Boost keeps going up over time
 

I have had boost creep that would end at about 155kPa at 7K RPM.

Lately, the whole range has been getting higher, until now, it is at 155 at 5K RPM, and tonight, it crept to 175kPa at 6900 RPM.

Fortunately, there is still fuel, and I was at about 11.5 AFR. As suspected, there is not much fuel left. Judging by the 20* increase in AIT, there is not much air left either. My Overboost has been set (somewhat randomly) at 180. I think I'll drop it down to 175.

This is still waste gate only.

I was thinking that this was due to the colder weather, but tonight was 35*, which is higher than yesterday, and about what it has been often over the last few weeks.

In the morning, I will check for leak of the waste gate actuator. If it is solid, then I will turn the preload down about a mm.

Anything else I should suspect?

Screen Shot

Iwg? Where is your vacuum line coming from?

Internal waste gate. TD04. Line from compressor outlet.

Try running it from post throttle body and see what happens.

Try running it right before the throttle body: https://www.miataturbo.net/diy-turbo...eed-ebc-47532/

It is a leaking diaphragm. That is why it has been increasing I've time.

Do not do this. If you do, then the turbo will attempt to reach wastegate pressure at all times, including under part-throttle operation. You will lose the ability to effectively modulate the manifold pressure, and drive the compressor into an inefficient region of its map.




This is the most ideal location for the WG reference.




Quite probable.

Joe,

In general, I have boost creep, not droop, so the compressor outlet is fine and direct. To that end, I may try to find an actuator with more throw (the stock one is about 13mm), as, the way I built the downpipe, there is enough room to open the wastegate up to a full 90 degrees, but the existing throw only opens it about 40 degrees.

I'm saying that I know it is a leaking diaphragm, as I tested it this morning. If I had just waited until today, I would not have had to bother the forum with my question. And indeed, I agree, NEVER go post throttle body.

I will, this season, go to EWG control with the MS3 as it allows easy 2-level boost, and lower onset of torque (street car).

And, it was supposed to say, "increasing OVER time".

Any recommendations on a replacement actuator? I would prefer about 6psi WG only, with ability to EBC drive to 12-15 (maybe that range is not possible.

Thanks to all.

Anyone use one of these?

Kinugawa

I like the idea that it is a direct replacement, yet adjustable to some extent. I'll only have to add a hole due to my clocking the housings.

People used those, with decent results, so I dont see why not.

Btw: there is absolutely no reason whatsoever for the flapper to open 90*

At the 40 its at now, it is venting all it can so I wouldn't bother doing that.

Thanks. I'll order it. The funny thing is that the same guys always sell slightly cheaper through E-Bay, after shipping; so I'll likely go that way.

*EDIT* Verifying Vlads Btw. I wired gate fully open and went for a drive. At WOT, boost follows RPM and peaked at 156kPa, exactly where it did before when the waste gate was working properly, but opening the WG only the 40*.

I wired the WG open, but missed the power, so this afternoon, I reconnected it; and just managed my throttle.

Got home and the new WGA was here. BUT, they sent the wrong spring. Supposed to have been a 0.5 bar, but was 1.5 bar.

Looking forward to putting this on and seeing how it works. Then I can report back. I'll also get a pic or two when I have it open for spring replacement.

https://www.miataturbo.net/attachmen...1&d=1421462383

https://www.miataturbo.net/attachmen...1&d=1421462383