Restrictor Horns
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Restrictor Horns
I've read in other threads that removing the restrictor horns from the air intake lines will improve fuel econcomy on my 460. Can anyone tell me why they are in there in the first place?
More Turbo
Joined: Nov 2003
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From: Peoria, IL (more or less)
Dunno specifically- but "restrictions", baffles, diverters, etc. are usually put in EFI intake tubes for one of two reasons: either to a) quiet the air flow noise, aka "silencers"; or b) to alter the airflow in some way. This usually means straightening it out or reducing turbulence, but in some cases (not EFI, obviously) things are placed somewhere in the intake passage to enhance mixture distribution.
On the off chance you are referring to an air cleaner housing rather than EFI, there's the valve to divert hot air into the engine for faster warmups. Air cleaner housings also often have baffles to reduce noise.
The upshot is, take a look at what's there & where, & give it a try.
If it's near the tube inlets, away from the intake, it's almost certainly for noise reduction. Another way to look at it: if aftermarket air kits replace those particular OE lines, it's probable the restrictors are for noise reduction.
Now, whether removing them will help much is another story, but at least it probably won't hurt anything.
On the off chance you are referring to an air cleaner housing rather than EFI, there's the valve to divert hot air into the engine for faster warmups. Air cleaner housings also often have baffles to reduce noise.
The upshot is, take a look at what's there & where, & give it a try.
If it's near the tube inlets, away from the intake, it's almost certainly for noise reduction. Another way to look at it: if aftermarket air kits replace those particular OE lines, it's probable the restrictors are for noise reduction.Now, whether removing them will help much is another story, but at least it probably won't hurt anything.
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From: Idabel, OK
I removed mine(90' EFI460) and it did seem to make a noticable improvement in the way the truck 'breathed'. It seemed to run and rev better, and seemed to improve power according to my SOTP meter and I would assume that if it makes enough difference that it can be felt, than it would be quite worthy and the best part is it just costs a little bit of your time.
By the looks of it, removing them would have to improve performance and relieve the intake tract of a restiction, which is always good. I didnt really notice much if any increase in noise.
By the looks of it, removing them would have to improve performance and relieve the intake tract of a restiction, which is always good. I didnt really notice much if any increase in noise.
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Originally Posted by stngh8r
I removed mine(90' EFI460) and it did seem to make a noticable improvement in the way the truck 'breathed'. It seemed to run and rev better, and seemed to improve power according to my SOTP meter and I would assume that if it makes enough difference that it can be felt, than it would be quite worthy and the best part is it just costs a little bit of your time.
By the looks of it, removing them would have to improve performance and relieve the intake tract of a restiction, which is always good. I didnt really notice much if any increase in noise.
By the looks of it, removing them would have to improve performance and relieve the intake tract of a restiction, which is always good. I didnt really notice much if any increase in noise.
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From: Idabel, OK
I do go to the track quite often and after the restrictor mod i got my best time to that date. See the sig.
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From: Idabel, OK
the only reason i did not mention it before was because it was not a back to back comparison(i.e. same day at the track) and i did not have a back to back dyno test or anything. But FYI- best time before was 17.0 and after the restrictor mod only on a maybe 10 degree cooler night 16.7! So there is your track time.
Post Fiend
Joined: Mar 2004
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From: Union, Washington
Originally Posted by stngh8r
the only reason i did not mention it before was because it was not a back to back comparison(i.e. same day at the track) and i did not have a back to back dyno test or anything. But FYI- best time before was 17.0 and after the restrictor mod only on a maybe 10 degree cooler night 16.7! So there is your track time.
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From: Idabel, OK
Drag Racing 101 is now in session
Originally Posted by Bear 45/70
You dropped a second by removing a noise reducer? I find that extremely hard to believe. You do realize the kind of power increase it takes to drop a second in the quarter mile don't you and in a heavy truck to boot. Just not possible in anybody's world.
As a general rule in drag racing:
10HP=0.1
100lbs=0.1
Just to stir the pot a little:
- I saw a .3 drop in the et when taking the airfilter out of the box. This was done with 2 baseline passes and 3 post airfilter removed passes.
Originally Posted by Bear 45/70
You do realize the kind of power increase it takes to drop a second in the quarter mile don't you
Quieres tu papa
Last edited by stngh8r; Jun 12, 2006 at 09:40 AM. Reason: change text
Post Fiend
Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Originally Posted by stngh8r
I do believe you are the one with very little track experience and also not capable of reading numbers into the tenths. I picked up .3 tenths, not a full second and yes I do believe that is very possible because the slower a vehicle is, the easier it is for speed to increase with mods. My truck weighs in at 5560, which is heavier as you correctly pointed out, but while that is a handicap, I can see no reason that this would hinder its ability to respond to mods.
