any of you guys read up on the 300 dollar supercharging this kid did to his FC? well i was wondering if us FB guys can use our heads and see if we can fab something up for the use of a eaton M-90 supercharger (like the ones off T-birds) with our 12a carb'd engines.

heres the link to the original kit the kid describes ... http://www.rx7club.com/showthread.php?s=&t...25&pagenumber=1

yeah, i saw that thread. i don't see why it can't be done to the fb. but the carb would have to be richened up tho. if ur putting it on a stock carb, it probably wont flow enough air that would be pumped into it. a RB holley set up for either street port or bridge port would probably work well on a stock port with that supercharger.

yea man, im all excited now, im going to get a 12a short block to rebuild, and attempt to get ported, how hard is it to port yourself ? i can take it to a local machine shop around here, then i wanna either fab up some SC mounts, or get a turbo setup, then drop it all in and take out my other 12a block and rebuild that https://www.nopistons.com/forums/pub...DIR#>/wink.png

come on mike, post something i know you want to !

i was reading the latest issue of turbo and there was an article about this guy whos selling electric superchargers. they are pretty weird, i dont remember the price but they run off 3 small car batteries.

ebay sells electric turbos, don't waste your money, the weight of 3 batteries makes up for the extra 5 hp gain you might get from them

The kid in this refferal forum is a genious. Im going to get started with a supercharger setup right now. He made me realize just how easy it is, especially with us Non-Computer 12A's. Any Input would be awesome. WE should all get started and develop something together with all our input. His setup seems pretty solid so I'll start with that. Advice on a carburator would be nice, I'd like to keep the stock one, but an upgrade might be required.



Lets do this!

You prolly wanna check out the porting and rebuilding forum then. Not as easy as it seems.

If you run draw-through like the V8 guys, you'd need a bigger carb. But if you run blow-through, the stock carb with a pressure hat might be sufficient.

Im off to the junk yard today to see if I can salvage a Supercharger. They are usually the first things to go but its monday (the day they bring in all the new cars for the vultures) so I might get lucky. I talked to a couple guys I work with and they can help me develop/weld a plate/bracket to put it on. Should be pretty awesome when its done.

alak, i think we should get something togther, if you can fab a plate then id be happy to buy one from you, your running a carb'd 12a right ?

Ya a stock 12A 4bbl. Im working with a guy at work trying to see if we can fabricate a hat/cap that will fit on top and have a fitting for a 2" inlet. Not sure on the inlet size just yet, I dont have the supercharger. Im aim-ing for a blow through setup - much like this guys setup in his FC. Only difference is Im going to have an atmospheric blow-off valve, can anyone reccommend one? Im not looking to spend much - I have to put away some cash for Toyota Supra Parts (ya, I know its not an RX-7, but what ya gonna do).





And the hunt for a supercharger begins.....

hell yea man, whatever you do , get 2 made so i can buy them man, im veryyy intrested in doing the same. get a eaton M-90 s/c off ebay, like 200 bucks.

How about a stocker from a 1st gen DSM?

ahh 1g talon , hehe the best way to go for any stock bov part haha

You know, the best blower for this sort of thing would be one off a Mazda Millenia. a) it's sized perfectly for the engine b) it's a Lysholm type, so it would be much more efficient than the Eaton.

A positive displacement supercharger (roots/lysholm) with a carb has to be a draw through setup. Otherwise you're going to need one hell of a blow off valve... (and probably use a huge amount of crankshaft HP to turn the blower at part throttle)

I don't know, draw through would be a lot harder to fab up and i don't feel like buying a new carb. I didn't know that millena's had sc ?? I think sticking with a eaton would be much more applicable...

It's really not a design choice. A blow through positive displacement won't work - you need a dynamic compressor (like a turbo) for that. Look at any car with a roots blower - all are draw through. The FC setup depicted earlier had the throttle body relocated upstream of the blower.



If you had a throttle at the blower inlet at might work, but that's going to do all sorts of wacky things with the carb (even with fuel pressure being compensated).



The millenia supercharger (on the 'S' model I think - Miller cycle engine) is more efficient that the roots type (read: cooler charge). It might be smaller too - I saw one once but don't know how large a comparable roots is. The rotors in the millenia supercharger are overdriven and spin at 21,000 and 35,000 RPM (they are different sizes) at max RPM on the V6 (this is why I think it may be smaller).

Okay, so looking through the thread, zbrown has his upstream of the throttle - see my earlier post regarding massive blow off vale and lots of wasted crank HP at part throttle... (or just a little supercharger not moving much air).

so i need to buy a holley then inorder to do this your saying

No, not really. In the first pic, the guy had relocated his TB to where it really belongs for a roots SC. Looking through the thread, I see that the other guy was actually blowing through his TB, with a blow off valve to handle the excess air. Not real efficient, but apparently it worked.

So, assuming you aren't moving huge amounts of air (ie keeping the boost sort of low), and don't mind the inefficiency, you should be able to blow through your carb.

Note that the inefficiency I am referring to deals with compressing air and then throwing it away. If the TB was upstream of the SC (where it belongs), you would be compressing less dense air at part throttle, thus not wasting power.



If you want to try this, you will need a boost compensated fuel pressure regulator like a Malpassi (this is a "return type") or a Mallory 3 port (also return type), and a fuel pump capable of supplying extra pressure, as fuel pressure required will increase with pressure in the carb hat.



Now if you could trick the blow off valve into opening at a lower pressure during part throttle, you could increase efficiency (by not making as much pressure when you don't need it).

hmm, well do you think you could get some kind of setup togther ?

