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engine nerds: inline 4 timed as parallel twin?

ohio said:
This, but a firing order of 1-2-2-1, is what I'm asking about. It's different than the Yamaha Big Bang which has a 90 degree crank. Basically it's a new set of cams plus some ignition trickery in an existing I-4. I guess I'm surprised no one has tried the combo, but I'm sure there are good reasons for it. Hoping someone can tell me what they are.



So do you know of anyone that has done it? What was the result like?

I have no intention of doing this to my R6, but after a ton of conversations with flat trackers about the improved traction of singles & twins vs triples and fours, and the racing success of big bang fours, it just seemed like a logical thing to try.
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The reasons (whether they are good or not) depend on how the bike is being used (Or..is there a problem that needs solving).

Flat trackers had a huge problem, hooking up on dirt, to manage turning those corners at like 100 MPH.

Harley's firing order was a "Gold standard", and taking a Triumph twin, with the pistons going up and down together (but firing alternately), and just replacing the cams and ignition to make that firing together (in a big bang) was easy enough, and did the deed for flat tracking.

Big question is "what do you want to do, and what are you willing to spend in doing it?"

Nothing is free, there are trade-offs.
 
kangaroo said:
This was done in 2005 by Rob Mac's Virgin Yamaha team. It was called the Pig. The firing order was 1-2-1 at every 90 degrees. So the firing order was 1- 2,3 - 4. They found out the hard way that the power pulses at 180 was too much for the cylinder head to take. It worked so well that Haga crashed riding off the front tire first time out. WSBK promptly banned it.

You'll need 2 very pricey things to make it work on a street bike. A Motec M8 and a set of custom cams. So about $5k just to tinker. There's a guy in Australia that'll sell you the kit.
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Ah, totally makes sense at 1-2/3-4, like a triple with a bigger middle piston, especially at 90 degrees. Again, no intention of doing this to my bike... more just curious why the 180 degree versions haven't been tried by OEMs, because it seems like they would would be relatively easy to implement without the major redesign and retooling something like the cross-plane crank requires. If it's so great it was banned from WSBK, then I want it. Though no one will produce it if they can't run it in racing. Damn.
 
ohio said:
If it's so great it was banned from WSBK, then I want it. Though no one will produce it if they can't run it in racing. Damn.
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Just because it's great for racing, doens't mean it will be worth it on the street either.

Racing vehicles tend to be highly compromised.
 
ohio said:
Ah, totally makes sense at 1-2/3-4, like a triple with a bigger middle piston, especially at 90 degrees. Again, no intention of doing this to my bike... more just curious why the 180 degree versions haven't been tried by OEMs, because it seems like they would would be relatively easy to implement without the major redesign and retooling something like the cross-plane crank requires. If it's so great it was banned from WSBK, then I want it. Though no one will produce it if they can't run it in racing. Damn.
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Engine design right now is following motogp and relying more on electronics than the mechanics. A race team relied on ingenuity and simplicity.
 
The BUB streamliner engine (worlds fastest m/c ) is a good example of big bang. From their site...

The Engine: The BUB Seven is powered by a custom V-4 engine. This engine is purpose built for motorcycle land speed racing. From a blank sheet of paper this engine was designed for one thing, power the world's fastest motorcycle.

The maximum limit for this land speed racing is 3000cc. The engine also needs to fit in a space 18 inch x 28 inched so part of the initial design is to fit this compact space. The V-4 concept was used for two reasons, one to fit into the packaging and two the unique surface of the salt flats requires a engine with traction control. The engine is a big bang type so that the engine can gain traction then relax and then transfer power with the next power pulse.


Denis told me at speed, the thing fires every forty five feet to keep from overwhelming the tires traction.
 
Cereal KLR said:
Denis told me at speed, the thing fires every forty five feet to keep from overwhelming the tires traction.
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That is actually really interesting and useful info. Any idea how fast that is?

And just to clarify, by true big bang are you talking about all cylinder firing at exactly the same time or firing 2 then 2?


Edit:

From looking at the crank, it looks as though it is a 2 and 2 firing - one bank firing at the same time then the other firing.
 
