SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: SomeThingWilder on August 30, 2015, 09:10:18 PM
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Inform me of your beliefs please!!
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Wow !!! Well that depends on what you want to do with your boat??? If it's just a ski boat and family oriented a flywheel fits the bill . Now you want to race around and hot dog it !! Flexplate is the only way to go!!
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Wow !!! Well that depends on what you want to do with your boat??? If it's just a ski boat and family oriented a flywheel fits the bill . Now you want to race around and hot dog it !! Flexplate is the only way to go!!
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Just to get the party started.
What does the flywheel have to do with power?
;D
GT
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Flywheel
Sent from McIntyre park
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Flex plate can let go over 5 k
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Here's my personal theory.
Anything that is going to run more than an hour at a cruise, or idle for 20 minutes at a shot, should have a flywheel.
Anything that idles for only a few minutes and runs wot for short stints can get away with a flexplate.
A flywheel is easier on parts.
A flywheel has fewer starter issues.
A flywheel runs smoother and can idle lower with big Cams.
GT
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Flex plate can let go over 5 k
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??? Im scratchin my head on this..O0
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I would also like to be educated on how flywheels are easier on parts?? Cus it seams to me its just more reciprocating mass on the the crankshaft...kinda outside the subject but i put scattershields in all my gear cars because i know anything meant to have a flywheel in it isnt easy on parts!! Lol
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You can do that I ve had them come apart at 5500 rpm and rip threw the boat like a saw blade
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You can do that I ve had them come apart at 5500 rpm and rip threw the boat like a saw blade
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TCI has them for what ever rpm you need. China shit might be a problem. I run. 10000 rpm plate on my boat no worries
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You can do that I ve had them come apart at 5500 rpm and rip threw the boat like a saw blade
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stop buying flex plates at harbor freight. 😜 what does it mean when they say SFI?
"RTCP"
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I don't run China a flex late has no strength without the torque converter hooked to it not here to start a fight
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I have Sfi flywheel not harbor freight
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I don't run China a flex late has no strength without the torque converter hooked to it not here to start a fight
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then you must have a different problem if they are coming apart at 5500, I'm spinning my motor 72-7300 no problems with flex plates
"RTCP"
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Ok I know of some it happen to besides me so not trying to start a fight or arguments over this
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I would also like to be educated on how flywheels are easier on parts?? Cus it seams to me its just more reciprocating mass on the the crankshaft...kinda outside the subject but i put scattershields in all my gear cars because i know anything meant to have a flywheel in it isnt easy on parts!! Lol
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Flywheels are designed to deaden harmonics. The added mass, (when balanced properly) provides a smooth centrifugal gyro. It takes the impact out of driveshaft components and removes a lot of the hammering due to a large camshaft.
A stick car has impacts and high torque changes not seen in a jet pump.
Literally the ONLY positive thing a flexplate does is increase the ability to rev quicker out of the hole. I doubt seriously anyone on here could tell the difference from one to the other. The pump has something to do with it also, if your spinning a stainless impeller, the mass may male a difference, but we're talking milliseconds.
The marathon boats run aluminum flywheels in most cases.
You do see flexplates, but they're the ones that typically have starter issues.
I'm not sure about the flexplate alone coming apart at the upper rpm, but suspect there was something else causing these failures.
JMO
GT
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I ran a flexplate on my olds. It definitely made for more vibration at idle, but revved a lot faster. It handled 5k without sawing through my hull... Motor is still running tits. Rev limit was set at 5100
I don't always prefer fast revving for the olds, but when I do... I prefer Dos Equis
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I ran a flexplate on my olds. It definitely made for more vibration at idle, but revved a lot faster. It handled 5k without sawing through my hull... Motor is still running tits. Rev limit was set at 5100
I don't always prefer fast revving for the olds, but when I do... I prefer Dos Equis
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Revved a lot faster in the water, or on the trailer?
GT
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Ha!! Yah I have a flywheel , and it does slow down the revs . Throttle response is slowed . And yes it will numb the shakes .
