[MC968CS]

Thanks cloud 96...8 yep, thats the kit.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

So have you decided against the balance shaft delete for your race car? If so, why? Thanks.

Partial Post: Please Login or Register to read the full post.

[flash]

having driven with the balance shafts disconnected due to a broken belt, i can tell you for certain that the engine produces LESS power. this is as a result of things essentially having to "fight themselves" as the rotating masses result in harmonics that require more energy to overcome the loads. it feels like it is struggling.



if you lightened other things up, so as to potentially change the harmonics, you might have it work. there would be a boatload of math involved though in order to get it right, and not just be guessing.



this may or may not be so much of a problem in the 944, for which this kit was developed, but in the 968, those balance shafts really do the job.



as a side note, did anybody else notice that there is no mention of any power gain?

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

Yeah, a 3.0 liter inline four without balance shafts has the makings of being a real shaker for sure. BMW even uses balance shafts on their new turbo four, which I believe is only 2.3 liters. I was just curious as to MC968CS's experience.

Partial Post: Please Login or Register to read the full post.

[flash]

lol - yeah - it was pretty ugly. it was not a fun drove from l.a. to paso robles and back like that

Partial Post: Please Login or Register to read the full post.

[MC968CS]

Flash, I deeply deeply respect your experience. In this case mine differs drastically.



Running sans balance shaft belt and tracking with revs above approx 4000rpm, the engine definately is stronger, with not hint of doubt in my mind. I have very seriously tracked the car both ways. My engine internals are stock, with just the airbox mod, very special full race exhaust and the best of 5 or 6 chips made for me. All tested back to back on the dyno too. I also picked up approx 3km/h (GPS data) down the straight at my test track.



In fact once I noticed a really surprising hp pickup in a race, and was talking to my race crew as to what caused it afterwards, when the officials came in to tell me a belt, which turned out to be the balance shaft belt, was lying on the track. I didnt know. So, for me, running sans the balance shaft belt results in a faster engine, but it is rougher at lower revs and I also dont trust it to be ok longer term. I worry about other things breaking from the extra vibration. Not worth it to me as its not a hp focussed car.I even carry spare balance shaft belts with me to all events. (ie: the cars are very fast relative to their hp, so if you are not winning, just 'turn in to corners faster' is my attitude-968's hammer)



My 5 cents worth for cloud 96...8 on a car built and run with an unlimited budget to win.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

MC968CS - Thanks for sharing your experience. So, as I had suspected, a mod best suited to people looking to eek out every last bit out of their car, preferably with an unlimited budget available.

Partial Post: Please Login or Register to read the full post.

[flash]

in my case, i had a 12lb flywheel. this is likely what made the problem show up. if you had a DMF your case would almost certainly be a complicated one, where the problem was there, but masked by the DMF. the removed mass would give you a gain, but the DMF would hide the harmonic issues. with a 12lb flywheel, there is nothing to smooth that out, and the harmonics wreak havoc.



for me, i noticed it the instant it happened. i was in the middle of a sweeping fairly high speed turn, banged a gear, and suddenly the car just felt "wrong". my wife was sitting next to me and was not happy with me freaking out. we were just getting going on the annual paso robles run with a bunch of other 968s. i pulled over to find the belt sheered longitudinally. i cut it and removed it, hoping that the vibration and power drop were due to the belt jumping 1 or more teeth. i was not that lucky. the symptoms remained. the entire run up and back was nerve wracking. i found muscles in unmentionable places that i never knew i had.



harmonics can be calculated. the effects are able to be clearly shown in the math. any harmonic will cost power. if you have the ability to dampen them, you might not feel the harmonic, but the dampener is still absorbing that energy which is not being transferred to the wheels.



a scenario that would explain your situation would be one where there was a larger problem (i.e. an unbalanced flywheel, or a balance belt off a tooth) and that problem was then "relieved" by removing the belt. the car would be "faster" than before, but still not as fast as if things were right.



another scenario that could explain your situation would be one in which you hit the "perfect storm" of engine balancing. you may have been one of the lucky ones that had everything "just right". it happens. in fact, manufacturers have actually determined a percentage of the engines that are like that.



so, in the end, you have to determine whether or not the 4 or 5 hp you might gain from the deletion of the rotating mass is offset by the cost of the harmonics. you may have a net gain, or you may have a net loss. in my case, i had a huge net loss.

Partial Post: Please Login or Register to read the full post.

[tamathumper]

Running with no belt would probably be better than running with one of the shafts out of phase by 180 degrees?

Partial Post: Please Login or Register to read the full post.

[gbarrier]

Been there. 180 out really sucks. It was installed by a local reputable shop for the previous owner.

Partial Post: Please Login or Register to read the full post.

[Lear35A]

Also been there. In one of my many rebuilds I put the bottom shaft 180° out. The shifter vibrated so much I could hardly hold it.

Partial Post: Please Login or Register to read the full post.