i think it's still the wastegate, mine did the same thing on the dyno, now i think the helper spring is fatigued since now it's not rising back up anymore. this is going to be a project for me as well. anyone have any luck with the cheaper ebay wastegates?

 

I have a brand new 8psi wastegate can. This is the same one that Joe used on his greddy kit.

http://www.flyinmiata.com/index.php?...umber=02-70576

$35 + shipping.

 

Whats the diameter on the can? There not much room there between turbo and valve cover. If it fits I'll take it. PM me your paypal info.

 

This is the same unit that Joe Perez used on his Greddy kit, so I assume it'll fit. I bought it originally to use with my Greddy kist, but I went with a different turbo setup and don't need it any longer.

I won't be able to give you a shipping quote until tuesday, tomorrow is a holiday here.

Jay

 

Took me a while to find the pictures. My bracket actually isn't as cool as Koto's, just a piece of 16ga sheet steel. Also, mine is a different can; rather than the two studs, it has a welded-on flange. Otherwise identical, but I got it new on a DOTD quite cheaply.

The bracket on the WG can had to be trimmed significantly. You can see below how the position of the nipple relative to the bracket is wildly different. Thus, the new one is rotated appx 90° CCW (viewed from front) relative to the old, necessitating the trimming of its welded-on bracket.

I also cut the rod and eliminated the latter of the two bends, causing the end of the rod to be offset relative to centerline. The rod was almost exactly the correct diameter for threading to 1/4-20, so I just ran a die down the ends after cutting, and used .25" threaded hex couplers to re-assemble. (when threading, support the rod in the vise, not the can)

The two together, before modding the new one:




The new can in place, modification of rod is obvious:





Slightly better shot of bracket (this turned out to be hard to get a good picture of):




The holes in the compressor that the bracket now is fastened to were filled with setscrews originally. Just pulled 'em out and replaced with bolts.

No helper springs, and with the MBC she holds a rock-solid 13PSI to redline.

 

Thanks Joe. If this works great....if not I'm welding a external WG to the manifold and I'll be done with this once and for all.

 

One small epitaph- I did this because I too was having problems with boost dropping off with RPM. If it was at 13PSI @ 3.5k, it would gradually drop and by redline be at maybe 10PSI. This can did not (by itself, anyway) solve the problem.

AbeFM gave me the answer, which in retrospect seems blindingly obvious but at the time hadn't occurred to me. I was still taking the WG boost signal from the stock location on the compressor- before the intercooler.

The intercooler is a restriction. Thus, when air is flowing through it there is a pressure drop between the inlet and the outlet. The amount of this drop is not a constant- it rises proportional to the volume of air passing through the intercooler per unit time. More airflow, more pressure drop.

So what was happening is that the WG was indeed holding a constant pressure in the system before the intercooler, since that's where its reference signal was. After the intercooler, the pressure dropped with RPM because airflow obviously increases with RPM. As the RPM climbed and the mass of air passing through the I/C increased, the pressure drop across he I/C increased and this was reflected in my MAP gauge.

Installing the larger can helped somewhat, and it's obviously a beefier unit- it was not cost-burdensome and I'm glad I put it in. But installing a nipple in the pipe between the I/C and the TB and feeding that into the MBC and WG was what really made the boost rock-solid.

 

Coming from you, sir, that means a lot!

 

I'm going to have my bungs welded on my TB pipe soon, is this something you highly suggest? What did you use as a nipple?

 

would you recommend doing this even with EBC?

 

With MS and an EBC, you would be getting your signal post intercoller. The EBC will be working off the MAP sensor for MS, and I don't think any one is hooking there MAP up to there turbo housing.

 

'cept the way a lot of us do it, the MS isn't basing its EBC table off of the MAP sensor, it goes off of the duty cycle targets table, which doesn't read any sensor.

 

I have a funky idea! Forgetting about the wastegate flapper, how big could you port the wastage hole on the greddy turbo? Might be an option to run an external wastgate, but using that hole to feed it.

 

That just sounds obscene...

I used a 1/8"NPT to 3/16" brass hose barb fitting from ACE Hardware. Drilled and tapped a 1/8"NPT hole in one of my pipes and just threaded it in.


Right.

I mean, either way to can tweak it in software- if it's closed loop than the MS will handle it, if it's raw DC then you'll just have to scale the numbers down a bit towards the top. But I think it'd be easier to do with the drive air from a post-IC location, so that there's a linearer relationship between it and actual MAP.

(Is linearer a word? More Linear. Linearer. Yeah, I like it.)

 

I got a free can off a turbo from a VW 1.8t. I'm gonna cut the bracket and weld and rig it the best I can to get it to fit. I have no idea if the threads are going to mate up but we'll see. Worst case scenario it'll fail to open and I'll blow the motor.