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There are a few things that I would like to point out.
First and foremost is the difference between internal and external balance. The first picture is of the external balance counterweight on an OEM 454 flexplate. External balancing is done because of improperly designed counterweights on the crankshaft. Not enough mass was added to the counterweight, most likely because of the manufacturing process, but could also be because heavier (larger) pistons and rods were installed.
External balancing is, by far, much more economical than internal balancing. External balancing can be achieved by adding a welded or bolted (2nd picture) counterweight to a flywheel of flexplate, drilling holes or machining slots 180-degrees opposite of where the mass needs to be added, or a combination thereof. Removing material rather than adding material allows for an ultimately lighter rotating assembly.
IMO, external balance is acceptable for stock and mild performance engine builds only. This is because of the imbalance of the flywheel/flexplate (and damper) being placed on the ends of the crankshaft, unsupported by bearings on both sides, as is the case with the crankshaft's integral counterweights. Any serious effort build should be internally balanced.
A note on balancing an engine. If I am building an external balance engine, I will balance the crankshaft with the damper and flywheel/flexplate installed. In an internally balanced application, the flywheel/flexplate and damper/hub get balanced independently of the crankshaft. I want to make sure that all are a true neutral balance, should I ever need to change a component.
Some engines have options to run different diameters (tooth count) flexplates/flywheels. My 3rd and 4th pictures illustrate the difference between the Chevy 168 tooth wheel and the 153, which equates to about 1.344-inch difference in diameter. 12.844-inch diameter for the 153 tooth and 14.188-inch diameter for the 168 tooth wheel. I prefer the small wheel for two reasons, 1. Reduced inertia and 2. Increased cranking RPM.
The two flexplates pictured weigh about the same because the smaller SFI approved plate is made from slightly thicker 4130 chromoly, however it will theoretically allow the engine to rev faster because of the reduced inertia. "Inertia is the resistance of any physical object to any change in its state of motion including changes to its speed and direction or the state of rest" ( https://en.m.wikipedia.org/wiki/Inertia). More specifically, "rotational inertia, the property that a rotating rigid body maintains its state of uniform rotational motion. Its angular momentum is unchanged, unless an external torque is applied; this is also called conservation of angular momentum."
Inertia = (1/2)(Mass)(Radius^2)
Basically, the more weight that can be removed from the outside diameter, the faster it can be accelerated.
I don't mean that someone could look at any one component of a system, such as a lightened flywheel/flexplate and say, "that is why this engine has such good throttle response, it has a lightened flywheel!" All else being equal, light weight pistons will have the most dramatic affect as will anything that can be done to reduce reciprocating mass. Reducing the weight of the rods and drilling the crankshaft rod journals allows for lighter counterweights. And so on and so forth.
Regarding flywheel/flexplate cracking/breaking, I have seen a surprising lot of broken wheels of all kinds at NJBA events. I think this has to do with the conservation of angular momentum where the axis of a flywheel is not easily changed. This axis changes every time the direction and/or trim of the boat changes. I have not witnessed the same in road racing or wheel-standing drag cars. Maybe the transmission input shaft provides enough support to prevent that.
Since it took me so long to type all this on my cell phone, please excuse any redundant information.
Cheers,
Joe
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Forgot the pictures
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I had a '71 340 4-speed Duster that I spent a lot of time developing. It started life with a 30# flywheel. I had read a lot about heavy flywheels making a small block car launch like a big block car. Now, I call BS on this one.
I ran down to George at McLeod and ordered a 60# flywheel. Fortunately George talked me out of the 100# flywheel.
What I noticed, the engine revved A LOT slower, both free revving the engine and while accelerating the car. It also limited the peak RPM that the engine would rev. I couldn't believe it, all the work I had done to make it rev fast was gone!
I went back to McLeod, crying about my lost performance and George said, "yeah, that's what we expected." He said, they can lighten it for me. Trying to play it safe, I bought a second flywheel which ended up at 23#. All my RPM came back, both free revving and revving during acceleration increased, and my launch improved.
