Changing my 1st-gen RX7 to ITA

J

joeracerx95

New member
Now that this group has convinced me to stick with my 1st-gen RX7 for ITA, I have some questions.

Stock (rejetted) carb or one of the choices listed in the rules?

What header? Collected/uncollected.

What 15X7 wheel do you recommend. Spacer needed?

What size tire?

What rear-end ratio?

Tri-link rear?

What shocks?

What spring rates?

What's the deal with sperical bearings? I know nothing.

Anything obvious I missed?

Thanks for any and all help

-chuck-
 
Now that this group has convinced me to stick with my 1st-gen RX7 for ITA, I have some questions.
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My opinion isn't worth the time you take to read it, probably, LOL, except for one thing:

Call Jim Susko, and buy his setup manual. He is G-Froce Engineeering, and while you may, or may not agree with his conclusions, his thought process should be worth the price of admission. That said, here goes:

Stock (rejetted) carb or one of the choices listed in the rules?
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Stock reworked. Paul Yaw was the guru to go to, but he's gotten out of the 1st gen biz...not enough volume he told me last time I got him on the phone. I guess he's still waiting far a few to trickle in as he's had two of mine for over a year...on for service, the other for "Yawism". ISC used to do it as well, not sure if they still do. And PB&J Racing says they do, but I have no idea of the service they might provide. Others will have other options, I hope.

What header? Collected/uncollected.
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I run a custom prototype, and it's uncollected until after the rear axle. Others have success collected. The ISC stailess header is smoother than the Racing Beat, and lighter. A good peice.

What 15X7 wheel do you recommend. Spacer needed?
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I run 13, as it works better with the tire and gear choices, and keeps unsprung weight down.

What size tire?
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I have run 225/50/13, but will probably switch to the 45s this season to get the car down a bit more.

What rear-end ratio?
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Track dependant. I run a 4.88, but guys run 5.12s as well.

Tri-link rear?
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yes

What shocks?
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many choices. For the stiffer spring rates, the Tokiko choice isn't going to cut it, although they are a popular choice, due to $. Advanced Design are cool, but they have issues with gas leakage and the attendent hassle of refilling, and are moderately priced. Koni double adjustable are a great choice, also moderately priced. And you could always get serious with Penskes, etc.

What spring rates?
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Again, very track dependent.

What's the deal with sperical bearings? I know nothing.
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You can use a SB in an unmodified component that had a bushing in it previously, and you may tack weld them in place. RX-7 use them commonly in the lower rear longitudinal links, but not in the front of the drag link on the front control arm, for example.

Anything obvious I missed?
Thanks for any and all help
-chuck-
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I assume we'll fine tune those answers as we go along! Welcome to the fun!

(And if anyone can point me to my code screw up, I'd be HAPPY to fix this mess! thanks)
 
Stock (rejetted) carb or one of the choices listed in the rules?
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Stock unless you just like playing with carbs. The faster IT7 cars around here seem to all have stock Mikuni carbs.

What header? Collected/uncollected.
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Racing Beat. Collected as far aft as possible, like somewhere around the rear axle.

What 15X7 wheel do you recommend. Spacer needed?
What size tire?
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We're still running 13" wheels/tires (Panasport, No spacer).

225/45 13

What rear-end ratio?
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Depends on the track and your level of engine prep. With the relative lack of "grunt" in the 12A, shorter (numerically larger ratio) gears are better.

Tri-link rear?
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Depends on track and your driving style. A lot of folks like the tri-link. Watts links are pretty common, too.

What shocks?
What spring rates?
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Hmm. Depends on you and the car. I'm not sure what's in ours right now.

What's the deal with sperical bearings? I know nothing.
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When you lower a production car to IT limits, the stock suspension has a tendency to bind. Definitely true for the FB RX-7. The spherical bearings on the sway bars and such help to alleviate that binding, making the suspension much more predictable.
 
Big Thumbs up for PB&J carbs. Service was second to none. I sent him my "2nd Big Name" carb to work on and he gave me a big run down on the problems with the carb. I had it back on the car w/i 2 or 3 weeks and that was during the bad hurricane season a couple of years ago (Carl's based in FL). Try that with a Yaw ;)

There's a link to PB&J on my links page www.izzyscustomcages.com/links.html Follow the dancing bananna and tell him that Izzy's sent you!
 
among the ITA Rx7 drivers I know in SEDiv, the tire profile in 13" is variable, depending upon the track. The guys I know run 225/45/13 at Road Atlanta, but 225/50/13 at CMP. Most prefer the 5.12 rear end, but some of us can't afford it yet and run the 4.88. While 15" wheels, on the surface, sound like a good idea, they raise your CG, or cause you to further bind the stock suspension trying to get the CG back down (if possible at all). They also increase rotating mass, a big no-no for low torque engines. Just my $0.02 worth from someone who barely knows the difference between a spark plug and an oil drain plug.

