Pm From Mackcl96

[fjh]

I had a pm from mackcl96 asking if rear wheel horse power was the advertised HP for mack trucks at one time! I accidently deleted your pm brother sorry!Anyway My answer and I will stand corrected but to the best of my memory The fly wheel horse power was the advertised HP of the truck It would be a unfair and hard to compair against other vendors engines otherwise! Having said that for quite some time duing the 80s and early 90s all the trucks came with a dynotested tag in the window Its anyones guess if they actually draged full HP out of them on the dyno before sending the trucks out!I do know also we had the odd customer take em to task on the HP of the odd V8 bitching about no power to find the 500 hp engine would be making 488 /470 to the ground which aint to shabby for an un touched engine.The guys at the dyno place also comented that you could put a cup of coffee on the hood while dynoing and it wouldnt budge where other engines would shake the dam thing off the hood!

[mackcl96]

I had a pm from mackcl96 asking if rear wheel horse power was the advertised HP for mack trucks at one time! I accidently deleted your pm brother sorry!Anyway My answer and I will stand corrected but to the best of my memory The fly wheel horse power was the advertised HP of the truck It would be a unfair and hard to compair against other vendors engines otherwise! Having said that for quite some time duing the 80s and early 90s all the trucks came with a dynotested tag in the window Its anyones guess if they actually draged full HP out of them on the dyno before sending the trucks out!I do know also we had the odd customer take em to task on the HP of the odd V8 bitching about no power to find the 500 hp engine would be making 488 /470 to the ground which aint to shabby for an un touched engine.The guys at the dyno place also comented that you could put a cup of coffee on the hood while dynoing and it wouldnt budge where other engines would shake the dam thing off the hood!

QUOTE fjh

I beleive that was just rumor more than anything.After all gear ratios can change things sum what and then were not comparing apples to apples.Having said that ,the trucks all used to come in with dyno tested tag on the window up till just after the E9 era they kind of droped that mid way thru as the E7 came along!

I did get it

Thanks,

Heard this from a few old timers but cant believe it can be true, with like you say, and wheel base kills horsepower,single axle over tandem, Rockwell over Mack carriers.

It came up in another site, so I asked other member's here and they thought it was true on older Mack's

Very few of the Mack's at the dealer I worked at were Dyno'ed in the early 80's because we picked them up at

the factory and we marked road tested on the door tag.

But then we had a long pre-delivery sheet not like today

Also 1 out of 10 broke on the way up because of a block heater o-ring didn't seal

still see dyno tags but might be engine only

[mackcl96]

I just copy and pasted our (teenage texting jibber) but I going to ask in English for the other 3,000 members

Did Mack at one time use horsepower numbers to ground?

Some people think a 237hp is to the ground that would mean it's 305 at the flywheel

so that means a 350 is 425

[bts-4120]

I just copy and pasted our (teenage texting jibber) but I going to ask in English for the other 3,000 members

Did Mack at one time use horsepower numbers to ground?

Some people think a 237hp is to the ground that would mean it's 305 at the flywheel

so that means a 350 is 425

thats what I always heard but only on the Maxidyne engines

[GearheadGrrrl]

I suspect there may be something to that rumor. For examples, the EM6-300 was given 4 valve heads and had it's displacement increased from 11 to 12 litres but the horsepower rating was never increased from 300. On the road, I've found that 237s will keep up with the 14 liter 290/300 Cummins or 8V71 Detroit, and would run away and hide from the L10 Cummings or 6-71. The 285 and 300 Macks would likewise run with a 350 Cummins. I worked for a while for a bulk hauler that ran 425 Cats with the exception of one 350 horse Mack, and the Mack could keep up with the Cats. So clearly Macks will run with other brand engines with 10 to 20 percent more rated horsepower- that's about the driveline losses of a class 8 truck.

[Lmackattack]

the older maxidynes were measured in brake hp. Brake HP is measured at the flywheel and does not compensate for drivetrain losses.

Trent

[mackcl96]

I suspect there may be something to that rumor. For examples, the EM6-300 was given 4 valve heads and had it's displacement increased from 11 to 12 litres but the horsepower rating was never increased from 300. On the road, I've found that 237s will keep up with the 14 liter 290/300 Cummins or 8V71 Detroit, and would run away and hide from the L10 Cummings or 6-71. The 285 and 300 Macks would likewise run with a 350 Cummins. I worked for a while for a bulk hauler that ran 425 Cats with the exception of one 350 horse Mack, and the Mack could keep up with the Cats. So clearly Macks will run with other brand engines with 10 to 20 percent more rated horsepower- that's about the driveline losses of a class 8 truck.

Oh I hear you, here is my input

I suspect there may be something to that rumor. For examples, the EM6-300 was given 4 valve heads and had it's displacement increased from 11 to 12 litres but the horsepower rating was never increased from 300

.

Mack Knew that 300hp was bulletproof and gave peek torque numbers. Mack was stubborn in changing what worked for decades.

I've found that 237s will keep up with the 14 liter 290/300 Cummins or 8V71 Detroit, and would run away and hide from the L10 Cummings or 6-71. The 285 and 300 Macks would likewise run with a 350 Cummins.

Also Mack had up on the competition was the 5spd trans 1 to 1 to the rears very little power loss and a long power range, so when the competition is down shifting (losing road speed) the Mack is still plugging along

Here is torque number for 1993 e7

EM7-300 1425 lb.ft at 1020 rpms (Maxidyne) that is almost the same as a Detroit series 60 450hp

E7-350 1277 lb.ft at 1250 rpms(Econodyne)

on the road the 300 felt stronger then the 350 because of torque

Also fly wheel horsepower on the EM7 is 300 at 1750rpm and 310 at 1500rpm

This is why I set my peak horsepower between 1500 and 1600rpm's for torque

With the wheel load dyno the formula is a loss of 60 to 70 hp from the flywheel to the ground

with the engine fan locked on add another 15hp

[mackcl96]

the older maxidynes were measured in brake hp. Brake HP is measured at the flywheel and does not compensate for drivetrain losses.

Trent

Thanks, Trent

all of the spec's I could find was at the flywheel.

Maybe the (AC) chain drive was to the ground I don't know.

[theakerstwo]

Oh I hear you, here is my input

.

Mack Knew that 300hp was bulletproof and gave peek torque numbers. Mack was stubborn in changing what worked for decades.

Also Mack had up on the competition was the 5spd trans 1 to 1 to the rears very little power loss and a long power range, so when the competition is down shifting (losing road speed) the Mack is still plugging along

Here is torque number for 1993 e7

EM7-300 1425 lb.ft at 1020 rpms (Maxidyne) that is almost the same as a Detroit series 60 450hp

E7-350 1277 lb.ft at 1250 rpms(Econodyne)

on the road the 300 felt stronger then the 350 because of torque

Also fly wheel horsepower on the EM7 is 300 at 1750rpm and 310 at 1500rpm

This is why I set my peak horsepower between 1500 and 1600rpm's for torque

With the wheel load dyno the formula is a loss of 60 to 70 hp from the flywheel to the ground

with the engine fan locked on add another 15hp

This is very true and i have know this for since the maxidyne came out but for a cummins driver you cant make him under stand that torque can get you there so horsepower can keep you going so a guy that is running a 13 speed and turning 2100 thinks he is losing time and power by pullingt the engine down to 1200. I have a freind that has two dump trucks and both mack. one is a 237 and the other is a 285 and both will top out at the top of a small hill the same time a 350 cummins will. Yes you can set a cummins up to do better but not at 1200 rpm.