GTUs 20B N/A Build Thread

[Christopher W.]

I have posted this thread on the other forum....but I kind of like the vibe over here better.

Plus I can't seem to get some basic questions answered. Anyway, I am just doing basically a cut and paste job.

So here goes..

I first found out about this car on Autotrader in 2000. I contacted the owner and the car seemed perfect. I just couldn't afford it. So over the course of the next couple of years I continued to contact the past owner. He still had it for sale but I still could not come up with the money.

At that point in my life I was living in my shop, surrounded by RX7s and I decided that it was time for a change. I sold all of my parts cars and tools and my 87TII. I moved from Little Rock to Fayetteville Arkansas.

I soon found myself moving to Italy, Northern Tuscany actually for a year. That was awesome.

When I got back from Italy to Fayetteville the bug started hitting again. I found a second gen in Houston that I was very interested in. I was just about to pull the trigger on that car and I decided one day out of the blue to see if Randy still had the car for sale in Mesa, AZ. I remembered his name, called information and got Randy on the phone. He said that he had just decided that day that he finally was going to sell the car. He was looking into running it through Barrett-Jackson.

We came to an agreement. He dropped the price 2K and gave me 6 months to pay for it.

So that is how I got the car. The car was pristine, 48k miles, always garaged and very, very few times did it get caught in the rain. It had a Nelson-Paxton supercharger and lots of suspension done. It had Mazdaspeed coilovers and some other bits and pieces. Here is a list of all of the stuff that came on the car when I bought it. Red means I have sold these parts..

Nelson/Paxton Supercharger SN2000 HO Blower with B&M Racing Cooler
Mariah Motorsports Naca Duct Headlight Cover
K&N filter in a Mariah Motorsports Cold Air Box
High Pressure Fuel Pump
Mazda RX-7 Turbo II Fuel Injectors
Corky Bell adjustable Fuel Pressure Regulator
Jacobs Spark Plug Wires
HPC coated Mind Train Header
A'PEXi GT Stainless Steel Exhaust
5Zigen Typhoon Wheels – 17 x 7.5 Front, 17 x 9 Rear
New Kumho Tires
MazdaSpeed adjustable coil-over shocks
Suspension Techniques Sway Bars
Racing Beat end links
Mazda Competition Adjustable Rear Camber Link
Hawk Brake Pads with
Mazda Competition Stainless Steel Brake Lines,
Mazda Competition Motor Mounts and Transmission Mounts
C’s Short Shifter
Tri-Point Engineering Air/Fuel Ratio Meter
Optima Battery Relocated to passenger-side rear storage compartment

It ran great but I wanted something more. So that started the 20B dreams. Well that didn't start the dreams but it gave life to my dream car.




















My goals for the car are to build a car that is more race car-ish than actual race car. I will not race this car. I will do track days and drive it on the street.

I mean I am doing things like no stereo but it will have AC.

One thing I noticed when I bought the car is that it was loud and hot inside. So that started my quest to deaden the sound and stop the heat from pouring in through the firewall.

So, I decided to get started. First I sold the charcoal wheels you see in some of the pictures. Then sold the supercharger and exhaust.

Then it was time to remove the interior. As you might know or expect lots of things like to break when removing brittle plastic parts. It was not to bad though. The car had always been garaged in AZ. It is amazing how well rubber and plastic will hold up when it is only getting hot. Not ever getting freezing really preserved this car well.

[Christopher W.]

I decided to do the FoamSeal trick to the frame rail cross member behind the seats and the running boards under the doors.

I have a thread that covers all of this. So I won't go over it here but it worked well and I am glad I did it.

http://www.rx7club.com/showthread.php?t=743378

When I got the engine out it was much more of a mess than I had anticipated. The OMP was spraying oil all underneath the car. As you can see in the pictures the engine bay doesn't match the outside of the car.

The reason why the engine firewall is not painted is because I am spraying a sound deadening material on the firewall and underneath.
















Next I decided to do some kind of spray on sound deadening material. I found some different ones out there. I decided on LizardSkin. It is not the cheapest but I really liked the guy I spoke to and they had two products. One is for straight sound deadening the other has a ceramic component for heat blocking.

We sprayed the interior and underneath. Prep was the pain. The actual spraying was not a problem.

[Christopher W.]

So that is kind of getting me down the road with the interior stuff. I did remove all of the auto seatbelts. I am going with straight street harnesses so I had to find all of the parts to change over. I have no seatbelt mechanisms in the car at all.

I bought two of the last three a-pillar covers for a manual seatbelt car left in North America...

I also found a TII transmission with less than 1k original miles. The story told to me was that Mazda took a TII off of the assembly line and gutted the interior and put IMSA sheetmetal on it. The car toured the US doing promo type stuff. The car only drove on and off the trailer basically. So it is probably way less than 1k miles. As you can see in the pictures it is prestine. That trans has not been cleaned. You can see the paper stickers are still almost perfect. I payed $500 shipped. Sweeeet!!

Around this time I was still having a hard time decided what to do about an engine. I was waffling by the hour as to maybe a LSX or 20b or what. I think that this transmission was what keep me from the darkside. I had to have this transmission in this car.

