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Discussion Starter #1
I am a complete noob to this site, and to diesels in general. i'm gonna put a 4bt in an early bronco soon, just because i think that would be cool. past/current projects have all been 302's or 351's.

the bronco will be built up w/a 3.5" lift, 2" body lift and i'm becoming convinced that the nv4500 should be behind it. still undecided though, as it will see some rock crawling and i think an auto would be easier to deal with there. a couple of questions for you folks.

i'd like to know some practical ways to make a little more power out of it, but keeping some bottom end for running thru the rocks? possilby adding an aftercooler or something, but i know nothing about modifying a diesel yet. a lot of the threads contain a good deal of bs (just my opinion) from people that sound like they are living in la la land. can anyone out there give some good sound advice? flame me as need be.
 

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I'm in the process of a early Bronco conversion and wanted specific torque and horsepower numbers out of a 4bt CPL858. I posted the results of a dyno session involving 33 pulls in "Performance Discussion" under the "Dyno Results" thread.

I find this site to be very useful and after you do the research required to perform the conversion your BS filter may clear up a bit.
 

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I'm in the process of a early Bronco conversion and wanted specific torque and horsepower numbers out of a 4bt CPL858. I posted the results of a dyno session involving 33 pulls in "Performance Discussion" under the "Dyno Results" thread.

I find this site to be very useful and after you do the research required to perform the conversion your BS filter may clear up a bit.
Well said!

Diesels and gassers are different as night and day. The horsepower & torque figures don't tell much in direct comparison. A typical gas engine starts making power around 1,500-1,700 rpm and doesn't get anywhere near full power until 4,500-6,000 depending on the engine build. At about 5,200 rpm torque and power merge to the same quantity on a gas engine.

A typical diesel engine makes torque right off of idle, from 1,000 rpm and keeps making more torque until maximum rpm, often at about 2500-3,000 rpm. Horsepower isn't optimized until the higher rpm range. Because of this a diesel makes great bottom end torque at low speed, ideal for rock crawling. The added torque throughout rpm range also gives good power at higher speeds.

A little diesel self-education can go a long ways towards helping you translate what you think you want into what you actually need. You won't find a better website to start getting educated on the subject, in my opinion.
 

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Discussion Starter #5
i did look at that thread. it started off good, but has turned into a debate on ideals. it was really my reason for wanting to start this thread. i'm just looking for some real world suggestions. i did find brut's dyno stuff (finally) and it was very informative.

i think in stock form the 4bt will do well for me. i'd like to mod it a little bit just because that is how i am. i'm sure it will start off stock, as found in the bread truck, so i can start from a clean slate. i've been doing some research, but any suggestions by people w/similar goals that have done some things to their motors would be helpful.
 

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i think in stock form the 4bt will do well for me. i'd like to mod it a little bit just because that is how i am.

Me too. I already have an air-to-air intercooler from a previous car.
And turning screws on the IP is fee, too!

I also have a H1C from a 5.9 - I guess I'll try it since I have it.
 

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I spent a considerable amount of time on "performance research" only to continually assess the gains vs durability and want vs need. My compromise was to rebuild the engine after the dyno runs with the following:

Complete balance
Stock cam
Stock crank and rods
New bearings
All new seals and gaskets
New head
New head bolts
Piers Diesel performance valve springs
Arias 1700* pistons
Arias Hellfire ring sets
VE pump rebuild kit with 3200 rpm spring
Turbo rebuild kit (stock turbo)
New stock injectors
New water and oil pumps
Plus some minor bearing changes (belt tension roller, idler roller)

I am adding a Bendix compressor / Vickers V10 PS pump assembly and a 300 amp alternator.

An intercooler won't offer much in lower EGTs because I won't be towing with the Bronco and it will typically see the need for lower EGTs at a very slow speed.

I'm still undecided about some form of custom intake....and this is always the delemma. The best a custom intake could do for the motor is maybe 15 hp, so do I want the intake for looks or should I just tune the IP and timing for the additional HP.;)
 

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I don't think you would need to build for so much power if you plan to keep stock injectors. Of course, maybe you are building for more power in the future.
 

