Twin Engine V12 or 2x60°V6
Twin Engine V12 or 2x60°V6
(OP)
I'm going to attempt to mate two modern FWD GM engines into a longitudinal V12. As the title states, they're 60° V6 engines that can be pretty easily setup for RWD applications. With FWD accessories, they should fit together tidily enough.
My understanding is dragsters coupled engines like this would two sprockets and a double strand chain, but I'm looking for something that'll last longer, and ideally I could decouple the front engine to run as a V6. The standalone tuning to allow this will be difficult. I've read of different options but perhaps someone here could recommend something. Ideally this coupler could fit 6 or 12 different ways to allow different timing combinations of the engines for testing. Any ideas for a reliable coupler/decoupler would be appreciated.
The balancers in these engines I need to learn more about, but I'm curious if you can eliminate the need for a secondary harmonic balancer if coupled correctly. Probably not worth pursuing in this case. Constructing an exhaust system that's capable of sounding like a balanced V12 would be nice. I'm honestly not even sure what effects aside from sound would be present, given the engines are each balanced.
The routing for coolant through two engines seems a bit redundant when I want to turn one off, but maybe possible still. I could eliminate one of the thermostats maybe or use an electric water pump on the dead engine to assist with this. Ideas here are also appreciated.
I've been told not to combine the oil system into one, and though I don't totally understand why not, it does seem safer not to.
What am I missing here?
My understanding is dragsters coupled engines like this would two sprockets and a double strand chain, but I'm looking for something that'll last longer, and ideally I could decouple the front engine to run as a V6. The standalone tuning to allow this will be difficult. I've read of different options but perhaps someone here could recommend something. Ideally this coupler could fit 6 or 12 different ways to allow different timing combinations of the engines for testing. Any ideas for a reliable coupler/decoupler would be appreciated.
The balancers in these engines I need to learn more about, but I'm curious if you can eliminate the need for a secondary harmonic balancer if coupled correctly. Probably not worth pursuing in this case. Constructing an exhaust system that's capable of sounding like a balanced V12 would be nice. I'm honestly not even sure what effects aside from sound would be present, given the engines are each balanced.
The routing for coolant through two engines seems a bit redundant when I want to turn one off, but maybe possible still. I could eliminate one of the thermostats maybe or use an electric water pump on the dead engine to assist with this. Ideas here are also appreciated.
I've been told not to combine the oil system into one, and though I don't totally understand why not, it does seem safer not to.
What am I missing here?





RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
The front pulley connection is normally not designed to transmit full rated power of the engine. The rest of the crankshaft of the rear engine probably isn't designed to transmit the power of two engines.
The chain and sprocket method allows the flywheel end of both engines to do all of the power output without having to go through the front pulley. It also means the front end of each engine can operate all of its own accessories just like it normally does. It also provides some degree of "give" to allow for mechanical vibrations and torque fluctuations.
If you want to be able to shut one engine down, you will need a clutch to do that. There will not be any synchronization on re-engagement, nor does there need to be.
Keep it simple. Let each engine operate stand-alone completely independent of the other one aside from the throttles being mechanically connected. Each one is mechanically balanced on its own, each one does its own oil system, each one does its own ignition and fuel delivery.
A V8 + V4 probably isn't a good idea. A V8 has 90 degree firing intervals. An even-firing V12 has 60 degree firing intervals. A V4 with 90 degree bank angle and single crank pins has uneven 90-270-90-270 firing intervals. There's no way to stick that onto an even-firing V8 without resulting in uneven firing intervals without completely redesigning everything - which is, of course, the correct way to do what you are attempting to do as opposed to butchering something together that was never meant to work together ...
RE: Twin Engine V12 or 2x60°V6
The really terrible approach would be to spin the front engine dead for the sake of fuel economy, I'd think. Hence the idea to decouple. A somewhat efficient "sleeper" is part of the theme, I guess.
RE: Twin Engine V12 or 2x60°V6
I was thinking this was you, returning.
http://www.eng-tips.com/viewthread.cfm?qid=342044
RE: Twin Engine V12 or 2x60°V6
>>>>>>>>>>>>>> REALLY BAD IDEA, <<<<<<<<<<<<<<
because the exhaust gases will destroy the idle engine's cylinder bores in a matter of hours.
The crank nose of a (sturdy) John Deere 6.3 liter Diesel is rated for something like 75HP @1800rpm. I assume that tractor pullers add extra keyways and/or shrink disks and/or custom cranks, and still don't expect much in terms of lifetime.
If you want a V12, just buy one.
Mike Halloran
Pembroke Pines, FL, USA
RE: Twin Engine V12 or 2x60°V6
"Because we can" ... sure, but not all ideas are good ideas ...
RE: Twin Engine V12 or 2x60°V6
If it's that ill-advised maybe I should try to fuse two blocks together and make a crank. Seems like a breeze, no?
RE: Twin Engine V12 or 2x60°V6
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Twin Engine V12 or 2x60°V6
it was meant to take for torque.
