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Brando
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Boost leak.
I’ve been having trouble that I couldn’t figure out. Chris Carrol told me to look for boost leaks. I believe I may have found it.
 This blow off valve is so weak that my engines vaccume pulls it open at idle. I’m guessing I need a larger spring since I have a 1bar+spring. I was looking into that before anyway. Now I believe I’m losing boost from the weak spring letting the valve open up under full throttle. What do you guys think? It’s a tial knockoff. Which spring would be appropriate?
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Turbo powa! 1977 911s. it's cool |
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10-02-2018, 07:05 PM
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Turbofrog
Join Date: Aug 2009
Location: Europe
Posts: 1,677
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If the boost goes against the piston or diagram opening it should be ok. I aim for loose spring so it helps the turbo spin out of boost.
I had great success doing a DIY pressure tester installed on the throttle body. Lots of little leaks was found and I got my idle vacuum back.
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************************************************** ******************************* 10/78 930: HX40Super, MS3pro+IDX1050+044+E85, ITB, 12 Denso COPs, TrueSplit-BB/2*38WGs, Weight<1100kg |
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10-02-2018, 07:25 PM
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Brando
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Tell me about your setup.
You think the opening at idle is ok? I didn’t like unfiltered sir. |
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10-02-2018, 07:32 PM
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Brando
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Ok I found that boost leak. And the car is happier. Actually a little angry too but in a good way. I now have full boost (over 1bar) by 3400rpm. Wowzer. I’m a little frightened about that much boost and think I need to hurry and get it tuned because I’m getting too high of an afr. Need to get it sorted.
The leak was that blow off valve. I found a helper spring and installed it. It does open at throttle opening. Gives a nice flutter psssshhhht sound.
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10-02-2018, 07:52 PM
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Turbofrog
Join Date: Aug 2009
Location: Europe
Posts: 1,677
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Mine is recirculated so no unfiltered air with loose DV operation. THere has been discussion here earlier that bypassing some air at low revs and vacuum might help the turbo spool.
1 Bar by 3400 is nice. Was that in third gear and stock transmission?
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************************************************** ******************************* 10/78 930: HX40Super, MS3pro+IDX1050+044+E85, ITB, 12 Denso COPs, TrueSplit-BB/2*38WGs, Weight<1100kg |
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10-02-2018, 09:29 PM
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Brando
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My transmission is 930. I believe I’m getting that in second gear.
The gt35r is pretty good.
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Turbo powa! 1977 911s. it's cool |
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10-02-2018, 09:44 PM
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Registered
Join Date: Oct 2006
Location: MYR S.C.
Posts: 17,321
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that's probably not the best place for the BOV. lots of heat.
I tried venting my BOV to atmosphere. I have tried 2, both new. a synapse which is somewhat adjustable and the (I think) the 965 style with different springs. they both opened at idle. I could put in a spring or adjust it so it would not but then is would not open when letting off the gas. the car ran GREAT with it open cruising down the road because it made it run richer back when I was having a lean issue. it would close as soon as I went on boost because there is no loner any vacuum pulling it open. so just because it opens at idle does not mean it is open on boost. now, if you have it in the "push" mode where the boost is trying to push it open it "could" be possible it is opening under boost. I have run mine both ways and I cant recall that mine opened under boost when it should not have. oh, when it is open at idle that IS an air leak and will make it run lean. mine would idle like crap with it open at idle. problem I have now is the rubber Orings in the 965 style are bad and it wont open when I let off. you can tell when it does not open. you get that cool "chsh chsh" sound of the 962's back in the day. I don't think that is good for the turbo though. make sure it is opening when it should. remove the hose to the BOV so you know what it sounds like when it does NOT open.
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86 930 94kmiles [_  _] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD88 BMW 325is 200K+ SOLD 03 BMW 330CI 220K:: [_ _] RUNNING: [__] NOT RUNNING:01 suburban 330K:: [_ _] RUNNING: [__] NOT RUNNING:RACE CAR:: sold Last edited by T77911S; 10-03-2018 at 03:52 AM.. |
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10-03-2018, 03:40 AM
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Brando
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77911s,
Remember I’m not cis anymore. I’ve gone efi. Infact I don’t have the same engine at all. This bov was opening under boost and letting boost out. With a stronger spring it’s now working as it’s supposed to. Now my problem is the tune seems to have changed and I need to look at the part throttle afr because it is going lean. And also the boost is higher than I’m comfy with till I tune it. It’s like woah. This car has changed from pissing me off and wanting to sell it to once again impressive. The potential power of it is strong.
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10-03-2018, 05:44 AM
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Turbofrog
Join Date: Aug 2009
Location: Europe
Posts: 1,677
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Do you have a log to show of that second gear 1bar 2nd gear pull? That would be crazy fast spool with gt35r!
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************************************************** ******************************* 10/78 930: HX40Super, MS3pro+IDX1050+044+E85, ITB, 12 Denso COPs, TrueSplit-BB/2*38WGs, Weight<1100kg |
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10-03-2018, 07:07 AM
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Brando
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I have a flight recording but my driving is pretty timid because I’m watching afr and boost and they’re a little freaky. My highest boost on the recording is actually higher than I thought it would be, 17.1psi and afr was 12.74! Rpm was 4165 on that run. My throttle opening was over 3/4.
After last night I haven’t wanted to do any sustained open throttle runs at all. Peddling it big time. .
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Turbo powa! 1977 911s. it's cool Last edited by quattrorunner; 10-03-2018 at 08:17 AM.. |
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10-03-2018, 07:14 AM
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hoonkraft
