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Old 06-08-2011, 07:47 AM   #15
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Thanks to all who participated in this thread. After your input, several "back and forth" communications with Cummins, and responses from equipment dealers, I conclude that the 1st model year for a combination of CAC inter-cooler and P7100 pump in a motor home was in 1994.

Since Spike45 is volunteering to dig into Cummins Quick Serve Online-- some of our members might want to take him up on his generous offer. Provide him with your 8 character serial#, and, he can provide you with accurate specifications of your engine, injector pump, governor, and, I think, turbo. Such info might be really handy if you encounter trouble some distance away from an authorized Cummins service center, or, if you want to know the most feasible ways to add a few more horsepower to your rig.
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Old 06-08-2011, 07:59 AM   #16
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I belive all mechanical injected (not common rail injected) 8.3s will have the P7100 inline injector pump.
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Old 06-08-2011, 08:17 AM   #17
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My 92 Monaco w 6CTA is equipped with a M&W pump. Apparently more difficult to modify than P7100-- has to be removed from block whereas P7100 does not. Wondering if a P7100 is an easy replacement for the M&W? Also, I am considering separating my water jacketed after-cooler from the engine coolant (already 200 or so degrees) by providing a separate radiator "up front" on the coach, and circulating coolant with an electric pump. Will dropping air temp in the "cooler" by 100 degrees reduce EGT's an equal amount?
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Old 06-10-2011, 10:12 AM   #18
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My 92 Monaco w 6CTA is equipped with a M&W pump. Apparently more difficult to modify than P7100-- has to be removed from block whereas P7100 does not. Wondering if a P7100 is an easy replacement for the M&W? Also, I am considering separating my water jacketed after-cooler from the engine coolant (already 200 or so degrees) by providing a separate radiator "up front" on the coach, and circulating coolant with an electric pump. Will dropping air temp in the "cooler" by 100 degrees reduce EGT's an equal amount?

Beanpole,

What you are describing is what is called 'separate circuit aftercooler' which is commonly used on industrial big bore diesel engines. It works and well but as you have guessed it does provide complication. May I suggest replacing the jacket water aftercooler core assembly with different intake parts so that you can use a Charge Air Cooler radiator like later versions of ISC?

Aftercooling is used primarily as a means to reduce cylinder inlet air temperatures which will have a direct bearing on exhaust gas temps. For every 1 degree of inlet air temp reduction, you cut the exhaust gas temp by 3 degrees F. Plus the added benefit of longer power cylinder component life. I did not mention more power because you do not necessarily get more power from cooler air, just a denser air charge. Since cylinder air charge is greater than the delivered fuel rate, combustion is still limited to fuel rate. So, not more power just longer engine component life.

Turbocharges currently compress the inlet air sufficiently to raise its temperature to around 350F coming out of the compressor wheel housing. A CAC radiator can drop that to about 100 - 150F. Your present JWAC can only get it down to around 200 at best.
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Old 06-10-2011, 02:55 PM   #19
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Thanks Spike, There's a long story behind this engine. Will be as brief as possible. Bottomline, EGT's are running too high-- I drive with both eyes on a dash mounted pyrometer, and keep EGT's to 1,200 or below.

This coach has always been under-powered. Getting out on freeways has always been a problem. Get stuck at 30-35 mph on slight on-ramp upgrade and would have to merge with 70+ mph traffic at 30-35 mph.

Long story short. Alternator failed. Had re-builder re-build it. Within about 200 miles, pulley spun on shaft, serpentine belt jumped track, and, within minutes, engine overheated causing damage to pistons. Had it towed 75 miles to Cummins in Fort Worth. Service tech agreed that it would be a good time to rebuild to a higher horsepower level. He ordered upgraded parts and was ready to put the engine back together, when admins got wind, they nixed the project, and I was told the engine was going back together with parts identical to those taken out. Invoice was over $11,000.

