standard or advanced timing?

thomasinnv · December 13, 2011, 03:21:26 PM

The other thread has some talk about standard verses advanced timed engines, specifically the 8v71 in bus application. I have a few questions, and hope for some knowledgeable answers.

I have leaking endplate gaskets, so bad that I have no choice but to remove the engine and r&r gaskets. I will chose to completely tear down and replace all gaskets, seals, etc. while I have the engine out. I have N65 with advanced time, and wonder if I should consider changing the timing and/or possibly the injectors while I have the rear end apart.

So, to the question at hand...what are the effects of standard vs. advanced time as far as torque range and effects on driving (I have an alison 740), power output, any difference in effect of altitude, fuel economy, heat generation, longevity of engine itself, and any thing else that might be a factor? Some real time numbers or documented figures would be nice.

This is just as much for informational purposes as it is for me wanting to make a decision on making some changes.

Utahclaimjumper · December 13, 2011, 05:01:42 PM

Your 740 has enough gears to satisfy the "A" timing and N65s, leave it and enjoy.>>>Dan

bevans6 · December 13, 2011, 05:19:10 PM

The published information from Detroit Diesel is that the standard bus tune has 270 hp with 770 ft lbs of torque at 1200 rpm, the A-timed engine with N65's has 318 hp and even at the same 1200 rpm has 805 ft lbs of torque. Yes, it's peakier but it has more power everywhere than the bus tuned engine has.

Brian

luvrbus · December 13, 2011, 06:54:14 PM

7E65 injectors with standard timing on a 8v71 N/A

2100 rpm 318 hp
818 ft lbs of torque @ 1400 rpm
with less fuel lol

good luck

Utahclaimjumper · December 13, 2011, 06:57:36 PM

Another aspect of that combo is governed RPM,, you need at least 2250-2300 to satisfy that engine and trans combo and make it all usable.>>>Dan

thomasinnv · December 13, 2011, 07:03:46 PM

So, Clifford the numbers you posted seem pretty close to what my current setup is now. Any reason other than fuel consumption to change from what I have now? What about heat rejection? we all know these MCI's don't like heat.

When you say less fuel, just how much less?

Utahclaimjumper, currently set @ 2450 no load per the DD bible.

luvrbus · December 13, 2011, 07:09:49 PM

Your fine Derrick we took some smoke and power away from yours just run what you have this spring we will install a different blower and a new setting you will be good to go if you sell that heavy @$# tow vehicle lol

good luck

buswarrior · December 13, 2011, 09:43:01 PM

Apples and oranges...

Don't mix SAE net and SAE gross calculations...

IIRC, bus trim quoted at 270HP is a net number, then to be fair, the 318 is Gross, so to compare properly, it is 304HP net.

happy coaching!
buswarrior

thomasinnv · December 14, 2011, 08:31:23 AM

Hey Clifford that heavy tow vehicle is history. I replaced it with an eddie bauer ford exploder, about half the weight. Now I'd just like to keep from oiling it every time I tow it. LOL.

Geoff · December 14, 2011, 09:51:30 AM

I had a '79 RTS roll through here that had an 8V71TA in it and stock 7E60 injectors (this engine would have std. timing and federal cams). I talked to my injector rebuilder and he said the E injectors were bus-smog injectors and for more power and less smoke we went went with good ol' N75's.