rv_safetyman-More power in cruise?

Sam 4106 · March 28, 2010, 12:39:47 AM

Hi Jim,
I didn't want to hijack your CAC fan thread so I'll ask here. You mentioned your engine w/DDEC has 500 HP in cruise, which implies that it has less HP using the throttle pedal, does it? Our MC 8 with DDECII (450 HP)also seems to have more power available in cruise and I thought it was just my imagination. If DDEC engines do have more power available in cruise do you know how much more? In general, we don't have much for hills here in Minnesota but driving in New Mexico and Arizona in December and January I did think there was a difference between pedal and cruise control. Thanks for any information you can provide.
Sam MC8

PCC · March 28, 2010, 01:26:42 AM

Am I wrong or is it the same ECM controlling the same engine driving the same tires on the same vehicle?

If the pedal can do it, so can the cruise, and vice versa, if my understanding is correct, which means the engines horses are not any different whether in cruise or not.

If I am wrong - I really need to know .

Busted Knuckle · March 28, 2010, 01:48:38 AM

Sam,
It could be true!

Keith you maybe incorrect!

The master minds of fuel misers figured out way back when computers became common that if you give drivers more horse power on cruise than on the pedal more of them would be content at setting the cruise and letting it ride, rather than foot flat on the floor all the time!

So many ECM's are set up with 25-65 more horse power on cruise than the pedal.
When the 60 Series first became popular the most common setting was 435/470 then it went to 450/485 then 470/500 etc. CAT did similar ratings. I never heard of a split power Cumapart but I'm sure they had them too!
FWIW YMMV

BK

(ain't it amazing what they can do wit alectronix?)

belfert · March 28, 2010, 05:42:35 AM

My Series 60 is a 325/350 HP. 325 HP when the accelerator is manually manipulated and 350 HP when using cruise,

It sucks because the times when you really want all the power are the times you probably wouldn't be using cruise. I inquired about having this feature removed via reprogramming, but the cost was sky high so I decided it wasn't worth it.

chuckd · March 28, 2010, 06:19:17 AM

I had a Volvo 610 tow vehicle with an M 11 that had a dual "torque" cruise. It had 350/375 hp, and 1350/1450 ft lbs of torque. This was only on cruise and only on 9th and 10th gears.

Chuck

rv_safetyman · March 28, 2010, 06:32:50 AM

Well, folks have already answered the question. Yes, my engine is rated at 430/500. So, in cruise control, it has more HP. I think this was done to encourage drivers to use the CC to save fuel.

We are still on the road, so I don't have my library of literature on this engine. I did find a Spanish version of the specification sheet: http://extranet.detroitdiesel.com/Public/specs/3sa353s.pdf. The curves show how the engine performs with and without cruise control.

On my original engine, it was set at something like 430/470. With the ProLink I could choose either the single 470 rating or the 430/470. I had it set on straight 470. The ProLink also showed the torque set to 1450 on the original engine and this one shows 1650 ft lbs.

In any case, it sure seems to climbs the hills better (until I have to back off for the inlet air temperature

)

Jim

bs4104 · March 28, 2010, 08:06:43 AM

Jim: Just turn off the air temperature gauge in the SilverLeaf. Mine also (temperature) go up with the Jakes on long down hill run. The Cummins also has the More power in cruise Too. Bruce

rv_safetyman · March 28, 2010, 08:55:20 AM

Bruce, I really struggle with where the max air inlet temperature should be. It appears that DD has a limit of 50* above ambient. Given that we could hit 110* weather, I have set MY limit at 160-170*. If I don't back out of the throttle it will go well over 200*. I have to wonder out loud if I accelerated my original engine problem by letting the air temp get up to 250* a few times.

I think the ECM probably has some algorithm that de-fuels the engine when the temp gets too high, but I have not encountered it.

With the replacement engine, I want to make sure I don't do anything to hurt it.

My quandary is with the 92 series. The turbo dumps the hot air (at least 300* ?) directly into the blower and then a really puny water to air "cooler" tries to handle the heat from both the turbo and blower (blower minimized by by-pass). The air going into the cylinders has to be well over 200*. Guess it is all what the engine is designed for.

Jim

Sean · March 28, 2010, 09:06:05 AM

FWIW, the way a lot of drivers get around this is to engage the cruise at a low speed, say 35mph, then drive the bus normally with the throttle pedal. The ECM gives you the extra HP whenever the cruise is engaged; that HP is available to the pedal as well, so long as cruise remains engaged.

