Rally BRZ v2: Open 2wd Boogaloo

Exactly 4 years ago I started a thread about our Limited 2wd BRZ rally car and since then we've done a bunch of events in it, won our class in a few of them, been on the podium a bunch of times, and even managed to put together a regional championship win or two along the way.  That car is still awesome and we're still competing with it.

So why, then, have I just pulled the perfectly good FA20 from my daily driver?

Because it's time to build another one!

ARA Open 2wd
There are other rules that apply to all classes about things like safety and bodywork and whatnot, but this is the entirety of the specifics on Open 2wd in the rulebook:

That's it, and then you have this chart here (red added by me) to tell you your weight and displacement and restrictor if you're unfortunate enough to require one:

So let's get into why that red stuff is circled.

Overall Concept
The L2wd car had a clear mission- make a reliable rally car out of a BRZ without any excessive spending, while still addressing all weak points.

This time around, I'm aiming a little more aggressive, because to compete in O2wd, I'll need more power, less weight, and a tougher car overall.  So this one will have to be more like- make a reliable, competitive rally car out of a BRZ and improve performance where possible with clever use of better components and/or fabrication where necessary.  It's still very important that the car not be excessively costly or have wild amounts of difficult to produce, one-off parts; it needs to be able to compete, smash something, and still have whatever is damaged replaceable in a cost effective way before the next event.

What a tall order I've made for myself.

Engine
The current L2wd car definitely isn't inspiring in the horsepower department, and with good used FA20s changing hands for over $2500ea I have to admit I'm a little nervous about the day I need another one.  You can make perfectly good power with them if you add forced induction, but the costs rise exponentially if you want that power to be reliable and honestly, I do not want to mess with engine internals if I can avoid it- just not really my thing, and in competition I'd really not prefer to think about the engine being a major cost if it pops.

The "easy" answer would then be a Subaru H6 of some sort instead, since it bolts to the transmission, but honestly I don't really love Subaru engines, and the power numbers still aren't what I'd like in an Open car.  K swaps and LSs and the other typical answers were also considered, but like an idiot I'm trying to make this thing fit multiple rulesets and to rally up in Canada they want the engine block to match the chassis manufacturer- nice for me that these cars are both Subaru and Toyota...

So, I've chosen what is rapidly seeming like GRM's favorite minivan engine- the Toyota 2GRFE.  300hp seems like plenty, it's only 80lbs heavier on my scale than an FA20, and they're cheap and they made a zillion of them- sure sure, they don't fit in a BRZ at all or bolt to the transmission but we'll get to that in a bit.  I currently have two of this engine, one is full of metal and only for test fit and the other should be totally fine:

Suspension
The L2wd car has proven out a number of things about the suspension- the front end is actually pretty awesome, so while more travel would be nice it's not an absolute necessity.  The rear absolutely needs more travel and probably some minor geometry alterations.  Both ends will have extended towers, and the rears in particular will be a lot taller than the L2wd towers.  The fronts will be either a similar height to the L2wd car (which is more or less the maximum that fits under the hood) or possibly slightly taller IF it turns out that I can accommodate the additional travel with fabricated control arms:

Big boy tower height seen poking out of the hood here:

My intention with the suspension is to build the first iteration around some Bilstein struts similar to what's on the L2wd car, and then move those to spare duty and spend the big bucks on a set of Ohlins once the car is fully functional and driving.

If I find the rear suspension to be completely unworkable, fabricating something else is a possibility, but ideally I'd really like to keep some of it stockish just for spares purposes.

Chassis
Last time I removed almost nothing, and was predictably rewarded with a heavy car.  This time I think I'm going to spend a lot of time drilling spot welds and removing absolutely everything that the car doesn't need- we're going to have a heavier engine and I'd still like an overall lighter car weight if at all possible.  Seating position will also change, both for safety and weight distribution; ideally the seats will sit all the way back slightly behind the B pillar, and we'll move the controls to accomodate.  The car will need a pedal box anyway since there will be a cylinder head occupying the space where the brake and clutch master cylinders normally live.

Once I've got the rest of it ready, Adam Brock will be caging it because he's the best.

Aero and Bodywork
The hood is probably going to need at least some alteration to fit a tall v6 under it, and I might as well look at making the trunk and maybe some other stuff lighter while I'm at it.

I also think a wing would help at higher speeds, so probably worth doing one of those as well.  I've got something drawn up with the MSHD airfoil profile and a general support concept that attaches to the rear quarter so that the trunklid can become a floppy nothing, but not much else in that department right now:

Electrical
The OEM wiring on the L2wd car has been almost completely reliable- as tempting as it is to rip everything out and go full racecar with a PDM and stuff, I don't think that's an intelligent place to spend money here so I will be attempting to retain enough OEM wiring to run all the boring stuff that I don't want to have to think about.

