OBS Plenum Advice
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New User
Joined: Jun 2018
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From: Tucson, Az
OBS Plenum Advice
I've been doing a lot of upgrades to my truck, up pipes, down pipes, turbo, injectors, tunes, air filter, etc. The question I have is, how important is it to upgrade the 2 1'2" factory plenums to the larger 3"? also, will this affect the tuning at all, to the point that new tunes might be required?
Thanks!
Thanks!
Butt-Head
Joined: Apr 2004
Posts: 9,453
Likes: 2,936
From: Reed Point, MT
Easy.
If drive pressure for the turbine isn't reduced by installing up-pipes larger than 2" then how is overall flow increased on the intake side by going from 2" to 3"?
More intake flow requires more flow on BOTH sides of the head. It's no different than a stereo amplifier installation using a 4 gauge B+ lead and an 18 gauge ground lead .... there's a bottleneck somewhere.
There was obviously a reason Ford increased the size and I'll attribute it to the length of the intake tract after adding a charge air cooler and reducing flow resrictions on the piping walls due to air velocity.
There are zero tuning changes necessary with an intake plenum inlet change.
If drive pressure for the turbine isn't reduced by installing up-pipes larger than 2" then how is overall flow increased on the intake side by going from 2" to 3"?
More intake flow requires more flow on BOTH sides of the head. It's no different than a stereo amplifier installation using a 4 gauge B+ lead and an 18 gauge ground lead .... there's a bottleneck somewhere.
There was obviously a reason Ford increased the size and I'll attribute it to the length of the intake tract after adding a charge air cooler and reducing flow resrictions on the piping walls due to air velocity.
There are zero tuning changes necessary with an intake plenum inlet change.
Cargo Master
Joined: Nov 2009
Posts: 2,558
Likes: 19
I agree with cleetus here, however I pulled my plenums off and put flat plate ones with a three inch pipe in so the boots would stay in place.
With out the IC you would have to run a set of reduction boots backwards, anyway head ache. Maybe clean your fuel regulator for something to do. My two cents Canadian so take it for what its worth...
With out the IC you would have to run a set of reduction boots backwards, anyway head ache. Maybe clean your fuel regulator for something to do. My two cents Canadian so take it for what its worth...
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New User
Joined: Jun 2018
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From: Tucson, Az
nateairman - Thanks! I'll take the two cents Canadian. I'll add them to my collection.....lol Looks like I'll be staying stock as far as plenums for a while. Doesn't appear to be any reason to change, other than the billet 3" ones look a lot better...Not worth the price of admission though...
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Lead Driver
Joined: Apr 2016
Posts: 7,210
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From: Bahstun
Have to look at CFM vs pipe diameter for restriction losses
3in might offer a little more flow into the heads to keep EGT down but I wouldn't expect a huge difference
Maybe some before and after tests can be done.
3in might offer a little more flow into the heads to keep EGT down but I wouldn't expect a huge difference
Maybe some before and after tests can be done.
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Lead Driver
Joined: Sep 2002
Posts: 9,550
Likes: 2,034
From: North Texas
Heads flow really poor on the 7.3 DI, I would only upgrade if necessary (I believe T4 kits for example require them). Cost versus benefit versus hassle...plus I have never seen any data posted regarding gains, if any.
Maybe Navistar received a deal from a boot company, but only in 3" size.
Maybe Navistar received a deal from a boot company, but only in 3" size.
Laughing Gas
Joined: May 2012
Posts: 855
Likes: 5
From: Central Oregon
Easy.
If drive pressure for the turbine isn't reduced by installing up-pipes larger than 2" then how is overall flow increased on the intake side by going from 2" to 3"?
More intake flow requires more flow on BOTH sides of the head. It's no different than a stereo amplifier installation using a 4 gauge B+ lead and an 18 gauge ground lead .... there's a bottleneck somewhere.
There was obviously a reason Ford increased the size and I'll attribute it to the length of the intake tract after adding a charge air cooler and reducing flow resrictions on the piping walls due to air velocity.
There are zero tuning changes necessary with an intake plenum inlet change.
If drive pressure for the turbine isn't reduced by installing up-pipes larger than 2" then how is overall flow increased on the intake side by going from 2" to 3"?
More intake flow requires more flow on BOTH sides of the head. It's no different than a stereo amplifier installation using a 4 gauge B+ lead and an 18 gauge ground lead .... there's a bottleneck somewhere.
There was obviously a reason Ford increased the size and I'll attribute it to the length of the intake tract after adding a charge air cooler and reducing flow resrictions on the piping walls due to air velocity.
There are zero tuning changes necessary with an intake plenum inlet change.
Hotshot
Joined: Dec 2005
Posts: 14,377
Likes: 609
From: evansville in
At stock low boost levels 2" sure. Once you start adding boost the 2" inlets could very well becomena restriction.
Yea t4 is not stock boost levels.
There is no way I would stick with smalls at my boost level.
For most of you yea 2" is just peachy...
Yea t4 is not stock boost levels.
There is no way I would stick with smalls at my boost level.
For most of you yea 2" is just peachy...
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