Well I just finished installing my new wastegate arm, wow, what a difference! With the stock setup, the arm that the actuator controls is the same length as the arm inside the turbo that moves the actual gate. With my new longer arm, my actuator has about double the mechanical advantage over the gate as it did before. Immediately when I took it out I could tell the difference, Boost pegs to 13-14 psi (2-3 over stock) and levels off around 9lbs (1-2 over stock). Tomorrow I'm going in to try relocating the MAP/AIT sensors and possibly toy with the MAP resistors as well and maybe even some more optic tweaking. I'll post pictures/results tomorrow aft.

The boost guage don't lie.


TDG, I'm watching for those pictures.

Well I just finished installing my new wastegate arm, wow, what a difference! With the stock setup, the arm that the actuator controls is the same length as the arm inside the turbo that moves the actual gate. With my new longer arm, my actuator has about double the mechanical advantage over the gate as it did before. Immediately when I took it out I could tell the difference, Boost pegs to 13-14 psi (2-3 over stock) and levels off around 9lbs (1-2 over stock). Tomorrow I'm going in to try relocating the MAP/AIT sensors and possibly toy with the MAP resistors as well and maybe even some more optic tweaking. I'll post pictures/results tomorrow aft.


PICTURES, PICTURES and where did you get that longer arm @?

So, if you were running a softer spring on a home-made turbomaster, you could compensate by lengthening the wastegate actuator arm?

Just to make sure I undertand WG operation correctly:

With no vacuum and the arm not pulling, exhaust gases will blow the wastegate closed and give you more boost (before tripping an overboost code). The vacuum and arm only serve to open the WG and drop boost. Is this right?

Doug

Just to make sure I undertand WG operation correctly:

With no vacuum and the arm not pulling, exhaust gases will blow the wastegate closed and give you more boost (before tripping an overboost code). The vacuum and arm only serve to open the WG and drop boost. Is this right?

Doug





Nope, I think you got it backwards. Vacuum draws the wastegate closed. If no vaccum, then the wastegate is open to dump all the boost.

The control arm and actuating arm are same length - lengthening control arm provides more control force.


Vacuum is digitally regulated to 'bleed' exhaust gasses thru wastegate - oem limit is ~7-8psi Boost.


Lengthening arm may help some, but PCM will set Wastegate Duty Cycle according to measured Boost pressure.


Final controlling limit is Intake Air Temperature - ~240deg PCM will reduce WG DC, then fuel rate.


With any kind of load - hauling, towing, etc - IAT zips up over 200deg in a flash at 10psi Boost and up.


Necessitates some method of charge air cooling if you're gonna work the truck.Edited by: gmctd

Vacuum is digitally regulated to 'bleed' exhaust gasses thru wastegate - oem limit is ~7-8psi Boost.


Lengthening arm may help some, but PCM will set Wastegate Duty Cycle according to measured Boost pressure.


Final controlling limit is Intake Air Temperature, ~240deg - PCM will reduce WG DC, then fuel rate.


TDG,


PCM relates boost/IAT to fuel, or it wouldn't cut back WGDC and fuel in this feed back loop. My theroy still stands that when you resist baro and MAP sensor, more fuel is possible because you've tricked the feedback loop into allowing it.

PCM cuts back WG DC to reduce Boost.


If wastegate or solenoid is stuck, or someone has defeated Wastegate Solenoid function, PCM will then cut fuel to reduce Boost at high IAT.


Safety rules.....

Well, first, i want to make a correction on my first post, the boost does spike up to 13-14 psi but after it all got settled in I guess, it sustains about the same boost as it did before, which is to be expected. Well, I couldn't leave it at that after having spent over an hour making my new WG arm, so I made a trip to Radio Shack and got a 10K ohm linear Pot (http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=271-1715) and wired it up with some speaker wire I had in the truck, in their parking lot no less. I must say, this is the COOOLEST mod I've done yet! Cruising down the highway and you can literally dial the boost from 5-10 psi with the cruise set on 70! No codes, not even starting with the Pot. set on full, its great! I just have to shorten the shaft a little so I can mount it on the dash. Wiring a 10k ohm fixed resistor should certainly make the same results, but me, I'm a guy who likes all the knobs and switches I can get my hands on, and turning a dial and that makes the boost gauge climd, c'mon, who could turn that down?


I was pretty sure before I started that I was going to use a throttle lever for the new WG arm. I had to pick through several of them to find the one I wanted and came up with one off an old Roosa Master used mainly on the Shut-off side. Its about 3" long, the first 1½ is where I drilled my hole to bolt it up to the old WG arm, then it had a 90 deg bend outwards and another back to straight making it ½" off- set but still parallell. I mocked everything up on another GM-4 at the shop. This made the new Actuator connector sit further out away from the turbo than before, so I had to flip the actuator arm so the hitch was pointing outboard and run the actuator on the inside.


I'll get those pictures up as soon as the wife brings the truck back ;)Edited by: Texas Diesel Guy

You can pick up some additional efficiency by upgrade from -4 to -5 or -8 turbo - the compressor and turbine housings were both improved in flow characteristics over the -4.


The -8 got longer wg shaft bushing, due to early shaft binding failures in the -5.


Other than that, they're identical, and the -8 exhaust elbow, with the longer bushing\shaft assy, bolts up the the -5 turbine housing.


You'd probably see more gains in a heavier or working truck, but every little bit helps.......

Yeah, the GM-8 is a little better I'll agree with you there, I've never seen a 5 though. 8 would be a rather expensive upgrade, the whole exhaust housing is different, wastegate moved back a little bit, vertical mount actuator. I'm really happy with the way my GM-4 works, I'll see how it does with the Flowmaster Downpipe and Crossover.


Edit: Oh wait, the 5 is the one thats pretty much Identical to the Gm-8 right?Edited by: Texas Diesel Guy

-5 is identical to -8 but for wg shaft\bushing length.


Turbine wheel and shaft, bearings, labyrinth seals, and compressor wheel all identical -4 thru -8.


Pick up a bad -5 or -8, put your goodies in it and go.


No difference in mounting or downpipe attachment - just lower exhaust pressure, better conversion of velocity to pressure in the compressor.


More efficient.

I know one thing, you can't put the rotating center assembly from a 4 and put it in a 5-8 or vice verse. the center assembly circumference is slightly bigger on the 5-8. I tried and it didn't quite fit.

In techno-speak, the center casting with rotating parts is called the cartridge, and you are correct - no way will the -8 compressor housing fit the -4 diffuser flange.


And versa visa.


-8 exhaust elbow will also not fit -4 turbine housing, technically called the 'snail'.http://www.dieselplace.com/forum/smileys/Wink.gif

Well, here they are, not the best quality but you should be able to get the idea.


http://www.dieselplace.com/forum/uploads/48D_DSC00008.jpg


http://www.dieselplace.com/forum/uploads/77E_DSC00006_edited.jpg


http://www.dieselplace.com/forum/uploads/CBD_DSC00004_edited.jpg


http://www.dieselplace.com/forum/uploads/5C9_DSC00007_edited.jpgEdited by: Texas Diesel Guy

I think daylight would help. I can't tell what I'm seeing.


Nevermind, I see that it's a longer arm on the WG.Edited by: quantum mechanic

allright TDG, Now where did you come up with that setup. Homemade ? you like how it works better?

Homemade, used throttle lever, and I"m very happy with it, it really gives the pot I added a very well graduated adjustment.