i would like to pass this along, because i wondered about it for a while:

whith the stock intake there is a loss of 4 kpa over the rev range. with the box removed there is a loss of 4 kpa (zip tie mod). with the filter removed also there is a loss of 4 kpa.

this is measured with efilive. while i believe in measurement errors, this should be clear anyways.

btw, everything is stock otherwise.

 

Don't understand quite what you mean---
Any N/A engine should always read 100 KPA at WOT- Occasionally you may get a N/A engine to read slightly over 100KPA ---quite common with a FAST intake--But very minimal like 103 KPA -- rather meaningless or a slight error in the MAP sensor -Anything over that means the intake manifold has gone beyond atmospheric pressure and has boost (turbo or SC)
I really don't think you can read more or less airflow using a KPA or MAP reading
Even if KPA is measured during P/T I think those readings are meaningless and don't reflect More or Less airflow
When I want to see if mods are adding HP by increasing airflow I measure the airflow using PIDS that read "Cylinder Air in grams per cyl." and the "MAF reading in HZ" If those are increasing that equals more airflow equaling more HP
Another way to quickly see if there is more or less airflow at P/T is to look at your LTFT's after a mod.---Assuming that you have all your LTFT's at "0" before----If you get a positive new LTFT that means the AFR is leaner due to more airflow than before the mod and the ECM is adding fuel to compensate
If you get a negative LTFT then you are getting less airflow and the ECM is removing fuel to compensate for the lower amount of airflow

 

maybe i should have explained better.

with the engine off the map shows 96 kpa. at 3000 rpm and wot it shows 96 kpa. at 5500 rpm it shows 92 kpa. with and without the weird looking intake box or filter. so my conclusion is, that they are no restriction, at least not one that matters.

as to the maf, its weird because it was lowest without the filter, but its fluctuating quite a bit, so thats probably meaningless.

 

With the engine OFF and key ON any engine should show atmospheric pressure which is 100 KPA----If your engine shows 96 KPA then your MAP sensor is reading incorrectly
Unless you are at an altitude above 4000'--you then may get a KPA reading less than 100 KPA as the air pressure would be somewhat less than 14.6 PSI or 100 KPA

 

I haven't done any sort of filter/no filter tests, but I see a little pressure drop at high rpm at WOT also.

 

To note, there is a 3 kPa drop per 1000 ft of altitude. Sea Level will be about 101-103. In Denver you could actually be seeing map in the 80's

Ed M

 

Don't know if the ECM will make a change if under 4000' altitude---I know on most GM ECM's that the change in MAP due to elevation does not happen below 4000'

 

Not sure about that, point was you may not see 100 kPa with KOEO unless close to sea level. The PCM will use the current MAP readings for all its SD and misc calculations. It is reading absolute pressure in the intake manifold.

Any further reductions from the KOEO readings will be a result of restrictions/inefficiencies in the airflow system allowing some small level of vacuum to appear.

Ed M