Maggies "lose" 2 psi of boost with Long Tubes?

[hflores3]

Had an interesting chat with a shop who rather strongly suggests that 2 psi of boost is lost when using long-tube headers. Has to do with header efficiency and the loss of back pressure. You gents heard of anything similar?
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Henry, you lost 2 psi of boost when you added the headers, now with your installing one of our 3.10" TVS pulleys you will gain that 2 psi of boost back for your G8. Hope this helps.

Reason 100% of all Vehicles, be it Foreign or Domestic running Forced Air Induction ( Turbo or Supercharged ) you will always loose the 2 psi minimum, because the Lack of Back Pressure you just took out of the horsepower equation! Hope this helps.
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PLEASE NOTE: If running Long-Tube Headers, you will loose 2 PSI of Boost and to gain that back, choose a pulley 2 sizes smaller!

- 3.60" pulley: expect 2.0 psi. more boost over stock pulley -Total boost 8.0 psi
- 3.40" pulley: expect 4.0 psi. more boost over stock pulley -Total boost 10.0 psi
- 3.20" pulley: expect 6.0 psi. more boost over stock pulley -Total boost 12.0 psi
- 3.10" pulley: expect 7.0 psi. more boost over stock pulley -Total boost 13.0 psi
- 3.00" pulley: expect 8.0 psi. more boost over stock pulley -Total boost 14.0 psi
- 2.90" pulley: expect 9.0 psi. more boost over stock pulley -Total boost 15.0 psi
- 2.80" pulley: expect 10.0 psi. more boost over stock pulley -Total boost 16.0 psi
- 2.70" pulley: expect 11.0 psi. more boost over stock pulley -Total boost 17.0 psi
http://www.southfloridapulleyhq.com/

[BlueJacket]

I'm no expert but that sounds about right to me.

[BMR Sales]

Yeah it is true, I am not sure if its that much but you have to remember boost PSI is just a reference to overall restriction, which is which you "lose" boost after a header install. Headers gain power by making the exhaust less restrictive.

[norm8332]

With the stock cam mine went from 10.5 psi to about 9.5 psi with the headers+cats and catback.

[99-LS1-SS]

You do lose boost but you don't lose power. Boost is a measure of back pressure and when you can make the air flowing through the engine more efficient then you gain more with less. You "lose" boost when you port the heads too but you still keep or gain the same power.

[GRRRR8]

This is normal.

[Patrick G]

It's really quite simple if you think about it...

The blower is what dictates the amount of airflow going into the motor. More airflow typically equals more power. Boost is a measure of resistance, not power. More boost equals more resistance, not more power.

Headers reduce pumping losses and allow the combustion to more easily escape the chamber. Reduced pumping losses reduce restriction. Reduced restriction equals lower boost. This is a good thing. But since the blower dictates the airflow/power your motor makes, you will now be able to pulley-up to allow more airflow into the motor at the old boost level.

Sure, you'll gain some power from the reduced pumping losses of headers alone, but to really make them shine, you need to increase blower speed to see their ultimate gains.

[hflores3]

Sounds like there is validity to his claim of "loss."

Now then, is 2 psi an overstatement or is 1 psi about right and closer to the norm?

Damn interesting stuff!

[Patrick G]

Sounds like there is validity to his claim of "loss."

Now then, is 2 psi an overstatement or is 1 psi about right and closer to the norm?

Damn interesting stuff!Just don't correlate boost loss with power loss. Even with the loss in boost, headers will gain you power in a blower application (even without pulley changes).

[Ktlplxm]

Dont think of boost as anything important (it isn't an absolute just a measuring stick), you should look at airflow and cfm. If you take a supercharger making 10 lbs on a 6.0 and throw it on a 7.0 you will lose boost only because the total area you are trying to fill is less. You dont lose power, you just make it more efficient

[christiancoach]

Just don't correlate boost loss with power loss. Even with the loss in boost, headers will gain you power in a blower application (even without pulley changes).

....and running less boost is easier on the internals. So really by adding headers you should have kept the same or gained horsepower, and lowered the wear and tear on your motor.
Of course, as others have mentioned, change that pulley and see the overall results!