Intake Horn restriction

[Vaughn MacKenzie]

Yesterday I removed my intake horn to drill and tap for my boost gauge and as I suspected there is a considerable restriction at the concaved sides that clear the mounting bolts. It's worse than I would have guessed! It's quite a bit tighter than the 2nd Gen trucks and certainly significant enough to affect airflow when you crank up boost and power.



I think anyone going after improved performance will want to address this. I hope one of our vendors will take an interest in this and come up with a decent air horn that will maintain good flow through to the intake area.



Vaughn

 

[HoleshotHolset]

Vaughn:



Even though we all know less restriction in the intake stream is usually a good thing...



The net gains from modifying the OEM horn or manufacturing an aftermarket horn probably don't outweigh the costs involved.



If they did... then we'd all have 'em on our trucks... .



My point is that when you're shoving 30+psi at the cylinder head... the little things don't matter so much anymore.



No flames intended... just giving my $0. 02 worth...



Matt

 

[Vaughn MacKenzie]

You're right Matt it's not going to make a huge difference but when you're wanting to get peak performance from your Cummins then this is a definite spot for improvement. With high boost pressure you can cram the air past, but the greater the air pressure the greater the parasitic drag/friction past this point, not to mention increased heating of the air forcing its way past. When you're spending the $ for turbos and boxes then it would make sense to eliminate or reduce restrictions that stand in the way of getting the air from the turbo to the cylinders.



Someone is sending me a 2nd Gen intake horn to try on my '03 to see if it fits. If so then the fix should be pretty easy. . . get a 2nd Gen horn, it looks far less restrictive. I haven't priced them though so I don't know how spendy they are. If someone had a PN I could check with Cummins NW.



Vaughn

 

[rbattelle]

I gotta side with Vaughn on this one, Matt. He makes a good point. Maybe you could remove your existing horn and take it to a machine shop to have it "bored" out a bit?

 

[scotty1]

For every turn, change in shape and size you get more and more restriction/turbulence.

We already started on a totally different approach to this then a different intake horn like some out there for the 2nd gens.

As I learn more about air flows and fuel flows I have found some MAJOR bottlenecks that have a definate backlash on the performance. Surprising how that intake horn can effect things pre intercooler.

 

[HoleshotHolset]

The following post is not meant to be heated, nor was it written with intent to cause fire, flames, or explosions...



OK - do the work, figure out what it costs then do a before/after dyno run on the same day...



You ought to be able to do two runs within 5 minutes of each other... one with the OEM horn... one with a hogged out or 2nd Gen horn... post the results and tell me if it was worth it. I'll take back everything I said if you prove me wrong.



With everything else the same - I highly doubt you will see any gains.



Again, we all know that reduced restrictions have benefits... but this is one area that many people have messed with over the years... and the end result has been the same. They spent money and didn't get anything out of it.



Matt

 

[Vaughn MacKenzie]

Scott1 I'm happy to hear you guys are looking into this. Are you/Wildcat Diesel seriously looking into coming up with a solution? I think with the right product at the right price there would be some takers especially if it's proven to work. Have you taken a peek inside your horn?



Holeshot I agree with trying it on a dyno, but even if it's only a 5hp gain that's 5 more HP going to the wheels. It would be worth trying it that's for sure. Here is another idea: take an untouched 3G airhorn and tap in before and after the restriction and then measure boost readings at both locations, and see how much boost loss there is at 10, 20, & 30psi. That would tell you if indeed there is a dynamic restriction.



Vaughn

 

[HoleshotHolset]

5hp would be a reasonable gain... provided it didn't cost you an arm and both legs.



Not having seen too many 3rd Gens - I can't see why this horn would be so much more restrictive than the 2nd Gen trucks...



Did Cummins/DC cut corners again on the 3rd Gen trucks?

No wheel liners, thin paint, thin sheetmetal, now this?!



Matt

 

[Joseph Donnelly]

They didn't cut too many corners. Shipping weight of my 04 is more than 1000 lb. heavier than my 97. The earlier horn fits but you need an aftermarket hose because it points at a different angle. Also doesn't make any difference in performance, according to careful dyno and road testing by Lawrence.

 

[dieselpilot1969]

Originally posted by Vaughn MacKenzie

Yesterday I removed my intake horn to drill and tap for my boost gauge and as I suspected there is a considerable restriction at the concaved sides that clear the mounting bolts. It's worse than I would have guessed! It's quite a bit tighter than the 2nd Gen trucks and certainly significant enough to affect airflow when you crank up boost and power.



I think anyone going after improved performance will want to address this. I hope one of our vendors will take an interest in this and come up with a decent air horn that will maintain good flow through to the intake area.



Vaughn

what about getting the thing extrude honed?

 

[Vaughn MacKenzie]

Well I grabbed my airhorn and took some measurements:



Size of Opening at restriction: 1. 44" x 2. 8"

Size of circular horn entrance: 2. 563" Diameter



Soooo



Cross-section area at restriction = 4. 03 square inches

Cross-section area at entrance = 5. 16 square in.

Loss in area = 1. 13 sq. In.



Well a loss of a square inch in cross-sectional area doesn't sound bad but it's a 21% restriction. Not only that but the air is cramming past two bulges that intrude more than 1/2" on each side forcing the air through a gap that is less than 1. 5" wide.



Vaughn

 

[Vaughn MacKenzie]

Originally posted by HoleshotHolset

Not having seen too many 3rd Gens - I can't see why this horn would be so much more restrictive than the 2nd Gen trucks...

Holesett Check these out, not the best pics though. . .



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[KLockliear]

Already tried it. No difference in spool up, EGT or power.

 

[Vaughn MacKenzie]

Already tried a 2G horn? At what HP level(s)?



Another pic for Holesett https://www.turbodieselregister.com/user_gallery/sizeimage.php?&photoid=8898&width=0



Vaughn

 

[HoleshotHolset]

Thanks for the pics Vaughn... .



They got away from using the long bolts and just changed the casting to allow the use of short bolts on all 4 corners. Very interesting.



I guess I don't have to eat crow... . it has already been tried by a reputable guy and it didn't work.



Matt

 

[KLockliear]

Originally posted by Vaughn MacKenzie

Already tried a 2G horn? At what HP level(s)?



Vaughn

500rwhp.

 

[Vaughn MacKenzie]

Well you're not supposed to say that Keith! I wanted you to report at least a 50hp increase by switching out air horns



LOL this has made for some good discussion though