josephsc

For what it's worth, this is from a book: Cotton, M., "Porsche 924, 944 & 968", pg 58 -- but not sure of the original source:

Trucho-951

I believe John Milledge Engineering has built motors with b/s delete. However, I think the rotating assembly has been balanced for that type of use.

Here's a pic.

No B/S Engine

pun intented...

Stan944

I kept the balance shaft off for a few minutes once (while troubleshooting a problem). It worked, but there were noticable vibrations around 2.5 - 2.7 krpm. For daily driving it certainly would be annoying. For racing it could be OK, but I don't know if the engine would fail prematurely?

David Floyd

A true balance shaft delete removes the shafts not just the belt, if done right the car is very smooth.

luckett

When removing the balance shafts do you just plug the oil holes or does something else need to be done?

Calmchaos

I ran without a belt for a while, because my BS belt got shredded. My thrust washers snapped and the belt just got sliced up inside that cover... lucky as hell it didnt jam the Tbelt.
Anyway...
I ran w/o it for a few days maybe it added 2hp but I would never notice that. But when I put the belt back on (after replacing the bad tensioner) it became SO much smoother.
It was weird because I didn't notice the difference when I didnt have it, but I noticed when I put it back on. And like rock... I also had a tensioner bolt fall out of my PS pump.

Campeck

cough no belt covers COUGH!!!

924RACR

Use Loctite or you'll lose your nuts.

Though I don't race a 2.5L car, I'd feel comfortable removing the shafts and belt on a race-prepped motor, since I'd balance the whole rotating assembly before I worried about removing the shafts. That said, I'd also likely run in a class (ITS) where it would probably be illegal...

sweanders

The only bad thing I have seen regarding to this matter is that the oil pickup cracked and fell off..

ApexCars

Don Istook will do a BS deletes. According to him, if done right, you won't be able to tell a difference in the vibration. There is more to it than removing the belts though. Balance shafts are put in by manufacturers because it is cheaper and quicker than balancing every engine.

Team SSR

I've seen the oil pump pickup crack and very nearly fall off a race motor with B/S. The "Balance shafts" do not affect the internal balance of the engine. Pistons, rings, wristpins, rods, etc.. do, but since it is a flat crankshaft they counteract each other. The biggest effect on balance is the flywheel and clutch assembly. Most shops will balance the crankshaft by itself and then spin it again with the flywheel, or possibly 0 balance the flywheel by itself. Whether you run the balance shafts or not, the engine generates the same "out of balance" forces...the balance shafts create a secondary force to counteract the primary forces.
I'm not sure about PCA, but SCCA IT classes don't allow for removal of the balance shafts which may be why no racers are chiming in on why they do/don't run them.
Also, when removing accessories to gain HP... remember, you can't gain more HP than they cost. You can calculate the HP required to generate the amps your alternator is putting out. Which means if it only takes 3hp to spin your alternator under full load, you can't gain 5hp by removing it. The same for balanceshafts, water pumps, etc.

Ken D

Some good advice here. You should also talk to Scott Gomes; see this thread.
Balance Shaft Delete thread

M758

Perfectly said!

Do NOT delete the shafts!

Things that see extra vibes from deleted shafts.

1) Oil pickup tube - if it breaks you have spun the #2 bearing = Bad news
2) fuel rails - crack where the fuel damper and regulator are = fuel leak and possible fire

These are two for SURE... there are also all kinds of other brakets that crack.

BTW.. this NOT LEGAL for 944 cup.

All 3 avaible prep level PCA, SCCA ITS, and 944 spec requried the shafts so just keep them on.

The only way I would delete the shafts is if I knife edged the crank. I that case the actuall counter balance weight would be not correct given the slightly light engine mass. Remember these things work by creating a counter balanceing vibration to cancel out the effect of the secondary harmonics in the engine. That is why most folks don't really "feel them" very much but there are there in a very indirect way. The 4 cylinder engine is natrually unbalacned and with small internals (ie 1.6, 1.8, 2.0L) engines these secondard harmnics are small. In the larger engines like our 2.5L unit the extra mass of pistons and crank beging to cause extra vibes. So while it would be nice to pul the shafts expect to see things breaking since there will be more vib energy in certain frequencies than before. When designed and developed Porsche test with the shafts and all the bracketry was designed given those conditions. Once you change the vib signatiure of the engine otherwise solid parts can being failing at alarming rates.

Not worth the 1-2 hp you get to risk all kinds of stuff breaking thus not allowing you run events.

Serge944

Remember Tony Garcia's insane 951 2.8? It had balance shaft delete and it wasn't that smooth. That car had some serious money/knowledge put into it, too. I've seen it in person.

It's illogical for someone trying to gain some "vanity hp." Especially on a 944.

evil 944t

I can speak from experience. I know someone who cut the belt while on an engine dyno and gained 7hp.

Keep in mind that it is a race only motor and is taking a part and inspected, often.

The motor has a lot of time and money invested and makes a lot of hp.