Audi S8 5.2 V10 performance parts take 2
Now back to the performance parts of the build. Last time we talked about the JHM intake spacers and their ability to help keep the 5.2 V10 heat issues in check. While the spacers are helpful at keeping the motor cooler and more efficient the motor could also beit from shedding some of that unnecessary weight strapped to the front end of the crankshaft.
Installing LW parts onto the rotational assembly of the motor for performance gains are not new. This has been around since people have been hot rodding cars. Things like underdrive pulleys and lightweight pulleys have been a big part of the performance must do’s. We all know the huge gains seen with adding an LW flywheel if you have a manual car. We have a huge TQ converter strapped to the back of our motors filled with several quarts of transmission fluid and since we obviously can’t remove that we now look to the front of the motor and the crank pulley.
Why would you want to remove and replace your crank pulley? Simple, if you want to see the science behind this go cut a piece of string just over 2 feet long. Then from there tie a 10lb weight to the end of that same string and see if you can swing that 10lb weight in front of you like a propeller of an airplane. If you even can swing it, try to keep it going at a constant speed, then after a few seconds try to swing it as fast as you can. It will take a large amount of effort to get the speed of the weight to accelerate. After you did this replace the 10lb weight with a 2lb weight and repeat. The results will be drastically different. You’ll be able to speed up and control the 2lb weight and its spinning speed much easier and with more acceleration on demand.
That’s the crappy roadside simplistic explanation. The physics behind rotational weight reduction are sound and impactful. The JHM LW crank pulley allows the motor to spin up faster and with less work. It allows for much less resistance in rotational acceleration of the motor RPM. This results in a much more eager throttle response out of the motors acceleration and its simple.
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You’re dropping almost 9lbs off the front of the crankshaft.
So, for those of you who don’t know where this is or what it looks like. Let me show you.
Here are all the important things I reference where they’re located and what they look like.
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You’re going to have to pull the front end of the car off to replace your crank pulley. While I was in there I decided to remove the SAI system. SAI stands for Secondary Air System. It’s the system that turns on in cold weather to help your cats heat up quicker. The downside is the car tends to run rougher on cold starts when it’s activated and over time people have seen terrible carbon build up in the SAI valves. So, for me, I just removed it. Keep in mind unless you have a JHM tune doing this would result in a CEL the first time the SAI system is required to turn on.
Back to the pulley install. For me, the JHM LW crank pulley was a no brainer. It’s like doing the intake spacers when you do the carbon clean. You’re going to be in there anyway, you might as well put in the spacers while you’re there.
I was replacing my OEM belt that looked to be original and also looking to service my belt tensioner. The belt tensioners like to freeze up over time so, I would pull off the belt, take off the tensioner and lube it. While I was in there I added the LW crank pulley.
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The stock crank pulley is definitely heavy. Even if you don’t have to replace the belt it might not be a bad idea on replacing the crank pulley. The B6 and B7 S4’s had issues with these failing and the B8 S4s are known to have their crank pulleys fail.
As mentioned, while I was doing the maintenance I decided to remove my SAI system.
Here is a picture of all the other hardware removed. You can clearly see what lines are the SAI lines. They tap into the front of the cylinder heads.
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You can’t just pull the SAI lines off and not cap them. Or you’ll have exaust gas coming out the front of your cylinder heads. So, I quickly cut and welded the ends off the SAI lines.
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If anyone wants more pictures on the SAI removal let me know. I removed the pump and the valves that were located off to the side.
After the SAI lines were off and I made the caps I started putting everything back on again. Making sure to use Locktite on the crank bolts and using a nice white lithium lube on the belt tensioner.
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The crank pulleys on the 4.2 S4 and S5 are just like our crank pulley on the 5.2. They are counter weighted and that’s something serious. The money in the pulleys is in the balancing of the pulleys to make sure they have the right counter weight.
Years and years ago when this came out for the 4.2 S4 a few people would try to make the argument that putting an LW pulley on would cause issues. Well, there been no issues with the 4.2 S4 or S5 after 10 years and after several motor teardowns for built motors in the 4.2 there was no sign of any bearing issues. As a matter of fact there seemed to be less bearing wear on cars with LW crank pulleys over OEM units.
For fun, I did a crude test to show there was no change in NVH. I did the oldschool water on the intake test.
1800rpm
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3200rpm
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from 3200 back to idle.
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There are huge offset weight tolerances in the OEM pulleys where the JHM units are balanced with precision balancing. I actually noticed a smoother idle and lower knock voltages when crusing with the JHM LW pulley.