924Board.org

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

I haven't been around much lately. I used to spend a lot more time on this forum when I was traveling a lot but, I'm not doing that anymore.

Anyway, while building my 951 engine, I had started hanging around some of other forums because I was hoping to introduce myself and have meaningful dialog with the guys. But instead my first post was to a thread where I got trolled like you wouldn't believe! While I realize that I might not always sound like a nice guy, I'm very easy going and always eager to help...

Please, forgive me for this post, but I really I need to vent! I would also like to have a 'grown' discussion about some of this stuff.

Now, if I'm not mistaken there are a few engineers here, and I would love to pick your brains! I also invite all of you to join in, but please remember to act like an adult. This topic is very political, but I'm after facts. Again, I'm not an expert, but it gets under my skin when people post BS on the internet. I was scolded for this ironically. But why should I have to write a novel long post when these guys could just use google to verify what I wrote before trying to correct me... sigh.

Anyway, I am not saying that everything I said was correct; but it was to the best of my ability at the time... and later when I saw that it was futile reasoning with them I just started having a bit of a laugh, but since that was never my intention, I apologized. You have to understand that they were just attacking me and not adding anything of real value to the conversation. That sort of stuff just makes my brain bleed!

Below, I'm hoping we can straighten out some of this non-sense so it doesn't spread any further. I was exceptionally polite considering I was being beat up by guys that didn't have the first clue what I was talking about! I am a grown man, and I have better things to do than argue with children that want to call me a 'poopy-head'. So I told them that I was indeed wrong, and got out of there.

Please remember that:
"Ad hominem attacks are ultimately self-defeating. They are equivalent to admitting that you have lost the argument."

By all means, if you want to learn more about this stuff, go buy a book! I do not want you to take my word for it, I want you to help me have a better understanding by pointing out my mistakes. But this wasn't what was happening over there. I mean, I am more than willing to accept that I have a flawed understanding of things, but the things they said just didn't make any sense and I can't find anything, anywhere that backs up their claims. Sad really, but in the end, it was I that looked like the clown. Well, at least I never resorted to personal attacks, and I tried to handle my defeat with class.

Hopefully, we can create a thread here that actually helps someone. I will be citing references to the things I say, by using direct quotes from online books and articles, among other things. So please follow the links to learn more because I am by no means claiming to be an expert!

Thanks!
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

I was going to phrase the items as questions. But since I feel this is all very straight forward and I have given you links at the bottom, I'll give you my interpretation and let you correct me.

Anyway, a guy on that forum had ask what happens when you remove the balance shaft belt, and I gave a rather, 'textbook' answer.

They apparently didn't like this and started attacking me. I then tried to explain but they had no interest in understanding. I suppose I had it coming, but I had no idea that people didn't know this stuff, I mean, it in books afterall.

I will admit I was caught off guard because I hadn't really given much thought into this stuff, because there really isn't much to think about, but apparently there is... and I was given some of the strangest reasoning for why Porsche but the vibration dampers on the car.

fiat22turbo · Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR

So was it 944online.com or Pelican Parts? I would skew towards the latter being more prone to nonsensical wall-wailing and general trolling.

Pelican and Rennlist tend to be a bit better, but there are certain subjects that can be a little "hot-buttony" like oil brand or tire brands or drifting, etc.

Don't sweat it, ignore it and move on.

I don't have much of anything else to add to the discussion since I've only owned by 951 for a few months now and I'm not interested in modifying it too much for the time being.

I do have a basic understanding on how balance shafts work and why people looking for every last bit of horsepower and weight loss might remove them, but ultimately I don't believe you're going to notice a difference on the street or in local racing, unless you just prefer to remove them at a personal level (like the people that choose a Harley-style bike over a smoother idling bike of similar size, sometimes the vibrations are preferred) because you prefer more noise and vibration in your cars.
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11732 Location: PacNW

Balance shaft delete swaps broken oil pickup tubes and a bucket of fasteners for 5 hp. Bad move all around, IMO.
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Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

peterld · Posted: Mon Oct 28, 2013 12:51 am Post subject:

Common mechanical engineering wisdom stipulates that 500cc per cylinder is around the max a performance motor should have before harmonics/vibrations defeat the power gained by increasing capacity.
Thus a 4 cyl is optimally 2000cc, a 6 cyl is 3000cc, a V8 is 4000cc, and so on.
This was the general thinking back in the middle of the last century. Any increase in capacity within cylinder range was usually of the longer stroke/slower revving type.

