someone explain boost!!?? - Diesel Truck Forum - TheDieselGarage.com
Thread Details Posted by dangerous196, this thread has received 9 replies and been viewed 1081 times.

 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old 05-21-2007, 12:57 AM Thread Starter
 
Join Date: Dec 2008
Posts: 964
Points: 9,390
Thanks: 1
Thanked 1 Time in 1 Post
someone explain boost!!??

Ok So more is better right?! Wrong?? Give me something out there! A stock hx35 is only good to about 26psi after that it's just pumping HOT air?! Can someone explain how 50 plus boost is good and how does that amount get cool enough to be good? Ok to much just the basics please!! Help:shrug:
dangerous196 is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 05-21-2007, 02:33 AM
Super Moderator
 
John_G's Avatar
 
Join Date: Dec 2008
Location: Tyler, TX
Posts: 4,247
Points: 74,701
Thanks: 101
Thanked 407 Times in 347 Posts
NOPE! More is BAD.

What you REALLY want is air FLOW, not boost. Boost is ONLY a measurement of pressure, and doubling the boost does NOT double the flow, in fact it may reduce it if the Charge Air cooler cannot keep up.

Proof? OK.

Take a TD engine, any with a CAC. Increase the pipe diameter, improve the CAC flow (reduce pressure loss) and efficiency. You WILL move more air into the engine, make more power, but have less boost.

More boost also means more heat. You cannot compress air w/o heating it, and the more you compress it the hotter it gets. More heat increases EGTs, so you must REDUCE fuel to keep the EGTs in check. If you moved more air with the same or lower boost, you could INCREASE fuel!

'93 F-250 HD, 7.3L IDI, 5spd - FARM TRUCK
I Support: Trailer brakes an every axle over the towing vehicle's GVW; CDLs for RVers; Safety inspections for ALL vehicles and 6 axle trucks (97K GVW proposal).

Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote - Benjamin Franklin

I vote for LIBERTY!
John_G is offline  
post #3 of 10 (permalink) Old 05-21-2007, 02:43 AM
Senior Member
 
diesel_ram_man's Avatar
 
Join Date: Dec 2008
Posts: 4,158
Points: 50,916
Thanks: 3
Thanked 9 Times in 7 Posts
Images: 6
Quote:
Originally Posted by John_G
NOPE! More is BAD.

What you REALLY want is air FLOW, not boost. Boost is ONLY a measurement of pressure, and doubling the boost does NOT double the flow, in fact it may reduce it if the Charge Air cooler cannot keep up.

Proof? OK.

Take a TD engine, any with a CAC. Increase the pipe diameter, improve the CAC flow (reduce pressure loss) and efficiency. You WILL move more air into the engine, make more power, but have less boost.

More boost also means more heat. You cannot compress air w/o heating it, and the more you compress it the hotter it gets. More heat increases EGTs, so you must REDUCE fuel to keep the EGTs in check. If you moved more air with the same or lower boost, you could INCREASE fuel!
Very good info right there, Thanks for that John! :Thumbup:

-Charley, 1995 Nissan hardbody, single cab,2.4 i-4, 5spd, straight piped - 4.5in tip, 2x Rockford Fosgate R1's

Quote:
"I Caught that diesel thing, now it stings when I pee"
The Diesel Garage.com
Can You Keep Up??
diesel_ram_man is offline  
post #4 of 10 (permalink) Old 05-21-2007, 04:23 AM
Senior Member
 
sstockton's Avatar
 
Join Date: Jan 2009
Posts: 3,514
Points: 69,671
Thanks: 3
Thanked 64 Times in 60 Posts
Right, but sometimes boost is the cheapest easiest way to get more air into the combustion chamber. Like John said, it would be better to get increased air into the combustion chamber other ways, I.E. A cam which will keep the valves open longer allowing more air to enter the combustion chamber, and or cylinder head porting.

Also like John said, compressed air equals more heat. Air flowing through the compressor housing on a turbo creates pressure in that housing and the pressure then creates heat. Thats why you start building more heat with the hx35. If you do something to reduce that pressure, I.E. change the size of the housing or change the compressor wheel itself, you will flow more air at lower pressure in the turbo. This equates to more flow but cooler air. This air backs up at the cylinder head and creates boost, the boost is still based off flow, The same amount of flow creates the same amount of boost. however, since it wasn't compressed and heated in the turbo itself, the result is cooler boost, therefore cooler air in the combustion chamber. Cooler air in the combustion chamber means more power and lower egt's because of a better more complete burn.

However, everything really needs to be paired right. If you just throw a turbo with a bigger comp wheel and housing on a truck with no fuel mods you will greatly suffer down low. It takes more exhaust to turn the larger wheel and get it spinning fast enough to flow air and produce pressure. When you aren't producing pressure, the engine is relying on Vacuum to draw air into the combustion chamber. If your Air Fuel controller is set up to flow lots of fuel at low boost, when your engine is starving for air before your turbo has spooled, it smoothers the flame, too much fuel, and not enough air to burn properly. This leads to smoke, low end heat, and can cause excessive ring wear as well. Also when you smoother the flame down low, it becomes harder for the truck to build RPM, lower and slower RPM building leads to more lag, and it just takes even longer for everything to get to be where you want/need it to be to work properly.

