deleting counter balance shafts.
12-04-2001, 11:20 PM
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deleting counter balance shafts.
I'm just finishing assembling the motor on my 951 race car. I've been researching the idea of removing the counter balance shafts. The car is not at constant rpm for any prolonged periods, and eliminating the shafts seems like a potential small gain in hp, decrease in mechanical parts and potential failures. I believe the only oil gallery I need to preserve is the the oil line to the turbo. If anyone has any experience or ideas/suggestions I would appreciate hearing from you.
Thanks
Thanks
02-20-2002, 09:34 AM
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Ok guys heres the deal. I have REMOVED my balance shafts, i love it the car seems lighter, revvier, maybe not as silky smooth but certianly not rough either. The only way to do this is to have alot of work done to the block.
1.removing the shafts, covers, pulleys, tensoiner,ect.
2.Weld the oil drainbacks in the block shut these are six to eight 1x1/2 inch holes running from the shaft housings to the oil pan. To do this i believe you must completely dissaseble the engine and clean the hell out of it(if you have ever welded aluminum you know what i'm talking about)
3.Next I drilled and tapped the lower oil feed. It helps to make a flat with an end mill. Then i plugged it. This is important because that feed galley runs right from a crank main i think #2
4. Finally mill a 1 1/2 inch flat on the upper feed bearing surface then drill and tap for AN fitting. Then make a nice briaded steel line straight from oil feed to turbo ( which also needs to tapped, the hole is the correct size for an 1/8 inch pipe tap. i stuffed a rag into the hole first an used tapping wax so metal wouldnt fall into my turbo.) Now just get a pipe to AN adapter and you have a direct feed to the turbo.
I know this sounds involved. IT IS
Soime of you might say to just take of the belt and leave them in. I think this is a bad idea it will make the engine rough as hell. Because the harmonis will turn them but out of order. Just ask a mitsubishi 4G63 owner (Which these shafts are designed after, yes porsche bought the design from mitsubishi) So the only way is to remove them.
But heres what you get: Quicker rpm ,less lag, 30hp I have not dynoed, but this is what others have told me. It feels right. Better oil pressure to main bearings and turbo. No seals to leak, NO balance belt to break. Easy timing belt and water pump service, longer crank bearing life. (heres why! A balance shaft works by countering vibration from the large pistons, crank. Well the block has to absorb this. so every time the shafts and crank are fighting for the block it stresses the bearings. Not the scientific description but you get it. this doesnt seem to be a huge problem for Porsche, because they are built so well. But some chryslers will eat bearings until you remove the shafts. Its funny mitsubishi actually makes a balance shaft deletion kit, you can get it from the dealer. So it is a problem.
So let me just say that if i have a porsche that the engine needs to come out of then I will always remove the balance shafts. I feel it is an improvement. And i challenge someone to tell the difference at idle, i have non turbo cams and my car idles ok.
Good luck
arthur
1.removing the shafts, covers, pulleys, tensoiner,ect.
2.Weld the oil drainbacks in the block shut these are six to eight 1x1/2 inch holes running from the shaft housings to the oil pan. To do this i believe you must completely dissaseble the engine and clean the hell out of it(if you have ever welded aluminum you know what i'm talking about)
3.Next I drilled and tapped the lower oil feed. It helps to make a flat with an end mill. Then i plugged it. This is important because that feed galley runs right from a crank main i think #2
4. Finally mill a 1 1/2 inch flat on the upper feed bearing surface then drill and tap for AN fitting. Then make a nice briaded steel line straight from oil feed to turbo ( which also needs to tapped, the hole is the correct size for an 1/8 inch pipe tap. i stuffed a rag into the hole first an used tapping wax so metal wouldnt fall into my turbo.) Now just get a pipe to AN adapter and you have a direct feed to the turbo.
I know this sounds involved. IT IS
Soime of you might say to just take of the belt and leave them in. I think this is a bad idea it will make the engine rough as hell. Because the harmonis will turn them but out of order. Just ask a mitsubishi 4G63 owner (Which these shafts are designed after, yes porsche bought the design from mitsubishi) So the only way is to remove them.
But heres what you get: Quicker rpm ,less lag, 30hp I have not dynoed, but this is what others have told me. It feels right. Better oil pressure to main bearings and turbo. No seals to leak, NO balance belt to break. Easy timing belt and water pump service, longer crank bearing life. (heres why! A balance shaft works by countering vibration from the large pistons, crank. Well the block has to absorb this. so every time the shafts and crank are fighting for the block it stresses the bearings. Not the scientific description but you get it. this doesnt seem to be a huge problem for Porsche, because they are built so well. But some chryslers will eat bearings until you remove the shafts. Its funny mitsubishi actually makes a balance shaft deletion kit, you can get it from the dealer. So it is a problem.
So let me just say that if i have a porsche that the engine needs to come out of then I will always remove the balance shafts. I feel it is an improvement. And i challenge someone to tell the difference at idle, i have non turbo cams and my car idles ok.
Good luck
arthur
02-21-2002, 05:08 AM
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Arthur
Thanks for the detailed post on the delete question. My motor is stillout of the car, so I am still considering removing the CB shafts. Your post laid it out very well. It may be interesting to dyno my car with the shafts and then repeat the dyno with the shafts deleted.
Thanks again
Daryl <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
Thanks for the detailed post on the delete question. My motor is stillout of the car, so I am still considering removing the CB shafts. Your post laid it out very well. It may be interesting to dyno my car with the shafts and then repeat the dyno with the shafts deleted.
Thanks again
Daryl <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />
02-21-2002, 11:42 AM
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David at RAETECH says do not take the Balance shafts out because:
1. the vibration will eventually break the oil pickup off ... than you have real problems.
2. most of the electronic sensors will shake loose or off.
The car was not designed for this type of vibration. He suggests drysump system and engine management system to be able to tolerate the vibration.
I had mine removed but have not driven it yet...looking forward to that.
Still makes sense to me to take them out for a dedicated track car.
944turbo
1. the vibration will eventually break the oil pickup off ... than you have real problems.
2. most of the electronic sensors will shake loose or off.
The car was not designed for this type of vibration. He suggests drysump system and engine management system to be able to tolerate the vibration.
I had mine removed but have not driven it yet...looking forward to that.
Still makes sense to me to take them out for a dedicated track car.
944turbo
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02-21-2002, 10:41 PM
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Hello again,
Ive driven the car about 10 thousand miles or so with shafts out. I guess its an individual thing. A small vibration to me might be big to someone else. I am pretty tolerant i would drive a stiff suspension solid bushing full roll caged car everyday. as long as it made good power and handled well. With that said my car hasnt had any vibration problems, i did loctite the pick-up. There is a slight buzz at about 3000 rpm, but this is a turbo S and they are pretty stiff anyway. Also io have heard of some people making block off covers instead of welding the block, they would need to be sealed well. But you still have to drill and tap the holes so i cant see how you could do it in the car without getting chips in the oil lines.
good luck everyone
arthur
Ive driven the car about 10 thousand miles or so with shafts out. I guess its an individual thing. A small vibration to me might be big to someone else. I am pretty tolerant i would drive a stiff suspension solid bushing full roll caged car everyday. as long as it made good power and handled well. With that said my car hasnt had any vibration problems, i did loctite the pick-up. There is a slight buzz at about 3000 rpm, but this is a turbo S and they are pretty stiff anyway. Also io have heard of some people making block off covers instead of welding the block, they would need to be sealed well. But you still have to drill and tap the holes so i cant see how you could do it in the car without getting chips in the oil lines.
good luck everyone
arthur