Re: 2x Engine MRolla Unveiled

Thanks to Nick for finding the MRolla build worthy of inclusion under "Epic Builds"!

Let me mention that since Reno, MRolla has raced Denver and Infineon, and will be at Infineon next month.

Denver race MRolla was plauged by a mysterious engine disabling glitch. We still had a blast despite being towed off the track every 45 minutes. We never had a positive ID on the issue but have made it go away after replacing some ignition components and re-wiring the fuel pump.

Body roll was reduced for the 10-2011 by combining coils for the front suspension.

Also at Infineon we experimented with transmission configuration on the rear automatic. I'll post our findings on that in a more detailed technical post.

We finally killed the original Volatile RAM engine at Infineon as well as our spare, but we were able to continue racing most of the race under the power of the front engine. Redundancy pays!

There are more details on the rest of MRolla's 2011 season on the blog.

We'll continue to update this thread as the MRolla career progresses.

Re: 2x Engine MRolla Unveiled

I've had this blog post off and on the back burner for quite a while. It discusses the MRolla's transmission tech issues. … ssons.html

The real meat is in these charts illustrating the shifting process.



Anyone racing an automatic may already know this, but if not it's potentially useful.

Re: 2x Engine MRolla Unveiled

Well, how'd she do at this weekend's race?


Scuderia Ignorante // Modena / Dearborn / Aichi Prefecture / West Texas

129 (edited by Mulry 2012-04-09 07:59 AM)

Re: 2x Engine MRolla Unveiled

IgnoranteWest wrote:

Well, how'd she do at this weekend's race?

Dave, it was incredible. Saturday was less fun just because of the heavy rain and the rear auto trans was shifting a little too high for the wet conditions -- the high-rev sudden weight transfer could be tricky to manage. But Larry lowered the rear shift point overnight on Saturday, and it was awesome on Sunday. It's a fun but weird car to drive. With most manual transmission cars, you kind of get into a rhythm about when to shift, but with this one, you really just have to pay attention to the shift light because you can't really hear the front engine and it will rev past the fuel cut mechanically due to the other engine still driving the car.

But if anyone else is thinking about doing a dual-engine car, I say DO IT. Awesome fun.

Pat Mulry, TARP Racing Cookie Monster Warlord Powered By SIMCA

Re: 2x Engine MRolla Unveiled

The actuation on the mechanism is not variable but stepped. We've experimented with he two upper steps that put shift points at about 5300 RPM and 6200 RPM. The 6200 is a pretty abrupt shift that was pretty tricky in the rain, and a little concerning regarding transmission abuse. It would rocket up the hill through turns 2 and 3 though. 5300 is pretty smooth shifting but left us a bit hungry on the hill climb. 5300 was our choice for this race.

We figure if we leave it at 5300 we are never going to hurt that engine or transmission (knock on wood).

We're toying with the idea of a bike brake lever mounted to the stick shift connected to the kick-down. It would be great to be able to grab the lever on approach to a hill and have the extra RPMs for the climb. I know at High Plains there is a similar hill. It would add control complexity, but drivers could just ignore the lever until they are comfortable with the rest of the controls. We don't know if it will be worth the transmission durability risk and we're leaning toward just leaving it at the 5300 RPM step permanently.


Re: 2x Engine MRolla Unveiled

Larry, I think that the shift to 5300 was a good move in terms of making the car easier to drive on Sunday. I might be tempted to move it back up for the next race (especially Denver), if and only if, the weather is dry. In the wet, I'd keep it at 5300. But I totally agree that keeping it lower is probably better for reliability/longevity, and it was certainly fast enough even when shifting at 5300.

Pat Mulry, TARP Racing Cookie Monster Warlord Powered By SIMCA

Re: 2x Engine MRolla Unveiled

The MRolla now has a Facebook page:

Re: 2x Engine MRolla Unveiled

I recently revisited the time-lapse footage of the construction of the MRolla and put together a single (vs 3 segments), more complete/inclusive video that includes some additional stills, video clips, and time-lapse of the paint party.

Re: 2x Engine MRolla Unveiled

Despite the fact that I've driven the car I still say:  IT WILL NEVER WORK!!!


Head Wookie
Snowspeeder Pilots Association
'85 MR2

Re: 2x Engine MRolla Unveiled

The MRolla is being prepped for another 24 Hours Of Lemons race at Sonoma Raceway this month.

We added another door bar to meet new cage specifications.

We redesigned the instrument and control layout.

We decided to grind down the paint and leave it raw for this race. We will probably clear coat it.

Re: 2x Engine MRolla Unveiled

To summarize the MRolla's 4th season:

24HL Sear Point 3-2014, finished 45 of 167.
24HL Miller Motorsports Park, finished 32 of 67.
24HL High Plains Raceway 9-2014, finished 6 of 42. Winner: Index Of Effluency!

That's 12 races on the MRolla now. Running like a top. We did not hold back at this last race at all as far as how hard we flogged the motors. We set the rear automatic to shift at it's max, 6300 rpm, and we pushed the front up to 7000. I'm amazed how reliable this contraption is. My drivers want me to do more races with it next season.

Re: 2x Engine MRolla Unveiled

Awesome!  Just goes to show what thousands of hours of fabrication and several years of development will do for you. wink

A&D: 2011 Autobahn, 2012 Gingerman, 2012 Road America, 2012 Autobahn II, 2013 Gator-O-Rama (True 24!)
Sir Jackie Stewart's Coin Purse Racing
2013 Chubba Cheddar Enduro - Organizer's Choice, 2014 Doing Time in Joliet!/SirJackieSte … urseRacing

Re: 2x Engine MRolla Unveiled

The MRolla is still the 2nd most fun thing I've EVER driven.

(MDHarrell's 2-stroke 3-cylinder 4-speed on the tree Saab 96 takes the cake & made me laugh and giggle like a little schoolgirl. But yours actually goes fast)

"Real ZomBees prefer Bacon"
IOE(x2) MGB/SAAB 96, Judge's Choice, Class C Win, & 2011 Hooniverse Car of the Year!
MRolla, Stick Figure/Animal House, Free Range MR2, SAAB Sonett, "The Death Flip"
2008 Exoskeleton Jag Fiasco, Concours d Lemons - Rue Britannia, worse British car.

Re: 2x Engine MRolla Unveiled

The MRolla is for sale: … p?id=30726