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I spent a considerable amount of time on "performance research" only to continually assess the gains vs durability and want vs need. My compromise was to rebuild the engine after the dyno runs with the following:

Complete balance
Stock cam
Stock crank and rods
New bearings
All new seals and gaskets
New head
New head bolts
Piers Diesel performance valve springs
Arias 1700* pistons
Arias Hellfire ring sets
VE pump rebuild kit with 3200 rpm spring
Turbo rebuild kit (stock turbo)
New stock injectors
New water and oil pumps
Plus some minor bearing changes (belt tension roller, idler roller)

I am adding a Bendix compressor / Vickers V10 PS pump assembly and a 300 amp alternator.

An intercooler won't offer much in lower EGTs because I won't be towing with the Bronco and it will typically see the need for lower EGTs at a very slow speed.

I'm still undecided about some form of custom intake....and this is always the delemma. The best a custom intake could do for the motor is maybe 15 hp, so do I want the intake for looks or should I just tune the IP and timing for the additional HP.;)
I am very interested to know the results after balancing. Please keep us posted and report how close everything is!

On a couple of 6BT that I saw balanced there was very little that was not balanced already...

If I were to spend money on a full rebuild I would not be afraid to rebuild with Cummins stock parts, opposed to the HP pistons. I am curious how much more they cost than OEM? I would rather spend the extra to have someone in-the-know port the heck out of the head and have the QuickSpool port Mod done to a Turbine housing.
 

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I would rather spend the extra to have someone in-the-know port the heck out of the head and have the QuickSpool port Mod done to a Turbine housing.
Do you think head porting is going to acheive anything on an engine that almost never sees 3000rpm?

What is this "quickspool" turbine housing mod?
 

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Do you think head porting is going to achieve anything on an engine that almost never sees 3000rpm?
Ohhhhh....YES! Don't think in terms of RPM's...think lbs or Kg of airflow moving through. If you could move 60 lbs per minute of air through the engine (with enough fuel, too) at 3000 RPM you can move houses!

What is this "quickspool" turbine housing mod?
Probably just smoothing the transition from flange to scroll
 

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Ohhhhh....YES! Don't think in terms of RPM's...think lbs or Kg of airflow moving through. If you could move 60 lbs per minute of air through the engine (with enough fuel, too) at 3000 RPM you can move houses!
Ports don't care about mass flow. They only care about velocity (pressure losses proportional to velocity squared).
4BT's flowing 60lb/min of air has been done, but it's done by increasing the boost which increases the density, the air velocity is the same as a naturally aspirated 4B turning at the same RPM.
 

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Discussion Starter #13
how does not increasing boost not affect velocity? i'm a little lost on that one. i know that my air hose will seemingly blow with more velocity at 120 psi than at 30 psi.

another thing i'm curious about is how much these things smoke when the the fuel is turned up a turn or 2. i'm not looking to have it smoke like a freight train. it'd be ok on hard acceleration, but not all the time. anyone have some insight on that? the motor i'm picking up is a 4bt with about 60k miles on it. i doubt that i will go so far as to port it. maybe add some valve springs, but i don't think i'm gonna tear it apart this early in the game.
 

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how does not increasing boost not affect velocity? i'm a little lost on that one. i know that my air hose will seemingly blow with more velocity at 120 psi than at 30 psi.
...
Nozzles are designed/used to convert pressure to velocity.

Although your air hose probably does not have a well designed nozzle, what is happening at the end is similar - the pressure of the air exiting the end of the hose is converted to velocity. With increased pressure, the nozzle at the end of the hose can achieve higher velocity.

I remember, when I was much younger and involved with motorcycle racing, someone I respected at the time for his technical knowledge of engines, explained that velocity in an inlet port was related to the piston velocity.

