a previously 12a engined RX. About the only real change needed is adding an EFI fuel pump, such as a Hi Flow Bosch, and high pressure fuel lines. Its performance in stock form will be slightly better than a 13b gsl se. At 355lbs, there is also about a 25lb weight saving.
MODIFYING A 12at
Many people have tried modifying a 12at or adding a turbo to a 12a. One problem in evaluating their success is the lack of comparable dyno information and mixtures of din, SAE JIS etc. What follows is based on various sources including trying to make sense of contradictions and outputs measured in different ways.
The first step is replacing the stock 12a exhaust system and some of the emission equipment. This should give another 15-20hp
The first serious modification is adding a larger turbo. You can run the 12at Hitachi HT18S-BM turbo, with a 13bt compressor wheel & cover. At 12PSI it will give you about 210rwHp nearing the limit of the stock EFI. It is best to use a S5 turbo, which is equivalent to a small T04/large T03.
Add an intercooler. The stock manifold will need replacing, then you can install a front mounted intercooler from a Gen 2. If you want serious power then you can weld two stock ICs together. This gives about 225rwHp
Replace the analogue computer and knock control. The 12at works well with any recent injection computer system such as Haltech, MicroTech, Wolf or SDS, while some good fuel maps are available.
It is possible to use the entire induction and EFI system from an S5. The intake manifold will need an adaptor plate, and the exhaust manifold will need to be custom built. With all mods at 12PSI boost you will be getting a reliable +300rwHp on a street car.
If the budget allows, a further option is you can add water injection.
Presumably the engine is being rebuilt so take the opportunity for some porting. A 12a spec streetport would be a substantial improvement. Unfortunately, data on the12at is very, very limited so looking at 13b date would be useful. But as Peejay has said on another thread, you can never have too large a port on a turbo!
HYBRID MODIFICATION
Due to the difficulty of obtaining good 12at parts, a great way to go is a hybrid engine modification using a mixture of 12a, 12at and 13b parts. Using 12at low compression rotors, 12a components with their bigger inlet/exhaust ports and inlet, and 13b centreplate for the fuel injector bungs. The counterweights should be from the 12at or you will need to balance the rotating assembly.
One person who has successfully used this approach is Adsy01.
ADDING A TURBO TO A 12A
The most complex modification would be to follow all the above steps but just use 12a and 13b parts. The main change is to use 12a rotors and counterweights. The question is really why go down this track unless you are totally allergic to the 13bt?
A simple solution frequently tried in the past is to add a bolt-on turbo system to a 12a. Many earlier tuners, like Elford, Pacific Turbo and TWR, produced bolt-on kits. Unfortunately they are no longer in production so custom made systems are the only way to go. 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.
WHICH OPTION FOR YOU
The 12at is a great 1980s engine and represents a turning point in rotary history. But be warned, the engines are generally worn and not cheap. The need for a full rebuild is to be expected. Whether you want to go down that track is a personal choice of whether you want to stick with the Gen 1 or go retro with a modern engine in a lightweight classic body. Going down the genuine12at road is an expensive journey, a bolt-on turbo is the cheapest, mid way is to copy Mike P29 or AJC 13b and use a Cosmo Jspec 13bt with updated electronics and turbo.
Good luck, you will need timr and money
07-18-02, 05:15 AM
#3
Old [Sch|F]ool
Finding a turbo for a 12A = How good are you at reading compressor maps? 
The stock 12AT turbo was really small and designed for smooth seamless operation, after all the 12AT was designed for luxury cars and not the RX-7. You can get more power from a street ported 12A than you can from the stock 12AT.
I'd go with something designed for a 13B, which would raise the RPM range a bit. The stock turbo from a T2 should be about right. (In fact I'm told that T2 turbos are a good upgrade for 12ATs) You should be able to oval the bolt hole of a 13BT exhaust manifold to fit it to a 12A. They just need to go 5mm inboard. There shouldn't even be any port mismatch since the manifold exhaust holes are so much larger than the exit holes in the engine, and if they don't match just do a little more grinding.
Interesting trivia - All '84-85 engines, GSL-SE and 12A, have the boss on the front cover below the OMP for the turbo oil return line. I verified this on my '85 GSL - the boss is definitely there.
The stock 12AT turbo was really small and designed for smooth seamless operation, after all the 12AT was designed for luxury cars and not the RX-7. You can get more power from a street ported 12A than you can from the stock 12AT.I'd go with something designed for a 13B, which would raise the RPM range a bit. The stock turbo from a T2 should be about right. (In fact I'm told that T2 turbos are a good upgrade for 12ATs) You should be able to oval the bolt hole of a 13BT exhaust manifold to fit it to a 12A. They just need to go 5mm inboard. There shouldn't even be any port mismatch since the manifold exhaust holes are so much larger than the exit holes in the engine, and if they don't match just do a little more grinding.
