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.