03 cobra tube headers boost drop

[blwnblkgt]

i have a question how much boost drop will i see with long tube headers. my set up is tvs with 13psi pulley and a 10:1 compression engine. and also do cams really lower boost as well because I'm thinking of doing set of cams

 

[wile e coyote]

Boost is simply a measure of resistance. Headers, exhaust, cams etc can lower boost because they make a engine more efficient. A engine is nothing more than a big air pump..........if you grab a straw and blow as hard as you can, only so much air can get through right? That backpressure is "boost". But grab a garden hose and you can do it
much easier......so you can actually move more air, but your "boost" numbers will be lower because there isn't such a restriction.


Make sense?

 

[Bigggy]

Boost is simply a measure of resistance. Headers, exhaust, cams etc can lower boost because they make a engine more efficient. A engine is nothing more than a big air pump..........if you grab a straw and blow as hard as you can, only so much air can get through right? That backpressure is "boost". But grab a garden hose and you can do it
much easier......so you can actually move more air, but your "boost" numbers will be lower because there isn't such a restriction.


Make sense?

Voila!

Rule of thumbs, about 2 PSI for LTs.

 

[Stage 4.6]

Boost is simply a measure of resistance. Headers, exhaust, cams etc can lower boost because they make a engine more efficient. A engine is nothing more than a big air pump..........if you grab a straw and blow as hard as you can, only so much air can get through right? That backpressure is "boost". But grab a garden hose and you can do it
much easier......so you can actually move more air, but your "boost" numbers will be lower because there isn't such a restriction.


Make sense?

Awesome explanation! love the way you broke it down.

Voila!

Rule of thumbs, about 2 PSI for LTs.

That sounds spot on, I dropped 1.5psi w/kooks LT & 3in catted x-pipe

 

[blwnblkgt]

Makes perfect sense! Thanks

 

[Lycosa]

Boost is simply a measure of resistance. Headers, exhaust, cams etc can lower boost because they make a engine more efficient. A engine is nothing more than a big air pump..........if you grab a straw and blow as hard as you can, only so much air can get through right? That backpressure is "boost". But grab a garden hose and you can do it
much easier......so you can actually move more air, but your "boost" numbers will be lower because there isn't such a restriction.


Make sense?

So does the loss in boost mean using a smaller pulley to compensate is a good idea?

 

[Freakingstang]

So does the loss in boost mean using a smaller pulley to compensate is a good idea?

Some guys do...

you aren't "loosing" boost tho... people get stuck on this damn number..

A stock motor on 16lbs will make less power than the same motor with HCI on 12-13 lbs. you want to make as much power as you can on the least amount of "boost".

 

[Bigggy]

Boost is a measure of restriction, less boost with LTs does not mean that you loose power simply tells that the engine is breathing better. You will make the same or more power with less boost, so that's a good thing.

 

[04dreamcobra]

I did LTs and cams. Boost drop was about 4-5 psi. Made more power too even with the lower boost.

 

[GodStang]

So does the loss in boost mean using a smaller pulley to compensate is a good idea?

Most do. The boost drop will depend on size of headers. Typical drops depending on most common 03-04 Cobra LTs is 1.5-2psi. Some times less some times more. Improvements on restriction before the PD blower increase boost and Improvements in restrictions after the PD blower decrease boost. CFM the blower moves does not change just the restrictions in and out.

 

[Bdubbs]

By just adding headers my boost dropped 1 psi.

 

[tt335ci03cobra]

Also, 13psi from a 2.3L blower is much more air than 13psi from a 1.6L blower.

Same way it's funny in the turbo world when a guy says something like "ya I'm running 40psi bro" and acts all cool and show off like about it, but they don't understand that 40psi through a 2" t2 is literally like 12psi through a 3.5" t4.

 

[GodStang]

Also, 13psi from a 2.3L blower is much more air than 13psi from a 1.6L blower.

Same way it's funny in the turbo world when a guy says something like "ya I'm running 40psi bro" and acts all cool and show off like about it, but they don't understand that 40psi through a 2" t2 is literally like 12psi through a 3.5" t4.

For stock 03-04:
~14.5psi on an Eaton M112 (1.8L) moves approx 1146.2293cfm at 6500rpms.
~14.5psi on Kenne Bell 2.8L moves approx 1131.1997cfm at 6500rpms.

I would not say ~1% and ~15cfm is much more air.

 

[WildCobra]

Great write up love the info