Larger WG hole = Shorter rod length?


May 28, 2001
I put on a new TA49 this last weekend and have been taking it pretty easy, but today I had to let it loose.

I have the WG rod set to what, on my stock turbo, would have been around 17 lbs....but the TA49 wrapped up to about 15 lbs.
I put on a Mike Smith ported elbow w/ 1 1/4" puck....the John Craig TA49 came with a 1" dia. WG hole. would take more spring preload on the WG actuator with the larger hole. More area with the larger hole give greater force to overcome.

So I think I'm OK....just wondering if anyone else has noticed this when changing to a turbo with a larger WG hole.

The main reason I ask is that during the turbo change-out I also changed plugs and noticed I've developed the dreaded driver's side header fun...I'm hoping that the cracked header isn't the reason. It seems to spool fine :)

I just put on a TE60 a while back and noticed the same thing...haven't solved it yet, so I'll be watching to see what answers you get.
Yes, a bigger wastegate hole means you will waste more exhaust and therefore need more spring pressure to keep from having the wastegate open up. Shorten up the rod and everything should work out fine.

You definately should get that DS header fixed ASAP. It wreaks havoc on tuning the car otherwise.
That is the number one reason I tell people not to port their stock turbo exhaust housing when they buy a big puck THDP or Mike Smith Elbow. They are all gung ho to port stuff, then go to the track and the car slows way down, so they blame the THDP or the ported elbow, when its the enlarging of wastegate hole that made the difference (not everyone has turbolink with boost recording capability or go to the track as often as some of us, so they never realize that the max boost has dropped 3 psi or so)

I'm going on 6 years telling people not to do this unless they are running a much larger turbo. Even a TA49/TE44 can get by with smaller than a 1" hole if its radiused on the inside for more flow. Opening up a stock turbo to THDP puck size ruins an otherwise semi-valuable exhaust housing (they aren't making any more of these).
Well UNGN....

I wouldn't really say that the exhaust housing is ruined. I'll just need to put a few more turns on the WG actuator rod. And if it isn't enough I can always go with a "heavy duty" actuator.

I was going on the advice of Red Armstrong and John Craig....I think they know a few things about these cars.

From talking to John Craig, the Garrett .63 housings are available....they're just VERY expensive right now. The PTE .63 housings are plentiful and more reasonably priced.

c&'s not really that you waste more exhaust with the bigger WG hole/puck. The larger surface area creates a greater force on the puck....more square inches X lb/sq in = more lbs of force....therefore the WG actuator spring must have more pre-load (more turns on the rod).

Now once the WG opens....yeah the larger hole will relieve the pressure quicker (~wasting~).

I just noticed the header crack this last weekend and I'm trying to line up a spare header to do a "quick change" soon. Racing season is upon to get it ready!

Thanks for the help,
Originally posted by OKTurbo
Well UNGN....

I was going on the advice of Red Armstrong and John Craig....I think they know a few things about these cars.

John Craig doesn't avocate wholesale opening up of the wastegate hole. He does a great job of putting sweeping radius on the inside of the hole so a smaller hole will flow as much air as a larger hole, without having to add four turns to the wastegate rod. There are others out there that bore a large, straight sided hole in the housing to just under THDP puck size, deburr the hole a little and call it good so they can sell you a HD actuator when you use the the entire travel of the stock actuator just trying to achieve a decent racing boost level. I'd rather people not buy things they don't need because they did things they didn't need to do.
Yeah...I'm with you UNGN.

In my case I didn't know any better (no excuse). The turbo was ordered from John Craig thru Quad Air. I let Red take care of the details after I told him what I was after.

The hole is straight cut 1" taper to it at all.

Oh and learn. I haven't had it on long enough to know if it will be a "problem". WG actuators aren't ~that~ expensive.

There are a million ways to skin a cat.

The hole was probably opened up a little larger to allow you to run higher boost levels without creep.I agree with UNGN,radius the inside of the hole [BE CAREFUL of the outside mating face].
You didn't mention what A/R your new exhaust housing as opposed to your old one?
Use some form of grainger valve or bleeder in combination with the actuator....don't tighten the rod as much and you will have crisper control and avoid the problems of creep that come with too tight a spring. Lot cheaper than a hd actuator that may not offer as low a boost as you would like for the street.

Should I use the bleeder set-up with the stock solenoid or eliminate the solenoid (chip control) and just use a bleeder.

I have a friend who just removed a bleeder set-up from one of his cars (ATR I ~think~). It's a small valve with a vernier scale knob looking thingy....don't want to get too technical :).

He might let me have the old bleeder set-up to try out.

Or would using the BstC from Ramchargers/Modern Musclecar be the better set-up?

You can try it either way.....I have done it both ways in the past.

The BstC is neat but costs more money....with one solenoid, it has limited range.....I guess you can use a bleeder with it to move the boost curve up or down, or run dual solenoids.

I would try borrowing your friends to see if that gives you what you can always spend more later if you want to. :)