RX744CSP

iTrader: (4)

I'm not so much concerned with the exhaust side of the turbo plumbing as I am the intake side. Many moons ago, I rode a Kawaski turbo bike, it was the first year with the turbo at the rear of the engine, just below the swing arm pivot. It had turbo lag from hell; a combination of long exhaust tubes and long intake plumbing between the turbo and the blow through carbs. It takes time to get air to speed up, and the longer the tube the longer the lag.

If I were building the intake for this particular swap, (using FI stuff, a carb would be a bitch to set up), I'd make the intake and exhaust manifolds as close together as possible, put the injectors very close to the ports, and put the air door/throttle body on the intake side of the turbo. The intercooler would be between the air filter and the throttle body ( I realize this isn't optimal placement).

I keep coming back to a supercharger as a much simpler setup. Those 3800 Buick superchargers are pretty common, too.

xrotaryguy

Thats a neat idea with having the throttle body before the turbo. It would reduce the need for a blow off valve. But it would be sooooo far away from the combustion chamber. There would be lots of room for air pressure to bounce back and forth in the intake runner. What would your map sensor think of that? I think that having the throttle body closer to the factory location would be better.

In keeping with tradition... I will again state that a super charger is simpler. Why arent we using them again?

jic

iTrader: (1)

simple and clean

Slo Motorsports

All of this is really cool. I have a 75 Spit with a blown engine that I hoped my son and I would rebuild. Instead he took it all apart and abandoned it for some other cool toys (the Supra and T2). He did also buy a 1986 FC (13BNA) GXL for a dollar. The engine runs but the car is toast. In reading your forum I'm thinking yank the engine, tranny, LSD and convert the Spitfire to a rotary rocket. Will a 13B fit?

RX744CSP

iTrader: (4)

Yep,a 13B is only 20mm (about 3/4 inch) longer than a 12A. You also have all the electronics etc for an FI car.

Like RXMidget says, though, you'll have to convert the engine to a 'front mount' like a 12A or a 1st gen GSL-SE. The original late style 13B side mounts would come out about in the middle of the frame. You can use the GSL-SE engine front cover or, I understand it's possible to use a 12A front cover on a 13B. I would recommend that you check with Mazdatrix or Atkins Rotary etc. before doing that one.

You'd also need to shorten the shifter shaft to move the shifter far enough forward. That's not too difficult, there's a couple of threads on that on this board, like this one: https://www.rx7club.com/showthread.p...5&page=4&pp=15

Yank the limited slip out of the GXL and use it in a 1.8 Miata diff, it's a much simpler swap than using the long nose GXL diff. I used a GXL diff, but that was only because of the GRM Challenge budget restrictions. I'm sniffing around for a Miata diff now.

Slo Motorsports

It's definitely something to think about. Thanks for the input. I'm sure that I'll have more questions as I ponder this idea.

xrotaryguy

Since your car is an S4, it has a mechanical oil metering pump. Thats good for the conversion. You'll want to use a GSL SE cover because it has the front mounts that you want and it also has the correct provisions for a fuel injection type oil metering pump. You can use a carbureted motor's front cover but then you will be stuck with the carburetor type omp. The carbureted cars didnt so much have "il injection" as much as they had a brass tube drizzling oil down the throat of the carb. Injection is better. GSL SE front covers aren' that hard to find.

xrotaryguy

By the way... my buddies 3 cyl Chevy Sprint Turbo totally smoked my wife's Spit last night.

RX744CSP

iTrader: (4)

NO!!!!!!!!!!!!!!!

edmcguirk

There have been several heated arguments about the turbo vs supercharger on this forum. There are definate advantages to each. My personal preference is for a supercharger. There is a lot more advice and experience for turbos so you'll have to do your own design and fabrication for almost everything for a supercharger.

I would try to get a Thunderbird supercharger and a volvo intercooler. But I would not want to try to fit it all on a carburated manifold. Not much other choices on a 12a though.

By the way, you might have some difficulty putting the throttle body in front of the turbo. I think the shaft oil seals were not meant to keep oil out of a vacuum.

ed

RX744CSP

iTrader: (4)

You know, I never considered that vacuum on the turbo seals thing. I gotta ask my buddy at HOLSET what he thinks of that.

I figured on the intake, WTF as long as we are going crazy get the Mazdatrix intake flange and build something custom.

xrotaryguy

So Mazda Trix has intake flanges eh I thnik that it would almost necessary to build something your self... almost. The FD intake would be nice if we could afford it. There is an adapter that you can buy that makes it work out pretty nice. then you can use the FC intercooler in front of the radiator and perhaps even give it its own e-fan.

xrotaryguy

The diff in My Wife's Spitfire went belly up. The pinion shaft has all kinda of play. I'm tempted to do the Rx7 rear end swap now. I wonder how possible it is to do the swap with out getting as carried away as Rx744CSP? I don't have the suspension bits that I need just yet. Didn't Grass Roots retain the leaf spring for the first iteration if their rear end?

