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Old 04-09-2012, 11:47 PM   #1
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My Project MPG on 95 8.3 cummins Holiday Rambler

I have quite a few ideas and want to see what some of you think.

I just bought new to me a 1995 Holiday Rambler 39wd. No slides on a Spartan Mountain Master chasse. With a 8.3 mech injected Cummins mated to a MD3060 Allison transmission.

Current weight with 1/2 fuel, full propane, 1/4 tanks, and loaded with camping gear looks to be around 28k.

While the camping aspect is awesome with our new purchase the real reason is for our Race Team and traveling across the country to different drag race events. We will be towing a 32ft trailer with 2 race cars. Trailer and cars will be around 11k so our combined will be around 39k.

So far I have filled her up twice with MPG testing. With trailer empty to Seattle and towing 1 car back she got around 8.2mph avg around 60-65mph. Next tank was some trailer but lots of small trips from my shop, camping and random idling. The MPG came out around 7.2.

While I really want to turn up the HP via fueling I feel this could worsen MPG so I am going to try things 1st that I know should only help MPG and may or may not add HP.

1st thing on my list is the air intake. When I 1st got her the filter minder was sucked deep into the yellow. So I ordered up a new air filter while I was doing my fuel and oil filters. For air filters I felt it was quite huge and rated at 1000cfm. Well to my suprise even the new filter caused the filter minder to suck into the yellow. This now has me questioning the engineering on the air inlet on the side of the coach. Seems to me with no scoop that the air rushing by could create a suction. Making it harder for the motor to suck air. In looking at a few newer coaches today I see some of them have the inlet hole on the back corrner of the RV. So my plan to make some kinda of a scoop.




2nd on my list will be to advance the inj pump timing to around 15deg. Should be some free hp and MPG.

3rd is pull the wg line on the turbo while I know without more fueling the boost may not go up but even if it is a few more PSI it could make a little more hp on the same fuel. This does the same job as the Banks big WG with out spending the $$

4th been reading on here about how much hp the hyd fan draw. So 1st mission will be to make sure my fan is working right. Next idea I was thinking was doing a safe tow mud flap forward of the radiator and motor. I have a side radiator. I may even do one up front. I feel like the more air I can get out of the bottom of the RV the more air that can make it through the radiator. Was also thinking of some kind of side scoop to try and get more air on the radiator. I feel by getting her to cool better the less the fan has to run and the more hp is freed up to the motor.

I am not totally sure if my mind is thinking right on the scoop and flap idea. I know sometimes what makes sense in your head on what Air does and what it really does are 2 different things.

5th will be to slide the plate some the only theory here is that more hp will let me keep her at same speeds with lower RPM, but as me and my tech were arguing is even when it drops a gear rather than keep her pinned at 2.2k I would just back off the gas and keep it under 2k. The other idea though with the HP is being able to keep up the speed which helps with cooling, but more hp = more heat so who knows.

I will try and keep you posted on my gains and if there are any other ideas let me know.

Here is what she looks like when towing.
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Old 04-09-2012, 11:56 PM   #2
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I put a Banks kit on our ISC and now my reading on the filter minder is 15 and if I push it, the minder goes to 20 or slightly above although going to AZ didn't raise it even in the mountains. The filter I have is good for 1200 CFM and that should be enough for an ISL but still not enough for our ISC. Looking at going to a larger filter, which will necessitate going to larger tubing also. The CAC is OK as is though. We have a plenum intake on the drivers side up high and I may have to enlarge the intake there too.
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Old 04-10-2012, 12:09 AM   #3
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When I order this filter there is a 1200cfm option that I am pretty sure I can get to fit.

I just know my Duramax makes 430whp and 900tq and pulls though a pannel filter and does not pull the minder down. Also my 5.9 cummins in my 93 chevy at one point made 429whp 1029tq and ran 13.3@100mph in the 1/4 mi at 7700lbs and only ran a 4in tube K&N with a 6in round by 7in long filter. While I know the motor on the motor home is larger it still takes the same air to make hp. So I feel I will question the intake before the filter since the fitler looks to be 10x larger then any filter I have ever ran.
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Old 04-10-2012, 07:23 AM   #4
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You will always see vacuum pull on a filter mileage reminder due to the Bernoulli Effect of air rushing over an orifice. Just because it is in the yellow probably does not mean it is not enough airflow. The other thing is that how much air do you need coming through a filter at a steady MRPM at 62-65 mph without the turbo spun up. I bet it is not much and probably well with the air flow design of the filter. Now under max power accelarating or climbing may present a little problem but who cares about has mileage under full power. The one thing that would concern me with a side vent open like that is what happens in a rain storm. Water and paper air filters do not mix and the fibers expand and block airflow when wet.
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Old 04-10-2012, 07:57 AM   #5
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You might get more benefit out of reading these two publications
Attached Files
File Type: pdf Cummins MPG_Secrets_Whitepaper.pdf (375.9 KB, 513 views)
File Type: pdf CAT MPG Help.pdf (175.9 KB, 106 views)
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Old 04-10-2012, 08:14 AM   #6
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You might try a synthetic nanofiber air filter. These flow better than cellulose filters when clean and dirty and filter better than a wet gauze filter. Let me know your current part # and I will check for a replacement.

