Boost controller help

[ste91]

Not for a Starlet but most of you on here have turbos so presumably there are people with good knowledge on boost controllers here.

I simply want full boost to come in as fast as possible and it doesn't matter if there's a slight boost spike as long as it settles down to the desired psi and holds there.
Currently on the standard turbo I have a little bit of wastegate creep, peak boost is 19psi or there abouts but the wastegate is cracking open at 15psi. To cure this I fitted a manual boost controller (ball and spring type) which gets the boost in just how I want it, no wastegate creep and it comes on boost fast and strong, however there seems to be a problem with it as even with it set to minimum it still wants to boost up to 25+ psi which is too much.

So I have two options - mess around with the MBC, fit a different spring inside it, see if I can get it working properly.

OR

Buy an EBC, however they cost a lot more and most of them have features/settings that I'm simply not interested in, and there's such a wide choice I have no idea what to go for, every search I've done brings up different results.

Obviously the first and cheapest thing to do would be try a different spring in the MBC and hopefully it works, but if that doesn't work then I wont mess around I'll be looking to buy an EBC.

Edited March 24, 2014 by ste91

[triple j]

What spring is in your wastegate, i would change that spring (not the mbc one) to a bigger psi one closer to your desired boost then use the mbc to crank it up that little to where u want it

[Chris_GlanzaV98]

as above get a spring as close to your desired boost pressure and then just adjust the mbc ever so slightly

[ste91]

You've both misunderstood the problem - the MBC wont adjust low enough. It's a standard GT1549 turbo with internal wastegate (comes with adjustable actuator as standard), it eventually gets to the 19-20psi that I want but it creeps open at 15psi so the last few psi rise very slowly.

To cure this I'm using a boost controller so the wastegate actuator doesn't see any boost until the boost controller "opens" - and it does work, however I can't get the MBC to go low enough, presumably because the spring in it is too strong and is keeping it shut even when it's adjusted to as low as it will go.

If I can't fix the MBC by using a different spring then I will just give up on it and go straight for an EBC.

[Phil]

Whats your adjustable actuator up to during all this?

im trying to remember how a MBC works but i think im right in saying that you bleed air away from your actuator?

i think what your trying to achieve is what a straight forward MBC cannot - GAIN.(ie all the boost as early as possible but without suffering chronic creep)

you should have your actuator set low and use your MBC to bring that up to your desired level. (straight forward, slightly laggier but no creep hopefully)

sounds like you have your actuator high and your using your MBC to bleed away when it sees the boost spike.

Phil

[ste91]

Whats your adjustable actuator up to during all this?

im trying to remember how a MBC works but i think im right in saying that you bleed air away from your actuator?

i think what your trying to achieve is what a straight forward MBC cannot - GAIN.(ie all the boost as early as possible but without suffering chronic creep)

you should have your actuator set low and use your MBC to bring that up to your desired level. (straight forward, slightly laggier but no creep hopefully)

sounds like you have your actuator high and your using your MBC to bleed away when it sees the boost spike.

Phil

The standard adjustable actuator works fine. It (eventually) makes 19psi and holds it but the wastegate creeps open once it reaches 15psi so the last 4-5 psi are slow to rise.

It's a ball and spring type MBC which is literally a ball-bearing behind a spring, when the desired pressure is reached the ball bearing moves and allows boost pressure to reach the wastegate actuator.

This prevents wastegate creep as the wastegate actuator doesn't see any boost right up until the desired pressure is reached so it cannot crack open too early.

Boost creep is different to wastegate creep - boost creep is not an issue. You can get boost spikes with MBC's but that's not an issue either, the MBC I've got simply wont adjust low enough, it just wants to aim for 25+ psi all the time and stay there (not a spike).

99% of people with this turbo just use the standard actuator but I'm using the MBC mainly to test it out ready for when I upgrade the turbo which I'll be doing very shortly, so I wanted to try it out ready for that so I know if it works. Turns out it doesn't! But it has shown me that it does fix wastegate creep. If only it could be set a little lower so it wasn't over boosting. I'll be running somewhere around 23psi on the bigger turbo so it wont be as much a problem then, but at the moment it's at least 5 psi too high and the standard GT15 wont last very long at that level of boost (it's almost identical in size to a CT9 and I'm upgrading to a small version of a TD04, from a 2.5 diesel engine).

I've taken it off the car for the time being, I'll try it again once I've found a slightly weaker spring.

Edited March 24, 2014 by ste91