Not exactly a project I'm working on (my FB's turbo'd), but I can give some hints:



1 - fuel pump and regulator (already mentioned). Fuel pressure needs to be ~3.5 psi+supercharge pressure. Note that this isn't that same as boost (manifold) pressure. You need to reference it to the pressure in the carb hat.

2 - pressure gauge to measure SC outlet pressure.

3 - serious BOV. Remember that the SC is moving max volume all the time, and you're blowing off the rest. At part throttle, pressure could get pretty severe even with the BOV screaming away. Lots of heat, engine load (read: lowered mpg because the engine is working to drive this compressor)... Also look back to #1 - fuel pressure must compensate. If the 2nd gen installation builds up 20 psi, it doesn't really matter. With a carb, you're looking at 23.5 psi fuel pressure. Besides with that much blowing into the carb, there's no telling what's going to screw up.

4 - couldn't hurt to add an oxygen sensor

5 - carb may need modification for the secondaries to work properly. Mechanical secondaries maybe?

6 - carb may need rejetting

7 - you can add an intercooler to this setup!



Also it would be useful to be able to dump the supercharged air when cruising, say by using a throttle body at the SC outlet you can open. If you're not making any pressure, there won't be alot of parasitic drag. This goes for an FC installation as well.

well i only want to run 8 lbs, now the BOV will be the same as it is in a turbo car right ? when you let off gas or change gears it will let off the excess pressure , correct ?

Let me explain the difference between a dynamic compressor and a positive displacement one.

Take a hair dryer set to cold, and put your hand over the outlet. The fan continues

to spin. This is (sort of) a dynamic compressor. Now take a bicycle pump and cap off the hose.

Try to pump it. This is a positive displacement compressor.

If you install a roots blower (positive displacement) upstream of the throttle, it will

always be gulping in air at atmospheric pressure. With the throttle closed, pressure will

build, regardless of what boost level you have designed for. This is where the blow off valve

comes in and limit the pressure. This is not the normal function of a blow off valve, which normally

acts to vent excess pressure resulting from the compressor wheel spinning too fast

(like when the throttle is closed and the turbo is cranked up to 100,000 RPM).

With a roots SC blowing through the throttle, the BOV will be singing away at virtually all

times short of full throttle. Not exactly an ideal case.

I don't know whether the guy who has this setup on his 2nd gen doesn't realize this or

simply isn't concerned.

The correct way to install a roots blower is as a draw through. Next best thing

is to have a throttle body at the blower inlet which is controlled somehow in

tandem with the throttle in the carb (this is difficult).

hm, well i see, how much total did you spend on your turbo setup ? ive been pondering doing a rebuild on a extra 12a and then setting up a turbo setup for it while its all out of the car

Not sure how much I spent - it wasn't cheap. If you want to turbocharge

on a budget, get a TII turbo and manifold, and modify the manifold to fit

a 12A. You will probably need to space it out from the engine to clear the

intake - you can use header flanges, or make a steel spacer to space the

turbo off the exhaust manifold.

You will still need a bigger fuel pump and a boost referenced regulator.

An intercooler is recommended, although a turbo will heat the intake charge

less than a roots blower will.

(and if you have an 83-85, get a real oil cooler first)

nope 81 here, ok so the TII manifold and turbo is like rougly 250. could i use the stock TII dp and stuff or would i have to custom fab all that stuff ?

You should be able to use the stock TII downpipe - the other option is to get a Racing Beat downpipe. You will still need to do a little fabrication to connect it up to you existing exhaust. I had the RB pipe years ago when I started playing with turbos and it fit the FB just fine, so I assume the stock piece would fit.

You need to drill and tap your front cover for an oil return. The front cover I used already had a boss cast into it in just the right spot - not sure if they all do. You can plumb the oil line to numerous places: one of those racing beat gauge adapters, or modify the filter pedestal, or drill and tap the front side housing.

The water fittings on the turbo are pretty optional - good for longevity, but not essential to run.

Given the age of the car, and the wimpiness of the stock fuel pump wiring, you will need to run a wire from the battery, to a fuse, to a relay located near the fuel pump. Use the stock fuel pump wire to operate the relay - all the current for the pump will come straight from the battery. Actually this mod goes for any performance setup, not just turbo. Try to find an automotive relay with the matching plug. Quick disconnect terminals fit, but tend to get loose and hot, and can actually melt the relay (been there).

Racing Beat says that street porting is beneficial to engine life - somehow the little stock ports are a problem. Plus it'll add some good power and turbo response.

Probably not 100% necessary, but if you come across a 17 mm oil pump, use it. It's really the GSL-SE pump, but I've seen it stock in '85 12A engines.

alright, i thought to my understanding that the manifold off the turbo 2 wouldnt work, but they make cheap manifolds for the 12a anyway that i can just get. Now i have the racing beat cat replacment pipe, could that be ued as a mid pipe kind of deal and i can just attach a downpipe to that replacment pipe i bought ? that would be the best deal for it.

I'm almost positive you can modify the 13B manifold for the 12A - oval the mounting holes inward, then put a 12A gasket on it to check exhaust port alignment

and grind the manifold as necessary. Again the problem you will have is that the

turbo will likely hit your intake manifold and need to be spaced either with header

flanges or a custom made spacer to space the turbo away from the exhaust

manifold (I had this problem with my 13B using other than a TII intake).

If you don't use the TII manifold, the TII downpipe may not work - it all depends

on the manifold.

You should be able to tie into your cat replacement pipe, but will need a reducer. The TII downpipe is larger than the cat pipe.