ShelGame
07-27-2008, 12:28 PM
OK, so I built another Mitsu up from spare parts that I had. The previous turbo had a turbine exducer that measured 1.68. The one I put in (the best that I have) measures 1.745". The old one had ~0.04" wall clearance between the exducer and the housing!
First 3 runs Friday night were good. Pretty close times, fastest run I've had in the car (13.78 @ 97mph). But, the 3rd run, the boost was back to being lazy. Pretty quick to get up to 15-16psi, but then a slow creep up to the 19psi setpoint. Not sure what's going on, but I think I have an idea - It's in the WG somewhere. The only parts on this turbo that I kept were the O2 housing (SV is in the O2 housing on the Mitsu) and the WGA. I'm thinking the WGA is leaking when hot or something. Like maybe a pinhole in the diaphram that opens up the hotter the car gets. The 4th run was 2nd round of the brakcet race, and it was run round-robin, so the car was still hot.
Also, last fall when the WG siezed, I got 23psi pretty much instantly, no creep. Surprisingly, it was a pretty stabe 23psi. So, I don't think thslow boost rise is a turbo issue per se.
Has anyone had a WGA fail? What are the symptons? How would you test it? The WGA I'm using was brand new 2 years ago, and it's only been on the track. Still looks shiny and new.
Here's another thought - maybe the exhasut pressure is pushing open the WG a little? What if I plumbed vacuum to the 3rd barb on the WG solenoid? So that the WGA see vac until the solenoid switches? Is there a good vac source when in boost? Do either of the throttle body ports generate vac when boosting? I'm guessing no...
I gotta figure this out. The slow boost rise cost me the round (well, it wouldv'e if I hadn't red-lighted :) ). Gotta be able to dial the car...
EDIT: I looked at all 4 of my datasets from Friday night. It basically did the slow rise thing on all of them, it was just much worse on the 3rd run. Could it be that I simply need to shim the WGA? How much should be enough? I'm thinking a couple of 1/4" thick spacers from Ace hardware will do the trick. Or is that too much?
First 3 runs Friday night were good. Pretty close times, fastest run I've had in the car (13.78 @ 97mph). But, the 3rd run, the boost was back to being lazy. Pretty quick to get up to 15-16psi, but then a slow creep up to the 19psi setpoint. Not sure what's going on, but I think I have an idea - It's in the WG somewhere. The only parts on this turbo that I kept were the O2 housing (SV is in the O2 housing on the Mitsu) and the WGA. I'm thinking the WGA is leaking when hot or something. Like maybe a pinhole in the diaphram that opens up the hotter the car gets. The 4th run was 2nd round of the brakcet race, and it was run round-robin, so the car was still hot.
Also, last fall when the WG siezed, I got 23psi pretty much instantly, no creep. Surprisingly, it was a pretty stabe 23psi. So, I don't think thslow boost rise is a turbo issue per se.
Has anyone had a WGA fail? What are the symptons? How would you test it? The WGA I'm using was brand new 2 years ago, and it's only been on the track. Still looks shiny and new.
Here's another thought - maybe the exhasut pressure is pushing open the WG a little? What if I plumbed vacuum to the 3rd barb on the WG solenoid? So that the WGA see vac until the solenoid switches? Is there a good vac source when in boost? Do either of the throttle body ports generate vac when boosting? I'm guessing no...
I gotta figure this out. The slow boost rise cost me the round (well, it wouldv'e if I hadn't red-lighted :) ). Gotta be able to dial the car...
EDIT: I looked at all 4 of my datasets from Friday night. It basically did the slow rise thing on all of them, it was just much worse on the 3rd run. Could it be that I simply need to shim the WGA? How much should be enough? I'm thinking a couple of 1/4" thick spacers from Ace hardware will do the trick. Or is that too much?