Yeah 1+ G is a benchmark I'm aiming for as well. I know I've experienced that before on Laguna Seca riding in a Porsche 911 on slicks. Just amazing how well that car gripped... especially while braking. It was like throwing an anchor out the back.

Racetrack tarmac is very smooth and sticky though. Not at all like the crappy street surfaces we usually drive on. 1+ G on street tires is possible sure, but it largely depends on where you're driving.

For now yes, but I will be modifying my FB to this extreme as well just wait and see lol

Yes there is no doubt the double-wishbones provide a better contact patch for the tire... I had a few MKIII Supra's and I drove an FD a few times which also have that setup.

However imo there is sometimes more to be said for the MacPherson in terms of feedback. It's like a tuning fork for the tire it really picks up all the minute sensations from the road. I found the driving experience of the FD RX7 and the MKIII Supra a bit more numb in that regard.

Don't get me wrong, I'm not saying the cars were any slower in my hands because they weren't MacPherson. It's just that I was slightly less confident about what the limit of the tire was, and were not even talking about a big difference. Maybe 10-20% less feedback felt like to me.

On a track that difference wouldn't seem so big, but on a mountain road with a generally lousy road surface, with no runoff areas, feedback from your tires is everything.

Yeah I am also very interested to learn about what has been tried and done on high performance racing FB's that were not so limited by class rules. Millen's RX7's, and those group B FB rally cars for instance were pretty extreme.

It's what I'm shooting for, doesn't mean I'll get it. :lol: I'll give it my best shot anyway. I don't know about the feedback issue, you may be right on that. I wonder how much of that is due to the weight of the car though, the FD and especially the Supra aren't exactly lightweights. That's the biggest reason I chose the 1st gen over the FC and FD chassis. (I don't actually hate the other generations, just returning the harassment others have dished out :)) The first generation RX-7 was ridiculously light for a street car. I thought about going with a swapped Miata for this reason, but the RX-7 chassis should be stiffer than the convertible chassis and there is very little difference in their weights.

I know the SLA suspension will keep the tire in better contact with the road, providing more ultimate grip. So between the grip factor, and the need for tucking in large rubber, I decided to go this direction. A widebody with an increase in track width would have been more effective, but I want to keep it approximately stock in appearance. I would imagine that a widebody would get a lot of scrutiny from any law enforcement in the area. Between the large rubber and my upgraded brakes I should get pretty decent braking performance as well.

As you said there is a big difference in quality of the road surface between a racetrack and normal street driving though. Race cars can get away with a lot of things that won't work on the street. I'm trying to come as close as I can to that level of performance without losing the ability to drive it regularly.

Yeah a Supra is a heavy beast but weight is not always bad. A Supra is not a flickable or tossable car but it turns better than you might expect. There are lots of heavy cars that can manage 1+ G. More weight on a tire (to a point) creates a greater coefficient of friction and helps grip. More weight allows for more static grip in the tire, as well as more weight available for weight-transfer in grip driving. But of course, more weight works the tire harder so it wears and possibly overheats faster.

There are many great cars in the world that are heavy but through clever engineering actually make that extra overall curb weight an asset like the GTR.

In the general sense of performance, the ratio of power to weight is more important than the actual power or weight numbers themselves. In the truest sense of performance though, power is king as long as you can find a way to put all that power to the ground. That's what makes cars like the GTR and 911 so impressive.

My bridgeported RX3-SP, fully caged with a Ford 8.8" rear end in it was in the 2300 lb range when I corner weighed it. But so what? That car had no traction. When I swapped its engine in my FB (just a street car with a full interior) I was actually able to put the bridgeport power to use. The FB was way faster, but on paper it should have been slower.

That's exactly my goal as well. I drive sports cars not just for fun, but because I know they can out handle and out brake those other cars with incompetent drivers that cause accidents all the time in urban areas. Or help me dodge the grossly overpopulated deer population in rural mountain areas.

:cheers2: Funny you should mention deer as a very close encounter is what started me down this path. ;)

A lot of the RX-3s problem is that the stock suspension on those suck. They were designed as an economy commuter car and handling wasn't really in the equation except as an afterthought. The FB didn't weigh all that much more and even the first gens suspension was a vast improvement over the earlier cars. My SA weighed in at 2340 with everything in it and a full tank of fuel before I started modifying it. Hopefully I don't add too much weight to it, but I'm sure I'll add some. :gnorsi:

:)

Great thread, I'd love to see what exactly you have in store for the motor later.