My schedule was super tight, and, Cummins had failed to complete the work in the agreed upon timeframe, however, they wanted me to come and get it "right now!"
My wive can not see to drive. The embarrased Service Tech agreed to meet me "after-hours," and I rented a car to drive the 275 miles to pick-up the coach. We exchanged Keys and my check in the parking lot and the Service Tech left. I returned the rental car and caught a taxi back to Cummins. With not a soul in sight, I fired the engine-- it ran roughly-- the coach vibrated from stem to stern-- when I pulled out onto I-35 it shuddered. I suppose the dyno testing had done a number on the rubber bushing on the rear motor mount (front of engine?) I tied soft braided rope loops on each end of the mount shaft and eliminated most of the shudder. However the engine still vibrated, had less power, and less fuel mileage than before the overhaul. I drove the coach home to be available for a business commitment the next morning. I was ticked-- called Cummins-- they said drive it a couple of thousand miles and bring it back. I understood-- but really ticked-- hate vibration.

I bought a "Diesel Power" mag-- saw lots of stuff re modified injectors. Looked on EBAY and found a set for an 8.3L. Made contact-- met up with a con-man. It was a Biblical experience-- he met a stranger and took him in-- I played the part of the stranger. They fashioned a set of injectors, modified and calibrated my pump, replaced the exhaust, modified the Air Intake (K&N) filter, and, played with the turbo. They transformed our over-the-road coach into a 1/4 mile dragster. Very little more "useable" power," lots of black smoke, and exorbitant EGT's. Have driven it very carefully for almost 4 years-- two long trips. Now looking for ways to lower EGT's.

That's the reason for "separate circuit aftercooler" question. PAC brake is shot-- so thinking maybe new brake and turbo combo-- larger turbo entry orifice and more air. Air intake is 6" necked down to 3.5 or 4' at turbo. Expensive mod, and I have not pursued this option-- may not work at all. Thinking maybe "ram air" from the roof of the coach because K&N filter is exposed to all muck excited by the rear drive wheels, and clogs quickly. What a mess. Have an appointment and have to cut this message "short." Ha Ha, Richard
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Old 06-10-2011, 07:30 PM   #20
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Been messaging with Spike, but anyone can join in discussion.

I have the 6CTA-- after cooled. From looking at the top of my engine, and, the bottom of an after-cooler on Ebay, It appears to me that the "core" sits right over a cavity that houses intake air valves. The product offered on Ebay is listed as an original Inter-cooler, but I think is actually an "after-cooler" and the photo shows the cooling "core" of copper piping.

Seems that the inlet and outlet for the water jacket is less than 1" ID, and that it would be fairly simple to "block" coolant from the engine block, and run copper tubing to a radiator at the front of the coach-- using an electric pump to circulate the "separate" coolant. Seems like circulating through corrugated copper tubing the length of the coach and back that a radiator may not even be needed. Sort of like a ground source heat pump.

Now, if using CAC, a place to mount it would be the biggest challenge. That being accomplished, I suppose would only have to remove the core from the water jacket and plug the inlet and outlet water openings. Sounds so simple.

My "boost" gauge originally moved rather slowly under acceleration, but, now it really jumps quickly under hard acceleration. Need to test drive and look at actual figures. Boost needs to be coordinated somehow? Just thinking. Could have too much boost-- burst CAC unit?
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Old 06-13-2011, 04:11 PM   #21
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Beanpole,

No mystery on the black smoke. The engine is being grossly over fueled. The exhaust gas temp is high due to combustion being in the exhaust port instead of inside the cylinder.

I do not know where to begin on this. You say it is not really any more power than before? I do not think that a separate circuit aftercooler (or do you like intercooler, same thing) or even a charge air cooler (air radiator) will provide low enough air temps to do much. Your root cause in this is excessive fuel rate. You can only burn so much in the cylinder. The high temps are the result of more than necessary fuel that can only burn in the exhaust manifold. While I bet it does accelerate like a rocket it is not much better on cruise for the above reasons. You do not have enough air to match the excessive fueling rate. It is a combination of the injectors and the fuel rack setting. Cut the fuel delivery down to reduce black smoke and EGT should fall with it. With no real usable increase in power and obvious fuel consumption has shot up, what do you have to loose? There are too many of these hotrod diesel shops doing malpractice.
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Old 06-14-2011, 12:05 PM   #22
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Thanks for the info Spike. I was out of town Sat, Sun, and Monday.

