Detroit Diesel 71 - 92 series fans

this is last nite,I94 on the way to sysco baraboo wis. 43K in the box,according to bol. nice nite to cruise windows down,cab and bunk vents open. you can hear me lean on it after panning the gauges,then go into big hole overdrive. ain't that a purty song?



this motor actually pulls hard at 1500 rpm. looking at DD's own literature on these,the 350hp silver 92 max torque rating was at 1000rpm. my 445 is at 1300 rpm. i think the old,now permanently etched "slam yer hand in the door and drive it like you feel" tale has left a stigma on the 2 stroke in peoples minds. guys were told to rev em out or blow em up. i was too. i started watching the egt,and paying attention to the motor and how it was pulling. i didn't agree with the old 2 stroke methodology and some research proved i was right. i'm 42. cut my teeth on a 12.7l series 60, i didn't spend 20 years at the helm of the 318's and 238's. those i imagine you did need to wring out real proper to move. the later 92's.....don't. at first, i looked at it as a novelty engine. now i like,and respect it very much.

going into bigger hills,it does one of two things dependant on the hill,and weight. it either spools up and pulls the hill,or starts pulling the rpms down. at that point,it seems like it wants to sit at 1500 rpm. i can leave it in top gear,and pull 1500 as long as it can,or start dropping and splitting gears,and it still wants to drop to 1500. i do a lot of the same runs,similar loads,so i can experiment with how it pulls. it definitely has a sweet spot at 1500.

the EGT's will not go higher than 750. that turbo just blows too much air thru the block. the motor can pull down,as long as it is pulling.

my dad built the truck to be novelty show truck to run around town with,and economy was not in mind. showing off was,lol. the 4.56 gears,and big injectors and 2400 rpm limit for example. it does sound great in rush hour creeping with traffic at 2000 rpm,lol.

i don't drive it like i'm mad at it. i try to drive it correctly. according to dee-troit that is.

i was heavy out and back today. loaded in richland center wis. ran up 14/27. very hilly. was 78XXX lbs coming back. 5.2 for the round,i was leaning a bit harder on it in the hills,about 8-10 lbs boost. not bad really,considering.if i can do 5.5 overall,and not have to CRAWL up the hills-(aint expecting to blast up them foot on floor either)-we'll probably keep the detroit in it.

the best anyone else has done was 4.5 at the most....as bad as 3.75,driving it like you slammed yer hand in the door.....

 

The 8V92TTA will definitely pull down lower than the 8V71T. Around 1750 you could feel the bottom fall out of the 71T series. If you were on a big hill where the rpms were dropping fast you had better grab the next gear around 1900. My old 318 would turn 2550. It had 4" pipes with gutted mufflers. It was very loud, but it sure sounded great from 2150 on up, and the power kicked in at that rpm also.

I guess that's why I have tinnitis now. The old NH 250 Cummins and 71 series Detroits I used to drive were very loud.

But I tell you, heading east on I-40 just inside NC, climbing up through the twin tunnels with a decent load, that 318 was the best sounding truck I have ever heard. It would echo off the mountains. Not fast by any means, but sure sounded great. The only sound I can compare it to is a 1693 Cat at idle or just taking off going through the gears. Pure music to your ears.

Nothing sounds like that today, not even close. If I pulled into a truck stop and heard the clatter of a 1693 close to me, I would roll down the window just to listen to it.

 

Yeah, the "thunka, thunka, thunka" of a worn out accessory drive you're most likely to hear in a truckstop nowadays just doesn't have the same aural appeal, does it?

 

The 2 cycle Detroit's, most every one has it's max torque at 1200 RPM just like every other motor of the day, and just like every other motor of the day the Max torque and the HP graph cross at 1550, That is the operating range, above that you just burn excessive fuel., and extra heat, that does not mean you can not rev it up coming to a hill, even then 1800 should be the top.
Anytime someone tells you a Detroit has no torque, put it in low gear and with the maxi's on hit the start button, it will drive away try that on anything else. If you look at the option tag, the rating is heavey heavey, no other truck engine has that rating, they are oil cooled and if treated right they will last a long time, look at all the old cement trucks still running around. Go to a marina and look at the motors in bigger boats.
Just a thought!

 

Hahahaha. That's too funny. I remember someone telling me as I was running a 1693 back in the day ...... " If it gets real quiet, I'd start to worry ..... "

 

I never had the chance to run a 1693, but I can remember the 362 Pete cabovers w/ 1693s that were a couple inches higher than the rest. There was more cab below the step, and if you knew what to watch for, you knew which ones were likely able to blow your doors off.

 

Fast 1693 Peterbilt, real fast....

 

off to Aldi oak Creek. see you on I94.

 

Like i said before i use to overhaul the 2 stroke dd in military. Seen several of them go 100k or more in hmmtt's and het's with
soldiers driving them. Alot of hard usage and abuse. Still love the sound of them with straight pipes. Use to love putting them on the engine dyno and ground hopping them to do initial break in before putting them in engine cans. Straight out of the turbo oh what a sweet symphony!!. Also liked taking the m113's out and running the snot out of the 6v53's they have mufflers but not much of one. Exhaust about 3 ft from your right ear screaming at 2900 rpm. Very loud even with ear plugs.#### i miss them.

 

We had a instructor at NADC that loved to start up the 8v71 on the test stand, pull the throttle wide open with a bungee cord and twist the jake's idle switch wires together . She would run wide open and jakes working at the same time. Engine and stand would walk across the room!