My car used to reliably make 15psi at WOT. Now it makes 11-13 psi - but will sometimes build up to between 14 and 15 psi very slowly if I really wind it out. So it sounds like I have a pretty subtle leak. I have fairly new OEM intercooler boots. Any tricks to isolating the boost leak?
If you are confident the boots are not leaking, then the possibilities are few Isn't there a zip-tie BPV test you can perform to determine if the BPV is at fault? What about your boost gauge, could it be leaking where that line is attached? I have had the line fall off a couple of times, but the result was a dead boost gauge and of course a boost leak, so it was not hard to remedy.
Knowing sorta how you drive....the clearance on the SC rotors may have increased? No easy way to measure or determine this except a tear down.
I can test with my old boots (which were not leaking when I replaced them - preventative). I have a DT BPV - a couple of years old. Should be good, but I've thought that might be the culprit. I don't have a boost line connected - I read boost via Scanguage. If the FPR line were disconnected I'd know it. I don't know if there's something in my JCW airbox that could be leaking - I could disconnect and seal the line for a test I guess. Good but chilling through on the SC rotors. Yeah, I DO drive that way. :cornut:
The JCW airbox is pre-boost in the system so anything leaking there will have no bearing on max boost. It is possible that something in the intake is clogged to the point where it is limiting flow, but I doubt that knowing how well you take care of your car...........sorta.
Yeah - I forgot where that nipple was on the BPV. So potential culprits are: IC IC boots/clamps Horn gaskets Water/meth nozzle Intake manifold nipple/ hose to FPR Intake manifold gasket BPV
I don't think he noticed a leak but observed lower than accustomed total boost psi. He has many monitoring devises on his MINI that might show changes and even a possible engine code in the stored ECU memory which might help with the diagnosis. His list as quoted: So potential culprits are: **IC **IC boots/clamps **Horn gaskets **Water/meth nozzle **Intake manifold nipple/ hose to FPR **Intake manifold gasket BPV Because the indication is the total boost psi eventually comes up you can pretty much rule out:** All of those would effect a constant total psi and not gradual time reduced to maximum psi. Other things to compare. Engine timing and AFRs.
With regards to BlimeyCabrio's MINI and his thread concern When I make an internet assessment I consider who the owner is and how I know that person treats his MINI. So your scenario would not be the case with BlimeyCabrio. And to answer your question, yes the air filters condition can effect boost perimeters.
Reading from the starting post information you can rule out head leaking because no engine code information? The poly belt although a good thought also does not have to much merit because of inconsistency in the behavior of the boost as posted.
I had a IC boot going bad and until it really started loosing boost there were no codes thrown. A very small leak down given enough time pumping air into the system could slowly build up boost as described. Given the stock boost the ecu might not think anything is wrong when he's building 11 to start....
Two questions: How many miles on the car at this point? Where does the computer read the boost pressure from? Could a bad sensor fit the symptoms?
How long has this been the case Blimey? Hasn't it been like hot as hell as of late, that could have the boost down a little too.
You may becoming confused by my responses? Your scenario has a description of consistent desegregation and not as this threads first post describes a specific inconsistency. Now in your case we have to think about all the reasons why an IC boot would go bad in the first place? A thought about Super chargers in general. By lowering the restrictions or increasing inductive flow you also lower the resistance which will inevitably lower the total boost. I would think we need to wait for more information from BlimeyCabrio to practice further internet technical diagnosis.
Thanks for the help guys. More details: This was really noticed at a recent re-tune on the dyno. But in retrospect, I can attest that it had been going on a while - I keep BST displayed on the ScanGauge all the time, and I can recall that I haven't seen high boost numbers as consistently as of late. Car has 80K HARD miles. Otherwise all is well. No codes, no weirdness stored when I interrogate the ECU with Autoenginuity. Belt is pretty fresh and doesn't appear to be slipping - that would have shown up on the dyno. Maximum boost I can attain is about where it should be... just takes a LOT longer pulling at WOT to get there than it used to - I used to hit 15psi after only several seconds of WOT. Now it might not get there after 30 seconds of WOT. Only thing that has changed that I can think of that MAY have corresponded with the boost behavior change is Thumper-1 head installation. Basically just a ported and polished head, stock valve size, probably similar to JCW but maybe a bit more aggressive in the porting. I don't know for sure that the boost changed at that point in time... but I know it boosted strong at some point before the head was installed, and I'm not sure it has since the head was installed (but it may have... I'm not sure). Does it regardless of ambient temps outside. Same at 70F and 100F.