Bus Conversions dot Com Bulletin Board
July 24, 2014, 08:21:45 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If you had an E-Mag Subscription: The dog will not eat it.
   Home   Help Forum Rules Search Calendar Login Register BCM Home Page Contact BCM  
Pages: [1] 2  All   Go Down
  Print  
Author Topic: Alright Tom C, I am ready to hear about your low boost turbo 8V71 mod  (Read 3615 times)
RickB
Hero Member
*****
Offline Offline

Posts: 1047


81 MCI 9 smooth side 8V71 Allison 754




Ignore
« on: July 30, 2008, 08:32:57 AM »

Tom and all you other busboys,
After much thought and a failed attempt to clear the Rockies. (200 degrees on the gauge at the top of the first first pass, I turned around and took the car instead, also one head was considerably hotter than the other when I used my IR gun??? any thoughts?)
Brian Diehl gave me a realistic view of the work and money involved in a repower and I have decided that if we are relocating to Denver that I still have no choice but to search for more horsepower and your low boost mod and bigger injectors seem like the least expensive/ least difficult option.
Can you give me an idea of what turbo you used and any other parts I may need to start looking for?

I am imagining you are quite happy with the results, if you aren't please let me know. The altitude here in Denver and beyond are hell on my bus but my joints and back feel like I am 18 again. The pull starts in Sterling Colorado and  never really stops until you are clear on the other side. That 2-3% constant rise into Denver just sucked...struggled to maintain 45-55 mph
Thanks for your words of wisdom in advance.  Rick
Logged

I will drive my Detroit hard... I will drive my Detroit hard.
JohnEd
Hero Member
*****
Offline Offline

Posts: 4571




Ignore
« Reply #1 on: July 30, 2008, 10:01:24 AM »

Rick,

I think you did the prudent thing in turning around.  Share what all you have done to the cooling system?  When were the thermostats changed?

If you add power....turbo OR bigger injectors will either do that....you will need more cooling than you have at present.  If your rads are clean in and out, thermostats are new, pump is good and trans cooler is augmented with an air to air and fans are good.....wouldn't that mean you have a tired 8V71?  Open the air box and look at the skirts to verify piston condition?  Do a compression check?  If the compression is good does that mean that the engine itself shouldn't be contributing to any cooling issue?  If your injectors are old and out of balance I think that will contribute to power loss, poor efficiency and overheating......and might even show up as one head running hotter.  More specific questions to answer anyway.

There must be three stock rads that are bigger than the stock 8V71 item.  I have read where the new oversized custom 8V92 items ran $1,400 each.

Good luck and I am looking forward to the experts opinion as this has been gone thru many times.

John
Logged

"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
Lonnie time to go
Lonnie
Sr. Member
****
Offline Offline

Posts: 301

Saginaw, Michgan




Ignore
« Reply #2 on: July 30, 2008, 11:05:46 AM »

First i will say i am no expert
From all the people i have talk with just in the last few months I can say this.
Your temp. of 200 degree may be ok and very normal in the mountains. I think at about 210 degrees his when you worry. Also you mentioned that you where trying to go 45 to 55  mph .  This is a high speed with the 8V71.  Shifting down to a lower gear might have pushed you over the mountains with little worries. There is some chance that a air scoop might work.  This is done on the roof and channels air into the motor to help.  I don't know how well it works but i have heard good things.
.
You should know this is the info i have read on the threads in this forum. None of what i say is based on experience.  But the people in the forum and in the chat groups are very helpful.
.
.
Logged

1976 4905
lostagain
Hero Member
*****
Offline Offline

Posts: 1505


MC5C




Ignore
« Reply #3 on: July 30, 2008, 12:34:22 PM »

My engine (4-71 DD) used to smoke at altitude or just accelerating with my foot down.

I fabbed a ram air for the intake out of sheet metal. It worked remarkably well: no more smoke above 20 mph. That little extra air was enough to burn the fuel used. No increase in power though.

Then I installed a turbo, a Garrett Airesearch spech'ed for my engine, I can't remember the details now. ( I removed the ram air). I get 8 psi of boost and it makes a great difference. I go up the hills one gear higher than before, ( 5 speed manual). I go up the slight inclines in 5th now where I used to have to downshift for them. In short, I keep up to traffic now. I am tickled pink. The turbo gives you more torque down lower in the mid rpm range so you can hold a given gear longer. The only mod. I did was put in the better oil seals in the blower. (The older style would not have withstood the extra boost). I kept the same old injectors ( N65), so not using any more fuel, I don't create any more heat than before. I kept the same old one piece pistons. The whole thing looks simple enough, but I spent several hours fabricating and head scratching to make it all come together: adaptors, flanges, intake and exhaust plumbing, etc. I installed it on the end of the exhaust manifold on the side of the engine so I didn't have to raise the bedroom floor. BTW, I kept the old oil bath air cleaner, which works very well, in spite of what some mechanics, mostly the young ones, were telling me. I have been driving it this way for 2 summers now (+- 10 000 miles) and it works great. Highly recommend doing it.