Since then much has changed in metallurgy, machining, fuel delivery and engine management. One only has to look at the wonderful range of all alloy Ls engines now produced by GM - up to 7 litres of stonking V8.
Conversely, current F1 motors are 2.4 litre V8s revving to 16k!

The 2.5 litre 924S/944 motor, and it's bigger brother the 3.0 litre, don't have to have balance shafts, but the inclusion of balance shafts does exactly what it says on the tin - helps smooth out the motor.

Here in Australia for over 10 years now there has been a race series for 2.5 NA 944s...all running WITHOUT balance shafts. Yes there were vibration/harmonic problems at first, but these days the motors do a whole season of racing before a freshen up. Mind you, the cars are gutted with all hang-on panels in FRP, lightened flywheels, etc, etc.

It's interesting to note that the four 968 Turbo RS built by the factory comprised the 3.0 litre bottom end (with balance shafts) topped by the 8 valve 944 Turbo head, etc.

As to the 944 GTR the factory built (basically a 944S turbocharged) I have no idea.....were balance shafts used on that DOHC motor?

So long story short.....as Rasta said......unless it's an out and out dedicated race car, there is little to be gained by deleting the balance shafts except a world of pain.

I'm sure if Porsche had designed a new 4 cyl motor from scratch, rather than using the expediency of virtually cutting a 928 motor in half, the 944 motor would have looked somewhat different....maybe something like a Honda S2000 +++, or maybe even a watercooled 4 cyl Polo motor.

Notwithstanding any of the foregoing, I have never driven a balance shaft-less 944, so I really have no idea what the motor feels like, however even in my 944S2 I find the motor relatively coarse compared to modern motors (not as coarse as my 924s though

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80/81 932/8 ROW

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Fiat, it does indeed seem that this topic is very sensitive, and perhaps I was naive to think that people actually wanted to know this stuff. I won't mention the name of the forum, but it is one you listed.

Peter, I was perhaps being too faceitous in the above post.

The balance shafts merely help reduce the amount of vibration that is felt on the chassis side of the engine mounts. They have ZERO effect on the crank itself, or the power output of the engine... unless you consider the parasitic loss!

What is happening in simplified terms is, the reciprocating mass; which is the pistons and connecting rods, are pulling up on the crank which behaves like a spring. The heavier the reciprocating mass and the faster the engine speed, the more it vibrates. The balance shafts merely help mask this vibration from the chassis.

All inline-four cylinders over 1.8 liters need balance shafts according to Noise, Vibration, and Harshness standards; (please google NVH and its relation to balance shafts). These standards have nothing to do with keeping the engine from falling apart, or re-claiming power, they're for reducing certain vibrations/noise that could potientally make some people car sick.

Before balance shafts were practical, cars like the Porsche 924 with it's 2.0 L engine and the Pontiac Tempest 3.2 L, were among millions of others that had to rely on soft rubber mounts to do the same job... this is all in the links I posted above!
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Guys, keep in mind, I was talking to THE SOURCE of much of these 'broken pickup tube' claims, and they thought the balance shafts were there to stop the pistons from shaking the engine... when in fact, it is the crank that vibrates, while the engine absorbs much of this vibration. I mean, this is very well understood by engineers that wrote these books.

Now, if they don't know how the balance shafts work, or why they are there, how am I supposed to take their word that they're what was responsible for breaking those engines... I mean, how about actually being helpful and offering up some proof instead of wasting everyone's time by calling me names!

Later on, when a guy showed up and said that his engine had lasted 10 years without the shafts, they were nearly lost for words, and never really answered his questions. They told him that he must drive like a girl... yeah, what a delight! If they had proven their point, I might have put my belt back on... oh I didn't mention that did I?

Yes, my N/A engine was completely stock and I drove it for nearly eight years without them. The reason I removed my belt was because I was working on a 944 that had thrown its BS belt, and it ended up taking the timing belt. Having worked with many race shops, I had knew their actual purpose and wasn't the least bit concerned. Afterwards, I drove my car daily for five of those eight years. Even took it to the track on weekends, auto-crossed it, and went to the drag strip constantly! When I opened it to sell the parts last year, it was still absolutely perfect inside and out... in fact it was one of the nicest engines I'd ever seen... so, when exactly was everything supposed to loosen up and break???

Please, if I bothered listening to those guys on other forums, I wouldn't have a turbo engine in my car! It just seems to me, that everything is impossible to them just because they are either too lazy or don't know how. I didn't bring the fact I run without balance shafts, because I didn't think it was relevant... after all, that is just one mans experience and is by no means scientific data.

