Multi Engine Coupling

He should talk to these guys.

Three miles per minute, three miles per gallon.

Walter airport fire trucks of the CB series used two Ford 534 inch V-8 engines. They were driven for testing and emergencies only. Gas consumption was in gallons per mile. About 3-4 GPM.

How about... 3 miles per minute, 3 gal. per mile

When those trucks were younger, and "less fragile", they were quick and fast. 0 to 50 mph in 40 seconds by FAA mandate, with a minimum top speed of 60 MPH.

Sound like he's going to need a sprag clutch in there somewhere.

Sprays?

The little parts that let it roll in one direction and lock in the other, Like a helicopter that looses power and auto rotates.

In this case you would have a common drive shaft with one engine driving through the sprag clutch.

Sprays = sprags?

I don't know, that image is from a sprag clutch manufacturer. That is what they called them.

I worked on a transfer conveyor that had two motors driving a common shaft. one motor had a higher rpm. and would overrun the clutches. This would increase the flow of material.

My moped has one of those!

You have to tie the crankshafts together....and then tune them as one....

https://www.youtube.com/watch?v=jM0wN0zRhgk

Take a ride in this twin V-8 = V-16 hot rod on the street....

https://www.youtube.com/watch?v=tEapHfgF1Wo

Build an engine with software....

https://www.youtube.com/watch?v=png2pPICtv8

Ultimate Rat Rod...?

https://www.youtube.com/watch?v=xxRp1zFxKBY

No, you don't have to tie the crankshafts together. He's not putting all the engine power into a single axle.

It's separate drive for the front and read.

Simpler in many ways.

Need to know the configuration of the engines. Side by side? End to end?

Does he have a drive line configuration in mind?

Some type of synchronization is needed. Maybe just electrical like twin aircraft.

Need more details.

The ground will provide the sychronization. Here's a cool Caddy!http://www.ronsusser.com/inventory/listing/1966-two-engine-toronado-the-ultimate-sleeper-car-850hp/

Well then I would take a front engined front wheel drive and rear engined rear wheel drive and weld them together, use an electronic shift and fuel control with rev counter control....

Correct, it's not the same as driving 2 axles via one prop shaft, (without a 3rd diff). Each engine works along a power/speed curve.

When coupling two recip engines together, would crankshaft angle have to be considered?

It must be considered if you want the smoothest possible powertrain. But, it is not essential to have it function. Many of the multiple engine dragsters were not that well engineered. As I look at the 2,3,4,and 5 engine setups used in tractor pulls, I find it hard to believe they are synced that well.

Why is that hard to believe?

How would you couple five engines together to keep each engine synchronized so that each #1 cylinder was exactly at TDC at the same time? Or would you stager them so that the 90 degrees between the firing pulses of each engine was divided by 5 so the engine combination would have a firing pulse every 18 degrees? Remember that each of the engines shown in the picture is capable of 2,000 horsepower.

And ask yourself what would be the gain by syncing them in that fashion..

As long as all five engines are linked together at a 1:1 ratio, and they are all powered at the same throttle opening, and are almost always asked to operate at or near WOT, what difference does it make?

I thought you were suggesting that it would be difficult to believe the engines were synced well because it is technology seen at a tractor pull.

i'd choose 18°. I don't think it wouldnmake that much difference but it might be a little easier on the remainder of the drivetrain.

If you are going through the trouble if putting all this tigether, how much more trouble would it be to connect the engines at some specific orientation than arbitrary? Probably not much more...and this is a competition.

I don't recall whether the magazine was called VW & Porsche or later as European Car, but someone mounted a second engine into the trunk/backseat area of a V-dub GTI. Somewhere in my basement I have the back issue. Not sure I can find it though.

I remember that, it was a tuning company called Dubsport.

I think it doable but I can see some major problems with the design if one drive system gets out out sync with the other or shuts down entirely while the other is on the power.