Scott "Righty" Franklin (Captain Who's brother)
www.NutDriver.org


BTW, what ever happened to Stan and SDJ? Had some good parts, did good work, but seems to have disappeared from the face of the earth.
 
Righty, someone posted here some time ago that he had bought equipment/whatever from the Stan's business.

Chuck, you may also want to throw out the Watts linkage & replace it with a Panhard bar. The OEM Watts linkage is another cause of rear end bushings binding.

Also with the Panhard bar analyze the the turns & the number of R.H. & L.H. turns at the tracks you run. this may support the side of the chassis you mount the Panhard bar to.

Improved water & oil coling radiators.

Underdrive pulleys.

Header heat deflector away from carb/intake.

After market fule pump, regulator with a ACCURATE gauge.

Cool air intake.

MAKE SURE the car & driver are at the minimum weight of 2280 pounds.

Enjoy the economics of your car choice ;)
David
 
Welcome to ITA and a great car. I love mine!

Here is another vote for the Susko setup manual - my car follows pretty much all of it and it very easy to drive fast. I have Koni's on the front and split valve Pro Shock on the rear.

The OE watts link mount break can break at the axle - I have a panhard rod and a Tri link. I like spherical bearings.

13" wheels for the same reasons listed by everyone else. I run Kumho v710's in 215/50 x13 and like them allot

I have an ISC header w/long tube primaries that merge at the axle into a 2.5" single

I have two carbs - one built by VanSteenburg and the other is a Yaw. Both work fine

Spend money on cooling - I have a 22x19 dual pass radiator that was built by Ron Davis and it works great. I also use OE oil coolers - two in series in the summer - with -10 lines.
 
Thanks for all the feedback, it helps immensely.

So, I just saved about $1,000 because I get to use my stock/Pro7 carb. :D
I get to save about $2,000 because I get to use my Pro7 13X7 wheels instead of buying 15". :D
Now I need a new ring&pinion, probably 4.88.
I might need different shocks, I currently have Tokico Illuminas.
At some point I should change to a tri-link/panard.
I need a header.
I already have a dual pass/dual core aluminum radiator.

I think I'm set for now. :eclipsee_steering:

Thanks again for the advice. :happy204:

-chuck-
 
Have fun with the racing! But, DO buy the $75 Susko book, it will end up saving you wasted money dorking with this and that...and you'll learn so much about these cars. It's worth more than the price.

And one more thing, think carefully when changing your struts/inserts/brakes, etc. The later "big bearing" struts are better, but less common and all parts are not interchangable. just a heads up.
 
Also, make sure you've got plenty of oil cooling going on. In the southeast, and probably most anywhere in the southern half of the lower 48, that means either a separate oil cooler or one that's combined into the radiator.
 
hmmmm i still have one of the originals air dams we used to use in the 80's in my ITA RX7,, its brand new still never used it, as i kept it for spare,, to bad i dont run a first gen RX7 any more, maybe i should put it on e bay..
 
yes i coould, but the only reason i dont sell it, is i hate to pack it up, hard to find a box to fit it,, if you ever come to so cal let me know,,
 
MAKE SURE the car & driver are at the minimum weight of 2280 pounds.

Enjoy the economics of your car choice ;)
David
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David -

Do you know something I don't???? :unsure:

I was thrilled when they changed our min. weight to 2280, but I only know of 1 guy who can come anywhere NEAR that number. Yes, I probably weigh about 180, but I'm not going to lose more than about 20 pounds. Last time the car & I went over the scales we were something like 2309.

I don't run a coolsuit or a camera or anything else I don't have to.

So, basically "good luck getting to 2280'!

As far as your last comment, all I'm going to add is "Amen!"
 
Mike, that's about 20 pounds...for an IT car that's pretty darn close, and I would have a hard time going to the ITAC and saying "Move it to ITB cuz it can't make weight."

It's less than 1%, and that would have to fall into what would be considered "noise" in any scientific experiment, especially one such as this, with the lack of controls, right?
 
Mike, that's about 20 pounds...for an IT car that's pretty darn close, and I would have a hard time going to the ITAC and saying "Move it to ITB cuz it can't make weight."

