Community Forums

IMDSailor · 08-24-2012, 06:46 AM

As the OP of this thread, all I can say is, Great Stuff, love a healthy debate. It's through these forms and exchanges that I hope to get from DD(Diesel Dumb) to DS(Diesel Smart) or at least DK(Diesel Knowledgeable). Some of it makes my brain hurt, but I'm a learn'in.
Stewart

jimcumminsw · 08-25-2012, 08:18 AM

Quote:

Originally Posted by IMDSailor

As the OP of this thread, all I can say is, Great Stuff, love a healthy debate. It's through these forms and exchanges that I hope to get from DD(Diesel Dumb) to DS(Diesel Smart) or at least DK(Diesel Knowledgeable). Some of it makes my brain hurt, but I'm a learn'in.
Stewart

Here is a free publication from Turbo Diesel Register.Com that is available for free. You need to down load the PDF booklet and even though it is gear to the RAM Cummins engine it will give you some knowledge on how a diesel works. It is called a Turbo Diesel Buyers Guide. Good luck.

http://www.turbodieselregister.com/magazines/buyersguide.phtml

Jim W.

DriVer · 08-25-2012, 08:31 AM

Quote:

Originally Posted by IMDSailor

As the OP of this thread, all I can say is, Great Stuff, love a healthy debate. It's through these forms and exchanges that I hope to get from DD(Diesel Dumb) to DS(Diesel Smart) or at least DK(Diesel Knowledgeable). Some of it makes my brain hurt, but I'm a learn'in.

Stewart, I put the question forward to a point of contact and I hope to get an answer shortly.

I had a Banks gauge package that I used in conjunction with my 7.4L Power Stroke Diesel back in 1997. When pulling my fifth wheel, I kept an eagle eye on the EGT especially when pulling grades. I recall that approaching the EGT Hi-Temp threshold, all I had to do was lift for a few moments and the temps would tank. Once the EGTs had recovered into a nominal range, the process would start all over again. Straight and level under tow - never a problem. Not towing ... never had a Hi-Temp reading even under WOT on grade.

steveatpa · 08-25-2012, 10:03 AM

Quote:

Originally Posted by DriVer

Stewart, I put the question forward to a point of contact and I hope to get an answer shortly.

I had a Banks gauge package that I used in conjunction with my 7.4L Power Stroke Diesel back in 1997. When pulling my fifth wheel, I kept an eagle eye on the EGT especially when pulling grades. I recall that approaching the EGT Hi-Temp threshold, all I had to do was lift for a few moments and the temps would tank. Once the EGTs had recovered into a nominal range, the process would start all over again. Straight and level under tow - never a problem. Not towing ... never had a Hi-Temp reading even under WOT on grade.

DriVer, you are correct. Pulling back of the throttle will immediately cause the EGT's to drop. Remember, EGT's are completely connected to the amount of fuel. Diesel are like furnaces whereby the more fuel you cram in there, the hotter they get. (That of course not involving boost in that equation) But.....the problem with cutting throttle during a climb is that the you can cause the engine to "get under the turbo" and potentially put yourself in a situation where you place the engine under a greater load trying to continue climbing where then the EGT's get even higher.

While climbing a grade, I would suggest NOT coming off the throttle as long as the EGT's are maintaining in the safe zone. Point which I think you're making is to just slow down a little thereby lessening the EGT's a little too. Good advice for some who doesn't understand. And certainly trying to push through the grade with EGT's skyrocketing out of the safe zone will cause engine damage.

You mentioned Banks too. One main reason Banks is so popular is because they generally incorporate a fail safe system where the system is watching the vitals for you and will do things like de-fuel if you're not paying attention to the EGT's.

DriVer · 08-25-2012, 10:28 AM

Quote:

Originally Posted by steveatpa

While climbing a grade, I would suggest NOT coming off the throttle as long as the EGTs are maintaining in the safe zone. Point which I think you're making is to just slow down a little thereby lessening the EGTs a little too. Good advice for some who doesn't understand. And certainly trying to push through the grade with EGTs skyrocketing out of the safe zone will cause engine damage.

Thank you for the reply and continuing comment.

In my remarks I stated that I would only lift (read sligtly) and not get off the throttle and as you suggested, you "DO NOT" (read never) want to scrub off a lot (or any) of energy on a long pull.

Unless an RV owner has a go-zillion lbs/ft of torque, it's never a good plan to pull at low revs on grade because the turbo just won't provide enough boost.

Older pre-97 emission engines would probably be able to take this type of a beating occasionally however I am uncertain how 2010 engines will do under a heavy load with few revs. I'm sure that the NOx goes to hell in a hand basket and the DPF might start loading up with the IP screaming for a regen.

I am really unable to render an educated opionion in this matter since I have not driven a vehicle in this profile however I expect that my comment will be fairly close to what could happen.

RustyJC · 08-25-2012, 10:48 AM

The new diesel engines' variable geometry turbochargers (VGTs) have a much broader operating band than the old fixed geometry turbos that had too much nozzle area for low RPM operation, so they're not as prone to "getting under the turbo" as the older engines as the VGTs will close down the nozzle area to spool up the turbo. Having said that, keeping the revs at or above the peak torque RPM is still a good idea.

Rusty

DriVer · 08-25-2012, 12:43 PM

Quote:

Originally Posted by RustyJC

The new diesel engines' variable geometry turbochargers (VGTs) have a much broader operating band than the old fixed geometry turbos that had too much nozzle area for low RPM operation, so they're not as prone to "getting under the turbo" as the older engines as the VGTs will close down the nozzle area to spool up the turbo. Having said that, keeping the revs at or above the peak torque RPM is still a good idea.

Rusty, Thank you for your insight into the VGT. Your comments are always appreciated.

MaxxForce has chosen not to use a VGT in its 2010 and beyond engines if recollection serves me well. MaxxForce engines use 2 fixed BW turbos. One turbo comes in in low rev conditions and as the engine spools up, it seamlessly passes the baton to the larger turbo which keeps everything humming and moving down the road.

As I recall, it was reported to me that replacing either the lo or high speed turbo was considerably less expensive than replacing a VGT. Would this be consistent with your opinion in this matter as well?

Quote:

Having said that, keeping the revs at or above the peak torque RPM is still a good idea.

This is just about the best advice to any diesel owner that can be shared ... and I agree!

Just like an aircraft, if you scrub off too much energy at the wrong time, you could be toast!

Lessons learned; keep your energy levels as high as possible for the task at hand.

steveatpa · 08-25-2012, 01:02 PM

Quote:

Originally Posted by RustyJC

The new diesel engines' variable geometry turbochargers (VGTs) have a much broader operating band than the old fixed geometry turbos that had too much nozzle area for low RPM operation, so they're not as prone to "getting under the turbo" as the older engines as the VGTs will close down the nozzle area to spool up the turbo. Having said that, keeping the revs at or above the peak torque RPM is still a good idea.

Rusty

Exactly.