DD8V71 compaired to DD8V71T

[gm4106]

Waht is the difference in the horse power and the torque between a 8V71 turbo and a 8V71?
What parts of the motor are different between these two motors, heads,vales, block or pistones?
This would be the earlier model of the DD8v71T.
Any other related information would be helpful also.

[Jerry32]

It seems to be that when engines are discussed there is no mention of horsepower or torque and I have tried to find something on the web but to no avail. Where are all the engine experts that can inform about these DD engines.

[Melbo]

Just be patient

When Tom C reads this he will be able to answer the question

Also if you locate his thread about the turbo in his bus it may answer most of your questions.

Melbo

[RTS/Daytona]

detroit diesel HP guide -->
http://www.adieselengine.com/new_page_1.htm

[TomC]

Well now that you mention this- I just changed my 8V-71N to a 8V-71TI.  The original engine was a standard 8V-71N for transit that has 18.7 to one two piece pistons (iron top with aluminum skirt).  First off Don Fairchild, who did the work, pulled one head and one piston to make sure I had the proper rings.  Luckily, transits use a tighter oil ring set for cleaner burn compared to the over the road trucks that are looser, burn more oil but last longer.  I had an air to air intercooler made for in front of the radiator, changed the blower from a small bearing to a large bearing with bypass valve, increased the injectors from N65 (300hp and 800 lb/ft torque) to 9G75 (370hp and 1125lb/ft torque) because I kept the higher compression pistons, keep the turbo boost to 15psi.  If I had changed the pistons from the 18.7 to 17:1, I could have gone to a full 25psi boost with 80 injectors for 400hp with 1200lb/ft torque.
So to change from a natural to turbo, you could do as little as just add the turbo for about 6-10psi boost-mainly for high altitude smoke control (that's what I started out as, but got a little carried away).  You could do what I did for a medium bump in power-add turbo, air to air intercooler, go from 65 to 75 injectors (blower change was optional).  Or all the way- change pistons and liners, injectors from 65 to 80, change blower to bypass, add air to air intercooler or buy block with aftercooler built in. Injectors with horsepower and torque is- first for non turbo (8V-71):
N55- 260hp and 680lb/ft
N60- 280hp and 740lb/ft
N65- 304hp and 800lb/ft
N70- 320hp (or 318hp if you prefer) and 860lb/ft
Horsepower and torque for turbo and aftercooled 8V-71:
7G65- 325hp and 975lb/ft
7G70- 350hp and 1050lb/ft
7G75- 375hp and 1125lb/ft
7G80- 400hp and 1200lb/ft- which was the highest setting Detroit offered from the factory.
The horsepower and torque is higher with the turbo, even with the same size injector because of more air and better efficiency.  Non turbo engines will loose power the higher up in altitude you go, whereas turbo engines will maintain power to 10,000ft before loosing some power.
Just to let you know the difference in performance.  Coming south from Las Vegas to L.A. on I-15.  Just into Calif, the big pull up the first hill, I used to do 30mph, now do 40mph.  Also, where before had to down shift several times on some of the other hills on the way to L.A., once I topped the big hill, didn't have to down shift once ever all the way back to L.A.  The turbo really wakes up the 8V-71!  Highly recommend it over exchanging for another engine
I also had to enlarge the radiator core and air cleaner.  Good Luck, TomC

[gm4106]

Thanks Tom this is very helpful. I'm looking at a 4106 with a turbo 8v71 with a V730  So to tell for sure what it is don't know.  The owner don't know. The person before him changed it and no info came with the bus. But I would guess this is something stamped on the block . Where would I look ? Once again thanks.

[Melbo]

there is a serial number on the block

If you are sitting on the transmission it is on your right hand side

On my MCI it is on the drivers side

Low on the block and hard to see behind the air cleaner etc.

Melbo

[TomC]

One of the best ways to find out what the engine puts out is to pull the lower valve cover (it only has the two bolts in the middle holding it on)and look at the round tag on the injectors.  It'll say like- N65, or 7G75 or similar.  Make sure when you put the valve cover on that you center it accurately so not to hit the injection control rack inside.  That can limit your full throttle if it does hit.  Good Luck, TomC