Andrew7dg

Got the FB Running and went down to the local Rally X to drive the course. I am now addicted! RWD is not that fast (or I just need to learn how to drive it) but driving it is a lot more fun than I thought.

I was in stock RWD class. This is my first time out there with this car.

I think I would like to go into modified class and see if I can run with the bigger cars. The main comp is the BMW E39 325s. However I think my car is lighter and with a fresh set of snow tires and some more experience I may have a chance.

Who else has done this and what have you done to your car to make it more competitive? and has it worked? and what hasn't worked?

I threw in a 83 LSD in mine before the event and I am glad I did. It made the car a lot more predictable and launched it off the line quicker.

rwatson5651

iTrader: (5)

Check post by peejay. I think he is the resident Rallycross expert.

peejay

But really, I drive anything that has four wheels and passes tech.

peejay

Oh yeah, what works:

More spring rate in the front. (Prepared-up only) Don't take off the front sway bar, seriously! Ignore the people that tell you to do it. They don't know RWD. If the front suspension doesn't handle the main anti-roll duties, you get a nasty uncontrollable snap oversteer mid corner and you also can't exit corners well. People who pull front swaybars are trying to tune around a driving problem - the problem of not driving aggressively enough.

Drive more. Enter more events. Learn something every time. Make mistakes and honestly analyze what went wrong. RIDE WITH FASTER PEOPLE AND LET FASTER PEOPLE DRIVE YOUR CAR. Seriously, this is the #1 thing ever.

Andrew7dg

Lol, I own a miata as well! I guess I am going to have to try that out at a course also.

I took a look at your mod sheet peejay and very impressive. I have all sorts of questions! I have decided to be on the modified rwd class because I have already the exhaust header which is a modification. Might as well go off the deep end.

I was going to ask you if you liked the half bridged port or the full bridge port? I have 12a right now woth no intention of switching to a 13b yet. I was going to try to buy another carb and modify it over the winter (hogged out Nikki as it is called?). I am not going to trailer the car to the track so it has to have some streetable manner.

I am glad you did tell me that about the front sway bar as someone did try to tell me to pull all sway bars. The front one sound important (stock sway bar or heavier?). What about the rear? Is that one still important? Some people it sound like they pull them for autox

Later modifications I plan after I have a couple races experience(and please comment on how they worked and if it is highly recommended or not)

Tri link setup with pan hard bar
FC sub frame swap

I have been a welder and a fabricator so pretty confident that I can do these mods

Thank you for the replies!

peejay

Try the rear bar both ways. It's very easy to remove and install. But definitely keep the front bar until you're able to increase the spring rate up front. I don't have a bar up front because my suspension precludes it, but my rear suspension can also be articulated with finger pressure.

Definitely the full bridge is better than the half bridge. It pulls from lower and makes power higher. But part of this is also the intake setup i have and a lot of careful ignition tuning.

I'm curious as to what "spec sheet" you found... my car has changed significantly since the last time i made one

Black Rocket tires are awesome. So awesome that I started breaking axles. Oops.

That Miata isn't mine... that's my friend Evan's car. He kinda won MR at the championship last year and placed a painfully close 2nd the year before. This year I spent driving everything BUT my car because of the axles problem. Evan's Miata, Evan's Subaru, another friend's Subaru, my Volvo... I miss driving my car

Jeff20B

iTrader: (13)

peejay, you have a bridgeported 13B with EFI, unless things have changed. Andrew7dg is wanting to keep his 12A and do a hogged out Nikki. Perhaps, for him, a half BP is the better choice? Being carbed, and all. Your thoughts?

peejay

The last time I made a spec sheet was in 2014 but that one never went online, it was hastily scribbled out five minutes before Class Inspection and then I threw it away when inspection was over. The last time I posted one was in 2011. I've made a few changes since then

