Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
j930's Avatar
 
Join Date: Aug 2010
Location: Anthem, AZ
Posts: 875
Garage
question about boost

is there a reference book or article that can be read about boost. I am new to turbos and when you guys discuss .6 bar .8 bar 1.2 bar etc. as related to the turbo and what the different levels of bar are resulting in. I am trying to figure out exactly what that means. I have a very basic understanding of how a turbo works but would like to learn more.

__________________
84 930 Slant
15 Sonata 2.0T
08 Ram 1500
15 Ram Eco Diesel
Old 11-07-2010, 07:05 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Banned
 
Join Date: Nov 2007
Location: Rockwall, Texas
Posts: 8,760
Maximum Boost, Corky Bell, (9780837601601) Paperback - Barnes & Noble
Old 11-07-2010, 07:32 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
mark houghton's Avatar
 
Join Date: Jul 2008
Location: Central Washington State
Posts: 3,839
1.0 bar is equivalent to 14.5 psi. Thus, .8 bar is 11.6 psi, etc. Stock 930's have the wastegate set to open at .8 bar. Typically, with some simple (but not necessarily inexpensive) modifications, a person can safely run 1.0 bar by changing the spring in the wastegate, installing a larger intercooler to better cool the air charge, and some means of adding additional fuel on full boost (usually an adjustable WUR). And coupled with some means of monitoring your air-to-fuel ratio to assure final tuning is correct.

There are a couple control things going on with boost. One is the wastgate opening up at the pre-determined spring tension (.8 bar) to let some of the exhaust gas bypass the turbo and stop any additional boost from occuring. Another is the boost recirculation valve (not a true blowoff valve since it isn't blowing off to atmosphere) that opens when you take your foot off the gas to shift. It allows all that under-pressure air residing in the intake manifold (actually, in the intercooler and secondary manifold that is part of the recirculation valve assembly) to recirculate back to the intake side of the turbo, vs. trying to force itself back through the turbo which will put strain on the turbo and cause it to stall...thus increasing your turbo lag. Also, when on boost, your WUR will react accordingly and cause an increase in fuel to the injectors to assure a rich enough mixture to both cool the cylinders and prevent detonation.

More boost pressure = more power, but not without some level of risk if not sorted out correctly. Until you gain more knowledge on these wonderful machines I would recommend staying stock and just enjoying it as-is.
__________________
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 11-07-2010, 09:10 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered User
 
j930's Avatar
 
Join Date: Aug 2010
Location: Anthem, AZ
Posts: 875
Garage
so the higher the bar the longer it stays in boost if I am understanding correctly, and thus giving more air for more power.
__________________
84 930 Slant
15 Sonata 2.0T
08 Ram 1500
15 Ram Eco Diesel
Old 11-07-2010, 11:01 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
mark houghton's Avatar
 
Join Date: Jul 2008
Location: Central Washington State
Posts: 3,839
Quote:
Originally Posted by j930 View Post
so the higher the bar the longer it stays in boost if I am understanding correctly, and thus giving more air for more power.
Not really. The higher the bar, the higher the boost pressure and the more hp the engine can deliver (with proper fueling). How quickly the turbo reaches maximum boost, and how well it can keep up with engine demand and not begin to lose boost is dependent upon the type of turbo and how welll it is matched to your engine build.
Properly functioning, your turbo will produce maximum boost and hold it throughout most of the useable rpm range of the engine.
__________________
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 11-07-2010, 03:17 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
wjfk32's Avatar
 
Join Date: May 2008
Posts: 1,257
This weekend I did some nice top end runs. Weather was approx 53-56F. I was seeing 15psi. I car pulled and pulled..Its amazing what COLD weather can do. Plus I tightened up some bolts by the wastegate and other places where boost could escape.

Its nice when CIS works out and no hickups.

Walt
Old 11-08-2010, 05:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
David's Avatar
 
Join Date: Apr 2002
Location: Houston (Clearlake), TX
Posts: 9,122
Garage
Another good book: Amazon.com: Forced Induction Performance Tuning A Practical Guide to Supercharging and Turbocharging (9781859606919): A. Bell: Books
__________________
2014 Cayman S
2011 Cayenne Turbo
1979 930 (475 rwhp at 0.95 bar)
Old 11-08-2010, 07:49 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
mark houghton's Avatar
 
Join Date: Jul 2008
Location: Central Washington State
Posts: 3,839
Quote:
Originally Posted by wjfk32 View Post
This weekend I did some nice top end runs. Weather was approx 53-56F. I was seeing 15psi. I car pulled and pulled..Its amazing what COLD weather can do. Plus I tightened up some bolts by the wastegate and other places where boost could escape.

