Hi,

We had similar issues with the boost. All over the place.

We removed the vacuum driven wastegate actuator and replaced with a standard pressure driven wastegate actuator.

I've never looked back and have had completely consistent boost since.

Appreciate it is stepping back in time technology wise but it just removed all the heartache of fluctuating boost.

I think our actuator came from a Garret t25 turbo.

Regards,
Steven RW

 

Yes. Whatever comes with the owens turbo.
Had soma bad vac hose. It worked but didn't like it. Put some new stuff on it. It was smaller inside diameter. It made no difference.

 

What's the vacuum tank for ? What happens if I by pass it to eliminate the possibility of a damaged tank.

 

I'm not sure I am answering your question, or telling you anything new but, in a bid to share:

The standard MCS system uses a pump created vacuum to suck the wastegate shut. Without a vacuum the spring in the actuator actually OPENS the wastegate. The good news is that any leaks in pipes leading to the actuator or the actuator pipe blowing off result in zero boost rather than on an older system where the actuator spring holds the wastegate shut and requires boost pressure to be applied to the actuator to open the wastegate. When it has a leak in the pipework the boost doesn't reach the actuator and the car over boosts.

Also the more modern system allows the ecu to decide it isn't happy and send no vacuum to the actuator and run zero boost if it doesn't like something. Whereas the older fashioned system didn't have that ability (some had the equivalent of an electronic bleed valve called an Amal valve that allowed for something similar but it was reduced boost rather than no boost).

For me, just putting an older style pressure driven actuator on the turbo, and just running a pipe from the intercooler to the actuator (a small boost feed) gave me much more control.

How the standard system works is the ecu sends a repetitive pulse to the vacuum unit to "try" and control the boost. We found on our later map it just didn't give the boost we wanted. No simple stable figures. It was all over the place and fluctuating say every 1 to 2 seconds from .5 to 1.5bar. So we got rid of it all.

Just sharing some of my experience. Hope it assists.

Cheers
Steven RW

 

Wow I don't know what I was thinking, I must have put something in my coffee this morning.

 

Hi have you checked Airflow readings. I was having what I thought was low boost because I was focused on the psi on the second head which flows more. I actually get lower psi readings but higher lb/min in air flow all the head work seems to make a big difference. Could the relationship between expected boost psi and MAF readings be throwing the tunes a bit off.


Super great about getting a shop my friends always have more work than they can do, someone is always into a project and clearly this is a passion for you.

 

I think I posted you can watch the gauge drop the longer I stay on the throttle. It loses boost. It's a new problem. It's never done this before.

 

I started this like three times not wanting to be a bother. But I still think you the mechanic could have it set up correctly and its just the ECU and the like 6ft run of tube that has to charge up then gets pressure, then eases a bit and then the ECU decides hay were just cruising at rocket speed. I like the dual balance I have, laid back cruising or blast, but I do sometimes miss dual webers, points ignition, and mechanical linkages. Sometimes I feel like I have to convince the ECU to do what I want just a bit, especially if Im not in Sport mode, still that mid-range torque that stays fat. Anyway Im just saying I vote ECU. PS not knocking tune but ECU

 

Starting to wonder that myself. Since today I happen to find my old vacuum lines that controlled the turbo. Put vacuum on the tank and it held forever if I let It that long. Put the hand vac pump on the wastegate vac actuator. Walked away, had lunch, went back. Worked perfectly. It's got the original vac lines now. NEW pressure converter. NEW IAT sensor. Changed the map sensor. Went for a ride. Same old crap. So let's go over the configuration of this car now,
New pressure converter
Installed factory hard line vac lines
New IAT
Known GOOD map sensor.
PCV delete so no boost is going through the valve cover at all.
NEW vacuum pump
All boost tubes were gone over today and they are all tight.
IT STILL PULLS MAX BOOST, shift it drops to
15 psi and continues to drop. It'll actually sit and hover around factory boost setting at wide open throttle.
At this point with as much money as I've spent, this isn't the type of car I would recommend modifying. Wanna go fast, stick with mustang and camaro's. The V8 stuff. It's one thing after another. I'm starting to lean towards ecu myself.
ITS THE ONLY THING LEFT !!!
Connect the waste gate directly to the vac pump
It'll pull awesome boost and go. Ask the ecu to do it, NOPE !!!

 

Can someone please correct if I'm wrong, I'm just trying figure out why all of a sudden I can hold max boost.
Was there a tuner awhile back or some kind of issue were the ECU's tried to resort back because it didn't like high boost settings ?
By the way, there's no engine lights during ithe boost loss either.

 

One more thought on the subject --- every once in awhile, I'll use my AP to reset the ECU. 95% of my driving is without boost and the ECU "learns" my driving habits. When I mentioned earlier that my boost problem hasn't come back since I left Vegas, I didn't mention that the ECU had been reset randomly since then.

This afternoon, temp in the mid 80's, I lost boost over 10psi. Within 2 minutes I pulled over and reset the ECU. Guess what --- I had max boost again. Now, this could be coincidence, but you gotta believe I'm gonna try the same fix next time it happens.

It's a pretty easy thing to do IF you have an AccessPort. Maybe some of the aftermarket scanners have the same feature, I'm clueless --- no one else in my local mini club has any significant mods. Another way to reset it is to disconnect the battery for a short period (define "short period"?)

Sprintcars, maybe before you give up completely, you could try resetting your ECU? I'm not suggesting you're driving as slow as I do, just that our ECU is "tempermental" at best. A reset puts it back where the tuner wants it.