I dream of some day doing a rebuild with the turbo pistons, bigger injectors, etc, but of course that would involve a bigger radiator and less fuel mileage...
Logged

JC
Invermere, BC
1977 MC5C, 6V92/HT740
makemineatwostroke
Guest

« Reply #4 on: July 30, 2008, 02:59:56 PM »

RickB 1 thing to consider is a 8v71N will lose about 3% of it's HP every 1000ft in altitude and they will get hot trying to burn fuel with out enough air. The 8v71 has pushed the Greyhounds and Trailways over that mountain range for years with out a turbo fwiw
« Last Edit: July 30, 2008, 03:07:44 PM by makemineatwostroke » Logged
RickB
Hero Member
*****
Offline Offline

Posts: 1047


81 MCI 9 smooth side 8V71 Allison 754




Ignore
« Reply #5 on: July 30, 2008, 05:51:25 PM »

I believe the radiators were gone through when the bus was converted (less than 25k miles ago). 180 degree stats just put in 2k ago. The blower seals are definitely in need of replacement (blue smoke for first mile or two) the motor has been checked out by some great mechanics and they all sat she is a good runner. I think pushing around 35000 lbs up and over a ten mile 8% grade on a 90 degree day is just asking too much of a tame tuned 8V71. I bet my current top HP is around 270 or so. I would like to see that jump a bit. I am expecting that Tom has the part numbers for the radiator and other extras he decided on. We are driving to Loveland from south Denver early tomorrow morning because whenever we are on the road record heat is sure to follow (longest stretch of 90 plus days in history thank you very much...)
I am not trying to be argumentative but if I was a driver for Greyhound and didn't have to pay to rebuild a motor if it blew up back in the 70's, I wouldn't have hesitated to drive further but when it's your checkbook paying for repairs 200 degrees is where I start to stress out.
Rick B.
Logged

I will drive my Detroit hard... I will drive my Detroit hard.
TomC
Hero Member
*****
Online Online

Posts: 6668





Ignore
« Reply #6 on: July 30, 2008, 06:05:20 PM »

Rick- I had Don Fairchild in Bakersfield do the work, since my bus was the first he'd seen using an air to air intercooler (Sierra Technologies out of Tulsa, OK).  I have about 8" of space between my side radiator and the side of the bus (transit 102" wide) I just installed the air to air intercooler against the radiator-like what a big rig has.  You could use two smaller ones perhaps in front of each radiator, or just mount it in the right engine door with a couple of electric radiator fans pushing the air out.  
The first thing Don checked was what piston rings I had and they were the tight transit rings that can take the mild boost I'm using (about 15psi).  If you have the more sloppy over the road rings, those will have to be changed otherwise you'll get too much blow by.  I get very little blow by with this setup.  Don used an early 12.7 liter Series 60 turbocharger with waste gate to better control the boost.  It's a little slow on take off, but works well once warmed up and rolling.  The injectors were changed from brown tag N65 to 9G75's.  I figure my horsepower is 375 with torque at 1125lb/ft (compared to 300hp and 800lb/ft with the N65's).  Also, Don installed the bypass blower valve kit.  I ultimately changed my radiator from a 5 row straight fin to a 6 row serpentine fin; changed the air cleaner from a 6" to a 7" outlet; changed the 5" muffler to a turbo rated muffler; installed a fuel modulator to keep the injectors from opening until turbo boost is up.  All in all it was a big project, about the cost of an overhaul ($13,000.00) but the difference in power is quite noticeable.  I'm not affraid to go up any mountains now.  Last year went to Mammoth at 8,600ft elevation, did not notice any power drop, and no smoke except from the stop light. The fuel mileage is still in the 5-6.5 range, but with the better performance, I don't care.  I did have to put on 15 misters tied into my water system since I have the largest radiator, and also added an auxiliary transmission cooler with fan.  But I'm quite sure that if you get the 8V-92TA radiators with the big squirrel cage blower, you'll be fine.  Good Luck, TomC  

P.S.-what injectors do you have now?
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
RickB
Hero Member
*****
Offline Offline

Posts: 1047


81 MCI 9 smooth side 8V71 Allison 754




Ignore
« Reply #7 on: July 30, 2008, 06:15:55 PM »

