Bus Conversions dot Com Bulletin Board
December 19, 2014, 07:41:15 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
News: If you had an Online Subscription: It will not get torn up or crushed if you back over it with your bus.
   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 3852 times)
RJ
Former Giant Greenbrier Owner
Hero Member
*****
Offline Offline

Posts: 2879





Ignore
« Reply #15 on: July 30, 2008, 10:19:03 PM »

JC,

Lost Again 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



John -

Here are a couple of interior photos of JC's coach for you to drool over, and yes, you did see it at Rickreall - that's where I took these pics.


Logged

RJ Long
PD4106-2784 No More
S13406 Now
Fresno CA
TomC
Hero Member
*****
Offline Offline

Posts: 6971





Ignore
« Reply #16 on: July 30, 2008, 10:32:15 PM »

What RJ said about finding a junk yard 8V-71TA is a good one-although they are a rare bird since they came out about the same time as the 6V-92TA, with most using the 92 instead.  The only difference between my non aftercooled originally naturally aspirated 8V-71 and the 8V-71TA is pistons and aftercooler.  Since I'm using low boost, the two piece 18.7 pistons with transit rings work well.  The engine starts faster when cold, I have the bypass blower like the turbo motor, and the air to air intercooler is WAY more cooling than the stock aftercooler under the blower in the V of the block.  Personally-if you're going to do this as a winter project, I would use your existing engine and rebuild it up into a turbo with the air to air intercooler in the right engine door.  The intercooler will take alot of heat off and if you go to a mild injector, like no bigger than a 75 like I have (some guys will go to 90's in the 8V-71), you'll have a very nice performing bus.  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
quantum500
Full Member
***
Offline Offline

Posts: 146




Ignore
« Reply #17 on: July 30, 2008, 10:37:11 PM »





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. . .

To add to the soapbox on the other end....I think its totally bogus that MCI developed such a poor cooling system.  I have ran several detroit power units over the years that where stationary, screaming their guts out, blowing smoke, lugging ......you get the picture that never ever over heat.  Unless the radiator is totally plugged up.  One is almost 50 years old.  Honestly if they where built right according to DD spec we should be able to hold the pedal down when ever where ever.  That of course is not the case.  Everything has to be in tip top shape and maybe a few band-aids put in place for good measure.  I'm in the process of working with a heating issue with just a slightly older MCI.  I'm going to try water/meth injection + a big trans cooler and see what happens.  I have searched and pried and asked and nobody to my knowledge outside of the drag strip guys have used water/meth on a detroit.  I have a 8v71n with brown 65 injectors.  Tends to blow some smoke at WFO and as I found out yesterday the throttle linkage hinders that even.  I have a 1/4" more to go!
The only time that I did not have heating issues is with a plugged fuel filter.  The last thing I'm going to do is change injectors so don't mention it.  The system that I'm putting together is going to deliever 12GPH@2500psi.  Should wake it up if nothing else.  It runs pretty good already.  I'll keep everyone posted.  Cross your fingers for the silver bullet.
Logged
rusty
Sr. Member
****
Online Online

Posts: 363





Ignore
« Reply #18 on: July 31, 2008, 06:40:32 AM »

  Rick B  I live north of Denver, south of Johnstown. I don't know anything about MCI's I like to mess around with Eagles (don't hold that against me). If your up in my area stop by. Welcome to Colorado the front range is a pretty nice place to live.
                         Thank You Wayne
                         303-591-0372
Logged
RickB
Hero Member
*****
Offline Offline

Posts: 1079


81 MCI 9 smooth side 8V71 Allison 754




Ignore
« Reply #19 on: July 31, 2008, 07:31:29 AM »

In response to the earlier post about my inability to maintain a reasonable speed from Sterling to Denver. The whole reason I want to modify my 8V71 is that is not a reasonable speed when encountering a very slight  grade in my opinion. The slowest you can legally drive that road is 40 and I know I dipped below that a number of times. But truth be told, I don't have a problem with the fact that I can't accelerate or clear the hill at 70 mph plus and I am constantly having to deal with lack of power with ANY grade at all, but a "reasonable" experience would be not having to stare at my temp gauge with white knuckles and pure fear every time I approach a long pull of any circumstance. I dropped the bus to first and I struggle to floor my accelerator under the best conditions, so I really think if anything I was babying my motor too much. I will not continue to own my bus if that is the experience I am going to go through everytime I want to go anywhere. I have avoided the mountains with both of my buses and have finally come to the conclusion that if there is an affordable alternative I would like to pursue it.
I have driven series 60 Prevosts up mountain grades and they are accelerating at the top of most of them. I don't think it's too much too ask of a bus/motor combo to at least not appear to be blowing up when you reach the top of any grade at 5 mph. We are driving north to Loveland later today and I am grateful that the drive there is fairly flat. Another 90 plus day here at the edge of the Rockies. I wish I could catch a temperature break , but it appreasr our drive back to Nashville this weekend will be ridiculously hot... Oh well...
Logged

