Rally BRZ v2: Open 2wd Boogaloo

Sideplates and wing supports need to be thought of as airborn toe. 

TurnerX19 said:

The fabricator wants to know if the flow disruption can be mitigated by making the span taper smaller to the rear, without the complex curves of the hoop wing on a Supra. Such a taper will only improve airborn directional stability if the sideplates absorb all of the taper so that their outer surface remains parallel to the center line. I don't remember where I saw an example of that, but it is not an original idea.

It's worth noting, that if Bill (TurnerX19) hadn't expressed interest in working on a wing, I'd almost certainly be planning to rivet some lexan to the back of the car and call it a spoiler.

¯\_(ツ)_/¯ said:

In reply to sleepyhead the buffalo :

Of note compared to your usual aero stuffs- this will be quite sideways, regularly, as well as flying and pitching up/down accordingly.  I honestly want it in part just to get the thing not to nose down off jumps.

roger that

I'll note that my understanding is that most of the WRC cars (with the acknowledgement that they are predominantly hatches) are moving to rear sections that are similar to what I'm describing:

having the uprights be somewhat foil shaped on the leading edge and feeding air into the area under the "normal rear wing" as conceptualized will help keep the flow attached while the car is sideslipped and probably also have a bit of lateral-directional stability benefit?  although, this being upside-down and sideways is kinda messing with my mental picture of things.

stacking the wing above a spoiler on the trunk will have further benefits akin to the "double element" they're trying to avoid... and probably means something like a modified eppler 421 would be workable without the possible unknowns of the MSHD foil (palatov motorsports has done similar in the past with their D4's at Pikes Peak, iirc).

Rally aero is neat!!!

In reply to sleepyhead the buffalo :

I see what you're getting at- maybe I can draw something up where we do machined foam core uprights, and a hot wire cut wing section in between.  The fun part is there's a LOT to do before that's the missing piece.

Eppler 421 and Selig S1223 were the profiles that looked like good options outside the MSHD thing.

Also of note- the trunk still needs to open and work well enough to do a tire change on the clock.  Fun list of requirements we're building .

I admit to real irritation at the 10mm section minimum for sideplates and uprights. I'd much rather shear the underbrush. Also the increadable variation and lack of driver control of angle of attack mean the airfoil itself doesn't mean much. This is an elevator, not a lift. Dirt sprint cars can run a door up there, the things they're using are the sideplates.

With the exception of the mating point on the fender crown the uprights can be designed to use the same foam cutter as the wing element itself. I just project the shape past reality a few inches and hand rasp them to fit before covering the first pair. Also I have several other anchorage points/ possible easy cheap not foam core uprights. Their weight penalty is big, but it is at the back...

irish44j (Forum Supporter) said:

¯\_(ツ)_/¯ said:

In reply to irish44j (Forum Supporter) :

 

I love old rally cars but I don't see very many of them showing up to 6+ events a year, and that's my plan so here we are.

For sure, which is why when you do, it's either 1-2 per year (like me), beaten to death (Downey), or just $$$ (Irish guys with Ford Ford Econoboxs, which aren't actually old cars anyhow). And Kevin, of course :)

Nah, it's a good plan for being competitive. And plus you don't have to be the "slow guy" your wife rides when she's not running with other "fast guys" anymore  lol.  ;)

I can run an old car and not kill it because I have no preconceptions that I'll ever be very competitive in stage rally lol.

Mine will be aggressively un-abused by next year lol. We will both learn the ways of full wiring 

¯\_(ツ)_/¯ said:

In reply to sleepyhead the buffalo :

I see what you're getting at- maybe I can draw something up where we do machined foam core uprights, and a hot wire cut wing section in between.  The fun part is there's a LOT to do before that's the missing piece.

Eppler 421 and Selig S1223 were the profiles that looked like good options outside the MSHD thing.

Also of note- the trunk still needs to open and work well enough to do a tire change on the clock.  Fun list of requirements we're building .

we could call the "airfoil shaped upright rounded into the wing" a long-term idealized goal... and even that might be a stretch since it'll be difficult to build-in an ability to adjust angle-of-attack or camber.  there's intermediate options that'll work too, even if the area where the foil mounts is "flat", with some foil shaping to the upright forward/behind that section.

Weight weenie time.  How much does the whole wiring harness with modules weigh?

That'll go down a bit but exactly how/where will have to wait.

How about that ABS module?  On the L2wd car I left the whole thing there, just removed the motor and plumbed around it, because it had solenoids attached to the board that seemed too flimsy to leave hanging- but that aluminum valve block and whatnot are heavy so let's be a little braver:

A bit of that gets this:

I screwed it to a piece of plastic temporarily to keep dust out of it while it waits for wiring investigations:

Here's how much that gets rid of:

And then, the worst part of shell prep/weight reduction- spot welds.  ENDLESS SPOT WELDS.  I used spot weld bits for a bunch of stuff, but ultimately the least time consuming way with minimal damage to the shell proved to be a Cubitron wheel on a grinder and just annihilating the brackets I was removing.  There are a few spot with blow-throughs from the drill and/or grinder that I'll have to weld up:

I know it doesn't look like much but even under the hood there were a couple lbs of stuff hiding:

And the big scary one, chopping the parcel shelf- the BRZ actually has two closed sections here, so I lopped off the bigger, further forward one and left the other.  The back window frame and upper landing points for the trunk lid are still plenty stiff, and the cage is going to do more to brace the rear suspension towers than this thing ever did:

This was a LOT of work and more to go to touch it up.  I'm debating attempting to drill out all the weld nuts I know I won't use, although it'd also be easy to convince myself to wait since I can't know for sure which will come in handy yet.  The only weld studs I left on the car are the ones at the base of the windshield for the defroster vent.

