You keep asking the same question, I keep giving you the same answer... I can only assume you don't believe me. Fair enough.
GMH Starfire 1.9L 4cyl interest?
Started by
_vk4akp_
, Aug 15 2012 09:03 PM
188 replies to this topic
#127
_STRAIGHTLINEMICK_
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Posted 01 July 2013 - 10:58 AM
I agree that there's not much you can do about torsional vibration apart from the flywheel and balancer. But I'd bet every dollar I have - yep, both of em - that in this case the problem is just a plain old secondary imbalance and could be markedly improved by pulling some reciprocating weight out.
Yep I agree Johnno, I think i said that in ihe previous post .The inherrent inline 4cyl balance problems are almost impossible to stop without major engineering changes .Most successful mitsubishi 4cyl race engines had balance shafts removed. Ensure the engine and trans are soft mounted to insulate the vibration from the driver , get it to go as fast as u can and enjoy it.
Edited by STRAIGHTLINEMICK, 01 July 2013 - 10:59 AM.
#128
Uncle Chop Chop
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Posted 01 July 2013 - 09:43 PM
They say you don't learn anything from the second kick from a horse.You keep asking the same question, I keep giving you the same answer... I can only assume you don't believe me. Fair enough.
#129
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Posted 02 July 2013 - 08:37 AM
You keep asking the same question, I keep giving you the same answer... I can only assume you don't believe me. Fair enough.
Its not that I dont believe you,Its more of me trying to get a better grasp of things in my own mind before I do things.
Sorry if it comes over that I doudt you,I am only a simple country hillbilly. 
#130
_oldjohnno_
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Posted 02 July 2013 - 10:27 AM
No worries, I have no problems with being thought to be wrong. Just that we didn't seem to be getting anywhere.
#131
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Posted 04 July 2013 - 03:21 PM
#132
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Posted 05 July 2013 - 08:23 AM
^^^ WTF,wouldnt that weaken the crank so much that it would break?
#134
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Posted 08 July 2013 - 12:31 PM
Yes I have heard of people boreing the pins on a six but as far as I know it was never fitted and tried for
some reason.
I have reduced the reciprocating weight by as much as practically allowable but I still dont think it will be enough
to come close to some sort of reasonable balance factor.
I think these things will need some extra weight on the counter balance weights but the popular opinion seems to be
that a mirror image crank does not need to use any sort of balance factor because of the fact that there is the same amount
of weight on each side.
Could someone expain in a simple semi scientific manner how on this earth that this type of crank can actually be balanced
if the pins are heavier than the counterbalance weights and one pair is 180 apart from the other pair?.
And how using as much flywheel as possible would actually overcome the balance problems these thing have?
#135
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Posted 08 July 2013 - 04:17 PM
#136
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Posted 09 July 2013 - 08:56 AM
I would say with numbers like that the centreline would look more like the thick bent black line when its spinning?
#137
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Posted 20 July 2013 - 08:46 AM
That thing's got to be well under-balanced, I'm sure if you could pull some weight from the pistons, pins and rods you'd see some improvement.
Well observed,,,and just by looking at a picture.If my numbers are correct it is underbalanced by quite a bit,up in the 100's.
#138
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Posted 08 November 2013 - 08:30 PM
I've rencently read, that opel have made a turbo 3 cyl for the adam, without balance shafts, the way they got the engine (opositionally?) balanced, instead of counter rotating shafts was to put heavy weigbhts on certain sections of both the crank pulley and flywheel.it seems that this is a very interesting way to get the job done@ is there anyone got an Idea how we would go about this on a starfire? Instead of more difficult counter rotating shafts?
#139
_Bomber Watson_
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Posted 08 November 2013 - 08:34 PM
So externally balanced like 400ci small blocks and 454 big blocks?
Not new....And not balanced lol.
Could help though i suppose?
On that note, would a ludicrously heavy balancer and flywheel help one of these engines?
I wont suggest the torque converter acting like a fluidampner for these engines as im sure in any form they wouldn't make enough grunt to be suitable for a slush, stick only for these jiggers.
Cheers.
Edited by Bomber Watson, 08 November 2013 - 08:35 PM.
#140
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Posted 08 November 2013 - 08:40 PM
Actually i owned a vh wagon with a starfire traumatic, bloody good car, u might be into something there. 454's are externally balanced in the same manor? But poorly?
I never noticed any vibrations.
I never noticed any vibrations.
#141
_Bomber Watson_
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Posted 08 November 2013 - 08:48 PM
400 sb's and 454 big block are externally balanced yes.
Im not sure this idea would work with a flat plane crank like a starfire crank though, now that i think of it some more.
I kinda think that getting as much weight out of the slugs rods pins and rings and as much weight on the flywheel would possibly work...Ie balancer off a C15 cat and a flywheel off a frOcking tractor.....
Cheers.
#142
_oldjohnno_
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Posted 09 November 2013 - 07:17 AM
I've rencently read, that opel have made a turbo 3 cyl for the adam, without balance shafts, the way they got the engine (opositionally?) balanced, instead of counter rotating shafts was to put heavy weigbhts on certain sections of both the crank pulley and flywheel.it seems that this is a very interesting way to get the job done@ is there anyone got an Idea how we would go about this on a starfire? Instead of more difficult counter rotating shafts?
The Adam engine has a single balance shaft. As a 3 cyl it is also inherently better "balanced" than a four (which in effect is just a big 180deg twin).
If you want to smooth out a starfire forget about balancing; it simply can't be done. It doesn't matter where you put the weights, it just isn't possible. Forget that you've even heard the word balancing and lighten the pistons/pins/rods. The factory parts are heavy so there is potential for massive improvement.
