Converting a Cross-Plane V8 to Flat-Plane
Converting a Cross-Plane V8 to Flat-Plane
(OP)
I'm looking in to converting a cross-plane V8 to a flat-plane. Specifically, the Toyota/Lexus 1UZ. I understand the basics of difference between the two configurations but was looking for recommendations on engineering the balance shaft(s).
I have the CAD/CAM, engineering and machining/welding capabilities but need to figure out those balance shafts. Anyone know of any texts that cover the secondary vibration characteristics of flat-plane V8's? Or perhaps someone knows the specs on the bottom end of Lotus' Espirit, Ferrari's Modena or the TVRs?
I've got a couple of friends that can handle the ECU, ignition and fuel injection but would cherish any advice you folks may have....
I have the CAD/CAM, engineering and machining/welding capabilities but need to figure out those balance shafts. Anyone know of any texts that cover the secondary vibration characteristics of flat-plane V8's? Or perhaps someone knows the specs on the bottom end of Lotus' Espirit, Ferrari's Modena or the TVRs?
I've got a couple of friends that can handle the ECU, ignition and fuel injection but would cherish any advice you folks may have....





RE: Converting a Cross-Plane V8 to Flat-Plane
Mike Halloran
Pembroke Pines, FL, USA
RE: Converting a Cross-Plane V8 to Flat-Plane
Are you sure the existing system is robust enough for the increased duty?
RE: Converting a Cross-Plane V8 to Flat-Plane
Since the secondary imabalance is along the cylinder axis you >>might<< need a pair of 2x encrank speed counter-rotating balance shafts for each bank. Serious complication to simplify exhaust manifolding
RE: Converting a Cross-Plane V8 to Flat-Plane
Fabrico -- based on the Toyota Supra's block being capable of +1000 HP I'm GUESSING this block should handle it. Do you think perhaps the crank bearings won't have the area necessary to resist the unbalanced forces?
Tmoose -- I'm not really after the simplified exhaust... more along the lines of the decreased rotational mass (throttle response), the oh-so-beautiful sound and for sheer uniqueness...
RE: Converting a Cross-Plane V8 to Flat-Plane
Mike Halloran
Pembroke Pines, FL, USA
RE: Converting a Cross-Plane V8 to Flat-Plane
RE: Converting a Cross-Plane V8 to Flat-Plane
Mike Halloran
Pembroke Pines, FL, USA
RE: Converting a Cross-Plane V8 to Flat-Plane
First you need to work out your effective forcing function. Then you need to design eccentric masses to give the same forcing function.
All the equations are in Theory of Machines and Mechanisms by Shigley and Ucker, or you can do it from first principles.
Then you need to figure out where to put them.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Converting a Cross-Plane V8 to Flat-Plane
You should have used, "theonlyroadnottaken." Your project, your money; however, of all the possible modifications one could make to that engine, a 180-degree crankshaft with balance shafts is the greatest investment of time and effort for the least return I can imagine. It will be unique.
Keep us posted as you work through the project.
thnx, jv.
RE: Converting a Cross-Plane V8 to Flat-Plane
If you were to take a four position standard V-8 crankshaft and change it to a 180 degree two position crank, you would introduce uneven firing impulses (instead of one every 90 degrees). Hmm, it seems to me you would be introducing more vibration than you are trying to eliminate.
Somewhere, there would be 4 cylinders with 180 degrees firing impulses, followed by 4 others. I visualize a master/slave cylinder relationship.
I can think of better ways to spend a couple of hundred grand, and you would get more power and a better sounding exhaust with exhuast tuning.
Franz
eng-tips, by professional engineers for professional engineers
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RE: Converting a Cross-Plane V8 to Flat-Plane
http://en.wikipedia.org/wiki/V8
RE: Converting a Cross-Plane V8 to Flat-Plane
RE: Converting a Cross-Plane V8 to Flat-Plane
The racing engines were not as constrained by 1)the need for better balance and 2) the better fuel distribution that a dual plane intake manifold provides with a central carburetor mount.
The availability of independant fuel injectors solved the latter problem and your no holds barred approach to cost should permit you to whittle a strong crank from a big chunk of sturdy steel.
Sound? You want sound? Take the savings and make a downpayment on a P51.
RE: Converting a Cross-Plane V8 to Flat-Plane
Flat plane crank is lighter, so more performance while accelerating as there is less inertia to overcome, and it changes the firing order so that each bank fires like a normal 4 cylinder at 180 degree increments, instead of a pair at 90 degree like a cuneiform crank.
This allows for an exhaust system that is more efficient without a need to cross pipes from one side of the engine to the other.
It also means that a dual plane manifold will have a left and right hand plane rather than a top and bottom plane.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Converting a Cross-Plane V8 to Flat-Plane
RE: Converting a Cross-Plane V8 to Flat-Plane
regards, Steve
RE: Converting a Cross-Plane V8 to Flat-Plane
i am going to put a flat plane crank in a 3uz.
i am going to use a balancer from a company in san diego. it is not a secondary balance shaft but a balancer to put onto the crank out front. looked for a balance shaft, couldn't find one for this engine or one to adapt to this engine. ferrari uses one. i'll look up the company, can't remember the name. would love to have a balancer shaft though.
wes
RE: Converting a Cross-Plane V8 to Flat-Plane
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Converting a Cross-Plane V8 to Flat-Plane
A well respected balance shop balanced a race shop's enlarged by stroking 4 cylinder Opel motor. It shook so violently the intake manifold would not stay on. Settled out of court. Really the balance shop was blameless. Vibration analysis would almost certainly have revealed the heavy vibration was at 2X rotation, not 1X (where "balancing" can help).
The secondary vibration was made worse if the cranks was "stroked" and original length rods were used. Heavy pistons aggavate secondary imbalance too.
RE: Converting a Cross-Plane V8 to Flat-Plane
It probably would be easier and cheaper to find a engine that is already made that way, but if you want to convert and need balance shaft calculations, this site is for you:
ht
you may have to do some modifications to the formula, because it is for v-twins, but the shafts will act the same. they will have to be proportionate to the weight, sit opposite to each other one the same plane as the crank, and spin in the opposite direction twice as fast as the crank. its pretty simple once you see it in action. the moto guzzi is the one that has a flat plane design.