Its nice when CIS works out and no hickups.

Walt
In the words of Emril Lugassi..."oh yeah babe"!!!

This morning, at 29 degrees outside, the sun just barely peeking over the horizon on a clear blue sky, frost on the windows of my less fortunate cars out in the driveway, I roll the 930 out of the heated garage into that cold dense air and hit the road for my 25 mile commute to work. Got the heater cranked to max (which isn't saying much, but kept things quite comfortable inside).

Got through town, WUR finished with cold control pressures, AAR closed, car idling at 950 with AFR's steady at 14.0, just purring. Hit the highway, go through the first 3 gears and lug along waiting for someone to get in my way. There he is!!! Down shift to second and positively blast past the dude. I think the front end came off the ground there for a second. Snag third, then a docile fourth and lump along the rest of the journey until the next opportunity arises.

Good Lord these cars like cold air and just positively rip up the road. I think I gained about 20 horses for free. AFR's hit about 12.2 at full boost (cold air will do that). This may be the last run of the year before the white stuff starts to fall, so a good memory to tide me over until spring.
__________________
Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 11-08-2010, 08:29 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
wjfk32's Avatar
 
Join Date: May 2008
Posts: 1,257
Mark, great write up!!

I did spin the tires in 2nd gear w/o flooring it (915)..Personally I don't want to do that. $$$$$.

I also ran into an S5 Audi--a little side by side fun..I was glad I was in the right lane--high frequency/exhuast sound. in 3rd gear.
The Audi's windows were down(GOOD)--ThIS Kid-20 something just bugged when passing him.

Walt
Old 11-08-2010, 08:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
EmptyGarage's Avatar
 
Join Date: Jul 2009
Location: Nova Scotia
Posts: 533
Quote:
Originally Posted by j930 View Post
so the higher the bar the longer it stays in boost if I am understanding correctly, and thus giving more air for more power.
I'm no expert and please correct me if this is stated wrong.

The higher the bars (pressurized air) the more oxygen in the cylinder the greater the amount of gasoline that can be ignited. Without turbo the cylinders can have a maximum of X liters of air and x liters of gas, (lets say x = 1 unit). When you boost at 1 bar you now have 2 units of air so you have enough oxygen to combust with 2 units of gas. This all produces more HP with same size cylinder, otherwise you would need a larger cylinder to burn 2 units of gas.

So more you increase boost the more fuel you can pump into cylinder for combustion, that is until you start throwing rods and burning pistons.
__________________
1986 930 EFI, twin plug, lovin the sport seats
Old 11-08-2010, 12:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Large Member
 
krasuskyp's Avatar
 
Join Date: Nov 2001
Location: top of 3rd
Posts: 4,229
Garage
Awesome Walt / Mark. Well done well said. Nothing like crisp cool fall intake fodder. Add a tint of moisture (cold fog=vehicular bonghits) and Bob's your uncle.

Cold tires on cold roads tho must be factored in heh heh.

Hear ya Mark on the season's over - least you ended on a high note! Not here.

TR3's still in garage so awoke yest to 930 under 3" of heavy slush. Prob the first it's ever seen, I shoulda snapped a shot. Ah well. And in parking it there last I drove it, I popped a FP fuse out of ??? nowhere (WTF?). Time to evict TR3 to storage & hibernate the 930 8-(.

Can't complain, I did have a fantastic driving season w/ the pig. In all of my pigs, really.

j930... drive a 'regular' t/c'd car and develop boost knowledge / impressions so you'll have a baseline, as a 930 is really not a good baseline (well, for learning... it's the BEST baseline otherwise lol). Boost also depends on load, so it's build-characteristics differ per gear per throttle input per RPM per hill etc. I don't hit max (0.84) bar in 1st say until like near 4200, and it holds flat until 6k or so. 3rd gear I'll see max @ 3200 or so.

def read Corky Bell's book

HTH

__________________
Paul... CT | '87 930 | '08 M3 6gang vert |
past:

| '07 S6 | '98 M3 vert | '01 M5 | '96 993 C2 cab | '05 S600 Sport - biturbo V12@Just Not Right 495rwhp / 612rwtq |
| '58 TR3A | '01 S8 | '95 S6 6gang | '88 M5 | '87 190E 2.3-16 |
Old 11-09-2010, 06:17 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 10:03 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2020 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.