Getting rid of balance shafts ?

[ImClueless]

I heard on most cars you can take out the balance shafts and gain some HP out of it. Is it possible on a porsche or do you think it would throw the engine to far out of balance and send it shuttling through my hood..

[Scott R]

Their is a guy in my local PCA that runs without balance shafts. He states that he gained some power. But it sure does vibrate around 4K, not very comfortable for around town.

[ImClueless]

yeah thats what i have been hearing, besides theres just something about smooth silky power..

[Moneyguy1]

Hell, just install a GM V6 and eliminate the balance shafts, the danger of broken valves, the iffy cooling system and about a hundred other strange and odd quirks the 944 engine has, thanks to superior German engineering!!!

Forgive me, guys, but doing a head job has done one on me.

Cheers

Bob S.

[ImClueless]

didnt mean to offend, just a question....

[AaronM]

From what I've heard (and it makes sense), removing the balance shafts, while slightly increasing horsepower, will seriously reduce engine life expectancy because of excessive vibration. There are a lot of things under the hood that don't like a lot of vibration and the few hp you'll pick up aren't worth the extra mechanical failures. There's a reason the factory put the balance shafts in there, and it wasn't just for ride comfort.

Aaron

EDIT: If you want the engine to spin more freely (which is what disconnecting the balance shafts would do), you're better off getting a lightened flywheel. No loss of smoothness and the same increase in the engine's ability to rev.

[Moneyguy1]

Hi Lon....

The design of the engine, not only from displacement parameters, but bore/stroke numbers requires the balance shafts to prevent it from shaking itself apart at constant mid-range revs. horizontally opposed 4 cyl engines do not have this problem, nor do five or six cylinder in-line engines. My objection to the 944 engine design is its complexity for the amount of power produced (NA). Since it was derived from a number of 928 parts, it is kludged to work, and since I was once in automotive engineering, I keep wondering whether a clean sheet design would not have been simpler, and less expensive in the long run. As an example, the balance shafts are an add-on, not required in the "parent" (or donor, if you prefer), 928 engine. I also wonder what the factory/dealer repair record over the production life of the model was, and what items were the most frequent to fail. But, that is something we can only guess at, never know for sure. The problems of the timing belt were never resolved during the 10 year run of the model, with the notable exception of the addition of a spring loaded adjuster which, according to the manuals, STILL requires the P9201 tool to adjust the tension.

My comments about the V6 installation is not completely without merit; the car would profit by an engine of the same weight, 1.3 liters additional displacement, and a vibration free design. Something the factory should have done in the first place. But, remember, the factory AT NO TIME will permit a "lesser model" ouclass the flagship 911 or derivative thereof. Although that nearly happened with the 951 in 1986.

I try to answer questions honestly; my forte is electrical and air conditioning, with some expertise in overall engine rebuilding.

There are no stupid questions. The only way we learn is by asking and then sifting the answers for the truth....

Bob S.

[afx]

I currently do not have my balance shaft belt installed correctly. I am not sure how close it is or if it as un-balanced as it would be without the belt completly. There is almost no extra vibration until you hit aroun 4K, then it gets pretty rough. I dont really see why it would be a problem to have to balance shafts for daily driving. Mine do not bother be much because I rarely get up to 4K in daily driving.

[AaronM]

Just a bit about the "lesser model" out-performing the 911. You're forgetting the 914/6. The sixes would run with the 911T in the straights and they blew by any 911 of similar vintage in the twisties. I was tempted to mention the 916 too, but that wasn't really a production model and on a price comparison the 916 was not the lesser model.

Yes the 944 engine was/is complex for its output, but given the parameters Porsche had to work with, there really wasn't much choice. The 944 engine, aside from identical bore and stroke, really isn't much related to the V8 in the 928. If I remember correctly, not even the pistons are interchangeable. (Something about the dome-ing of the pistons I think.) Also, the 944 is based on the 924, which had its engine bay built around a VW/Audi straight-four. Shoehorning a V-6 into the a chassis designed for a straight-four would have required more re-engineering of the chassis than Porsche could absorb at the time. A V-6 narrow enough to fit would have been too tall and a V-6 short enough to fit would have been too wide.

The 944/924S engine was only "half of a 928 engine" in displacement. It's not like Ford's V-8 and V-10 where the V-10 is just a V-8 with a longer block and crank. While the 944/924S engine benefitted from Porsche's experience with the 928 V-8 (for example, the use of Reynolds 390 aluminum for the block and head), it was not simply a 928 V-8 cut in half.