Thanks. I'm not quite sure which way I want to go on that myself yet. I'm trying to get all of the supporting hardware in place first. I will be shooting for the 350 HP level and staying rotary, so it will probably be a single turbo 13B REW based engine, we'll have to see when I get to that point. :)

While I was off playing farmer, I'm temporarily home as you can't cut corn in a snow storm, I ordered the upper A arms and hardware from pitstopusa.com. The parts are already here and exactly what I ordered. Which for those of you that know of my supplier travails, came as a pleasant surprise.

http://farm4.staticflickr.com/3670/1...2c41c79f8b.jpg
new upper A arms by GySgtFrank, on Flickr

They are Joe's Racing upper arms made for racing, but should work for what I want. They provide for adjusting camber and caster with minimal fuss using spacers (the blue things in the back) and slugs to adjust side to side and up and down for roll center adjustments. The arms are replaceable in different lengths if I need to change the camber gain as the tire moves through it's arc. They use a standard screw in ball joint, which I will pick up locally.

The only concern that I have is that the arms are suspended with non compliant bearings instead of rubber or poly bushings. Which is great for free movement, but they may be a bit harsh on the street. They are not the load bearing arms, so it shouldn't be too bad. The only way to find out is to try it I guess. Appropriate since this whole thing is one big bloody experiment anyway. :lol:

Looking really good Kevin. Keep up the good work. I look forward to seeing it at DGRR!

Thanks Mike. I finished up the other wheel arch and was trying to figure out how I was going to mount the arms this weekend, while I had a little time off. I came to the conclusion that I need to get some ball joints before I can finalize how I'm going to do it though. I need a week day off so I can do some shopping at the local race chassis shop. :07:

Sounds overpriced already :lol:

This is Kansas. Local redneck circle track shop. Prices don't look too bad. Not O'Reilly's level of pricing though. :lol:

Need a couple of threaded upper ball joints, so normal auto parts stores aren't an option. Could order on line, but I want to make sure they're going to actually fit before I plunk down the dollars.

If anyone needs more proof that I'm an idjit.

http://farm6.staticflickr.com/5536/1...10be672d_z.jpg
upper arm by GySgtFrank, on Flickr

When I put the upper mounts in they needed to sit where my new frame rails were at in order to get my Instant Center/Roll Center correct. Sooo. More cutting and fitting will be called for. Waiting on a digital caster/camber gauge so I can do final positioning on the A arms. (This is where I think it has to be, we'll see)

Setting my roll center to 1/2" above the ground and centered on the chassis. Initial setting for caster will be 5 to 7 degrees positive. Camber will be at zero with my adjustment all the way down. I'll use spacers to set that where I need it later.

Done with farming, back to work on the car and the never ending build thread.

Trying something different can be ... trying. I think I finally have the right side upper arm in position. 1.5 degrees camber, 6 degrees caster, 10 degree down angle on upper arm, 0 degree angle on lower arm. With full adjustability to make changes (which was what I was really after). Time to weld it in again. I've had to cut out so many previous ga-genius ideas that my engine bay looks like something from the Texas Chainsaw Massacre movies. Lots of grinding ahead. :blush5:

Doesn't look like much, but a lot of work to get this far.

http://farm6.staticflickr.com/5495/1...d5c35d80_z.jpg
Front frame arch 2 by GySgtFrank, on Flickr

http://farm8.staticflickr.com/7387/1...b16de5ef_z.jpg
shock tower rough by GySgtFrank, on Flickr

OK, go ahead and laugh. The passenger side is roughed in and back on the ground. Had to modify the original struts to take a heim joint at the bottom and weld on a perch to accept the coil over spring. Did some clearancing on the lower arm and added tabs to mount the shock as far out on the arm as possible. Then the real fun began trying to get the upper plate at the right height and angles so that nothing binds as the wheel moves, keep it within the bounds of ride height adjustment, and make sure the shock doesn't stick through the hood (the last was harder than it sounds). Also modified the coil over tube and went to a 275 pound 12" tall spring. I need to get some more measurements and do some adjusting now that it's on the ground. Then close and clean it up. Not looking forward to doing the other side, but it should go a bit faster now that I have some idea of what the he** I'm doing.

Nice!

http://farm3.staticflickr.com/2873/1...d4c82c26_z.jpg

Just to let y'all know I'm still at it. Now that I trial fitted both sides, found that my top mounts were about 1 1/2 inches too far back. I was unable to move them far enough even with the adjustment I built in. Put in new upper A arm mounts and pulled everything back apart to put in the actual bracing and shock/spring mounts. Starting to get it ground down and cleaned up. Slow, but getting there.

Gunny How much original stuff is left? Lots of hard work is see.

The front and rear frame stubs are still original. ;)

Oh and the VIN plate on the firewall. Don't forget that!

