Simon's RX-7 Race Car Log Thread
 

So I bought this 83 RX-7 back in June, it was raced in Spec7 out west and brought to the east coast at some point, I bought it locally with plans to run it in IT7.

This thread will be sort of my log of events with the car, prep work, changes, and I WILL HAVE QUESTIONS! I'm new to RX-7s although I have had a huge rotary obsession since I first got into racing, though I'm not an expert, I understand the basics.

Mods:

-Header w/ full exhaust.
-Strut tower bar.
-Full roll cage.
-Tokico struts.
-Unknown springs.
-Some type of aftermarket sway bar w/adjustable end links.
-Steel braided brake lines.
-Panasport for dry/Diamond Racing wheels for wet.

Not sure what else honestly. lol Looks like most of the bushings were replaced not sure on the specs though.

Day One:

This is the day I brought it home, it ran good, but had a stumbling issue that was known when I bought it. Previous owners cleaned the tank, new pump, you name it. Got it running better but there was still some hesitation.

Pics:

http://farm6.staticflickr.com/5453/7...f1e6f423_z.jpg
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Reserved

Looks like you can't edit posts...so...lol.

Anyway. After I got it home I did some small things to it and decided to run it at the HSR Atlanta Historic Races in September. First things on the list was to clean it up a bit, so I removed some decals, touched a few areas up with paint, and washed it:

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After the cosmetic stuff I fixed a few small things and put a OMP blockoff plate on to pre-mix.

Getting ready for the event I also cleaned up the interior some, put a new harness in the car, new padding on the cage around my head, and that was about it really.

I decided to just run the car as it was to get a feel for it, using the HSR weekend as a "test" to see how it ran and how it drove.

http://farm9.staticflickr.com/8030/7...10960404_c.jpg

My first session out sucked, I stuck all my Diamond Racing wheels on which I bought with fairly new Toyo unshaved tires I bought in case of rain but were in better shape than the R888s on the car, as I pulled down to grid my "crew" noticed the wheel was wobbling bad and was either loose or bent. Ended up being bent so hurried and went back to throw two Panasports on the rear.

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I did get out there though with some time left. The car handled great! I was very surprised. I took it easy just getting a feel for it, biggest headache was the stumbling issue coming out of corners and sometimes on straight aways, it really limited the car. The other issue was a bad vibration above 70 or so, so I kept my speed down to around 85 tops, which sucked especially on the backstraight.

Second session went better, I went quicker and started to get more out of the car. Handling wise it felt very neutral.

Third session on Sunday was the best, because I fixed the issue. It was just the vent solenoid unplugged on the carb, plugged it in and the car ran smooth! The only downside is it "feels" slower now, not sure if it's in my head or if it really did lose some power.

In the final session I went fastest and had a blast. Car ran good, no issues engine wise.

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So, reflecting on the weekend, here are things that concern me and I'm looking for some input if available:

-Vibration. Wheels out of balance? U-joint? I plan to replace both, but any ideas on what else or anything else to check?

-Low power? Get the carb tuned? I know the floats were messed with by the PO when they had fuel issues.

-After my final run on day two things got weird. Actually before and after. Before, as I went to back out, the car would not roll. I felt like something was broke, but I just forced it back and it got smooth. During the session it was fine. On my way back to the paddock, I felt a heavy pulsating vibration through the shifter, I thought it was possibly pickup from the tires or something. I drove it around a while later in the paddock and it was smooth again. The next day, I started it to warm up and once again, I got that feel through the shifter, but then it went away again. That time it was at idle.

That's all the issues I can think of right now. We're running it in a month at the SCCA American Road Race of Champions in the 3 hour ECR enduro as well as the test day, so quite a bit of track time. I'm hoping to have any issues resolved.

Nice. It good to see a car getting used the way it should be.

Nice looking car!

Vibration issues - some thoughts.

This can be caused by wheels being out of balance or by the drive shaft....or both.

An out of balance wheel(s) will vibrate in a consistent manner and get worse as speeds increase. If it is a front wheel the steering wheel will shake. A rear wheel will be felt more in you seat. All wheels/tires should be balanced.

If the steel wheels are made by Diamond, they will not be hub centric. They need to be balanced on a machine that references the lug holes and not the center hub. This something Diamond recomends on their site. Nothing wrong with the wheels.....this is just how they are.

Driveshafts in RX7's have a harmonic issue and they will vibrate. Even a brand new driveshaft from Mazda (I have one) will vibrate at a specifc RPM. Bad tail shaft bushings in the transmission will make this worse. So will too much pinion angle on the rear end - set the pinion angle at 0 degrees when the car is at ride height.

In my car the driveshaft vibrates from 7600 to 7900 in 4th gear. Over 7900 the vibrations disappear. The vibrations get worse as the trans/rear end heats up later in the race.

With a new driveshaft and new rear tail shaft bushings the vibrations are not that bad.

Thanks!