RE: Twin Engine V12 or 2x60°V6
Now this is an interesting idea. How did all the ancillaries work, and more importantly, how did the drivetrain all come together in this case? A V-drive or some sort of splitter or transfer case could be useful here maybe. The ability to split the power for all wheel drive while keeping one transmission would be dandy and could maybe be integrated in a tail to tail setup like this.
RE: Twin Engine V12 or 2x60°V6
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
je suis charlie
RE: Twin Engine V12 or 2x60°V6
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Twin Engine V12 or 2x60°V6
The idea of using the GM Atlas I6 to do a twin inline six has crossed my mind, but once again, I'd be unsure how to join them with the transmission. Probably easier to do reliably than my first idea, but very large. Great for a marine application. Maybe a landyacht, but the small v6 is what I'm still curious about.
RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
I think you need to make the front of the rear crank as strong as the back. I don't know if there were steel cranks available for these, but if so, maybe you could weld on a hub that would be big enough to transmit the power from the front engine to the back. Hell, they've done just about everything else with these engines, it can probably do this too.
As far as a longitudinal transaxle, maybe you could use the TH425. It will be the 90 degree bellhousing pattern, where yours is the 60 degree pattern (although it's a 90 degree engine)
RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
Jay Maechtlen
http://www.laserpubs.com/techcomm
RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
That doesn't mean it's easy.
I recall a particular yacht whose owner removed the original Cat I6 engines, and replaced them with more powerful V10 engines from another manufacturer, because he wanted his displacement hull to go faster, and only that manufacturer would guarantee the engines for unlimited operation at WOT.
What he didn't know at first was that the engines ran on only five cylinders at RPMs below 1400, and shook the bejeezus out of the boat. I observed the (sturdy) handrails wobbling side to side maybe a foot under those conditions.
I understand he had special fuel pumps made that ran the engines on all 10 cylinders all the time, but the smoke was intolerable, so he put the original pumps back on, and then he died. I was asked to propose some magical exhaust system to fix the problem; not possible at my skill level.
I have no idea what his widow did to solve the problem and/or sell the boat.
Mike Halloran
Pembroke Pines, FL, USA
RE: Twin Engine V12 or 2x60°V6
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Twin Engine V12 or 2x60°V6
I've often wondered about the tradeoff in engine longevity regarding high revs vs hard balancing. The 90° V6 versus, say, an I6. The power of the V6 is made at relatively low (albeit rough on the rotating assembly) revolutions, which I'd think would mean you'd wear away less cylinder bore, valvetrain and bearings while making the same power, over time. The moment of inertia wears away as well, though, not to mention the "dead spot" most engines have at low RPM (maybe more common on I4's but I'm not as familiar with it). I don't know enough about lubrication or metallurgy to be sure which wins though.
RE: Twin Engine V12 or 2x60°V6
In practice, though, inherently bad designs can achieve acceptable balance related behaviors and perform amazingly well, like a Honda inline 4 with a redline in the 8's. I think the talk about engine balance is over rated. I think any engine sold for automotive use in a 1st world country in the last 30 years is pretty well balanced.
RE: Twin Engine V12 or 2x60°V6
Pardon the poor terminology on my part, it's been awhile. I always thought, contrary to the folks who said "there's no replacement for displacement", I have to argue that, actually, clever cylinder arrangement can be a fine substitute.
RE: Twin Engine V12 or 2x60°V6
Nope, 3.8 litre 90 deg V6 has enormous inertial couple at 1.5 order, and is still currently sold. They may have fitted 1.5 order balance shafts but I doubt it very much.
Also no, an I6 has (virtually) zero inertial second order. The various cylinders cancel out. The only 2nd order that is left is due to mismatch in piston weights and things like that.
Engine balance is not overrated, you as a consumer benefit from a lot of hard work by people who know what they are talking about, so that you can think it is 'overrated'. Try riding a motorbike with a 500cc single cylinder engine with no balancer shafts and then say it is overrated.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Twin Engine V12 or 2x60°V6
And yes you are certainly right, that balance is important and that a lot of engineering goes into it. I was directing my comments toward a conversation that seemed to have evolved into whether or not off the shelf engines were balanced acceptably well, and I was trying to point out that they are.
RE: Twin Engine V12 or 2x60°V6
https://en.wikipedia.org/wiki/Piston_motion_equati...
Of course for forces we are interested in accelerations not velocities.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Twin Engine V12 or 2x60°V6
The GM 4.3 is a different engine family, based on the Chevrolet V8. There may be different series 4.3s, I don't know.
GM finally stopped building the 3.8 in the US around 2008, I think.
The newer GM 60 degree V6 motor seems to run pretty strong. (I have 2012 Impala with 3.6, feels considerably stronger than the '02 3.8 I had)
My project car still has a 1987 3.8 in it. Last year without a balance shaft. Not super smooth at idle. Being a transverse may reduce the imbalance effects?
It has been unreasonably durable, but am looking forward to installing the newer 3.8 I have for it.
Jay Maechtlen
http://www.laserpubs.com/techcomm
RE: Twin Engine V12 or 2x60°V6
RE: Twin Engine V12 or 2x60°V6
Jay Maechtlen
http://www.laserpubs.com/techcomm