Also Ford Motor Company recently completed a mpg test where they replaced their conventional Texaco engine oil, transmission fluid and gear oil with AMSOIL synthetics and achieved a 6.54% improvement in fuel economy. PM me if you would like a copy of this report.

Also, the older diesels were made to run on the higher sulfur diesel fuels which also had higher lubricity. AMSOIL makes a Diesel Fuel Concentrate which adds lubricity and cleans the fuel system for more mpg. They state "Tests prove that AMSOIL Diesel Concentrate cleans dirty injectors, improving fuel economy by up to 5 percent and restoring horsepower to like-new condition. " [moderator edit]
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Old 04-10-2012, 08:25 AM   #7
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Is this an ad for Amsoil? So you sell Amsoil, do you sponsor this website in anyway? Didn't think that this was allowed if you are not a sponsor.
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Old 04-10-2012, 08:37 AM   #8
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Quote:
Originally Posted by Mike Canter View Post
Is this an ad for Amsoil? So you sell Amsoil, do you sponsor this website in anyway? Didn't think that this was allowed if you are not a sponsor.
He asked for other ideas and to let him know. Ford and SouthWest Research institute did the tests. I'm a retired Shell Oil chemist. Just trying to help him out with his objectives. I'm not selling anything here, just providing test data. No commercial links posted. If anyone has better data, please post. If I have violated any forum rule, please quote the rule.
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Old 04-10-2012, 08:58 AM   #9
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Then forgive me if I am wrong. It was the way the post was written. So you are or are not an Amsoil dealer?

A few years ago in the 1990's I had a International Long wheelbase scout with a self installed Data 44 computer which gave me very accurate MPG readout and I could calibrate it right on. I always had used and still use a major synthetic oil. I measured the MPG over a short straight and level stretch of road and did it several times so I had repeatable MPG on cruise control. I then drained out the oil and filled it with regular premium fossil oil. I then ran the same test again. I could see no difference in MPG. Maybe there was an improvement in MPG that would should up in 10,000 miles but nothing I could see in short term. I then drained the manual transmission and differentials of fossil oil and filled them with synthetic. Again no difference could be noted doing the same test. I was very disapointed. I do still use synthetic oil products in my regular vehicles but not in my motorhome.

I believe the rule is that you have to be a registered vendor to advertise a product that you sell.
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Old 04-10-2012, 09:18 AM   #10
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I am interested in the small changes in fuel economy of this post. I'm wondering why the exhaust is not addressed. Lucas they do make a muffler that claims better performance and mileage, Aero 5050XL is a unusual design. I recently installed this on our coach but have not had the chance to check fuel mileage difference. I ran Amzoil in a 96 Eagle and did notice a difference in fuel consumption.
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Old 04-10-2012, 09:25 AM   #11
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Yes, I am an AMSOIL Dealer. It was my 27 years as a Shell Oil chemist, studying independent standard method comparison tests and warranties, and conversations with Exxon/Mobil, Texaco, Shell/Pennzoil/Quaker State engine oil experts that also use AMSOIL that brought me to this point. If I can find better products, I can sell those as well. But I haven't in the past 20 years. But I am still looking.

When looking for MPG improvements, there are established engineering test protocols that do the best to eliminate influences outside of the lubricants themselves. Ford used the SAE J1321 In-Service Fuel Consumption Test Procedure for their test performed last year. Be sure to look at recent data as motor oil API categories change every few years and influence mpg.
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Old 04-10-2012, 10:24 AM   #12
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Thanks for the imput.

The p-pump on the cummins can run anything from Ethanol to 100% motor oil and live. Dont ask me know I know I have been runing 1qt of 2 stroke oil per tank on my durmax drying to save my crappy injectors. I know its worth a little mpg.

I have allready pulled the muffler off so it is just 4in straight pipe. My current MPG # are straight piped.
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Old 04-10-2012, 10:34 AM   #13
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Thanks for the imput.

I have been runing 1qt of 2 stroke oil per tank on my durmax drying to save my crappy injectors. I know its worth a little mpg.
You are welcome.

IMHO, you may be better off running a diesel fuel concentrate that was formulated and tested to save injectors and injector pumps. They cost about the same as 2 stroke oil, but have many other formulated and tested benefits.
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Old 04-10-2012, 12:07 PM   #14
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I have also seen test on 2 stroke oil done by magzines and it came out better for MPG then the aditives.

Also many of my diesel shops sware by 2 stroke oil being the best.

But anyway P-pump cummins dont have injector or pump problems for the most part. True million mile pumps and injectors.

I feel most of Amsoil test are to short tearm. I have seen 2 transmission that we run in our Lancer Evolutions that had over 100k worth of gear ware with in 10k so to say the least I am not a Amsoil fan. I have also seen 10+ oil pump faiures in our car from Amsoil peole telling people the 0w oils will be fine in there 700+hp 4 cylinders.

These are my facts proven to me by real life data. Not random test that skew the way they want.

Also with the amount of weight I will be pulling gear protecton is key. So I will just keep Proven factory fluids in her for now.
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