Compressor Surge or Faulty Wastegate actuator?

Hi All,

Needing some help please.

I have just had my 2nd engineering brake test today and its fail.

Nothing to with the brakes on the car the car just could not perform well enough to actually do all the brake tests.

Basically the car is hooting, jerking and what sounds to me like surging upon boost.
Car will not accelerate normally when driving but not all the time sometimes its fine.

Free reving the motor out of gear and stationary is fine and i can push the car up to 5000-6000rpm no problem.

It only happens when its actual load driving and its intermittent.
During the test today there were times I could get the car upto speed quick rowing the gears and all was normal then there were times it would buck and jerk and hoot.

Knock of 9 counts normally resulted from this. I data logged this thoughout the brake test.
Once the car started knocking the only way to stop it was to turn the car off and wait for the ecu to click off.

Datalogs showing the fuel pump is switching off intermittently? Should that happen?

Here are details of the setup. Its a 3s 6g72 motor in another mitsubishi (be open minded please)

Chrome ECU v2
Stock 9b turbos
3SX hard intake pipes
tactrix 3 port boost solenoid
EVO BOV metal one (evo 8/9 one i think?)
K&N oval pod filter
Montero MAF (scaled in Chrome)
NGK copper plugs (heat range 6)
Stock injectors
Walbro 255 pump


Some of the troubleshooting that was done by the engineer and myself was to bypass the tactrix 3 port and just feed directly to the wastegate (wastegate spring pressure only)
We also bypassed the EVO Bypass valve.

Here is a video of the car. Early part of the video you can here the hooting sound.

https://youtu.be/X8dA54qTKCI

Also attached is a datalog of the car. Yes the AFR is quite rich.

Thanks guys

Running too rich will literally foul the plugs to the point where the motor stumbles. Just a quick thought.

I totally agree with you however this particular issue has been sort of an ongoing one and bucking and jerking occurred also when the car was running alot leaner. 13-14:1 AFR upon accel.

The first time this jerking/bucking happened was last year and a lot of troubleshooting.
At the time I was using quad tip bosch platinum spark plugs which i found later were not suitable plugs for the motor.

I swapped them and instantly found knock counts were gone and the car was alot happier.
I thought i had sorted this issue however not ever really able to test the actual driving of the car as the car is not allowed to be public road driven until engineering test completed.
(Dyno time is possible however no places local to me want me to hire the Dyno without them tuning it and few places want to touch the Chrome ECU despite it being factory like an EVO ecu)

I think its compressor surge as the car is hooting like mad and the datalogs show low airflow at the point of the hooting.

The motor is not able to ingest the boost?
The turbos are stalling?
Can this be a result of my FMIC being too small?

I pulled the wastegate actuators and pressure tested them.
Both hold upto 7-8lbs ok so i dont think they are any cause.

I am hoping someone can suggest some other things to check or test.

Anyway i have attached a youtube video of the car running on jack stands through the gears. You can hear the hooting sound when partial throttle open really clearly.
Its loudest heard at the K&N oval filter

https://youtu.be/a_mQnJ0eEQA

How do you have the BOV plumbed in? I had VERY weird issues like this when I didn't have the BOV diverter in the intake boot thingy. I assume the BOV is plumbed in the correct direction too?

I have the EVO BOV plumbed into pressurized intake hard pipe that goes to the throttle.
The BOV is recirulated back into the bottom of the turbo intake bubble. BOV is connected the right way around. Double and triple checked that.

Photo below should be able to see the BOV plumbed between intake pipe to throttle and the pre turbo intake bubble

Not sure what you mean by diverter in the intake boot? Something that'd part of the turbo intake bubble?

We disconnected the BOV and blocked the port for the BOV on the intake pipe during troubleshooting of the issue at the brake test. Same hooting, bucking and jerking upon throttle and boost (2500-3500rpm).

Attachment 9024

Older photo but same setup really
Attachment 9025

Do you need to have boost to perform the brake test?, easiest way for now would be to open both wastegate flappers so it's drivable then do the brake test?.

Sounds like compressor surge but you'll have to post pictures of all pipng and setup to get a good idea on your system.

Single fmic with altered charge pipes could cause this issue..

Don't need to have boost to do brake test.
Car just needs to be able to get to speed in a reasonable amount of time and do so smoothly.
So to open wastegate flappers just disconnect the actuator arm from the lever so its open always?

