Four-cylinder V-2?

[TonyB]

I haven't exactly done a lot of reasearch into this... no doubt I'll be flamed if I'm wrong...

I've seen a couple of comments on here and elsewhere that seem to indicate that some of the V4's in MotoGP are actually firing their cylinders in pairs, effectively becoming 'Four cylinder V-2s' and giving them the power of a four with the advantages like traction etc of a V-2. They certainly don't sound like V4s, and they don't 'drone' like the old RC30 and RC45, so maybe its true?

A few years ago Yamaha released the TRX850. It was a parrallel twin that had the crank aranged in such a way that it fired like a 90° V-2. Some journalists thought that this was a brilliant solution, as it offered all the advantages and the addictive sound of the V-2 with the far lower poduction costs and ease of chassis design of the parrallel twin. The idea never took off.

So I am wondering- could the crank and ignition system of an inline 4 be arranged in such a way to make it fire the cylinders in pairs, at the same intervals as a 90° V-2? If it were possible, it would have the power of a 4, the traction and sound of a V-2, and the lower production costs of an inline 4.

[k14]

So I am wondering- could the crank and ignition system of an inline 4 be arranged in such a way to make it fire the cylinders in pairs, at the same intervals as a 90° V-2? If it were possible, it would have the power of a 4, the traction and sound of a V-2, and the lower production costs of an inline 4.

Thats what they did in british superbikes but it was outlawed straight away. Don't think they're allowed to do it in world sbk either cause its against the rules. Its what they call a "big bang" engine. Rossi's bike runs exactly that way.

[TonyB]

Cheers K14. So, I wonder why none of the manufacturers have tried making one for the street? Or even some of the people who pour money into their bikes to make them different from all the other massed produced machines- what could be more different than your R1 sounding like Rossi's M1?

[R6_kid:Me]

I read an article in a british bike mag where they trialled this on an R1, i think it was a 2003/2004 model. Two bikes, one running conventionally, one with the 'big bang' setup. The big bang bike was favourable over the conventional bike and they said the loved the sound it made over that of a conventional IL4.

Something of note for you is that some of the motoGP V4 engines run a single head as angle between the heads is quite small. This (the small angle) could be why they dont quite sound the same as a 'normal' V4.

[idleidolidyll]

Big Bang engines are not prohibited at all. They make good sense.
Bikes have been built by enthusiasts from road bikes that copy the big bang formula but to do so you need new cams, new crank/s and to reprogram the ignition and fuel injection.

It's not a simple thing.

Personally though, I'd be really interested in a production big bang motor. I hate in line 4s (too buzzy, not realistic on the road) and much prefer the better torque delivery of a vee twin. If that were overcome by a proddy big bang, I'd be first in line for a test ride.

[pritch]

Close but...

I haven't read of V4s firing like twins but Yamaha and latterly Kawasaki have their inline fours firing in "big bang" mode. From memory, one pair of cylinders fires together, two smaller bangs then the big bang again.

I read an interview with a Yamaha exec who stated that the reason they hadn't done this to a road bike was that there were concerns about long term reliability due to increased vibration.

None of this is really new, I was talking to a friend who raced TQs and he said they were looking at doing this to a TQ engine 20 some years ago.

[sAsLEX]

I read an interview with a Yamaha exec who stated that the reason they hadn't done this to a road bike was that there were concerns about long term reliability due to increased vibration.

Hardleys Aprillia and Dukes seem to manage the vibes ok

[idleidolidyll]

Close but...

I haven't read of V4s firing like twins

Honda GP riders had a choice of setting their bikes up as big bang or traditional V4's.
That was in the mid to late 90's before GP1 took over. It usally applied to their 2 strokes.

I understand Yamaha offered the same.

[Edbear]

I'd be first in line for a test ride.

Ha ha!

[Motu]

To make an inline 4 fire like a V twin it would need a 270 crank,and to make it consumer friendly (that means someone would have to buy one and not give it back) it would need a balance shaft.Same with Yamaha's one big and 2 little,it is out of balance.Rossi can handle that but a wimpy consumer never would.

It can be done with V twins too - Bill Werner,legenary tuner for Gary Scott,Jay Springsteen and Scott Parker,one time sole employee of Harleys racing deptment...used to set up Scott Parker's XR750 as a ''twingle''.This made it fire bang bang as both pistons went over TDC 45 degrees apart.He did this on wet tracks and never told Parker - the bike made the same power,but felt ''flat'',so Scott Parker would ride the bike harder to make up for what he thought was a lack of power.Bill Werner knew that Parker backed off a bit on wet tracks,this was his way of making him ride harder....not only did he know how motors worked...but minds too.

[imdying]

They used to use big bang motors in 500s... Until Mick Doohan got bored, then he went back to the screamer... it gave him a psychological and power advantage over the other riders that were too pussy to ride the screamers

Essentially, with two pairs of pistons firing together, all you've essentially done is create a vtwin with more valve area than can be managed from a regular vtwin, which is a good thing

[Motu]

With a big bang inline 4 you just make a 180 deg parallel twin with primary balance and no rocking couple....and more valve area...and just more everything.

[TonyB]

Hey, it would be a way to give cars a bit of character too, I should do it to my van....ahhhhhh, just imagine driving a shitty old Toyota van with a booming V-2 sound track

[stanko]

The big bang engine was developed for the 1992 500 GP season by honda. The theory behind the design was that the revised firing order would result in the tyre breaking grip and spinning at the moment of ignition, causing it to move outwards, but then recover gripbefore the next cycle of paired ingniion events. In this way the rear tyre would be less likley to break awayinto the kind of uncontrolled spin that would stop abruptly and highside the rider.
The firing interval was aproximatly 70°.
It was a high maintenence engine with engine cases needing replacment every 600miles.
This is just a little background to the Big Bang engine and Im not sure if it adds anything to the thread.
I think the idea of running a V4 as effectivly two V twins allows for V4 type revs and v2 power delivery.

[FlyingDutchMan]

It is relatively easy to convert a in-line 4 into a big bang bike, or one big bang two little bangs - provided the bike is running a wasted spark ignition system. To do it all you need is new cams made up so that the valves on the outside cylinders open/close at the same time, and same thing for the middle two. No changes required to anything else.

May have to watch the extra peak torque loading though.