1996 855 T5 - iPD Bypass valve kit coming tomorrow!

[Sommerfeldt]

I recently replaced the serpentine belt tensioner (much easier than I feared), which had become exceedingly noisy... but in removing that noise, a different one became very apparent. I had suspected that my BPV diaphragm was blown for a while (and has probably been leaking since I got the car), so I got one of iPD's kits from a local parts place.

It's arriving tomorrow, the postal people tell me, and my question is - do I go with the stock spring or the slightly stiffer one? I don't want to create any issues, and while the car's basically Stage 0, I don't have any plans to make this into a streetracer. Still, I would enjoy a bit more response from the turbo than I've been getting, so will going for the slightly stiffer spring be an issue?

Not looking forward to that lower bolt on the BPV...

- S

[kahl]

If it is IPD kit number 124917 it will have three springs. Stock, middle and crazy. I installed the middle spring IMHO it was just a little bit stiffer than stock. Here is a shot of IPDs direction on the spring use age.

[j-dawg]

The stiffer spring will surge? Hell yes! I love them chuchuchuchu noises.

[JDS60R]

Stock spring for your application.

[Sommerfeldt]

Seems to be some divided opinions.

Should be the kit with 3 springs, yeah. I'm ruling out the stiffest one, since I'm not in that range at all, nor do I plan to be. I'm being a little preemptive in my thinking as well as practical - if I should decide to get a tune up to R levels, for example, the "middle" spring will be the right choice, and I don't want to do this twice, me thinks.

So do you guys think choosing the medium one will create any issues?

- S

[abscate]

I put the blue spring on and my 1999 Chu-Chu-Chu-Chu laughs at the receding BMWs......

[Sommerfeldt]

^

- S

[JDS60R]

Yes- it creates an issue.

The CBV spring helps regulate when the CBV valve opens. If you have too strong a spring you are not protecting the compressor wheel fins from the pressure sent back to them when you close the throttle plate. The chu chu noise is the pressure back feeding through the compressor wheel. It may never cause damage or may break off a fin right away.

Its up to you - its your turbo.

[scot850]

Also, of less importance, the standard TCV is only good to about 12 psi, maybe a little higher before it starts to fail.

Neil.

[Sommerfeldt]

Thanks for your input, guys! So, turns out that they sent me iPD kit 11437 or something, which is basically the same kit, without the stock spring option - just the blue and red. So, I spent a few hours with the car, stripping out everything in my path to those 3 bolts, and got the thing off. Turns out that the original membrane was whole, but had for some reason been deformed somewhat, and the seal just wasn't there. This must have been going on for a while, since there was also substantial oil residue leakage from the lower part of the CBV - that stuff you see in your air hoses.

Anyway, since I had no other option, I went with the blue spring, and when I finally had everything back together, took the car on a run through its paces - carefully. And nervously.

Everything seems to be fine w/ the blue spring on my stock setup. No laughing turbo, only better response, quieter but still single release of pressure when I let up. I should mention that my T5's an automagic, so that might have something to do with it accepting the blue spring in stride.

I also cleaned out my distributor cap, where everything was a luscious green color, :O and changed the last of my vacuum hoses - the one that connects right by the intake hose.

The results are much better than expected - faster response, better boost buildup (a.k.a. BBB, I think) and probably better mileage, since this thing was obviously leaking pressure to the outside. It was a PITA of a job, and my fingers are pretty raw today, but all in all, highly recommended if you think the CBV thingy's broken.

- S