You're right that some synchronization would be nice :) Accelerating (relatively) smoothly would require the engines to work together- eg, the honda would be acceleration in the power band while while the 8-liter is shifting. The output at the wheels can match, they HAVE to match!! It's not like the two engines are running side by side in two different cars and need to maintain the same speed; they ARE connected by the car, and should share the load. When a transmission shifts, the other engine will have a higher load. Auto transmissions don't force power backwards to the engine for shit (most cars you can't push start if they have an auto transmission, though there are some exceptions). I agree that the torque converters will take quite a beatdown, but arguably not more than stop and go traffic. I would also agree that it would be better if the engines are either both pushing (adding energy) or not pushing. I think you're right that both engines should at least be on and in neutral while the engine is in motion, unless there is an auxiliary oil pump/cooler that lubes and cools both transmissions when the car is on/moving. The transmissions could upshift and downshift due to differing loads at different RPM for each engine, but I think it could be avoided with a little care and tweaking. Also, if both torque converters are working correctly, I don't see why braking and downshifting wouldn't be seamless. About a functional dual engine auto, there is not really a need for it, as one engine is usually sufficient. But, to answer the question, I think it was Mercedes Benz that recently made prototype car with 2 diesel engines, one in front, one in rear. I'd bet anyone $20 that it'll be faster than a stock Delorean. (the front transmission won't matter when the wheels are off the ground, weee!) Jim On Wed, 24 Sep 2003 09:08:29 -0400 "Dave Stragand" <dave.stragand@xxxxxxxxxxxxxxx> writes: > Yes, but how in the heck are you ever going to synchronize them? Due > to the > different power curves and gearing ratios, it's simply not > mechanically > possible to get the output-at-the-wheels curves to match. Even with > automatics, you're still going to have a lot of issues. > > If one is assembly is ever moving faster than the other, it's going > to push > or drag the second (and this will almost always be this case) -- > yes, even > with automatics. This very effect is going to cause the powerband > on both > engines to alter their power and load, cause the trans's to up and > downshift > erratically, and wreak havoc on the frame as it is accordianed back > and > forth -- stresses neither the original nor your front sub were > designed or > suited for. > > Even if you had two identically matched engines and transmissions, > you'd > have a hard time ever getting them synced. As far as I know, the > only beast > to successfully accomplish this multiple engine feat was WWI-era > Sherman > tanks, which had four straight-six Chrysler engines running together. > However, they shared a -common- crankshaft and drivetrain. The old > Cartercar of the 19-teens had a dual engine setup, but again -- they > were > mechanically synchronized via gears. > > You say that due to having two auto trans's, therefore you won't > have these > issues, but you will, as well as torque converter chatter and > foaming. And > unless you have positraction-type differentials in each trans, it's > not > going to want to go in a straight line either. > > You're going to run into these issues if you have both engines on. > But if > you run on a single engine at a time, you're still going to have > some bad > issues. The oil pump on an auto trans runs off of power from the > engine, not > off of the wheels. So with the car rolling on one engine, the > other's > transmission is going to be running without lubrication. That's why > manufacturers tell you that you should not tow an automatic on the > drive > wheels for more than 25 miles or so tops, unless the engine is > running or > you disconnect the driveshaft. The inside of the trans WILL fry > after about > 50 - 100 miles. You're going to be running metal-on-metal inside > the case. > > It may work Jim, but I'd venture to bet that due to these engineering > limitations, you're going to run into: > > 1) lots of blown transmissions > 2) unstable steering, especially under load > 3) 'bouncy' braking as the trans's will downshift at different times > 4) unstable, chirpy, jerky, crooked acceleration > > Walt is right. Older four-wheel drives shared these same handling > issues, > and they even used the SAME engine and transmission. The effects > are going > to be greatly magnified in your configuration. > > Your car will certainly be unique, and a great novelty, but I > wouldn't plan > on trying to run both engines together on any regular basis. > Another way to > look at it -- in 100 years of folks trying to make cars faster, why > hasn't > anyone (including the world's best engineers) ever come up with a > functional > dual-engine auto? > > I commend your efforts, but unless you have some seriously complex > and well > thought out designs to counter these and other issues, I'm betting > that your > car under dual power will actually run -slower- than stock, with > dangerously > unstable handling to boot. I really hope you can prove me wrong, > but these > are some serious engineering feats to surmount -- that have never > successfully been surmounted before. What are your thoughts on > overcoming > these challenges? > > -Dave > ________________________________________________________________ The best thing to hit the internet in years - Juno SpeedBand! Surf the web up to FIVE TIMES FASTER! Only $14.95/ month - visit www.juno.com to sign up today! Yahoo! Groups Sponsor ADVERTISEMENT <http://rd.yahoo.com/M=194081.3897168.5135684.1261774/D=egroupweb/S=170512 6215:HM/A=1732161/R=0/SIG=11p5b9ris/*http://www.ediets.com/start.cfm?code= 30509&media=atkins> click here <http://us.adserver.yahoo.com/l?M=194081.3897168.5135684.1261774/D=egroupm ail/S=:HM/A=1732161/rand=298418188> To unsubscribe from this group, send an email to: DMCForum-unsubscribe@xxxxxxxxxxxxxxx Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
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