citroen C2 v12 4wd
Discussion
I haven't read the whole thread so apologies in advance for (a) possibly repeating a question, (b) possibly asking a general question which has been asked elsewhere, or (c) asking a stupid question 
but.....
I've always wondered how you synchronise a twin-engined car. Because if the engines are not in sync, surely one will always end up either pushing or pulling the other? Obviously there's still power going down, but if one is running at, say, 90% power, then surely as you accelerate, the 100% engine will get to the desired speed slightly faster than the 90% engine?
Does that question make any sense at all??
but.....I've always wondered how you synchronise a twin-engined car. Because if the engines are not in sync, surely one will always end up either pushing or pulling the other? Obviously there's still power going down, but if one is running at, say, 90% power, then surely as you accelerate, the 100% engine will get to the desired speed slightly faster than the 90% engine?
Does that question make any sense at all??
CAPP0 said:
I haven't read the whole thread so apologies in advance for (a) possibly repeating a question, (b) possibly asking a general question which has been asked elsewhere, or (c) asking a stupid question but.....
I've always wondered how you synchronise a twin-engined car. Because if the engines are not in sync, surely one will always end up either pushing or pulling the other? Obviously there's still power going down, but if one is running at, say, 90% power, then surely as you accelerate, the 100% engine will get to the desired speed slightly faster than the 90% engine?
Does that question make any sense at all??
Read my post, 4 posts above yours. but.....I've always wondered how you synchronise a twin-engined car. Because if the engines are not in sync, surely one will always end up either pushing or pulling the other? Obviously there's still power going down, but if one is running at, say, 90% power, then surely as you accelerate, the 100% engine will get to the desired speed slightly faster than the 90% engine?
Does that question make any sense at all??
They don't have to be in sync perfectly as long as they are both pushing the same way, eg forwards.
The two engines cannot run at different speeds as they are connected by the road.
CAPP0 said:
Thanks - I see both explanations, the electronic box answers it all!
I'm sure the OP will correct me if I'm wrong but the 'electronic box' will indeed work like a 4x4 traction control to stop one or more wheels spinning up during fast aggressive driving or slippery surfaces, and as such will make this citroen drive better in those conditions, but it is not a neccessity for a twin engine setup.All the 'old' twin engine cars like the 2 x VR6 golfs etc had literally only a throttle cable linking the two engines, and a cable change linking the 2 gearboxes, that was it.
There was no other electronics involved.
The revs/speed of the two engines were kept in sync my the road connecting them together.
Even if they broke traction, as soon as all 4 wheels gripped again they were back in sync.
It isn't witchcraft
NinjaPower said:
I'm sure the OP will correct me if I'm wrong but the 'electronic box' will indeed work like a 4x4 traction control to stop one or more wheels spinning up during fast aggressive driving or slippery surfaces, and as such will make this citroen drive better in those conditions, but it is not a neccessity for a twin engine setup.
All the 'old' twin engine cars like the 2 x VR6 golfs etc had literally only a throttle cable linking the two engines, and a cable change linking the 2 gearboxes, that was it.
There was no other electronics involved.
The revs/speed of the two engines were kept in sync my the road connecting them together.
Even if they broke traction, as soon as all 4 wheels gripped again they were back in sync.
It isn't witchcraft
I get what you mean, but what I can't get my head around is if - basically - one of the engines is 'weaker' than the other and as you (rightly) say they're connected by the road, won't the weaker one essentially be freewheeling, being pushed along by the stronger one? If you think about it in an extreme condition, if one of the engines seized, it would slow the car/bike, so would actively slow the other one as it'd have to work against it. Obviously that's an extreme, but if one can't keep up, surely it's adding nothing to the performance?All the 'old' twin engine cars like the 2 x VR6 golfs etc had literally only a throttle cable linking the two engines, and a cable change linking the 2 gearboxes, that was it.
There was no other electronics involved.
The revs/speed of the two engines were kept in sync my the road connecting them together.
Even if they broke traction, as soon as all 4 wheels gripped again they were back in sync.
It isn't witchcraft
I do know there's an answer as to how they work because a powertrain engineer at work is building a flat square four 1000cc two-stroke motorbike and is synching two flat twin engines. I asked him the same question, he spent about ten minutes explaining it and made me even more confused than when I started
Top project though OP
ETA; to use your example of a strong and weak person pushing a car. If instead of strong/weak you had a sprinter and a walker pushing the car at their full speed (hard to imagine, but you know what I mean!) - the walker wouldn't be making much difference would he? He'd be carried by the sprinter.
I've been at the wine tonight though, so may be talking nonsense!
Edited by srob on Thursday 21st June 21:16
Ok, well in your example of a sprinter and a walker, this isn't really applicable as both engines have the same top speed.
Think of it as two sprinters who can both run at 27mph flat out, pushing a car together.
One is (dare I say it) a woman and one is a man, therefore they both accelerate at the same rate and have the same top speed, BUT, the man has physically more power.
If they both start pushing a car together, it doesn't matter who is stronger, they both add to the pushing force until they hit their 27mph top speed (or the rev limiter if you will)
At no point are they slowing each other down or pulling each other along, they are both pushing hard until they hit their top speed simultaneously.
It's the same with the twin engined Honda Pro-Karts, sometimes those engines are well out of whack with each other power wise, but turn one engine off and you will suffer a major drop in performance as you are lacking the additional push from the second engine, no matter how strong or weak it is.
No engine accelerates at the same speed constantly. It depends on the load.
Think of it as two sprinters who can both run at 27mph flat out, pushing a car together.
One is (dare I say it) a woman and one is a man, therefore they both accelerate at the same rate and have the same top speed, BUT, the man has physically more power.
If they both start pushing a car together, it doesn't matter who is stronger, they both add to the pushing force until they hit their 27mph top speed (or the rev limiter if you will)
At no point are they slowing each other down or pulling each other along, they are both pushing hard until they hit their top speed simultaneously.
It's the same with the twin engined Honda Pro-Karts, sometimes those engines are well out of whack with each other power wise, but turn one engine off and you will suffer a major drop in performance as you are lacking the additional push from the second engine, no matter how strong or weak it is.
No engine accelerates at the same speed constantly. It depends on the load.
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