The Technical Questions Thread

[Matra et Alpine]

ht, your ideas are insane for bike packaging
First there aern't any boxer 4 bike engines. BMWs are twins.
So when you said 4, sorry for assuming you meant inline 4 and thus why - totally logically - I pointed out the issues with that layout.

OK, now lets look at boxer 4 laid across teh bike ( you should always talk about an engine from it's crank perspective ).
So pray tell ... HOW do you cool the rear pistons ? How are you routing the exhausts ? and the intakes ? Finally HOW are you taking the drive off the engine to the gearbox ? WHERE are you putting the box ? All obvious failins of the approach. AND why the last opposing cross-crank engien was in a 200cc motorbike used in the UK by the police in the 50s ... mates got one and it's clearly an engineering dead end

Thinking on my feet, I woudl be very concerned about the effect of the boxer crank on braking and accelration as it will now pitch the bike front/rear on revs. The idea of the engine revs lifting the front wheel gives scary image of wheelies at every corner or even workse if spinning the other way of lifting weight from the rear, reducing grip and drive

To cover some fo the other "stuff" ... wish you'd think optiosn through 100% ... so you suggested to Leaon the length is easily solved by shortening the stroke ? So that has to now have an equivalent increase in bore which ... THEN makes the engine WIDER. Remember the idea was this coudl be a narrow design ?

Also forgetting that the narrowest part needs to be at the bottom of a race/sports bike. It's OK for H-Ds to be low and wide because they don't go round corners fast with lots of lean.

THere is no benefit in narrowing the top part of a bike. THe rider becomes the determine factor on width up there. It's lower down where the shins and knees are that makes the biggest difference.

I like you're thinking laterally ( pun intended ) BUT if you woudl try to collect all the "solutions" to all the issues then the trade-offs and engineering problems will quickly show why competition bikes are the way they are

[NSXType-R]

Slightly off topic, but how do Corvette turbochargers work?

The ones with the turbo mounted in the exhaust system, towards the rear of the car.

I understand it helps with heat dissipation, but how is it linked up? A long shaft?

[Rasmus]

Originally Posted by NSXType-R

Slightly off topic, but how do Corvette turbochargers work?

The ones with the turbo mounted in the exhaust system, towards the rear of the car.

I understand it helps with heat dissipation, but how is it linked up? A long shaft?

I assume you mean the STS kits. Same as other turbos; piping, and lots of it.

Here's a TT kit for the C6:
http://www.jlturbo.com/pictures/sts/...-sts-turbo.jpg

And a 4th gen Camaro:
http://i177.photobucket.com/albums/w...maro-pipes.jpg

And just to be ridiculous, here's the TT Mustang GT kit:
http://www.mustangv8.com/en2/uploads...517c49e78f.jpg

[clutch-monkey]

what's the disadvantage? apart from peopel nicking your turbo's?

[cmcpokey]

Originally Posted by clutch-monkey

what's the disadvantage? apart from peopel nicking your turbo's?

i would imagine that having to push the air so far you would have a lot of efficiency losses.

[fpv_gtho]

Originally Posted by clutch-monkey

what's the disadvantage? apart from peopel nicking your turbo's?

Lag, lag, lag, lag, lag and lag. First theres all that piping to the back of the car, then its got to go all the way back. Must do miracles for throttle response.

[clutch-monkey]

what's the point then? no space in the engine bay?

[cmcpokey]

Originally Posted by clutch-monkey

what's the point then? no space in the engine bay?

pretty much.. probably dont have to worry about an intercooler either.

[hightower99]

Originally Posted by Matra et Alpine

OK, now lets look at boxer 4 laid across teh bike (you should always talk about an engine from it's crank perspective ).

I was referring to the crankshaft's main axis. Hopefully you read the bit when I described the situation in relation to how BMW places their flat twin engines. Basically the crankshaft is positioned just like it would be in a bike using an inline 4, but now its a flat 4 boxer.

Originally Posted by Matra

So pray tell ... HOW do you cool the rear pistons ?

IIRC MotoGP bikes are water-cooled and balancing the cooling between the forward piston pair which gets a good deal of cooling air and the rear piston pair that doesn't, shouldn't be too difficult.

Originally Posted by Matra

How are you routing the exhausts ? and the intakes ?

Exhaust can be routed under the engine and bike almost exactly the same way as any conventional engine is. Intake can be routed in through a ram-air box up top and fed down directly into the engine (as there will now be more free space).

Originally Posted by Matra

Finally HOW are you taking the drive off the engine to the gearbox ? WHERE are you putting the box ?

Gearbox can be situated where it normally is. Drive can be transmitted in almost the same way (it may need an extra gear or two to reach). Maybe if you took a minute to look at current MotoGP bikes without the fairing on them you would see that there is alot of space to use.

Originally Posted by Matra

Thinking on my feet, I woudl be very concerned about the effect of the boxer crank on braking and accelration as it will now pitch the bike front/rear on revs. The idea of the engine revs lifting the front wheel gives scary image of wheelies at every corner or even workse if spinning the other way of lifting weight from the rear, reducing grip and drive

I am not quite sure I understand... The crank is orientated exactly the same way as all current MotoGP bikes, the torque reactions will be almost the same as all the other engines (i.e. exactly the same as the 4 cylinder engines and slightly different from the 3 and 5 cylinder engines).

Originally Posted by Matra

so you suggested to Leaon the length is easily solved by shortening the stroke ? So that has to now have an equivalent increase in bore which ... THEN makes the engine WIDER. Remember the idea was this coudl be a narrow design ?

Yes except what I said was that because the engine is already short stroke (i.e. total displacement is set at 990cc and it is a 4 cylinder engine we are talking about) that the engine would not be too long in the first place. I don't think that the engine will need different bore or stroke dimensions compared to the other 4 cylinder engines in MotoGP.

