Overboosting. Any ideas?
 

Background: '99 running FM2, Hydra, 2.5in FM exhaust with cat deleted, still sourcing the wastegate can signal/pressure line from turbo cold side housing, running FM's new 8psi wastegate can and bracket, turbo's hot side is ported about half as much as the Begi photos. Car is in need of tune but drives fine ish.

So here's the story. Car hits 8psi like it should, then creeps a hair to 10psi ish at 5k rpm, then just keeps building. At 5500- 5800rpm it gets high enough to hit the Hydra's 15psi boost cut and shut the car down for a sec till I let off. Really tired of not being able to drive the car like it should be. Car hasn't been driven much due to unrelated issues. No manual/electronic boost control, just the boost signal from the turbo to the wastegate can. I've checked that the flapper moves its full range. Swapped the can with an old one and still does it. Only running FM's base map at the moment. Thought it might be ignition timing related. So messed with base timing. Down a few degrees still does it. Up and the car is ....more fun.....but still does it. Though maybe timing could be forcing turbo spool like an unwanted anti lag. :noob: I could handle 1-2 psi of creep in cold weather but this is crazy.

Any idea's? Searched the forum but can't find anything. A little about creep here and there but nothing that seems to be on this level.

Try changing your boost signal from the turbo->wastegate to directly pre throttle body->wastegate

Ok how would this help? Not saying it won't, so no disrespect. I've heard this is good for when the boost drops at higher rpm due to intercooler pressure loss. Just in my head, if I tap my pipe to source signal just before throttle body wouldn't there be in theory less pressure to push the wastegate open? I know there will be enough to do it. It's just I have more boost than I want, not that it's dropping off.

Other question is: My intercooler piping is all FM silicone pipes. Only hard piece is the BOV/intake sensor piece. For this idea that cool? It's only 8in from the throttle. Better to tap in just before BOV or just after? Also If I do try this the pipe is aluminum or stainless is a Lowes brass fitting ok for a long term thing or go crazy and find someone to weld?

what happens when you disconnect the actuator altogether? Just keep the flapper wide open and do a pull. If it still does it then you need to port the shit out of that turbo or go ewg

^ is my next move, it just got cold out and the turbo was still hot from the last test run. A lot of people have an FM2 or similar. I can't imagine this being a need for EWG. Nothing in my setup is odd or crazy custom. Calling FM tomorrow, but looking for ideas.

What's the downpipe look like? Wastegate flapper getting hung up on something?

+1 to a pull with the flapper unhooked.

FM cast outlet/downpipe. I can move the flapper through full sweep with it unhooked. I do have a small leak at the downpipe to exhaust gasket. I do mean little, just a small burble at idle. New gasket on the way.

Turbulence fail.

if anything the turbulance will cause him to make less boost up top, not more.

I discovered my DP studs stretched in Arkansas a few years ago when the car suddenly overboosted to the 18psi limit.

I'll hurry up and get my gasket here. I trust Hustler's input. I do agree that a "turbulence" would do the opposite, but I've had more bizarre stuff happen in the past with other cars go wrong that made less sense. Wasn't driving the car much, just got it going again, had a few exhaust backfires happen that blew the gasket out, and now this is a way more noticable problem then I remember. So unless a small bang of fuel in the exhaust suddenly made my turbo work way better than it did before, it's worth a shot for a couple dollar gasket. Need fixed anyway.

One idea that's being discussed as an idea is my deleting the cat making the exhaust to0 free flowing. 1: did the delete in august I think, didn't do this the little I drove it then. 2:I could maybe see a little creep but not 15psi at 5500rpm on a 8psi wastegate can.

That would not surprise me. I could not make less than 16psi in my car with 3" exhaust with the old BEGi set-up.

^ This. You are running almost the exact setup I was on my 95 and I couldn't get it under control. I had a full FM2 kit with their 3" dp to a 3" exhaust with just one magnaflow muffler. I sent my turbo to Blouch for porting but that still didn't solve it. I was hitting 17psi by redline. When I called FM, they told me to add a cat/muffler... EWG is the ultimate answer IMHO.

Send your turbine housing to BEGi and have them port the wastegate.

I had the same problem with my FM2 setup, took it to a machine shop and had them port it a little bit, didn't even help the problem at all.

Called BEGi up, Steph had me send the turbine housing in, they ported it.

I got the turbine housing back, installed it, problem completely gone. Now holds solid at whatever I want it to - no overboost whatsoever. They did an INSANELY better job at porting it than the previous machinist hat.

So just got done earlier checking the timing belt. All was well, one more thing down for ideas on what could cause this. Timing tensioner was a little loose. Well... the belt was. Just cracked the tensioner blot loose let the spring pull it in a hair then tightened. Talked to FM and long story short was recommended to put a restrictor in the exhaust if all checked out well. Thinking along the lines of a gasket replacement with a 2 1/4in hole. I'll cut some aluminum tomorrow and see if it helps. Maybe try a 2in hole and another with a 2.25in hole. I'm hunting for couch change for fun money broke at the moment so needs to be an easy fix/cheap. No monies for a cat to be put in.

Just seems counter productive to put IN a restriction. Just goes against the grain to un-make something better.

so did you disconnect the wga and try it?

+1. Putting a restriction in defeats the purpose entirely.