I heard "the man" talk about making changes to the Air to Fuel ratio. I think he used a "short" flat blade-- and moved an adjustment screw-- a "quarter turn" at a time. He mentioned turning it back a quarter turn when I took it-- but then remarked something like -- nah! it's gotta have the fuel to make the power. He claimed he took this engine from 250 to 375-400 horse power. I do not believe it. I can't -- say when passing a truck-- floor-board it for long -- maybe 10 seconds before EGT' reach 1,200 -- and I have to back off. On a long grade, pulling an alum trailer and 1989 Jeep Cherokee (around 5,500 lbs.), I'm back to where we were prior to the injector work-- second gear and 10 mph. Try to go faster, and it's a toss-up between EGT's running too hot and the transmission overheating.

Installed two additional trans cooling fans, and if all four fans are pulling air-- prior the the trans getting over 200-- then the trans can now take more power, but, then the EGT's eventually get too high. If the trans ever gets to 230 or so, the fans don't seem to help much. Thinking of adding reservoir for more cooling capacity.

Do you know where to find that adjustment screw on a M&W pump? I also wonder if the excessive black smoke crudded up my exhaust PAC brake?
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Old 06-15-2011, 09:40 AM   #23
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Thanks for the info Spike. I was out of town Sat, Sun, and Monday.

I heard "the man" talk about making changes to the Air to Fuel ratio. I think he used a "short" flat blade-- and moved an adjustment screw-- a "quarter turn" at a time. He mentioned turning it back a quarter turn when I took it-- but then remarked something like -- nah! it's gotta have the fuel to make the power. He claimed he took this engine from 250 to 375-400 horse power. I do not believe it. I can't -- say when passing a truck-- floor-board it for long -- maybe 10 seconds before EGT' reach 1,200 -- and I have to back off. On a long grade, pulling an alum trailer and 1989 Jeep Cherokee (around 5,500 lbs.), I'm back to where we were prior to the injector work-- second gear and 10 mph. Try to go faster, and it's a toss-up between EGT's running too hot and the transmission overheating.

Installed two additional trans cooling fans, and if all four fans are pulling air-- prior the the trans getting over 200-- then the trans can now take more power, but, then the EGT's eventually get too high. If the trans ever gets to 230 or so, the fans don't seem to help much. Thinking of adding reservoir for more cooling capacity.

Do you know where to find that adjustment screw on a M&W pump? I also wonder if the excessive black smoke crudded up my exhaust PAC brake?

I believe the "M&W" you refer to is the Bosch model MW pump. With all that you describe and no real advantage other than toasting the turbo on hard acceleration, why do you not consider taking to a reputable repair facility and return it to stock condition. The fellow with the screw driver sounds like a hack to me. Increasing HP requires much more than just turn the screw to allow for increased rack travel (more fuel). Engines now have matched turbos and injectors. Some have different pistons. Just turning the screw to increase fuel delivery without sufficient matching air volume to burn the fuel only results in the 'afterburner effect'.....combustion completing in the exhaust manifold. I, too, seriously doubt you had that much increase in HP.

BTW, the device he may have been speaking of is what we used to call at Caterpillar the FARC, Fuel-Air Ration Control. The task for that device is to hold the rack back until the turbo can spool up to speed and produce more air to match the increasing fuel delivery as you step down on the throttle. With the FARC correctly set, it allows enough rack travel to accelerate the engine without over-fueling as the turbo is lagging behind in air delivery. As the turbo increases If you do not know, the 'rack' is a linear gear that moves to turn the individual injector pump plungers connected to the rack with a small sector gear. Turning the plunger changes the length of the helix. The plunger has to cover the 'fill' port to force fuel past the nozzle check valve. The end of injection is when the 'spill' port is uncovered to vent the fuel under pressure to vent back into the fuel rail or manifold.