 

I heard of clearing codes by disconnecting the battery. The other is by disconnecting the positive and negative from the battery then hold them together. Idk. I have no access port. I've got scanners to clear codes but nothing to reset that I know of. I got bavarian technics.

 

When you say you lose boost, you mean it won't go to max or it drops after you reach max boost ?

 

Takes forever to get up to 10psi. Nowhere near max.

Admittedly, different from what you describe as your problem, but my point is the ECU reset fixes it.

By disconnecting the battery, the worst that can happen is you gotta reset the clock and maybe a gauge or two. Well worth it if the problem gets fixed.

 

I've had similar boost issues too but seems like u addressed most of the culprits. I've heard the vacuum res. tank cracks and/or get moisture build up. Worth pulling it off and checking. All lines new and stiff as to not collapse?
I believe you have a Manic tune?? Call Nicholas if so. What diverter you running? Do you hear the turbo boosting? The fact that u bypassed the ECU controlled vacuum and manually close the WG seems to eliminate some these ideas. I'm a big believer in looking at what data the ECU see's for allowing/not allowing boost; IAT, coolant temps, possible ign timing, MAP and MAF. Need to think, look and see what the ECM is seeing Not sure what exactly it takes to go in limp 1/2 power mode but my car would not boost with no check engine light when I ran a Ultimate Chip.
Sorry for the issue(s) I know its maddening.

 

Go Manual boost control. End

My view :-)

 

Yea I understand, mine will jump to max boost for a given map setting.?then slowly start losing it. If I let it go, it will eventually hover around the factory boost level. If I let off the gas peddle to pull max Vacuum then go back to full throttle, it will pull max commanded boost. But once again it'll start Losing pressure. Look at previous posts for a list of new parts.

 

Would if I knew who made a controller. It'd definitely be worth a try.

 

Look into an Apexi AVC-R. If I remember correctly thepenl has been running it on his for a while with great results.

 

While there is nothing like a flathead V8 for fun and sound, I can lift this engine and with the trans it is still light, and I like the mechanics of this engine. While going to manual boost control is an option being able to curve the boost is a good thing. Aftermarket boost computers often come with an upgraded control solenoid which could be something to look at I have one on my list. But I still go back to ECU, it has no problem handling fuel adjustments etc. its more a mode sort of thing that it is doing on purpose.


I know I have had to adjust my thinking in regards to how I handle the throttle, It is sensitive to the speed of attack. If I give it a good fast tap it will bump into full boost but if Im a hair slower it goes into a bit more laid back boost. Down shifting to 4th with a drop in rpms then fast on the throttle seems to always give me full on boost. Driving in track mode 3000rpms to redline also has an effect of on response. I also find I go all the way to the floor more than other set ups. Hills might be a way to test this a bit I have several 45deg climbs and it really digs in on those. On a new tune I could hardly go without chirping the tires, now launch is more relaxed unless I really try , so the system seems adaptable. I know in boost it uses fixed maps but when and how it chooses to go to maps or drop back seems to be part of its personality.


On the sensor control side, see if you can get raw voltage readings in your logs and track throttle position against each sensor individually.


Could this be a default to the masses sort of thing keep grandma from spinning her tires and going to full boost only under exact throttle inputs.

 

If you're ready to make some significant changes --- turbo diaphragm, from vacuum to pressure actuated, there's an outfit called TurboX that makes boost controllers, both manual and "automatic". I've been using a manual one for about 4 years now, with my Garrett. Until recently, boost has been trouble-free. As I understand their operation, they just increase the pressure required to activate the wastegate diaphragm. Default activation - without a manual boost controller, is typically 10 - 15 psi, and is adjustable a little bit with the linkage. Possibly, one of the turbo houses sells diaphragms / linkage separately. I used ATP Turbo as my source for turbo "stuff". There's also Turbo-Kits. Both have a big selection.

My experience with turbos is limited to the Mini's version --- with a vacuum operated wastegate. It's my understanding that most other automotive turbos are positive pressure controlled, but that's changing as more cars are becoming computer controlled. Might be wiser to stay with the vacuum system and learn to work with it --- personal choice.

'Course, none of this will fix a flaky ECU. And, it's only for controlling the wastegate. There are several other factors in controlling the amount of boost, as mentioned earlier.

And, thank you Euler-Spiral, for confirming the ECU "learning" process. It's got to be a significant factor in a non-OEM tune retaining its benefits. That's why I randomly reset my ECU --- extremely easy with the AP.

 

I'm not willing to make any significant changes for blow off valves. I'm done spending money and throwing parts at this thing. As far as I'm concerned I've spend a lot of money and I've got a car that had no more power than a stock car/engine on map C.
Just researched the ifs for the pressure converter and all that stuff. They are all correct.
It's going back together. If it still does it, I'll check to see what's owed at the bank and research my options. Selling it will be one.
I'll go back to V8. I like the cat but I don't like it to the point were the aggravation factor far exceeds the return of pleasure.

 

FYI: just upgrading turbos on the M3 would net 600hp easy...

Harsh reality.

 

I'm not getting another bmw nightmare. With the parts around the shop, I can get a 800-900 BBC
And put it in an older car. All done. No damn computers. The sensor this sensor that. 1 carb. 1 magneto. Done. Oh, by the way. Just had help with the car. No fixy. So I got the worlds slowest stage 3 whatever with a ported head, cams, methanol injection and one of the best turbo's you can buy.

 

You would have been better off with minor porting, stock turbo and meth injection with your stronger bottom end. You could have easily run Map C and Map B indefinitely. Sorry to hear of your turbo boost issues.