Again, I'm not suggesting that its a good idea to remove the shafts ...I'm just giving you my honest assessment. It is my feeling that some people on these forums just like to stir up paranoia... so, excuse me if I call them out! I might have been new to that forum, but I didn't just fall off the turnip truck. /rant.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

I was digging through my hard drive and came across this screen cap. Its from an advanced physics book and it discusses the 944 and how the balance shafts reduce motion sickness. So, not only do engineers understand this stuff, but other scientists study it too! Imagine that!

Please excuse the fact that it's highlighted... I didn't need that other stuff at the time.

I was being insulted over there by people who obviously had no idea what I was talking about, but yet they told me that I should "stay away from physics"... ok, I'll get right on that.

I suppose the scientists that wrote these books should also probably stay away from physics too... since it is so well known that the balance shafts are there to keep the engine from getting motion sickness!

On a serious note, please over look my passive aggressive posts, I'm just venting. I genuinely hope that someone finds this information useful. Also, please note that it says "unadapted". I personally think my balance shaft delete car is just fine, but it might bother others... also, a car with balance shafts can still cause certain people to get motion sickness because it is completely subjective...
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

So, I've began to see a behavioral pattern on that forum. I'm not usually one to get bothered by things said to me over the internet, but I was completely gaslighted. So, it wasn't that I got my feelings hurt, it was that after just pages and pages of being brow beaten, I started to question my own sanity.

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Okay, moving on...

Mechanical vibrations are a normal part of engine operation.

GeorgeV · Posted: Sun Dec 22, 2013 3:04 pm Post subject:

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Yep, if that kid came to this forum I would have told him to buy the best car he could afford, even if it's a $500 beater, and we'd help him get it sorted. If he happened to live nearby I would offer to lend him a hand. When I was his age I had three sports cars and had no idea what I was doing... but diving in is how you learn, and I'm still learning! I'm often amazed at how difficult and expensive they make these cars seem. Perhaps it is their own inability that they are projecting on to others.

Also, there was another thread that was sparked from that one. It also ran for 20+ pages. In it, he mentioned that he might not get a 944, at which-point some members became hostile; which is a typical response from control-freaks when they are disobeyed...

You see, I was lashed out at because I was disobeying. It was repeated to me time and time again that I should be asking them questions. Even though the things they were saying showed that they clearly had no understanding of how engines work. Also, everything I was saying was directly from some of the books that I've studied... so I was laughing at them, but they eventually broke me. So, I'm not kidding when I tell you that its a scary feeling when you can't trust your own memory... it was like being brainwashed by a cult or something.

So, yeah I didn't mean to make this thread emotional in any way. I just wanted to share this information on mechanical vibrations with others and was even hoping to learn something new along the way. And yes, fiat is right, you've just got to ignore it and move on! I have, but I've also learned a valuable lesson... some people only want to control you.
_________________
'84 944 -White, Brown interior
'84 944 -Red, Automatic
'86 944 -Garnet, Fully loaded, Koni suspension
'87 924S -Red, 300hp 951 swap
'87 924S -Red, Project Car
'88 924S -Red, Daily Driver

edredas · Joined: 09 Dec 2004 Posts: 861 Location: Charlotte, NC

Anyway, I would still like to continue sharing information on mechanical vibrations. This stuff can actually be very handy, and can help you find the source of vibration problems in your car. It also seems that the 944 community has been terribly misinformed by people that don't actually know how something works. I would have never guessed that I would have gotten so worked up over something said to me on the internet, but the way they ganged up on me made me question myself... I was just trying to polity help them have a better understanding, but they only wanted to bash me because they couldn't possibly ever be wrong.

So, following up on my previous posts...

As you might know, one of the biggest complaints of the 924 was the noise and vibration that invaded the passenger compartment. So, they tried to make the 944 as smooth and quiet as possible. However, that is a very hard job since there is a rigid shaft with an engine and transmission on each end that stretches from one end of the car to the other. Any vibration in one of those components can vibrate the whole assembly, so this means the entire drive-train must be completely isolated from the rest of the car.

As I mentioned above, balance shafts dampen one particular directional vibration that occurs at certain rpms. Unlike all the other vibrations the engine is emitting, this vibration just happens to transfer easily to the passenger compartment and it make it's way into places the occupants touch, such as the steering wheel, shifter, footwells, etc. This can cause fatigue, discomfort, and in some cases, motion sickness. This vibration is also the source of some of the booming noises in the cabin.

However, this is a normal engine vibration, and while it is annoying to people, it does not harm the engine in any way... the people that have started the rumors that it can break an engine, have obviously never seen/worked on a Ferrari V8.