Okay, people ask what have I been working on, on my FC3C and RX-7s in general.


As many of the long term users here know, last year I took my 'vert and put a rebuilt Jspec and driveline into it. My goals at that time were to #1 gain power, #2 pass CA emissions, #3 to retain the stock look. Lets face it the 'vert while being one of the best handling FCs just was a little low on HP in North America. And since I live in California, I must meet emissions testing once every two years.

I went with a FMIC but other than that and a Bonz highflow and down pipe, the car looked stock (other than the intercooler behind the front openings).

But I was ultimately un-happy. While the high HP was eye opening at first, the extra weight of the Turbo engine, driveline, and other extras, increased the plow of the car and made it feel much like the overweight pig it had become. I looked at removing the FMIC and going with a Sparco water to air unit, but lets face it... that only solves a few lbs. Yeah I could strip the car out, but I put the Turbo motor in to make the car be a cut rate version of the S2000 or Z3. Something that I could drop the top on and still style down the road. Not a stripped out hulk.

So I slowly came to the conclusion that the only way that the car was going to get back to its tossible youth, was to remove the 13BT and assorted heavy extra parts and go back to Non turbo.

I started with a blown S4 motor that I got from a fellow forum member in LA (Ni5mo180SX) for a rebuilt wiper switch and some cash. This I ended up rebuilding myself as the motor although had been over heated, was in basically good condition. The End plates needed lapping, but other than new gaskets and that, it was pretty good to go. I went with new stock 3 piece Mazda Apex seals as well, as the apex slot was in great shape on the rotors.

From there I did a minor street port. Remember being in CA; I still need to pass emissions. But at the same time as the block was coming back together I convinced a local shop that does aircraft parts, to reverse extrude hone a modified S5 middle (VDI section), S5 upper intake, and S4 LIM.

This turned out to be a mess. What was I thinking here? Each time the intake was extruded it wasted a VDI valve. Plus after the first cut, the VDI had to be switched position to extrude the short path. Three VDI valves later and now I had my perfect port matched and dull finished ported S5/S4 combo intake manifold. (I'll go into all the details on what I did to make this work better than most S5 intake on S4 motor conversions soon).

Whoops... need to reverse the PD:


Holes don't match between the VDI and S4 intakes,,, time to drill so they came match before we extrude it:


Fitting:


While the intake was out getting done, I swapped out the rear end with one from a 88 GTU, and managed to get the motor and tranny back in. Its funny the simple things you forget, like that I needed a new clutch slave (the Turbo tranny used a different slave) and things like that.

Once the intake was back, it was time for reassembly and then figuring out where all the vac lines need to go. There are actually substantial vacuum routing changes between the S4 and S5 intakes.

Next came the cat back. The stock convertible Cat back that had lasted through the original motor, then the turbo motor was now shot. The pipe had broken between the cat and the actual Y so the that flange and pipe could be spun 180 degrees. Really the only thing that held the y pipe together was the Mazda factory heat shielding.

Well, I had wanted to come out with a new exhaust on my web store (under cutting CorkSport on cost), so now was the chance for some tax deductible R&D. I tried a couple of Ebay mufflers, but was generally unhappy (too loud for a convertible). Then my local exhaust shop (that had been doing the exhaust welding for me) came up with a new stainless 3 inch in muffler. We had already decided that for shipping, we would want this to be a two piece (three piece on the dual muffler version) and that we needed to be able to not wake the dead. Ideally we wanted the exhaust tuned specific for a non turbo motor (something that most aftermarket exhaust systems are not designed for), peaking in the upper mid range where the N/A motor often looses its torque again.

So intake done, exhaust done, I added a crane cams Hi6 and Iridium leading plugs (damm things were $25 each and a special order from a local racer parts store). Now Nippondenso claims a min of 5 HP increase with just the Iridium plugs, skeptical I tried them more for plug life than anything.

So then after about a month of break in driving it was dyno time... what did we do?



Well above what I was shooting for and in the range of a turbo motor.

Figuring about a 25-30 HP loss to drive train and assorted options, we estimate that motor to be putting out near 200 FWHP. The same as a stock S5 Turbo- all while meeting the stringent California emissions (well other than the missing EGR valve, but we'll see if they even notice that). But the big thing is an almost flat torque curve from 3000 RPM up.

My 88 'vert now chirps tires in the first couple of gears, something that the bloated turbo 'vert never did, and with my non-P package vert weighing in at 2890 with a half tank of gas (and full interior and air conditioning, and power steering). That makes it lighter than the S5 GXL and S5 Turbo and only 90 lbs heavier than a 89-90 GTUs.

So see you can have performance in a "heavy" vert while still staying away from a motor swap.

More pictures to follow.

 

Does this vert have any suspension mods? I can understand how the extra bulk of a TII conversion can make the already bloated vert feel sloppy, but some simple spring and strut mods would take care of that...AJX's and Eibachs for comfort and performance great job on the NA motor though, thats a nice amount of power!! still missing all that turbo torque, but a nice free revving NA rotary is a beautiful thing. Once I throw my TII conversion in my NA (everything is sitting in my shop) I'd like to build an NA FB one day with a street mikuni setup (25 yrs old = no more emissions tests in NY hehe)

 

Wow. That's quite a nice bit of work, Icemark. I'm curious about:
1) How much power do you estimate is from the unique intake work with streetporting, and how much from your exhaust?
2) How much weight savings from the NA drivetrain, and how much from your exhaust?

Being broke, I'm idea-gathering for my S5 NA project.

 

wow thats nice power!

 

#1 Probably the intake work is the biggest jump. Maybe 20-25 Hp between Extrude Honed intake, and minor porting. Most street ports are only about 10-15 HP, and I think I did a pretty conservative cut and dyno testing has showed only a max of about 15 peak HP using a port matched S5 intake on a S4 engine.

#2 probably a little over 200 lbs compared to before and after (including using the single muffler on the exhaust). Typically the Turbo and drive line adds abot 150-175 lbs over a Non Turbo driveline.

This set up should not be considered cheap. The extrude honing of the intake alone cost more than the motor and gasket kit cost me.

 

was the extrude honing in the 500 dollar range???

 

Yeah just over that. It would have been about $100 cheaper if he hadn't had to make a custom manifold template for the machine.

He had the template already for a S4 turbo

 

Damn, that's awsome. Never thought I'd see someone go back to n/a in a car that they'd already worked on to become turbo! I have seen ppl buy another car to keep n/a, but then again, you've gotta have passion for that kind of thing, and passion does not mean you scrap one car because you want something different, you keep at it untill you have what you want!

Good job, man! I will prolly have some questions for you later on when I get busyer with my '88 SE that will be staying n/a.

 

Nicely done Mark! All that work certainly paid off! Color me impressed.

Steve

 

Ah, now I have to see how it will do against RarestRX...we should be now within 100 lbs although He should be putting down more torque.

 

Impressive could you sepcify which engine you used? Rotors and the rest?

 

Yes, outstanding job!
Enjoy her now!

 

Ahh, I'm within ~70 lbs of Kevin now, and haltech's going in soon! Turbo torque!

Steve "Not quite smog legal though..."

 

props

 

wow i always heard people say extrude hone couldnt be done on the IM and those are some pretty serious gains from it. do you think you gained more from extrude hone than you could have from mannualy porting the IM?

 

And noone has said it but when do we get to see a sneek peek at the exhaust? When will it be in production and how much is it gonna cost?

Thx

 

Very nice. I've been thinking about what to do with my intake, so now I have a few new ideas. I've got a friend in Arlington that builds trubine engines for helicopters, as well as massive horespower V-8s for drag racing. Imgonna have to see what he can do for me one I get everything figured out.

 

I have a couple in cold weather testing right now... looking at around $250 for the single and $350-$400 for the dual.

I start having them available once I know that they will be durable and that there are not any design flaws. Probably spring time.

 

Actually even the corporate extudehone.com website lists a price for intakes for rotary engines (frightfully close to what I paid), but many shops through out the country can abrasive flow machine parts.

They typically say about a 30% flow gain from aluminum intakes abrasive flowed, but I think that is more for a V8 style intake like on a mustang.

And yes, with our intake tube design I think it would be next to impossible to get the same kind of increases from porting by hand. In an ideal world I would have flowed the intake and the engine all together. I need to find the pictures I took looking down the intake. Even the lumps from Mazda's re-enforcement of screw holes are gone and clean.

 

That's what I was thinking. I just couldn't give up all that turbo torque. While the engine results are very impressive, I think I'd have put the money into suspension instead. Good work though.

 

knight1976: that fb is sexy man. i think maybe in the future i will make my fc a turbo track car, and buy an fb.

 

Yo,

Damn Mark, that's some serious power! Check my new thread, just dyno'ed the other day.

You're gonna make me get a streetport! Heh. I'm pretty happy with the dyno results, we could possibly squeeze a few more if we get agressive on the AF...but I'm stoked that the S-AFC did so much!

NA Powah!

Kevin
1989 GTUs "No turbo, no problem!"

 

Well its nice to know my NA at least has the POTENTIAL to chirp its tires, LOL.

Good job.

 

thanks for the compliment but the pic makes the car look a million times better than it really is. It has oxidized paint, dents and dings, and the interior is shredded.

 

That sounds great, i can't wait till that becomes available. How do u think this will compare to say, the RB exhausts?

And thats an impressive amount of work u did with your vert there. Is there anything you DON'T know??
Thank god you post on this forum