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why am i only boosting 23 psi boost

3K views 17 replies 7 participants last post by  FIRESTARTER 
#1 ·
hey guys i just wanted alittle pointers. ive searched and read alot of posts . this is what i have and done so far. 1994 dodge cummins 2wd manuel trans. i have ground the fuel plate to a #100 , did the washer mod, turned my star wheel in bout 8 turns and turned the smoke screw in about 1.5 turns. i also have a boost elbow. i have the screw turned all the way in on the elbow which should give me full boost, but im only getting about 23 psi on the topend and the most 950 degrees on my egt. any ideas ?
 
#2 ·
Do you hear any air leaks at boost? Make sure your intake boots are intact and not cracked, also check your intake horn gasket.
 
#3 ·
hey, finally some one close to me.. im only like 10 mins from you.

what kind of guage are you running? i had a guy check out my truck and he said it spools up great and that my boost sounds fine. my guage shows 23psi also. ive checked all my pipes for holes and cracks.

whats the intake horn? i'll have to check mine
 
#4 ·
I have a glowshift 3 in 1 gauge with pyro, boost, and tranny temp.

The intake horn is the pipe on the driver's side that connects to the engine, the oil dipstick is connected to it. My gasket is blown out completely on mine and I hit 22psi at most at lockup in 4th gear.
 
#5 ·
I would check the fuel plate and make sure its not so far forward that its stopping rack travel. It happens sometimes then you grind your own plate or buy an aftermarket plate. Slide it half way and see if it helps. If it was that big of a boost leak, your exhaust temps would be astronomical. My 2 cents.
 
#6 ·
that can happen? have the fuel plate to far forward? let see if i understand the diesel concept. am i correct that fuel affects boost? or are they not affected by each other? like if i have too much it will affect how much the truck will boost. another question is could it be that i still have my stock govener springs that i dont have enought rpm to get more boost ?
 
#7 ·
Ya you got it right having the plate full forard for more power. And the more fuel generally speaking the more boost you get. all im saying is to check and make sure that the arm inside the pump isnt getting caught on the bottom of the plate. If it is, then there is no rack travel, which means your truck is getting no extra fuel and there for not reaching peak boost. the lack of fuel also explains your low egt's. the best way to see if the arm getting caught is the cause is pull out your plate out (temporarily) and see what kind of boost numbers you get. or just slide the plate back a little and see if you get more power. if you do then it was the arm being stuck. Ive had this happen on 2 seperate trucks i've tuned.
 
#8 ·
ok so all i need to do is remove just the plate nothng else and put it back together and take for a test drive. it smokes pretty good now but like i said its not getting alot of boost.ill try that and let you guys know.
 
#9 ·
Well I would take it out. Drive it and see of your boost goes up, then put it back in.
 
#10 ·
oorrr, you could back the boost elbow off a little and watch it go up. loosen the adjustment up. that should make you happy.

rande
 
#11 ·
Unhook your wastegate and slide your plate to the front of your afc. With a hx35, you should be looking for 35 psi.

BTW, where is your egt probe
 
#13 ·
With a disabled wg and stock plate all the way forward, I was hitting 25psi, cut it to a 0 and it went up to 35.

Disable your wastegate and make sure your plate is as far toward your injector lines as possible.
 
#14 ·
if you're only hitting 950 degrees there is fueling problem. with an #11 plate I could wrap a pyro and hit 35 PSI a once. I ran no plate for a while...and, well, lets not talk about that :p

did you make your own plate or buy it?

if you made it, did oyu polish it??

I bought an ebayokate when I first got my truck and after about 20k miles of driving it when I went to no plate I saw a groove where the rack arm was hitting hte plate and NOT riding up..explained why I had less power up top than I thought I should...

I would take the plate out and test it that way as stated, look for nay marks on the plate to show consistent hitting and not moving. either way, I'd polish it til its shiny and smooth on the forward face.

The best way I figured to tune with a plate is take the cover of, fire the truck up (running DOES make a difference where the rack strikes), and throttle pop it until it hits as low as you can go on the plate.
 
#15 ·
when i bought and installed my elbow it is/was set for 35# of boost. i'm thinkin that if you adjusted it all the way open you might have gone past the adjustment point. i like to start with the easy stuff first. good luck to you.

rande
 
#16 ·
ok heres i have found since last post. i backed the boost screw out about half way , didnt help. so i removed my afc housing and inspected the govenor lever and with the lever moved to the on postion it wasnt hitting the fuel plate at all . there was no signs of any contact on the fuel plate. so i moved the fuel plate back toward the firewall til would hit when moved forward and not go under the fuel plate. gotta test drive and see what happens now.
 
#17 ·
well took it for a test drive and had just a tick hair more boost and hit 1000 degrees . could it be that the stock govenor springs are holding me back? its like its hitting a wall and thats all its got. can some tell me what exactly does the star wheel do ?i think i read some where that the tigher the star wheel is the more boost it takes to move it. is that right. why would you want to turn it all the way in so its really tight?
 
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