Engine air intake grill

[Ken L.]

A ISL 400 has a 543 cu inch displacement.
Where did you get the information that it used 672 CFM at 2100?
I plugged it into the program and it shows that engine with turbo requiring
990 CFM at 2100 rpm.
With this information the air intake grill is way to small and should be almost double
Hummm? That is a good question, I have it written down on a piece of paper.
543 cid is correct though. The 990 C.F.M. only works to make it worse. I did find that with a new filter the MAX. on the filter minder should be 10.0--h2o, and with a dirty filter the MAX. would be 25.0--h2o.
It would be great if someone who tried this modification would see this thread and chime in. I guess I have to figure a way to enlarge the intake grill.
672 CFM at 2100 RPM I wonder where that came from???? Later, Ken

[wb7auk]

[QUOTE=Ken L.;2947458]A ISL 400 has a 543 cu inch displacement.
Where did you get the information that it used 672 CFM at 2100?
I plugged it into the program and it shows that engine with turbo requiring
990 CFM at 2100 rpm.
With this information the air intake grill is way to small and should be almost double
Hummm? That is a good question, I have it written down on a piece of paper.
543 cid is correct though. The 990 C.F.M. only works to make it worse. I did find that with a new filter the MAX. on the filter minder should be 10.0--h2o, and with a dirty filter the MAX. would be 25.0--h2o.
It would be great if someone who tried this modification would see this thread and chime in. I guess I have to figure a way to enlarge the intake grill.
672 CFM at 2100 RPM I wonder where that came from???? Later,

Driving down the road using very little boost it is a toss up on mileage effect as your engine is using something like 534 CFM but the second you start adding fuel that also increases boost things go south as the grill restricts air flow big time and your fuel usage suffers.
The smallest amount of vacuum you have is great I change filters once they are above 17 inches as I have found your fuel mileage starts suffering because the intake air temp starts climbing at the engine.

[Ken L.]

OK, I have taken off the intake grill, and taken some pictures. The effective usable area seems to be about 3"w. x 8.5" h. or 3'w x 5.75"h. If you can see the pictures and look at the tape measure showing the opening size between the louvers, you can see 2'25" on one opening, 2.5" on one opening and 1" on the other opening. That comes to about 5.75"h x 3"w of open area in the grill to suck the air through. Until I can open the box in the closet that houses the collector box I will not know what it might take to enlarge the opening. It doesn't look like fun. I just hope that it might be worth it??

[wolfe10]

Yes, Ken. Please do keep us posted on air filter minder reading pre and post improvement. Also any performance changes. Could be a very worthwhile upgrade.

[greenmachine]

Ken, when you took the grille off , could you tell the center of the metal stud in the wall. That's panned in and looking at it seems to be wider once you go past the opening. I measured mine and its 6inches wide once you past about 2 1/2 inches in. When I tapped on the wall it felt like a metal stud on one side and hollow on the right. I looked under and that is a dust and water problem. I can't go up. I know where I can get another one of those grilles but not on sell. Here Vision junk yard has them and put two side by side if the metal stud wall will let you or go to a sheet metal shop and have one made to fit. Point is I think you can widen that opening enough right there.
Thanks
Larry Pate
2003 Alpine 38FDDS 350 ISC

[Koop]

These calculations aren't as simple as they seem. The air filter housing (airbox) is a Helmholtz resonator. Properly sized it will reach a resonate frequency somewhere around the peak torque RPM. This creates a supercharging effect. The engineers that designed this stuff weren't backyard mechanics, they had an idea of what they were doing.

Changing the dimensions of the intake and/or airbox may be detrimental to performance. Just saying

[wb7auk]

Every Helmholtz system I have seen on a intake was used to reduce intake
noise.

[Koop]

Originally Posted by wb7auk

Every Helmholtz system I have seen on a intake was used to reduce intake
noise.

Really? Not my experience.

[wb7auk]

We don't have 180 degree crankshafts and a even firing engine for starters but it has been awhile things might have changed.

[Ken L.]

Originally Posted by Koop

These calculations aren't as simple as they seem. The air filter housing (airbox) is a Helmholtz resonator. Properly sized it will reach a resonate frequency somewhere around the peak torque RPM. This creates a supercharging effect. The engineers that designed this stuff weren't backyard mechanics, they had an idea of what they were doing.

Changing the dimensions of the intake and/or airbox may be detrimental to performance. Just saying

OK Guys, we all have had our problems with the engineers ideas. If they had gotten it all right, we wouldn't have to build reinforcing brackets for our Steering Box mount. I have found many things that were not as good as they could be on my coach. One other area was with the Furnace cycling, it didn't even come close to having enough ductwork installed to run up to temp. with out going off on "High Heat safety shutdown". I am not an engineer, but I know when things aren't working [sometimes].
Helmholtz Resonator that is a whole subject and the concept could be applied to Air as Cavitation is to liquid. If you could lower the resonance in an air flow, you might be able to increase the air flow in the system? Doing it at the collection point, as at the intake grill, seems unlikely to effect this coaches performance. Not getting enough Air in to the system, might?
I am so glad that so many have weighed in on this subject, I will continue, with your help, to try to find an answer. Ken

[Koop]

Originally Posted by wb7auk

We don't have 180 degree crankshafts and a even firing engine for starters but it has been awhile things might have changed.

Inline six cylinder engines have even firing intervals every 120 degrees of crankshaft rotation.

[wb7auk]

Mike,

When you find a diesel with turbo using a Helmholtz resonator to increase the little power one gains at low RPM and the coach maker that went to the expense for each unit please send me that link I would be interested.

[Ken L.]

Originally Posted by wb7auk

Mike,

When you find a diesel with turbo using a Helmholtz resonator to increase the little power one gains at low RPM and the coach maker that went to the expense for each unit please send me that link I would be interested.

This is not a link, it is a picture of what is in my coach. It looks like a
plastic rectangle to round adapter from the side wall to through the floor for air to the engine. If there is any more engineering than that, it is not apparent.
The opening through the wall seems to be surrounded with aluminum framing.
That might mean I would have to remove the rear side piece to get another Grill side by side with the existing? Now if I can find a suitable S.S. grill?
Still thinking on this one. Ken

[wb7auk]

Can not see for sure but looks like it has a bulge on one side and the other side looks like it was caulked to seal a damaged unit.
Anyway as I posted earlier it is providing for air intake and a noise reducer if I am correct.