after installing the first mbc higher gears under a load boost shoots to25+ psi... bought a new mbc same problem... if doing a full pull boost seems steady 15 psi tailing off to about 12 in the high rps.... does anyone else have a similar problem.... i know what i thinks causing it is the wastegat cant let enough exhaust out fast enough but its kind wierd i know other ppl are running an mbc with no problems... im thinking of cuting a hole in the turbine housing and welding a pipe in to run an external dump out of the top of the housing...
Have you adjusted your wastegate rod out all the way or are you just relying on the mbc? Ive read that if your upping the boost 100% on the boost controller and not adjusting your wastegate accordingly it can cause spikes.
So that being said you should have your wastegate set at full boost and then use the mbc to add the extra 2psi.
Whatever you do DONT start cutting into your turbo.
it spikes the same whether the rod is stock or adjusted in... and its just a 125 dollar turbo.. if i can run an external gate its worth it... i wasnt planning on testing it on the turbo im using just a spare laying around...
I would guess then you have a different issue. There is alot of people running this setup without the issues you have posted.
Id look into a mechanical problem. instead of hacking things up id fix the problem as its probably something small and easy.
If it were me this is what id do:
-Take off the mbc and adjust your wastegate down to the lowest boost level and see what happens and what boost your getting.
-then adjust your wastegate to the max boost level and see what boost levels your getting there.
That puts the system back to stock and within the capabilities of the turbo and if your still getting the spike or other odd things you know its an issue with either your vac lines or your wastegate may just be bad.
The idea is to fix the problem not band aid it.
Yes, I would never try to run my saab set up to 25-30psi, this is way out of the efficentcy range of this turbo, you are holding a stick of dynamite, and let me guess stock lower end?
no one said anything about holding 25 psi... a spike is a spike... im running 15 psi..
Have you done what I said yet? Has it fixed the spikes?
Bottom line hitting 25 psi is way out of the Saab's turbo efficentcy range.
i have seen many mbc cause a delay long enough for the boost to spike. lose the mbc and see if the boost doesnt spike.
If you get a good mbc the ones with a bleed off hole drilled in it that will help the spiking issue.
ive done everything possible... i have both styles of mbc i have solid and bleeder and both make spikes...there are no spikes running the compressor with no mbc... you would have to be here to understand the problem....
So the problem lies in the mbc...plain and simple....
Try hooking it up and having it turned all the way down and then slowly turn it up and test it out and keep on going till you have the same issue.
If it does it right from the start then its the controller plain and simple.
ecotecnik wrote:ive done everything possible... i have both styles of mbc i have solid and bleeder and both make spikes...there are no spikes running the compressor with no mbc... you would have to be here to understand the problem....
this is why i no longer use mbc's. if i want to regulate boost on an internal wastegate turbo i modifiy the wastegate actuator rod so that i can adjust the boost with the rod instead of with a mbc.
