View Full Version : 2nd Gen ITS

04-16-2002, 12:36 AM
First of all, this site is what it is because all of you that read, and add comments to it. As you can see, I have only found about this site for a few months now, and am already looking to all of you for help in "doing it once". Some of us could learn form your mistakes, and pass the experience down to others that will eventually ask these same questions again later on. That's what will make these classes grow and not die off.

I have 1st Gen. experience, but not much 2nd Gen. I am progressively building an ITS car, and have a few (more) questions. No ITS rule book yet...still waiting.

1. Is there really a difference in weight in a "sunroof" car versus a "non-sunroof" one?
2. What are the gear ratios for the 5 speed used, and tire sizes allowed (ie. 205/60-15)?
3. If you can update and backdate, can the power mirrors be replaced with others?

I have found a '90 GTU (build date 7/89) with a sunroof, 100/105 compression, 130,000 miles, no smoke, 5-lug wheels, roll-up windows, sunroof, 5-speed, A/C, Arrest-Me-Red Paint...$1500.00. I'm about to buy. Using it for street for a two years, then it's "GUT TIME".

I always appreciate any help given.


04-16-2002, 12:01 PM
1. Ye=, although it's minimal once you remove the sunroof motor and framework, and just bolt the sunroof to the roof. I wouldn't worry about it, it's just more work for you to prep.

2. 3.48, 2.00, 1.37, 1.00, .71, IIRC. Tire size is unrestricted, but it has to fit on a 15x7 wheel.

3. Yes, you can swap mirrors.

FYI, don't forget the 89-91 GTU have 5 lug wheels, but not the 4 piston brakes. You'll want to get those of an 86-88 GXL.


04-16-2002, 04:51 PM
I have heard rumors of a closer 5th gear. Is there one that can be used? 1.00 to .71 should be about a 2300 RPM drop in a 4th to 5th shift using a 205/55-15 tire (23.877 diameter). Say it isn't so! That's 110 MPH in 4th @ 7500 RPM, to 154 MPH in 5th @ 7500 RPM.

[email protected] (http://[email protected])
Paul, I don't want to clog the site with further questions for a while.

04-16-2002, 05:28 PM
That should be a 2136 RPM drop from 4th to 5th @ the same speed. Need to take my abacus to the shop for a tune-up.


Chris Wire
04-16-2002, 06:20 PM
The GTUs has a fifth gear ratio of .756. You can get the gear set (drive & driven gears) from MazdaComp at 800-435-2508. If you are not already signed up, you will have to register for your Team member number. With the 5.12 gear, this seems to be the hot setup in the SEDiv.

The GTUs and other non-turbo RX7s share the same 1 thru 4 ratios, so with the change to the .756 5th gear, you now have a GTUs gearbox.

Welcome to the madness!!!
Welcome to the madness!!!

Chris Wire
Team Wire Racing
ITS Mazda RX7 #35

C. Ludwig
04-16-2002, 07:29 PM
Don't have my manuals here in front of me but there is a difference in 5th gear between the Series 4 (86-88) and Series 5 (89-91). Think the early cars got the .75 like the GTU and the later cars got a .72 or something like that. I'll have to recheck my FSMs.

As far as tires I think everyone is using a 225 of some sort. Kumhos fit fine on my car but Hoosiers rub the lower spring perch pretty badly.


04-16-2002, 09:33 PM

I assume, by the name, you are going to run at Willow. If that's the case, don't worry about the 5th gear, you won't NEED it if you keep the stock rear gear and run 225/50/15's. You will if you change to 4.88's. Calculate for a top speed of around 125 at willow with lap times in the 1:37 range only using 3/4th gear.

Since your name is TURN9, can I assume you have mastered the most dificult turn in all of North America? Please share your knowledge of the perfect line.....

04-17-2002, 06:43 AM
Been there, turned that. I've been found out.

Ran PRO-7 most of last year in NASA and my 2 required regionals in SCCA. Most of my experience came from NASA. Running a "1G" RX7 only using 3rd and 4th around Willow Springs. With the stock 3.909 rear end "welded" gears, it is a fast track. Did a 3 hour night enduro running the first stint for 1.5 hours of it. (saw the fuel pressure gauge fluctuate and still did 1 more lap) What a blast. Used my in-car camera to decide if carrying 4th around turn 2 @ 5500 RPM, was quicker than down-shifting to 3rd and carrying it to 7500 RPM was better, setting me up for the 3rd turn going up the hill. I always shifted @ 8000, and never had a problem

Won't take up this space, E-mail me for more on the story.

[email protected] (http://[email protected])

March RACER Magazine has a story devoted to PRO7, and a few of my quotes (p.82)

04-17-2002, 06:54 AM
Got side-tracked...found out that the turbo 2G's had a 5th gear of .76; whereas, the GTU and GXL had a 5th gear of .71(Mazda RX7 Gold Portfolio). The 4.30 only came on the GTU-S and the rest had a 4.10 rear.


C. Ludwig
04-18-2002, 09:20 PM
OK. Got a look at my factory service manuals today. The 86 NA top gear is a .711. The 90 NA uses a .697 for all except those with the viscous limited slip (just GTUs' or all GTU?) have a .756. For reference the 90 TII used a .719. Now the early Miatas used a .8xx top gear and Pineapple Racing (others I'm sure) do a conversion. http://Forums.ImprovedTouring.com/it/wink.gif Think the splits are closer throughout the box too. Disclaimer: I know it ain't legal... http://Forums.ImprovedTouring.com/it/smile.gif

Also, the auto trannyed 2nd gens came with an open 3.90 rear gear. Just to let you know in case you ever think about picking up a cheap extra 4.10. Don't wanna be surprised.


[This message has been edited by C. Ludwig (edited April 18, 2002).]