This is a modification to try to keep boost under control when using a 12 or 14 cm wastegated housing on an engine that really needs a bigger turbo. I don't want a bigger turbo because I run empty in heavy traffic most of the time and I want all the spoolup I can get. I don't want to grenade my little turbo into the engine by overboosting it, though. The problem I was having was that the turbo would make 37 PSI with the wastegate wired open! This is because the wastegated housings only wastegate the rear 3 cylinders. I don't wanna know what the EGT in the front 3 looked like at 37 PSI.

Anyway, I had a spare housing laying around, so I pulled off the backplate and drilled a new port into the front scroll through the original wastegate port. Like so.

I was a little concerned that this would hurt spoolup due to pressure pulses being able to pass through the new port instead of having to go past the turbine at high velocity.

Results: I can't tell any difference in spoolup. Boost is back under control. EGT is still high at high RPM, but I'm no longer concerned about grenading the turbo. I think it's time for water/meth injection...

2 more pics in my gallery.

 

looks good. you can go bigger on the holes too.

Forrest

 

WANNADIESEL,
I may be way wrong but wouldnt cutting the divider out of the inlet side of the houseing have the same effect? The reason I ask is because I have a 14 wg that I was going to cut the divider out of for the same reason you drilled yours.

mooseman

 

Forrest - Yeah, I could have gone a little bigger, but I didn't think that would help much. I'm at 13/16" right now (stock was 3/4"), but I think the flow restriction point in the wastegate is how little the flapper valve swings open. It only opens about 1/4" before it hits the backplate. Making the ports as large as possible didn't seem to be worth the effort.

Moose - Yeah, you could cut out the divider. I thought about it, but I decided that this way would be less disruptive to the normal flow through the scrolls when the wastegate is closed. Also it seemed like a lot of work. I think if you cut the divider back about 1/2 inch from the flange and blended it smooth (think leading edge of an airplane wing) that would give good results. Kind of the same thing as a notched plenum divider in a dual plane gasser motor - give up some bottom end for better top end, keep good midrange. At least that's how my brain works.

 

Dave, since I talked to you about this mod I realized that the Banks Big Head wastegate and housing uses the same method to run the wastegated exhaust from all six.

 

Well, there's at least one part from Bank$ that's not a waste.

I'm pretty happy with the results, I wasn't expecting much other than to regain control over the boost. The more I read about water/methanol injection the more I think that's the answer for me. Keep the little turbo for good performance in dense traffic, but have the water/meth to cool things down when blasting up hills out in the country. There's just nothing like hitting the bottom of a long hill at 45 and romping on it - planted in the seat all the way up, back off when the speed or the pyro scares you.

 

looking good dave! works well huh?

 

oh yeah, my thinking behind going with 15/16" was that more surface area (on the flap) would make for easier opening. i'm no mathematician, so i don't know if that is actually different than your set-up.

 

Hadn't thought of it that way. 13/16" was the biggest metal bit I had that would fit the drill press. The TurboMaster opened just fine with the stock setup, the only problem was it was only wasting the rear 3 cylinders. I was thinking something was screwy with the TurboMaster until I wired the wastegate open and went for a ride. Slow spoolup but it still made 37 psi on the top end.

Have you got your wastegate working yet? I have another can if you'd like it. Or buy a TurboMaster from Bill Heath. This is the second time he's sent me an install kit so I could swap housings and he still won't let me pay him.

 

i'm sure it works fine. but i haven't had a chance play with it since right after that discussion a BRAND NEW exhaust valve spring broke. that's all i'm going to say for now as it is still getting resolved. waiting on some parts from cummins before i can get 'er running again.

 

wannadiesel, I did this to my 12cm housing awhile ago, drilled both to 13/16". I can't tell a difference in spoolup vs. stock. It did help with EGT's though, can still get high but seems to take longer to do so.

I wonder if the housing backing plate could be notched so the wastegate can open a bit more? I was also thinking of putting on a bigger flapper door 1 1/16", and drilling the holes to 1".

 

yes, and yes... you can get a bigger flapper off another turbo and bore the hole out even bigger. just make sure it'll clear the inner wall of the housing. the larger you bore thehole, the less shrouded it'll be against whatever size flapper you have. 1/16" seat should be fine. but you need to make sure the flapper can't move around on the arm. seen that before on an old housing. had to weldup and re=drill thearm tomake the flapper tight again.

Forrest

 

As far as the flapper hitting the backing plate, couldn't you make one that allows the flapper to open farther? Ex. a "Bubble" in the plate, or something like that?

Just throwing things out

Chris

 

yes, you could.

you guys should see the turbos on the old GM 6.5 diesels... HUGE wastegate orifice, and the elbow is shaped to allow the puck to swing WAY out.

Forrest

 

So is it best to drill a hole instead of cutting out the divider. I can do either but I just wana do whats best.

Mooseman