More boost problems

[davidgt97]

I have crushed my BOV and the car held 18psi great but it was fuel cutting horrible. I just got in a 2G MAF so I decided to go ahead and put it on to see if it helped. I put in the 2G MAF along w/ a set of 560's and custom made my own intake pipe. It ran great w/ no fuel cut at 18psi a few passes. I took it out for another trip down the road and came across a RX-8 who apparently didn't know any better. I played w/ him for a little bit and then passed him like he was stopped, but as I passed I noticed it felt weaker. I checked my boost guage and was only making 10psi. I took it right home and found that apparently I didn't have the BOV recirc hose on tight enough and it had blown off. I put the hose back on and started it back up. It idled smooth and the AFR's on my wideband at idle were at about 14.5. So I took it out again only to find I still can't make more than 10psi. I tried playing w/ my MBC and the only time it will make more than 10 is turned all the way up which is just blocking off the wastegate and I have to let off the pedal before it gets to 20. I also tried doing a leak test at the TB and it seems to leak off rather quick. The only leak I could find was where it was coming out the valve cover breather. I'm again puzzled

 

[davidgt97]

I went out in the garage today and tried a few things that will hopefully help someone diagnose my issue. I started w/ another boost leak test and found a small leak on the small BOV line at the clamp and fixed it. I also pulled the hose off the pcv and blocked it off. I seemed to be able to hold pressure longer like this. I also pulled the pcv out to try some blow through tests. If you blow air through the valve cover side it feels unrestricted(as I believe it should.) Then I put 20psi to the other side and some air did get through. I regulated my compressor to less than 10psi and could still hear a noticeable amount of air getting through. Isn't a PCV essentially a check valve? Should any air be getting through? Also I did a warm comp test and got between 150 and 155 on all 4. This engine has less than 2000 miles on it. Is this good comp? I have heard some say that pefect comp is 178, but a friend told me this was for the N/A cars.

 

[brando12685]

possibly a problem with your mbc. try disecting it and take a look if anything looks messed up.

 

[davidgt97]

I was actually thinking the same thing today. It is a cheap EBAY MBC. I'll try to find someone who has a good one and swap it out.

 

[davidgt97]

I have ordered a voodoo ceramic ball & spring type MBC. I should be in any day now. I pray this fixes my problem.

 

[anteversion]

compression should be 167 psi max for 4g63t engine.... yours is good since both are almost equals. 14 psi is the max limit difference between 2 pistons. PCV can only let the oil vapors to be evacuate. thats means that air cannot enter by this valve, but can only exit. an it works only when a vacuum source is plugged to.Cheap ebay mbc are very very not working great. my friend bought one last summer and it was only spiking