Designed induction restriction
Designed induction restriction
(OP)
I would like to see if anyone can make some sense of this.
A 1996 Ford F250 with a 460 Engine.
Running from the airfilter is 2 large rubber hoses, they come to a plastic junction, that has a very small hole maybe an inch or so diameter that connect from each hose, that restrict the airflow, then 2 large hoses come off the other side that then feed the air to the throttle body.
This is so counter to any logic as far as getting airflow into the engine. Does anyone know why this was done? This is stock factory on all these, and I think many more models as well. I would think this would help to decrease fuel economy as well. Any ideas? Thanks.
A 1996 Ford F250 with a 460 Engine.
Running from the airfilter is 2 large rubber hoses, they come to a plastic junction, that has a very small hole maybe an inch or so diameter that connect from each hose, that restrict the airflow, then 2 large hoses come off the other side that then feed the air to the throttle body.
This is so counter to any logic as far as getting airflow into the engine. Does anyone know why this was done? This is stock factory on all these, and I think many more models as well. I would think this would help to decrease fuel economy as well. Any ideas? Thanks.





RE: Designed induction restriction
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Generally when you see odd things in the intake it was put there for sound/noise reasons. I'm unclear from your description if the 1" hole is connecting the two hoses together or if both hoses are being restricted down to 1"? Since the hoses are different lengths connecting them together probably helps to dampen each other's natural resonance, making it quieter. I checked on a couple of web sites, included Gale Banks, and they don't remove that plastic piece with the power kits - which makes me believe it isn't hurting your power. (but a picture would convince me!)
ISZ
RE: Designed induction restriction
RE: Designed induction restriction
RE: Designed induction restriction
RE: Designed induction restriction
They are mounted midway between the air filter box and the engine throttles but are tucked inside the outlet hoses of the ISC supply tee. On the photo from IceStationZebra, it is visible directly over the AC compressor.
On a whim, I sawed them off (I have a spare) and can detect no difference in performance or noise, although I suspect it has to do with intake pressure wave tuning.
Franz
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RE: Designed induction restriction
Cheers
Greg Locock
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RE: Designed induction restriction
RE: Designed induction restriction
Here are the two venturi's I sectioned off. They are in the inlet of the tee, between the air filter box and the tee. I cant find the replacement tee, they are frequently removed when converting one of these monsters to propane. Oh well, its running just fine, right now, its on the road.
Franz
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RE: Designed induction restriction
Cheers
Greg Locock
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RE: Designed induction restriction
Franz
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RE: Designed induction restriction
Cheers
Greg Locock
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RE: Designed induction restriction
Franz
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RE: Designed induction restriction
BTW, measure the intake valve opening, and figure out air speeds, and flow from that and you will see it's a much greater restriction than those two venturi's were. They will have an effect on airflow at very high engine speeds, but you will destroy the engine from an over-rev long before you max out the drlivery through those tubes. That of course is why there was no obvious improvemnent in performance when they were removed.
RE: Designed induction restriction
More than likely it would have been advertised as some wiz bang idea that covered up the inadequate breathing design.
Even though i haven't viewed the port sizes on this particular engine one would imagine they would be like typical Ford design ports & big enough to stick your head in & destroying good Torque curves.
Remember it is just a factory engine & nothing special.
Anti reversion could be ruled out---anti reversion needs to start at the valve seats, valves & intake runners etc.
If there is a reversion problem that far up the intake tract then Ford had better go back to the drawing board.
RE: Designed induction restriction
Waves can exist in any part of the duct and therefore reversion can exist anywhere.
This seems to me to be a device that will limit power and reduce noise emissions from the inlet tract.
Regards
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RE: Designed induction restriction
Patprimmer is right on about increasing air velocity, it just aint happening in this case. The hose diameter immediately after the venturi body is the same size as the hose size immediately before it.
Franz
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RE: Designed induction restriction
- Steve
RE: Designed induction restriction
Though it could be other factors, but it seems to idle a bit rough and has a slight what I call a mid range flutter. Could be the China autolites, or the old cap/rotor, other wise this is a fresh engine. So now I'm on the hunt for another part. When I get a chance I'll take some measurements and post them.
RE: Designed induction restriction
Bore 4.440" ?
Stroke 4.5" ?
Intake valve size?
Intake valve lift?
Thanks
RE: Designed induction restriction
Thanks
RE: Designed induction restriction
4.360" bore
3.850" stroke
4.900" bore spacing
6.605" rods
10.322" deck height
1.756" piston compression height
3.000" main journals
2.500" rod journals
(2008 FRPP catalog, which I happened to have open for an unrelated reason)
Norm