IMO you need EFI for both. I never went full bridge with the OEM injection manifolds because I didn't want overlap on the injectors if they could blow into a plenum. Thus why I went to a Holley manifold and throttle body - I can have all the overlap I want with excellent drivability because the distance from port opening to the "end" of the intake tract (the closed throttle plate) is relatively small. In fact drivability got better compared to a street port or half bridge on the EFI manifold! I'm sure that part of this is because my MS runs batch fire and I'm only running one injection per revolution. (I have never had an OE-injected RX-7 - I went straight from carbs to Megasquirt in ~2008)

Carbs are great on stockport engines and even street port, but anything raunchy really needs EFI to be drivable. It's just too much PITA to make a carb do what you want it to do under the awful conditions you force upon it down in the 5-20hp part of the power spectrum.

Also, I'd leave the Nikki alone aside from minor details like removing the secondary diaphragm spring. "Hogging out the barrels" does nothing useful for you aside from make you have to chase tuning problems. Stock works really well, and working really well is a lot better than something that bogs and spits back and upsets the chassis when you whack the throttle at 3000. At that point, any theoretical gains you might get from more power are now LOST. You're chasing your tail.

Jeff20B

iTrader: (13)

Oh, ok. So maybe a half BP with a Nikki is a no go.* But I can say that a hogged out Nikki with modded air bleeds works awesome on stock ports up to 74 spec ports. Gonna try for street ports next.

I can also floor mine with mechanical secondaries at 3000 and it pins you back in the seat with no bogs and no delays. I can even slam it at 2000 but it just sits there and sounds a little more throaty (no bogs) until it reaches 3k, then it takes off.

I guess it wants 3000 with 74 spec ports. Stock ports could probably do it at 2500 and street ports might need you to wait until 3500. Or not. Greater volumetric efficiency could result in something other than what I think it could. I'll just have to try it; streetports.

*I've tried a half BP 12A with a stock venturi Nikki before but it wasn't as nice as my 74 ported 13B with a hogged out Nikki. I'd still like to try another half BP but don't really want to ruin a set of irons.

wankel=awesome

This describes mine perfectly. And its a direct copy of Jeff's "Hogged Nikki".

Andrew7dg

I used to be a co driver in stage rally. I am familiar with the Black Rockets. They have a square edge for good cornering and I imagine that they would work good for rally X. We had a problem with them at high speeds. They are kind of unbalanced and require lots of wheel weights. They are also HEAVY so I can't imagine why you would brake axles.

Speaking of axles, I am guessing you have the GSL-SE axle which should be the stronger of the axles. Do you suspect that Rally X is hard on the axles? Are you going to switch to something bigger? And judging from the 2011 mod it looks like you went with the tri link setup, How does the 3rd link and the car support take the abuse? I have been a welder/fabricator so doing this mod isn't that tricky for me.

Right now I have the GS with the GSL Diff running 13" Snow tires. I think it is working pretty good except that whenever I make a tight corner I get some noise from the diff on pavement. I have heard that these diffs do need clutches in the regulatory though.

If I may inquire about your 13b motor, 13b full bridge, on a 4 port motor? and that is running a Holly intake, which Holly Throttle body injection?
Did you do the porting yourself or did you find a template?



So it sound like the plan for right now,

Fix the carb up to get the most out of the stock port 12a (keep reading the post by Jeff)

Buy new snow tires,

Try with the rear sway bar on and off to see preference

Fix up front end with polyurethane for no more rattles

Drive, drive, and drive some more and have other better drivers drive the car to see what they are doing.