I will drive my Detroit hard... I will drive my Detroit hard.
skipn
Guest

« Reply #20 on: July 31, 2008, 08:09:07 AM »


 RickB,

    After reading the prior responses I'm going to suggest (sacrilege) if you are going to spend 13k+ (from TomC method)
 you might consider going to a RTO 4 stroke........ Tongue

   At the 300hp range cat 3306 or Cummins LTA10 in factory configurations. The engines are fairly priced
 at around 5k-7k (with dyno reports).  You would probably also need a different tranny. Lots of choices but
 would need to be shorter than the 700 series Allisons.

   Just a thought.
  Skip
Logged
edroelle
Sr. Member
****
Offline Offline

Posts: 351


1998 Royale Prevost




Ignore
« Reply #21 on: July 31, 2008, 08:11:26 AM »

Rick,

I had the same problem as you when I had an MCI 8, 8V71, and traveled in the Rockies.   (I had to run WOT, first gear, 19 MPH, to prevent overheating.)   I then installed a truck 8V71T.  There was a lot of change-over of parts on the engine.  I took a lot of time, but I may have been too meticulous.  I also changed to the "102 radiators" PN 6K-1-5 from Diesel Radiator in Chicago, small fan pulley (7 3/4" diameter, and large fans with the outlets opened-up.  I got many of the parts at a local bus company in their own junk bus yard.

The aftercooler 8V71 blocks are hard to find. 

TomC is one of the only air to air intercooled 2 cycle units I have heard of.  I may be out-of-tune, but if there are more, there probably are not many.  Theoretically, that is a good approach.  However, I think you should install the intercooler somewhere other than the engine compartment, blowing out.  The reason is that you are looking to cool the air.  The air from the engine compartment has been heated by the radiators and the engine.  You would gain more by pulling from a fresh air supply.

Even without aftercooling or air to air intercooling, you could get 350 HP, plus the advantage of the turbo in mountains at altitude.

Ed Roelle
Flint, MI

Logged
TomC
Hero Member
*****
Offline Offline

Posts: 6971





Ignore
« Reply #22 on: July 31, 2008, 09:14:27 AM »

Instead of using any air to air intercooler or aftercooler, I would suggest you go no higher than the N65 brown tag injectors-then you don't need the aftercooler.  Then with a low boost-like 5psi, you'll have sea level performance like a normal 318 at any altitude.  If my engine had performed like that, I would have been satisfied.  The bigger injectors are nice, but using the smaller injectors (N65's) will still boost your power from 300hp and 800lb/ft to 325hp and 975lb/ft of torque.  Good Luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
quantum500
Full Member
***
Offline Offline

Posts: 146




Ignore
« Reply #23 on: July 31, 2008, 09:22:50 PM »

If you were to do that and use the N65 injectors with a turbo do you think that you would generate more or less heat compared to a natural with the same injectors?  I'm thinking less heat and more power, just because your combusting all the fuel instead of blowing it out the valves/head.  Correct me if I'm wrong.
Logged
lostagain
Hero Member
*****
Offline Offline

Posts: 1616


MC5C




Ignore
« Reply #24 on: August 01, 2008, 07:51:15 AM »

With my limited experience, I'm thinking that you would generate more heat, because more air from the turbo will burn more fuel that would otherwise go out the exhaust as black smoke. More combustion makes more heat, which increases the velocity of the exhaust gases through the turbo turbine, which makes it draw more air with the compressor wheel to make more boost, etc, etc.

In practice, the turbo on my bus (same N65 injectors as before) hasn't increased temperatures noticably.

FWIW

JC
Logged

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

Posts: 146




Ignore
« Reply #25 on: August 01, 2008, 03:27:42 PM »

I know for a fact that less black smoke = less heat at the manifold.  I do not know weather or not that puts the heat into the engine.  I know the sled pullers and drag racers can reduce egt's with more boost.  So kind of confusing thats why I asked.
Logged
TomC
Hero Member
*****
Offline Offline

Posts: 6971





Ignore
« Reply #26 on: August 01, 2008, 10:59:31 PM »

That's mainly because- if you have no black smoke, all the combustion is happening in the combustion chamber.  With black smoke, combustion is still happening when the valve opens and exhaust is still burning in the exhaust manifolds.  Good luck, TomC
Logged

Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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!