i recently installed a hallman mbc, and put the car at 21 psi. , ran perfect for about a month and a 1/2, now all of a sudden, my boost will only hit 15 psi and taper to about 13, i cleaned the mbc as per reading posts, but no change, checked all hoses and everything looks goood, i have read many topics and cannot find any help....... any ideas?????

 

Check your IC pipings or couplers. You may be leaking boost.

 

will do, and post with any results.....

 

checked i.c. hoses and all are tight (using samco silicon, never failed before) checked turbo and intake hoses to mbc and all are tight, when i shift at 3000rpm, my bov gave a nice tight discharge, now it flutters, is this because of my low boost or could the bov be bad???? (i thought the bov would not affect turbo pressure at all,or am i wrong??)

 

Eh, you have an aftermarket bov? Is it venting to atmosphere? Cause if it is that's bad on the evo. Screws up you air flow readings because they vent metered air. Recirculate only.

 

using a greddy bov, NOT venting to atmosphere......it was on the car for over a year and have never had a problem...

 

Check the vacuum line / replace it going to your gauge thats what happend to mine it had a leak in the hose. I'm running VTA on my GFB Stealth FX and Zero problems... even before my tune.

 

So did you actually do a boost leak test or just make sure the bolts/nuts are tight on your hose clamps/t-bolt clamps???

 

did not do a boost leak test, cannot find a thread that gives good instructions, i doubt if it can be too hard, any guidance???

 

If you don't know how to do it, go visit CBRD or something. The only way I know of to do it involves an air pump, pressure gauge, and a little welding . There are probably easier ways though.

If I had to guess, I'd bet your LICP is loose, it seems to happen a lot on the evo 8. Make sure you don't have any pin hole leaks in the hoses, make sure you use NEW hoses for your MBC (you don't want to reuse the old ones, though many people do), make sure all your fittings are tight on the UICP'ing. Check around the outside of the head and make sure there isn't any fluid leaking (leaky head gasket or something), make sure your spark plugs are torqued correctly.

That's all I got, but you might want to take the trip to CBRD and just get it over with. If your closer to NJ I know a couple of shops in monmouth county.

 

thanks, i'm pulling it apart tonight to check and reseat everything......

 

If you can only boost to 15 or 13 psi, if it's a boost leak, there's no need to do a test. There would have to be either a hose completely ripped off or a big hole in an ic pipe. And in that case the car wouldn't idle or run smoothly at all. It's not a boost leak. It's either a mis installed part or a defective mbc, or bov, or a leaking or broken hose. I've had the same problem that you're describing and the car basically would boost to 22 psi one minute and the next pull it would only boost to 17. Mine turned out to be a mbc issue. I cleaned it and lubed it and it went away. ??? I would check every hose on your intake mani. (FPR hose, etc.) And if you have a boost gauge trace that line and see if it's leaking. Then check out your bov ajustments, the WGA, and mbc. To be boosting that low means the problem should be obvious once you look around a little bit.

 

If your really curious, I think I have a spare Forge MBC somewhere . I'm using an AEM truboost and have no desire to ever re-install that thing.

 

The easiest way of doing this is to visit somewhere like Home Depot or Ebay (this one is kinda elaborate) -

http://cgi.ebay.com/ebaymotors/Evo-T...QQcmdZViewItem

As for making your own with Home Depot type goodies - I got a 2.5 inch -2.5 inch hose coupler, a 2.25 inch PVC end cap that would sit inside one side of the coupler, and a valve stem. I put the PVC end cap into the hose coupler then I sealed it with some polyeurethane, then I drilled a hole in the cap and sealed in a valve stem seal the same way. Remove your intake and lock on the coupler, then pressurize the system. I used the valve stem with my air compressor to do this. Get a spray bottle of soapy water and spray it at every vac hose and hose clamp to detect leaks (it will bubble nicely). This is what I did on my DSM, does wonders. Also I used a mechanic stethescope to listen for leaks inside the throttle body (yes it really worked ). You might want to have someone watch your boost gauge. With my DSM we usually pressurized the system to 30-35PSI since that's all I ever boosted. Really sounds like hose coupler, vac hose, or some vac cap popped off. Good luck!

 

As TheGame just stated in the above and I stated before. Check your boost line running to the Boost Gauge.