So far R3VLimited has discussed this several times.
I searched through the forum and found all the threads and so here we are going to consolidate them all into one thread.
First off...
What is VANOS?
VANOS (Variable Onckenwellen Steuerung) is a cam phasing system for BMWs. It's similar to the Honda VTEC system for BMWs, which advances or retards the timing of your engine at different RPM speeds to optimize the engine. (VTEC goes farther then this and none in stock engines have ever broken)
What does THAT mean? Basically VANOS can mean a 40-50 ft/lbs of torque in the low end (2000-2500 RPM in a 540i). Above 4100 RPM, Dyno charts agree that VANOS ends up doing nothing; it actually just shuts off.
Now that we know what VANOS is, lets discuss...
The Pros and Cons of VANOS!
1.
As previously discussed, VANOS provides more low end power. Most people agree that this low end torque is noticeable most when daily driving. If you plan on driving this car predominately on the track or plan on driving your car above that 4100 RPM threshold, then you will not notice this as much.
2.
Currently the record for the fastest stock BMW 325 was a manual 1993 325is with VANOS (June, 1993 issue of Car and Driver). That car did 6.5 sec from 0-60mph.
As well, the fastest stock automatic BMW 325 was an automatic 1994 325i with VANOS (August, 1994 issue of Car and Driver). That car did 7.7 sec from 0-60mph.
That says a lot for the E36, as well as for M50B25TUs in general. Powerful engines, even more so with the addition of VANOS.
3.
There are more performance options for a VANOS engine, but keep in mind, like an our stock M20s, these engines come highly tuned from the factory. There is not a huge amount of things you can do to an M50 (VANOS or non) that will net any huge gains. The two things that are recommended are S50 cams (E36 M3) and a chip, which will bump you up to about 220 hp.
Don't waste your money on injectors or MAFs, even cold air intakes (CAI) net VERY small gains. The only real thing you can do is turbo, and we're not going into that here.
4.
The drawback to a M50TU is that the Vanos is no VTEC. They do break, and when they do, it can be $500-$1000 to fix. Even while they do work, after about 150,000 km they start to rattle, which is also tough to fix.
The issue is an o-ring within the Vanos unit, specifically a piston seal, which go after about 30,000 km, eventually leading to failure. Unfortunately BMW does not sell these individually, they only sell rebuild Vanos units for about $500. These rebuilt ones still have the same rings that degrade in the engine environment and fail.
EDIT: Apparently bimmerforums has someone there who runs Beisan Systems. They manufacture a teflon o-ring ($30) for failing Vanos units, addressing the reason for failure (bad material), as well as a repair kit (also $30) for that annoying "Vanos Rattle". They even sell the expensive Vanos tool for $5.
So let's discuss the...
Pros and Cons of hunting a Non-Vanos
1.
The M50 had thicker vale stems and dual valve springs. Some have said the block is SLIGHTLY thicker as well, allowing one to bore out to 86mm vs. only 85mm in a M50TU. (It's been brought up that the S50 block is a M50TU block bored to 86mm, so this may be a moot point)
However it has been argued that the second valve spring is only there since the valve stem is thicker, and the valve stem is thicker because it was on the M20.
Either way, this engine's stock internals lends themselves better to boosting. Again, not talking about that here, but E30Tech.com has more information on this.
2.
The M50 can be cammed by moving the exhaust cam to the intake side and adding a Schrick cam to the exhaust. However, Schrick cams have been discontinued. If you can find one used, power to you.
VAC Motorsports now offers some M50 cams on their website, made by CAT.
M50 Non-Vanos CAT Cams @ VAC Motorsports
Other then that, the same applies for this engine in terms of performance mods. Chip it and be done. Maybe a CAI, save your money for suspension and drivetrain stuff.
3.
The major drawback to an M50 non-vanos is that the cars they come from are older, therefore more kms. They also were made for only late-1991 until late-1992, so finding one is a little harder. Parts are mostly interchangeable, so fixing one is no more difficult.
4. Big bonus? Less things to go wrong. A Vanos unit failing is not common, but it does, like everything else, not have an infinite lifespan. However, if you're mechanically inclined, fixing it yourself MAY not be that difficult, considering the parts are cheap through Beisan Systems.
CONCLUSION:
This debate will be concluded when two brand new, completely stock 325i cars get dyno'd. Until then, we will argue.
One thing is certain, the M50 is a moderate upgrade from the M20. About 30 more hp/torque, a timing chain rather then a belt...
If you've got anything to add, do it NOW!
