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Old 08-27-2021, 09:32 AM   #21
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Join Date: Apr 2013
Location: Colorado
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Year: 1993
Coachwork: bluebird
Engine: 5.9 Cummins, Allison AT1545
Rated Cap: 2
wastegate and afc use the same boost reference line.

i have no boost gauge, so today i hooked up my air compressor with its cheapo air regulator.

the afc was set to full fuel around @ 20 - 35psi
the wastegate opens @ 15-20psi

i loosened the spring some more on the afc, i can hear it travel out now at 15psi.

i killed my battery last night (left lights on) so its on the charger now, but i think im close.

fingers crossed.

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Old 08-28-2021, 08:28 PM   #22
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i had my turbo and exhaust manifold off in 2017. at the time, i thought the wastegate was fixed and didnt think twice about its setting. apparently i can adjust the tension of the spring by adjusting the length of the arm. i am certain i chnged the setting.

on the vehicle, adjusting that arm looks very difficult.

when the exhaust manifold was off, it was for an extended time because of a broken bolt. i'd rather not go down that path again.

another option would be to separate the afc and wastegate air lines. leave the original line going to the afc and install a boost elbow for a reduced pressure line for the wastegate.

there is a threaded bung in my charge air tube above the turbo that i think i could install one of those boost elbows. that would give me a lower pressure reference line for the waste gate just above the turbo..

dissasemble the exhaust/turbo and adjust the setting? or get an air fitting and a few feet of hose?


in my head the elbow and hose is the quick fix.

how open is a waste gate at WOT?

comparing pictures from 2017 to now... the wastegate area is sooty now. i think its open too much.

since all i do is WOT on the highway, whats a cruising boost pressure?
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Old 08-29-2021, 09:08 PM   #23
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because its the weekend, instead of ordering parts... i pulled apart my turbo.

the waste gate came off after a couple of busted knuckles. its tight quarters, as it is sandwiched inbetween the turbo and the engine block. 2 nuts and clip, and i had the waste gate off.

i sat down with the air compressor and adjusted the waste gate.
it was fully open around 15psi.

i shortened the arm, which preloaded the spring inside the diaphragm. i had seen onthe internet that a turn of the arm was equal to about 3 psi. down 10psi, i started with 3 turns and tested on the compressor. the compressor still opened the wastegate early. i tightend more, it got better, finally, after maybe 7 or 8 full turns onthe arm, the waste gate stayed closed until after 20psi. fully open @25psi.

i put it all back together and took it out for a spin.

power was good, a little too much smoke.

egt's were down!! big time.

wot on flat ground was in the 10's, on my hill it only got into the 12's.
top speed was about the same 67-68
it still slowed quite a bit climbing - i crested the hill at 63.

lots of power.

i could stop now... maybe it'll sit for a few days while i think about it.

its still smokey low - maybe adjust star wheel again and back off smoke screw.
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Old 08-31-2021, 10:59 PM   #24
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i got boost!

no clue how much. guessing 25-30psi range. cummins says the factory wastegate was 22psi. i've got an extra twist on the spring after what i thought was factory.

she's got power, space shuttle like!

egt's are down! wot - 11, cruising @ wot 8-9, hill climb 11-12.

less than wot had egts in the 3 and 4s. its running cool!

top speed is about 67... no change

i can hear the turbo whine loud and clear. thats a new sound.

going to try these settings for a bit, wil track fuel and see if its changed from the mid 7's mpg
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Old 09-01-2021, 12:38 AM   #25
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good to hear

Now that you have more air, you are likely to have to tune in the fuel pump to match the air supply again....


test and tune make a change test and tune, make another change, test and tune

gets to be a drag, but when you stick with it, you make results

more air means you can burn more fuel even when at part throttle... now keep the speeds to 55 mph and then check mileage at 65 mph and see what kind of difference you see

cheers

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