So I finally decided on the 20B. I got a hold of Japan2LA and bought one with a blown seal. The deal went great. I had it shipped to Logan at Defined Autoworks. That is who is building, installing and tuning the engine.

I will get a little more through this stuff and then get more to what is going on with the engine.

I also wanted a Torsen diff. I loved the one I had way back in the 80s in my built 72 240Z. I don't like the Kazz clunking. That is totally unacceptable in a street car for me.

By the way, I am 45 years old. I am not driving around in a loud, clunking, hot obnoxious RX7.

I bought a S5 TII rear, a S6 diff and some new S4 stub axles. I also really like the 4.3 gear. I got a new one from Racing Beat. I don't know if I will keep it in. We will see when I get it on the road.

The rear went together without a hitch and got all cleaned up and painted.


















Oh yea, we also dropped the entire suspension before we sprayed LizardSkin. At that point I bought all poly bushing. We replace everything except the rear subframe mounts. They were in great condition and I don't want to much NVH. Also did the DTSS elim bushings.

I found some kid on the other forum selling his new in box Cusco Zero2R Coilovers..... they are beautiful. Retail is around $2500. I got them shipped for $1550.

I also found a brand new Electromotive Tec3R.....$1100 bucks shipped for the ECU. Sure beats $2000.00.

[Christopher W.]

Now on to the roll bar.

I had a company in Springdale Arkansas build the roll bar. They are Macon Motorsports. They mainly build V8 engines and do some custom fab work. Bob, who worked on my car has been building chassis, experimental aircraft and is a aircraft mechanic for thirty years. He part times at night at Macon. He did an awesome job.

We thought about adding more bars to the roll bar but I decided that it would serve my purposes as is. I didn't want to much visibility blocked because it is a street car after all.

[Christopher W.]

Now the car is back at my house. I have got the interior for the most part back in.

I bought a pair of Recaro Pole Position seats. I got Recaro sidemounts and sliders. It was a joke. I am only 5'9" and my head was hitting the roof.
We scrapped the Recaro sliders and custom fit the Recaro sidemounts to the OEM sliders. The fit is perfect. Although the seats fit pretty snug. I kind of wish I had got the large edition. They fit me almost too perfect. Maybe a little tight in the shoulders. I have a 31" waist and broad shoulders. The only problem will be for other people. One of my best friends I grew up with building cars (Datsun 240Zs) is now about 400lbs. He will have to sit on top of the seat. No way to fit in it...at all.

The OEM back deck stuff won't work with the roll bar. So Bob is going to make a custom back deck that will be shorter and angle down toward the front of the car. I should be able to keep the bin lids. I have a tiny Odyssey PC680 mounted behind the passenger seat. Seeing how I have no stereo I don't think it will be any problem at all.

I also put a few pieces of Hushmat on the inside of the roof, back deck and various places. If you tap on the roof it sounds like a Mercedes....or better.

I took a contractors double light on placed it inside the engine bay pointing towards the firewall. I turned on the contractor light and turned off the lights in the garage at night. I got inside the car and looked for any light coming inside the car through the firewall. I completely blocked and sealed every bit of light the I could see. No more heat just pouring in through the firewall.

[Christopher W.]

Here is my little project for the side mirrors.

I really like the S5 mirrors....but they do look kind of chunky on the side of the car. I decided to have some side mirror mounting plates made to put some small light weight carbon fiber mirrors. I am still not to sure about the carbon fiber. I don't want to look to ricey. We will see. I will get the side plates powder coated black after I get the correct mounting position for the mirrors.

And no, I am not selling my OEM side mirrors.
















Well, now on to the fun stuff.

Logan, at Defined Autoworks is doing the engine. We have broke apart the engine and found one housing bad. So, we got one. We have three N/A rotors that have been sent out for balancing. Logan is building a custom exhaust. Header will go back to a Borla XR-1 then will split into two. Then there will be two Borlas at the back. We are looking into doing a valve in the exhaust to help with volume levels. It is not being designed for performance so much as keeping the thing civil on the streets until you open up the throttle.

I am not sure how much to talk about here. I don't want to give away any of Logan's suprises. But anyway, I am sure Logan can come on here and give more details if he likes.

Semi PPort
Six independent throttle bodies
Tec3R

Oh yea, I did depower and weld the steering rack the right way.

I hope to have the car to Logan by the middle of next month. I am about four months behind when I thought it was going to be up there. Anyway, maybe get it back in the summer.

We are hoping for 350-380rwhp....maybe more. I am not planning on running the engine up over 8500rmp.

Here is a link to my coilovers..

http://www.rallitek.com/cuzecosu.html

We will see how these do. Spring rate is 8k front and 6k rear.

[Christopher W.]

My first question,

I bought a clutch and pp from Corksport for my TII transmission before I knew I was going the 20B route.

ACT 'XACT' Streetlite Flywheel
ACT Street Performance Clutch Kit

Does anyone see any problem with using this setup if I am going to be around 375rwhp?


My second question:

I remove the heat shields.

