Revamping the Rx7

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Carl S
Wouldnt a shit-ton of anti-squat tend to remove the compliance from the suspension and cause it to skip over the bumps and lose traction? Just from watching the f cup videos it seems that everything rwd sits down in back when they get on the gas, not much anti-squatting going on. Just curious.

You'd think that, and I tried zero squat, and it tramped horribly over rough stuff, so I kept adding anti-squat and it kept getting better and better.

I don't question it, I just do what works, you know?

so i got to measure i little between moving and all that before i left. I wish i would have gotten more time to tinker but i got a measurement of the 1.9" and i think that was from "rest" with my jacking the body of the car up until the axle came with it. And that about sucks. Over all travel has to be less than 5". Which also sucks. Since there is hope of a renewed log book (3 spots left in the SCCA one) i will likely go forth and four link / volvo axle the thing after the 2012 season.

Ordered the .625 Wilwood master cylinder for the hydraulic handbrake (buying the CNC one here soonish).

Probably ordering the Hybrid neck restraint here soon as well. Mostly since its a big expense.

Ordered my Hybrid Pro today along with my race suit. So the big safey expenses are out of the way (mostly). The helmet is up in the air just thanks to waiting for Peltor to release a new standard...

So i find myself in a debate between using the stock ecu and wiring harness to run this engine and running the megasquirt. I have a megasquirt that will run with the distributor and i would just need a wiring harness for it. Whereas, i have the stock ecu and MAF and i believe i even have an engine harness laying around. The car isnt really THAT modified but tuning but be worthwhile considering. But the ease of running the stock crap would be nice. Thoughts?

If you are proficient with building wiring harnesses then go for it, but if not, reliability always wins in rallying.

i think in the interest of time ill just use the stock ecu and wiring. It will just go together with less problems. Car just needs some minor things from here really.

There are so many other things to worry about in getting a rally car running and through a rally, I'd go with known-good stock stuff to start. If you want tuning flexibility later, there are plug-and-play megasquirt options that use the stock harness, so you won't be taking any steps backwards.

-Dave

The problem is 25 year old harnesses that are probably junk. Hell, a lot of them were junk 15 years ago.

I'm all for megasquirt. The trick is don't do anything fancy. Buy a prebuilt flying lead harness, run all of the grounds through the firewall and ground them at the engine (like the factory does on 99% of all cars made), use new sensors and connector pigtails instead of junkyard garbage, etc. My thinking is to also just use a damn distributor and an MSD to give the computer its signal, I've had exactly zero RPM noise issues with doing this. It gives up on power and fuel economy but, on the other hand, zero problems is even more important.

I only ever had ONE problem, and that was because I was running low impedance injectors at 75% PWM and a max duty cycle of 95% or so, for something like 50-60,000 miles, on a used 1.01 board which has known PWM transistor problems, and I *finally* killed the transistor. So I wired in a resistor block, reset the computer to not use PWM, and kept on truckin'.



Edited 1 time(s). Last edit at 10/30/2011 03:21PM by Pete.

While I kinda disagree about the likelyhood of Miata harnesses being junk, the more I think about it, the more they would be a pain to swap in. Mazda doesn't tend to do separate engine harnesses, so you'd almost have to swap an entire Miata wiring harness into the car. Depending on the condition of the RX-7 harness, this might not be a terrible idea, but it does change the equation...

-Dave

well i elected to use the 13B i had due to cost issues, so the miata isnt in the car. A rotary is, and those harness are a touch old and rather cooked from heat over the years.

by flying lead harness are you taking about that thing DIYautotone sells that i just wire the connector ends too?

Well, look who wasn't paying attention...

well if i dont have MAKE the harness, and just pin the wires to connectors, that wouldnt be so bad. My issue isnt so much funding, its just time. I would likely then run the distributor on an MSD box (setup the car had before really). I HAVE a megasquirt from my silver car, and it worked. Only problems i ever really had was a floating TPS issue. TPS max value would change all the damn time for some reason....

my biggest concern is still travel (suspension). Especially the rear. Its terrible. And outside of cutting and welding to redo the links, i see no way to improve upon it. Depending on how Idaho goes, i might just say screw it and do just that. Run a Volvo dana 30 axle and buy some links get to it. Probably wouldn't be TOO hard really.

Idaho is at least very smooth so i can get away with my weak 5" of travel in the rear. Seeing the results from previous owners, id say the car will still do well, but i bet it would be damn good with improvements.

and JVL, i PMed you a few times. I need some green front suspensionage!

Quote
Gravity Fed
my biggest concern is still travel (suspension). Especially the rear. Its terrible. And outside of cutting and welding to redo the links, i see no way to improve upon it. Depending on how Idaho goes, i might just say screw it and do just that. Run a Volvo dana 30 axle and buy some links get to it. Probably wouldn't be TOO hard really.

Idaho is at least very smooth so i can get away with my weak 5" of travel in the rear. Seeing the results from previous owners, id say the car will still do well, but i bet it would be damn good with improvements.

and JVL, i PMed you a few times. I need some green front suspensionage!

Back in the day........I ran a very fast RX-7. Pretty well had my way with all the local competition and many of the national guys. So did 3 or 4 other 7s of that era. That was pre-Sube days but we still beat up on GTX and Talon with regularity. I never felt handicapped by the rear suspension. Keep in mind the car is pretty light and you can get by with a bit less travel because of that. I don't remember my spring rates but the factory rally springs were a bit stiff and caused the cars to jump around too much on gravel. My car was about an inch higher than stock, I re-worked one of the watts linkage bars and made sure all the trailing arms were tightened at rest rather than droop. Or you can go the Hurst route and make the 3 link rear suspension. For Idaho and learning I'm sure you will be fine with the stockish suspension.