To paraphrase my favorite author, Carroll Smith, run the minimum diameter flywheel that you can hook a starter system to and the flywheel needs have only enough mass to allow the engine to idle without stalling.
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One complaint that I keep hearing about flexplates is the amount of runout they tend to have. I attribute this to being a stamped sheet metal part with a welded ring gear. Both the stamping/forming process and the welding induce stresses into the finished part. The result is that the flexplate appears to wobble while observing it with the engine running. I do believe that having a torque converter bolted to it, inside a transmission, does a lot clean up said runout.
Meziere manufactures two billet 4340 flexplates, a 168-tooth PN FPS041 and a 139-tooth PN FPS042. Josh Patridge at ISG makes a billet spoked 168-tooth flexplate (pictured). All of these are for internally balanced Chevy applications. I have not yet tried the the 139-tooth wheel yet. I do not know how much drama is involved in getting an OE starter location to work. Meziere makes some really nice starters and might offer a special starter for this application, however I have the feeling that a custom rear-mount starter, like the one pictured, might be required.
GN7, on the other hand, never felt it was worth the hassle to make a small diameter wheel work.
Cheers,
Joe
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Forgot the picture again
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Lastly, there are thickness differences between flexplates and flywheels. An OE Chevy flexplate is made from .125 (1/8") material. The SFI plate in my earlier post is .150 thick 4130 chromoly. Flywheels, on the other hand, are typically .400 thick. This 1/4"+ difference in thickness at the flange can cause clearance issues with the drive line, making a flywheel not a direct bolt-on replacement for a flexplate, without addressing drive line length.
Swapping from a flywheel to a flexplate should not be a problem, just make sure that there is enough spline engagement (one shaft diameter minimum) between the yoke and the pump shaft.
Hopefully, that's more than you ever wanted to know about the topic.
Cheers,
Joe
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I would pay ten bucks to see a back to back test on a jet from a full on flywheel to a flex with no other changes. I'm not convinced that it would make that much difference being an you ate already spinning 40+ pounds of crap in the pump.
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I would pay ten bucks to see a back to back test on a jet from a full on flywheel to a flex with no other changes. I'm not convinced that it would make that much difference being an you ate already spinning 40+ pounds of crap in the pump.
As you have stated, it is not focusing on just one small aspect of the whole. It is the whole system!
Switching from 850g+ Speed Pro ashtrays to light weight ~600g CP pistons, which usually include 1/16 or .043 light tension rings instead of the stock 5/64 rings; light weight Oliver, Carillo, or Crower rods; crankshafts with lightened and detailed rod throws and profiled counterweights; light weight lifters, valves, titanium retainers, and rockers, but heavy 7/16 push rods; and every other moving part in the engine lightened. It all adds up.
Of course, there is the snowball effect. The light weight pistons come with the benefit of an increased compression ratio, which usually corresponds to replacing the peanut port heads with something a little better flowing etc.
I think that the rotating assembly has enough mass to keep the engine idling, even without a flywheel/flexplate, if you had a way to start it. Might have to idle it up a bit.
When my friends used to build boats back in the 80s, they ran 100# flywheels to further drop the idle RPM to exaggerate the blower surge. I think that made the engine lazy. His 23% overdriven 8-71 blown & injected 509 was way more badass than mine, but his didn't have the super touchy throttle response mine has. I kept telling him, "lighten that flywheel" to which his reply was always, "make more power!" Maybe it would make a noticeable difference here, maybe not. But I agree, in the average 7.9:1 compression cement mixer jet boat, it will make no difference. Maybe if a loader is installed.
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Revved a lot faster in the water, or on the trailer?
GT
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On the trailer of course!!!! That's all that mattered for me lol
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I don't always prefer fast revving for the olds, but when I do... I prefer Dos Equis
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"now thats funny right there...i dont who you are....."
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Here's my personal theory.
