Boost Numbers with TST

[Big MAK]

Running on 3/3; my max boost is 25lbs; even when towing. It'll momentarily spike to around 30 but immediately comes back down. Just for a test I turned it to 6/4 and I see the exact same behavior.



Towing on 3/3 I see the same numbers. I also noticed that my vacuum gauge dropped to "75% restriction". Perhaps the engine's running out of air???? With an AFE pro guard and intake? Or maybe I can't get the exhaust gases out quick enough... . but I wouldn't expect the vacuum gauge to drop if the exhaust side was the issue. ATS manifold going on this weekend; stacks too if the parts get here; fuel pressure sensor also on order.



I chatted with Mark Chapple and we suspect running out of fuel mighty quick; could be weak pump and will only support that 24lb output.



Other experiences re: boost levels with TST at 3/3 or thereabouts?



Curious about this boost thing; but the TST has been great!

 

[SRadke]

With the stock elbow I can see as high as 38 psi on setting 4:4. Usually levels off at about 35 where the box is programmed for it to do so. If you turn it up to 5 or higher do you see any smoke? Your truck should make close to 25 psi stock I can't imagine not having enought fuel to get it any higher with TST.



-Scott

 

[Big MAK]

That's what I thought. Other then the quick spike my max boost is right where it was stock. I'm wondering if my boost elbow is defective.



I have an adjustable boost elbow from PDR; maybe I should try it? What's a good 'rule of thumb' for the PDR boost elbow -- i. e. starting point setting?

 

[Big MAK]

The elbow I had from PDR was the same elbow except the adjustment nut was turned in about three quarter of a turn more. Put it on. Now on 3/3 max boost holds at a steady 32lbs. Problem solved.

 

[SRadke]

Sounds good except it still sounds like you are short on fuel. I did an experiment with mine where I locked the wastegate open. I found not only an encredilbly slow spooling bottom end but I sill had enough fuel on setting 5:5 to make 40 psi even with the wastgate fully open. Your situation sounds fishy to me.



-Scott

 

[JRMora]

I know this will sound like a dumb question, but does altitude have any effect on the maximum boost developed? I have a stock HO, and the most I have seen is 22# WOT. I live at about 5000 ft above sea level. I realize the purpose of a turbo is to compress the air coming in the engine, but if you start at a lower pressure you won't see as high a peak.



Right?



I see that Big Mak is in NE while Scott is in OR (Close to the coast?) BTW, I did miserably at geography.



I'm curious what boost the guys up in the Colorado "Hills" are getting.



Juan

 

[BillGotthelf]

MAK I just towed my 5'ver last weekend for a long weekend and acclerating in 3/3 I would see 35 psi tops. Only extras on motor is the AFE 7 intake.

 

[hotram03]

I have run mine up to 2/4 and I have seen 43lbs and stays at about 41-42 under WOT. I also run the DD Jammer turbo which is supposed to stop at 40 , so I'm being careful.

 

[SRadke]

Yes Juan, altitude will affect max boost numbers. I live at a relatively low altitude here (about 400 ft. ) but I've traveled a little and seen boost numbers as high as 38 psi at an elevation of 5000 ft. I'm still suspicious of a problem. With a normally programmed PMCR 35 psi boost should be where it levels off and it shouldn't have much trouble getting there.



-Scott

 

[Big MAK]

Thanks for the input; I'm trying to get a fuel pressure gauge installed but I can't seem to get the parts in. I may have to just buy a new pump and have it done with since I don't expect to use the stocker too much longer anyways...

 

[SRadke]

FYI, I put in a pressure gauge and my stocker will supply all the fuel I can burn with safe EGT's and my stock turbo. I can pull it down to about 2 psi but considering it starts at 7 that aint so bad. With a new turbo will come my pusher pump.



-Scott