boost problem with dawes device

[stumo]

The hole in a dawes is to let the pressure drop in the actuator once the ball has shut.

It sounds like you've got ...
shit/swarf/crap/etc in the dawes and that's causing the inconsistancy
or an actuator problem
or a prob with the piping/turbo etc

I've got a large 5 inch gauge that only goes to 30psi, it's sensitive enough to register you blowing on the tube, when connected up to the car with a dawes i've never seen it go over the set pressure by more than 1/2 psi .
Obviously if the pressure drops with a std turbo it's cos the turbo is running out of puff.

It's how they justify their "builds boost quicker" claim because there's no creeping of the wastegate as you approach the required boost.

true, there is no wastegate creep BUT that's what the "gain" is for, it essentially does the same thing

 

[williams]

My avcr has an extra port on the solenoid and I'm sure both my blitz controllers did.

 

[Perrin21]

ok heres the hole answer lol literally.

You may notice that many ball-and-spring type MBCs have, by design, a small hole… either in the case, or in one of its "barbs" or "nipples". In the picture below, the red arrow is pointing to such a hole. This does not indicate that it is actually a bleeder type MBC. Near the start of the last paragraph, it was stated that ball-and-spring type MBCs do not leak boost, "at least prior to reaching the desired boost level". Such a hole is typically on the "Wastegate side", so when boost is building on the charged-air side of the MBC, no pressure can go out that hole until after the desired boost level is achieved and the spring-loaded ball is pushed out of its seat. Then the boost signal rushes past the ball on its way to the Wastegate Actuator. The reason for that hole is to allow the "column" of charged air, or "boost signal", to drain or "bleed" out of the hose that sent the signal to the Wastegate Actuator. Without that hole, the charged air in the hose to the Wastegate Actuator would tend to "get trapped" and would slow the proper closing of the Wastegate. Technically, it is an inefficiency to allow some boost to escape, but it is a very small inefficiency that has a good trade-off. The inefficiency is relatively small so it really is not even worth mentioning… but that hole is a source of curiosity to many, so an explanation was warranted. Some ball-and-spring type controllers may not have such a hole and in those cases, the manufacturer may advise a small diameter "T" fitting or some other means of providing release hole

 

[skiddusmarkus]

I have ordered a new actuator spring that supports 12.5 psi to 17.0 psi . There's no way the existing actuator spring would be compatible as forge do 4 different ones. Fingers crossed its this.

Why?You should mess about with the Dawes more 1st to totally rule it out.To replace the actuator spring your turbo needs to come off unless you have monkey hands.

 

[Perrin21]

Why?You should mess about with the Dawes more 1st to totally rule it out.To replace the actuator spring your turbo needs to come off unless you have monkey hands.

The actuator spring will always be insufficient. Why try and make the actuator spring do what it was never designed to? That sounds like botching to me.

 

[skiddusmarkus]

If you buy a 17psi actuator you cannot turn it down, its 17psi for good.With the standard actuator you can always turn it up to 17psi with a boost controller.
What I meant was you aren't spending enough time trying to get the dawes to work and just jumping into buying something you might not need.I don't know if you will change the actuator yourself in which case it won't cost you anything but I got quoted 3-4 hours labour from 3 different tuners on here as its a turbo off job.
So you've gone from a £20 dawes to a £100 actuator and £150 labour to get the same result.

I actually have a forge actuator, the 17psi one but thats because I want to run 1.7-2 bar boost and my 1 bar actuator wouldn't really be up to it.My problem is the diaphragm split after 100 miles and although forge replaced it for free, I still have to shell out to have it removed and refitted.

 

[williams]

Personally, I would just go buy the ever reliable avcr. I fucked about with other boost controllers and actuators trying to get the right boost and get it to hold reliable. No problem at all with the avcr. Another case of you get what you pay for imo.

 

[Perrin21]

If you buy a 17psi actuator you cannot turn it down, its 17psi for good.With the standard actuator you can always turn it up to 17psi with a boost controller.
What I meant was you aren't spending enough time trying to get the dawes to work and just jumping into buying something you might not need.I don't know if you will change the actuator yourself in which case it won't cost you anything but I got quoted 3-4 hours labour from 3 different tuners on here as its a turbo off job.
So you've gone from a £20 dawes to a £100 actuator and £150 labour to get the same result.

I actually have a forge actuator, the 17psi one but thats because I want to run 1.7-2 bar boost and my 1 bar actuator wouldn't really be up to it.My problem is the diaphragm split after 100 miles and although forge replaced it for free, I still have to shell out to have it removed and refitted.

17psi is only 1.1Bar . why would i want to turn it down? as for fitting the spring, lets hope its not turbo off. The actuator was already on the car and the replacement spring cost £16 delivered.

