New 290DC Over-Propped

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Re: New 290DC Over-Propped

Postby Trent » Mon Oct 27, 2008 8:16 pm

conehead39 wrote:AskHarry.
5400 is about 500 rpm low. Ideal is 5900-6000, but your cruise mpg may not change if you go to 3x16x20.

There are lots of factors that enter the best cruise mpg. Just read the various OB mfgs test.Try some other rpms like 3800and 4200.
Reread WCC test data NOTES about no electronics, no gear, ie like outriggers, fishing rods in rod holders,anchor ,anchor chain.
1. Did you bottom paint it? Harry and Us have gotten very good results with Micron 66 with very low mpg reductions and application life. We know for a fact that another cheaper Micron gave less gas mileage, We only left it on 4-6 months.
2. Were you going into a head current, ( go both directions)
3. Was it a hot + humid day = less HP for a given rpm.Yam and Honda prop tests were Jan. Feb
4. 180 fuel x 6.3 lb/gal= 1134 lbs
5. 35 g fresh water + 15 gal waste =50g x 80% x 8 lb/gal= 400 lbs.
6. How much additional equipment have you added .If you did you probably put it up front making it more nose heavy.

1. No paint, lift kept
2. Tried both
3. No, actually it was a cool day low 70's
4. Yes, I had 180 fuel
5. Yes, I had about 35g fresh water but waste tank is empty
6. No additional gear except for electronics... maybe 15-20 pounds total with half that in rear due to transducer

To address other posts:
1. No riggers, no rods, no gear of any kind
2. Yes, I'm coming up short on RPM without gear so it will only get worse (with some mitigation after break in).
3. The good news is dealer is going to put some 20 pitch props vs. 21.5's and I'll report back results in a few weeks
4. I don't believe test results either ;-)
5. I'll fill the tanks and try a long trip soon to test accuracy of meters... will let you know what I find
2008 290DC, 2x250 Suzuki, Garmin GPSMAP 5212, GHP10 Autopilot, GMI10 Display, GPS17X NMEA 2000 Antenna, GSD22 Sounder

Greg Manning
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Re: New 290DC Over-Propped

Postby Greg Manning » Tue Oct 28, 2008 5:50 am

Harry Brosofsky wrote:01 Excursion 7.3 - 16 city, 21 highway, 17+ average
04 F-250 CC SRW 6.0 - 15 city, 18 highway, 16 average
06 F-350 CC DRW 6.0 - 13 city, 16 highway, 15 average
08 F-450 CC DRW 6.4 - 11 city, 13 highway, 11.5 average

Great motor, lousy economy. Of course I also have 4.30 gears and it's a 450, which weighs more than 500 more than a 350.


Thanks Harry...must have remembered the Excursion number. Always a Ford towing vehicle disciple but I have liked the Duramax so far.
Moved back to the dark side

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Re: New 290DC Over-Propped

Postby conehead39 » Tue Oct 28, 2008 7:29 pm

My friend that I recently delivered his 2008 Duramax says the gas mileage is lower than his earlier 04 w 5 speed allison..
Even with 6 speed on the 08. However the 08 has the Diesel Particulate Filter in the exhaust.
I all have heard about DFPs is the exhaust is quiet ,does not smell like a diesel but reduces gas mileage.

It is probably going thru growing pains like the 1975-80 Catalytic converters.

Best combo for a Duramax is the first year with 6 speed, probably 06 and 07 the best.
06,33TE,F250TXR Yam,15.5x17x3w sds;bottom micron 66,2house2150Ody;start 2 Dek
ShermanTwr w cont,Lee ORig,Gar 3010wbathy,XM,440uppr.Fur 582L, B258idTD forw bilge.Sim AP16, Icom 402, Shakes 5225XPant.ACREPIRBwGPS.

Harry Brosofsky
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Re: New 290DC Over-Propped

Postby Harry Brosofsky » Tue Oct 28, 2008 7:36 pm

Same deal for Ford and Dodge. The DPF works by trapping soot, then when it senses a certain degree of clogging, raw fuel is dumped in after the turbo (basically an afterburner) to clean out the DPF. You can actually fell the power drop and watch the economy decrease when it happens.

'03 330TE, Zuke DF250s, Ray C-120 (2), RS-125 (2), 4KW dome, DSM300, M260, Icom 504A (2), CommandMic III (2), Navman Fuel 3100, Jensen MCD-A1, XM SkiFi II, DC Gold 6x9s (4), Odyssey PC2150 (2), BEP 717+, scuba rack, hardtop rear arch, extra rod holders

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Re: New 290DC Over-Propped

Postby v70catboat » Wed Aug 04, 2010 10:17 am

BMW uses urea to clean the exhaust, wonder why the US companies don't?
2006 270 SD with twin Honda 225's

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