14b Questions

One of my friends is upgrading to an evoIII 16g, so he's selling me his 14b for dirt cheap! However, I've got a few questions first. I have a 95 GSX, fyi.

1.) Will I need an install kit or will it just bolt right in?
2.) Will it hold boost til redline (or at least better than this gay t-25 POS)?
3.) I'm getting a 3" exhaust from the turbo back (porting the o2 sensor housing as well), will I have any MAJOR creep issues with the 14b?

Thanks! :)

You will need an install kit

install kit, boost to redline, some creep.

If, and I stress if... you do a killer porting of the wastegate bowl and the entire wastegate passage in the O2 housing you can get the 14b to hold 14 psi with zero creep any gear, and rpm w/3" exh. I've done it. It takes a lot of material to be removed from the stock O2 housing waste passage and an intelligent reshaping of the wastegate bowl and flapper orifice. IMO now would be a good time to get the EVO O2 housing, it fits 3" exh. perfect and flows far better on the exhaust and waste passage than the stock housing does.

I got my 14b boost creep down from 22 psi (!) to less than 15 psi without enlarging the WG runner in the O2 housing, just cutting the divider back to make up for poor sensor placement on Mitsu's part. LEt me try to find the info for a cut and paste.

----------
With a 2.5 inch Busher turbo back I got creep. Both with the cat and especially without it. 18-19 psi on the cat, 22 psi on the test pipe. 3" exhaust would have been worse. 22 psi on my little 14b on pump gas? Not cool ;o) I tried everything from external dumps to different turbine housings (my flapper arm was bunk) to no avail. I finally broke down and ported the turbine housing, flapper hole, and O2 housing. No more creep. I have set it as low as 15 with no problems.

-----------------------------------------------------------------------



> > success in fixing it with a ported o2 housing. Is this the way to
> > go?

Just for the sake of getting this into the archives some more I'll go over my experiences with boost creep on a 14b again. I had a 14b with 2.5 inch BR turbo back, including highflow cat. I had 18 or so psi of boost creep. At the time I was more concerned with race gas track time so I let it slide... I put on a 2.5 inch test pipe. While it did add 1.5 mph consistently at the track (or about 15 hp at 3300 lbs) it also bumped my boost creep up to 22 psi. Obviously that is unacceptable on pump gas ;o)

I started by changing to another turbine housing since I thought I noticed my flapper haging up on something. That had no effect. Same goes for swapping the actuator. I then added a 2.5 inch tubular SS external dump O2 housing from Victory Performance. That had NO effect whatsoever. Aside from making my DSM sound like a rusty 88 cavalier with no muffler ;o) I let my flapper "swing free" and I still got around 17-18 psi. (attached to the actuator, the flapper only opens up about 45 degrees) It was obvious the stock wastegate just wasnt flowing enough for my 2.5 inch turbo back setup.

So the porting began. I started out by not doing much to the flapper hole diameter itself, but concentrating on the wasgate exit area (see the vfaqs). I looked at where the gasses flow to and from and "hit the apexes" :o) Then I match ported the O2 housing in that area and took the divider down a bit. On 2g O2 housing the sensor sits right in front of where the wasgate gasses rejoin the main exhaust. It couldnt be much worse. For this reason I think 2g may have a slightly bigger problem with creep than 1g. This got me down to about 17 psi. Not bad for barely touching the hole.

I went back in again and got it to 16 psi. Timing was still junk so I went back in again and opened up the hole a touch. This time I got things down to 15 psi. Timing looked great.


Kevin Jewer
95 GSX - 14b
12.74 at 109



================================================== ================================


When I was creeping to 22-23 psi on the 14b, I tried an external dump
tubular O2 housing hoping that it would be an easy fix. It had
absolutely no effect on my creep.

Which brings me back to my original theory. If you are using stock
sized flapper, O2 housing is the least of your wastegate
restrictions, especially on 1g housing. I think due to the fact that
the sensor is right in front of the divider, the 2g housing is worse
despite the appearance of a larger runner. I think the Mitsu
engineers said "Lets make the runner 15% bigger, and then block 70%
of the opening with an O2 sensor!" But sadly not only do I think they
said that, they got paid for it, and by us no less... ;o)

Kevin Jewer
95 GSX - 14b
12.74 at 109

You need to notch the turbine housing so the flapper can open fully. I forget the exact spot but it hangs up otherwise.

Damn, that was so much more information than I thought I was gonna get, thanks guys!!! :)

You need to notch the turbine housing so the flapper can open fully. I forget the exact spot but it hangs up otherwise.

That only helps when you need to port the flapper hole. The actuator can only open the flapper about 45 degrees, so it never hits that spot no matter how much you port it. :) The fact that it only opens 45 degrees or so is the reason that porting the WG exit area is SO important. Far more important than the O2 housing passage.