Tom, thanks for the great info. I don't know yet what injectors I have. I am on the road and plan to tear into this project over the winter. I am sure i'll need pix and info from time to time.
Logged

I will drive my Detroit hard... I will drive my Detroit hard.
JohnEd
Hero Member
*****
Offline Offline

Posts: 4571




Ignore
« Reply #8 on: July 30, 2008, 06:32:31 PM »

JC-Lostagain,

A 4-71 with a 5 speed manual in an ARROW dynamic MCI?  Just what kind of MPG do you get out of that?  Shocked Grin Grin Grin

Thanks,

John
Logged

"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
luvrbus
Guest

« Reply #9 on: July 30, 2008, 06:59:07 PM »

Rick,why not use the factory after cooler they work and can be bought for a 100 bucks I  installed a air to air on my 8v92 and don't see that much of a improvement for 2 grand and anything you put in front of a radiator on a MCI causes heating problems because their system is marginal to start with
Logged
lostagain
Hero Member
*****
Offline Offline

Posts: 1505


MC5C




Ignore
« Reply #10 on: July 30, 2008, 07:45:49 PM »

JohnEd, as a matter of fact, when we had this bus at Brewster's (Banff, Alberta) in the Seventies it was no. 9, and we called it "The
Rocket", partly because most of us Canadian drivers were into hockey, and no. 9 was "Rocket" Richard's jersey number with the Montreal Canadiens. I still have that number on the bus, and it still lives up to it's name...

JC
Logged

JC
Invermere, BC
1977 MC5C, 6V92/HT740
lostagain
Hero Member
*****
Offline Offline

Posts: 1505


MC5C




Ignore
« Reply #11 on: July 30, 2008, 07:51:51 PM »

Oh and I forgot, I get about 12 to 13 mpg (Cdn), 10-11 mph (US)
Logged

JC
Invermere, BC
1977 MC5C, 6V92/HT740
quantum500
Full Member
***
Offline Offline

Posts: 146




Ignore
« Reply #12 on: July 30, 2008, 08:39:23 PM »

Rick- I had Don Fairchild in Bakersfield do the work, since my bus was the first he'd seen using an air to air intercooler (Sierra Technologies out of Tulsa, OK).  I have about 8" of space between my side radiator and the side of the bus (transit 102" wide) I just installed the air to air intercooler against the radiator-like what a big rig has.  You could use two smaller ones perhaps in front of each radiator, or just mount it in the right engine door with a couple of electric radiator fans pushing the air out.  
The first thing Don checked was what piston rings I had and they were the tight transit rings that can take the mild boost I'm using (about 15psi).  If you have the more sloppy over the road rings, those will have to be changed otherwise you'll get too much blow by.  I get very little blow by with this setup.  Don used an early 12.7 liter Series 60 turbocharger with waste gate to better control the boost.  It's a little slow on take off, but works well once warmed up and rolling.  The injectors were changed from brown tag N65 to 9G75's.  I figure my horsepower is 375 with torque at 1125lb/ft (compared to 300hp and 800lb/ft with the N65's).  Also, Don installed the bypass blower valve kit.  I ultimately changed my radiator from a 5 row straight fin to a 6 row serpentine fin; changed the air cleaner from a 6" to a 7" outlet; changed the 5" muffler to a turbo rated muffler; installed a fuel modulator to keep the injectors from opening until turbo boost is up.  All in all it was a big project, about the cost of an overhaul ($13,000.00) but the difference in power is quite noticeable.  I'm not affraid to go up any mountains now.  Last year went to Mammoth at 8,600ft elevation, did not notice any power drop, and no smoke except from the stop light. The fuel mileage is still in the 5-6.5 range, but with the better performance, I don't care.  I did have to put on 15 misters tied into my water system since I have the largest radiator, and also added an auxiliary transmission cooler with fan.  But I'm quite sure that if you get the 8V-92TA radiators with the big squirrel cage blower, you'll be fine.  Good Luck, TomC  

P.S.-what injectors do you have now?

I wonder if you could use water/meth injection instead of the intercooler/aftercooler approach?  Lots cheaper, lots simpler and from what I have read more cooling capacity. 
Logged
JohnEd
Hero Member
*****
Offline Offline

Posts: 4571




Ignore
« Reply #13 on: July 30, 2008, 09:27:34 PM »

JC,

Lostagain looks like a great bus.  I envy you her anmd I would like to see some of interior, if possible.  Thanks for the numbers and I find them very believable.

Were you at Rickreall?  I didn't stop but I think I saw her there on the last day late.  I did no more than cruise the lot but there were some nice busses and some that I think I recognized.

