Rough Footage

Here's a clip of a few laps in the MRolla. Nothing too exciting, but you can get a sense of what driving it is like. Pretty normal except the sound of the rear engine with the automatic drowns out the front completely. So you see shifting does not seem to match the sound of the engine, so it was very important to keep an eye on the front tach.

Answer To Engine Syncing Questions

Nearly unanimously the first question out of anyone after their eyes refocused when they heard about our double engine Corolla/MR2 project: “How will you synch the engines?” I heard this question so often, from the mechanical genius and inept alike, that I started to question whether the project was feasible. When I explained our theory, that synching would not be necessary since the systems would be completely independent like two coupled locomotives, they usually said “I guess that might work” with their mouth, and “you’re a batshit-crazy moron” with their facial expression.

A few would pursue the subject a little further and explain how if the engines were not synched they would contend with each other and drive the wheels at different speeds and chew up tires and put undue torque on drivetrain components and blah blah blah. As near as I could tell they expected our car to suffer the same problems manifest in a 4 wheel drive vehicle, with locked differentials front, rear, and center, doing 15’ radius turns on pavement.

My answer would be that any car has an endless array of forces operating for and against drive train: Going up hills, going down hills, head winds, tail winds cross winds, various load mass, collisions... Being welded to another car moving the same direction is just another external force on the first drive train. As far as one engine can tell, the combination of forward forces is no different than driving downhill.

My favorite is the people who speak with the authority of someone who just the other day was driving their own twin engine car and the axles snapped off on their way to work.

An endurance race proven example has been built and demonstrated. It works great. It ran hard all day. I personally flogged it. Not even an unexpected level of tire wear. If you want to build one that doesn't work just to prove us wrong, go nuts.

Answer To Transmissions Questions

Transmissions: The automatic/manual combination worked even better than we hoped. There was no contention, no heavy clunk shifts in the automatic, no problems. It was as simple as put the rear in “D” and drive normally

We had originally planned to use an electronically controlled transmission and shift the automatic with an electronic dial mounted on top of the manual shifter. Short story is we found a fully mechanical automatic and went with it due to crunch time.

The only adjustment we could make on this transmission was a cable that links to the throttle cable, the “kick-down” that tells the transmission that you are romping on the gas pedal. Initial tests we left this alone and it shifted at pretty lackadaisically. All we had to do was clamp the kick-down cable out a couple centimeters (pictured below) and our automatic was suddenly a hill climber, shifting somewhere around 5-6k rpm.

I was worried that when we released the throttle pedal (which was linked to both engines’ throttle cables, pictured below) to shift the manual, the automatic would disengage and hunt for the correct gear once we hit the gas again. Not a problem. I suspect because it only senses axle rotation, it was always ready to push just where it left off as soon as our manual shift was complete and we got back on the throttle.

Functionally the auto/manual combo was GREAT! Once you put it in drive you just drove the manual normally. Any place on the track where there was a gear selection question, you were fine with the higher manual gear because the auto was still pushing at the higher RPM. This was very distinct on the hill and in the lower speed corners.

The only problem was minor. The rear “muffler” was extremely loud compared to the front. It drown out the sound of the manual transmission engine. We had to keep a careful eye on the front tachometer for manual shifting. Shifting by sound is pretty instinctive and this took a few laps to get used to. Paul wired in and RPM shift light, but it didn’t work right and it wasn’t a critical problem. Fortunately nobody botched shifting too bad because one engine would be more than happy to push the other way past redline.

At Last!

What a pay off. The response to the MRolla at the Reno 24 Hours Of Lemons was fantastic. Everyone stopped by to compliment our whacky efforts.

On top of that, it ran far better than we dared hope. It was strong, fast, mostly reliable, a bit soft in the springs but the 4WD grip was great, and it was a blast to drive.

On top of that, we won Organizers Choice. $500! Sweet!

More details and photos to follow.

V-RAM's compression before Buttonwillow 8-2009:

150, 165, 155, 180

V-RAM's current compression as the ass-half engine of the MRolla, 5-2011:

160, 145, 150, 163

One of those is probably in revers order, but either way I'm encouraged by the cylinder that improved at least 10 PSI from th 2009 measurement, and I'm confident the others will all soon start increasing too.

Crunch Time

No more exterior pics until after we reveal the theme at the race this week. We had the whole team painting Saturday and the MRolla is looking good. Paul it the Bondo-Meister and his work has really transformed this shanty into a car.

Yesterday we started blowing a 50 amp fuse that leads to almost everything every time we turned the MR2 key to acc/on. Exactly what the issue was will remain a mystery. After a several other troubleshooting steps, swapping the complete wiring harness was a very frustrating, time consuming fix. The time it took us to do that was supposed to be spent leisurely finishing a few other tasks before we load the trailer, but now we are seriously pressed for time.

Instru-mental

Controls and gauges coming together.

Running Under It's Own Powers

Running today under the simultaneous power of both engines for the first time. High fives! From a few 30 yard driveway dashes I can report that this will be a very confusing car to drive.

Less Than Two Weeks...

We got the rear transmission installed and did some driveway test driving.

Got lights mounted. "New" wheels and tires.

Ignition switches.

Throttle cables.