Some threads:
http://www.r3vlimited.com/board/showthread.php?t=55290
I searched through the forum and found all the threads and so here we are going to consolidate them all into one thread.
First off...
What is VANOS?
VANOS (Variable Onckenwellen Steuerung) is a cam phasing system for BMWs. It's similar to the Honda VTEC system for BMWs, which advances or retards the timing of your engine at different RPM speeds to optimize the engine. (VTEC goes farther then this and none in stock engines have ever broken)
What does THAT mean? Basically VANOS can mean a 40-50 ft/lbs of torque in the low end (2000-2500 RPM in a 540i). Above 4100 RPM, Dyno charts agree that VANOS ends up doing nothing; it actually just shuts off.
Now that we know what VANOS is, lets discuss...
The Pros and Cons of VANOS!
1.
As previously discussed, VANOS provides more low end power. Most people agree that this low end torque is noticeable most when daily driving. If you plan on driving this car predominately on the track or plan on driving your car above that 4100 RPM threshold, then you will not notice this as much.
2.
Currently the record for the fastest stock BMW 325 was a manual 1993 325is with VANOS (June, 1993 issue of Car and Driver). That car did 6.5 sec from 0-60mph.
As well, the fastest stock automatic BMW 325 was an automatic 1994 325i with VANOS (August, 1994 issue of Car and Driver). That car did 7.7 sec from 0-60mph.
That says a lot for the E36, as well as for M50B25TUs in general. Powerful engines, even more so with the addition of VANOS.
3.
There are more performance options for a VANOS engine, but keep in mind, like an our stock M20s, these engines come highly tuned from the factory. There is not a huge amount of things you can do to an M50 (VANOS or non) that will net any huge gains. The two things that are recommended are S50 cams (E36 M3) and a chip, which will bump you up to about 220 hp.
Don't waste your money on injectors or MAFs, even cold air intakes (CAI) net VERY small gains. The only real thing you can do is turbo, and we're not going into that here.
4.
The drawback to a M50TU is that the Vanos is no VTEC. They do break, and when they do, it can be $500-$1000 to fix. Even while they do work, after about 150,000 km they start to rattle, which is also tough to fix.
The issue is an o-ring within the Vanos unit, specifically a piston seal, which go after about 30,000 km, eventually leading to failure. Unfortunately BMW does not sell these individually, they only sell rebuild Vanos units for about $500. These rebuilt ones still have the same rings that degrade in the engine environment and fail.
EDIT: Apparently bimmerforums has someone there who runs Beisan Systems. They manufacture a teflon o-ring ($30) for failing Vanos units, addressing the reason for failure (bad material), as well as a repair kit (also $30) for that annoying "Vanos Rattle". They even sell the expensive Vanos tool for $5.
So let's discuss the...
Pros and Cons of hunting a Non-Vanos
1.
The M50 had thicker vale stems and dual valve springs. Some have said the block is SLIGHTLY thicker as well, allowing one to bore out to 86mm vs. only 85mm in a M50TU. (It's been brought up that the S50 block is a M50TU block bored to 86mm, so this may be a moot point)
However it has been argued that the second valve spring is only there since the valve stem is thicker, and the valve stem is thicker because it was on the M20.
Either way, this engine's stock internals lends themselves better to boosting. Again, not talking about that here, but E30Tech.com has more information on this.
2.
The M50 can be cammed by moving the exhaust cam to the intake side and adding a Schrick cam to the exhaust. However, Schrick cams have been discontinued. If you can find one used, power to you.
VAC Motorsports now offers some M50 cams on their website, made by CAT.
M50 Non-Vanos CAT Cams @ VAC Motorsports
Other then that, the same applies for this engine in terms of performance mods. Chip it and be done. Maybe a CAI, save your money for suspension and drivetrain stuff.
3.
The major drawback to an M50 non-vanos is that the cars they come from are older, therefore more kms. They also were made for only late-1991 until late-1992, so finding one is a little harder. Parts are mostly interchangeable, so fixing one is no more difficult.
4. Big bonus? Less things to go wrong. A Vanos unit failing is not common, but it does, like everything else, not have an infinite lifespan. However, if you're mechanically inclined, fixing it yourself MAY not be that difficult, considering the parts are cheap through Beisan Systems.
CONCLUSION:
This debate will be concluded when two brand new, completely stock 325i cars get dyno'd. Until then, we will argue.
One thing is certain, the M50 is a moderate upgrade from the M20. About 30 more hp/torque, a timing chain rather then a belt...
If you've got anything to add, do it NOW!
Some threads:
http://www.r3vlimited.com/board/showthread.php?t=55290
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