Exhaust Brake

[dons2346]

Anyone know how much back pressure the exhaust brake in a ISC can cause? I know it depends on RPM so lets assume red line

[1doodadd]

Here is some reading for ya........


https://www.dieselnet.com/tech/diesel_exh_pres.php

[dennis45]

Originally Posted by 1doodadd

Here is some reading for ya........


https://www.dieselnet.com/tech/diesel_exh_pres.php

Not sure that article has much bearing on the OP's original question.

To the OP, do you mean restriction with the butterfly open or closed? im going to assume Open? Closed would not be an issue.

[dennis45]

Sorry, I meant to attach this doc.

[dennis45]

Looking at the Jacobs FAQ's, they don't mention restriction at all. Can't say for certain but IMO, I don't believe it would make any measurable difference given its proximity to the turbo Outlet.

https://www.jacobsvehiclesystems.com...-support/faqs/

[Happycarz]

Don, I know that PacBrake uses 60 psi on Cummins ISC & ISL engines. They have an port on the side of the exhaust brake that can be used to verify back pressure with a gauge.
Earlier models were adjustable, but since at least since 2008, they are set from factory with no field adjustment available.

[dons2346]

Harry,
The 60 you mention is pretty close to the 55 max that I have been told. I am having some blow which is throwing oil on the rear of the coach. Excessive back pressure from the exhaust brake will cause this.

To the others that supplied reading material, thanks

[dennis45]

Originally Posted by dons2346

Harry,
The 60 you mention is pretty close to the 55 max that I have been told. I am having some blow which is throwing oil on the rear of the coach. Excessive back pressure from the exhaust brake will cause this.

To the others that supplied reading material, thanks

Overfilling the crankcase will have this result also. I keep mine about 1/4" to 1/2" below the full mark. Any more and blows out the breather tube.

[dons2346]

Originally Posted by dennis45

Overfilling the crankcase will have this result also. I keep mine about 1/4" to 1/2" below the full mark. Any more and blows out the breather tube.

This is where my oil level is. Thinking about going lower but it was suggested to check the back pressure on the exhaust brake

[PGCI2006]

I had problems with the turbo brake on my 2008. Haven’t used it since, my Allison tranny slows me pretty good though.

[JohnBoyToo]

is it an exhaust brake or an engine brake ?

Mine has an Engine brake, but the manual calls it an Exhaust brake too:
Exhaust Brake
The exhaust brake is designed to supplement the standard wheel braking system. It s not designed to bring the motorhome to a complete stop. Use of the exhaust brake can extend service life of brake linings. The exhaust brake switch (located on the driver’s console) activates the auxiliary brake integrated in the variable geometry turbocharger.
To Engage the Exhaust Brake:
Turn on exhaust brake switch and release the throttle to the idle position.

When the auxiliary brake is activated, the variable geometry turbocharger will restrict exhaust gases causing increased back-pressure within the engine. Increased back-pressure slows the speed of the engine resulting in braking action. The amount of engine braking power developed is relative to engine speed (RPM).
When the auxiliary brake is activated going down a hill, it will help control road speed or sufficiently slow the road speed until the transmission can automatically downshift to the next lower gear. Downshifting automatically occurs from high gear down to second gear.
Certain road conditions and engine speeds may require the transmission be manually shifted down in order to generate adequate engine RPM and increase the engine brake effect.
NOTE:
The brake lights will illuminate while the exhaust brake is applied.
caution:
Activating the exhaust brake switch does not cancel cruise control.

[MartinP]

Originally Posted by dons2346

Harry,
The 60 you mention is pretty close to the 55 max that I have been told. I am having some blow which is throwing oil on the rear of the coach. Excessive back pressure from the exhaust brake will cause this.

To the others that supplied reading material, thanks

How does the back pressure that is caused by the exhaust brake cause engine blow by out of the breather when the combustion pressures are much higher and my not cause any blow by? I installed a Pacbrake and was actually concerned more with the turbo seals until I called up tech support at Pacbrake. However, I do wish that the pressure relief setting was adjustable as I personally think 60 psi is a tad too high.

[twinboat]

There will be more pressure in the exhaust ports when the exhaust brake is on. That pressure could push past the exhaust valve guides, increasing crankcase pressure.

[96 Wideglide]

Originally Posted by JohnBoyToo

is it an exhaust brake or an engine brake ?

Mine has an Engine brake, but the manual calls it an Exhaust brake too:
Exhaust Brake
The exhaust brake is designed to supplement the standard wheel braking system. It s not designed to bring the motorhome to a complete stop. Use of the exhaust brake can extend service life of brake linings. The exhaust brake switch (located on the driver’s console) activates the auxiliary brake integrated in the variable geometry turbocharger.
To Engage the Exhaust Brake:
Turn on exhaust brake switch and release the throttle to the idle position.

When the auxiliary brake is activated, the variable geometry turbocharger will restrict exhaust gases causing increased back-pressure within the engine. Increased back-pressure slows the speed of the engine resulting in braking action. The amount of engine braking power developed is relative to engine speed (RPM).
When the auxiliary brake is activated going down a hill, it will help control road speed or sufficiently slow the road speed until the transmission can automatically downshift to the next lower gear. Downshifting automatically occurs from high gear down to second gear.
Certain road conditions and engine speeds may require the transmission be manually shifted down in order to generate adequate engine RPM and increase the engine brake effect.
NOTE:
The brake lights will illuminate while the exhaust brake is applied.
caution:
Activating the exhaust brake switch does not cancel cruise control.

That's a VGT exhaust brake you've got. Switch is wrong.