Anything that is going to run more than an hour at a cruise, or idle for 20 minutes at a shot, should have a flywheel.
Anything that idles for only a few minutes and runs wot for short stints can get away with a flexplate.
A flywheel is easier on parts.
A flywheel has fewer starter issues.
A flywheel runs smoother and can idle lower with big Cams.
GT
. I have no idea what GT is talking about here. Most the time I agree with him. Lol
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. I have no idea what GT is talking about here. Most the time I agree with him. Lol
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What part loses you?
Happy to explain any of it, hell, all of it.
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GT I have a problem breaking teeth but I mostly understand it. Just having fun.
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Thanks for letting me pick the experts brains. I have a mild 468 bbc about 470ish HP . My engine builder recommend a flexplate. But after talking to Sonny Bryant from Bryant Racing he questioned why I would run a flex and not a fly and all I could say was that's what my engine builder put on.
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Thanks for letting me pick the experts brains. I have a mild 468 bbc about 470ish HP . My engine builder recommend a flexplate. But after talking to Sonny Bryant from Bryant Racing he questioned why I would run a flex and not a fly and all I could say was that's what my engine builder put on.
Why does Sonny recommend a flywheel?
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Why does Sonny recommend a flywheel?
he didn't actually recommend one he was just asking me why not a flywheel. He did explain that back when he was racing, flexplate did exactly what their names says. At high rpm without the torque converter in place they can become wobbly. But he said flexplate back then are probably a lot different the Now.
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he didn't actually recommend one he was just asking me why not a flywheel. He did explain that back when he was racing, flexplate did exactly what their names says. At high rpm without the torque converter in place they can become wobbly. But he said flexplate back then are probably a lot different the Now.
. I have noticed that they do wobble not sure that hurts anything. But we can get Joe's opinion on the or GT's.
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. I have noticed that they do wobble not sure that hurts anything. But we can get Joe's opinion on the or GT's.
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That's one of the reasons I don't like them for a recreational deal. That gyro action (IMHO) weakens the center and causes cracks.
The SFI rating on them is null and void without a torque converter bolted to them.
The torque converter bolts to the outer perimeter and there is a centering button going to the crank. No wobble.
Again, I would use an aluminum flywheel minimum, but I'm retarded.
GT
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I would pay ten bucks to see a back to back test on a jet from a full on flywheel to a flex with no other changes. I'm not convinced that it would make that much difference being an you ate already spinning 40+ pounds of crap in the pump.
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That's one of the reasons I don't like them for a recreational deal. That gyro action (IMHO) weakens the center and causes cracks.
The SFI rating on them is null and void without a torque converter bolted to them.
The torque converter bolts to the outer perimeter and there is a centering button going to the crank. No wobble.
Again, I would use an aluminum flywheel minimum, but I'm retarded.
GT
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Hi GT, strange we actually agree on something without needing a ten page "debate" . ::) But don't forget the TQ converter is also supported by the input shaft of the trans. I wouldn't want to be within 100 yards of one running with no trans to support it. I bet it would flex that plate like a wet noodle.
I ran down to George at McLeod and ordered a 60# flywheel. Fortunately George talked me out of the 100# flywheel.
What I noticed, the engine revved A LOT slower, both free revving the engine and while accelerating the car. It also limited the peak RPM that the engine would rev. I couldn't believe it, all the work I had done to make it rev fast was gone!
Where you thinking it "limited the peak RPM that the engine would rev" because the car went through the traps at a lower RPM ?
With my own boat (V-drive). Running the flywheel it idled nice/smooth/quiet. Changed to a flexplate, idle was rougher and it caused a rattle from the V-drive. Flywheel was easier on parts because it didn't try to rattle the drive.
BTW, the engine turned the exact same max RPM with either one. IMO you should see no noticeable difference in max RPM unless your so far past your HP peek that your HP curve is falling like a rock off a cliff. Car would have had a slower trap speed and hence a lower RPM through the traps because it wasn't able to accelerate the added rotational mass as quickly, but eventually it would reach the same speed/RPM.
