barely building boost with ebay turbo
 

As the title says, i'm barely building any boost (no matter what i do with the MBC) with my 92 that has an ebay turbo with an internal wastegate. I've searched high and low for boost leaks and cant find any, although there is a slight hiss near the intake manifold. i can't remember if that hiss was always there or if it started around the same time as the boost drop. also it doesnt seem like a boost leak to me since it hits the same 18 in/hg of vacuum as before. i also haven't been able to spot any exhaust leaks before the turbo. i even changed the manifold to turbo gasket just to be safe, to no avail. there is no smoke from the tailpipe so i wonder... is my ebay turbo finally blown but the oil seals are ok? or is that not even possible?

EDIT: forgot to mention that the wastegate has two nipples on it. the upper one I can't blow into, the other blows right out by the rod with hardly any resistance. i can switch the vacuum line with my MBC on it from one to the other and it makes no difference whatsoever.

what turbo is it?

for the wastegate, you use the top nipple, leave the bottom open.

Do you have a leaking BOV or recirc valve?
Stationary checks wont work as you can not build boost without driving the car. (Or using anti-lag.)

its a t04e turbo. a/r 60

i've tried tightening the BOV already, no luck :(

wouldnt vacuum reading be different though? i guess i'll have to build a boost leak tester... I was trying to avoid that. :vash:

well it's not going to build boost on a 1.6L untill like 4.5K or above.

it hit full boost well before 5.5 before, now i barely hit 1-2 psi in first at redline and maybe 3 psi in second at redline.

Is your vacuum measurement after the throttle? If yes, it will not be affected. MAF Idle would be affected though.

bad coupler? bad turbo gasket?


what's full boost?

ahh good point!

i've checked all the couplers, none have any tears/holes, and all of the pipes are in their couplers fully. and i tried changing the manifold to turbo gasket just to be safe even though it didnt seem to be leaking.

full boost is about 7 psi.

Disconnect the MBC and run just WG.

lol wut?

probably should have, but I haven't tried this yet. i'll give it a shot after work on the way to lowes to get stuff for a boost leak tester. best case scenario is i dont end up having to make one.

What is the waste gate set as? Why are you using a MBC?

wastegate is 7 psi, i had bumped it up to 9 at one point but realized it was probably a bad idea and turned it down. it would have made more sense to just remove the MBC i know, but i wanted to have the option to turn it back up.

While you're still chasing ---- bypass it completely... Less parts, less stuff to narrow down.

i'll give it a shot. it wont make it any worse, that's for sure.

Are you sure that the waste gate is closed?

Did you have to clock the turbo to fit your car?

Have you moved the wastegate actuator?

So there are no unusual hissing noises when you try to build boost in higher gears? When my CHRA failed, there was no oil smoke, just a light metallic noise and no boost...but that's with a dual bb turbo, not a chinkacharger.

i havn't pulled the downpipe off to check, but I have moved the flapper with the rod disconnected and it moves freely. also i can pull the rod and it has plenty of resistance.

EDIT: now that i think about it, the rod was pulled out a little bit with the flapper as closed as it would go. i figured that was supposed to be like that for more tension on the flapper making sure it was closed. was i right with my assumption or is my wastegate most likely not closing all the way?

not that i can hear.

You should have to use compressed air on the actuator to move the rod out about 1/8 inch to get the rod on to the WG flapper. if you can just drop the rod and not have to fight it on, your too loose and the WG flapper is not fully closed.

I am running about that same turbo on my old Turbo Ranger...

really? my old rx7 TII wastegate i could move even easier and it built boost just fine.

Think about it, the WG is a door, if not fully closed, it leaks

Maybe you had a diffrent style of actuator that pulled the rod tight. IDK

I know I had a no boost problem once, and the rod was not pulling the WG tight to seal.

Clocked the turbo a bit to put some tention on the rod, therefor the WG... boosted great after that.

its got a good amount of tension on it, but not enough that i cant pull it by hand with some effort.