Interesting trivia - All '84-85 engines, GSL-SE and 12A, have the boss on the front cover below the OMP for the turbo oil return line. I verified this on my '85 GSL - the boss is definitely there.
Last edited by peejay; 07-18-02 at 05:17 AM.
07-18-02, 06:25 AM
#5
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Peejay, can you use the 13bt manifold on the 12a NA engine? If so it would be a great saving on a blow thru system as the quotes for a custom set-up are very high.
07-18-02, 07:25 AM
#6
Old [Sch|F]ool
Well, I know of people that do mount 13B manifolds and headers on 12As by ovalling the bolt holes. I won't argue with what people are already doing. 
The only thing that worries me is if the assembly will clear the intake manifold. It might be necessary to space the exhaust manifold out a bit. Before I physically have parts in my hand, I can't comment on that, other than the T2 turbo/manifold will not clear the 13B 6-port intake manifold.
Besides, if I was gonna go turbo, I'd make my own turbo header and mount something a bit uncommon on the top.
The only thing that worries me is if the assembly will clear the intake manifold. It might be necessary to space the exhaust manifold out a bit. Before I physically have parts in my hand, I can't comment on that, other than the T2 turbo/manifold will not clear the 13B 6-port intake manifold.Besides, if I was gonna go turbo, I'd make my own turbo header and mount something a bit uncommon on the top.
Trending Topics
07-18-02, 06:55 PM
#8
Old [Sch|F]ool
You need to do mods to the carb to work right with blowthrough operation. Turbo doesn't care.
Drawthrough requires special turbo seals to withstand vacuum, and even more carb mods than blowthrough.
Drawthrough requires special turbo seals to withstand vacuum, and even more carb mods than blowthrough.
07-18-02, 08:54 PM
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Peejay: I agree that the stock 12at is not powerful engine when compared with a streetported 12a. I think people were confused by the 160JIS figure which is nearly 20% higher than SAE.
However, the 12at has potential with reworking the ports and turbo. Thus, to change to a reasonable engine you are looking at the import cost, plus a rebuild, plus modifications. The total is looking like the price for two good gsl-se's!
However, the 12at has potential with reworking the ports and turbo. Thus, to change to a reasonable engine you are looking at the import cost, plus a rebuild, plus modifications. The total is looking like the price for two good gsl-se's!
07-19-02, 11:36 AM
#12
standard combustion
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If you really need a turbo car, just buy the racing beat 12a chassis convert to 13b engine mount and buy a Jspec S5 engine with its ECU and wiring harness, GSL-SE front cover, alter your hood and slightly modify the exhuast and you will have a turbo car in the best route arguablly for the cheapest effective price.
07-19-02, 11:51 AM
#13
Originally posted by WackyRotary
If you really need a turbo car, just buy the racing beat 12a chassis convert to 13b engine mount and buy a Jspec S5 engine with its ECU and wiring harness, GSL-SE front cover, alter your hood and slightly modify the exhuast and you will have a turbo car in the best route arguablly for the cheapest effective price.
If you really need a turbo car, just buy the racing beat 12a chassis convert to 13b engine mount and buy a Jspec S5 engine with its ECU and wiring harness, GSL-SE front cover, alter your hood and slightly modify the exhuast and you will have a turbo car in the best route arguablly for the cheapest effective price.
Truly quick and cheap:
Stock 12A, Blow Through Holley setup - Less than 1500 bucks. 220 HP.
07-19-02, 01:37 PM
#14
Thanks for all the help. Here basically my story. i have a 12a gs. I want to streetport it someday wheni have the money, but im on a very limited budget. Doing a 12bt swap would be sweet, but it wouldnt be any cheaper than the street port, and would be a way bigger pain in the ***. Im not really prepaired for any engine swaps here. this is my only car. The reason i asked about the turbo is because i thought if it was possbile that it might be a good inbetween. Although, if a holley carb when be bigger bang for the buck, maybe i could go that route.
Direct Freak: The blowthrough Holley setup you mentioned. Where could i find some more info on that?
Again, thanks for all your anwsers, im stil new on all of this.
Direct Freak: The blowthrough Holley setup you mentioned. Where could i find some more info on that?
Again, thanks for all your anwsers, im stil new on all of this.
07-19-02, 07:38 PM
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Blowthrough means the turbo feeds into the carb as distinct from 'suck through' when the turbo is after the carb. The main problem with the latter is air/fuel mix goes into the turbo with a potential disaster if there is a backfire.
07-19-02, 08:35 PM
#17
35r 13b first gen
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As Mcguire asked earlier where can you purchase a turbocharger.
Also what is the difference between a supercharger and a turbocharger?
Where can you find a supercharger
?
Thanks
Also what is the difference between a supercharger and a turbocharger?
Where can you find a supercharger
?