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sliverstorm said:
Anybody who skipped this article, read it. The big bang theory appears to be incorrect, as previously discussed in this thread, and this article describes the real advantage. :thumbup
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ya i wish this website article had the illustration of the magazine, the side view of a rear tire and how the different firing patters appear on the circumference really show how smoother firing of the pistons provides better acceleration and traction, it also compares the v4 of the aprillia and the ducati to the i4 patterns (bmw yamaha and the other jap engines)
 
I'd like to throw in that the theory behind the 'big bang' recovering traction appears to be sound, from my experience.

I had a thumper last year that was so wily and torquey, going through a deep lean if you open up the throttle, you could feel the tail step out just a little every power pulse, but it would grip once the pulse was over. Not nearly as much power as a I-4 or V-4, but you better believe it was 'big bang' in the purest of senses :teeth

Whether it actually results in increased or decreased performance, I cannot say. I personally suspect the people attributing performance gains to the 'regaining traction' period are confused and attributing the performance gain to the wrong side-effect.
 
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sliverstorm said:
I personally suspect the people attributing performance gains to the 'regaining traction' period are confused and attributing the performance gain to the wrong side-effect.
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When you say "the people" you mean top level pro racers, right?
 
Cheyenne said:
When you say "the people" you mean top level pro racers, right?
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Yup. All they have to know is that it works, not exactly why it works.

Not that you should believe me. I have no proof, that's just my opinion :teeth


Well, I have a little proof. Thumpers should corner just as well if not better as V's if the 'big bang' theory is really correct- in fact they should corner best of all motorcycles- as they only have 1 bang per 2 engine revolutions. But they don't, at least not that I've heard of.
 
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sliverstorm said:
Well, I have a little proof. Thumpers should corner just as well if not better as V's if the 'big bang' theory is really correct- in fact they should corner best of all motorcycles- as they only have 1 bang per 2 engine revolutions. But they don't, at least not that I've heard of.
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How much of a difference are you looking for? It's gonna be small no matter what.

Ducati SuperMono. :x


Edit: Crap, now just thinking about it I have to go drool at pics...where's my tissue?
 
sliverstorm said:
Thumpers should corner just as well if not better as V's if the 'big bang' theory is really correct- in fact they should corner best of all motorcycles- as they only have 1 bang per 2 engine revolutions. But they don't, at least not that I've heard of.
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Singles hook up better in dirt. Twingles were better than the Harley twins in flat-track (as mentioned above)
 
ohio said:
Singles hook up better in dirt. Twingles were better than the Harley twins in flat-track (as mentioned above)
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Harleys were the first "twingles" as the change could be made by removing the timing cover and re-timing the cams if track conditions warranted it.
 
sliverstorm said:
Yup. All they have to know is that it works, not exactly why it works.

Not that you should believe me. I have no proof, that's just my opinion :teeth


Well, I have a little proof. Thumpers should corner just as well if not better as V's if the 'big bang' theory is really correct- in fact they should corner best of all motorcycles- as they only have 1 bang per 2 engine revolutions. But they don't, at least not that I've heard of.
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Actually...the best Racers, know the why...That's how they get there.

They are Legends Like Rossi and Kenny Roberts and Mert Lawill (sp) and a list of MotoCross and Flat track champs.

They tried everything (design wise). They assist in development. They can because they know the why.

And your wrong about thumpers cornering, As a blanket statement. It depends on where they are being used. What speeds (which is also engine speed).
 
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xlcr said:
Harleys were the first "twingles" as the change could be made by removing the timing cover and re-timing the cams if track conditions warranted it.
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You completely lost me. How do you turn a single crankpin V-twin into a twingle? You can create a long-bang but they can't fire at the same time.
 
JO EBRMC said:
You completely lost me. How do you turn a single crankpin V-twin into a twingle? You can create a long-bang but they can't fire at the same time.
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You don't (can't) turn a Harley twin into a twingle (so your right, not lost).

Twingle was a Triumph twin, re-cam-ed, to have both pistons (which went up and down together anyway) doing the same thing at the same time,, and acting like a single.
 
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