8V71T injector size vs cooling requirement question...

bevans6 · March 24, 2012, 01:43:55 PM

I think I know the answer to this but I want to get some opinions from people who may actually have a clue...

I have the 8V71T with N80 injectors installed in my MC-5C, getting close to taking it out on the road. I suspect that I will have a bit of a cooling problem, the 5C radiators are a little smaller than the MC-9 and the engine with those injectors is rated at 400 hp gross, 350 hp net. I have a long term plan to rectify that if I need to, but since I am moving to Nova Scotia I have packed my shop, so I won't be able to fabricate a new radiator, plumbing, mounts etc, nor will I have time... This move is rolling, it's on a down hill stretch and it don't have brakes...

Now my idea - I have a nice set of perfectly good N65 brown tag injectors sitting in a box on the shelf. If I do find I have an over-heating problem I thought that I might swap those injectors in just to get by. The idea is from the 8V71T data sheet that shows one version was with N65 injectors and it made 308 hp gross - just a tad more than the N65's made in my 8V71N. I figure the turbo engine at that hp level will cool about the same as the natural engine did, which was just fine, so I could do that swap pending me having the time and effort needed to install more radiator.

What do you think? What would I set the injectors at, do you think? Anyone have a manual with tune up data for an 8V71T with N65's? The goal here, to be clear, is driving the 1200 miles between here and my new home in Nova Scotia without overheating, just once...

Thanks, Brian

RickB · March 24, 2012, 01:53:53 PM

Brian,

Les fuel=less heat. Seems to me if you're concerned and you can run the rack your self it may be a good idea. If not, make sure you have an IR gun for the trip and travel at night if you can.

Something tells me Clifford or Don will have the tune specs.

Rick

lostagain · March 24, 2012, 04:15:51 PM

Brian,

this is just from experience driving those buses for a lot of years. And I am sorry this is not black and white numbers that you are probably looking for, but here is my not-so-learned opinion, LOL: it will not overheat unless you are driving up a hill in hot summer temperatures. So, if it is less than 25C (80F) at the time of your move, you might not have a problem.

I would set the N65s at 1.484". I am sure the real mechanics will chime in with their advice, which is better than mine.

And as an aside, but related to your concern, my 5C has squirrel rad blowers that are about 12" diameter, with a pulley which is about 8.5" dia., which IIRC the PO told me is off of a MC9, for stronger air flow through the rads.

Hope this post is OK. Just trying to help. You have to be carefull what you say on this board lately, LOL.

JC

thomasinnv · March 24, 2012, 06:16:45 PM

Brian I am assuming since your engine is turbo'd that it has standard timing. Set the brown tag N65's at 1.484" or the white tag N65's at 1.460" according to "da book". If you do happen to have advanced timing, well then that changes things a bit.

luvrbus · March 24, 2012, 06:53:39 PM

Hey guys he has military spec turbo engine monster of a turbo takes a lot of fuel and heat to turn that baby best if he just leaves it alone till he gets the right turbo he installs the 65 with his turbo it will just be a problem for him.

RJ · March 24, 2012, 08:22:06 PM

Brian -

Biggest reason for overheating an MCI is the weight of the right shoe on the throttle.

If you see black smoke out the exhaust, back off.

Simple.

Enjoy the journey!

FWIW & HTH. . .

buswarrior · March 24, 2012, 08:23:02 PM

Well, I'm just a bus driver...

I'd not waste my time changing out injectors on a coach that I'm driving myself.

Moderate your own use of the excess heat generating power.

As noted, it won't be a problem running on the flat, it'll be on the bigger hills.

Watch the temp gauge, and back off from the max it can climb, keep the revs high for better cooling by dropping a gear more than it needs, throw on the 4 ways, pretending to be underpowered, and over the top with a cool engine you go.

The old trick of slowing down sufficiently that you can accelerate pays off on all equipment, 2 or 4 stroke.

And use the time for packing more boxes in a more relaxed manner?

happy coaching!
buswarrior

Homegrowndiesel · March 24, 2012, 09:06:03 PM

X3 right foot controls the heat.

bevans6 · March 25, 2012, 04:29:57 AM

Welcome advice, guys, I appreciate it! I do indeed have the ability to back off a bit from max power, and I can always drive at night if I have to!

Brian

TomC · March 25, 2012, 07:42:53 AM

You know how the bus performed before with the non turbo engine. Just allow the bus to slow down on hills and down shift to keep the rpm's up high to keep both the water pump and radiator fan pumping the most. I wouldn't change the injectors. If you see the temp coming up, back off the throttle or even pull over to let it cool off (with the engine running) for 5 minutes. Don't let the temp go above 210 degrees-I stop when it gets to 200. You'll be fine. But for best summer driving, install the biggest radiators you can fit-like the 8V-92 radiators. Good Luck, TomC

thomasinnv · March 25, 2012, 09:32:18 AM

Quote from: luvrbus on March 24, 2012, 06:53:39 PM
Hey guys he has military spec turbo engine monster of a turbo takes a lot of fuel and heat to turn that baby best if he just leaves it alone till he gets the right turbo he installs the 65 with his turbo it will just be a problem for him.

Yes, I overlooked that little tid bit of information. It seems me sometimes forgets to not open me mouth when me knows not of what me speaketh. Classic disease of foot in mouth.