Future (and you can help me order these in what you think are important)

Increase spring rate in front (280 to 320 range)

Switch to an FC front sub frame for Rack and Pinion, lower control arms and struts

Find different rear end and find some lower gear sets

Find another rim size

3 link with pan hard bar

Bridge port the 12a or find a 13b

I am sure I will find other mods along the way...

peejay

Okay, stage rally experience. Awesome. I went from Michelin ZE70/80 tires in 17-65-15 to the Black Rockets. The Black Rockets are a lot lighter

I didn't start breaking axles until I went to the BRs. (Surely it can't also be the extra power I got from some mods over the winter, and a new driving style that emphasizes acceleration over all else) I was wearing out the axle bearings a lot and twisting/bending housings too. Oddly enough when I broke the first axle, it was a left side axle and it was at the same event where I broke one of the housing braces - on the left side. I changed both axles and won my next event but broke another axle (right side) on the way to the one after that. When I pulled the axles out to swap in the unbroken (but twisted) axle from the first go-round, I found that the one that didn't break was twisted a full axle spline and was ready to break too. So I replaced it with the less-bad axle and kept the car one wheel drive until my final solution.

Which is a 9" with 31-spline axles (wishing I sprang for the 35s, actually, they aren't MUCH bigger than the 26-spline Mazda units) and we'll be putting a backbrace and lower brace on it.

I have been 3-linking RX-7s since... 2006? It was originally an expedient way to fix a rusted car, but it works SO well when done right. With

If it just makes noise, you need to shim it tighter Mine would bark and make the car jump around on pavement.

[quote]If I may inquire about your 13b motor, 13b full bridge, on a 4 port motor? and that is running a Holly intake, which Holly Throttle body injection?
Did you do the porting yourself or did you find a template?

No, a Holley carburetor that acts only as a throttle body. Two 1000cc injectors on a GSL-SE fuel rail. My engine is basically GSL-SE with 12A end housings and a S4 N/A rotating assembly.

I found the limiting factor to be the engine, myself. Get a RB long primary exhaust system. It's quiet and very good for power. They do rust out after 15 years though Mine actually is for a 12A, I cut the rear header tube off at the rear flange and shortened it so it'd bolt up to a 13B.

Not worth it unless the control arm bushings are shot. Do NOT do the tension rod bushings.

Not that much... 175-250 or so depending on factors. I have 175s right now. Stock is ~110.

This was a step backwards, IMO. I mainly did it because it was cheaper than sourcing a new power box, since mine was toast.

No on the panhard - it isn't as strong as the Watts. I have a simple brace going to the center stud and that's it. I broke my Panhard at Nationals in 2011.

Andrew7dg

Yes, let me know if you have any questions about going over to the dark side!

I live in Minnesota so I have been to Ojibwe forest rally, LSPR, 100AW, almost made it to snow drift, Magnum Opus (Nasa event), and a handful of regionals that pretty much run on sections of the national circuit.

It feels a little backwards going from Co Driving Stage rallies to being new to rallycross but it is putting me in the drivers seat and in a RWD car. It is so much fun to drive.

Maybe, just maybe I might cage this car... once everything is sorted out. I just want to have fun with it right now.


I am curious about this as the car I was in was a FWD and wonder about the comparison.


Interesting, I have an 8.8" sitting in my garage.

It looks like I am going to have to find a solution around the Watts link for the 3rd Link as it is in the way. Just looking at the 4 link, it looks like it would bind up and I believe that is why people get snap oversteer on the car. I would really like to put that 3rd link in and I have the fabrication experience to do it.


Really? I would have thought that the Rack and Pinion with the stronger A arms (and also a bolt pattern that is different than 110x4 would be a better benefit. Plus better strut and spring options.

I want to thank you for answering my questions. This has changed my outlook on how I am going to build the car up over time. It is good that someone has been down this path and is willing to share their experience.

peejay

The front roll center in the FC is lower, which makes the handling go all wallowy. It's not as responsive as with the FB front end. And the struts have a LOT less travel. I went from 175-200lb springs on the FB to 250lb on the FC to both deal with the roll center problem and the reduced travel.

Now I have super long front struts that I fabricated, which raises the nose (and therefore the roll center) and gets me back the travel, so I can go back down to 175lb springs...

My 3 link comes up through the floor. Clears the Watts just fine. Of course, this is a Mod only modification.