Well, hopefully the mods won't show from the outside. It should look relatively stock at first glance. Unless you lift the hood (or bonnet for Bri-Bri). :D

http://farm6.staticflickr.com/5512/1...96ea2549_z.jpg
frame & hoops by GySgtFrank, on Flickr

I got the other side in and welded up today with a bit of a struggle. Deleted the brake vacuum booster and incorporated the brake master cylinder mounting plate into the plate for the hoop. Far more compact mounting. I'll have to see how well the brakes work without it. This should make the frame rails pretty strong and get rid of any flex.

Good luck man. That's a lot of work.

Thanks Jeff. It keeps me out of trouble, sort of. :lol:

Nice

Soooooo.....you gonna make DGRR this year?

Yikes!

I think so. Despite how it looks, I'm actually getting pretty close to buttoning it up to reinstall everything.

http://farm6.staticflickr.com/5487/1...01655c79c1.jpg
lower frame rail by GySgtFrank, on Flickr

The lower rail is what the cradle will bolt to. Should have the rail on the other side done tonight or tomorrow.

Nice!

Thanks Cheebs. At least it has a nice flat surface to bolt the lower cradle to when I get that finished up. :biggthumpup:

That is a little handy...

upper mounts, Part III
 

So... I screwed up again. The upper mounts are off by 1/2" on the driver's side and the passenger side was off by 3/4 - 1". I could have sworn I had them right that time, but it was not to be. I did have enough adjustment to get them where they needed to be, but they were at the very end of the adjustment and then some. Not comfortable running it that way so here we go again. Trying to get an accurate measurement with very few squared up surfaces is a pain in the ass. So I need to cut them out one more time. Getting a little smarter this time and building a stand alone box for the mounts. That way I can tack it in place and move the whole thing when I get the alignment equipment back on it.

http://farm6.staticflickr.com/5498/1...b3d0435e_z.jpg
upper A arm mount part 3 by GySgtFrank, on Flickr

Also did a little modification while the mounts are out. I didn't care much for the camber adjustment as it tended to move too far while adjusting and it was a pain to bring it back. So I drilled out the front holes and welded 1/2 - 20 nuts on them then put a cap and nut on the other side as well. That way I can run a fine thread 1/2" bolt in each side to push the mounting block back and forth for fine adjustment. It will also help lock it in place more securely.

Cross my fingers and hope I get it right this time. :lol:

Measure once weld 4 times?

or keep cutting and welding until you get it right. ;)

Because dumb great bend marine :uhh:

Watch it! I resemble that remark. :squint:

OK. Plan 436. I ran out of letters a ways back and had to start numbering them.

To fix the problem of being at the end of my adjustment range (and still being .2 degrees off in caster side to side). I came up with putting an adjustment rail on top of my existing camber adjustment rail. This necessitated raising the mounting point and opening up some more room to the rear. I'm using stop bolts on both sides of the clamping rails so I hopefully get no movement from my adjusters when under load. This is in addition to the bolts that clamp it all together. I have been a little concerned to make doubly sure I get no movement once I get the @#$%^ thing adjusted to the correct spot.

The bottom cradle will also be able to move forward and back using a bolt and stop nuts on the bracket at the front of the lower rail. The clamping bolts on the lower rail will be slotted. It SHOULD fix my adjustability problems. I need to weld in a plate to close up the top of the mount with the upper hoop and put some gusseting across it so that the mount is rock steady.

Not the most elegant solution, but I will have full fine adjustability to dial it in, as well as the ability to make large adjustments when I decide to do something stupid. Such as playing with my wheelbase.

Me actually getting the car to DGRR is starting to look pretty iffy, since things are refusing to cooperate. Regardless of whether the little (insert Peter's favorite word here) gets there or not, I plan to be there this year.

https://farm8.staticflickr.com/7365/...f8428698_z.jpg
plan 436 by GySgtFrank, on Flickr

Hey Gunny.... one more night of insomnia, although I'm happy to see you're making progress. Such an undertaking man.... it's looking really REALLY sick.... something I've never seen done before to that extent on a little first gen... can't wait to see it done.

Thank'ee sir! I really have to get it right one of these times. Getting tired of putting it together, then having to cut it all out and start over when it doesn't quite do what I want it to. I think I've played too much of that stupid Gran Turismo game. My favorite part is buying the full race suspension and playing with all the settings just to see what it does. I have a need for a real one. ;)

I figure if I can stuff enough tire under there and get the settings right I can save on brake pad replacements, 'cuz we just won't brake fur no stoopid corners.

I'll have brakes too though, just for those damn suicidal deer. Passenger seatbelts will be a requirement so I don't lose anybody. Windshields are expensive. :lol:

So yeah... if I ever complain about the difficulty of getting my car to run right, please redirect me to this thread :lol:

Aww-HELL-yeah!!! We'll have:


A Wild GUNNY Appeared!





Unable to Flee... :naughty: