Talk me out of this - IFS/IRS Yaris 3cyl powered FJ40 buggy

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Jetboy

Jetboy

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After spending some time around the side by sides and Front Range's 3rd gen IFS (handles big tires) I've been thinking my FJ40 (currently on 39's with 5.29s, solid axles, SOA, 2f 4spd) might be due to go under the knife for a major rehab.

My thought is maybe go full on ultra light buggy build with it. Yaris 3cyl is 105hp and 175lbs. I'd go front engine longitudinal mount with the transaxle. Outputs direct to front and rear Toyota 8" clamshell IFS diffs. Then to long travel home brew IFS/IRS with toyota outer assemblies from the spindle out. 4 wheel discs. 4wheel steering, with a OEM rack/pinion up front and hydro rear. Maybe 40ish tires. Full tube frame with FJ40 skin narrowed body and 4 seats.

The Yaris transmission has a 3.5 1st gear and a 3.7 final drive. Add 3.73 geared 8" clamshells and it's got about 50:1 gear ratio or 5.29's for about a 70:1. Probably just about right.

Basically a super side by side. Goal is total weight under 2,000lbs.

Am I crazy for considering this? I think I could build it very cheaply.

basically this only durable.
10644488_1527750070788427_6639044683749894867_n.jpg
 
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I've been considering a build like this - so these thoughts come from that

with unitized bearings on most fwd and ifs 4x4s - your options are pretty wide-open for designing your own independent suspension. I think the Toyota 6 lug would be overkill and worse, add unneeded weight (which starts the whole house-of-cards falling down on light buggy).

When I build something from scratch (and I've done a few), I always start with what the manufacturer designed. If you're using a Yaris motor, I certainly wouldn't go larger than rav4 differentials/hubs. I also would never use radial tires on a buggy....way too heavy.

I'd also make the brakes inboard to reduce unsprung weight (which, again, helps in a myriad of ways).
 
Super light with 40" tires and the clam shell diffs you are suggesting would explode rapidly..


What you are imagining would be okay with maybe 35's but stepping into big tire country would not make it durable. Unless you do not plan on really using it.

A goal of under 2K is not realistic.. A old VW bug has more weight than that with P165 tires..
a 2 seat rzr 1000 weights 1,379 dry..

Some light reading.
lightweight buggy build ?'s - Pirate4x4.Com : 4x4 and Off-Road Forum
 
Jetboy said:
4 wheel discs. 4wheel steering, with a OEM rack/pinion up front and hydro rear. Maybe 40ish tires. Full tube frame with FJ40 skin narrowed body and 4 seats.
Click to expand...

Other than the OP?
 
A Yaris is 2200lbs. A CJ5 was 2,600lbs. The 258 weighed around 600lbs. So a CJ5 with a Yaris engine would I suppose be right at the 2200lb mark. I'm thinking I can come in under that weight. I haven't gone through all the weight estimating yet. 2000lbs might be a bit optimistic?

My primary observation is that most buggies have limited engineering involved in the chassis design and a lot of "more is better". Specifically they are full of small diameter tubing with a design criteria of more tubes are better. Having built a RZR chassis in aluminum with an engineering teem in my shop a few years ago - it was bout 100lbs - I'm confident that my chassis (I'll do mostly steel, cause I'm lazy and cheap) would be WAY lighter than most. Probably just a bit more than a typical rzr. Maybe 300lbs. Add 350 for engine/trans. 400 for suspension. another ?200 for fuel tank and electronics/exhaust/engine management stuff, then 600 for tires/wheels and I'm around 2000lbs. Still need sheet metal and seats/racks/winch/compressor. If I shave weight everywhere possible, I'd like to think 2000lbs is at least plausible. I could be way off base. If so 105hp isn't going to cut it. The only way this works is to keep the entire package very low weight.

