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Thread: B13 Rally Car Build

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2011-04-11 14:13:30
Originally Posted by hpro123
1. Subscribed.
2. DId you figure out what you are going to do with your transmission? If not, ask, we may be able to help.
3. Interested in your rear link solution. Note that from Road Racing experience in the forums, it was not the parallel ones that were the major problem but the trailing link.

For now, I'm just running a stock B13 transmission. I'm interested in hearing options.

As to the rear suspension, it's not just the trailing arm or the parallel arms that bind, it's all of it. The rear suspension on the B13 operates almost entirely in bind, and depends on the compliance of bushings to make it work.

As the wheels go up and down they get pulled front-back by the trailing arm's arc. That requires the parallel arms to flex at the body and at the knuckle.

As the wheels go up and down, they also get pulled in and pushed out by the arc of the parallel arms. This requires flex at the ends of the trailing arm, both at the body (large bushing) and at the knuckle (small bushing).

With the limited stock travel, the soft stock bushings allow for this flex. The problem is that they also allow for the wheel to move in less controlled ways as the bushings deform in other ways than simply pivoting. This means that the alignment of the rear wheels is constantly changing under load. To try and address this, people put in poly bushings, which have much less compliance.

This causes the binding to become much worse (though I'm of the opinion that it's not really as big a deal under typical circumstances as some make it out to be).

The "fix" of leaving the stock front bushing in the trailing arm helps in two ways. One, because the bushing is soft rubber, it will deform in such a way as to allow some fore-aft movement of the arm, which the poly bushing doesn't. Two, because the ES bushing is so wide that it makes contact with the body mounts across the face of the bushing (not just at the metal sleeve), it's resistance to flex is well above the difference between the rubber and the poly materials. I think this bushing is a poor design on ES's part.

The problem with the fix is that it requires the trailing arm to move in ways it was never supposed to move, and puts all the binding stresses on that one bushing. But it works for most, and even as a compromise, it's better than stock for track use.

Now, add more range of motion to the suspension, and things get really ugly, because the farther you move the wheel up and down the more the arcs of the arms pull the wheels in and forward. Since my rear suspension has massively more travel than stock, I see binding bad enough that the bushing prevent droop about 2-3" (!) before the struts do. Not only is that wasting travel that I could be using, it also means that the suspension will behave in a very non-linear fashion.

The ideal solution would be to replace all of the bushings with rod ends and allow full articulation, with 100% compliance in the directions required and 0% in those not. Offhand, I'm not sure how to make that a reality, but here's what I'm doing.

1. New parallel arms with heim joints at each end (this has the side benefit of allowing for length adjustment of the arms, but that isn't the main goal). This takes all the bind out of the parallel arms, and allows them to move fore-aft smoothly, without requiring the front trailing arm bushing to compress.
2. I will initially shave the front trailing arm bushing (using the ES poly one) to allow the arm to pivot more freely, while maintaining the higher level of control of the poly bushing in compression (fore-aft movement). I actually have the rod ends and tube adapters I need to convert this joint to a heim joint as well, but not enough time to take that on before the first event.

That leave the bushing in the knuckle, and that's the hard part. If the bushing was in the arm, it would be no problem at all to replace with a heim joint, but as it's in the knuckle, it's a pain. I'm sure someone with mad fab skills could come up with a way to machine the hub and press in a ball-type bushing, or perhaps remove the current attachment point entirely and thread the knuckle for a ball joint. but I haven't come up with a brilliant plan that fits my fab skills yet. It's possible that between the parallel arms and the shaved front bushing, I'll never need to go further; there would still be some bind, but it may be minimal.
2011-04-11 14:50:17
Obviously you are way into the rear suspension stuff... will anxiously wait for progress, if and when it happens! As you have may have seen, there have been other rear-link efforts that started and died with only a few people benefiting from it, it is definitely unpredictable!

As for trannies, for the SR20 block there are only 3 reasonable alternatives.

RS5F32V/A: the one you have, the weakest.
RS5F70V/A: the infamous B15/P11 transmission, some 20% stronger in specs but proven to be significantly stronger in practice! This can also get all the internals from the QG RS5F70 transmissions and all the LSDs from the RS5F32 trannies.
RS5F50V/A: The oldest and strongest one, from the FWD U12 and some Altimas. Ideal if you can source parts.

The 6 speed from the latest Nisssans (RS6F5#A/H) are totally unknown to me in terms of strength but availability is SCARSE.

All of the above were manufactured by the Aichikikai factory and parts are used in a zillion other Japanese and European models.
2011-04-11 14:59:27
Strength of the transmission isn't likely to be a big deal for me because: A) I'm not running a lot of HP (stock, tired DE for now, and perhaps a high-compression DE+cams later). B) On gravel, the shock loads are less, since the tires spin so much easier than on pavement. Availability of a clutch-type differential is a much higher priority than strength. After that it's availability of replacement parts. For instance, a killer transmission isn't worth much if it requires Frankenstein axles that can't be sourced easily.

For the rear links, I'm leveraging stuff sold for circle-track cars. If someone was willing to do work themselves (as opposed to buying a pre-made kit), it could be done for under $200. A pre-made kit would probably be twice that.
2011-04-12 14:21:22
In this case the RS5F70V is your best choice because:
-- 1. It IS stronger than the RS5F32V.
-- 2. YOu will be able to get spare parts for all the internals for a LONG time since they were in all N16s with the QG18 engine until 2006 or later. BIG PLUS here.
-- 3. The LSD part is identical to the old RS5F32V differential and there were disk-based aftermarket LSDs for those from Nismo in the US and at least Co\usco in Japan. There was another one which eludes my memory.

2. Rear Links: I would appreciate it if we could "talk" when you are done!
2011-04-12 15:14:36
Vector, your post on the rear suspension sounds familiar. =D


Also, read the last couple pages of this thread. Slowly but surely they are coming to market.
2011-04-12 17:08:57
Originally Posted by BenFenner
Vector, your post on the rear suspension sounds familiar. =D


Also, read the last couple pages of this thread. Slowly but surely they are coming to market.

Yep, I had certainly read the first one, though I'd forgotten that there were the nice diagrams there.

I had been following the second one, but it seemed to have died out, so I went off on my own to make them.
2011-04-12 18:51:17
very nice project! subscribed
2011-04-14 19:57:00
Some progress last night, pics later tonight.

Pulled the engine and transmission last night. Went pretty well, I think about hrs from start to engine on a dolly alongside the car.

We were being absolutely fanatical about making sure all the lines and wires were disconnected, as not to damage the wiring harness. So when we started hoisting the engine out and it was hanging on something, we were really puzzled. We dropped the cross-member off thinking that maybe it was just binding on that. At which point Dan (who will be my co-driver) just started laughing. Turns out we left the shift lankage connected. Ooops.

The other fun was getting the driver's side axle out of the transmission. That thing was stuck in there like none I've ever pulled before. The really maddening thing about it was that when it finally came, it was with just a gentle tug. The inner CV joint on that axle has clearly been re-manufactured, and it was a complete POS as well, so perhaps the fit of the circlip was loose and hanging up on something.

Wit the engine out, the extent of the body damage is more evident, but doesn't go any farther than I thought, so tonight the plasma torch gets a workout.
2011-04-15 05:32:11
With the engine out, the damage to the driver's front is pretty obvious.

About 15 minutes later: (I LOVE the plasma cutter)

And an hour or so later, all the bent stuff is gone and a little cleanup of the engine bay has happened.

Next up, more cleaning and then trimming the good front clip to fit and weld that sucker on.
2011-04-24 23:43:16
Looks like you've got your work cut out for you. (heheheh)
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