Hey Guys
I have a GM 4106 with 8V71 65 injectors. It has an out of frame rebuild with about 8000 miles on it. 730 transmission, I tow a 4400 lb. car. It's just about all I can do to make it up a 6% grade. Any suggestion how I might get a little more power. This engine was installed at the local Detroit dealer.
JLL, the 1st thing to do is check and be sure you are getting full throttle sounds like your not the shut down cylinder is the largest culprit of not letting a 8v71 engine open to full throttle.
I would start with the shut down and you GM guys have a throttle cable that gives problems also.
good luck
I didn't mention that I have and williams air throttle
JLL
Some old timers around these parts of Colorado say that using propane injection on their diesel engine is like adding another gear.
I have no experience using propane injection, but I know if it's done properly, it may achieve the result you're looking for, without causing any undue stress or harm to your engine.
HTH
Jay
87 SaftLiner
I assume that you are not trying to pull a 6 % grade in fourth or even third gear. If I recall correctly the last time I encountered a grade that steep I was in second gear. And I was pulling a trailer, although not 4400 lbs. I had no trouble. Therefore you are either not getting full throttle or there is something else wrong.
Fred M GM PD4106
Just re-read you post and I see you have an automatic so my apologies about being in the wrong gear.
Fred Mc.
I would take it back to the DD dealer that rebuilt it. There probably aren't to many mechanics that are good at running the rack any more. At least get them to check it. It would be a good idea anyway now you have broken it in.
Quote from: JLL on October 04, 2009, 12:56:11 PM
It's just about all I can do to make it up a 6% grade.
JLL -When you say the above, what road speed are you talking about?
Are you downshifting the transmission manually when you start to pull a grade?
What elevation are you at? Climbing a 6% grade from sea level is a whole lot different than one at 6,000 ft or more.
With N-65 injectors, the shop may have set the engine up for "A" timing, which also shifts the torque peak up the rpm range about 200 or so (1200 > 1400). This may or may not have some effect on your pulling ability with the Allison.
Have you weighed the coach? Besides having the correct numbers to accurately set your tire pressures, it will also give you some clue about what your climbing ability will be.
More help with more info. . .
FWIW & HTH. . .
;)
The sure way to find out how much power you do or don't have is a visit to a chassis dyno.
With that set up, on a 6% grade you should be in 1st gear with the engine around 2100 doing about 35mph. If you pull the gear shift lever down to 1st, and allow the transmission to get into 1st, with your foot on the floor and revved up, then pull your foot up about an inch, and you'll feel the transmission bump into torque converter lockup. This will allow you to pull a long grade with the torque converter locked up, without the tremendous heat of the torque converter slipping.
The only way you can get more power is to either propane inject it, or have the engine turbocharged. I can tell you that turbocharging and increasing the injectors to 75's REALLY wakes up the engine. I can pull hills about 15 mph faster then before. But-it is NOT cheap. Good Luck, TomC
What speed and altitudes do you pull those grades? I have pulled many grades for many miles with a worn out engine and a V730. I weigh ~25K empty. Around 10% and 9000ft I am crawling at 12 to 14 mph. 6% I was in the lower 20 range. I have an oversize seven core radiator (Stock is four core) and n70 squirters (wish I had smaller). What matters most is getting ride of the heat. You can shoe horn in a 1000hp beast but you will still be forced to limit you speed to the buses ability to shed the heat. BTW, it takes the same amount of energy and heat creation to climb a grade regardless of speed (I don't want to hear about the non-relevent variables guys). The way the bus survives it is to spread out that work and heat shedding over a longer period of time. So there where times I could go faster, but I had to reduce speed to keep the temps in check. I need to add an additional trans cooler (Hayden) to my system and I feel that I could do better. For more power and better climbing the hills, I like the 6V92 conversion. I have driven a 4106 6V92 n95, V730 through WV and it acted more like a car than a bus. It had a huge custom radiator and fan to keep it cool.