Brakes
Pedal box is going to be non-optional with the new engine, so that.  Front brake upgrade path is nice and clear, since the ubiquitous WRX 4 pot calipers will bolt up and clear 15" wheels just fine- in the rear I could go with the matching aluminum WRX 2-pots, or have considered adapting the 4-pot for cast iron toughness and matching spares all around, although that'd require major bias alterations elsewhere in the system.  Either way, I intend to stay in the Subaru parts bin here.

Driveline
It'll need a driveshaft made or the stock one shortened pretty aggressively, which isn't a super big deal.  I actually really like the options for the stock differential housing, so in all likelihood it'll be either an aftermarket 1.5way LSD or another mk3 Supra one, and most likely 4.56 or 4.88 gears- the L2wd car has 4.88s, and the lower redline of the 2GRFE would put all the speed/gear calcs in nearly the same exact spot with 4.56s installed.

You're a madman. Subscribed. 

Looking forward to this!

Oh boy, this should be a fun thread.

What transmission do you plan on installing?  Keeping the stock one?

The FR-Sienna?!  Has a nice Ring to it. 

Following, obviously.

Yuss!

Involved. It will be awesome....Oh, right, that was a Nissan tag line.

Thanks guys!  Obvious question will be, wtf am I gonna do to get that engine in there- the suspension stuff is mostly iteration/alteration on what I've learned with the current car so the path there is clearer.

Why the regular (fwd) 2GRFE and not the (rwd) 2GRFSE?
I don't want the direct injection complexity of the -FSE, the regular flavor is cheaper, and importantly, Frankenstein Motorworks makes tuned ECUs for them which should allow me to continue staying away from standalones.

OK but it doesn't fit
This is technically true, although with slight pan modification it could fit with a pretty aggressive hood bump.  I don't like how far forward that would put it, though, so my intent is to stick the back of the cylinder heads against the firewall and start cutting.

What transmission?
Despite the two damaged ones sitting in my shop, I plan to use a stock transmission.  There are a few reasons for this:
-I haven't actually damaged one in any way that suggests power/torque was the culprit
-The ratios are very nice
-They're light
-They're cheap
-There are numerous upgrade paths (newer FA24 variants of the same gearbox, or the holy grail of finding a cheap used QBE69G sequential some day)
and very interestingly... they're almost made for an adapter.  Subaru recessed their flywheel into the block, and Toyota didn't, which adds up to mean I can use a ~1.3" adapter and the overall stack height winds up correct for a BRZ clutch, flywheel, starter, etc. etc.

Here's my adapter "kit":

The gearbox adapter has counterbores in the other side and will basically live bolted permanently to the engine, and allow me to utilize all BRZ fitment stuff on the gearbox side.  The flywheel will be a lightweight steel BRZ flywheel with the crank pattern of a 2GRFE in the center but no other changes- Spec seems happy to make me one, although timeline is currently unknown.  The adapter is on a similar timeline but material has been purchased.  I also got a clear template cut for fit check:

A few bolts will have to go unused on the block side, but the engine and transmission will each have 2 dowels going into them and the bolts are huge on the 2GRFE so I'm not really worried.

Oil Pan
This was a major decision point for me- I really didn't want to make one, but the geometric/weight distribution advantages of doing so were too glaring.  The plan is a machined upper pan and welded lower, with externally mounted oil filter and cooler, and a slightly cut down OEM pickup tube.  The profile can be much lower and it'll let me shove the engine way down and back:

Clearance to the windage tray is, I think, still enough and filling the area formerly occupied by the weird flat engine with sump gets me 6qts of capacity:

Cooling
The other big problem with putting a fwd engine where it doesn't belong is the stupid radiator hose coming out of the back of the heads.  I looked at every configuration of IS350/250 coolant piping and a lot of parts mix and match only to ultimately be foiled:

Everything is just different enough on the rwd engines to be nonviable, so there's going to be a weird wraparound coolant pipe- upside, I can put the end of it wherever I want, and stick a radiator cap on it probably too- where is going to depend on the intake.  Uh oh.

Intake
The various stock 2GRFE intake manifolds are WAY too tall, so I'll need something different.  Luckily, Marc from Frankenstein Motorworks has been hugely helpful as I design and theorize all this stuff, and is working on something in this area.  As long as I don't need a giant cowl hood I'll be happy, I just don't know precisely what this intake solution will look like yet either.

Exhaust
Since this engine is a V instead of a pancake, there's actually a bunch of room and I'm pretty comfortable zapping something together once I see where everything else has ended up.