Actually I have turned his explanation around. This concerned the practical limit to engine rpm and why multi cylinder short stroke engines rev faster - the rpm and stroke determine piston speed, piston speed determines flow velocity in the inlet port, and the limit to the engine rpm is the air velocity in the intake port.
 

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Do you think head porting is going to acheive anything on an engine that almost never sees 3000rpm?

What is this "quickspool" turbine housing mod?
Your the engineer, you tell me! I see the high temp, high dollar pistons on the list and the first thing that comes to mind is he's concerned about EGT. I think the OEM pistons are good enough, my opinion of course. Have you ever looked in the frontal area of the intake on a 12 valve 6BT cylinder head? The huge wave of material in there? Is the 4BT head the same? I was thinking moving the air better couldn't hurt a thing. Am I wrong in thinking a better flowing head would have lower EGT?

The quick spool modification is a port job of a turbine housing, it makes a 16 spool like a 14, or a 14 like a 12 etc. Reasonable mod to have done.
 

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how does not increasing boost not affect velocity? i'm a little lost on that one. i know that my air hose will seemingly blow with more velocity at 120 psi than at 30 psi.
When you compress a gas, you're shoving the molecules closer together. If you increase density, you increase the total amount of material moved in a given timeframe without having to increase velocity.

About like a freeway.. If you only have cars in 2 lanes on a 4 lane freeway, all following at 100 yards, then you compare it to 4 lanes being used with a 50 yard following, you've quadrupled the volume of cars you move at the same velocity.

Now, there's a LOT more interplay between velocity, volume, and pressure, but Bernoulli needs his rest..
 

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Do you think head porting is going to acheive anything on an engine that almost never sees 3000rpm?
Hell ya! for a normal street driver, No....But if you are pushing some good boost number and have already done the normal tweeks here and there and dont mind speeding some cash looking for all you can grab then there is power to be found in dem dar runners;)
 

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I know that my air hose will seemingly blow with more velocity at 120 psi than at 30 psi.
Don't forget that your blowgun is exiting at atmospheric pressure. We have a turbo on the exhaust side, so imagine if you will your air blow gun blowing into the small opening of an oil drum with 60psi of air already inside. When you increase boost pressure, you also increase exhaust back pressure through the turbine.

But, it all works out in the end, since the real goal is to get as many pounds of air THROUGH the engine as are needed to make the work you need. Porting will help with flow. An engine with good ports will be flowing more air at 20 psi than and engine with restrictive ports at 20 psi.
 

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Discussion Starter #19
thanks for some more insight. i can see how a turbo would make the air more dense, as it compresses it. i don't see how a NA engine would have the same flow rates as a turbo'ed engine though. it just seems like there is more 'force' there to push more air through the ports. i know in a NA engine, vacuum goes to 0 under full load. i didn't care much for bernoulli, pascal, or whoever invented calculus (trying hard to block out all that stuff now)... pythagoras and i get along pretty well though. plus, he had a cool sounding name..

here are my thoughts so far. i'm thinking of doing a turbo swap, possibly a HY-35 or HX-35, but i've heard some have had problems w/egt using these. any other thoughts on doing some mods within the 2-300 range? i think the turbo would probably give the most bang for the buck.

what i definitely plan to is the governor spring mod and turn up the fuel a bit. not sure what else might be needed. i'll check the pump timing, but probably won't clock it any, or if so, it will be just a hair. i won't be pulling anything, and will do regular street driving and rock crawling on some weekends. it won't be a daily driver.
 

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i don't see how a NA engine would have the same flow rates as a turbo'ed engine though.
He was saying velocity (speed) stays the same, regardless of pressure. Imagine pushing a gallon of water through at 20 psi versus a gallon of corn syrup at 20 psi, but at the same speed.

i'm thinking of doing a turbo swap, possibly a HY-35 or HX-35, but i've heard some have had problems w/egt using these.
Look for a HY35, I was reading some thread where a guy was getting bad compressor surge with the HX35. There are others: My 1993 6BT is going to donate its H1C to the 4BT.
 
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