As a general rule in drag racing:
10HP=0.1
100lbs=0.1
Just to stir the pot a little:
- I saw a .3 drop in the et when taking the airfilter out of the box. This was done with 2 baseline passes and 3 post airfilter removed passes.
- As a matter of fact I do. I saw a full second drop in the et with nitrous. BUT! On the dyno the nitrous only increased 40rwhp and 50rwtq???? For a total of 264rwhp/415rwtq(105* day and before the magnifico restrictor cutting mod)
Quieres tu papa
As a general rule in drag racing:
10HP=0.1
100lbs=0.1
Just to stir the pot a little:
- I saw a .3 drop in the et when taking the airfilter out of the box. This was done with 2 baseline passes and 3 post airfilter removed passes.
- As a matter of fact I do. I saw a full second drop in the et with nitrous. BUT! On the dyno the nitrous only increased 40rwhp and 50rwtq???? For a total of 264rwhp/415rwtq(105* day and before the magnifico restrictor cutting mod)
Quieres tu papa
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From: Idabel, OK
Bear, I am sorry that you doubt. I am also sorry that I got defensive in the first place. I, like yourself, am also very skeptical when people speak of gains they got and then find out they have no basis for their comments. I have logged many passes at the drag strip and have a few trophies as well(one was obtained weekend before last). As hard as it may be to believe, the clean paper air filter being removed on the same night showed .3 and the restrictor horn thing did help as well IMHO. The air horns in the intake tract of these EFI trucks are pretty small, so It would seem quite feasible to me to gain HP by removing it.
As far as the general rule thing, I agree, it is a general rule. My truck picked up a second with nitrous that only showed 40rwhp gain on the chassis dyno; on the contrary, my low 12sec ls1 vette barely picks up a 2/10s at best with a 50shot?
tsavino-sorry for the deviation in topic, please do give the restrictor horn thing a try, its not going to hurt and I feel that it is a worthy free mod.
hehe, no I am not a car salesmen
Dr. E
As far as the general rule thing, I agree, it is a general rule. My truck picked up a second with nitrous that only showed 40rwhp gain on the chassis dyno; on the contrary, my low 12sec ls1 vette barely picks up a 2/10s at best with a 50shot?
tsavino-sorry for the deviation in topic, please do give the restrictor horn thing a try, its not going to hurt and I feel that it is a worthy free mod.
hehe, no I am not a car salesmen
Dr. E
Post Fiend
Joined: Mar 2004
Posts: 6,056
Likes: 8
From: Union, Washington
Originally Posted by stngh8r
Bear, I am sorry that you doubt. I am also sorry that I got defensive in the first place. I, like yourself, am also very skeptical when people speak of gains they got and then find out they have no basis for their comments. I have logged many passes at the drag strip and have a few trophies as well(one was obtained weekend before last). As hard as it may be to believe, the clean paper air filter being removed on the same night showed .3 and the restrictor horn thing did help as well IMHO. The air horns in the intake tract of these EFI trucks are pretty small, so It would seem quite feasible to me to gain HP by removing it.
As far as the general rule thing, I agree, it is a general rule. My truck picked up a second with nitrous that only showed 40rwhp gain on the chassis dyno; on the contrary, my low 12sec ls1 vette barely picks up a 2/10s at best with a 50shot?
tsavino-sorry for the deviation in topic, please do give the restrictor horn thing a try, its not going to hurt and I feel that it is a worthy free mod.
hehe, no I am not a car salesmen
Dr. E
As far as the general rule thing, I agree, it is a general rule. My truck picked up a second with nitrous that only showed 40rwhp gain on the chassis dyno; on the contrary, my low 12sec ls1 vette barely picks up a 2/10s at best with a 50shot?
tsavino-sorry for the deviation in topic, please do give the restrictor horn thing a try, its not going to hurt and I feel that it is a worthy free mod.
hehe, no I am not a car salesmen
Dr. E
I have found that in drag racing the torque numbers effect ET and horsepower numbers effect mph normally. I once had a 3800 pound car with a 3:1 rearend that ran 14.7 at 99mph using first and second gear only. Switched to a 4.30 rear with the same tires and then ran 14.05 at 100mph. The gear changed multiplied the torque for a much better ET but horsepower remained pretty much the same.
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