Boost Boost Boost ??????????

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I have a few questions about boost.
1st If Dodge limits boost to 20 psi there must be a reason. If so Why?
2nd I'm running DDII's and boost module and my boost pressure easily hits 30+ at this pressure am I causing any damage? (I know some guys hit in the 40's (HVAC)).
3rd If I shouldn't be concerned about boost why do I need a gage other than coolness factor?

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Jim

Patriot blue Y2k 5sp Stealth 2500 (markings removed)QC,SLT+,leather, camper,TT,lsd,3. 54,4x4,hd xfer case,Geno's dual gauge,DD IIM's and boost module,ARE lid & bedrug liner, Sony 10 disk cd changer.

 

[Archive]

Hey Jim,
I consider the boost gauge more of a diagnostic tool than something to prevent damage. In other words, if you were used to seeing 30psi under certain conditions, and now you're seeing 20, you would look for the cause; loose clamp, wastegate stuck, those kinds of things.
As far as why Dodge tells Cummins to limit boost and fueling, my opinion is that it is all political. Driveline warranty concerns, epa. Nothing concerning protecting the engine itself.

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99 3500 Reg Cab, Red, 2wd, 5spd, 4:10
(2) 87 GN's (Also turbo 6's)

 

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Oh, as far as hurting the motor with the extra boost... Of course if there is something wrong with the motor, more boost would make it show up faster, but there is so much overbuild margin in the Cummins, an extra 10 or 20lbs probably doesn't even get noticed except to make extra oxygen available for combustion and cool egts.
Speaking of overbuild margin, look at HVAC, Joe Donnelly and others. 600hp. 1280ft lbs of torque. Makes me breath easier knowing my mild setup doesn't come close to what the Cummins is capable of.

 

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Thanks Turbo-6
Just wanted some Peace of mind I guess.

Jim

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Jim

Patriot blue Y2k 5sp Stealth 2500 (markings removed)QC,SLT+,leather, camper,TT,lsd,3. 54,4x4,hd xfer case,Geno's dual gauge,DD IIM's and boost module,ARE lid & bedrug liner, Sony 10 disk cd changer.

 

[Archive]

Jim,
Take a look at the thread on this forum that is titled HVAC does it. With the HP and torque he is putting out at around 45lbs of boost and the engine is running strong, you won't have any problems.
Mike

 

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<font color=blue>Well the number thats heard to not "exceed" is 45 PSI of boost on the Cummins. And also you ask why Cummins limits boost to 20?, well there are alot of reasons, having to do with EPA, federal regulations, and etc... And also I believe there is such a thing as TOO MUCH boost for a "set" fuel level.

 

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<font color=Teal> The other thing that has been usefull having a boost gauge is it show you what kind of load you are under while driving.

Example going to a match is Montana All of the sudden I was seeing 15-20 lbs of boost running 80 (usally at 6-8). I was running right into one hell of a head wind.
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Dee'sel
97 2500 Club 4X4 3. 54 LSD 5 speed, K&N Air filter RE0880 & Psychotty,
TST #11 all the way forward, #12 for winter, AFC spring kit, Geno's Exhaust Blanket
TST EGT gauge & TST 0-60 boost gauge in A Pillar, Hypo clutch ass.
Cat-be-gone, 4" Dynomax Bullet muffler, Crome 4" turn down,
AmsOil 80W-90 in Trans GL-4, Amsoil 15W-40 Oil W/ Bypass system
Lund WInter front, Leer Cab Level Shell,
235/85R16 Goodyears *NRA/USPSA member and proud of it*

 

[Archive]

I had also read that Dodge considers the wastegate as part of the "Emission Control System". .

HMMMMMMMMMM

Interesting when you consider that other Non RAM B5. 9 ISBs are equipped with Non-Wastegated turbos from the Cummins factory.

Larry

 

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Turbo 6 is dead on target (as is everyone else). The boost gauge operation was the first indication of a loose clamp on my system. Yeah, I could feel it under acceleration, but had a DC mechanic checked it all would have been OK because it did develop 20 psi. I knew something was wrong because of the pause on the way up there. Higher boost... . without the fuel to go with it what's the use? Also, with the 17:1 compression ratio, that is a lot off cylinder pressure at combustion when you are feeding it 20 psi or more.

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2001 ETH DEE 2500, 4. 10 LSD, Towing Package, Electric Brakes, EGT/Boost Gauges, Running Boards, K&N,
Real Backup Lights

 

[Archive]

I was at Cummins yesterday dropping off a dyno sheet and picking up my new "Cummins" valve cover. One of the mechanics told me that in marine spec engines you would often see high 30's for boost under normal conditions. I don't believe those engines are controlled by the EPA the way are trucks are.

 

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I am truly in awe of the boost a b5. 9 can take, I used to be a hot rodder and remember reading about grand nationals having head gasket probs above 24 psi or so and now I read on the ford site about the psd not being able to do more than 35 (which is still high). The last time I checked Dave Mitchell was running 45, he used to run 60 psi but kept imploding turbos when shifting, it seems with the manual transmission the sudden drop in boost when shifting will grenade a turbo above 45 or 50 psi. That is phenominal to think that a cummins can withstand 60 psi (although the turbo itself can't) Like HVAC said you could feed these killer B's grenades and they'd keep running. I would like to know the cylinder pressure of a cummins with 17:1 compression and 60 psi, I'll bet it is A pretty big number. I used to work on F-14 tomcats in the Navy and would stand in awe as they would run the engines at full afterburner with 24 (yes 24) chains holding the aircraft in place, it would rattle the fillings out of your teeth!!!!!! I Imagine seeing Dave Mitchell pull would be kind of like that... . I WILL see him pull before I die!!!!

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BLACK BEAST: 2K1 QC, SWB, Auto, 4X4, 4. 10 LSD, SLT, Black, Camel leather, Tow pckg, nv241HD, cab lights, 2 inch daystar coil spacers, 35 inch Mickey thompson claws, bushwacker flares, rhino lined bed and rocker panels.

soon to come; DD stage 1's, boost module, possibly van aaken.

GREEN MACHINE: 93 Jeep Wrangler 4. 0L, T-18, 38X11 Boggers, Dana 44's, AtlasII T-case, ARB's, warn and moser shafts, Ramsey 5K winch... . NEEDS A DIESEL!!!!!!

 

[Archive]

Compression ratio is the ratio of ending pressure to starting pressure (in the cylinder). That would mean that starting at 36psig (gauge pressure), adding 14. 7psi to account for atmospheric pressure, to get 50. 7psia (absolute pressure - compression ratio's, etc. , all deal with absolute pressure). That would mean that the ending pressure would be 861. 8psia, or 847. 1psig.

To get ending pressure for any other starting pressure, just add 14. 7 to your boost pressure (this is assuming that the cylinder sees full boost pressure). Then multiply by 17 (17:1 compression ratio). That gives absolute pressure, if you want the pressure that a gauge would read, subtract 14. 7.

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1999 2500 QC 4X4 LB Auto 4. 10LS, Driftwood, CD player with Steering Wheel Controls, Power Driver's Seat, 275HP Injectors, PowerEdge, ISSPRO Boost and EGT, K&N Air Filter, Brushguard, Spray-in Liner, 285/75R16 BFG AT KO's, Nerf Bars, Black Diamond Plate Deep Well Tool Box, Mopar flat antispray guards (front and back)
2000 Yamaha Big Bear 400 4X4
NRA Member

 

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Drawson

Ain't these Cummins great. We need a boost gauge to know if we have a head wind. Never needed one with my gassers. All I needed was a speedo to know when I had a head wind.

Barry Horner
Lake Forest
Orange County, Ca

2001, SLT+, ETH, 6 speed, White quad cab, short bed, Sport, 2wd , 3:54 anti spin, Camper Special with trailer tow, 16x8 Forged Aluminum with 265x75 tires, Fog lights, Audio controls steering wheel mounted, AM/FM cassette with CD, Travel Convenience group, Keyless entry with remote, Leather agate heated seats. Line-X bed liner. ARE LS 2 taunau cover. Pillar mount boost and EGT.

 

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<font Color=blue>Yes Barry, these motors/truck are truely amazing. But I cauldn't have owned one in my earlier years, I wouldn't have a drivers licence.
</font><marquee> #ad
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Dee'sel
97 2500 Club 4X4 3. 54, Forrest Green/Edgewood, LSD 5 speed, K&N Air filter RE0880 & Psychotty, TST #11 all the way forward, #12 for winter, AFC spring kit, Geno's Exhaust Blanket
TST EGT gauge & TST 0-60 boost gauge in A Pillar, Hypo clutch ass.
Cat-be-gone, 4" Dynomax Bullet muffler, Crome 4" turn down,
AmsOil 80W-90 in Trans GL-4, Amsoil 15W-40 Oil W/ Bypass system
Lund WInter front, Leer Cab Level Shell,
235/85R16 Goodyears *NRA/USPSA member and proud of it*

[This message has been edited by drawson (edited 07-19-2000). ]

 

[Archive]

Actually the turbo can take more than 45 psi. The problem is that when you shift, you go to zero boost and the residual boost in the intercooler and lines tries very hard to kick the pinwheel backwards. Eventually it scrubs the bearings enough and flexes enough so it rubs the compressor housing, gets a little out of balance, and then scrrreeeee, time for a new turbo.
Chaaaa--chiiinnnnnggg Holset's cash register gets an influx of Rammerdollars.

 

[Archive]

Joe does this happen also with auto trucks? If I drive a WOT with the auto shifting does it have time to go to zero boost?

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BLACK BEAST: 2K1 QC, SWB, Auto, 4X4, 4. 10 LSD, SLT, Black, Camel leather, Tow pckg, nv241HD, cab lights, 2 inch daystar coil spacers, 35 inch Mickey thompson claws, bushwacker flares, rhino lined bed and rocker panels.

soon to come;Auto transmission upgrades and some Bombing to outrun the durrmacks and pSd's

GREEN MACHINE: 93 Jeep Wrangler 4. 0L, T-18, 38X11 Boggers, Dana 44's, AtlasII T-case, ARB's, warn and moser shafts, Ramsey 5K winch... . NEEDS A DIESEL!!!!!!

 

[Archive]

The HX40 and high boost levels with the auto transmission is something that I can't help but fantasize about #ad
I am imagining the boost needle flipping right and staying there all the way to redline and [Censored] mph! I wouldn't think the auto would have the drop in boost the manual transmission experiences. Consequently a "Scourge" could run more boost without turbo failure. It's just not fair I tell ya #ad
#ad

 

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I believe that Dodge's limit of 20 psi is to match their stock engine max design power output. In fact, if the stock ECM sees a boost pressure over 20 psi it responds by reducing the fueling signal. Pressures over 20 psi will not generate more power unless the fueling signal is modified or some method is used to deliver more fuel to match the more O2 from the higher boost pressure. On a stock engine the 20 psi boost provides ideal amount of O2 for the stock max fueling for the most efficient burn. Of course these values should change if engine is modified.

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Wait'n for my 2001 2500 QC, SB, 4x4, ETH 6-sp, 3. 54 LSD, SLT++ (everything but those silly looking lights on top of the roof), White over Silver, Tan leather.

 

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Compression ratio is volume based. To get compression ratio, divide the cubic volume of one cylinder by the cubic volume of the head plus the cubic volume of the head gasket.

5. 88 liter total displacement = 980cc/cylinder
At 17:1, 980/17 = 57. 647cc head + gasket volume

This doesn't change TXRam's calculations, Just another way of looking at it; p1v1=p2v2.

Ignoring the heat of compression, you get a 17. 286 psi cyclinder pressure increase for each 1 psi of boost.

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2001 QC SLT SWB ETH 6SP

[This message has been edited by Little Bill (edited 07-21-2000). ]