Boost question

Darkstar72

Active Member
So...today while out making some fueling adjustments since I was getting some KR in this cooler weather the boost felt great and gauge shot right up to 23 psi where it was set. I noticed some KR showing up so I changed nothing, hit the test button on the alky to make sure it would fatten up at idle which it did, and the next time I punched it the boost only got as high as 19 lbs. Thought perhaps it was a fluke and went down another back road for a third gear hit and same thing, topped out at 19 lbs. I just got back from another drive after letting the car cool off...same thing, 19 lbs max boost at WOT.

When driving to check for KR I only do full throttle pulls rolling in third gear. I guess I could try a few WOTs off the line to see where boost climbs to, but I’ve never seen my boost lower than 20 psi all year at WOT regardless of what gear I was in. So far I’ve checked all the intercooler connections (all tight), no cracks seen in either header, no signs of exhaust leaks from header to heads, and I’m at a loss why all of a sudden the car won’t go above 20 lbs when it just 23 lbs a few hours ago no problem.
 

gn87man

Member
You might want to check for leaks at the interface where the passenger side header meets the turbo flange. That is prone to exhaust leaks.

Sent from my SM-N950U using Tapatalk
 

Darkstar72

Active Member
You might want to check for leaks at the interface where the passenger side header meets the turbo flange. That is prone to exhaust leaks.

Sent from my SM-N950U using Tapatalk

I just checked it and those bolts had a little room left in them to go. Possible they got loose. If I get time perhaps I will take it out again tonight for a quick romp.

It comes up on the boost pretty strong it just hits 19 now and stops where just this morning it was well over 20. IDK.
 

87GNALKY

Active Member
If you have a power logger, look at waste gate open point on the graph. sounds like the waste gate is leting go at the same location (19#) every time. Also you wont need quite as much alky when the temps cool down like they are now. You could be loading it up a little too much is running alky..
 

Darkstar72

Active Member
Just got back. 2 quick blasts and still topped out at 19 psi. Perhaps in the spring I’ll get up on a lift to check the crossover.
 

Darkstar72

Active Member
If you have a power logger, look at waste gate open point on the graph. sounds like the waste gate is leting go at the same location (19#) every time. Also you wont need quite as much alky when the temps cool down like they are now. You could be loading it up a little too much is running alky..

I thought about that too that I fattened it up a bit too much. I guess when I decide to take it out again I’ll lower the gain on the alky.
 

Darkstar72

Active Member
Gauge or connection? Boost controlled by the solenoid? It seems odd its exactly 19 everytime.

I’m monitoring boost via the VDO gauge on the pillar. Boost controlled by an RJC manual boost controller.

I think 87GNALKY may be on to something with the loading up on alky. I did turn the gain knob up to 8 yesterday when I saw some KR and that was before I added a little more fuel through the chip this morning. It seems very likely it was something I’ve done versus the car getting goofy somewhere.
 

Darkstar72

Active Member
Well...still happening. Turned alky down from 8 to 6, no change, boost still topping out at 19 lbs. Trimmed some fuel out...no change, still 19 or so. Turned in the RJC manual boost controller...no help and I think it’s actually getting worse. No cracks seen in the headers at all. No obnoxious exhaust leak ticks that I can hear.

Is it possible the wastegate actuator is just worn out? IDK. Just looking for reasons why the car up to 2 weeks ago had no issue making 21 to 23 psi of boost and now can’t even get to 20 psi.
 

87GNALKY

Active Member
Check your gauge line for leak or possibly gauge itself
I'm kinda thinking that also. It says 19# but what does it feel like? If your exhaust valves suddenly stopped seating properly, that would explain why it is lower but at a consistent lower boost.. Do you think you could have floated the valves? That's like a way out there thought though... You could always do the leak down test to see but I would doubt you suddenly stopped seating valves.. If you had a Power logger hooked up you could look at where the waste gate is releasing.. Got a buddy with a power logger?
 

87GNALKY

Active Member
I am thinking of ways you can check your vac from your MAP sensor and the only thing I can think of at the moment is borrow another MAP or gauge from a buddy and see what it reads. Your gauge may just be out of calibration. I wish I was closer to IL, I would help you out with a power logger and boost gauge to test. I guess you could always remove the shrader valve from a tire pressure gauge and hook that up to the boost/Vac line but that's a really poor mans way of trying to measure Vac/Boost. I just would rather you do some low level testing rather than hurting something by getting a bunch of knock messing with the ALKY/Water mix.
 

Anthony P

sharing knowledge with those who care to listen
Hi Dennis, check your RJC boost controller. someone else recently had similar problem with their RJC unit. swapped to spare controller - that fixed problem.

check RJC brass 90* fitting. pinhole on side, in middle of flat part is supposed to be there to bleed off pressure. if pollen/dirt/etc is clogging that hole, can't bleed pressure so wastegate stays cracked thus not able to build higher boost. worth a check.
 

Darkstar72

Active Member
Just checked the gauge line. It’s tight and no cracks/tears. I think the gauge is accurate as it doesn’t feel like I’m pulling as hard when gauge was reading higher. I can still get it to spool up pretty quick but it’s just not getting where it used to.

Under advice from a friend I stuck a leaf blower up the tailpipe and sprayed down all my exhaust header connections at the welds and the turbo flange...no bubbles with soapy water.

Should I attempt to shorten the wastegate rod to see if boost comes back up? If a wastegate takes a dump what are the symptoms?
 

87GNALKY

Active Member
Just checked the gauge line. It’s tight and no cracks/tears. I think the gauge is accurate as it doesn’t feel like I’m pulling as hard when gauge was reading higher. I can still get it to spool up pretty quick but it’s just not getting where it used to.

Under advice from a friend I stuck a leaf blower up the tailpipe and sprayed down all my exhaust header connections at the welds and the turbo flange...no bubbles with soapy water.

Should I attempt to shorten the wastegate rod to see if boost comes back up? If a wastegate takes a dump what are the symptoms?
Shove a banana in your tailpipe. If it blows the banana out, you have boost.... I am kidding dude.... Dont do that........
 

87GNALKY

Active Member
If your using an external waist gate you can change the springs out if you have extras. If not, you could try and find another 8-10 # waist-gate spring to replace it with. I would bet that the waist gate gasket would be more likely to be the issue that a spring though. Have tried just using a new gasket/perm-atex on the waist-gate? Dont forget, if you use perm-atex, you need to let it set at least 24 hours or it will blow out.
 

Darkstar72

Active Member
Hi Dennis, check your RJC boost controller. someone else recently had similar problem with their RJC unit. swapped to spare controller - that fixed problem.

check RJC brass 90* fitting. pinhole on side, in middle of flat part is supposed to be there to bleed off pressure. if pollen/dirt/etc is clogging that hole, can't bleed pressure so wastegate stays cracked thus not able to build higher boost. worth a check.

It was definitely in the RJC boost controller. I took a pick and dug around in that hole because why the hell not. Then I took the top off to check the spring and ball...all looked in place. I also decided to add some Teflon tape on the threads and tightened all up.

Just got back from some test hits rolling in third...whacking 23 psi and staying there. O2 looking good around 780 and no knock.

The case of the missing boost is solved!!

Thank you everyone for helping me work through this one.
 
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