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Car Forum / Porsche / Porshe 944 / May 2006importance of balance shaft?
Hi guys, I'm new to the Porsche line and was wondering if someone could answer a question? I just acquired an 87 Porsche 944 non-turbo. I got it knowing that the alternator needed replacing, it would not charge the battery. While pulling the alternator I noticed what looked like some type of inspection hole on the upper left (my right) of the engine front cover. When I looked into it I noticed the top balance shat did not have a belt going around it. I pulled the front cover off the engine and realized that the balance shaft belt was missing altogether. Both balance shafts spin freely but there is no belt. My question is this... How important is the balance shaft anyway? I was able to crank the car and drive it (ran very, very well) before I got it and pulled the alternator for rebuilding. What is the purpose of the shaft and can it be driven without one for long periods. Thanks in advance. VCS >My question is this... How important is the balance shaft anyway? I was >able to crank the car and drive it (ran very, very well) before I got >it and pulled the alternator for rebuilding. What is the purpose of the >shaft and can it be driven without one for long periods. It's actually sort of cosmetic - it dampens engine vibration at lower rpms, so the car seems smoother. Guys that track 944s often remove them permanently with no ill effects. epbrown -- "Everybody wants a normal life and a cool car; most people will settle for the car." Chris Titus 2003 BMW 325i Black/Black, 2003 BMW Z4 Black/Black Well now we know - and I adjust that belt carefully so all timing marks line up within degrees! Surprise! But imagine how smooth your baby will run when you install a new belt! I replaced the brushes in my 944 without removing the alternator - it was so easy!  Signature______ joliett >>My question is this... How important is the balance shaft anyway? I was >>able to crank the car and drive it (ran very, very well) before I got [quoted text clipped - 9 lines] > most people will settle for the car." Chris Titus > 2003 BMW 325i Black/Black, 2003 BMW Z4 Black/Black Shortly after aguiring my '89, my water pump failed. When my mechanic replaced it, obviously we went with a new timing belt. When I picked up my baby though he told me that both balance shaft belts had broken and he replaced those as well. I thought that vibration was normal due to it being a four banger, but after the replacement of these belts......WOW. Replacing your belts would do the same for your car, and make that much more pleasurable to drive. That little ZZZZZZZZ to the sound is soooo awesome. Let me know how you make out. Fred > Hi guys, > [quoted text clipped - 17 lines] > > VCS Actually surprised to hear the engine would run well without the balance shafts working. Could you describe how much vibration you experienced before reconnecting the shafts? It actually felt like any American four cylinder from the 70's or 80's. Since I'd never owned a Porsche before, I didn't think much of it. Growing up working on Ford and Mopars, I learned that the more cylinders you had, the smoother the engine ran. After this repair to my '89 944, I learned that wasn't necessarily so. My mechanic (definitely an expert on the breed) assured me this caused no damage. As with all repairs to this car, the $1000 price tag on fixing it made me swear that it was going into the paper for sale. That is until I got in it and drove it home. OH HOW I LOVE MY CAR. > Actually surprised to hear the engine would run well without the > balance shafts working. > Could you describe how much vibration you experienced before > reconnecting the shafts? a warning - I would be very worried - not because there is no balance shaft belt, but because it indicates that some idiot was working on the car and didn't care to be thourough - I would personally take that as a sign to IMEDIATELY change the timing belt, and add a balance shaft belt, and check the tensioning rollers, etc. >Hi guys, > [quoted text clipped - 17 lines] > >VCS Bill www.wbnoble.com to contact me, do not reply to this message, instead correct this address and use it will iam_ b_ No ble at msn daught com Yes and no, Bill. I totally agree with the timing belt replacement. Keep in mind though that the balance shaft belts are thin and relatively delicate. Haven't seen one last as long as a timing belt yet. Just my $.02 worth. >a warning - I would be very worried - not because there is no balance > shaft belt, but because it indicates that some idiot was working on [quoted text clipped - 33 lines] > > *** Posted via a free Usenet account from http://www.teranews.com *** This four cylider bias is fascinating. I also have a Saab 900S with four cylinders that runs as smooth as a clock. No balance shafts. Maybe the 944 has some other design aspect that makes the balance shafts necessary. (or optional for that matter) > This four cylider bias is fascinating. I also have a Saab 900S with > four cylinders that runs as smooth as a clock. No balance shafts. > Maybe the 944 has some other design aspect that makes the balance > shafts necessary. (or optional for that matter) NVH can be reduced by a manufacturer in lots of ways, balancer shafts are used in several 'premium' engines although I guess having big pistons probably made it harder to cancel out in other ways with the options available in the late 70's. IIRC Porsche just wanted it to feel "as smooth as a six" following criticism over the 924 engines' harshness. Never driven a 924 but I've