The new 30 spline CVs seem to be very strong. I actually can only find one example anywhere of anyone ever braking one. I don't know what Toyota changed, but they seem to be pretty strong compared to the old 7.5 stuff. I'd hope that the 8" clamshell would be sufficient for a light weight crawler. The only way this idea can work is with ifs/irs without a divorced transfer case because of the proximity of the engine to the axle. It might go in the back just like a rzr. It's probably 10 times as strong as a rzr diff. Of course I'm talking a bigger buggy. I'm not opposed to jumping up to a 9.5" diff, but my gut feeling is that it's overkill for a light weight buggy with 100hp. Then again I have had a 100hp 22r shred birfields with a 50:1 gearing, so???

And I do want big tires. I think at least 37's, but I'd really like to run something around 40" if I can.
 
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The toy CV's hold up okay as long as you do not extend them much. Articulation is what kills them.

I am dubious on your weight. What are you basing your CJ5 weight on? I weighed a mostly stock 81 CJ5 on 33's with a soft top at about 3600. Even Tiny, the vw powered moon buggy wasn't quite that light.

But, I'm all for giving it a try. Even more so if it's really cheap. Just make sure you have someone there to save you when it breaks ;) :beer:
 
I was just using specs from the interwebs. I think they're from some Jeep publication back in the day.

Big tires are a weight killer. If you added 600lbs of tires to the 2000lb jeep... Interco makes some 36/10/18 ATV tires that could be an alternative. Smaller than I want, but they're selling them for $150ea. in the blems right now. They're not very light weight though. Kinda just in dreamer mode right now.
 
Yaris is a 4 cylinder. Great little cars for what they are. They are the next generation of the Toyota Echo.

If I was doing it, I'd start with an Echo (I've had both). Echo had a real throttle cable, not drive by wire and even though the hp ratings are the same, it was quicker and got better mileage.
 
If I had a yaris i'd do this to it.

yaris_wrc_testing_5-626x313.jpg
 
You're all crushing my dreams!! LOL. I've got a couple projects in the queue so best case this would be a project for the coming winter if I can slowly source all the parts by then. That gives me lots of time.

You might be on to something with the Echo. I don't have a donor car yet. I just googled the lightest weight Toyota engine and I found a few links saying the Yaris was the lightest engine in any production Toyota car in America. So I looked at Co-Part to see what they sell for. Seems like $500 would get you a totaled one with rear damage. Plus you can buy a Yaris engine on ebay for $299. For that price I could just buy a spare to carry on the trailer if the rest of the package is solid. Toyota's cheap cars tend to be very durable in my experience, so I thought it might just be the ticket.

The one benefit of a Honda engine is that they crank the opposite direction of most others, so if you want rear engine the belts and such are pointed to the rear whereas a Yaris engine will have all the accessories pointed forward. I don't much care either way. Kinda wanted to keep it Toyota and call it a Half-J40 or something stupid like that.

I sadly just don't ever drive my FJ40. It just sits. Needs to either get turned into something easier to trailer or sent to a new home.
 
The toyota INZFE has a timing chain in it. A plus as far as I'm concerned. These are 500,000 mile motors with little/no effort.

My 2001 ECHO got crashed at 318,000 miles in October 2010. It still had the original water pump, alternator, radiator, A/C stuff, and clutch when it died (never had the valve cover off of it). At 305,000 miles on the clock I drove from Kentucky to the Bonneville salt flats for speed week 2010. It didn't skip a beat.

It's replacement was a 2010 Yaris sedan. So far, so good.
 
Jetboy said:
If so 105hp isn't going to cut it. The only way this works is to keep the entire package very low weight.
Click to expand...

You'll want much lower gears if that's all the ponies it will have.
 
Toyota prius is based on the same engine but has funky valve timing. The prius pistons and rods can be swapped to the echo/yaris motor for more compression (go from 11:1 to something like 13:1)
 
pjohnson said:
You'll want much lower gears if that's all the ponies it will have.
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The little motor has great engine management and V V T. It pulls from idle to redline.

In a street car the manual trans versions are considerably quicker/more fun to drive (think go kart) but an automatic trans may make a better buggy
 
That's not a CJ ;)
 
Something else...I think an ECHO ecm would be easier to trick into thinking it is still an ECHO. The ECHO has no ABS or traction control and has old school wiring. The yaris ecm is going to require more sensors and I am pretty sure the wiring is that CAN BUS bull****.
 
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