Aaron

[Moneyguy1]

Aaron: I have seen 944s with GM v8s installed. There was quite little that had to be changed; power brakes were lost, but that is really no big deal. And, there was, in the works, a six cylinder engine that would have fit with room to spare; the VW VR6. What difference would it have made: Audi or VW? Audi had a straight 5 that would probably have fit as well, I would have to do some measurements to verify. As for the 914, you are correct, and it makes my point. Does Porsche still produce the 914? Nope. It came too close to toppling the king. It replaced the 914 with the anemic 924, keeping the HP under 125 in the NA form. The 928 was meant to be the new flagship, but somewhere management had a change of heart. Perhaps it was the threats of lynching by the "purists." Look up part numbers 928 to 944 internal parts. There are very few interchangable. Once Porsche had made the decision to use the parts bin as much as possible, they found out that this was more difficult than they had thought, and with typical Teutonic stubbornness, refused to budge from their proscribed path and came up with a lousy design, brilliantly executed. The original 928 was 4.7 liters if I remember correctly. Half that would be less than the 2.5 of the 944. I never said it was a v8 cut in half; that is a virtual impossibility to produce. The only parts that could be internally carried over might be the connecting rods, pistons and perhaps the head. Pontiac tried a similar stunt in the sixties with their "Iron Duke" in the Tempest; rear trannie and front slant 4: imagine that...an engineering advance....a Porsche based on 40 year old technology when it was new. Now where have I read that before? Truth be known, new basic ideas are tried and like a self fulfilling prophecy are designed to lead to failure. "See, we told you so...." It is only when the company is backed into the ultimate wall such as the limit to which an air cooled engine can be increased in displacement (ahh, the good old laws of thermodynamics) does the company really embrace "new" technology such as water cooling..Ach Du Leiber....Such an idea....

Have fun...I do!!!!!!

Cheers!!

Bob S.

[AFJuvat]

Originally posted by afx
I currently do not have my balance shaft belt installed correctly. I am not sure how close it is or if it as un-balanced as it would be without the belt completly.

Engine at TDC,, keys for both balance shafts point up same orientation as the cylinders

AFJuvat

[SoCal Driver]

Here:

[AaronM]

Moneyguy: Point taken. Still, there has to be more to the use of a 4-cylinder than simple stubborn-ness. If I had to hazard a guess, it would be that prior experience (with the 914/4 and the original 924 with the Audi engine) taught Porsche that sharing obvious componants with VW/Audi was a big no-no in the eyes of the public.

If I remember rightly from Leffingwell's excellent book Porsche Legends, the original 924 was supposed to be a VW exclusive, but VW axed the project. Porsche picked up the original 924 only because the union at which the VW 924 was to be made was very upset with the loss of jobs when VW canceled. When the original 924 got the same "vopo" reputation as the 914, Porsche was left with very little choice than to re-design the exterior a bit and to change the engine to a "genuine Porsche" unit.

I agree that there are a lot of larger and vibration-free engines that can be made to fit in the 944/924S, but given the technology of the period, and the fact that Porsche was aiming for balanced handling pretty much limits the engine choices they could make. The engine had to be light, even with the small straight-4 the car is slightly nose-heavy.

This has been a great exchange by the way. I've been on more than a few other forums where this would have degenerated into a flame war. Thanks for keeping it an informative discussion.

Aaron

[Moneyguy1]

Hey...It's fun to exchange info and ideas. Yes, originally the 924 was to be a VW/Audi product, similar to the 914. What happened was that what VW "changed their minds" Porsche saw it as a way to get their balance sheet in more positive territory. My gut feeling is that Porsche had very little experience with straight inline four cylinder engines and kept getting themselves deeper in the crap as the 944 design progressed. I imagine that management gave them a timetable and, right or wrong, they came up with some compromises that, although not optimal, filled the bill. What is sad is that, realizing (we assume they knew about the engine's Achille's heel), Porsche did not, for the 1985.5 "series 2" come up with a different configuration. From a standpoint of esthetics, the car still looks as modern as tomorrow; the only objection I have to the body build is the rear hatch and its tendency to delaminate. Had I been the designer, I would have made the frame more robust, or eliminate it altogether and do what GM did with the Camaro/Firebird with the hinges bolted directly through molded holes in the glass canopy. Then, sadly, over the life of the 944 the annual price increases began to take their toll to the point where it was no longr "affordable" as an entry level vehicle, and many of the reviews pointed out the fact that it was a lot to pay for a 4 cylinder car. The weight of a VR6 is even a few pounds less than the 4 banger, and the Detroit 3.8 liter V6 is within 20 pounds according to my sources. IN addition, such an engine would have sat back a tad, reducing the front to back weight distribution differential!!