The rear engine shutting down and dragging would not be a major drivability issue but having the front drive one that does the steering and primary braking effects most certainly could create very dangerous and uncontrollable driving conditions fast than the driver could react to.

That and how exactly is he going to clutch, shift and control the power of two drive systems simultaneously with smooth and reliable consistency?

Over or under powering either end while going into or out of corner will create wild instability similar to trying to take a hard corner under power in a four wheel drive vehicle locked in four wheel drive on a dry road.

I say the project is certainly doable but as far as drivability goes I suspect that in the majority of conditions it's going to be a unsafe handful to drive for the worst possible reasons.

I can't believe you said what you did here. Mr. live-on-the-edge.

The front's still gonna steer and stop, just like the brakes were applied to the front only.

Surprising, not catastrophic.

The clutch and shifter are not that big a deal. Maybe two clutch pedals that can be operated together or separately, if needed. Shifter is just a matter of linkage.

Many times I've powered through turns on dirt roads locked in with no problems.

This is a drag car, mostly.

I disagree with the idea that the front's going to steer and stop normally.

It depends on what speed the vehicle is traveling and what type of failure occurs.

Front wheel drive vehicles are extremely unstable when subjected to high torque moments.

Even at medium speed an intermittent and/or high torque cycle in a front wheel drive vehicle will make the steering and braking very unstable and unreliable.

The higher the vehicle speed when the failure occurs, the more catastrophic the wreck will be.

Although I think there will be a lot of "OH $h!t" moments while they play with the vehicle I would thoroughly enjoy being there and participating.

The knowledge gained and the memories will be priceless.

Most high performance vehicles offered today are going back to rear wheel drive for this very reason.

Sorry. I don't know what I was thinking.

My wife had leftover Turkish potato chili and I added a bit of mustard to it to Germanify it a bit and ate it cold.

My defenses went down shortly after that. (It was so good.)

On the extreme, if the rear end locks up, no big deal. Except you now have a moving bouncy-castle if it breaks loose again. If the front end locks up it will want to become the back end very quickly, adding any centrifugal force.

on second thought, call me Captain Obvious.

Your friend would be better off with automatic transmissions. Having to manually shift two transmissions at the same time will not work when racing. On street driving, it might be acceptable, but very tough. Would he have one clutch pedal, or two? If only one clutch, he would have to move two separate shift levers while the clutch is depressed. If two separate clutch pedals, what would happen as the one clutch is released while the other is locked up? What would happen, is the car would slow down from engine braking from the clutch-engine that was not disengaged.

Trying to get one shifter to control two transmissions at the same time, at opposite ends of the car 5 times per movement of the car, all day long is just realistic. Too much mechanical movement over too long a distance.

Walter CB series airport fire trucks used two Ford V8 engines and two early Allison automatic transmissions to power them. To avoid the two transmissions from shifting at different times, they were modified to eliminate all automatic shifting. Each transmission had a six position air cylinder as shifter linkage. The driver had an air shifter to command each transmission. The driver would start in 1,2, or 3, and the transmission would stay in that gear range until the next command from the driver.

Check out the Hurst Hairy Oldsmobile. That was a duel engine tube frame drag car. two blown 425 inch Olds motors.

Drivability under hard driving was poor. Torque steer was a problem for this and other high powered front- front, rear-rear twin engine cars.

The Tommy Ivo designs would use left side engines to drive one axle, and the right side engines to drive the other axle. Other twin engine cars. trucks and tractors would couple the crankshafts together. The problem with this setup is 2x the power to the transmission. Hope this helps to guide you- him on the build. Good luck.