I am going to wrap the entire exhaust for the following reason:

1. To help scavaging
2. To reduce heat
3. I think it will give the exhaust a lower tone.

Is there any problem with not putting the heat shields back on?

[Max777]

clean FC!

I think that you shoudl return those coilovers, and purchase STANCE GR+ units instead. They are only 1500 and better quality than the cusco ones. If I spent 2500 on FC coilovers, I would get some DG5's instead of cusco.

Second: I dunno about you, but I would keep the heatshields on there unless your custom DP just will not fit any way imaginable, or unless you're building a serious full race car that will not be driven on the street.

[Christopher W.]

Originally Posted by Max777

clean FC!

I think that you shoudl return those coilovers, and purchase STANCE GR+ units instead. They are only 1500 and better quality than the cusco ones. If I spent 2500 on FC coilovers, I would get some DG5's instead of cusco.

Second: I dunno about you, but I would keep the heatshields on there unless your custom DP just will not fit any way imaginable, or unless you're building a serious full race car that will not be driven on the street.

Coilovers were bought NIB off of the other forum. There is no sending them back. I only paid $1500 shipped for them. I think the top of the line Cusco will probably do everything I am hoping for.... I am keeping my Mazdaspeed coilovers until I verify that I want to keep these. I looked at many other brands but these were priced right and the Scubie guys really seem to like them.

This is a N/A street car. No dp but a custom header made by Defined Autoworks.

[Max777]

Holy smokes, all that work and no snail? What gives? And, sorry, I missed that part about the coilovers being bought used...

Also, if you're 45 and have this level of tuning ability, then why not the FD? You could obviously afford one.... I love the FC myself, but if I were rich... I'd deff switch.

[FerociousP]

don't listen to him... I'd rather seen a super clean FC than a FD anyway... especially a ITB 20B... no stickers please

[Phoenix7]

Originally Posted by Christopher W.

My first question,

I bought a clutch and pp from Corksport for my TII transmission before I knew I was going the 20B route.

ACT 'XACT' Streetlite Flywheel
ACT Street Performance Clutch Kit

Does anyone see any problem with using this setup if I am going to be around 375rwhp?


My second question:

I remove the heat shields.

I am going to wrap the entire exhaust for the following reason:

1. To help scavaging
2. To reduce heat
3. I think it will give the exhaust a lower tone.

Is there any problem with not putting the heat shields back on?

if you're still going to use the TII tranny with your 20B then keep it and use it...I don't see you prematurely wearing out the clutch at 375hp...unless you like to drag race.

As far as the heatshields......that's a tough call. If you get the really good wraps (cool to the touch) then the shields would just be useless. Also, I assume this car will never see a wet road, right? don't forget some wraps rot when they're wet and it could eventually damage the exhaust.


Did you ever dyno your SC setup?

[Christopher W.]

Originally Posted by Max777

Holy smokes, all that work and no snail? What gives? And, sorry, I missed that part about the coilovers being bought used...

Also, if you're 45 and have this level of tuning ability, then why not the FD? You could obviously afford one.... I love the FC myself, but if I were rich... I'd deff switch.

Well the coilovers have never been installed...

As far as turbo, I don't want the complication. I want the reliability of N/A. I also want the linear power curve. I believe 375rwhp will make this just a super fun car to drive.

I also have ridden in cars that are mostly around 350 to 400rwhp. And they felt great. I don't see any need for a 550rwhp 2800lbs street car. At least not in my world. If I could do it without a turbo I would be interested. Maybe a 4 rotor someday...

As for as my level of tuning. I have none....yet. That is why I am using Defined Autoworks. I can change parts and things but I am not building this engine or tuning it.

Next thing, I am not rich at all. This is requiring a lot of effort, work and expense. It is really not a very smart financial decision but I am committed to complete this project. There sure are a lot of nice cars for sale out there. To bad I can't take advantage of a bad economy.

If I had bought an FD then I never would have satisfied my love and yearning for a wicked FC.

By the way, if I get a FD someday, it will be a LSX V8....

[Christopher W.]

Originally Posted by Phoenix7

if you're still going to use the TII tranny with your 20B then keep it and use it...I don't see you prematurely wearing out the clutch at 375hp...unless you like to drag race.

As far as the heatshields......that's a tough call. If you get the really good wraps (cool to the touch) then the shields would just be useless. Also, I assume this car will never see a wet road, right? don't forget some wraps rot when they're wet and it could eventually damage the exhaust.


Did you ever dyno your SC setup?

The SC came to me with a dyno sheet of 225rwhp. I don't remember the TQ numbers. I actually have the sheet around here somewhere.

No rain and no drag racing...Well maybe no drag racing. No clutch dumping drama anyway.

I will definitely be using the best wrap that is available. Thanks for the input..

FerociousP - If you mean no stickers on my car, not a chance. The only stickers are the GTUs stickers. I actually bought four more just in case I need them in the future. Damn, $100 for four from Mazdatrix...

[Phoenix7]

also, THANK YOU very much for not going LSX with this GTUs...Keep it up and keep us updated....we actually have quite a few GTUs owners on this board:

I forget to tell to join the club
http://rotarycarclub.com/rotary_foru....php?groupid=8

225 is not bad at all...