It's less than 1%, and that would have to fall into what would be considered "noise" in any scientific experiment, especially one such as this, with the lack of controls, right?
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Jake -

I plead "it's Friday". I have no idea where my brain is right now, as I have to leave for Savannah after work.

The old weight was 2380. I usually hovered around there (the car was actually DQed a couple of times for being just under, but not since I bought it). There was ballast that I removed, but it only took me down to 2360-something w/ a bone dry cell.

Most of the other guys I race with could get near the old weight, but nobody seems to think we can find anywhere near 100 pounds to drop.

(c'mon.... WEEKEND!) :birra:
 
Heck, I was glad I finally got below 2380 !!! 2280? Yeah, Mike, you really aren't helping !!!

So - you lost me; just how far over are you, now? About 90 lbs?
 
David -

Do you know something I don't???? :unsure:

. Yes, I probably weigh about 180, ...... Last time the car & I went over the scales we were something like 2309.

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Mike, I was commenting on the above quote. If you mean "about" to mean 185-6 or so, and the car is 2309 as is, if you could lose 5-6 pounds, you'd have a car about 23 pounds over. That's pretty close!
 
Hi Joe-
I'm a San Francisco region long time ITA rx-7 runner. I will also echo the Jim Susko recommendation. The tri-link and front radius rod spherical kits are excellent (except you need to add nylock nuts to replace the nuts/lockwashers that come with the tri-link). His spring rate recommendations are good, although his blue dot rear springs are too short to keep my car off the bump stops (so I run 1-1.5" of spring spacers).
If you are not already signed up with Mazda comp, do so. (http://www.mazdamotorsports.com/webapp/wcs/stores/servlet/Home?storeId=10001&langId=-1)
They have brake ducts that work well. They have a big radiator that works well. They have the enginer pulleys that work well, etc etc.
In San Clemente, I believe you are going to run SoCal, and all those tracks are FAST (willow springs, california speedway, button willow). I wouldn't run a final drive shorter than 4.44, and would consider locating a 4.10. I had a 4.33 at Willow springs several years ago and it was too short (with 225-50/r13 hoosiers)!
Good luck getting the car set up and down to legal weight--I'm about 60 lbs over.
Look for Bob Bradfield ( Bobcat racing) at some of the so-cal evants. He is a great driver, friendly, and has a very simple car!

Feel free to drop me a note at [email protected].
Good luck with the car!!

Tak
#29 ITA SFR SCCA
 
Hi Joe-
I'm a San Francisco region long time ITA rx-7 runner. I will also echo the Jim Susko recommendation. The tri-link and front radius rod spherical kits are excellent (except you need to add nylock nuts to replace the nuts/lockwashers that come with the tri-link). His spring rate recommendations are good, although his blue dot rear springs are too short to keep my car off the bump stops (so I run 1-1.5" of spring spacers).
If you are not already signed up with Mazda comp, do so. (http://www.mazdamotorsports.com/webapp/wcs/stores/servlet/Home?storeId=10001&langId=-1)
They have brake ducts that work well. They have a big radiator that works well. They have the enginer pulleys that work well, etc etc.
In San Clemente, I believe you are going to run SoCal, and all those tracks are FAST (willow springs, california speedway, button willow). I wouldn't run a final drive shorter than 4.44, and would consider locating a 4.10. I had a 4.33 at Willow springs several years ago and it was too short (with 225-50/r13 hoosiers)!
Good luck getting the car set up and down to legal weight--I'm about 60 lbs over.
Look for Bob Bradfield ( Bobcat racing) at some of the so-cal evants. He is a great driver, friendly, and has a very simple car!

Feel free to drop me a note at [email protected].
Good luck with the car!!

Tak
#29 ITA SFR SCCA
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Thanks Tak, I talked to Dave Lemon over at Mazdatrix about the final ratio. Using Paul Yaw's calculator, ( http://www.yawpower.com/download/gearspr.xls ) factoring in a 225/45/13 tire and using 3,4,5 gears the choice is a 4.88. I assume you must be sticking with 2,3,4 gears if you are staying that low on your rear ratio.

Currently my car is prepared to the CalClub Pro7 rules so I'm definitely a member of the Mazda program.

I installed the ISC exhaust system this weekend. This is a very nicely made system. It couldn't have bolted in any easier.

I ran my Pro7 car in ITA in the SFR in a few events the last two years. Bob Bradfield is the first person I met when I got to the track and we've been friends since. Heck of a nice guy. I've been swapping e-mails with him to get his set up since he was so successful in ITA running his 1st gen. He claims to lack a lot of detailed knowledge because he says he's just, "the monkey behind the wheel." :eclipsee_steering:
 
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