Hello,

My name is Ed and I just purchased my first Porsche a few weeks ago. It's a 2002 996 turbo.

I have been doing a LOT of reading on the forums to get familiar with the car and what to expect. One that I can't believe Porsche was ok with was the IMS noise. From what I understand it is caused by the two gears. I think I know what would fix this once and for all. It'll take one of the Vendors with $$$$ to develop this upgrade.

When I was in high school, I owned a 1990 Toyota Corolla. I had to do a head gasket replacement on it when I first got it. I put the thing back together and it ran fine minus a rattling noise coming from the valve cover. To make a long story short, it ended up being the two gears between the cams. It sounded just like this IMS noise we all have in these turbo cars. What Toyota did to prevent that noise, was one of the gears was split in two and one half was spring loaded. Before the gears are supposed to be matched up, you have to preload the one gear and hold it in place with a pin. Once you had everything set, you pull the pin out. The one gear will then hold firmly to the other. The best way I can explain it would be a scissor like effect on the gears. This stops the gears from ever getting slack.

I think that one of the performance shops should look into making something like this.



-Ed

 

The set up you speak of lets one cam "float" to stop the noise. What I mean by float is that the one cam can move from where it was set in order to keep noise down. The ims on our motors is used to time all four cams. This ability to move would knock the timing out of whack on either the excel or the decel.

 

The setup he is refering to does not have a floating cam shaft. The cam gear is split and spring loaded to automatically compensate for the gear lash that causes the noise. So with the cam gear separated in half one the gear halves utilize a clock spring to load it the direction opposite of cam load while running. This loads back side of the gear teeth the other way to stop the cam gear slop. So by this spring loading both faces(leading and trailing) of the gear teeth is making a firm contact with the opposing gear.

The IMS isn't the main mechanical component in the keeping of cam timing. Granted if the IMS gear fails timing will be screwed, but the IMS timing as pertains to the chain and sprockets are a constant. The cam sprocket timing is fixed in reference to the IMS. The mechanical timing adjustments are done all in the heads between the sprockets, cams and of course the tappets for lift. If the timing was done by the IMS then the sloppy gear lash issues this engine has would be causing timing issues anyways.

 

I came across this in one of my emails from PCA. Has anyone have any input on this. Would this help the situation.

http://www.lnengineering.com/ims.html

 

This is for the 2.7,3.4 and 3.6 NA wet sump engines not the metzger engine setup. The IMS bearing on our engines cannot be replaced without a complete teardown. The wet sump engines can have the bearing replaced much easier and use a ball bearing as opposed to the bushing setup our cars use. Good read though and some very good info on oils that pertains to us too.

Many engine builders suggest upgrading to the GT3 IMS when cracking these engines open because the sprocket and shaft are all one piece and they have less lash and bearing wear issues. This shaft is what the 959 used as well as other 911 race spec cars.

 

bank 1 and bank 2 are ran off the ims. the timing chains do not contact the crankshaft at all. So what would be the "mian mechanical component"? The split gear showen only has the load of one cam not four, an main oil pump, and the scavenging oil pump for the turbos. Why would you want forced wear on a prime part like that? The add heat, by way of added fiction. Weight, all the components need to make it work plus add size because the gear is sized for its load range and now will need to be larger. The spring pre load would have to overcome the load of all the components listed above and deal with a crankshaft that want to stop every 120 degrees. How big do you think the gear would need to be in width? Then the next big fix will be a light weight ims that will increase your spool time, increase your rpm (straight cut gears add 200 rpm already). Here is my sale pitch "I you thought your lwfw was worth the weight saving then you must have one of these..." lol. For real now the load on the ims is so great that there is really nothing short of perfectly cut gears and no slop in any of the other parts connected to it. Welcome to the flat 6.. Love her or leave her.

 

That is for the N/A motor M96/M97 not the gt1 motor.

 

The main mechanical component in keeping the cam timing is the sprocket assembly. This clocks the cam in relation to the sprocket. The IMS drives them and is the main mechanical drive.

As for the wear just think that every knock in your engine is metal banging metal. The gear lash slop causes gear teeth to gear teeth hammering. Over time it can cause issues. So I don't think that the spring loaded IMS gear would see any more wear than the stock IMS gear. The slop is so small that it would only require a small amount of spring loading to avoid banging. Probably would be difficult to even see looking at it. I don't loose sleep over it personally, but it is a factor in the noises these engines make. I agree it is the nature of the engine though. The aircooled engines have other noises to deflect the attention away from IMS noises. Without those other noises you would probably hear it bad on them too. If your engine makes metal and it gets torn down I would replace the IMS, but I would never tear one of these engines apart for an IMS noise. A new IMS will be quiet for a while. But I would bet that they return again eventually so it is not worth it IMHO. If I were the guy making money off rebuilding your engine I might tell you otherwise though

 

what noise? I have no noise other than my LWFW and my loud exhaust

 

HAHA... I pay no mind to the ims noise at all. When the motor would like to stop every 120 degrees there has to be some knocking.

 

What's the big deal. It sounds like a Metzger engine Porsche. It's not broke if it's SUPPOSED to sound like that.

 

Thanks for the reply guys

I understand that the engine is ok making this noise but i'm sure many would love to fix that noise if they ever had to do a rebuild. I'm just saying someone could make money with this. There are enough complaints to have a good business case.

Is everyone sure the noise is the IMS gear or could it be one of the other gears?

 

The 996 Turbo engine is a real good engine and the intermediate shaft is not a problem.

Gear driven shafts can be a bit noisy but they are reliable and efficient. If one wants to avoid a noisy engine buy something with a rubber timing belt. Then worry about having this belt changed every once in a while before it breaks and ruins the engine.

Besides the noise may not come from the engine's intermediate shaft and its gear drive.

In my 03 Turbo the 'rattle' that I hear comes from the clutch or possibly the tranmission. When the engine/drivetrain are hot up to operating temperature sometimes when I bring the car to a stop and I always shift into neutral and let the clutch out I hear a rattle/light knocking noise that goes away when I depress and release the clutch pedal.

Sincerely,

Macster.

 

I understand that gear drives are more reliable I just think this is a possible solution for people when they do a rebuild.

I'm comming from a belt driven engine. I just sold my 400WHP DeLorean with a 2JZGTE engine in it. Very reliable, strong and smooth sounding engine.

 

I have got it too, especially in 2nd gear and when below 2000rpm. Since I installed the sport clutch with lighter fligh wheel it's even more obvious then before.