Thats why, with a larger turbo on the truck, I'm not a huge fan of running the AFC loose on a mechanically injected truck, or unplugging the map sensor on something like a 24v. Full fuel with no boost isn't the best thing in the world.

There are a lot of things that go into picking the right turbo(s) for your truck, and fueling and Tuning must be matched accordingly. Its easy to build a truck that puts out decent numbers, but its hard to make a truck that puts out big numbers and still functions well all around. Egt's, spool up, reliability, driving manners and of course the power you want.

Hope this helped a little. Sorry if it was disjointed, please feel free to correct any mistakes that you find or ask if you want a little clarification
Sean

2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.

TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)
www.totalperformancediesel.com
sstockton is offline  
post #5 of 10 (permalink) Old 05-21-2007, 04:27 AM
 
Join Date: Dec 2008
Posts: 687
Points: 2,918
Thanks: 2
Thanked 2 Times in 2 Posts
Damn son, thanks even though I didn't even ask the question
ckbed is offline  
post #6 of 10 (permalink) Old 06-02-2007, 07:14 AM
Senior Member
 
sstockton's Avatar
 
Join Date: Jan 2009
Posts: 3,514
Points: 69,671
Thanks: 3
Thanked 64 Times in 60 Posts
Quote:
Originally Posted by ckbed
Damn son, thanks even though I didn't even ask the question
No problem, I hope its useful information.
Sean

2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.

TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)
www.totalperformancediesel.com
sstockton is offline  
post #7 of 10 (permalink) Old 06-02-2007, 12:22 PM
Senior Member
 
Join Date: Dec 2006
Posts: 326
Points: 18,179
Thanks: 0
Thanked 0 Times in 0 Posts
ok help me out with this. I'm running a hx35 stock fuel plate star wheel forward waste-gate plugged is this going to be harmful to my valves in the long run.:shrug:

96 ccab 3500 4x4 5.9 12valve dually. daily driver. afc forward, star wheel all forward. KDP done!!!:Thumbup:BHAF!! 2cycle additive. next up: #0 plate- injectors, timing and TC some day!!!
R-muck is offline  
post #8 of 10 (permalink) Old 06-02-2007, 05:23 PM
Senior Member
 
sstockton's Avatar
 
Join Date: Jan 2009
Posts: 3,514
Points: 69,671
Thanks: 3
Thanked 64 Times in 60 Posts
Quote:
Originally Posted by R-muck
ok help me out with this. I'm running a hx35 stock fuel plate star wheel forward waste-gate plugged is this going to be harmful to my valves in the long run.:shrug:
Its hard to say what boost you're pushing, but you have nothing to be concerned about. All that sliding the AFC and star wheel is going to do is increase low boost fuel. Without a plate and injectors you don't really have to worry about smoother the flame down low, you don't have that much fuel. Also you aren't even close to being out of the compressors map up top without a plate. That isn't that much pressure on the valves on either side of the equation either, intake or exhaust. If you were running a lot higher boost, and therefore drive pressure, I would start thinking about the exhaust valves.
Sean

2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.

TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)
www.totalperformancediesel.com
sstockton is offline  
post #9 of 10 (permalink) Old 06-19-2007, 06:12 AM
Diesel Mafia #67
 
blackcloudCTD95's Avatar
 
Join Date: Jun 2006
Location: jensen beach fl
Posts: 11,283
Points: 69,457
Thanks: 257
Thanked 202 Times in 153 Posts
Now me on the other hand.. with DV's injectors and FP.. and running no W/g I EASILY saw 42 psi.. and that was waisted power.. I was off the compressor map I think the compressor map stops arround 32 psi..

Jordan

95-dodge 2500 built to the hill... - sold to litle brother
03- stroker 6.0 studs and basic BS

blackcloudCTD95 is offline  
post #10 of 10 (permalink) Old 06-19-2007, 06:54 AM
Senior Member
 
sstockton's Avatar
 
Join Date: Jan 2009
Posts: 3,514
Points: 69,671
Thanks: 3
Thanked 64 Times in 60 Posts
Quote:
Originally Posted by blackcloudCTD95
Now me on the other hand.. with DV's injectors and FP.. and running no W/g I EASILY saw 42 psi.. and that was waisted power.. I was off the compressor map I think the compressor map stops arround 32 psi..
Yeah, after 32psi, you just start building hot air, and increasing EGT's. If you have enough fuel to push significantly past 32psi, or essentially enough fuel to spool a bigger turbo, get one.
Sean

2000 2500 reg. cab 4x4 auto 577hp
09 6.7L QC LB stick, 4x4.

TOTAL PERFORMANCE DIESEL 707-545-FUEL (3835)
www.totalperformancediesel.com
sstockton is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Diesel Truck Forum - TheDieselGarage.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome