Max Boost

[jimnance]

I have been told that for long engine life and towing a 10,000 lb fifth wheel that boost should be limited to about 30 PSI.



Any thoughts?

 

[Ramafid]

I don't know that answer but I'm interested about max boost also. How much boost does the RV 275 motors make? What are the gaskets rated for( head , intake)? Has anyone had a failure due to boost on engines making less than 30 lbs? I know the Cummins is tough but don't want to end up with problems down the road.

 

[jimnance]

boost

Also, how is boost regulated with a stock 5. 9 ISB engine. Is there a wastegate that is computer controlled?

 

[LSMITH]

Jim, boost is regulated two ways on the ISB. First the wastegate on the turbo opens releasing the exhuast pressure from the drive wheel. It is pnuematic, boost pressure pushes on a piston overcoming spring pressure to open the wastegate. Second, the MAP sensor feeds back to the ECM what the boost pressure is, and the ECM communicates to the VP44 how much fuel is needed to maintain max boost without exceeding it. These controls are bypassed by a bleed orifice in the line to the wastegate actuator or by by locking the wastgate actuator arm/shaft and by "clipping" the signal to the ECM with a boost module making the ECM unaware that boost is at or above the preset limit in the software. This is my understanding of how it works, hope it helps.

 

[jimnance]

boost

If that is the case, then the installation of the EZ chip must not increase max boost since it is only an electrical connection?

 

[RustyJC]

Re: boost

Originally posted by jimnance

If that is the case, then the installation of the EZ chip must not increase max boost since it is only an electrical connection?

The boost elbow shipped with the EZ box "tricks" the wastegate by reducing the pressure being sent to the wastegate actuator.



The EZ MAP plugs "trick" the electronics by routing the MAP signal through the EZ before sending it on to the ECM and PCM.



Working together, the boost elbow is what increases the boost. The boost module (fed by the MAP plugs) keep the increased boost from setting "Overboost" codes and illuminating the "Check Engine" light as well as keeping the VP-44 from defueling due to an overboost condition.



With the EZ and boost elbow, we're running 31-32 PSIG maximum boost towing our 13,500 lb 5th wheel.



Rusty

 

[Bob Wagner]

Jim, It would help if you posted your signature when asking a question

 

[jimnance]

signiture

Just added my signiture. Took me a while to figure out that signiture is where you put the data.



Thanks

 

[jimnance]

boost

Actaually I am installing a box sold by Western Diesel ( westerndiesel.com ) and they don't appear to have an elbow with the kit. If this is the case what is max boost setting for the wastegate?

 

[LSMITH]

Jim, if you have no elbow with the box then probably have no MAP connections either. Sounds like it closer to a VA than an EZ. If you have no MAP connectors from the box and no elbow included then you are stuck with factory boost levels, or you buy a boost module and add that to the setup. Factory boost levels really are fine unless you add injectors to the box. Keep an eye on the EGT when pulling hard regardless of setup.

 

[LSMITH]

I looked at the WD website and it sure looks and sounds like a rebadged EZ, however they made no mention of a bleed orifice for the wastegate actuator, or any mods to the wastegate at all. It is billed as a boost manager in the ad, so there has to be a way that it modifies the wastegate actuator either mechanically or by bleeding pressure. Read the instruction that came with it and see, let us know what the deal is as we are always curious about the boxes on the market.

 

[Texas Diesel]

Originally posted by jimnance

I boost should be limited to about 30 PSI.



Any thoughts?

Slightly off topic but if a person installed injectors and an EZ how would you limit boost pressure since the boost elbows are non-adjustable?

 

[RustyJC]

Originally posted by LSMITH

Factory boost levels really are fine unless you add injectors to the box. Keep an eye on the EGT when pulling hard regardless of setup.

Actually, in addition to the much improved midrange power/torque, a key benefit we see with our setup (Edge EZ with boost elbow @ 31-32 PSIG boost, BHAF, 4" exhaust) is a reduction in maximum pre-turbo EGT's from 1250-1300 degF stock to our current 1050-1100 degF when towing. Although more boost doesn't directly convert to more BHP, there are benefits for those of us who tow heavy loads.



Rusty

 

[Neal Cassady]

Texas Diesel,



If you want to manage your boost manually you can stay with the factory elbow and use the turnbuckle/j-hook method the HY35 crowd uses. If you do a search on the topic there should be quite a bit to read, including pictures of the setup.



Or you can buy an air compressor type regulator and plumb it into wastegate actuator line. This would allow you to fine tune the boost to the level that you want. I think there was a thread a while ago with a detailed description of this setup.



Dave