Boost level

[Protsrace]

I have an 2000 Winnebago chieftain with a 5.9 Cummings motor in it.It has a banks power kit installed.Does any one no what the boost level should be.I am only seeing about 10 Lbs of boost in first and second gear.I have seen as high as 28 in 5 gear.Is this normal?

Thanks Dennis

[Finance]

I can tell you that with 28# of boost on that model of 5.9 you’re playing with fire in terms of exhaust temperatures. Does it have an EGT gauge?

If you’re not knowledgeable about diesel performance modifications it would be best to have a reliable Cummins mechanic check it out.

Depending on what model of transmission you have, it may limit torque in the lower gears to prevent damage.

[TomAndPeg]

You have the same vintage 5.9 ISB as ours, which limits the top end boost to around 24 psi in a stock configuration. There are after-market methods to modify the top end (Banks, etc.), but over-boosting for an extended period of time can increase the risk of damage to a stock turbo.

In addition to Cummins, I would suggest you have a conversation with Banks tech support. They no longer offer a performance kit for the 1998.5-2002 ISB, but they should be able to tell you what boost settings are expected and what components (including the turbo) have been upgraded in your kit to allow higher boost and EGT.

[gvjackson]

I have the 1998.5 version of this MH, with Banks, and I see boost generally maxing around 22 psi without regard to the current gear, although, I don't usually watch boost during accelleration. Does your unit move crisply through the lower gears, or does it seem to drag along to get through 1, 2, & 3? If crisply, I'd not be too worried. If not, then a deeper investigation might be warranted.

[Protsrace]

Originally Posted by gvjackson

I have the 1998.5 version of this MH, with Banks, and I see boost generally maxing around 22 psi without regard to the current gear, although, I don't usually watch boost during accelleration. Does your unit move crisply through the lower gears, or does it seem to drag along to get through 1, 2, & 3? If crisply, I'd not be too worried. If not, then a deeper investigation might be warranted.

It does seem to Accelerate a little slow in the lower gears but does seem to shift fine .That is why I asked if the boost is normally that low in the lower gears.It does have banks boost gauge and EGT gauge on the RV.It seems to be fine on the power in the higher gears.

[gvjackson]

Originally Posted by Protsrace

It does seem to Accelerate a little slow in the lower gears but does seem to shift fine ...

Your max boost eliminates induction leaks and a turbo issue, so, perhaps fuel flow. Which leads to an item I meant to include before. Your model year also featured the VP44 injection pump (1998.5-2002) which is HIGHLY dependent on a properly functioning lift pump for internal lubrication. If the lift pump starts to fade, the VP44 eventually starts to self-destruct. Thus, I added a fuel pressure gauge with sensor after the lift pump. While Cummins is more concerned with flow rate, falling pressure will be indicative. Strangely, fuel pressure/flow was not a standard piece of equipment, so, if one had not previously been added, please consider doing so.

Go ahead, ask me how I know that this VP44/Lift Pump issue is real!!!$$$$!!!

[Jzack]

Yes, as gvjackson stated, everyone "in the know" with the 24V ISB HIGHLY recommends replacing the OEM Carter lift pump with a high quality aftermarket unit to protect the very expensive VP44 injection pump from self-destructing. A fuel pressure gauge or warning light is also a must. Poke around on Geno's Garage and Blue Chip Diesel for some great info on the 24V ISB and the infamous VP44.

[Protsrace]

The VP44 was just replaced in March of this year.Also a good aftermarket lift pump was installed.I planned installing the fuel pressure this spring before I take it out again?Is it possible the injectors are causing the low boost?

[Bob_C]

I have a VP 44 from Blue Chip and what a difference.....I stayed with the Carter lift pump as it puts out 11 lbs, and 9 when towing on flat highways and 7 on hard pulls,,,,,Added fuel pressure gauge and RV 275 hp injectors from Geno's, and with a 4" exhaust with muffler, am getting 24 plus empty at 70 and 16 when towing at 65......max boost is 20.....make sure the 2 moulded rubber elbows on the intake side haven't started to slip out from under their clamps.......lost of boost if that happens....

[gvjackson]

I did not know about aftermarket lift pump alternatives until after my OE replacement. Then I danced around the pressure gauge install for almost 2 years before adding a GlowShift unit. Idling, my Carter is ~16psi, 11-12 psi cruising ~65 on smooth level road, and ~8 psi tugging our toad up the long 5-7% hill on I-77N near Fancy Gap. So I'll use that as my standard. I think I read, on the internet [emoji2957], that it takes at least 2-3 psi to ensure some VP-44 lubrication via the return fuel flow(?).

Regarding the question of injectors, I wouldn't think that injectors would directly affect boost level, and your(OP) high boost at speed would seem to align with this.

Unfortunately my snowbird trip departure is on hold, so I can't make any near term boost vs gear range observations, but I'm not going to risk the salt exposure for a joy ride, unless we get a mid-winter deluge to wash the roads.

[Gary RVRoamer]

The transmission gear doesn't effect the boost directly, but the engine rpms and throttle position do. If you push for maximum power in any gear, you should get maximum boost, which is usually 24 psi for that engine. Somebody may have cranked up the boost a bit with the idea that they get hotter performance, but that's a bit risky cause it really does get hotter (EGT).

[Protsrace]

Originally Posted by Gary RVRoamer

The transmission gear doesn't effect the boost directly, but the engine rpms and throttle position do. If you push for maximum power in any gear, you should get maximum boost, which is usually 24 psi for that engine. Somebody may have cranked up the boost a bit with the idea that they get hotter performance, but that's a bit risky cause it really does get hotter (EGT).

It does have a banks Kit on it.but with the pedal all the way down in first and second gear it only get around 10 all the way to it shifts.as soon as it hits 3 or fourth gear the boost is mostly around 25 but I did see it go to 28 once .But I didn’t stay in it long .

[twinboat]

Power brake it and see how high the boost climbs.

If it gets higher then 10, its probably just shifting before its fully loaded.

[Mr_D]

Due to the rating of some Allisons the power output can be restricted in first and second gears to keep from over stressing the trans. Call Banks and ask them.