Empathy List Archives

G

GYMKIDD319@aol.com

Sat, Mar 20, 2004 12:59 PM

Rafael posted:
"...My impression is that engines designed for turbos aren't designed to run
without them-- and vice versa. The key issues are compression..."

In an offline exchange regarding the original post on removing turbos, it was
confirmed that the engine in question IS a DD 8V71T....

These have compression of 17 to 1 according to my DD manual....and weight
3250 lbs with transmission....they weigh in at 3100lbs for the natural
engine....I can't find the compression of the natural....

I provided the originator with an offline source who has first hand knowledge
of the changes for this engine model....
But Rafael and Arild have a good point....don't make this change without
KNOWING what is required....

FINANCIAL ANALYSIS
If the turbo removal and other modifications do result in a HP change from
435 to to 350 natural, 350/435 is about 80% which means fuel economy should
improve about 20%...maybe alittle more if you can run at a lower RPM....

Let's assume the modification (done professionally) costs $1,500/engine or
$3,000 total for two. ( I have no idea what it costs, don't use this number.)

Let's say you estimate using 2,500 gallons annually at $1.50 without the
conversion. A 20% savings would be 2500 x 1.50 x .2 or $750 savings
annually....it would take 3,000/750 or about 4 years to recoup your costs of conversion....
....plus you won't have any turbo repairs....and maybe you can sell them (two
per engine l) on e-bay!!! The intercoolers alone (also two per engine) list
for $1,000 each (actual figure, from five years ago)....

I'm not making a judgement here ....just providing one simple way to see
what the payoff looks like...Please note these are illustrative figures only,
plug in your own based on fact...

Cheers,
Rob Brueckner
1972 Hatteras Yachtfish

Rafael posted: "...My impression is that engines designed for turbos aren't designed to run without them-- and vice versa. The key issues are compression..." In an offline exchange regarding the original post on removing turbos, it was confirmed that the engine in question IS a DD 8V71T.... These have compression of 17 to 1 according to my DD manual....and weight 3250 lbs with transmission....they weigh in at 3100lbs for the natural engine....I can't find the compression of the natural.... I provided the originator with an offline source who has first hand knowledge of the changes for this engine model.... But Rafael and Arild have a good point....don't make this change without KNOWING what is required.... FINANCIAL ANALYSIS If the turbo removal and other modifications do result in a HP change from 435 to to 350 natural, 350/435 is about 80% which means fuel economy should improve about 20%...maybe alittle more if you can run at a lower RPM.... Let's assume the modification (done professionally) costs $1,500/engine or $3,000 total for two. ( I have no idea what it costs, don't use this number.) Let's say you estimate using 2,500 gallons annually at $1.50 without the conversion. A 20% savings would be 2500 x 1.50 x .2 or $750 savings annually....it would take 3,000/750 or about 4 years to recoup your costs of conversion.... ....plus you won't have any turbo repairs....and maybe you can sell them (two per engine l) on e-bay!!! The intercoolers alone (also two per engine) list for $1,000 each (actual figure, from five years ago).... I'm not making a judgement here ....just providing one simple way to see what the payoff looks like...Please note these are illustrative figures only, plug in your own based on fact... Cheers, Rob Brueckner 1972 Hatteras Yachtfish

JH

James H. E. Maugham

Sat, Mar 20, 2004 2:07 PM

Rob Brueckner wrote:

FINANCIAL ANALYSIS
If the turbo removal and other modifications do result in a HP
change from
435 to to 350 natural, 350/435 is about 80% which means fuel
economy should
improve about 20%...maybe alittle more if you can run at a lower
RPM....

RPM to RPM without any other modifications to the engine other than removing
the turbo, the engine will burn the exact SAME amount of fuel.

The turbos exist on engines to get more HP out of them with the same fuel
burn as a NA engine of the same size. Internal combustion engines burn AIR
and the more you can pack into the cylinder means the more power you can get
out. The diesel oil or gasoline "fuel" is simply an ignitor.

Mechanical fuel pumps for diesels do more than their gasoline brethren which
only need to maintain a constant pressure and volume. Diesel pumps meter a
specific amount of fuel to the injector and, absent changing the pump and
injectors, the amount of fuel a de-turboed engine would burn at a specific
RPM would remain constant.

Result, turning the wick up to 1800RPM on these de-rated engines would
result in burning the same amount of fuel. You'd just go a lot slower.