The vibration only really starts around 70mph, until then, I feel nothing, then it starts to vibrate and gets fairly violent. I thought wheels but with all four Panasports on, it did it, then with the front Panasports to the rear and two of the Diamonds up front it still did it without any change. So although I'll still have them balanced anyway to be sure, I'm now sort of thinking it may be something else. I bought the Diamonds from another RX-7 racer, not sure if he already had them balanced I know he ran them, but I'll take them in anyway.

What's the pinion angle?

The only vibration I get below 70mph is right when I'm pulling off, I originally thought that was a driveshaft thing, which I guess still may be and could be really showing it's head at 70+?

Thanks for the help! :icon_tup:

nice car! i wish i could run HSR, my car happens to fit their rule set perfectly, out west they won't let anything newer than like 75 race unless its a porsche.

oh and BTW we're (japanese) twins (basil), my car was a blue non sunroof car turned Pro7 too. https://www.rx7club.com/build-thread...eepers-854956/

for the vibration, it sounds like a U joint, but make sure your tires are round too, sounds dumb, but they do not always wear round.

Thanks!

Yeah I originally thought tires, but the ones that were worst warn weren't on the car and the fronts are practically new.

I'm going to replace the u-joint for sure and see what happens.

Small Update:

Getting started on car prep for the American Road Race of Champions which is not too far away! I'm getting tires mounted on my Panasports tomorrow and having them balanced. I don't feel any play checking the drive shaft so I'll try balancing them first, then go from there.

I'm also about to order new rotors for the car, I'm new to this whole replacing the bearings deal with the rotors, is it hard? Here is my list, do I have all that's needed:

2 Front Rotors
2 Rear Rotors
2 Front Inner Bearings
2 Front Outer Bearings
2 Rear Bearings

Is there no inner/outer for the rear?

As I'm getting the brakes done I'll also change transmission and differential fluid.

More to come with some photo updates of my progress.

Another option is to build yourself a 2 piece tailshafts. This is how Mazda over came the issue in there race cars, was a factory race part.
Here's pic and some info..
Rx7 Tailsharft # 4352 25 100 and Centre-Bearing Support # 4352 25 300
This is a special two-piece drive shaft with a centre universal joint and support bearing. It has been designed to move the resonant frequency out.
Pic's show the differences between the Rx2 tailshaft (on the right)
https://imageshack.us/a/img220/2933/mfrrx2tailshaft.jpg

Pic's show the difference between the centre bearing (Rx2 on the right)
https://img716.imageshack.us/img716/...lshaftjpg2.jpg
https://img41.imageshack.us/img41/98...lshaftjpg1.jpg

So we ran the 2012 American Road Race of Champions this past weekend in the three hour enduro. We ran my Mazda RX-7 in IT7.

The week was a rough one leading up to it, I had brake issues (found a leaking caliper, then a bad master, etc) which kept us from doing the test day Thursday, which was going to be primarily a benefit to my co-driver as he has never driven the car. We missed it, so qualifying Sunday was his first time in the car.

From the start, we had transmission issues. At first it just wouldn't go into gear, it finally would after some banging on it, then out on track he had issues getting to 4th, etc. I sent him back out telling him to double clutch and just get the car warmed up and he said it felt better.

The race came around and the rain started, luckily we were starting on un-shaved RA1s which was a huge benefit. I think we moved up to like 12th overall at one point just from consistent lap times and not having to pit because of the wet.

My co-driver ran an hour and fifteen minutes or so before pitting for me to get in the car and fuel, now the transmission was worst with 4th gear pop out and some other weird sensations. After a few laps with me in the car I had to drive holding the shifter in gear, it was the hardest thing I've ever done in a car. Let me tell you, driving one handed at Road Atlanta, especially through turn 12 is not exactly fun. Especially in a race with different classes and some very fast cars out there. That's a lot of things to be doing at once. lol

After a half hour or so it got bad, all gears felt like death, they would slip out, couldn't find gears, etc. Going into T1 I fumbled for a gear, couldn't find one, I started running out of road at quite a bit of speed, saw a pack coming up behind me and decided to just open up my hands and go off. It was a rough off but I managed to keep it straight and not hit anything. lol I finally found a gear and continued.

I let my friend finish the race, by the end he was only using 3rd and 5th, but the car made it, the transmission is destroyed but everything else ran great the whole race and we got 1st in class...out of one. But hey, finishing an enduro is half the battle and finishing with a car in bad shape makes it 20x better.

Here are some pics:

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Some fun Saturday night, making the final touches.

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Pics from post race impound:

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Great job. That sounds stressful.

Nice, welcome to rx7 racing. I run an 83 it7 in great lakes division. Hopefully make it down to the arrc this next year

So a little update for my "build."

So far I've bought one transmission, going to buy a second as well.

I ordered a Paul Yaw Nikki today and a 7s Only tuned carb as well.

New seat ordered:

http://www.kirkeyracing.com/images/T...GHT_Medium.JPG

I had the hardest time trying to figure out some mirrors, my passenger side mirror is electric and there's an electric switch on the dash, so planned on trying to get electric mirrors and make them work. Found out there's no real wiring. Drivers door mirror vibrates no matter what I change, so I just found some cheap roll bar mirrors and had to get some other mounts to try and make them work. Spent about $30 when said and done, better than the $80ish for them as a real kit. Tight budget remember!

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Also picked up this jewel:

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Along with my mirror, I also put a wink mirror in with some "custom" mounts. Who knew they sold mirror mounts at Wal Mart?!

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I also picked up a right side window net for some added safety.

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Can't forget a water bottle holder for those hot southern summer days!
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I also decided enduros may be better with some form of real communication versus a pit board and random unexpected pit stops. I won this in an auction, radios will be replaced with something a little better but it should do the trick and I got a killer deal on it.
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I also threw the weird spoke Grant out for a regular 3 spoke Grant, please excuse my mess.

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More to come soon as we tear it down mechanically!

UPDATE.

Got the new seat in. I LOVE it. I'm still debating whether to buy a cover or buy a lot of padding and sort of make it fit me. Price wise would be about the same. Either way, here it is. MUCH better than the Kirkey that was in there and MUCH more protective feeling.

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Excuse my mess, I plan on painting/stripping sound deadening last once all the important things are done.

I guess next up is transmission stuff.

I also had to order a new idler arm, found mine to be 100% shot the other day when I was about to take it to a friends shop to start the transmission work.

Looks awesome so far, subscribed :biggrin:

UPDATE.

After a long winter I'll finally have the car back out on track this weekend. Fingers crossed nothing happens.

We just did a LOT of work to it such as replacing the transmission, clutch, all associated items, suspension bits, and tons of just small things here and there to make the car more reliable and what not. Of course half of these simple things turned into complicated things so a simple slave cylinder job ended up taking 3 hours because of a bolt size issue, just small stuff like that.

Finally making progress:
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An example of what came out of the old transmission:
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New transmission ready to go:
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Long nights:
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We made this cool setup to add transmission fluid without causing a mess from a hand pump. We drilled a hole in the tunnel where the fill plug is, then ran tubing, a 90 degree bend, and more tubing into the transmission so you can just pour it into a funnel from the interior. Worked like a charm.
http://farm8.staticflickr.com/7288/8...13c1f5a6_z.jpg

Anyway, that's it for now I'll post more later and updates through the weekend. I'll have some video as well with lap time overlay courtesy of Harry's LapTimer.

UPDATE.

Got the car on the ground, got it running, and drove it! Easier said than done though. It did not want to start, we had fuel (too much) and spark, but it just kept flooding over. We finally figured it out and got it fired up then I held my breath and went through the gears, luckily they all worked!

We got the car down and I took it for a quick test drive, I never knew these transmissions could be so smooth. After the last time I drove it this felt like slicing butter. It ran good, transmission shifted smooth, clutch feels good. We're ready to race...I hope.

The rest of the day was spent tightening up odds and ends, cleaning the car, etc. I'll take it to the track tomorrow.

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UPDATE.

We took the car to the track today, before leaving I ran into hopefully the last issue of the weekend, my kill switch went bad causing the car to cut on and off, luckily I caught it early, sourced a new one from a vendor at the track, and got it back together quickly.

We go out at 8am tomorrow morning and have three sessions, 50% chance of rain, I'll run rain or shine but prefer shine primarily because I don't want to sit around in the rain. lol

Ready to leave the shop:
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Kill switch swap:

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My Volvo wagon makes a great support vehicle. :P

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Ready to go:

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Fingers crossed we have a fun and clean day tomorrow.

UPDATE.

The first session our Saturday was damp, so I mainly took it slow and just got a feel for the car again and made sure everything was working properly. Everything felt good, the transmission was smooth, and I was ready for the session after lunch.

Session two was now completely dry and I immediately went almost two seconds faster than my previous best time in the RX-7. Still very underpowered on the straights I could make up a good amount of time in the corners. Session three was even better with another half of a second shaved off of my previous time. I was happy, the car was running good, and I was excited for Sunday.

Sunday came and so did the rain. A lot of rain. Enough to flood quite a bit in the local area specifically Flowery Branch. We arrived at the track wet and early and I knew the day would be a rain fest and I wouldn't be able to keep shaving time off. I would however get valuable experience in the wet. The first session out was soaked, there was standing water in turn one, the esses, a pond on the entry into ten, and a river running down the hill from eleven into turn twelve. It made for a very exciting session mixed with hydroplaning down the back straight and a game of throttle control and smooth steering inputs. I had a blast in all honesty, speed wasn't high but it was a lot of fun and I learned a lot.

The second session was also wet, although not as rough as the first. This was the last session of the weekend so my main goal was to just have some fun and not screw anything up. It was once again a blast sliding around in the wet and a good conclusion to a fun weekend.

Videos: (MAKE SURE IT'S ON HD!)

Sliding in the rain:

Camaro losing it:

Mowing the grass:

Dry lap:

Our next event is still in the air, I may be able to fit another in before my wedding but if not August for sure, then a 6 hour NASA enduro at Road Atlanta in August. Before the next event I have a very small list of things to do, which is nice since last time I had a book of things to do!

A few photos from last weekend:

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Beautiful! Rain is a blessing when you're learning a new car or track! Speed will come. I love that place, was lucky to have a track weekend there back in '95.