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Old 01-30-2016, 08:44 PM   #1
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Engine air intake grill

I have been looking at the stainless steel air intake grill, it looks way too small to me. The effective opening size is 16.5 sq. in. Two openings about 3"w.x 2.25"h, and one 3"w x 1"h. It is connected to a 7"dia pipe to the Air Cleaner housing. The engine is rated at 672cfm @ 2100 rpm. Will that much air really fit through 16.5 sq. in. of opening? Would bigger be better in this case? In residential grill sizing 672cfm would require a 6" x 16"---580cfm. or 8" x 18"---732cfm size grill. Has anyone looked into this issue, could we be getting better mileage if we had more air available?
Just a thought? Ken
Ps. 7" dia. = 38.48 sq. in. of area.
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Old 01-31-2016, 07:12 AM   #2
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Ken, you could be on to something. I had a dodge with 5.9 Cummins and I changed the air intake on it and it gave me more power and better fuel mileage. I would say if you contact Cummins they could help. I know they where involved in the radiator, so Its hard to think they didn't check the air. I believe there's ok, good, better. What does other Coaches have on there coach. They let the older Dodge trucks go lacking air. When the weather breaks here, I'll look at mine to see what could be done. I have a mud flap on my coach and I think its like a sail boat it pull back on the coach also. I see some are brushes then some on a chain, mine is solid and thick rubber. It just pushes dust up in the motor.
Thanks Ken
Larry Pate
2003 Alpine Coach 38FDDS 350 ISC Cummins
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Old 01-31-2016, 08:22 AM   #3
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What is your air filter minder reading? It logs maximum vacuum on the intake system: coach side opening, ducting to air filter and air filter itself.

Sure, if excessive restriction is noted, then you might consider a larger side of coach opening. Have seen that on several Alpines of your vintage.

If restriction is not excessive, probably not worth worrying about.

Brett
2003 Alpine 38FDDS
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Old 01-31-2016, 10:17 AM   #4
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The math notwithstanding, this issue has come up before on this forum--might consider doing a search for more details. Believe several Alpine owners have added a second inlet louver [see West Marine] and expanded the air box behind the side-wall to accommodate the larger opening. Dont recall any follow-up regarding improved performance or fuel mileage increases. Tend to agree that except on the margins, if the restrictive filter minder is not indicating a significant vacuum, you would not be gaining much [except another louver].
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Old 01-31-2016, 12:40 PM   #5
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Interesting observations. My filter minder does not show a drastic vacuum or restriction, it barely moves at all. I don't get to travel as much as I would like, so not as many miles a year as some might see. I have a neighbor who has a 7.2 ford truck with twin stacks. Yesterday I asked him, "how do you get enough air into that engine to feed those stacks"? He said interesting thing, "I replaced the air intake with an after market unit and picked up 3 MPG." That is what started me on this subject. I will search for more info regarding Alpine Air intake. Thank you, Ken
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Old 01-31-2016, 01:27 PM   #6
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Indeed, how much you will gain (if anything) depends on how much restriction you currently have.

Certainly, a "boosted/hopped up" engine like your neighbors truck will benefit from more than OE CFM's.
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Old 01-31-2016, 02:48 PM   #7
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Old Scout, I guess my search technic is not good, I cannot find anything on this Air intake subject. What am I doing wrong? Ken
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Old 01-31-2016, 03:44 PM   #8
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Ken--seems the search function on IRV2 only goes back about 2-3 years--unless I am missing something too. This issue goes back a long way--more than two years. Hopefully one of the owners involved with the original post will chime in......sorry to mislead you.....
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Old 02-15-2016, 07:45 PM   #9
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OK. I wandered around a big RV show today. I looked at every Diesel Pusher there.
EVERY one of them had at least TWO times the surface area and many had way more than that. That means Mine [ours] are the smallest out there, at least that I can find. It seems that the newer the Coach the bigger the intake??? I'm still thinking about this. Ken
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Old 02-16-2016, 08:45 PM   #10
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Quote:
Originally Posted by wolfe10 View Post
What is your air filter minder reading? It logs maximum vacuum on the intake system: coach side opening, ducting to air filter and air filter itself.

Sure, if excessive restriction is noted, then you might consider a larger side of coach opening. Have seen that on several Alpines of your vintage.

If restriction is not excessive, probably not worth worrying about.

Brett
2003 Alpine 38FDDS
This
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Old 02-17-2016, 04:32 PM   #11
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Ken, I have the 350 cummins on my 2003 38FD. Are the intake the same size opening on 2003 with the 400 cummins ?
Larry
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Old 02-17-2016, 04:45 PM   #12
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Yes--same size! Still looking to hear from an owner who has done this upgrade-- eg, better MPG or less restriction????? [Vic, where are you--probably on the Entegra website....]
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Old 02-18-2016, 06:49 AM   #13
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I've done a little checking and with normal operations the air is fine could be better. Where the trouble is when you have yours trying to push your coach over a hill. I was asked about temperature readings and I explained I didn't have that until now. I installed the silver leaf program on my coach. I had a program on my dodge and the size of the intake was not the problem it was the restriction in the filter. Each filter has a rating and the paper filter really restricts. So I keep bring up dodge because that's the only thing I have changed from factory to now. There is no problem with thinking that it wouldn't help. Now the cost to change and the gain from this. I will say on my own thinking that going down the road at 60 to 70 you wouldn't notice anything. If you want to get up and go past a car or truck fast ,you could tell the difference. If you are going up a long hill you could tell the difference and the intake and exhaust temperature would show its going to be cooler. I will be able to tell temperatures this year. My dodge had all the things that tell you if vaccum was to great on intake but I change the filter and intake out it made one big difference. I'm sending out question to these filter company's and waiting to see who will step up. I did go to search at top of page and google air intake problems and there where some forums on this for other brands but didn't get into it deep. I'm trying to find the data on the filter to see which one is less restricted. Then I have to watch for dust. Where I live about three hours away is that Vision junk yard. Higher than hell. But I'm wondering if they had another grille like the one I have and put it right above the one I have and tee into the pipe. It wouldn't be on sell. When I here back on the filters I will jump back in here and will be watching for what you guys find out. I can here my wife now if its not broke don't fix it. Thanks everyone
Larry
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Old 02-18-2016, 06:56 AM   #14
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Scientific way to approach it is for those with same engine (Cummins ISL) to read air filter minder gauge BEFORE the coach-side inlet enlarged.

Then reset air filter minder and do a 0-60 MPH at Wide Open Throttle and then read air filter minder gauge.

THAT will tell you whether this is a valuable upgrade.

Brett
2003 Alpine 38FDDS
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