MBC is maxed out.

[phunny]

Got my car tuned today and after we got it all dialed in I went to turn up the boost. SUPRISE, it was all the way in.... I understand there is a mod to put washers on the WG but I'm not sure where exactly they go. Anyone have any pictures or could really explain exactly where they go. Thanks guys

Charlie

 

[T9S1i]

what kind of WG are you running? Internal or external?
What kind of MBC?

 

[VTEC_THIS]

If it's a ball and spring mbc, you can put a stiffer spring in and it will hold more boost.

 

[JusMX141]

If it's all the way in, there's no air making it through the MBC anyways. Putting a stiffer spring in it will do nothing.

The problem is that the flapper is blowing open because the actuator doesn't have enough spring tension to hold it shut. You can try to shim the actuator by adding a couple washers between the compressor housing and the actuator's mounting tabs, but it may only get you a couple psi.


Recently we ran into an issue on my buddy's car when trying to achieve anything over 18psi. The car has a 34mm internally-gated FP Green and we were using a T25 actuator (the turbo had a welded flapper when I got it, be he wanted to go internal and the T25 actuator was the only one I had that would fit properly.)

Anytime we tried to boost past 18psi, the flapper would blow open. The car has an external dump for the wastegate chamber, so we could hear when the wastegate would open....no hiding that. I began shimming the gate tighter and tighter and we were getting the same results. We were down to 1/4" of arm travel, and I had the boost source going to the actuator completely disconnected- same result. I ended up getting a universal AGP actuator with a much stronger spring and an adjustable arm and manufacturing a bracket to hold the actuator head.

The first time out with the new actuator the car made 28psi....I had far too much preload on the actuator arm. Plently of tuning later, we've found a sweet spot between the actuator having enough spring strength to hold the flapper shut and just enough preload that there isn't a huge spike in boost. The boost now spikes to 23-24psi before settling at 22 and holding it rock-steady to redline.

 

[Black_Bullet]

Ive shimmed my w.g. with 1 washer on each of the two actuator bolts.
Helped the car spool up faster and gave only like 1 more psi.
I didnt want to do anymore shims because then it wouldve gotten uncontrollable with spikes and possibly premature wear...

I see about 24psi falling and holding 21 redline right now on my e316g.
In the upper gears ( 4th & 5th ) especially in colder weather, I get 25psi spikes which I dont care for too much
but there manageable. Anything more than that and the 16g is just blowing super hot air fudging the tune up.

You can try that, but preferably I just suggest you get a tubular o2 housing with like a 38mm external gate on it and running the stiffest spring you feel comfortable running. ( Stiffer the spring the higher your lowest boost will go. The closer your lowest boost to your actual desired boost, the better boost control and holding.)

 

[phunny]

I have an internal gated evoIII. Halman boost controller. 16.5-17 is max I can run....

 

[T9S1i]

did you check for boost leaks? Or leaks in the lines to and from the MBC?

 

[blcknspo0ln]

Do you have the hallman ES? Either way, did you ever take the MBC apart by any chance? I say this because I temporarily had the same issue when I took apart the MBC and put the plunger in the wrong way (all it does is acts as a middle from the tightening screw and the spring) and I wasn't getting enough spring pressure to run over 22 psi. I switched that little plunger around (literally gave the spring only another 1/3" of play) and now I have my good boost control back.

IMO, I'll for once disagree with justin on this because I have never seen a 16G fail to hold 18+psi. If it's an MHI 16G, the WG arm is non adjustable, so the wg tension should be the same. Of course, oem failure is always a possibility, but I doubt it. I would look for something in the system that is not hooked up correctly. Sounds dumb, but make sure the boost controller is not hooked up backwards. The line perpendicular to the MBC body is the one that goes into the wastegate.

 

[T9S1i]

when i hooked my mbc up backwards, my boost shot up to 25+ psi, it didnt have trouble boosting at all.


Here is something to look into.
Sometimes the pivot arm that goes inside the turbine housing inbetween the wg flapper and the part where the WG rod connects to the flapper outside of the turbine housing kind of "walks" out of the housing, thus causing a bad angle for the flapper door, and it kind of stays open.

See if this part is sticking out more than 1-2 mm and if it is kind of tap it with the side of a hammer and it will go back in.

I noticed slow spool up before and this was the culprit. It was an OLD 16g though.


Also, you could always try to put some washers inbetween where the internal gate bolts to the comp housing to give more load on the wg flapper and arm.

 

[blcknspo0ln]

I swear, I bet we're all looking waaaaaaay too deep into this problem.

when i hooked my mbc up backwards, my boost shot up to 25+ psi, it didnt have trouble boosting at all.

It makes a lot of sense anyway, since the boost source would be going nowhere into the boost controller, therefore the wastegate would never open. It's too late in the night to start contemplating theory, but I literally *intentionally* ran my MBC backwards yesterday and I got wastegate pressure (1.5bar). crazy I tell ya!

 

[T9S1i]

hmmm, it could be they are different types of mbc's. Im running a SBR cheapo ball/spring mbc. Works like a charm after i had nothing but troubles with my turboxs dual stage left over from my FWD.

 

[Black_Bullet]

Is there any discrepancies between the bleeder style mbcs and the non bleeder ball and spring mbcs.
( or are they all bleeder? )

I have a old joe p mbc with a bleeder hole, and it bleeds way too much air.
If I boost leak test with it on thats all you hear ( leaking tb shaft seals too). My boost seems to always fall back to 20-21psi no matter how far down I tighten the mbc. Before I shimmed the actuator it used to hold even less, and the Gm maft/ blow thru seemed to free up a little bit more air also but I know its got more in it.
I can spike 25-26 and still only have max of 21 at 7k though. I dont have 34mm flapper btw.

