Can anyone tell me....

If the bpv is not closing, partially or completely, would a boost gauge still register boost? I'm thinking that if the sc is spinning fast enough, it could still be creating positive pressure in the intake manifold, even if an open bpv is thwarting its effectiveness.

 

I have the 16% pulley, cai, DT bypass valve, etc. - this makes boost come on pretty quick and makes for great acceleration. However, in normal driving (even with a dip into the throttle) my boost gauge is reading vacuum. In order to get the needle to register pressure I need to punch the accelerator and keep squeezing it down. The instant I let off or even stop squeezing the needle starts drifting back to vacuum.

 

Mine is the same way, but my car doesn't feel like it's getting boost, or much of it. I *can* make the boost gauge needle sweep over to the 10 lb range if I floor it and hold it, so I thought the bpv was probably ok. However, I'm starting to wonder if it's really *not* working properly, but the gauge can still be made to show boost in the manifold. The car feels a lot like it did when I *did* have a bad bpv.

 

I haven't had any bp valve issues, so can't advise on that. btw, not sure what mods you have, but I can hit 15psi of pressure. Could the fact that you only hit 10 be an indication that there is a leak somewhere?

 

when i had the 15% I made just under 15psi, with the stocker 10psi.

 

my car with the DT BPV just takes a little tap to get it from 10hg vacume to 0 then a little squeeze of the throttle and it starts to boost. When cruising at a steady rate I am at 10hg vac on deceleration with no throttle at all I am at 20 hg vac. Then at full throttle about 6k rpm I can hit 17-18 psi thats with 15% pulley.

 

No mods on the intake side. Stock JCW with a header and exhaust. I used to get about 13 lbs boost maximum, now it'll get 12 at wot above 5,000 rpm with the pedal floored, but usually it hangs at the 5-10 lb range, and I have to shove my foot in it to get that. The thing that makes me wonder is that aside from the general feeling that it's down on power it also rarely gets into boost. I also seem to run around -10 at steady state cruising, and -20 if I take my foot off the gas. If I floor it, the needle jumps over to positive and the car makes a lot more noise and goes forward, but it doesn't feel like it's being thrown down the road like it used to.

It's going in for a 100k service soon, and I'm going to have them do a pressure/smoke test for leaks as well. I've got a DT bpv that I may have them throw in at the same time. It was in the car before, but I was having driveability issues with it, so it came out. May give it another shot.

 

Maybe it's your blower going on you? Your BPV butterfly set screw could have backed off too allowing you to recycle boosted air.

I threw a code when I had a leak in between TB and SC. Smoke test found hairline crack in plastic duct between TB and SC.

Jeremy

 

From experience, I believe it should. I replaced my valve with the DT one. My boost gauge still showed boost before and after the mod. The old valve's spring was very loose, took almost no effort to open and close the valve. The difference being after the mod that when I let off the gas, it immediately dropped back to vacuum instead of gradually settling down.

So down throttle--boost up---up throttle, immediately boost off after the DT BPV.

Richard

 

I hope not!! It's only got about 50,000 miles on it.


That's an interesting theory.

I'm not getting any codes for leaks. After the header went on a couple weeks ago, I got codes for the O2 sensors. Those and a fuse got replaced, and no SES light since. Like I said, though, when I have the car in for service, I'm going to have them do a pressure test on the intake to be sure.

 

Right now, I've got: down throttle--zero boost or vacuum, down further throttle--moderate boost--not much more power, down HARD on the throttle--car goes, "huh? Oh! Oooookay... let's go... if I have to. But it's sooooo much woooork."

Needle instantaneously jumps back to vacuum if I even think about lifting the throttle even the slightest bit.

 

Oh 70spop, I thought you meant you're are 100K miles(your upcoming service)??? Or is this your second blower?

Jeremy

 

Right. I'm at 100,000, but the blower is the JCW one that was put on at about 50,000 miles.

 

Hey not to be out in left field, but the gauge can still register boost depending on where it is tapped, and a portion can be lost to any number of causes. Have you tried checking the boots to the TMIC? If those get punctured or are starting to wear out, you can loose boost there. But if the gauge is tapped on the S/C side it could still register a lot of boost. Also, you should see boost when you dip the throttle in. No real delay. The S/C will go from vacuum to boost nearly instantly.

Let me know if I can help further. May your boost come hard and strong!

 

The boots were just replaced with the new ALTA ones that I ordered when you sent the header, and I haven't noticed anything really different since they went on, so they're probably sealed up ok.

Yeah, the registering boost on the gauge even if it's being defeated somewhere else was what I was wondering about. And no, the gauge needle doesn't go into boost at tip-in. It does, of course, move toward the boost side, but in order for it to go to the plus side, I really have to bury the pedal. With just casual (but not pokey) acceleration, it will go maybe 2 lbs if it goes into boost at all.

 

Only 13lbs?!?!?

I'm getting 15psig normally and I've seen up to 17psig (Track Days) on my electronic Boost meter, with just a 15% SC pulley. I do have the 5-10in Hg during normal Highway driving, as well. I'm looking at doing the VGS mod, and I'm itching to get the DT BPV. Sounds like you may have some issues.

 

FWIW, when I installed my OBX header, i lost ~1 psi of max boost

 

I've got an OBX header, high flow Cat and free flow exhaust. Lost about 2psig, but that's why I'm looking to get the DT BPV. See if I can get the ponies to respond better.

 

hmmmm... I noticed a loss in psi after I installed my DFIC. I'm thinking I might want to get a smoke test, because I definitely think I have a leak somewhere.

 

I have an update - I had forgotten about this.

When I was at the Jan-tune party a few weeks ago, the car was giving us fits after the initial run. We couldn't figure out why it wasn't responding to the usual tuning tweaks. Then we noticed that the boost gauge needle was sitting at zero when the car was idling. A-HA!! So Dr. O removed the intercooler and we all started looking for a split hose to the boost gauge. Finally found that the end had just fallen off the nipple where it taps from the intake manifold. We put that back on, zip-tied all of the vacuum hose connections, and were on our way.

Since then - oh, and I had replaced the bpv with a new stocker prior to the tuning party and that had already made a noticeable improvement - the car willl jump up to 12-13 lbs boost with about 1/2-2/3 throttle. If I really push it, it will be up to 14 lbs once I pass 5,000 rpm, and gain maybe another 1/2 lb by 7,000 rpm.

I have a feeling that the hose to the gauge was/is only good for about 12 psi before it expanded enough to start leaking at the connection - I'm surprised it didn't blow off sooner. Now that it's all zip-tied, everything stays in.

 

i lost boost due to my belt slipping . went from 15lbs to 10 just from the belt .

 

I like electronic over mechanical. As a mechanic, I know mechanical is always more accurate, cheaper, and more accurate , but when it comes to the MINI, because mine is a daily driver with minimal track time, electronic wins out.

A mute point if your sender still has a mechanical interface, it could have still worked loose.