Losing boost. Dodgy mbc? Actuator?

[Rik]

Bit of an annoying problem. I'm boosting to 1bar but quickly dropping back down to 0.5. Before I could keep it at about 0.85 without any drop. I put my new manifold on today so turned the boost up to 1bar (got all fueling mods taken care of) and its dropping down to 0.5 bar pretty quick. Could it just be the turbo/actuator on its last legs or dodgy mbc?

The mbc is abit of a weird one, its an ab88 one and it's always acted strange in that to gain more boost, you wind it to negative..instead of positive! It's fully wound to negative now and it boosts to 1bar, if I add more positive, it will just take it down to around 0.5 and stay there! I've asked around to make sure that its plumbed in ok, which I got told it is.

Pic:

Does anyone know what the problem could be?

I'll find out eventually as im waiting on my other speedvision hybrid to arrive so that will eliminate the turbo and actuator from the equation and i'm trying to get hold of an ebc to see if that fixes it. If anyone has any suggestions though, pleeeeease tell me!

 

[Sigma]

If you have to wind it down, to turn the boost up, then just switch the pipes round.

It's only a valve!

 

[Rik]

I tried mate, still does the same lol. I originally had the pipes round the other way and it did the same so swapped them to how they are now...and still the same! Crazy thing.

 

[12345678]

Bit of an annoying problem. I'm boosting to 1bar but quickly dropping back down to 0.5.

could it be your boost tee?
surely it reduces the rate of flow to the actuator - giving you higher boost, but would it also not reduce the rate of flow from the actuator i.e. holding the wastegate open for longer, causing your boost pressure to drop?
Just a thought.

 

[Suspected_Psycho]

Is it just a standard actuator or a HKS Ajustable?.. I'm thinking that its not the MBC, as if it hits 1.0bar, then its not going to limit it to 0.5..

Its possible the actuator is not strong enough to keep the wastegate closed so its leaking out, but as much as .5 bar? hmmm seems suspect! Just thinking alloud!

Seeing from the pic its just stock.. should be good for 0.6bar tho.. unless its completly screwed!

 

[weakboy2]

also there should be a one way vavle in line with that boost controller? ball an spring valves always spike then drop boost of unfortunatly

 

[Rik]

I think im just gonna go with a EBC guys, I just have this on temp. till the funds allow such things! lol Cheers for the help!

 

[fastglanza]

it looks like a std actuator which will bleed boost off. the speedvision hybrid will have an upgraded actuator.

 

[mini_boost]

i had dat same mbc it did d same tin wit d positive negative tin but it worked wel but i find it spikes boost.

neways i believe ur actuator is bad looks like a ct9 there n those actuators usually give out especially wen u raise d boost above stock i went thru 2 stock actuators. i had d same problem wit both actuators so i decided to use an actuator off a nissan sr20det which is a t28 turbo had to dril one hole in d rod it was to long n mount it to d ct9 wit only one bolt n it never moved or shifted n my boost problem was fixd n now my base boost is around 7psi ~.5bar.never installed d mbc after changin actuator 7psi wit d 5efthe is nice in no hurry for more power yet

ur mbc is connected correct but make sure to plug all d other lines u dont want to be wastin time wen its just an open line sumwhere............ happy boostin

 

[Starlet_Sam]

I had that boost controller, absolute toss. I had it at 1.1bar and it would drop off to 0.7bar, I took it off and adjusted the actuator to 1.1bar and it held so much better, dropping from 1.1bar to 1bar. Throw it in the bin mate, it's the worst product that ToyTuning have EVER sold.

 

[Nwimie]

i had a simular boost controller and it was awfull! soon replaced it with a EBC thats probley where the problem lies tbh.

 

[Deano]

Not all mbc's are bad I have a turbosmart boost tee on my car when it was connected it was brilliant never had a problem

 

[sx_turbo]

i'm still investigating the reasons for my boost loss.

i'm hoping its not my ebc, but you never know.

im changing the wastegate (mine had a hair line crack in it) and changing the actuator to a jam one aswell and make the piping route shorter.

fingers crossed just doing those 2 will will stop mine from dropping

 

[Rik]

Sounds like its best to get rid then! Cost feck all so not too fussed, will keep it on till hybrid comes i guess! Hopefully will get hold of an ebc for then. What ebc does everyone use? I'm thinking about trying an hdi one with the gauge they are doing, anyone used one?

Also, not sure if i will get replies about this one but noticed that my hks ssqv is sticking abit (i think) if i rev the car slightly i can feel the air come out an when it dumps, it will dump like normal, but then have abit of air come out still afterwards. Now i dont remember it doing this before :| it was dumped the air straight away an that was it. I took it apart before an put some oil in to try sort it but it still sticks. Am i best taking the whole thing apart to look at the spring etc?