Regards,

James

Rob Brueckner wrote: > > FINANCIAL ANALYSIS > If the turbo removal and other modifications do result in a HP > change from > 435 to to 350 natural, 350/435 is about 80% which means fuel > economy should > improve about 20%...maybe alittle more if you can run at a lower > RPM.... RPM to RPM without any other modifications to the engine other than removing the turbo, the engine will burn the exact SAME amount of fuel. The turbos exist on engines to get more HP out of them with the same fuel burn as a NA engine of the same size. Internal combustion engines burn AIR and the more you can pack into the cylinder means the more power you can get out. The diesel oil or gasoline "fuel" is simply an ignitor. Mechanical fuel pumps for diesels do more than their gasoline brethren which only need to maintain a constant pressure and volume. Diesel pumps meter a specific amount of fuel to the injector and, absent changing the pump and injectors, the amount of fuel a de-turboed engine would burn at a specific RPM would remain constant. Result, turning the wick up to 1800RPM on these de-rated engines would result in burning the same amount of fuel. You'd just go a lot slower. Regards, James

KP

Keith Pleas

Sat, Mar 20, 2004 3:54 PM

Re: Removing turbo

Another thing that I recall from a previous thread on this topic was dealing
with the lubrication for the turbo.

Keith

Re: Removing turbo Another thing that I recall from a previous thread on this topic was dealing with the lubrication for the turbo. Keith

D

David

Sun, Mar 21, 2004 2:32 AM

If you take the turbo off and put in a spacer, and you want it to be
permanent you should change the injectors. I think on the 435 HP 8v71s this
requires some exhaust work as well as they have only one turbo. On twin
turbo models like the 12v71 its very easy to put in a spacer. You can look
up what the 8v71 naturals used for injectors and replace them, re-set the
rack, and your off and running. Its harder to go the other way and add
turbos to non-turbos, cause they have different pistons and heads. These
higher performance heads will be happy with less power.

With all motors its the same thing air and fuel. More fuel with bigger
injectors, then you need more air so they put on turbos. But its always an
engineering exercise to balance it out. Too much fuel you get carbon
deposits. Too much air and it runs too lean and won't get up to RPMs.

I had a friend with 12v71ti 550 hp DDs. He crossed from Brownsville TX to
New Orleans running at 1200 rpm, hull speed. When he got close to New
Orleans he powered up and found out he had burned out his twin turbos on
both engines. When he got to the marina he was not happy. Turns out he had
to pay $700 each to get 4 re-built turbos. He did mention that he saved
$4000 in fuel by going slow across the gulf instead of 20 knots from port to
port. Then he paid another $300 for a pair of inserts for the next time.

Do really fast motor yachts and sportfish go slow. Sure when it suits them.
I understand the new computerized super diesels can adjust injectors and
turbos so that they can run slow for ever if you so choose. Kind-a makes one
think when buying a trawler, or motor yacht or Sportfish its so confusing. I
like to go slow and save money but I like to go fast cause I can get to St
Michaels and back in a weekend. Oh my?

Skooch
Worton Creek MD

If you take the turbo off and put in a spacer, and you want it to be permanent you should change the injectors. I think on the 435 HP 8v71s this requires some exhaust work as well as they have only one turbo. On twin turbo models like the 12v71 its very easy to put in a spacer. You can look up what the 8v71 naturals used for injectors and replace them, re-set the rack, and your off and running. Its harder to go the other way and add turbos to non-turbos, cause they have different pistons and heads. These higher performance heads will be happy with less power. With all motors its the same thing air and fuel. More fuel with bigger injectors, then you need more air so they put on turbos. But its always an engineering exercise to balance it out. Too much fuel you get carbon deposits. Too much air and it runs too lean and won't get up to RPMs. I had a friend with 12v71ti 550 hp DDs. He crossed from Brownsville TX to New Orleans running at 1200 rpm, hull speed. When he got close to New Orleans he powered up and found out he had burned out his twin turbos on both engines. When he got to the marina he was not happy. Turns out he had to pay $700 each to get 4 re-built turbos. He did mention that he saved $4000 in fuel by going slow across the gulf instead of 20 knots from port to port. Then he paid another $300 for a pair of inserts for the next time. Do really fast motor yachts and sportfish go slow. Sure when it suits them. I understand the new computerized super diesels can adjust injectors and turbos so that they can run slow for ever if you so choose. Kind-a makes one think when buying a trawler, or motor yacht or Sportfish its so confusing. I like to go slow and save money but I like to go fast cause I can get to St Michaels and back in a weekend. Oh my? Skooch Worton Creek MD

trawlers@lists.trawlering.com

TWL: Going slowww for fuel savings