Really Weird... Boost Controller failing when hot?

hsk8te2006 · 07-07-2008, 04:10 PM

I'm running into problems the last 2 days with my boost levels, and I have an idea that I wanted to see if anyone has ever seen before...

Has anyone ever had a high-end MBC and had it not work correctly when it gets hot?

My car's drivetrain is practically stock, except for a hard UICP and crushed 1g BOV, and a K&N air filter.

I'm running a Voodoo II MBC (Ceramic ball& spring), piped correctly and mounted over my radiator, which was keeping the car at 14-14.5 psi all the time.

Lately, the weather has been hot (around 90 and humid, instead f the usual VT 75). yesterday, my car wouldn't boost over 12, and this afternoon it wouldn't boost over 10. So, I figured I would try and adjust the MBC to see what the problem was.

When I tried to loosten the locking collar on the MBC screw, I found the MBC too hot to touch without burning myself (thanks to being mounted above the radiator (to keep the lines short)). So, I poured some water on it to cool it down.

Then, just to see what would happen, I took it for a drive to see if cooling it down made a difference, and it did. For one 1st-3rd gear run, I got 14psi. However, about 1 min. later, it was back to only 10psi again, and the MBC felt warmer to the touch again.

Has anyone else ever seen something like this before?

CanadianTSi · 07-07-2008, 04:24 PM

The spring could be getting softer as it gets hotter.

You could also try sourcing the MBC from the Intake Manifold.

hsk8te2006 · 07-07-2008, 08:35 PM

The spring getting softer as it gets hotter would make sense. I also realized that I sat in the hot weather and read my maual for about 20 minutes with teh car idling before heading home earlier, so I bet that contributed to the heat as well.

As to sourcing it from the intake manifold, I'm not sure if I would want to for 2 reasons:

1) My car rarely gets hot enough (here in VT) for the radiator to give off enough heat to affect the boost levels.
2) I've hard that the shorter the line, the better.

I had considered maybe mounting it where the stock boost control soleniod is mounted (farther away from the radiator), but then I would need to take the intake filter out just to get to my MBC... probably not a good idea in case I want to adjust the level in the future.

hsk8te2006 · 07-08-2008, 01:01 PM

Update... this mornign when everything was cold it boosted to 14.5 perfectly.

Then, after driving it for about 20 minutes with the A/C on in 85 degree weather, it only boosted to 11 again.

hsk8te2006 · 07-12-2008, 12:53 PM

Ok... this sucks... i tightened the screw on my MBC spring severla times (about 1/2 turn at a time), in teh thought that if the spring had been re-shaped by the heat into a shorter shape, ti wouild help. Well, after about 6 turns, no improvement... still only boosting to 11, even when cold.

My thoughts for what to do next are:

1) Take the MBC off and make sure the internal parts aren't damaged.
2) Change my conical air filter (it looks really dirty right now).
3) Run a boost leak test
4) Buy a new boost gauge (in case it's faulty)

Anyone have any thoughts or auggestions to add?

Thanks in advance!

hsk8te2006 · 07-21-2008, 06:09 PM

Update... I removed my manual bost controller fromt eh car, and I removed the screw and all of the internals from the MBC. None of them looked damaged at all, so I set them back in the MBC int eh right order, and re-installed it ont he car the exact same way it was before.

Result: Perfect ability to control the boost level as it should be. Not exactly sure why, btu this may be useful information for anyoen else who runs into a similar problem.

(My guess is that the entire MBC and spring expanded around the upper ball, and rendered the setting useless with the screw near where it normally should be.)