Bombers suggestion of heavy flywheels would help slightly in two ways - firstly (and only slightly) by helping to reduce the velocity fluctuations thru TDC. And secondly (and more noticeably) by increasing the mass of the engine as a whole.
But really, just get some light components in there and the vibration will no longer be bad enough to be a problem.
#143
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Posted 09 November 2013 - 10:43 PM
Righto! Thx for picking me up on that johnno!, twas actually the ford ecoboost 1l 3cyl thats externally balanced.
Righto! Thx for picking me up on that johnno!, twas actually the ford ecoboost 1l 3cyl thats externally balanced.
Righto! Thx for picking me up on that johnno!, twas actually the ford ecoboost 1l 3cyl thats externally balanced.
#144
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Posted 10 November 2013 - 08:22 AM
Righto! Thx for picking me up on that johnno!, twas actually the ford ecoboost 1l 3cyl thats externally balanced.
It seems that Ford have taken a similar approach with their engine as others have done with single cylinder bike engines for years - ie. if it simply can't be balanced, shift the shakes to a direction that produces the least objectional results with the chosen frame and mounts.
Those problem vibrations are in a vertical direction, and Ford manages to alter that with a flywheel and pulley at opposite ends of the engine that are very specifically unbalanced - plus some crankshaft work - to redirect the vibrations fore-aft. Engineers then use sophisticated engine mountings to quell that motion.
#145
_Bomber Watson_
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Posted 10 November 2013 - 10:43 AM
In this modern day and age, why do we still design such terrible engines then proceed to reinvent the wheel trying to hide the problems?
I get it with the holden sixes, Starfire, any car engine older, old school single/twin bikes, Harley engines, all that kinda stuff, didnt really have the gear to design things like we do now.... And i understand why they still persist with modern dirt bikes and the like (size, weight), but FFS, modern cars??!!??
Cheers.
Edited by Bomber Watson, 10 November 2013 - 10:44 AM.
#146
_oldjohnno_
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Posted 10 November 2013 - 12:33 PM
In this modern day and age, why do we still design such terrible engines then proceed to reinvent the wheel trying to hide the problems?
I get it with the holden sixes, Starfire, any car engine older, old school single/twin bikes, Harley engines, all that kinda stuff, didnt really have the gear to design things like we do now.... And i understand why they still persist with modern dirt bikes and the like (size, weight), but FFS, modern cars??!!??
Cheers.
OK I'll bite.
What terrible engines are you talking about? There's been some truly brilliant engines released in the last decade or two. As far as the triples go you have to remember that as far as most current consumers are concerned any discernible vibration is too much, so it's not like they are trying to band-aid an inherent shaker, they're just putting the final polish on engines that are at least as smooth as the sixes and eights of old.
Todays factory engineers have to work within ridiculously tight boundaries for weight, bulk, emissions and noise/vibration, yet they succeed in all these as well as providing performance comparable or better than the old eights, plus a longer lifespan (thanks mainly to emissions restrictions, ironically). Most of the time you simply don't need a lot of cylinders; look at what Ducati (to name just one) can do with only two. The sweet spot for passenger car engines seems to be between 400 to 500cc per cylinder; I assume though that the engineers have used a minumum of three cylinders for NVH reasons. But you can certainly make a lot of power with a 1 litre twin.
#147
_Bomber Watson_
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Posted 10 November 2013 - 12:54 PM
Good point.
Once again i was looking at the world backwards, I was thinking they were band aiding a inherently wobly engine, Like Harley did in 99 with the solid mounted softail TC88's to stop your feet from vibrating off the pegs, instead of, as you pointed out, further refining an already suitable design so it lives up to current expectations.
On that note, i class Harleys decision as a good one, i Wouldnt have purchased a TC88B equiped bike if it was anything other than a solid mounted 45 degree air cooled pushrod v twin...If i wanted a 90 degree quad cam water cooled V twin i would have brought a Ducati, not a V Rod....
Plus the more i look at it the more i realize there really is no inherently balanced engine....Just better balanced...
Horses for Courses....
#148
_oldjohnno_
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Posted 10 November 2013 - 04:31 PM
Harleys are an interesting case and are in a way unique. Technically speaking the sensible thing to do would be to go to a 90 degree twin and forget about vibration altogether. But that simply isn't an option for HD; 45 degree vee twins that shake their heads and go "potato potato potato..." are Harley Davidson. Their knife-and-fork rod arrangement is something else that is less than ideal but again it wouldn't be a Harley if the cylinders were offset. Not to mention over a century of vee-twin tradition; something that HD's customer base hold dear. They aren't my cuppa tea but I can certainly understand the appeal.
There are inherently balanced engines - eg. 90 deg vees, flat fours and sixes, straight sixes etc. If you're interested in engine design and balancing issues look up a bloke named Fred Lanchester. He was an amazing engineer who was behind quite a few major automotive advances: disc brakes and the harmonic balancer to name only two. He devised some interesting engine layouts with perfect balance.
Edited by oldjohnno, 10 November 2013 - 04:33 PM.
#149
_Bomber Watson_
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Posted 10 November 2013 - 04:39 PM
I was under the impression no four stroke could be balanced because of different loads on the pistons during different strokes?
Ie going up under compression stroke presents different forces to going up on exhaust stroke, down on inlet stroke produces different forces than going down on power stroke.
2 strokes on the other hand...
#150
_oldjohnno_
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Posted 10 November 2013 - 05:09 PM
Makes no difference whether the forces are transmitted via the compressed charge and the cylinder head, or whether they go via the conrod, the net effect is all the same.
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