Flexplates or even flywheels have way less rotational mass using them in a boat than they do when used in a car. In a car the flexplate would have a big heavy TQ converter (full of fluid) bolted to it, and the flywheel would have a big heavy pressure plate bolted to it. Using either one without its bolt on parts results in way less rotational mass than in a car. But you also have to add any part of the drive system that rotates with the engine when the drive/trans is in gear. That goes all the way back to the tires in a car.
Lower rotational mass will allow the engine to gain RPM faster. But your already way lower than either would be in a car. And with a jet, where it can flash to max RPM at any time regardless of boat speed the only difference would be is the time it takes the engine to rev from idle to max RPM. A split second. Its not like the engine gains RPM slowly as it accelerates the boat, like it would in a car. Rotational mass determines how quick the engine can gain RPM, not how quick a jet boat can gain speed.
Only comparable way to compare the benefits or reducing flywheel/flexplate weight/mass between a jet boat and a car would be to time how quick an automatic trans drag car can gain RPM on the line from idle to stall RPM. At WOT the jet boat goes from idle to "stall RPM" and just stays there. Do you think changing flexplate weight would change stall RPM with an automatic trans ? The only benefit would be a very slightly reduced idle to stall RPM time. And at that time, the pump isn't properly loaded, so I doubt there would be any measurable difference in boat performance.
I vote for flywheel. Get the smoother idle and reduced abuse on the U-joints and pump shaft splines.
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Hi GT, strange we actually agree on something without needing a ten page "debate" . ::) But don't forget the TQ converter is also supported by the input shaft of the trans. I wouldn't want to be within 100 yards of one running with no trans to support it. I bet it would flex that plate like a wet noodle.
Possibly, but I would think it would be limited simply because of the crank button. I guess ultimately it would depend on the balance of the torque converter and the gyro action of the fluids inside it. It will want to be locked into its rotational circle and really not want to move. Like a motorcycle wheel.
Where you thinking it "limited the peak RPM that the engine would rev" because the car went through the traps at a lower RPM ?
With my own boat (V-drive). Running the flywheel it idled nice/smooth/quiet. Changed to a flexplate, idle was rougher and it caused a rattle from the V-drive. Flywheel was easier on parts because it didn't try to rattle the drive.
BTW, the engine turned the exact same max RPM with either one. IMO you should see no noticeable difference in max RPM unless your so far past your HP peek that your HP curve is falling like a rock off a cliff. Car would have had a slower trap speed and hence a lower RPM through the traps because it wasn't able to accelerate the added rotational mass as quickly, but eventually it would reach the same speed/RPM.
Flexplates or even flywheels have way less rotational mass using them in a boat than they do when used in a car. In a car the flexplate would have a big heavy TQ converter (full of fluid) bolted to it, and the flywheel would have a big heavy pressure plate bolted to it. Using either one without its bolt on parts results in way less rotational mass than in a car. But you also have to add any part of the drive system that rotates with the engine when the drive/trans is in gear. That goes all the way back to the tires in a car.
Lower rotational mass will allow the engine to gain RPM faster. But your already way lower than either would be in a car. And with a jet, where it can flash to max RPM at any time regardless of boat speed the only difference would be is the time it takes the engine to rev from idle to max RPM. A split second. Its not like the engine gains RPM slowly as it accelerates the boat, like it would in a car. Rotational mass determines how quick the engine can gain RPM, not how quick a jet boat can gain speed.
Only comparable way to compare the benefits or reducing flywheel/flexplate weight/mass between a jet boat and a car would be to time how quick an automatic trans drag car can gain RPM on the line from idle to stall RPM. At WOT the jet boat goes from idle to "stall RPM" and just stays there. Do you think changing flexplate weight would change stall RPM with an automatic trans ? The only benefit would be a very slightly reduced idle to stall RPM time. And at that time, the pump isn't properly loaded, so I doubt there would be any measurable difference in boat performance.