 

[skiddusmarkus]

Maybe you don't want to turn it down but you don't have a choice wuith the stronger spring is what I mean.I have the forge actuator on and I cannot take the top off in situ as a couple of the grub screws are blocked by the gearbox.I don't have a standard turbo so maybe you will be lucky but when I searched others said it was easier to take the turbo off to swap the actuator than fanny about trying to get to it on the car.
It still doesn't alter the fact that you will be paying money out you might not need to.The 1st thing I'd do is strip the dawes down and see if there's any shit in it and mess about with winding it out by different amounts.Then I'd try and borrow someone elses if that didn't cure it.Then pressure test the actuator and go from there.Spend more money only after you've tried everything else or your shopping list is going to have to keep waiting.

 

[williams]

pressure test teh actuator 1st, takes a couple mins and parts dont need to be removed or setup or anything.

 

[Perrin21]

pressure test teh actuator 1st, takes a couple mins and parts dont need to be removed or setup or anything.

surely if the actuator spring is set up for 0.7bar then if its working 100% I'd still need the stiffer spring to up the boost to 1.1bar properly. What's happening at the moment is that the car boosts to 1.2 or 1 bar using the dawes device and then the boost drops as the revs build by about 0.5 back to 0.7 . This seems like the spring is too weak in the actuator to me. Have I missed the point on how this works?

 

[red reading]

actuator spring is too weak, the wastegate is being pushed open by the flow at high revs.

 

[Perrin21]

actuator spring is too weak, the wastegate is being pushed open by the flow at high revs.

That was my thoughts. Glad someone agrees, the new spring should arrive tomorrow. I will find out then. You have given me hope red reading

 

[skiddusmarkus]

Chances are Danny is right, but if you don't do the easy tests 1st, every time you have a problem it will end up costing you a fortune.None of the things suggested costs a penny to do, just a bit of time.

 

[Perrin21]

Chances are Danny is right, but if you don't do the easy tests 1st, every time you have a problem it will end up costing you a fortune.None of the things suggested costs a penny to do, just a bit of time.

I couldn't agree more, however as is obvious with my questions I'm non technical and require help with the mechanics of it, hence the time isn't free as I'm paying (or trying to pay) for someone else's. If I knew what I was doing I'd happily spend hours doing it myself but the last thing I took apart was my push bike lol. Oh and I have zero tools.

 

[williams]

That's what a boost controller does, allows you to run more pressure than the actuator is rated at. I think red meanss the spring is weaker than it should be. I ran 1.4 bar with no problems on a standard actuator. Held boost fine.

 

[williams]

If your actuator is working fine then there is nor reason at all why you can't run that boost on that actuator spring, test that before you buy anything.

 

[gtirx2]

I to have/had the same problem and i am using an avc-r,i am also using a 1bar forge actuator.

I did not look into it much at the time tbh and my cars been off the road for ages now,but at the time i was also suspecting the actuator.


It never use to do it on the old stock actuator with the same boost controller,it only started happening after i fitted the forge.


Mine was even like it with the boost controller turned off running just on actuator pressure,It would hold a good solid bar until the high revs and always drop off.

You could even set the avcr to 90% duty in the high revs and it would still drop the boost the same,you could hear the avcr bleeding the pressure still though so thats why i assumed it was the actuator and not the avcr solenoid.

The actulator was also fitted to 3 other standard turbos over the time and it was always the same,so it was not an iffy turbo.

It was fine through out the rest of the revs range and i could set it to what i wanted, but i always had the same drop in boost at the top.

I wish i did look into it abit more at the time tbh,like trying a bleed valve on it etc,but i was going to change turbos so i was going to look into it then and change the spring at the same time.

Like mentioned though at the time i was also pretty convinced it was the actuator getting blown open,the only thing that was making me dout it though was when i tested the actulator once with the compresser, compaired to a standard one it was a lot stiffer and took more pressure to open just like you would expect, and seemed to be working fine tbh, so was always still abit unsure if it was definatally that.

I had even taken the actuator apart and it all look fine.

lol its doing my head in now just thinking about it,heres a graph of what mine was doing.

 

[geoff pine]

I'm thinking it might just be better to fit a stronger spring in the actuator rated to 1.15 bar and remove the Dawes device, wouldn't this be better?

Is this a dawes device or just a cheap ebay lookalike ???you do know if you only use the actuator as a means of controling your boost you could be running at almost double the spring pressure.

 

[geoff pine]

You could do the 1 bar loop and if you dont hit 1 bar then that could tell you that your actuator is stuffed but thats if theres no problems with your turbo.