bobC and others, thanks for the responses. I agree with some of the issues brought up. So far he intends the clutches to be synchronized and motivated by one simple linkage system. A Solid rod system linking them together and depressed as one thus mechanical vs hydraulic. Each engine is transverse as per original design and as per stock orientation... forward and aft. Axel orientation from transmission are as they are in the original front, oriented as now per the rear. Plug and play if you will. No changes in geometry per axel size, length, spacing etc for drive axels. All components should all be synchronized ideally. any gains I suspect will be for upper end HP/torque with proper gearing. Bottom end torque gains will be only due to engine management and extremely good synchronization otherwise any variations in power transfer will be an energy loss due to differentials occurring at any point in the rpm range, i.e., differentials in traction, over/under wheel spin, varying power transfer (agin wheel spin or unequal power transfer differential between front and rear?) at any load/rpm, torque load response/energy transfer through the cars frame/flex and how some of the typical energy transfer issues differ from any car. I question if the potential problems are now compounded, or not much of an issue?, or is their an improvement to the geometry to consider with the variables perpetuated by the forward and aft engine configuration? With big pull tractors thats a very specific use and understandable, but as a driver? I think problems occur..just trying to nail them down to specifics.

Gains in hp/torque will likely be available across the rpm spectrum. At WOT, assuming minimal tire/clutch slip, both drivetrains are limited in speed predominantly by the shared load. When one drivetrain is pulling more strongly than the other, the load on the underperforming drivetrain is effectively lightened.

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Problems are more likely to arise in other situations. Running lightly loaded and engaging the clutch, especially from a standing start may be where problems become apparent.

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Light loads might invite push-me pull-me cycling as each drivetrain alternately drives or is driven.

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Engaging the clutch seems like fertile ground for problems. Feedback leading to jerky cycling seen with poor use of a normal single clutch may be harder to avoid and of greater severity.

There is potential to over rev one of the engines if the other drivetrain engages more quickly.

More wear on both drivetrains, especially clutches is to be expected. This will be exacerbated the more slowly the clutch is used to engage/disengage, and the degree of clutch and throttle mismatch.

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There may be some strange handling phenomena. A variation on torque steer may be apparent with normal torque steer but with the addition of variations in average path length between front and rear wheels with steering changes.

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It might be a good idea to install some sort of rev limiter that limits fuel if the clutch is depressed at all and rpm is within a thousand of red line.

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Also, avoiding the temptation of using lighter flywheels is probably a good idea. Heavier flywheels will likely reduce, or at least mask some of the potential problems.

I think it's doable, with separate transmission and computers. It's like ABS braking system applied to individual tires. But, if engine's are coupled in one transmission, then definitely, synchronization is an issue.

I guess you have to let to guy pursue and experiment with interest.

How many transvers 4 cylinder power packages could you fit on a Cavalier station wagon?

As many as you want but they still wont run.

Or are you thinking that if one quits then you just switch over to another one?

I was thinking on a Cavalier

http://blog.hemmings.com/index.php/tag/dual-engine/

"It can be difficult to stuff 14 cylinders into a Jetta. That's why this smart builder decided to split it up with six up front and eight in the back. The front wheels are driven by a VR6 engine while the rear wheels are driven by a turbocharged W8. Both are connected via their throttles. The front motor runs a manual five-speed while the rear motor runs an automatic five-speed."

https://www.youtube.com/watch?v=lRxpJ6Vh9Bg

Maybe this will give you some ideas! With auto trans in both ends, like this guy says, "If one hick-ups, the other doesn't know about it and just keeps going". The only connection between the two engines is a throttle cable to the carbs.

http://gmauthority.com/blog/2014/06/two-cadillac-engines-one-yugo-video/

Thanks all for some interesting replies. He now has the link and perhaps we can have him ad more information.

Hello Everyone -

This is a twin engine car. As stated before it uses two, independent front wheel drive systems in the front as from the factory, and in the rear.

The specifications of each motor are as follows:

2.0L (122ci) DOHC Fuel Injected Inline Four Cylinder Turbocharged from the Factory. Approximately 200 Horsepower and 200 foot pounds of torque in Factory trim. (Modifications will follow in time)

Transverse Five Speed Manual Transmission operated by Cables for Gear Selection. And by Hydraulics for the Clutch engagement/disengagement.