Thanks
07-19-02, 10:01 PM
#18
Originally posted by Maguire
The reason i asked about the turbo is because i thought if it was possbile that it might be a good inbetween. Although, if a holley carb when be bigger bang for the buck, maybe i could go that route.
Direct Freak: The blowthrough Holley setup you mentioned. Where could i find some more info on that?
The reason i asked about the turbo is because i thought if it was possbile that it might be a good inbetween. Although, if a holley carb when be bigger bang for the buck, maybe i could go that route.
Direct Freak: The blowthrough Holley setup you mentioned. Where could i find some more info on that?
In the Links there is a yahoo group for TurboFB's, a Yahoo Group for Blow-Through turbo systems. Two great resources for Turbos and Turbocharged first Gen RX-7's.
A Holley 4 Barrel carb is an excellent carburator for a Blow through Turbo system on a rotary.
A stock 13B Turbo and exhaust manifold (out of a junkyard) will provide plenty of get-up and go for a stock port 12A.
Honestly, even though it is relatively simple, it is not a project for a newbie. I suggest you read up on how Turbochargers work first (including books), after spending lots of time on the forum reading and searching. Chances are 99% of your questions have been previously answered somewhere on this main forum.
Oh, and a little etiquette, do not post on a really old thread, thus bringing it back to life. It brings down current threads to no-man's land.
Good Luck.
07-20-02, 01:57 AM
#21
Originally posted by Paul Fitzwarryne
Directfreak. Do you have the links for the Yahoo groups?
Thanks
Directfreak. Do you have the links for the Yahoo groups?
Thanks
TURBO FB
TURBO FB Database
BLOW THROUGH
DRAW THROUGH
07-21-02, 06:37 PM
#22
Awesome guys, thanks for all your help. Okay, so lets say i get the Holley carb, the turbo off a 13b and the manifold. And it should work? About the carb. What model? Should i get the one from racing beat or is there a more cost effective solution? Also when i put on the new carb and turbo. Should i add headers or is the stock down pipe enough?
07-23-02, 05:51 PM
#23
RicanRider
Have you checked out Mazdaracing's options for a 12A turbo? www.mazdaracing.com
Originally posted by Maguire
Awesome guys, thanks for all your help. Okay, so lets say i get the Holley carb, the turbo off a 13b and the manifold. And it should work? About the carb. What model? Should i get the one from racing beat or is there a more cost effective solution? Also when i put on the new carb and turbo. Should i add headers or is the stock down pipe enough?
Awesome guys, thanks for all your help. Okay, so lets say i get the Holley carb, the turbo off a 13b and the manifold. And it should work? About the carb. What model? Should i get the one from racing beat or is there a more cost effective solution? Also when i put on the new carb and turbo. Should i add headers or is the stock down pipe enough?
07-23-02, 10:03 PM
#24
I'm a boost creep...
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Originally posted by Paul Fitzwarryne
The engine was not designed as a high revving sports car motor...
The engine was not designed as a high revving sports car motor...
I agree that the stock 12at is not powerful engine when compared with a streetported 12a.
07-24-02, 12:31 AM
#25
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NZ Convertible. I am not certain whether you are agreeing or disagreeing with me. The main point I was making was the stock 12at is limited so just dropping it in will have a dramatic impact , only about 115 rwHp. So if you are going down this track budget for some major modifications. This is to contrast withthe 13bt which is aimed at performance in stock form.
First, the stock 12at power curve drops off at about 6300rpm because of limitations in design, Obviously if you get rid of one of the major limitations, the size of the turbo, as you have done the powercurve changes and the engine will rev higher.
Second, the wording I used was "stock'. A better exhaust, effective intake and bigger turbo is a significant modification
If you read my post under the section headed 'modifying a 12at' I deal with the type of modifications you have on your vehicle and give 210rwHp plus 15 more for an intercooler. these line up with your experience. A question that interests me is whether you have hit the limitation of the stock ECU at that point.
A point of interest, you have a 88 FC convertible which comes with a 13b as stock, why did you go for the 12at or was this in a previous car? Going 12at was a fashion in NZ on earlier RXs according to one of my sheep loving friends!
First, the stock 12at power curve drops off at about 6300rpm because of limitations in design, Obviously if you get rid of one of the major limitations, the size of the turbo, as you have done the powercurve changes and the engine will rev higher.
Second, the wording I used was "stock'. A better exhaust, effective intake and bigger turbo is a significant modification
If you read my post under the section headed 'modifying a 12at' I deal with the type of modifications you have on your vehicle and give 210rwHp plus 15 more for an intercooler. these line up with your experience. A question that interests me is whether you have hit the limitation of the stock ECU at that point.
A point of interest, you have a 88 FC convertible which comes with a 13b as stock, why did you go for the 12at or was this in a previous car? Going 12at was a fashion in NZ on earlier RXs according to one of my sheep loving friends!