sodly

Mack E6, E7 vs their competition

35 posts in this topic

On 1/14/2017 at 11:01 PM, sodly said:

I've always been curious about the torque output on the 80s/90s E6 and E7 versus their typical competitor engines like the ubiquitous 350/400 Cummins or 3406 Cat.  I know the Mack sixes are lower on displacement compared to almost all the other manufacturers (why is this?).  But people always talk about how a Mack engine will "pull".  Some say their numbers were taken at the rear wheels while their competitors measured power/torque at the flywheel (which I find hard to believe).  I'm curious, for example, how a 350 Mack stacks up to a 350 Cummins.  I've driven Detroit and Cummins powered trucks but never anything with a Mack engine.  Do Mack six cylinder diesels produce more torque?  Or just more torque relative to their displacement?  When you pull the big hood on a Superliner and see a 350 E6 sitting there it just, honestly, doesn't look all that impressive.  Yet, they were very popular/common in that model.  There must be a reason why. 

Another thing I've noticed over the years is that Mack engines sound different than others, at least at idle.  Does anyone else fixate on this?  Obviously, a two-stroke Detroit sounds like nothing else.  But can you discern a 350 Cummins at idle versus a 350 Mack?  It's hard to put in words but I've always thought Cummins motors (at idle) sound a little "hollow" and "knocky", if that makes any sense.  There's a hollowness to their idle sound.  Whereas Macks, to me, sound more "growly"... more "truckish".  Maybe a little louder?  But different.  How would you describe the sounds of Cummins, Cats and Macks... in general?  

Sodly, thanks for asking these questions as I have wondered the same before. I have also wondered what were these Macks engine longevity compared to the bigger hp competition at the time?

My uncle in very mountainous Jamaica still has 74 Mack DM600 with a 237 engine, twin stick 5sp and 38k Mack rears that still works everyday with the original powertrain. Even though the engine has been overhauled it is still the original, and  the transmission has never been opened. Many trucks have come and gone since this Mack and the few other makes of the same vintage or from the 80s that have survived have had their engines replaced and other powertrain components. Everyone around there with a truck knows everyone else with one, so this truck and Macks in particular have this kind of reputation especially since there are not many Macks in that area.

I remember the bigger horsepower Cummins or CAT powered trucks being faster especially on the flats than even the 300hp plus Macks but the Macks even with their smaller displacement excelled on the steep or unpaved grades and other tough conditions fully loaded while 'screaming' less under pressure.

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As a kid I used to be fond of being able to tell different engines based on their sounds from even far away. Even some trucks with the same engine types had distinct sounds due to their individual exhausts etc. which allowed me to identify the owner.

When I was in recruit school, about the time rocks were invented, there was a large land fill on a hill adjacent to the fire academy. A friend and I would make bets on the make of the truck climbing the hill based on the sound of the engine before it became visible to us. The Maxidynes were almost too easy to pick out.

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On 7/13/2017 at 6:32 PM, Timmyb said:

Based on what you said, I'd recommend an E6. 

Just about any engine could do what your asking of it, including an e9 but it wouldn't be my first recommendation. 

I agree... it wouldn't be my first choice either.  But sometimes beggars can't be choosers.  I'm just wondering if I should pass on a seemingly good E9 truck just because of the engine.  I mean... a v8's cool and all but I don't want to inherit a future headache if the motor should ever develop problems (not likely, I suppose, with the light duty it would see with me).  Personally, I've always liked straight 6 motors of all flavors... diesel or gas.  An E6 350 with a 12 speed would be my druthers.

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One thing I learned a long while ago was MACK's power band was generally exactly where you needed it most. . .if the unit was spec'd out right. Which was when the salesmen were real truck people not ex Mac Donald's or Hyundai salesmen. .

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On July 15, 2017 at 8:44 PM, sodly said:

I agree... it wouldn't be my first choice either.  But sometimes beggars can't be choosers.  I'm just wondering if I should pass on a seemingly good E9 truck just because of the engine.  I mean... a v8's cool and all but I don't want to inherit a future headache if the motor should ever develop problems (not likely, I suppose, with the light duty it would see with me).  Personally, I've always liked straight 6 motors of all flavors... diesel or gas.  An E6 350 with a 12 speed would be my druthers.

My personal opinion is a motor is a bolt in part and they will all break at 1 point.  If the truck is exactly what you want and the price is where you want I'd go for it.  If its a good motor at the present time I'd be looking more at rust issues myself as a determining factor.    An inline could alway be swapped in if something happened and a rear gear change ain't that pricey around here.    

 

Strictly my personal uneducated opinion.   

