High EGT's or High RPM's.....?

[CumminsPuller]

Which is harder on fuel mileage?



Jason

 

[illflem]

High rpms and high boost are harder

 

[Shooter]

What Bill said

 

[Bigsaint]

I think what Jason is asking is which of the two are harder on the MPG, my guess is high boost ????



Scott W.

 

[Steve Campbell]

Should I choose sides....

The higher the boost (IMO) the lower the fuel mileage.



On the other hand, how does one get high EGT without high fueling/boost other than lugging the engine?

 

[Tom G]

Almost Answered My Question Without Asking

Gentlemen:



Ah yes - got the experts here talking about a question that has been on my mind for months. Please help me understand the relationship between boost, EGT's and RPM's



I tow a 25' 5er (about 6,000 lbs) and have been wondering why the following happens.



When I am going up a smal hill in O. D. I never see more than about 15-17 psi on my boost gage. EGT's usually hold at about 1100 degrees or some place close to that number and about 1750 RPM; HOWEVER



when the hill get steeper and the truck shift down out of O. D. (or I take it out of O. D. ) the boost jumpsto about 19. 5 psi, EGT's jump to about 1250-1350 degrees and 2250 RPM after the Torque Converter locks up.



I guess my question is - why can't I get full boost and power in O. D. ? I took the truck to the dealer and they have performed (and verified on a second visit) the TSB for O. D. power.



Your comments please

Tom Garven

Lake Havasu City, AZ.

 

[Ramboy]

My truck works pretty much the opposite of yours. I have no problem hitting max boost and EGT's in O. D. When towing, I drop out of O. D. to control EGT's while going uphill.

 

[Tom G]

Ramboy - Thank You For Info

Thank you for responding. I noticed in your signature that you have lots of goodies on your truck. If you can remember back to when you first installed your gages was your truck ever like mine?



I mean low boost in O. D. and high boost in the other gears. Do you think there is something wrong with my truck maybe?



Tom G

 

[dmurdock]

Tom, I don't think the 'puter will let you really "get on it" in overdrive, I think it unlocks the converter when you do (at least my wife's car is like that). I know that's not really a comparison, but every auto I've ever had has done that (basically the equivalent of downshifting).

 

[Tom G]

Thank You dmurdock

You are right. I can only press the accelerator down about 3/4 of the way while in O. D before it will downshift unless I am going faster than about 75-80 mph. Then I can put the petal to the metal but the boost still never goes any higher than 15 psi.



How about you; what kind of boost pressure are you seeing in O. D ?



How about 3rd gear?



Thank you

Tom Garven

 

[PBayer]

Tom

I just got back from a trip. I towed in stage 1 on the power edge box. Total trailer weight was about 8000ish lbs. Up a 5-6% grade I was able to hold 20 to 23 lbs of boost in OD and EGT's were 1200. I lost only 5 mph, from 75 mph. The little hy35 needs some help, so off to the hx35 in the future.

Paul

 

[dmurdock]

Sorry Tom, I have a 6 speed... but what your describing sounds like the computer trying to save the lockup clutches.

 

[Tom G]

Thank You Paul for the Info.

Hi Paul



O. K. it sounds like its time to get some type of fueling and boost box. Also it must be time to start preping the boss for $500 to improved our fuel mileage ;-|



I am only pulling about 2,000 lbs less than you and could never pull a 6% grade in O. D. with my 5er.





Tom Garven



Lake Havasu City, AZ 106 degrees today - just right for the pool or the lake.

 

[PBayer]

I know lot of people have many different type fuel/timing boxes... so heres my opinion. edge comp. I have the older edge 3 stage box and am very happy with it, however I see a comp box in my future. It has more adjustability and power. The box made the biggest improvement for the buck. Happy Bombing!!!!!!

 

[Tom G]

HI Paul

I am just waiting for my 3 yr. /36,000 warranty to expire. About another 6 months should do it. After that I figure the probability of the Cummins failing is way down on the list so will start warming her up a little Will also most likely have to get a transmission temp gage and also probably a valve body and torque converter upgrade.



Might be smarter to work a deal on a new 300 hp 2003 instead of spending a bunch of money on my truck. But if I keep her; I am leaning towards the True Torque Power Module (TTPM) however at $649 it seems to be overpriced compared to the other boxes around. I do like the fact that they are located in Lost Wages (Las Vegas) which is only about 150 miles up the road so if something goes wrong its not too far away. Also like the Van Aaken (sp) because it's CARB approved which the TTPM is not.



Have a great day

Tom Garven

Lake Havasu City - 200 miles from a 320,000 acre forrest fire in Northcentral Arizona :-(