I give these only as potential configurations, not as engine sources!!!!!

It would have been a totally different car from the standpoint of potential. Granted, the turbo model can be horsed up to phenominal numbers, but at what cost in reliability? Had the company started wih 3.2 or 3.8 liters, there would have been so much more to work with. Even with the four; imagine had the turbo model head been redesigned so the intake/exhaust were on the same side. Would have simplified the plumbing, reduced the weight a bit, eliminated some weak spoys such as cracking of exhaust components. They could have done a lot had they wanted to but consider the 911 as an example. The annual changes were incremental, never radical. Flip over an early 911 and a later model and from the bottom to the casual observer, they look a lot alike (even a beetle looks similar).

This has been a great discussion. Thanks!

Bob S.....

I did work early in my career for GM in research........great fun!!!

[SoCal Driver]

Ah...Which V-6 was that? Twin turbos?

[AaronM]

This has definitely been interesting. I've got no complaints about the power that my 924S makes, the car's well balanced and after my old Accord, the 924S definitely feels more lively.

Of course, I haven't had to do a front-end service yet.

Aaron

[Mark_944S2]

Having an S2 which has as much power as a GM V6 or a 24V VW VR6 I'm not quite convinced by the complexity argument :

91 944 S2, 220bhp.

Valves = 16
Cylinders =4
Cams = 2
Camshaft belts = 1, camshaft chain = 1
Balance shafts/belts =2

Character - very torquey, revs nicely. Bit noisy!

2003 VW Jetta VR6 24V = 210bhp

Valves =24
Cylinders =6
Cams = 4
Camshaft belts = 2, chains = 2
No balance shafts (I think)

Much quieter but who wants quiet! Besides the S2 has a unique engine, that's why I like it.

Mark

PS Fuel consumption on an S2 is a lot better than a Jetta VR6

[Moneyguy1]

Unique is good; reliable and durable is better. And, from my own experience as a member of PCA, and the postings on this and other lists, the 944 engine is not one I would put in the top ten of reliability. Be honest...If we, as individuals, did not keep on top of potential problems, how long would it be before real serious, expen$ive problems would put at least a temporary end to our fun? Yes, I like the power the S model and the 951 put out, but they both inherit the base problems of the oriinal design. I own a 944, and I take good care of it. Prior to relocating from Roachester NY to Tucson nearly two years ago, I had my friendly neighborhood Porsche factory trained mechanic install new belts for me. He asked if I was going to drive it cross country. If so, he said, I better find a place en route to GET THE BELT RETENSIONED!!!!!

Tell me of any other car that requires this kind of attention? Needless to say, I had it shipped.

Not looking for arguments. Simply pointing out that the vehicle could have been improved with a bit more effort on the part of the maker, given the premium price that the car originally demanded when new.

BTW..I have a VR6 Passat. Don't worry about valve damage too much....The only problem I have with it is that technical data is difficult to obtain for the mid 90s model since there were relatively few. With similar overall mileage, the Passat has yet to have any failures in electrical switchgear. The windows still work, the A/C switch still operates, and I do not have to have an advanced engineering degree to figure out how to get the defrosters to work!!!!!!

I still wonder what will be out there for us folks to wrench on after the supply of 944s dries up due to time, accidents and other things. I used to rebuild classics. The most horrific words were "No Longer Available" when looking for parts. Every year there are fewer out there for us to glean parts from, and as the number out there dwindle, interest in providing parts that the factory will not supply will also begin to fade. The 944 is not the icon that the 356 or 911 are. Every time I read a post of a broken belt or S chain destroying a head or a #2 bearing holeing a block, I think to myself "There goes another one." Supplies are limited, guys...

Cheers!!

Bob S.

Now if I had a big barn, I would begin hoarding now ;o)

[AaronM]

Yes, supplies are limited. This is why we need to learn how to machine things.

Aaron

[drew1]

I made a reply in the last couple of years similiar to Moneyguy's about 944 faults. I think the post was converting a 924 to 944 motor. My thoughts were to stick to the Audi. I think in the 70's some people got up high in Porsche that should have been building Cadilacs instead of sports cars.

drew1