Air Pump Removal - Main Bearing Stress?
 

So I know there's a big thread related to this topic but I'd like to open up a sort of new (to me) line of thought on removing the air pump on my FD;

I'm converting to a single turbo and wanna delete the air pump. The thing is, I don't want to buy an idler pulley unless I absolutely have to. The reasoning I've heard behind getting an idler is it keeps the eccentric shaft from being pulled too far in one direction and making contact with the main bearings and prematurely wearing those out. So is this a fairly well documented problem with not running an idler or could I potentially just run a much shorter belt?

Big thanks guys,
Andrew

I was under the impression the main reason is to keep proper contact on the water pump pulley.

Tom

Didn't think of that, but also a good thought. Any known cases of running no idler or air pump?

Remember that the amount of torque a belt can produce is exponentially related to its angle of contact with the pulley. So you can see increasing contact angle will produce much more torque w/o over-tensioning the belt.

I have seen first-hand evidence of the problems with not running an airpump idler pulley.

- Bad water pump bearing and erosion in water pump housing, both had to be thrown out.
- The side the e-shaft was pulled towards showing lots of copper in the front bearing
- I have heard of spun bearings but not personally seen this.

Those idler pulley kits aren't much, Pineapple Racing and Full Function Engineering make really nice kits that aren't too pricey. As a bonus it's MUCH easier to find a belt in the correct size. Had a buddy lose a water pump one year at Deal's Gap and shredded the belt. Went to a parts store in rural North Carolina and picked up a new belt no problem. Got a water pump from a guy at the rally and back in business.

It's just foolish to try and get around it at this point. Seriously the only downside is the reasonable price it cost to buy one, everything else is a positive.

Dale

I ran a twin turbo set up with no airpump and no idler for a year or so, being careful to not over tension the belts.

My water temps would rise very quickly at high RPM, presumably because the belt was slipping past the water pump pulley. I eventually fitted an idler and my water temps were much more constant, though I'm looking for a way to get rid of it or find another solution because it doesn't leave much room for an air filter on single turbo.

Pineapple has a single turbo version that tucks WAY down in there, it's supposed to give plenty of room for a single turbo setup.

Dale

I didn't watch the whole video but looks like it should give you an idea if it would fit your turbo---->
FD Idler pulley conversion kit

Seems like I should install it with the engine still out of the car, then. Big thanks for the help, guys

You can easily do this with the engine in the car FYI. But it's always easy doing things like this with the engine out.

Dale

Do not be one of these cheapo FD owners. Either do it right or sale the car.

Just bit the bullet and picked up the Pineapple Racing kit. Only reason I went with them is for the same price as the FFE kit, Pineapple included a belt, whereas FFE wanted an extra $20 for a belt.

Thanks for all the advice, folks!