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View Full Version : Crazy idea! Need your thoughts.



blkd_outA401
10-17-2011, 09:00 AM
Ok first I just wanna lay the foundation for the thought. I have had to do a lot of work on my 01 1.8 because I bought the car with problems. New head, got that on then the k03 blew up so put on an ebay k04. I know, I know, SHIT! All the ripping on me aside. The turbo is still holding up after 5k. Only problem I am having with it is overboosting. Figured out that the pressure coming from the nipple on the compressor is lower than what is going into the intake, which is why I am overboosting. So I need to use a MBC to limit the boost. Now I have done a lot of searching and research about an MBC and most suggest that I use it in parallel with the N75 so that is what I am going to do. Oh, BTW I have a revo stage 2 along with this, other than that and the k04 it is stock.
Here is my crazy idea. I read that some people are hooking up there MBC to manifold pressure to accuate the wastegate. What I am thinking is if I keep the n75 hooked up the way it is and add the MBC in like this, hook the pressure side of it to manifold pressure and the bleed side, T'ed in with the N75.
I am thinking that under heavy load that the MBC will control the accuation of the WG, and under small load the N75 will control the WG because there is not enough pressure to push the MBC. Bad picture but gets my idea across.
Let me know. If you think this could work.
Thanks

https://lh4.googleusercontent.com/-v_5jRuKSzno/TpxQ8wRoYcI/AAAAAAAAABQ/BTCbzkEGG-U/s912/Untitled.jpg

bmarshall
10-17-2011, 06:15 PM
This is still in parallel sort of, the manifold will see slightly less pressure than at the compressor because of the pressure drop across the intercooler but you should be able to adjust for this with the MBC.

colony7
10-17-2011, 08:57 PM
it wont work, the pressure at your turbo maybe be lower than your manifold, but that can only be temporary. it all has to equal out at some point, and your n75 will open no matter what at the tune's demand. whatever that boost is, you wont get above with this setup

walky_talky20
10-18-2011, 05:37 AM
Pressure at the compressor housing should be higher, if anything, than at the manifold. So I don't think that is your problem (how did you come up with that exactly?).

Your problem most likely has to do with the crap (as in complete garbage) exhaust housing that is not manufactured properly. The wastegate port is not machined large enough to effectively control the boost. In such a case, the wastegate port would need "ported" to make it work properly. This is a very common issue with ebay K04's.

blkd_outA401
10-18-2011, 08:04 AM
Pressure at the compressor housing should be higher, if anything, than at the manifold. So I don't think that is your problem (how did you come up with that exactly?).

Your problem most likely has to do with the crap (as in complete garbage) exhaust housing that is not manufactured properly. The wastegate port is not machined large enough to effectively control the boost. In such a case, the wastegate port would need "ported" to make it work properly. This is a very common issue with ebay K04's.

I have read a lot of the threads about the ebay turbos and am full aware of how the machining on the WG is smaller than it is supposed to be. I hooked up a boost gauge at the compressor along with my in car that is measuring manifold pressure and they were off by about 2-6 psi. This is what has lead me to this. I know this turbo is a chinese knock off and its not the best route but it is what it is and that is what I have for now. After I did the checking, I took it to the shop that did my REVO tune and he confirmed the pressure varience. Everything I have read on EBAY turbo, none of it says anything about the difference in pressures from what is at the compressor and at the manifold.

walky_talky20
10-18-2011, 08:09 AM
And you did A-B-A testing by swapping the gauges? I don't know how your intercooler piping and manifold is managing to amplify the boost pressure, but that's pretty sweet. Need to get me some of that.

Perhaps it is just the port or fitting on the compressor housing which is restrictive and not allowing full pressure to reach the N75. That's the only thing I can think of.

blkd_outA401
10-18-2011, 08:21 AM
And you did A-B-A testing by swapping the gauges? I don't know how your intercooler piping and manifold is managing to amplify the boost pressure, but that's pretty sweet. Need to get me some of that.

Perhaps it is just the port or fitting on the compressor housing which is restrictive and not allowing full pressure to reach the N75. That's the only thing I can think of.

Yes, after i tested one I swapped them to make sure that MY gauge was working and sure enough. My and the mech's best guess is that the porting for the compressor housing is too far away from the fins which makes it not build enough. I have tested the fitting too and it is working properly. In turn, it is throwing off the timing and acuation of the WG. The WG is just not opening soon enough. The overboost is just more of a spike. Cause it will hit 30psi, I think because my gauge only goes to 25 and it pegs straight down, but only spike to that. It never holds, it just hits and then levels at where the tune wants it, which is 20psi. So i figure if I use a MBC, which was the mech's suggestion, and tune it down to about 13-15psi that should compensate for the spike right?

blkd_outA401
10-18-2011, 08:23 AM
That and I am just gonna try and fix it this way and run it till that turbo blows up. Which shouldnt be too much longer seeing how I have been running this EBAY turbo longer than most.