Home built,bike engined autox toy

Well I guess I should do this since being asked for it by a few different people so here it goes. I parted out the full composite bodied,turbo'd 4ag breathing thru a set of RX1 carbs AE86 corolla to challenge myself in my 1st(and probably last)scratch built car. Design goals were 81" wheelbase,900lbs,sub 60% rear weight bias,equal left/right balance and a budget of $5000 all in.

Specs as it sits,81" wheelbase,950lbs with wings(no driver),57.6% rear weight and 49.7% left/right with driver-went over budget though and I'm sitting about 6k now. Engine is a fuel inject 2002 yamaha R1,makes 150hp stock and now running on megasquirt.Engine will be turbo'd by spring with a low boost set-up and should make an easy 225+hp.Power to weight with driver will dip to right around 4lbs per hp. Up here in Canada the solo rules are a little different than scca,I run in B-mod which strangely has no max wing area so my wings are 22 sq ft total.Front wing COP is 32" if front of front contact patch and the rear is 12" behind rear contact patch,this relationship allows the rear weight bias to remain at approx 60% rear heavy up untill around 60 mph and then the load starts to shirt forwards due to the added leverage on the front. A miata donated the hubs,brakes and rear diff/axles,everything else is one off.

Some build pics,this was after 2 days.Made good progress-then things slowed down a notch.

Some vids in action,without wings and 710's, http://youtu.be/r_opHgKNnfU Same day with 25b ho ho's,it was the only run I made on them so I left lots of time out there-btw ignore the rattling panel,didn't notice it untill watching the vid later. http://youtu.be/8r8nhAWhCgs Only event so far with the wings, http://youtu.be/HNpzN9iLb2E

And there you have it,a condensed 7 months of my life.

Hopefully its enjoyed.

I forgot to include its 1st drive,I ran two exploratory laps before coming in to find a coolant leak. I ran 1 lap after that,this is that lap.I've never been know to take my time geting up to speed in something.

http://youtu.be/X4eQ_5MQZXs

Nice work. How is the car doing so far?

How did you decide on suspension mounting points?

7 months is damn impressive for a scratch build, well done sir.

very jealous of your fab skills. amazing work!

The car has a perfect record of setting FTD at every event its been at over the year since it was ready to drive,between 2 and 3 seconds clear of the next quickest cars.I have some sorting to do to balance the car with the areo and I've been running this year on used hoosiers.Goal for next year with more power and new skins is to be a minimum of 5 seconds clear and to finally get pax ftd. Suspension points were worked out(right or wrong)in wishbone.

Well that looks like it would be slow and boring.

...

Also jealous of your fab skills. Excuse my lack of aero higher knowledge but would the wings be that functional in autox considering it is mostly reliant on mechanical grip rather then high speed corners?

It looks like a hill-climb car

With regards to areo-yes they make a big difference even at slow speeds.Even at 40mph I'm putting significant load to the tires,in addition to to the download the end plates act like rudders and really stabilize the car. Watch vids with/without wings to see the difference,once I get the understeer dialed out it will be much quicker.

any FSAE in your past?

Since having this to drive, how boring do you find driving a normal street car?

MitchellC wrote: Since having this to drive, how boring do you find driving a normal street car?

His other race car is a Geo Metro

Kevlar, is the left side engine mounting used to shorten the wheelbase and/or was designed strictly for use w/ the diff? Also, what steering rack are you using?

That's a nice build ya got there, I really like the MC engine cars, I been toying w/ the idea

pretty sweet. I love seeing homebuilt cars. Looks like a handful without the 710s or wings.

No concern for durability or vibration from the halfshaft (driveshaft) coupling the engine to the differential? Seems like a fairly steep angle.

Extremely impressive work. $6K spent, 7 month time-span, and it looks incredible. Appears to go just as well as it looks, too, (definitely seems squirrely without the aero, though).

Any plans to go hill-climbing with it?

Zomby woof wrote:

MitchellC wrote: Since having this to drive, how boring do you find driving a normal street car?

His other race car is a Geo Metro

I love the phrase "other race car"

My summer street car is an e30 with full ground ground custom valved koni short strokes and shortened housing with an obd1 M52 with M3 cams headers and its far from boring. The geo has some rather large changes coming for the up coming ice race season,not letting the cat outa the bag just yet but it will be far more interesting than a geo should be. I did the side mounted engine because I didn't want to build a chain driven diff and I also prefer to sit closer to the rear axle.With the chain drive and transverse engine I'd need to sit well forward and than struggle a bit with getting my feet outa the way of the steering bits.Increasing the wheelbase was not an option for me. The steering rack in for an offroad buggy with center steer,it was for rear steer spindles but the miata is front steer so I simply flipped it upside down to move the wheels the correct way.Its a 1 turn lock to lock. The driveshaft is a very popular topic of conversation,the engine end uses a hawk adapter that slips in place of the countershaft sprocket and allows a spicer pto u-joint to bolt on.The engine angle and height is set so the u-joint end has very minimal angle in either direction and the cv at the diff end takes up the angle.No vibration whatsoever,I've had trouble with the 20 year oem mazda boots tearing though. I'm not concerned with the joint failing with the angle,we were tuning the megasquirt the night before an event at a kart track and the boot blew off right away and puked all the grease out.We were running out of time so I decided to keep running it instead of swapping in the spare driveshaft.Ran the car for a solid 2 hours with no grease and no noise from it,cleaned the car up a bit and ran the event the next day as well with no noise.The spare shaft is in with a new boot,so far so good. Nope on the fsae,it would be far better designed without doubt if I had ANY training at all.I'm a carpenter,I know angles and eyeballin'.

We have no hillclimbs anywhere near me in Ontario Canada,not so sure I'd want to take the chance of planting my face deep into a tree anyways.

Wow, that is an outstanding build!

Awesome

Nice build!

Great. Now I got the bike engine A mod car itch again. Thanks, dude. In the interest of getting the weight down I've been looking at brakes and spindles from big quads and those off road 'side by sides'.

I'd like to HC whatever I wind up with.

I thought this was going to be a tire-kickin' question.

For the record, I love the answer. So cool.

Curmudgeon wrote: Nice build! Great. Now I got the bike engine A mod car itch again. Thanks, dude. In the interest of getting the weight down I've been looking at brakes and spindles from big quads and those off road 'side by sides'. I'd like to HC whatever I wind up with.

Honestly I think you would be better off fabbing your own hub assemblies. The availability of bolt on spindles and bearings make it feasible for the average fabricator.

I'm lazy. If I can go to the ATV graveyard or even buy one with a blowed up motor and rob this kind of stuff, it makes my task easier.

Building your own spindles makes sense if you have the ability to be accurate enough and the big problem for me was knowing if I was putting the mounts in the "correct" locations.I was seeing uprights for DSR's with price tags of over 5k for the set-no thanks. For the sake of meeting budget and timeline goals using miata bits made the most sense,the mazda engineers seem to have gotten it pretty close.

I'm not sure how well the offroad parts would work,nor how light they are compared to the miata stuff.Looks like lots of room for 13" wheels though.

Sweet amazing skills..