Here is a pretty good site with illustrations on how scroll and helix injection pumps work: http://http://www.exploroz.com/Vehicle/Technical/DFI_Systems.aspx

Scroll the page down to the 'inline pumps'.
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Old 06-16-2011, 08:06 AM   #24
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Hello I have a 1996 Monaco with a 8.3 it's says it is a 300 hp & I'm sure it is as it runs like a freight train so I think someone has been doing something to it as the boost goes up to 23 and if I remember these are suppose to run at around 15. It runs great. The reason I'm writing is my pacbrake is toast. When I got it it was missing the actuator and the butter flap was siezed so does anyone out there know where I can get a replacement for it at a reasonable price. Thank you Ric. bounder39@aol.com
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Old 06-16-2011, 01:21 PM   #25
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Thanks Spike for the very thoughtful response. If I can find the "screw," I think turning it "clockwise" should reduce fuel rate. A local shop for which I have respect, will not touch my coach because of the mods. I asked another shop to "turn" the screw to cut back on fuel, and, they too refused to touch it. So-- it's up to me to find the screw. I see the pump-- but no screw-- maybe a mirror will help. Again thanks for all the good info. Best wishes to you.

Wish I could help Bounder-- just do not know the answer to his question.
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Old 06-16-2011, 04:18 PM   #26
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Thanks Spike for the very thoughtful response. If I can find the "screw," I think turning it "clockwise" should reduce fuel rate. A local shop for which I have respect, will not touch my coach because of the mods. I asked another shop to "turn" the screw to cut back on fuel, and, they too refused to touch it. So-- it's up to me to find the screw. I see the pump-- but no screw-- maybe a mirror will help. Again thanks for all the good info. Best wishes to you.

Wish I could help Bounder-- just do not know the answer to his question.
The Air Fuel Control adjustments that I know of but not sure about on the Bosch MW pump would adjust the 'hold back' on the rack travel. The diaphragm receives boost air pressure signal from the intake manifold. As the boost comes up as the turbocharger spins up it moves a little more to allow the rack to move more even though you hold your food down. AFC adjustment is a MAJOR part of your issue. If the turbo is toast, then you essentially have a naturally aspirated engine. NA engines characteristically have high exhaust temperatures usually in the range of 1500F at full load. Correctly turbocharged engines have a normal exhaust temperature of 950F at full load. It may be your turbo is unable to supply sufficient air due to issues with the turbine or the compressor sections.

BOTTOM LINE: Take it to a Cummins distributor. Get it back like it was. You are not going to be able to make a 6CTA run like an ISL 450. But you can get it back to operating respectable and resume the long life this engine is capable of.

Picture below is the line drawing from the 6CTA service manual showing the location of the AFC. A Cummins distributor service department can adjust it correctly. See the attachments I have included about this subject.

GOOOOOOOOOOOOOOOD Luck.

Gary
Attached Thumbnails
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Name:	Bosch MW AFC location.PNG
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Size:	345.4 KB
ID:	11253  
Attached Files
File Type: pdf AFC info from 6CTA Service Manual.pdf (100.4 KB, 157 views)
File Type: pdf Unauthorized Adjustment of Midrange Fuel Injection Pumps.pdf (82.8 KB, 106 views)
File Type: pdf Excessive Fuel Consumption Troubleshooting.pdf (306.7 KB, 89 views)
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Old 07-18-2011, 08:51 PM   #27
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Hi, been watching this thread and wanted to know some of the info that is passed in this thread involving the 8.3, what I have is a 1989 Monaco Crown Royal with the 6cta8.3 but I noticed that the turbo on most 8.3 are on the upper drivers side of motor but mine is located on the bottom lower drivers side, by the oil pan area, any go or bad about this ? Thanks Jr.
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Old 07-19-2011, 03:10 PM   #28
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Hi, been watching this thread and wanted to know some of the info that is passed in this thread involving the 8.3, what I have is a 1989 Monaco Crown Royal with the 6cta8.3 but I noticed that the turbo on most 8.3 are on the upper drivers side of motor but mine is located on the bottom lower drivers side, by the oil pan area, any go or bad about this ? Thanks Jr.
Jr,

Yours being a much older iteration of the venerable C8.3 is why the turbo was mounted differently. Does not make any difference in performance. That engine family has always had the exhaust manifold on the left facing the front of the engine (fan end, not flywheel end). For you, the fan end is facing out toward the back thus the exhaust is on your left (driver side).
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