Thoughts about converting a 65º V to 90º

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humble sabot
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Thoughts about converting a 65º V to 90º

Post by humble sabot » Sun Jan 28, 2018 1:49 am

So, i'm mulling around the idea of using a motorcycle V4 in a car project and there are a few possible choices. At minimum I want to convert it to dry sump oiling since moto sumps and crankcases are so tall, considering the way they are cast there are a lot of things to modify, and perhaps dumping the whole lower crankcase and building a bespoke one with some of the sumpwork designed-in would make a lot of sense, size and weight wise.
One thing I've discovered is that 90º is not necessarily a default for strong V4s, narrower actually works quite well in some ways for packaging in a bike, but isn't quite as interesting in a car.
I suppose the question I'd like to throw out there would be: since changing the V angle would change the effect of the firing order on the balance and vibration, what are some things to consider, that i may not have so far?
the four immutable forces:
static balance
dynamic balance
static imbalance
dynamic imbalance

Greg Locock
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Re: Thoughts about converting a 65º V to 90º

Post by Greg Locock » Sun Jan 28, 2018 4:55 am

Half a V8? Pretty horrid. If you are dry sumping go for a boxer.

Tommy Cookers
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Re: Thoughts about converting a 65º V to 90º

Post by Tommy Cookers » Sun Jan 28, 2018 6:01 pm

'changing the V angle'

otoh
would not affect the firing order but it would affect the firing intervals - beneficially
and beneficially affect the balance and so eliminate the counterbalance shaft

yes the flat 4 is the best balancewise

roon
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Re: Thoughts about converting a 65º V to 90º

Post by roon » Sun Jan 28, 2018 10:31 pm

Greg Locock wrote:
Sun Jan 28, 2018 4:55 am
Half a V8? Pretty horrid. If you are dry sumping go for a boxer.
Horrid in what sense?

Maritimer
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Location: Canada

Re: Thoughts about converting a 65º V to 90º

Post by Maritimer » Sun Jan 28, 2018 10:42 pm

Porsche spent quite a while getting the 90° V4 in the 919 working well, vibration is a major issue generally.

Greg Locock
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Joined: Fri Jun 29, 2012 11:48 pm

Re: Thoughts about converting a 65º V to 90º

Post by Greg Locock » Mon Jan 29, 2018 12:47 am

Secondary balance. V4s don't have a great rep in the UK after that nasty Ford one in the 70s and 80s.

Tommy Cookers
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Joined: Fri Feb 17, 2012 3:55 pm

Re: Thoughts about converting a 65º V to 90º

Post by Tommy Cookers » Mon Jan 29, 2018 10:30 am

the 1965-78 mainly 2 litre UK Ford V4 (60 deg for V6 commonality) was not at the time condemned for vibration ?
the firing intervals are uneven within a bank so the engine sounds rougher than it is ?
there was slightly less secondary vibration force (than an inline 4) but yes a secondary vibration moment
and the single primary counterbalance shaft can't do a perfect job because of its position ?
btw
the similar Ford Germany V4 1.2 - 1.7 litre of 1962-81 was planned (then abandoned) as the Ford USA Cardinal fwd compact
and even turbocharged to 200 hp in one version of the Saab 96

a V4 for a car will have even firing intervals - which means 4 throws and cylinders probably rather spread out
isn't the argument against a car V4 (without V6 production commonality) the extra cost ?
though Zaporozhet chose to make their people's car an aircooled 90 deg V4

the motorcycle V4 will have 2 throws and so close cylinder spacing that helps re secondary vibration moments
(and the 90 deg V angle here of course gives counterbalancing of the primary vibration forces at source)
presumably the OP has decided whether it's to be solidly or elastically mounted and the layout re transmission

humble sabot
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Joined: Sat Feb 17, 2007 9:33 am

Re: Thoughts about converting a 65º V to 90º

Post by humble sabot » Mon Jan 29, 2018 8:12 pm

I know Porsche had some growing pains with the 919 platform, but I don't remember anything about the format of the engine posing problems?
The top candidate is the Aprilia RSV4. The Honda VFR 1200 is quite interesting because they've worked out an extremely smooth running motor without a balance shaft which would lend itself well to solid mounting and features a dual clutch trans and already has shaft output but would otherwise be a weird fit in a car application and require a lot more reverse engineering to drop the cg closer to the floor.

I discovered one application of the RSV4 in a car: http://griiip.com a little after finding it might have potential, if for nothing else than sound. Griiip seems much more interested in selling the G1 as a racing package than as a car so they aren't very in depth with their descriptions of how the thing is engineered but i am most curious.

I'm possibly in a small group, but i never liked the sound of a flat engine.
the four immutable forces:
static balance
dynamic balance
static imbalance
dynamic imbalance