RX744CSP

iTrader: (4)

Yes, GRM kept the leaf spring. I have a copy of the article; if you want, PM me and I'll burn/snailmail a copy for you. Beware, it's not an easy swap. I think, were I in your position, I'd look at a 510/240Z diff. It's narrower etc and should be an easier swap (easy being a relative term).

I got the Abomination running again today 3/17. Woo hoo! It's off to the autocross again this Sunday.

RX744CSP

iTrader: (4)

Aaaand.... busted a homemade CV axle in two. No damage to the car, just to my ego. Massive CV axle rework underway.

xrotaryguy

I got that GRM article in the mail the other day. Thank you for that. What is the plan for the new and improved axle? Do you thing that you can baiscly do the same thing that you did before of will you need to get more carried away? What about using a long sleve to go over the two axles. The sleve could have a bunch of holes in it so that you could do spot welds up and down it's length. Still might not be all that strong. Heck, you'd likely be weakening the axle.

This bit about Nissan / Datsun diffs is sounding better all the time I have heard that Subaru diffs are similar. Do you guys have any idea shich ones have lsd units in them or which ones are stronger than others?

RX744CSP

iTrader: (4)

Yep, Subies use an R180 diff which is dimensionally the same as the R200 (or so I've been told) but the gizzards aren't as stout. That GRM diff was a pretty intense swap, wasn't it?

I got the new and improved axles back in the Abomination today; I beveled the ends of the stubs, drilled a .250 hole in the center for alignment purposes, used a piece of .250 rod, set the welder to 11, and burned them together in layers. I stopped at each layer to wire brush, check for voids, and straight. I then used some .120 wall 4140 tubing, split it (the CV splines are bigger than the center of the shaft) drilled 5/16 holes in each piece, set the welder to 11 again and plug welded the holes, welded the splits (the splits had .125 gaps to allow penetration to the shaft) then circle welded the ends.

I put it all back together today 4/2, and decided dammit if it's gonna break, it's gonna break here. So, I dropped the tire pressure to 20 psi, wound it up to 5000 RPM and sidestepped the clutch. :



I'm thinking it worked.

xrotaryguy

hahaha Niiiiice! Well congrats! Hey, I was wondering, do the Datsun and Scooby diffs have flanges that I can adapt to? Or do they use splined axles? I seem to recall selling a lot of splined Subaru axles for the fronts of Subarus. I dont know what the backs look like. I recall that my 78 280 Z had U joints. I don't recall if it had a flanged stub axle or not though.

Xavier8

I didn't know you had a duelie!! Whats next on the break list?

RX744CSP

iTrader: (4)

Thanks for jinxing an old fat man. I'm going to Myrtle Beach on Sunday 4/9 to try to bust it again.

There's six sets of those burnout marks in front of the Garage Majal.

RX744CSP

iTrader: (4)

And.... 4/9 went well. Car ran great.

Spanked 'em. Got FTD.

Rotored Mini

great to hear the axle repair went well and so did the autocross

do you have any more pics of the car?

I would love to get a closer look

RX744CSP

iTrader: (4)

Took it out again 4/23, car runs GREAT. 3rd fastest time of day behind a turbo 300ZX and a Z06 Vette, the suspension works better than I thought it would. Still some teething problems but nothing I can't lick.

Learned that a rotary backfiring through the exhaust will make a cop grab his gun. I went through the lights, cut the ignition and fuel pump while coasting in gear, then pushed in the clutch, put it in neutral, and KABOOM. Only harm was to my underwear.

xrotaryguy

Haha thats how it is when you have a rotary. Glad to hear that its going so well. I'm especially happy to hear that your suspension is working out so well. I have been thinking of building some similar to what you have. Its scary not knowing what toe changes and camber changes etc to tune into the rear end.

xrotaryguy

Are there any updates to this project? I am still in the gathering parts stage of mine. The Spit is lookig and running better than ever thanks to a new paint job, rebuilt diff, rebuilt drive shaft, and 2 new u joints. It's still under 68 hp Triumph power though. I must say that the rear suspension is fun as hell on an auto cross course! It loves to be driven side ways with the throttle wide open.

I have one queston for you guys. Differentials again. Are the R180 diffs of the 70's vintage Z cars narrower than the R200 diffs of the 80's and 90's vintage 240sx's and 300z's? I have been trying to figure this out based off of pics and doing searches on various forums, but so far to no avail.