Also, IIRC, the HP split is settable with a Pro-Link -- Detroit already got its $$$ for the extra HP up front, and you should not need to pay for a new "program". Which does not mean that some shops with a Pro-Link won't try to stiff you for changing one setting. I would offer to unset it for you, but I have the older DDR (instead of a Pro-Link), which only works on DDEC-II.

-Sean
http://OurOdyssey.BlogSpot.com

gus · March 28, 2010, 09:06:22 AM

My 671 is set at 218 HP at cruise and 217.5 not in cruise!1

TomC · March 28, 2010, 09:10:40 AM

Any electronic engine can be programmed to have less power with the pedal and more with cruise control. This is mainly done to encourage the driver to be in cruise control more since most drivers have nervous right feet and don't know how to coax better fuel mileage out of their rigs. The split horsepower/torque ratings can be turned off to get maximum power from the pedal.

There are instances where being on cruise control will burn more fuel then if you were using the accelerator. If you're in rolling terrain, you're better to be on pedal. If you're on cruise control, it will accelerate at full throttle up the hill and continue to accelerate down the hill until you get back up to speed. If you use the accelerator pedal on rolling hills, you can keep the pedal pressure the same going up the hill allowing the bus to slow down then at the top you can release the pedal all together and let gravity increase the speed back up. Course this only works on a multiple lane highway. If you're on a 2 lane, this method would be down right rude to the people behind you (I always pull over when 5 cars are behind me on a 2 lane). This method has been proven many times.
We have an owner/operator with one of our new Freightliner Cascadia's with 455hp DD15 and 13 spd running between Salt Lake City and Phoenix-which is not a flat route by any means. He has progressive shifting programmed into the engine (something you can only do with a multiple speed transmission-can't with a 4 or 5spd manual), top speed of 61 mph. He only uses the cruise on flat ground. In the first 150,000mi of driving, his on board computer has a life time fuel mileage average of 7.6mpg-and this is at 80,000lbs! I wish I could get that weighing 34,500lbs! With the 2010 certified engines getting even better fuel mileage since the smog controls on the engines have been backed way off, and relying on the exhaust treatment, we should see 8mpg trucks at 80,000lbs regularly. Imagine what the DD15 could get in a bus? Theoretically, at 40,000lbs, around 15mpg! Good Luck, TomC

belfert · March 28, 2010, 09:44:38 AM

Quote from: Sean on March 28, 2010, 09:06:05 AM
Also, IIRC, the HP split is settable with a Pro-Link -- Detroit already got its $$$ for the extra HP up front, and you should not need to pay for a new "program". Which does not mean that some shops with a Pro-Link won't try to stiff you for changing one setting. I would offer to unset it for you, but I have the older DDR (instead of a Pro-Link), which only works on DDEC-II.

Interesting. The local authorized Detroit shop didn't mention it was a simple setting that could be changed without major expense. They claimed it was a major programming change. I could probably get the bus garage I use to just change it the next time I get my yearly oil change, lube job, and brake check.

rv_safetyman · March 28, 2010, 10:00:08 AM

Brian, I have probably misled you. When DD programs the computer, they can either put in one HP setting or a table of settings. If the table is there, the ProLink can select from the table. My original engine had the two options. The replacement engine has only one option, so I could not choose 500HP at all conditions.

I have heard of ECMs with several HP settings with some pretty large differences. The truck owner could select the HP option based on things like the driver skills. DD also has the ability to have several HP options that are settable by a switch. Saw it in the manual, but have never heard of a real life application that had it.

TomC, I fully agree about taking the CC off for rolling hills. The Jakes should also be off so that you can "run the hills" better (bet the young drivers have not heard that term).

Jim

Sam 4106 · March 28, 2010, 01:32:24 PM

Hi folks,
Thanks for all the responses. I now know how to manage my driving to optimize my fuel economy. The vast knowledge of this group always amazes me.
Thanks, Sam MC8

belfert · March 28, 2010, 05:49:04 PM

I don't know if I have a second HP table I can enable in my DDEC or not. I simply called the local Detroit dealer for a price to change this. The guy on the phone said it would have to be reprogrammed without ever having actually seen my engine.

The trick of setting the cruise at 35MPH sounds like a neat trick to try. What is the minimum cruise speed setting on a DDEC III? Most vehicles won't enable cruise below about 40MPH.

I almost never turn on the Jake when I have cruise enabled. There is some wierd interaction between cruise and the Jake that screws with the tranny. (Those of you with non-electronic trannies and engines won't have this issue.) I usually only turn on the Jake when I need it like going down a grade.