own quite a few 4-pots & never thought of them as being particularly harsh, I guess it depends what you are used to. A straight six would be nice, more refinement below 2k rpm would be good too, there are a lot of ways in which this engine could have been better but it was probably developed on a relatively low budget. Malc. I pulled this from a website giving many specs on our beloved cars... "In-line 4-cylidner engines were often plagued with vibrations so Porsche negotiated a deal with Mitsubishi for the use of their 2-balance shafts." It has a little more instreading reading if interested.....http://www.conceptcarz.com/vehicle/z9949/default.aspx. > This four cylider bias is fascinating. I also have a Saab 900S with > four cylinders that runs as smooth as a clock. No balance shafts. > Maybe the 944 has some other design aspect that makes the balance > shafts necessary. (or optional for that matter) > I pulled this from a website giving many specs on our beloved cars... > "In-line 4-cylidner engines were often plagued with vibrations so Porsche > negotiated a deal with Mitsubishi for the use of their 2-balance shafts." I've always wondered, wasn't the patent originally held by an American company and then Mitsubishi purchased it? For some reason, I always think of Allison or Lockheed (think P38 Lightning, ironic that it's now Mitsibushi's) > > This four cylider bias is fascinating. I also have a Saab 900S with > > four cylinders that runs as smooth as a clock. No balance shafts. > > Maybe the 944 has some other design aspect that makes the balance > > shafts necessary. (or optional for that matter) Displacement, I've heard, is the big issue. I'll bet the Saab displaced 2 liters or so. I've read that once you go much over 2 liters, the vibration gets more noticeable. I believe Honda's 2.2 doesn't use balance shafts (could be wrong) and it's very smooth... however, the 2.4 in the Chrysler "cloud" cars (Breeze, Stratus, etc) does use a balance shaft. I don't remember offhand which Japanese mfr makes those engines, but I'm thinking it was Mitsu engine. GM's 2.5 Iron Duke from the 80's was very shaky. Very ironic. Especially since Mitsubishi was the company responsible for the Japanese Zero during WWII. Coincidentally, Porsche designed Nazi war equipment. I know......this is a little off topic, but it just made me go hmmmm. >> I pulled this from a website giving many specs on our beloved cars... >> "In-line 4-cylidner engines were often plagued with vibrations so Porsche [quoted text clipped - 19 lines] > offhand which Japanese mfr makes those engines, but I'm thinking it was > Mitsu engine. GM's 2.5 Iron Duke from the 80's was very shaky. Exactly. Later 944s' displacement was increased to 2.7 and 3.0 in the "S" models. I remember when I got my baby, I thought the engine was incredibly large for a four cylinder. The car has a big nose and the engine takes up every bit of room under the hood. Looks like I've helped this string get far away from helping VCS's belt question. Sorry about that. Best of luck with your repairs VCS. Let me know how you make out. >> I pulled this from a website giving many specs on our beloved cars... >> "In-line 4-cylidner engines were often plagued with vibrations so Porsche [quoted text clipped - 19 lines] > offhand which Japanese mfr makes those engines, but I'm thinking it was > Mitsu engine. GM's 2.5 Iron Duke from the 80's was very shaky. my point was not that the balance shaft is important, but rather that the omitting of the belt indicates a lack of care and concern on the part of hte mechanic. by the way, when I drove a 944 as my regular car and put 250K miles on it (from new), I did all my own belt changes - I'd wait for the balance shaft to break, that was my sign to change them both - never had a timing belt break. so your theory is right - the reason it's right is that the timing belt turns at 1/2 engine speed and the balance shafts go at 2X engine speed, so the balance shaft belt goes 4X as far as a timing belt in the same # of miles \ >Yes and no, Bill. I totally agree with the timing belt replacement. Keep >in mind though that the balance shaft belts are thin and relatively [quoted text clipped - 6 lines] >> as a sign to IMEDIATELY change the timing belt, and add a balance >> shaft belt, and check the tensioning rollers, etc. Bill www.wbnoble.com to contact me, do not reply to this message, instead correct this address and use it will iam_ b_ No ble at msn daught com Let me add my 2 cents worth--- I replaced both the cam timing belt and balance shaft belts myself. At the time I knew there was one balance shaft but not two (OK I can't read!). The car ran fine but about 8 months later (as I thought everything was OK the oil pickup tube broke and oil pressure went to zero. I was at idle in a parking lot so there was very little if any damage-- in fact I can't see any change in the oil pressure now versus before the break. However -- if this were to occur at high speed I would expect some damage. Took the shop (and yes I had it done rather than pull the pan myself and spend ten hours on my back-per the book and maybe longer for me) 10 hours plus parts came to just short of $1200. I would at the very least replace and make sure that all is properly aligned. Learn from my stupidity. Brian Moore > my point was not that the balance shaft is important, but rather that > the omitting of the belt indicates a lack of care and concern on the [quoted text clipped - 27 lines] > > *** Posted via a free Usenet account from http://www.teranews.com *** |
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