ECU/Wiring
This is hopefully the magic piece of this puzzle- Frankenstein has tuned Sienna ECUs and absolutely fantastic instructions for wiring them, and I can even get one setup for the returnless BRZ fuel system's stock fuel pressure.  The question will be how much of the BRZ stuff it'll happily integrate with, which is going to mean a bunch of wires on a bench and massive amounts of coffee, most likely.

I do also want to make a point here of inviting everyone to poke holes in this and ask questions and tell me where you see me approaching a massive pitfall- this stuff is mostly CAD and experiments at this stage, it'll only get harder to course correct as I get further in.  I've spent a lot of time thinking about it but that doesn't mean I'm thinking of everything.

The adapter plate needs to fill inward towards the block on the right side to prevent dirt ingress behind the flywheel.

Let's Goooooo!!!!

In reply to TurnerX19 :

Some sort of cover is going to be in order for that area- slight grinding may be required for starter clearance so I'm not perfectly certain what it'll have to look like yet.  Similar concerns for the bottom of the adapter, but I drew up that brace for that spot instead since I also want a little extra insurance on rock hits.

In reply to ¯\_(ツ)_/¯ :

Would a fairly simple flat piece of metal work with a recess on the engine-side of the adapter plate?

Front Suspension
As previously mentioned, which variant of the big boy Ohlins travel I target is going to depend on whether I can the rest of stuff up there to accommodate 244mm travel (their longer option needing towers through the hood, currently front bushing runs out of twist and balljoint runs out of angle) or just 207mm travel (their shorter option, which would allow towers very similar to L2wd car, ability to run stock control arms if needed).  I think I'd also like to add a steering quickener but retain the column assist electric power steering, because it actually works really well.  So some TBD and nothing groundbreaking there.

Rear Suspension
The L2wd car's stock geometry in the rear gives it a lot of bumpsteer and not much travel, along with an alarming amount of antisquat if the ride height is adjusted too high.  I put the points in SolidWorks (because susprog3d is confusing and difficult for me) and started messing around, and despite moving the toe link all over the place, I really wasn't able to do much with the bumpsteer characteristics.

Then I scooted the trailing arm attachment point down, which I figured would just help with antisquat... and the bumpsteer improved too!  So it seems that the trailing arm mount location is the magic sauce, at least theoretically, for getting a bunch of stuff to work better, and as long as I can keep the toe in check I should be able to increase the travel back there a bunch at the same time.  The results looked promising enough that I welded some stuff to a spare subframe:

I think an adjustable trailing link will also help me really dial this in, as well as welding the toe link eccentrics in their innermost position and using an adjustable toe link instead.  The plan here is to assemble the whole thing, with a spherical bearing replacing the ultra-bindy trailing link bushing, and start playing with it to see what I can get the bumpsteer down to, with a goal of getting near 250mm rear travel if at all possible.

In reply to Ian F (Forum Supporter) :

Less pieces please. I have milling machine access to neatly add clearance on the finished part.

Loved the original, can't wait to see this plat out! 

and we're off! hweee!!! 

This is gonna be awesome

Lets goooo!!

Several years ago I asked you why you didn't just go all-in and run open with us. You said something to the effect of "running in Limited saves me from myself" or something to that effect.

Glad to see you finally ditched that idea, since few people are more creative than you are in the DIY section of rally...

And though I already knew about this project, obviously, I'm still mildly surprised you didn't go with something totally off-the-wall for rally.  But I guess this one will be different enough from the current on that it won't get boring like "just doing the same thing again" would. 

In reply to irish44j (Forum Supporter) :

I really, REALLY looked hard at a number of interesting older cars- mid 80s Toyota products mainly, even to the point of going and checking out a few KE70 Corollas and doing a pretty detailed measuring session on my 85 MR2.  Ultimately, as much as I'd love to build something with that much cool factor, and as much as the lighter weight might make it better on paper, I decided that what I really want out of this next car is to compete with it, a lot; 40 year old cars are still 40 years old, and come with parts sourcing problems and additional work because of it. A modern shell with modern components and a super healthy supply of good used parts should mean I can run more events and therefore get more practice and be faster.

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.

Hell yes, subscribed. Do you have an idea of what kind of whp a stock engine converted to rwd trim puts down?

In reply to Shavarsh :

Not a clue!  I know they can make over 300whp in transverse applications, and I'd be very happy with anywhere near that- the L2wd car's FA20 is probably putting a whopping ~165hp to the ground so it'd be a massive upgrade.

Speaking of which, I just sold the FA20 from this black car, which has basically zeroed it out by Challenge math.  Motor mount parts have been ordered and much removal of stuff from the shell is ongoing.

Build following intensifies!

¯\_(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.