I vote for flywheel. Get the smoother idle and reduced abuse on the U-joints and pump shaft splines.
Ooooooh, now you done it... :o
I have to agree. But would like to add, the horsepower draw on a jet pump until about 4,000 rpm is squat. So the abundance of excess hp could prove our theory even further. It would give the engine something to push against keeping absolute vacuum level more stable during acceleration. Just a silly thought. Would love to have time to play with it.
GT
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Possibly, but I would think it would be limited simply because of the crank button. I guess ultimately it would depend on the balance of the torque converter and the gyro action of the fluids inside it. It will want to be locked into its rotational circle and really not want to move. Like a motorcycle wheel.
Ooooooh, now you done it... :o
I have to agree. But would like to add, the horsepower draw on a jet pump until about 4,000 rpm is squat. So the abundance of excess hp could prove our theory even further. It would give the engine something to push against keeping absolute vacuum level more stable during acceleration. Just a silly thought. Would love to have time to play with it.
GT
OK, here we go. LOL
That little button on the TQ converter isn't going to do squat to keep it from flexing the plate and wobbling around. Its the rear support from the trans that keeps it all in line. Its not like the TQ converter has a 6" long precision shaft that slips into the crank. Grab a TQ converter and put it on the end of a crank, it will wobble around. The TQ converter is basically an extension of the transition input shaft as far as this is concerned. The TQ converter slips into the crank and bolts to the flexplate to center that end the same way a manual trans shaft slips into the pilot bushing. Support from both sides. That keeps the TQ converter from wobbling around, and the TQ converter keeps the outer section of the flexplate from wobbling back and forth. IMO, The added weight/mass of the TQ converter (unsupported by the trans) would exaggerate the flex of the plate till it started throwing shrapnel like a box of hand grenades. ::)
Your thoughts of a motorcycle wheel might actually apply here, but not like you think it does. If you had a severely out of balance motorcycle wheel, them balanced it by adding weight to only one side of the rim, say the right side. Eventually at some RPM it would try to flex the rim and wobble just like a flexplate. The imbalance of weight between the left and right sides of the rim will try to flex the rim in that spot to center the weight.
Hmmm, maybe the cause of the wobble with an unsupported flexplate is just that its weight is not perfectly centered (front to back) over its mounting flange. This would get really bad with an external balance flexplate that has that huge weight on one side of the plate, and an internal balance might actually not flex/wobble much at all. ???
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OK, here we go. LOL
That little button on the TQ converter isn't going to do squat to keep it from flexing the plate and wobbling around. Its the rear support from the trans that keeps it all in line. Its not like the TQ converter has a 6" long precision shaft that slips into the crank. Grab a TQ converter and put it on the end of a crank, it will wobble around. The TQ converter is basically an extension of the transition input shaft as far as this is concerned. The TQ converter slips into the crank and bolts to the flexplate to center that end the same way a manual trans shaft slips into the pilot bushing. Support from both sides. That keeps the TQ converter from wobbling around, and the TQ converter keeps the outer section of the flexplate from wobbling back and forth. IMO, The added weight/mass of the TQ converter (unsupported by the trans) would exaggerate the flex of the plate till it started throwing shrapnel like a box of hand grenades. ::)
Your thoughts of a motorcycle wheel might actually apply here, but not like you think it does. If you had a severely out of balance motorcycle wheel, them balanced it by adding weight to only one side of the rim, say the right side. Eventually at some RPM it would try to flex the rim and wobble just like a flexplate. The imbalance of weight between the left and right sides of the rim will try to flex the rim in that spot to center the weight.
Hmmm, maybe the cause of the wobble with an unsupported flexplate is just that its weight is not perfectly centered (front to back) over its mounting flange. This would get really bad with an external balance flexplate that has that huge weight on one side of the plate, and an internal balance might actually not flex/wobble much at all. ???
Meh, you may be correct. I was just thinking out loud.
GT
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So who has a flywheel laying around they want to sell?
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For what??
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For what??
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