Can you blow a small amount of compressed air in one the nipples and see the rod move?

When you install the rod on the WG lever pin, to you tug on it some to get it to go on the lever pin?

It should take a bit of effort to get the rod on.

How old is the turbo?
Has it been abused?

I wonder if the WG hole has cracked badly and even with the flapper fully shut, exhaust gasses are getting around it

You'd pretty much have to lose the flapper to see almost no boost - a crack wouldn't do it. Also, it doesn't matter if the MBC is on there, if you're not building enough boost to open the wastegate, you could run the MBC fully closed or fully open and it wouldn't make a difference. Better idea: disconnect the signal line from the wastegate actuator altogether to see if you can build boost that way.

Make or buy a boost leak tester

WG flapper leak or boost leak. You have one of these problems.

well i disconnected the mbc which made no difference. also i pulled the downpipe off and the flapper does appear to be closing fully. i'm planning to build a boost leak tester tonight.

This.

Otherwise you're just going to keep grabbing at straws. Plus, you'll now have it on hand for the future if you ever run in to problems again.

I literally just went through this. Flapper door seemed to work fine. 2-3 psi with wastegate vac hose disconnected.

The rod had moved out of position on wastegate. Once dp was removed. I instantly seen it. I tapped it lightly with a hammer back into place. Never had a problem again.

Intake manifold shouldn't have any hisses. Find your leak.

mbc mounting bracket is ingenious. +1.

:brain:

I think that is about the best way to mount a MBC, It is very responsive that way.

All you do is remove the hose barb and replace with a pipe nipple (1/8 npt)

The trick is you have to shave a few threads off the nipple on the end that screws into the MBC, or you will not be able to get any adjustment from the spring.

it's ingenious except it keeps you stuck with the worst possible place to take a boost reference for a MBC...


that said, i still like it if you don't mind the boost taper towards redline. ;-)

what do you mean it moved out of position? when i pulled my dp off, everything looked to be alright.

Why is it the worst place for a MBC?

It is set at 22psi, no boost creep or taper.

it's taking a pressure reference from the source, not from where the charged air enters the engine.

if you have something like an IC in the path between the compressor outlet and the intake manifold, the amount of restriction that item represents becomes greater as the airflow increases. It's a non linear relationship.

The way to think about it is with a narrow drinking straw. if you blow through it lightly, it seems to present no restriction. However, the harder you blow, the more of a restriction it becomes.

We have a thread about it somewhere. I'll find and update this post.

EDIT: here we are. https://www.miataturbo.net/diy-turbo-discussion-14/boost-sag-no-you-dont-need-ebc-47532/

i still prefer sourcing boost from after the IC, but props nonetheless.

that was the core intention of my post, as well, i just was less direct about it

I read that thread, Very intresting style of writing in it.

The logic in it sound, but I have never noticed boost taper towards redline.
I hold boost of 22psi from 2500 thu 6k

Ill have to check a few other turbo rides and see there set up and see if they get the taper.

This is the first board I have been on to speak of taper and not creep.

this can still be done with a similar setup as that one you like:

https://www.miataturbo.net/attachmen...ine=1333749988

I worry a little bit about the weight bouncing around, since there's a total of one thread in that thin IC pipe, so we'll see if it lasts. Abe might get another $20 of mine.

What about 6k thu redline?

lol i was about to say the same :bigtu:

FWIW I've sourced my MBC both Pre and Post Intercooler and it made virtually no difference, other slight boost spikes put right before the TB. This is with my custom ETS intercooler. Throw a super restrictive intercooler on there and that changes it all I'm sure- boost taper up top. Just depends on the situation/setup.

Redline on a stock Ford 2.3 SOHC is 6250 RPM......After this the factory ECU cuts spark.

The hinge that the flapper is attached to, had slid up about 4 mm, and the door would not completely shut. I looked at the outside of housing and seen where a small tack weld had came apart. That weld held the guide for the shaft. I tapped it down untill they matched. It worked perfect again.

