So I was driving last night and the issue I've been fighting with cropped up again, seems it makes itself more obvious during knighttime where temperatures drop (it was 62 ambient when this was occurring). Anyone know what this is? You can KIND of hear it in the audio but it's phone video, but watch the needle, I build boost, hit target, the car falls flat on it's face, dropping boost from say 15psi to 7, then starts building and repeats. If I get to a high enough RPM it stops happening (as shown at the end of the video), but this is very concerning. I did have it happen at about 8psi last night, but I didn't get a datalog of any of this as I was on my way to a friends house..



Someone I was talking to last night suggested shortening my BOV hose, and I hadn't touched the adjuster screw on the BOV since I put the thing on initially so I did. I unscrewed the thing until there was 6-7 threads and put it in, but I still don't get the typical BOV sound at anything above say, 7psi. I honestly don't know what this is.

-Compressor surge?
-BOV jacked up, causing me to blow my boost out of it? (it's the "go fast bits" bov that came with the FM2)
-A resonance caused by the high-flow cat I have? (suggested by someone last night - unlikely?)
-Fuel cut? The map has a maximum boost set at 22psi, I am not getting anywhere near that, max I saw while logging yesterday was 18.4psi. I was NOT having this during the daytime hours (mind you it was 12*f warmer)
-Spark blowout? I thought my Toyota COPs and NGK resistor-less at .04 fixed that..

I did get a datalog of this happening in another thread, car builds boost, "falls on face" happens and boost went from 14.1psi down to 7, then climbed to 9, 12, 14, fell on face, 9, 11, 14, repeat.

Lost...

 

First off, your friends are idiots.

Secondly, try upping your boost limit, you should be safe at 3.6 psi below your fuel cut, but it's free to try. I know with my MS it needs 1-2 psi extra. You could be getting more pressure in cooler temperatures.

 

sounds like missing of some sorts.

 

I'll try that, current "Maximum boost" is set to 22.5psi, I'll try 24.

Edit- That's what I'm guessing, I'm going to close gap further to .035 tonight and try to duplicate issue again.

 

Der as I have said many times before this is not compressor surge.

If it was spark blowout your boost wouldn't take a huge ****. Power would kinda crap out and your afrs would go rich or lean but that's it. No mega boost collapse.

Overboost cut with hydra feels like you've run out of gas for a split second. It feels horrible and yes, your boost will take a huge ****.

Note that the hydra logging is not necessarily high rez enough to detect how high your boost may spike. My logs show 24psi peak but my overboost cut has to be set to 25psi to not cut. That means I spike to 27psi because hydra cuts 3psi over.

 

Well that makes sense. Any idea why it would spike 18 on the logs and then settle to WG (roughly 14.1) or just above WG (15.4)? This MBC is no joke, it should be able to handle it..

 

It spikes because that's how the MBC rocks and rolls.

You have a cheap MBC right? Try this. Drill out the restrictor hole a tiny amount. By like 1 step up in drill bits. If it still spikes try another drill bit size up. Don't try to hard. Win FTW.

 

What's your boost source for the MBC?

 

Comes off the charge side of the turbo, it's a Grimmspeed MBC, something to the tune of 80 bucks iirc. My brace one's ball bearing had a flat spot (which answers why I was having issues..)

 

Well I just watched the video. that's not hydra overboost. Regarding surge, when I pass through certain RPMs at particular boost levels my turbo does make bizzare fluttering noises and boost gauge does the wobble dance- within a 2-3psi range though. Not 8psi.

Looks to me like some boost control issue. Maybe your BOV?

RE troubleshooting:

You can determine if it is the wastegate or not by disconnecting your wastegate signal line. Of course, only do part throttle to 15psi. IF no problemo there's some problem with your wastegate setup.

You could also do the same with the BOV by removing it and sealing the hole. Just don't snap off the throttle- ease off of it and your turbo will be fine.

I still think you should turn the **** on your MBC to hit 17psi and see what happens. Just glance at your realtime knock readout after you do a pull.

 

For whatever reason, the MBC seems to exacerbate the issue. I'm going to go upload my new map (with raised thresholds) to see if the issue is still present. Wish me luck <3

 

I am taking the MBC off and will try it right off the WGA tonight, I closed plugs to just over .035. Also removed some small jagged bigs off plugs 1 and 4, either material from ping or they were like that (causing the ping I was seeing on my map before). Regardless I'm getting an EFR and hydra 2.7 so an EBC will be the proper path anyway.

 

I had that same wobble, same boost signal. It's a turbulent signal. I'm not sure what's causing that down-up-down-up stepping of boost, but when I switched to a pre-throttle body boost signal it quieted down the over shoot quite a bit. The needle bouncing around like a blurr was solved by replacing greddy's crappy waste gate.

 

Yeah, I took the MBC off, and im operating off 14psi via WGA. I'm calling it good, and going to just hold off until Winter when I buy the EFR and get Hydra 2.7. I'll be using the (now working) EBC setup on the hydra and I'll have better gauges and all around superior setup.

Still kinda perplexed what this was, but I don't care to try to replicate it to find out else risk breaking something..

 

How big is the can on the wastegate, how long is the boost controller hose, and what is the internal diameter?

My WG did this when I had too small of a hose on it.

 

This is the WGA I bought. It works better then the one I had before, hose from turbo to MBC has an ID of 1/8" if I remember right, I'll have to double check. With the MBC taken out of the loop, I build boost to 14.1psi and holds it.

Boost controller to WGA hose was uncut, and was about 2'. Mostly so I could return this thing if it's too much of a hassle.