Originally Posted by Matra

THere is no benefit in narrowing the top part of a bike. THe rider becomes the determine factor on width up there. It's lower down where the shins and knees are that makes the biggest difference.

A rider's knees are pretty high up on the side of the bike when they need to tuck in and the feet are towards the rear of the bike. I could imagine that it would be possible to make the area between the riders knees narrower, allowing him to tuck in tighter and present less frontal area. The area where the rider's feet are shouldn't change at all (remember the gearbox is kept in the same position).

Originally Posted by Matra

I like you're thinking laterally ( pun intended ) BUT if you woudl try to collect all the "solutions" to all the issues then the trade-offs and engineering problems will quickly show why competition bikes are the way they are

Maybe you now understand that the whole point was simply to create discussion about the actual engineering problems that would need to be dealt with...? The point was never to prove anything or to even present a solution, just an interesting suggestion that unfortunately was too easily pushed aside without any real discussion.

BTW: Can you really tell me how competition bikes are? Even MotoGP has 3, 4, and 5 cylinder engines IIRC.

Originally Posted by clutch-monkey

what's the point then? no space in the engine bay?

They are normally used when you have a big engine in a cramped engine bay. It is a cheap and effective way to run low pressure FI on large engines.

Contrary to popular belief (it seems) these systems are not inefficient or laggy when designed properly. The require a different approche then if you where making a turbo system where the turbos could be situated in the engine bay.

I for one would opt for an STS-like turbo system over say a centrifugal supercharger...

[Matra et Alpine]

ROFLMAO

Have you been anywhere near a sports bike ?
I've been going to the Isle of Man TT for the last 10 years.
There you get to walk the paddock 24/7, talk to mecnahincs, riders everyone.
It's THE pinnacle of bike motorsport.

You are really dousing yourself with gas this time .. even more than in the past.
Every point WRONG. Every "example" WRONG. Every "inference" WRONG.

I'm not wasting time going over it. Go study and look at practical. and no you cannot effectively cool a flat box 4 rear cylinder ... the demand in the water routing and the radiator would creat such huge frontal area !!

and as for "exhauset below engine like current" ... erm NON of those are trying to take the exhaust fomr a boxer. Try and just sketch it .. even just in your mind the problem is obvious !

The "killer" for me was you agreed that it won't actually norrow it for the rider at the top. So by your own write up realising it doesn't actually help

Refusing now to go through point by point as you are clearly well out of your knowledge and understanding zone.
Bikes are NOT cars with two wheels and car thinking doesn't work there

[fpv_gtho]

Originally Posted by hightower99

I for one would opt for an STS-like turbo system over say a centrifugal supercharger...

Something like this: APS Boss Intercooled Twin Turbo Performance would be better than either.

[hightower99]

Originally Posted by Matra et Alpine

I'm not wasting time going over it. Go study and look at practical. and no you cannot effectively cool a flat box 4 rear cylinder ... the demand in the water routing and the radiator would creat such huge frontal area !!

Really so your opinion is that it is impossible to cool the rear cylinder pair of a flat 4 boxer engine in a bike without increasing the radiator size by a huge amount and because the water routing would be too complex (meaning space consuming right?). What calculations did you base that off of?

Originally Posted by Matra

and as for "exhauset below engine like current" ... erm NON of those are trying to take the exhaust fomr a boxer. Try and just sketch it .. even just in your mind the problem is obvious !

Sorry this "obvious" insurmountable issue is not apparent to me...

Originally Posted by fpv_gtho

Something like this: APS Boss Intercooled Twin Turbo Performance would be better than either.

Well sure if there is room for it then getting the turbos as close as possible is better for high power applications. Have you seen the magic they can do with the E46 M3 at Horsepowerfreaks? mind-boggling!

[LeonOfTheDead]

Originally Posted by hightower99

Well sure if there is room for it then getting the turbos as close as possible is better for high power applications. Have you seen the magic they can do with the E46 M3 at Horsepowerfreaks? mind-boggling!

No, it isn't better, because the pressure waves would reflect in the combustion chamber instantly, and it would decrease the ability to overfill the combustion chamber with less depression in the exhaust manifold due to the presence of the turbine.

[hightower99]

Originally Posted by LeonOfTheDead

No, it isn't better, because the pressure waves would reflect in the combustion chamber instantly, and it would decrease the ability to overfill the combustion chamber with less depression in the exhaust manifold due to the presence of the turbine.

Obviously the turbo system has to be designed properly. How do you know the pressure waves would reflect into the combustion chamber instantly? Are you talking about pressure waves from the exhaust or intake system? By "overfill" I assume you are talking about scavenging? That is primarily controlled by valve-timing which is also changed when you change to an FI system.

Check out this site: here.

look at the design and how they tried to get the turbo as close as possible...

[LeonOfTheDead]

Originally Posted by hightower99

Obviously the turbo system has to be designed properly. How do you know the pressure waves would reflect into the combustion chamber instantly? Are you talking about pressure waves from the exhaust or intake system? By "overfill" I assume you are talking about scavenging? That is primarily controlled by valve-timing which is also changed when you change to an FI system.

Check out this site: here.

look at the design and how they tried to get the turbo as close as possible...

Obviously I was talking about the exhaust manifold.
And I said "instantly" because, considering the speed those waves reach, and the distance they would have to cover if the turbine was mount so close to the exhaust valves, the time required would be near zero.
I'm not saying the system doesn't give you advantages, but that the overall efficiency wouldn't be "the best" possible.
Also, what we aren't considering in examples like these are emissions, engine's behavious at low rpm, a lot of factors apart from he obviously increased power, which differentiate a good engine from a powerful one.