Long story short, my gate door was not closing completely.

I would find hiss on intake #1........ Hint while at idle spray all vaccum connections with starter fuid, if a leak it will suck it in and idle up...

If once fixed, it still doesnt build boost..I would take complete intercooler system off and inspect for silicon coupler leaks, or holes in intercooler.

I had to do that once. I had a hole in a spot not visible.

Hope this helps.


PS: Hows shaft play? And how does the compressor wheel look? Any chipping?

its got a little shaft play, but not too bad. no chips on the compressor or turbine wheels that i could see. last night i did a test though... i hooked my boost gauge up before the throttle body to see if it built more boost when i left off the throttle. well right before the BOV opened, it showed about 10psi for a quick second. so that leads me to believe that i definitely have a boost leak and it is after the TB. i'll have to pick up some starter fluid tomorrow after i get paid... i could use electronic parts cleaner or brake cleaner to do the same thing right? i'm broke, don't get paid until tomorrow and have both of those but not starting fluid. although work might let me steal a few squirts of starting fluid... hmmmm

Brake clean will work no prob. Watch your eyes for spray tho.

i thought so. i'll try this during my lunch break.

well i sprayed it a bunch of places and it made no difference whatsoever... except when i sprayed it inside the BOV. unfortunately, i had to tighten down the BOV stud so far to keep it from leaking, that i can't tighten it down anymore. i'm still not building boost though, so i think my BOV is broken somehow. I'm going to tear it down tonight and see what i can figure out. I've got another identical BOV that my roommate took apart and never put back together that i can steal parts from if necessary.

it's pretty obvious when boost is leaking out something like the bov, you'll hear the whoosh.

well it might not be leaking from there anymore, but it definately was before because i could put my hand over it and feel slight vacuum pulling on it along with the idle going up. there were barely enough threads to get it to stop leaking, that's why i think its getting pushed open by the boost pressure.

so for an update, i've changed the BOV, and it is no longer leaking from there. I cannot find another leak anywhere. I've sprayed brake parts cleaner everywhere i can think of that vacuum could get to. Every coupler, all the vacuum fittings. Most of the vacuum lines are brand new. I have discovered though, that my turbo seals are leaking.

are there any vacuum ports/hoses that aren't easily visible that i might have missed/not know about? i've checked the one on the back of the manifold already.

Is there any way to build boost sooner? I had someone who owned a miata with a similar greddy turbo setup drive my car and he said I have an exhaust or boost leak because the boost wasn't building until 4.5k-5k. I was going to run a boost leak test this weekend but now I am just flat out confused.

Can I modify my tune in megasquirt so that it will build maximum boost as quickly as possible?

It's not really a tuning issue. You might be able to tweak it a bit so you get the most out of what boost you can build at lower rpms, but you can't physically build boost sooner by tuning.

You need to have a turbo it good condition, a free flowing downpipe, a free flowing exhaust, a good seal between the head, manifold, turbo, and downpipe, and a good wastegate system.

For the wastegate, use a boost source location directly in front of the throttle body, use a good manual boost controller, make sure you have a good wastegate.

Remember the stock greddy wastegate sucks, if you haven't replaced it, make that your first priority.

I appreciate it. What makes the greddy so poor for performance? And do you have any recommendations for upgrades?

Not really sure. It's a genuine Garrett turbo (no, mitsubishi?) and it's great, but the wastegate has always been the suck.

Search "helper springs" for a laugh. They were so bad, they needed help getting open. My own personal experience was a boost needle bouncing so bad I couldn't see it.

I skipped the helper spring and went right for a new wastegate. You're going to have to do your own research on that one, as it's been a while since I upgraded. Take a few measurements of your current one and start searching the internet. Try SR20 wastegates, they have a ~5.75" arm. Check my build thread for a great suggestion on brackets, just remember that flat brackets DON'T work.