With these cams etc. I know im running up towards the choke point of the e316g, but
the other day I plugged the bleed hole and I got 22-23psi at redline and pulled way harder, but it just made the intial spike harsher ( 27ish.) I hear its not good to block the bleed hole anyways on that style mbc since it can lock up pressure in the line and cause sporadic behavior. Different gears, temps also alters set boost, its pretty annoying to dial a real tune in on it. Id like to get this thing set at 25psi rock solid every gear with boost dropping off no lower than 22psi at 7k.

Hope this is still of any kind of relevance to OP's question, but basically iam looking for ways to get more boost without having to run with no waste gate line ( yea right. ) I was thinking going external with a really stiff spring to keep the set boost as close to minimum boost as possible instead of jumping from stock w.g. pressure of like 11 psi and trying to make a mbc more than double that amount.

OP, the shimming did work for me, you should give it a shot in increasing your boost; just becareful doing it.
Check for boost leaks, that will limit boosting, and make sure your MBC ( if it has a bleeder hole ) isnt actually bleeding too much air out or its considered a boost leak imo.

 

[Black_Bullet]

hmmm, it could be they are different types of mbc's. Im running a SBR cheapo ball/spring mbc. Works like a charm after i had nothing but troubles with my turboxs dual stage left over from my FWD.

Does that SBR mbc cause any spikes/ boost drop off issues. Is it a bleeder style?
I had a friend who used to run one and he never had any problems with spike with a 14b interal gated setup;
but that could be a different story.

 

[JusMX141]

Despite what our actuators are capable of, I'm positive that once you reach a certain boost level, even a 31mm wastegate flapper becomes difficult to hold shut.

For example, look at this giant 19cm Holset HX40 housing. This is a twin-scroll housing that is designed for use on Volvo trucks and supports 35-40psi:

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The flapper is about the size of a quarter, and the wastegate hole itself is barely big enough to fit your pointer finger into; yet this is all that's needed to regulate boost on such a large application.

Once the air pressure reaches a certain threshold, it needs far less of a space in which to escape. Even if the flapper only opens 1/4", it's still enough for 35psi to blast it's way past the turbine wheel. Now 15psi, on the other hand, would need far less of a restriction to exit through the wastegate rather than continue through the turbine housing. In steps 34mm and 38mm flappers with massive wastegate holes underneath.

 

[phunny]

I just did a boost leak test, everything was fine. I found out I do have the bleeder type mbc. I'm shimming the wg now and see what that does.

P.S. the mbc is hooked up right.

 

[H82lose91]

Port the turbine housing so it doesnt promote flow to the wastegate passage. I went from 19psi at redline with my MBC all the way in to holding 21psi to redline with just some porting. I added to 1/8" thick shims under the WGA and its now holding 23.5 psi to redline. If you do this toye of porting dont expect to run 14psi and not see creep. Also having the larger flapper doesnt help in these situations. This a E316g btw.

 

[phunny]

Got everything back together and went for a short drive. Holding 18lbs steady now. Was hoping for more, seeing that everyone else with an evo3 can boost over 21lbs

 

[Black_Bullet]

Port the turbine housing so it doesnt promote flow to the wastegate passage. I went from 19psi at redline with my MBC all the way in to holding 21psi to redline with just some porting. I added to 1/8" thick shims under the WGA and its now holding 23.5 psi to redline. If you do this toye of porting dont expect to run 14psi and not see creep. Also having the larger flapper doesnt help in these situations. This a E316g btw.

23 to redline is not bad, Im having trouble getting mines to do that, but I have some minor boost leaks though.
Do you have cams, stock intake manifold? Does it spike really high first?

 

[H82lose91]

Right now its spiking 29psi and holding 23psi. Boost controller even with the new spring is only adjusting the spike. The 1/8" shims are what bumped things up. As a datapoint, before these mods i had 12mm nuts under the WGA and it would spike 30psi and hold 24psi to 7k. So im about at that same point without having to shim the crap out of the WGA so the port work is doing allot.

Motor is a 9:1 wiseco eagle setup, GSC S2's, Stock intake, mild ported head with 1mm over valves. Car went 12.07@115 on pump/meth with modded sidemount last week. Hitting the dyno tomorrow then tossing on the new intake manifold.

 

[Black_Bullet]

Right now its spiking 29psi and holding 23psi. Boost controller even with the new spring is only adjusting the spike. The 1/8" shims are what bumped things up. As a datapoint, before these mods i had 12mm nuts under the WGA and it would spike 30psi and hold 24psi to 7k. So im about at that same point without having to shim the crap out of the WGA so the port work is doing allot.

Motor is a 9:1 wiseco eagle setup, GSC S2's, Stock intake, mild ported head with 1mm over valves. Car went 12.07@115 on pump/meth with modded sidemount last week. Hitting the dyno tomorrow then tossing on the new intake manifold.

You will probably get some large gains with adding a decent fmic on there.
That 16g is throwing a ton of heat into the intake tract with those spikes.
I am limited to straight 93 octane so my tune becomes jello with anything over 25psi.
Sounds like your cars making some decent power though, with a little bit of better driving you should be able to do 11.9-11.8 with that trap speed... Ask me how I know.

 

[H82lose91]

With the Meth the intercooler isnt holding it back too much. Although i do have an EVO FMIC on the way for it. Dyno'd it today with no changes slip is in my profile. New intake is on already and will hitting the dyno again next week i hope.

 

[Black_Bullet]

Op have you thought about using a tighter waste gate actuator instead of the stocker with shims.
I think theres like a HRC actuator that is 17psi spring or something.

 

[phunny]

Op have you thought about using a tighter waste gate actuator instead of the stocker with shims.
I think theres like a HRC actuator that is 17psi spring or something.

I didn't know that was an option. I'll look into that, thanks.