Ignore the remaining chunks on the rear suspension mounts, those are in the cut zone for the towers so I didn't get too picky about them.

Very cool! I may have skimmed past some of the technical details, but you know what you are doing as well as anybody.

Lmk if you need an extra set of hands anytime, i am usually around. I'm in danger of transitioning my current project from solo4 to stage rally instead when I see awesome stuff like this

I'll apologize now for not getting over. Plenty of ideas fomenting..... 

I did a whole bunch of unexciting work- welding up pinholes where I punched through with the spot weld cutter, and flappy wheeling them back to flat.  Mind numbing, and not photogenic- here's a picture of all that stuff after hitting it with a little spraypaint.  Bleh:

Let's look at something more exciting- got a whole bunch of stuff to turn into motor mounts:

Folded, welded, failed to take a detailed picture of the engine side, but here are the subframe side (same part for both) mounts which use a front control arm bushing- a friend who I will refer to as "lotus guy" here unless he wishes to be identified differently did the final bore work and pressed the bushings in for me.  I picked this bushing specifically because it's the only original rubber bushing on the L2wd car which has never needed replacement, and it happens to be nice and compact and reasonably priced too:

But of course, I don't have my new oil pan yet either so I had to come up with a way to keep the test fit engine from dripping- make that oil pan, a foil pan!

And with a bit of wiggling, we have our first official test fit:

I also plopped the upper core support back on to visualize the gap to the radiator:

I am extremely pleased with how this looks in here.  Now just absolutely everything to go!

Looks great. Now time for 3D tetris. I like the logic train to the motor mount bushing too.

In reply to TurnerX19 :

Me too!

Is there enough room for a turbo?  Just in case? 

In reply to Ian F (Forum Supporter) :

What is the displacement multiplier for a turbo?

..

Speaking personally, driving a turbo rear drive car on gravel is less than optimal, with the nonlinear power delivery.  Even a turbo front drive car is awful light-switchey.

OTOH, I'm not the guy who used to rally a Merkur.

¯\_(ツ)_/¯ said:

I also plopped the upper core support back on to visualize the gap to the radiator:

I am extremely pleased with how this looks in here.  Now just absolutely everything to go!

eyeballing some k-swapped ClubTR BRZ/86's last year, I was oggling how much room there was with this chassis to extract radiator air out of the hood... and I had to assume a V6 would be even better.  I'd wonder if you couldn't split the cooling a bit, so the "coolant radiator" takes up the PAX side of the vertical core support, and an oil cooler and transmission cooler on the driver's size (one above the other).  With ducting (and proper mesh) in and out... you can probably get away with a smaller than stock frontal area... especially if its multiple cores?  Then again, rally cars do tend to operate a lower average speeds than GLTC.   Hrmmm.

In reply to sleepyhead the buffalo :

I think I'll be using the stock type radiator- they're cheap, plentiful, and should still have enough cooling capacity if I get a decent aluminum one.  There is a bit of a gap above the stock radiator I may duct to the oil cooler, it's normally full of intake box and foam.  Pretty excited about the hugeness of the possible vent there, though- and you're right, sometimes the airspeed is very low for upwards of 10min at a time so we can't really design any part of the car for high speeds only.  It has to cool well working very hard at sub-30mph, occasionally.

Over on the suspension side, I tested some fabricated control arms on the L2wd car- I took the spring off the strut and even dropped it down an extra bit in order to determine what increased travel would do.  The balljoint angle on these was an attempt to adjust things to allow for greater travel, and it worked the way I'd hoped more or less.

Basically this boils down to, the Ohlins I'd like to use eventually have two viable travel options up front- 207mm travel, and 244mm travel.  The stock control arms are nearing their limits at 207mm travel, while the fabricated ones will do that easily with a good amount of wiggle room.  The fabricated arms will also do 244mm of travel, just barely, but the balljoint is basically at its' limit at both full bump and full droop- I don't think it's a good idea to run something that's that close to its' mechanical limit on angle with the sorts of forces it'll see in rally, not to mention the possibility that a small bend in any component might take it beyond that, so I think we stick with the 207mm plan.  That'll also let us use stock control arms in a pinch without them disintegrating.  Honestly that should be plenty of travel up front, especially with fancy valving and hydraulic bumpstops.

Is there a way to limit the travel of the longer stroke shocks to something in between 207 and 244 mm or does that just add extra complexity for a inch of travel? If you were to go that route could you make the limiters adjustable in case you were to need a stock control arm in a pinch?

In reply to adam525i :

I certainly could, but I'd rather not carry the extra weight, overall length, and taller towers required to package that if I'm not going to use all of it.

The taller towers in the front may run into another point about bodywork. Re-read the aero rules, the part about adding above the hood line is not specific to aero....That makes a lot of hood scoops I have seen illegal as well.. I suspect they really only mean lamps and wings, but suspension tower bulges might need special approval.

In reply to ¯\_(ツ)_/¯ :

Is there any way you could measure the depth or length of the FRS bellhousing and the distance which the input shaft protrudes from it? I have been contemplating doing the same swap in a Miata and the Miata 6 speed from 1999-2005 uses the same transmission as the FRS. So this might simplify it significantly.

I wouldn't complain about the dimensions of the tailhousing and the length of the output shaft either.

If everything adds up I'd love to buy an adapter plate from you!

Also, have you considered using an FSE or Tacoma oil pan? It may be able to clear your setup, and I'm pretty confident that they interchange.

In reply to Beancup123 :