ZX14 Super Seven, finally finish and tested

[Gabriel]

I posted this on the racing section but it might as well be here since I finally have this car finished. So I took my car to the track for the first time ever. I myself had never been on a race track and it was such a blast that I can't wait till next time.

So a little bit about my car. I started this project in 2008 and finish in 2014. Yeah it took a while, I had no kids when I started and now, 8 years later I got four. The car was on the back burner for quite some time. Anyway I finally finished it in October 2014 and drove about 2000km since then with no issues. I use the book size for the frame with a few mods for the IRS and I wanted a full roll bar. I used the brakes, the diff and the steering rack off of a Mazda RX7 GXL. I build my own suspension and used QA1 shocks and Hypercoils with modified RX7 spindles.
For motor, I wanted something small and light and found a almost new Kawasaki ZX14 with 1300mils on it.



On the track I notice the the car was really tail happy. I have Yokohama A048 up front and Yokohama A008P with doesn't help the back as those are street tire and the front R compound. But I notice that the car would start sliding in deceleration as soon as I would give it steering input. So I think that the LSD that came from the RX7 is the problem. It's a clutch type limited slip and is pretty much always lock up.

I don't known if others have had similar issues but I was expecting the Seven to be really fast around corner and that's where I was the slowest.
As far as balance my car is rear heavy, it weighs 1176lbs with me in it and half a tank. The rear is about 700lbs and the front 500lbs. I notice that can was sliding around even more on the track when I was by myself so it's probably not a balance problem.

Anyway here is a few pictures of the track day.

[nick47]

Great-looking car. Nicely done!

[Tundra 7]

Love the "R's" in the video. Very cool. Sweet car.

[Gabriel]

Thanks man.

[dfdahl]

That's awesome man, Looks like you could use a little more rear roll bar too.

[kreb]

Man that's light! Is it dry-sumped? Nice work.

[locofinn]

I notice that can was sliding around even more on the track when I was by myself so it's probably not a balance problem.

Add more tire. Very nice build

[trialsmangasgas]

Sweet car!!! Did you make the sun visor? That might be an Item I could use in my car. Russ

[Lonnie-S]

Yeah, you've got a really nice car there. Thanks for the video and the photos. And also, thanks for the time line info. I'm heading into the kind of build time you had, so it's encouraging to see what the end-result can be if you stick to it.

Cheers,

[wrightcomputing]

First of all congratulations on your first track day and it looks like the car ran great, The engine sounds amazing.

On the video I didn't notice oversteer apart from that one corner at the end. It could have been driver error as it was your first track day. With the car being rear heavy you are going to get lift off oversteer and it will want to rotate when cornering. To stop the rotation you need to add gas to get the weight to transfer to the rear and increase grip. Most beginners release the gas in this situation which actually makes it worse.

Here are some basic tips to reduce oversteer. Lower the rear end (reduce rake), soften the rear springs, shocks, sway bars and tires. You can also raise the front and stiffen everything of that is easier. At the track you should stick to tire pressures and shock adjustments to balance the car.

You ALWAYS want the tires with the most grip on the rear. Get the same or similar tires all round before you commit any other money to fix the handling. Good luck and enjoy that great car.

[wrightcomputing]

I just watched the instructor run video and the car is definitely loose. What alignment setting are you running. I would probably start with 1-2 degrees camber and zero toe in the front and 0.5-1 degrees of camber and 0-1/8" toe in at the rear.

If you get serious about track racing the you should get a pyrometer and check the temps across the tire which will let you know how to adjust the camber and tire pressure to optimize the contact patch of the tires.

[papak]

You might want to try an inch wider wheel/tire combination at the rear and /or raise the rear tire pressure 2psi to start. You may be able to dial out the oversteer with tire pressure but 2-3 psi is about the range you can work with before you need more tire.

Just my 2 cents

[Gabriel]

Thanks, guys for the tips, I'll get myself new tires for the next lapping day and see how it behaves. Wrightcomputing, I'll have to try to give it some gas if it's want to rotate next time and see what it does.

Russ, I made that sun visor out of 3/16 Lexan, I had to made something when I did the inspection. It actually doesn't do anything for the sun but it's a nice wind deflector.

Here's a couple more picture of that track day.

[Gabriel]

More pictures...