Again, thanks,

John
Logged

"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
RJ
Former Giant Greenbrier Owner
Hero Member
*****
Offline Offline

Posts: 2776





Ignore
« Reply #14 on: July 30, 2008, 10:09:28 PM »


After much thought and a failed attempt to clear the Rockies. (200 degrees on the gauge at the top of the first first pass, I turned around and took the car instead, also one head was considerably hotter than the other when I used my IR gun??? any thoughts?)

That 2-3% constant rise into Denver just sucked...struggled to maintain 45-55 mph




Rick -

The overheating problem that plagues many of our buses can often be traced back to poor maintenance and the amount of weight forced upon the throttle pedal under gravity-fighting operating conditions.

There's no reason you should have had to turn the coach around on that recent run, other than the fact you were probably pushing it too hard in too high a gear for the altitude.  You say yourself that you were struggling to maintain 45 -55 mph.  What was your hurry??  If you'd dropped another gear and kept the engine in the 1800-1900 rpm range on a partial throttle, you'd have gone right on up and over without any problems.  And all it would have cost you is a little time - maybe an additional 10 minutes or so.

I used to climb Baker grade out of Barstow, CA on the way to Las Vegas in MCIs equipped with your powertrain in the middle of summer with temps often over 100, and never once had one overheat on me.  That also included the MC-9s that had 8V71 turbos hooked to the HT-754s.  Why?  Because you don't want it to shut down on you with 45 passengers on board in 100 degree weather, that's why.  How? You go down another gear and enjoy the sights while keeping a mindful eye on the tach and the temp gauge.  The folk on board might grumble a little, but they'd grumble a whole lot more if you were parked alongside the road with a hot engine.  So you go slower in the right gear. . .

Now, to get off my soapbox. . .



Be very aware that MCI cooling systems are marginal at best, even with the big 8V92 cores.  Besides the larger cores, when equipped with 8V92s MCI also installed much larger squirrel cage blowers, changed the squirrel cage drive pulley to a smaller diameter, and a host of other small details to try and keep the beast from self-destructing. . . and they still had problems, especially with the CA emission engines.  One of the ways they solved the problem was to simply not offer the 8V92 engine in MC-9 coaches to be sold in CA new, for a brief period of time.  Once 9 production ended, and the A-series were rolling off the lines, the 8V92 was re-instated, since the A's have somewhat larger cooling compartments, among other changes.

I wouldn't, however, recommend putting an air-to-air intercooler in front of the radiators on your model MCI - they struggle enough as it is.  Tom's suggestion of mounting it on the RH rear side service door and using electric- or hydraulically-driven fans is a good one.

That being said, what Tom's done to his engine is very similar to a stock 8V71TA, which was an option in the MC-9s.  They came from the factory with 350 hp in coach trim, 375 if you were going to put them in an 18-wheeler.  So it's entirely possible - if the factory can do it, so can you.

Since yours isn't broke, I'd like to suggest that you don't fix it - right now.  Instead, shop for an 8V71TA in some of the truck boneyards that should be in the Denver area.  Buy a complete truck tractor unit with that engine, pull what you need and sell/scrap the rest.  Then get it rebuilt to 350 or 375 hp specs before shoehorning it into your coach.  While it's being rebuilt, begin your quest for the larger squirrel cage blowers and blower drive box, as well as the radiator cores.  Think Sam Caylor. . . 

In other words, keep using your coach "as is" until the hot rod motor and it's cooling system are all ready to go. 

Another thought comes to mind:  Do you know how heavy your coach actually is, in "road-trip-ready" trim?  If not, take the time, ten bucks or so, and go have it weighed.  Make sure you get readings for all three axles.  Once you have your readings, put your coach on a diet and determine how much can be jettisoned and still make travel enjoyable.  Then weigh it again so you can adjust the tire pressure according to the tire manufacturer's inflation charts for the approximate load each tire's carrying.  Don't forget to add a little to compensate for "stuff".  By putting your coach on a diet, you'll help that hard-working 8V somewhat, and, as a bonus, you might get slightly better fuel economy - from 5 to 5.1 perhaps?

Big picture?  The idea of putting a low-boost turbo on your engine is a good one, with the benefits outweighing the negatives, providing you pay attention to the details.

That and enjoying the beautiful Colorado scenery more as you travel.   Shocked

FWIW & HTH. . .

 Wink
Logged

RJ Long
PD4106-2784 No More
Fresno CA
Pages: [1] 2  All   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.18 | SMF © 2013, Simple Machines Valid XHTML 1.0! Valid CSS!