Boot for 3.5 HFM?

[BeirBrennerE30]

Alternator cooling duct...

[redhatpat]

Abe, what's that air hose that goes to the top of the radiator?

Alternator cooling duct. Stock on e36s. I'm not sure it's really needed.

[MR 325]

Matt, you can also heat up the stock elbow and stretch the 3.5 MAF over it. It takes just a few minutes with a lightbulb and a skinny flat-head screwdriver.

Well I WAS just thinking of doing this. That's what I did with the M30 AFM on my 85. My only concern is the boot is showing stress crakcs on that car where it's stretched after a year of use.

[matt]

Was the M20 boot new when you did that?

A new boot should stretch fine.

[Stu]

If you get a new boot ($10, $12?) you shouldn't have any issues. Mine has been installed on the 3.5" MAF for 4.5yrs and 90,000 miles and it doesn't show any signs of cracking.

What about the other side, if you want to retain the stock airbox from your E36 engine instead of installing a cone?

I don't see how this would be affected by the intake boot?

[MR 325]

Fuck it, stretch boot sounds good to me.

Thanks Stu.

[318isbmw]

The cheap 3 to 3.5 one from silicone intakes worked great for me. Drilled the holes in the underside so you can't even see them, works great and seals well. Never had any problems at all with it as well as a few friends w/ e36 m3's who track them haven't had issues with theirs either doing the same.

[grib]

I have tried all three methods (stretching a new stock boot, the DIY silicon piece and the Bimmerworld 3.5" to 3" boot).

Would not go the DIY route again. The elbow they send is really thin. It's hard to cut/drill clean and even harder to adhere the two external tubes to. I couldn't find an adhesive that would bond the plastic elbows to the silicon, and when they cut loose you have a MAJOR vacuum leak. The professional boots wrap these tubes into the silicon, so it's an entirely different method of bonding. For the folks who got the DIY elbow to work - I'd be curious what adhesive worked.

If you're trying to do it on a budget - stretch a new stock boot. I did mine by dipping it in almost boiling water, then using two large flathead screw drivers to stretch it over the MAF. Frustrating, but once you get it it's solid and you have that feeling of victory.

When I saw the Bimmerworld piece I knew I wanted it. The flow has got to be much smoother without that "accordion" section and it looks much cleaner. They are usually back-ordered, but it was worth the wait on the price. Really solid piece, and really clean looking (especially in the black). It comes with a couple of extra inches on the MAF side so you can trim it to fit your application...

[318isbmw]

I drilled the holes so they were small enough that they were a tight fit. Was a total pain in the ass to get the plastic pieces into the elbow, but holds snug w/ no leaks as is.