And furthermore, operation of both engines will be controlled via a single throttle cable that 'Y's to each engine, as well as shifter cables that do the same to each transmission. I will be using an aftermarket brake pedal assembly with two master cylinders in place of the original clutch pedal to operate each clutch at the same time.

The OEM 'heavy' flywheels will be used, for multiple reasons; driveability, thermal capacity, and spooling the turbocharger sooner in the rpm range and minimizing Delta P losses between shifts.

Right now, the car is under construction. I am wary of the repercussions of having a powerful, front wheel drive, lightweight car, and what that causes such as torque steer. However, I am especially concerned if having two, 500hp, front wheel drive layouts in a single car with open differentials spells disaster under drag racing conditions.

Example. Rolling at 60 miles per hour and building load using the brakes to spool the turbochargers while increasing throttle position. I can realistically see myself being pulled-- no, YANKED towards the median or other cars in the other lane without being able to react in time.

There really shouldn't be a 'median' or 'cars in the other lane' in 'drag racing conditions'.

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I would not try to dissuade someone from taking a risk that they want to and have been given ample oportunity to understand. Taking risks is one of the essentials for happiness.

But putting others unwitting at risk is not acceptable. Please do not endanger people who have not explicitly decided to take such risks.

You can good insightful feedback and suggestions here on CR4, but not unconditionally. Most on here will cease to be helpful if they learn their assistance furthers a project that endangers people who have not knowing chosen to take such risks.

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Racing is great in the proper place at the proper time, otherwise it is rightfully a crime.

I was under the impression that there are medians, barriers, and cars in the other lane when drag racing. I can see why you thought I was going to illegally race. Allow me to be completely transparent. This is NOT a street car, however it is driven on the street and when I say that I DO NOT mean race on the street. I fully understand the consequences and repercussions of daily driving without paying attention, never mind piloting a missile. Infringing on the rights of others is something I will not do. I appreciate your thoughts as well as respect your position. I'll consider that a warning.

It looks like I misunderstood the type of medians and other cars being described. I'm glad that was my mistake and not a mistake of possibly assisting the realization of something dangerous likely to be used recklessly.

First of all, welcome to the site. You will need some thick skin, as some here will not like your idea, and will let you know that.

That being said, the first thing that I want to get clear between us is this. Both powertrains MUST be installed with the same forward facing details as the car they were in originally. You can not just turn the rear one around and have the engine facing backwards. The install would be easier, but the rear engine would be trying to drive backwards.

The manual shift linkage will be the biggest problem that you face as far as I can see. Did these drivetrains use cables to shift from the factory? Do both transaxles have the exact same final drive ratios?

Thank you, I appreciate you letting me know that. I had a pretty good idea of what people think already and have had plenty of time for people to try and tear me down from this silly idea.

I also wish to be more clear when talking about this. This is not a hypothetical car nor am I a dreamer. The car is real and it has two complete drivetrains installed in it right this second. However, it is far from done. I still need to finish the shifter cables, purchase a bunch of misc parts in regards to all components of the car.

Despite already knowing not to do that I am grateful of your input. Both drivetrains are already installed where I think they should be. All of the motor mounts and trans mounts are finished aside as well as the subframe mounts.

Yes, however the solution is simple and elegant in regards to the shifter cables. These transaxles did use shifter cables from the factory. Both, front and rear engines, transmissions, gear ratios, and turbocharger selection will be identical.

OK. So far so good. If the transmissions were both cable shifted, it might be possible to have custom length cables made. Hydraulic repair facilities are likely to have the ability to make them, or will know who can.

If you look at the shifter, it may be possible to stack the two cable connector sets one on top of the other. Thus allowing one shifter to move two sets of cables. Good luck.

HEY, where's the pictures?

There was also a Car and Driver project around 1985 that put twin engines in a Honda CRX. There is a article about that edition in car lust blog....

http://www.carlustblog.com/2008/02/car-lust-twin.html