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On 1/15/2017 at 8:14 AM, Lmackattack said:

My opinion was that the old E6 / E7 Mechanical 300s were just a very solid engine used for the job they did. they were not a powerhouse for over the road use but the little 676 cube 6cyl would hold its own against engines of 855 cube inch.  A 300 mack would run with a 350 cummins.  A 350 mack would run with a 400 cummins.  The macks had slight torque advantage even with a smaller bore/cube engine.

Gearing also has alot to do with it as Mack had widely used double reduction diffs and direct final drive transmissions.  Macks could put more HP/TQ to the wheels with their common gearing in use with Macks own drive train. 

That being said the old saying "There is no replacement for displacement" still holds true. In my opinion the cummins would pull long hills better. They had the displacement advantage to hold the Hp where the Macks would start to struggle and louse speed faster.

 I feel Mack lost the edge in the HP wars when they did not advance 6cyl engine engine options by raising their HP and Displacemet. Mack continued to push their 300 or 350HP small bore 6cyl diesel when all others 6cyl engine mfg were pushing their 400+ HP big bores...

 

just my .02

 

 

 

On 1/15/2017 at 9:06 AM, james j neiweem said:

Also I believe the E9 didn't catch on as well as it could have because of less than stellar performance of the earlier Mack V8's. Also V-8's in general are a little shy on torque and rely on HP(RPM) to get the job done. If Mack had made an 900 plus cubic inch six cylinder engine using the Maxidyne principal things may have turned out differently. They would have been well suited to todays 1000-1500 operating range.

I always wondered why Mack had a gap in their engine displacement between the 11 liter 6 cyl and 16 liter V8 while the competitor's 13 to 15 liter grew in popularity. Were they short on development funds or just thought their torquey 6 cyl would be enough as in many cases they did? It is  a pity their big 6 didn't make to the market.

Edited by Jamaican Bulldog

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Why no 900 cube Mack 6 cyl is probably a complicated question which involved sales, marketing, engineering, production and the board of directors which must balance the desires of all these bursaries. In hind sight it appears that a big cub Maxidyne would have successful given the big cube success of Cat and 60 series Detroit's. For what ever reason it appears to me that Mack went from top of the industry 80 plus years ago to being owned by Volvo. Mack had the big off road dump market virtually to it's self but quit around the time Cat started so Mack doesn't have any 5 million trucks to sell. Mack sold lots of trucks in the west when they were in Hayward and had a lock on the ready mix truck chassis business but they lost virtually all their business following the closure of the Hayward plant and the closer of dealerships. There are 6 or 7 Mack truck dealerships in California,  and a dozen Volvo dealerships with a Mack sign on the corner of the building, And, California being the 6th largest economy in the world and having the busiest ports in the US, and    my    local Peterbilt store having a small Mack and  Volvo sign on the corner of the building, maybe there won't be a Mack Truck in our future. 

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I am lead to believe the e7 was designed for a capacity increase. It was in an article I read, hopefully kscarbel2 can confirm this?

If it was indeed true, I wonder why it never happened?

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Did the e6 and e7 use the same block. I thought the e7 was just an increase in stroke over the e6 with a beefier bottom end.:mellow:

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12 hours ago, Timmyb said:

I am lead to believe the e7 was designed for a capacity increase. It was in an article I read, hopefully kscarbel2 can confirm this?

If it was indeed true, I wonder why it never happened?

Billy, I'm sorry to be late in replying. I'm wide open these days with a full plate of work.

We used to casually say that the E7 was the E6 made metric. Some truth to that.

I'm not aware of the E7 architecture having been planned to go from its 12-litre size to say 13-litres.

And back in 1987-88 when we were designing the E7 (launched in 1989), we really didn't have the 13-litre size on our radar. After all, our E6-350 4V could run circles around a 350hp Cummins and blow it away in fuel economy. Power, economy, durability.......what more can a 6-cylinder customer ask for?

Today, thanks to new technologies like CGI (Compacted Graphite Iron) engine blocks, we can easily get 450hp from an 11-litre block and 500-520hp from a 12-litre block. But realize the E7 was designed around the technologies on hand in 1987-88.

That said, we did improve (evolve) the E7. I did not like unit pump injection on it, or any other engine. EUP was a stepping stone. Common Rail was the ticket, solving a long list of problems with a relatively simple design and superb reliability.

Mack Trucks' E7 direct injection heavy-duty diesel engine is a four cycle, in-line six cylinder design. The 728 cu in. (12 1) engine is turbocharged and chassis mounted air-to-air aftercooled. The E7 is being introduced in 1989 with power ratings of 250 hp to 400 hp (186 kW to 298 kW) at 1700 to 1800 rpm, calibrated to 1990 EPA standards. Highlights of the E7 engine's design, development and performance are presented. Information is included which illustrates the strategies utilized to attain program goals of controlling weight and cost while extending power ratings, reducing emissions levels, and improving fuel economy, serviceability, durability and reliability.

http://papers.sae.org/892497/

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