Disconnecting the WGA is going to be this afternoon. Have left over spine problems from the military and can only bend over around the hood so long. I work better on my back :giggle: Figure I'll do a disconnected pull this afternoon and if that doesn't give me ideas on the problem then shoving a restrictor in he exhaust is probably my last idea.

Just for a ballpark, a disconnect WGA run should only net maybe 4psi max at redline? Obviously if I still hit 15psi cut without the can connected I'm Fing lost.
Then it's a housing port at begi.

forget the restrictor idea. its overcomplicated and completely unneccessary. retarded if you ask me. whats the point in choking up the motor and killing power just to keep pressure in check?

disconnect wga, do pull, if you still overboost you need porting or ewg. the end

True ^. I'm only looking at doing a restrictor plate cut out of scrap aluminum bolted in as a temp gasket at downpipe to exhaust flange. Figure if a little restriction cures the issue then it is WG porting time. No funds for EWG.

Read- https://www.miataturbo.net/showthrea...ht=boost+creep

Disconnect the damn flapper. Know this- when the wastegate opens the flappen, the range it opens is not as much as you would think. I used a small air compressor to actuate the assembly and was surprised how little it moved. Also, exhaust gas takes the path of least resistance. If it's easy to get through the turbine, it won't want to go through the wastegate.

^Thanks. That thread describes what is going on with mine to the T. Even just had the CHRA rebuilt recently. Just called Begi and they'll be getting my housing after the new year. Still going to do a wastegate wired open pull, later tho, my back is killing me. Just for funsies.

On a note: It seems like a ton of people need to port the turbine side. Why not just cast this in from the get go? I know I'm pissing in the wind. Just needed to say it, no need to flame me.

I tried putting a simple restrictor plate in the exhaust system as a temporary solution. Not only did it NOT fix the boost creep problem, but it also significantly increased the boost threshold.

Effectively, my boost came on later, and still creeped to boost cut well before redline.

You really have 2 options, as far as I can tell:
1. Send turbine housing to BEGi and have them port it for the cost of shipping.
2. Buy an EWG setup.

Edit:
Shit, you beat me by 5 minutes

It seems Corky contacted Garrett about the problem to ask them to change the casting, and Garrett basically told him,

"We've never experienced the problem before, you are obviously doing something wrong"

Apparently, we're running a much more efficient setup than garrett has ever experienced...

Begi is only charging me the hour of labor. So for less than $100 it should be fixed. An I agree a exhaust restriction is a bad idea.

Dopp: thanks for the link For some reason didn't come up in my searchs

It is now.
Look at Borgwarner EFR turbo line.

Haha yeah. If I had the money in a heart beat. Need to rebuild the motor soon. Actually what I'm trying to do is make sure everything works right while I save up funds for the motor. No point on putting in a built motor attached to non working parts. Then it's wheels and a call to ARTech. Unless I find wheels for cheap. '97 has a pair of slightly tweaked ugly ones and the '99 has the ugliest 16's ever made that came with the car. Waiting for 949's new style to come out.

Look closelys. It's almost as if someone at BW put some actual thought into the IWG design. :giggle:

Note the angle of the wastegate port and the cavity behind the flapper - the cavity is of particular interest, since the flow off the turbine wheel should create a significant low-pressure zone to promote wastegate flow.

https://www.miataturbo.net/attachmen...ine=1324522040

Here's a less sexy photo of the WG inlet:

https://www.miataturbo.net/attachmen...ine=1324522040

For comparison's sake, here's my old ported 2554R with a much, much sharper transition into the wastegate:

https://www.miataturbo.net/attachmen...ine=1324522040

Can't resist, this pic is too sexy. Our new product photo guy is phenomenal.

https://www.miataturbo.net/attachmen...ine=1324522216

Does this mean we all need to start saving up for a group buy....

No group buy - they will definitely go into production. We may offer a small discount for certain early adopters with certain cars, though.

They'll be priced competitively, but our goal isn't to compete on price - our kit will be a big departure from the status-quo in lots of ways.

No problem Sir.

The hotside I got back from BEGi had a much deeper channel cut into it, interesting. Did that posting fix any issue you were having before, Sav?

Very simple and common issue. Boost creep happens when the wastegate doesn't flow enough which is made worse when your DP back has very low back pressure. Most internal wastegates would creep if you were to run an open turbo blowing hot air on the fire wall (don't try this at home - only mentioned for perspective). Adding backpressure like a restriction or cat as a means to control creep makes as little sense as putting in a smaller turbo that flows less as a means to control creep.

Apples to oranges, but I finally got my 16g upgraded MSM turbo to stay somewhat under control by putting in a wastegate can with a longer throw. The stock can would only crack the wastegate a small amount. I found a can that would swing the flapper open until it hit the back wall of the DP and it helped. Pressurize the WG can with the turbo off the car if you can and observe what the flapper is doing. Don't forget to check how the inside of the DP might be inhibiting the opening. If none of that helps, build the engine, tune to 20psi and hold on!

I guess for others and their searches I should call this issue fixed for now. I wound up porting the turbo. I only had a couple drives with it together before I found out the 2 middle cylinders are F---ed. I will admit I didn't go rape it to truly test the boost stability, however what romping on it I did do it held the pressure I had set it at. Well actually I was messing with a new MBC so don't "know" what I set it at, but it would hit 8psi on wastegate can only and stay there. Couple clicks on the MBC and it would hold 9psi, then clicks and 10psi. So as far as I can tell porting the hot side fixed my issue.