Could someone please explain to me why I lost 2lbs of boost

[lpearson]

I just put on a new AFE Stage 2 air system and my boost pressure went down from 36 to 34. I guess I don't understand. I didn't do anything else. What gives? I thought more air would increase boost. Anyone got an answer?



Thanks,

Lowell

 

[ndurbin]

I also lost 2 lbs. of boost when I installed mine. Went from 26 to 24. I made sure all boot connections were tight.

 

[Huff N Puff]

There are alot of causes for a loss of boost

Start with leaks on the intake side and the exhaust. Dirty oil can slow down your turbine. Injectors not working properly,dirty air filter or dirty fuel filter,poor primary fuel delivery,e. g. lift pump. Those are the simple issues,the complcated ones are sensor or computer problems,and even transmission issues such as slightly slipping transmission components,Good luck,hope its dirty oil. Merv

 

[lpearson]

Re: There are alot of causes for a loss of boost

Originally posted by Huff N Puff

Start with leaks on the intake side and the exhaust. Dirty oil can slow down your turbine. Injectors not working properly,dirty air filter or dirty fuel filter,poor primary fuel delivery,e. g. lift pump. Those are the simple issues,the complcated ones are sensor or computer problems,and even transmission issues such as slightly slipping transmission components,Good luck,hope its dirty oil. Merv

My stock box with a K&N equalled 36lbs of boost. All I did was change to the New AFE. All connections are tight and lined up and went right out to test my new toy. --------and lost two pounds somewhere. Have done 4 test runs at WOT, same results. No question it's the new air box.



Injectors are new EDM's, you can eat off my engine ( I'm a clean nut); filters are almost new, oil is new synthetic. Sooooo I don't think any of these are the issue.



I called AFE today, ----- just now got a call from them back (Eric Griffith) and he's checking into it. I feel better already. He said in a couple of days he would call back. I'll post what he says.



Lowell

 

[RankRam]

I will take a stab at this.



Boost equates to the amount of work that the engine is doing to do a certain task. My thought is that with the improved airflow the engine is not working as hard to do the same task.



If you hooked up good load I would think the boost would be the same with each intake set up.



Does this make sense to any one or am I just blowing smoke? So to speak.

 

[Big MAK]

You're getting better fuel burn with the larger air charge. Less work to get the same power. Put a heavy load behind it to see where the real max is at under any condition. imo



If your max boost is less when pegged out towing a hill with a heavy load; then I'd start looking for a culprit ---- unless you simply ran out of fuel to burn.



You may simply be blowing less fuel out your tailpipe.

 

[RustyJC]

We really need the head/flow performance curve of the turbo's compressor impeller to answer this. Generally, for a given drive gas horsepower on the turbine side, if airflow goes up, head (discharge pressure minus suction pressure) will go down. This may explain your loss of boost.



Rusty

 

[Dennis Garrett]

The airplane pilots out there know about "density altitude". It affects wing lift and propeller preformance in aircraft. On cool, low humidity days, oxygen molecules are denser & closer together, making propeller bite & wing lift more pronounced. Just the opposite, warmer, moist, high humidity air has oxygen molecules that are further appart, and not as dense or oxygen rich. Wing lift & propeller bite suffer, making longer take off runs. The same should affect the turbos on our trucks, you should see a little higher boost on a cool dry day, a little less on hot humid days. The difference can double the take off distance on a small plane.

 

[britannic]

Although the boost went down, did you lose any power? If not, it may be that the AFE is more efficient and the air doesn't get as hot through the compressor, so that the intercooler can remove more heat and hence the 2lb drop - just a theory of course...

Originally posted by lpearson

I just put on a new AFE Stage 2 air system and my boost pressure went down from 36 to 34. I guess I don't understand. I didn't do anything else. What gives? I thought more air would increase boost. Anyone got an answer?



Thanks,

Lowell

 

[snowracer69]

britannic took the words outta my keyboard.



While Dennis makes some good points about density altitude (and I see EVERY ONE of those points while both flying (PP, ASEL, IR) and being highly BOMBed at high altitude with high temps... . I can't stop this thing from smoking right now w/ ambient temps at 75*F+) I don't think they're playing a roll in your boost.



Remember, your boost gauge is refrencing against atmospheric pressure, hence "gage pressure"... it's not an absolute pressure gage.



Josh

 

[lpearson]

I am trying to understand the posts here.



So, you are all saying that it's a good thing that the boost pressure went down because of more air.



Anyway, thanks for the thoughts.



Lowell

 

[lpearson]

Originally posted by ndurbin

I also lost 2 lbs. of boost when I installed mine. Went from 26 to 24. I made sure all boot connections were tight.

Curious, did you lose any performance after the new air system?



Lowell

 

[RankRam]

Originally posted by lpearson

I am trying to understand the posts here.



So, are you all saying that it's a good thing that the boost pressure went down?



Performance is the same, drives nice, no problems there. Just the boost question.



Interesting note: I thought that higher boost presure = more H. P.

I get a hight volume air system, boost goes down, but performance doesn't.



Anyway, thants for the thoughts.



Lowell

Yes it's a good thing!



Your truck is not working as hard to give you the same amount of performance.



I really believe you will get the peak boost you saw before the air mod when you subject the truck to a good load pulling.

 

[dpuckett]

I hadnt thought of it applying to the intake side of things. When I went from my 12cm housing back to the stock 18, I lost about 6 psi boost, but actually GAINED a little sit-me-back-in-the-seat, or it seemed to. Didnt lose anything for sure. I'll have to mull over this losing boost when increasing airflow. I'm no physicist, but I may be able to figure something out, and reword it.



Lower boost IS good. Boost is resistance to airflow. That is why you will frequently lose boost &/or lower EGT with a ported head, or other airflow improvements, but GAIN power. Did your EGTs go down with the boost loss? The freer you can get stuff in and out, the better off you are, even if the numbers arent as impressive. WE know what they mean with this or that mod.



Daniel

 

[ndurbin]

No I didn't loose any performance. I also put a straight pipe in at the same time. The truck seems to like it alot better, and sounds a helluva lot better. Just might have to put the silencer ring back in since the turbos so loud now.

 

[Forrest Nearing]

if you put the silencer back in, I'll bet money you'll take it back out in short order!



(I did! LOL!)



Forrest

 

[ndurbin]

It's not bad with just the truck, but man when I get on it with the trailer behind it gets real high pitched.



Or I could just get some new speakers to drown it out alil. might also help with the drone from the staight pipe too.

 

[R.M.THOMPSON]

You lost your boost due to the loss in ehhaust restriction... Change the intake back to stock and you will lose even more. .

 

[PRout]

I think you guys are just guessing, and dont really know the answer.

 

[mhenon]

TAG / AFE install

One of the first things I noticed after installing the TAG/AFE was while down-shifting. Going from 5th to 4th gear, for instance, it felt like there was no resistance... . almost like you just dropped it into neutral. Can only guess that resistance to air-flow through the intake system has been reduced.

I did pick up 1mpg while towing my TT. This was three days of driving with headwinds every day. My previous average with headwinds was about 11 mpg. This trip averaged 12. 15 mpg. Thats a solid 10% increase over a 1800 mile trip. I just can't believe my crappy luck with the winds though. Going through southern Idaho, from east to west, it was fierce.

These air-flow enhancements really show up when you pour the fuel to it (like towing heavy into a headwind or bombing).



Mike