so a little while back i put on a turbo xs mbc and was working fine until recently when my boost started hitting 15 in the middle of the day and 21 (desired boost level) at night. i know the temperature has a little to do with it but im not sure if it can affect it that much. does anyone else have this problem or know the answer?

 

There will be a change from cool to hot weather and back, but it shouldn't be that drastic. Unfortunately, I think you missed out on the fact that the TXS MBC is no good for the Evo. I am not sure why people still buy them when we are constantly telling people that Forge and Hallman are the best...

 

What gear were you in when you did these comparisons?

 

i have tried in every gear when its hot and i always get 15 but at night i tried in fourth

 

i now have a hallman pro rx mbc and the inlet is coming from the bov line and the outlet is going to the wastegate actuator but i still have low boost problems during the middle of the day. no matter what gear im in i cant get past 16. also since i live in utah would the combination of the high altitude and 100 degree weather have something to do with it

 

Do you have a stock DV, or an aftermarket BOV?

 

im not exactly sure what a DV is and i dont know if i have a stock bov because i bought my car used and i dont know what the stock one looks like. but i have been told its an aftermarket one.

 

1) Yes, hot weather makes the boost lower, and 6000' altitude makes the turbo way less efficient and thus tapers more.

2) DV = diverter valve = BOV. Technically, a BOV vents to atmosphere, but we refer to DVs and BOVs interchangeably

3) You'd know if you have a stock or aftermarket BOV if you did 2 minutes of searching to educate yourself, yah?

Despite all of this, your boost should not ever be limited to a max of 16psi peak. I can see if it's tapering to 16psi, but if it's not able to peak at 20psi or higher, then there's a problem. You may have a soft spring in the MBC that only goes to a certain max psi and may need a stiffer spring.

 

could this be another snorkel syndrome???

 

well i put the stiff spring in the mbc and it does reach 21 but still during the day it wont go any higher than 16. and yes i do now know i have a aftermarket bov.

 

Yeah, that doesn't make sense. If it hits 21psi at any point in time, then it should still hit close to 21 even during the hot summer day. Are you sure you're not comparing peak boost from a roll-on at low rpm vs shifting through the gears quickly? YOu only see peak boost at ~3500rpm. If you shift through the gears quickly, you see lower peak boost, because you're never below 5000-5500rpm, and the boost has tapered by then.

If you go out right now, put it in 4th at 2000rpm and floor it, you're saying it only spikes to 16psi max?

 

yea thats it. and as my engine gets hotter it will go even as low as 14

 

Bad juju. Have a knowledgeable Evo owner look at it and do a boost leak test.

http://vfaq.com/mods/ICtester.html

 

and no its not a snorkel syndrome because i have an aftermarket intake

 

i have now tested it for boost leaks and there is one and it is comming out of where the throttle cable is hooked to and i have no clue how to take off that part. any suggestions?