I will add some more photos of the separate components as I pulled the turbo intake pipes off yesterday and checked the turbos and wastegate actuators for damage. No damage. Actuators holding pressure to 7-8lbs

A suggestion was made on facebook that I could add a resonator box to the intake system (after the MAF) and that when compressor started surging/stalling that this trapped/reversing air goes into the resonator box first so that the air does not screw with the MAF sensor signals.
Anyone have experience with trying that?

There's a diverter in the intake boot that's a y-shaped piece of plastic. You can see the shiny bit here:
http://www.3sx.com/store/catalog/bov...ch-04-400l.jpg

If the BOV opens then the air dumps right back into the MAF and makes the car run like complete crap. Similar to your facebook suggestion, air stalling the MAF is really bad.

Yeah I have that hard plastic diverter in the intake bubble for the air venting from the BOV.

Would be so good if it was simply just that!

Quote:

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Originally Posted by DocWalt

There's a diverter in the intake boot that's a y-shaped piece of plastic. You can see the shiny bit here:
http://www.3sx.com/store/catalog/bov...ch-04-400l.jpg

If the BOV opens then the air dumps right back into the MAF and makes the car run like complete crap. Similar to your facebook suggestion, air stalling the MAF is really bad.

---

I've been searching around and am wondering if anyone knows where and if I could find the device that Eric (aka kywhitelightning) had made that he used to cure turbo cruise surge.

http://www.3sgto.org/threads/13541-G...A-complete-kit


I think its something that could work.
My surging occurs typically upon light acceleration 2500-3500rpm at 20-30% TPS

Right now Im game to try things that others have had success with.

Here is some pic of my pre-turbo intake piping. One observation i made is that the EVO bov ive been using is so stiff i cant push the valve open with my thumb.
Does this need to be a softer?

I have an older style HKS SSV Bov that vents to atmosphere im considering testing also. Its adjustable so might help and at the moment any change to this gives me a lead to how to cure it.

Attachment 9026
Attachment 9027

Are your wastegates plumbed with equal length hose from a T junction? Have you verified that both wastegates are cracking open at the same pressure?

Neither of the above should affect the partial boost issue you're seeing, FWIW. Sure sounds like typical compressor surge to me. There are fixes posted for that, none of them particularly pleasant. kywhitelightning's fix was essentially controlled boost leaks, one of the other fixes was a huge air hose between the turbo outlets, another fix is to go back to SMICs (obviously some custom work required there, heh)...

The wastegates hoses are unequal length from the T junction.
I would have to check the opening of the under boost to confirm if they both are opening at same pressure or not.

I am considering making up a reservoir within the pre turbo intake system to catch the surge before it hits the MAF.
Reckon if i can catch it with a baffled reservoir then it should allow enough time to allow the motor to digest the pressure in the system.

Failing that I have a HKS SSV bov and Turbsmart manual boost tee.
I just chucked it on the car earlier today and am hoping that somehow this will help.
I doubt it but im trying anyway.
The BOV is adjustable so im thinking i have it soft and allow pressure not able to be digested in the motor to vent out that instead.

Aside from all that then i'll get onto a switch solution as used by kywhitelightning and fastfalcon94.
Using Chrome ECU I have a spare output that should be able to be configured to do the job of making a small boost leak within a certain set of parameters.

Quote:

---

Originally Posted by DocWalt

Are your wastegates plumbed with equal length hose from a T junction? Have you verified that both wastegates are cracking open at the same pressure?

Neither of the above should affect the partial boost issue you're seeing, FWIW. Sure sounds like typical compressor surge to me. There are fixes posted for that, none of them particularly pleasant. kywhitelightning's fix was essentially controlled boost leaks, one of the other fixes was a huge air hose between the turbo outlets, another fix is to go back to SMICs (obviously some custom work required there, heh)...

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So I figured out what was going wrong with my setup.

Its wasn't an inherent Compressor surge issue but rather was caused by a couple of things.

Boost spiking caused by too much load (untuned) Target load were too high for the turbo's and causing them to spike high and that would cause the motor to backfire and jerk and stumble then the car would go into Limp mode (CEL)

Its scary how many times I had this happened but after a good tuning session and reducing the target load table in the ECU rom and modifying the WGDC tables I had the car holding steady 7-8lbs boost like it should without knock.

I also suspect that this problem I had was not helped by a dodgy fuel pump (Walbro 255 l that could have been a cheap knock off) and Narrowband O2 sensor that was not grounded correctly so my feedback trims were not updating correctly.

I will post up the logs of before and after.

I still need to somehow find the correct scaling for ecuflash for the Apexi MAP sensor I have been using as it is showing some funky boost pressure readings (otherwise I will just find another MAP sensor to hook up instead perhaps)

Thanks

Dougal