Club 80-90 Forums

Paul_Van_Denton wrote:what was wrong with the charge cooler setup? lots of lag?

southernsparky wrote:Lloyd, I've read lots about the pressure differences etc, is there any real evidence to support it?
I want to change mine which will be like jaegers I guess, but if there's a proven better option then maybe I'll change the plan.

Here are some of the questions (not necessarily in order) that I asked myself before and during the tests with the first one being stated above: (remember, when I say that a pressure is higher in a particular area, this would result in a lower number on the chart because the chart represents the differential between the higher test area and the lower test area)

Question:
Even before I started the tests, I knew that a scoop on the pillar vent would help force air into the plenum, but how would this compare to the airflow in the "ideal" location at the front of the van?

Answer:
Not very well actually…at least not under my limited test procedures. While adding the scoop significantly increased the pressure in the plenum, the results are still a long way from the pressure at the front of the van. I'm sure that improvements to the scoop design/location could improve this even more, but I don't think that a single side vent/plenum can ever produce enough pressure to be considered equal to that of the front of the van. However, if the two plenums were to be combined into one plenum, maybe then we might have something. Tying the two plenums together and venting them out the back of the van seems to me to be a great way to get the kind of airflow needed to produce good results when using an air/air intercooler, albeit a bunch of work.

Question:
What is the air doing at the leading edge of the louvers as it enters the vent without a scoop?

Answer:
The air pressure in that area is comparatively pretty low. I was actually a little surprised at just how low the pressure was in this area.

Question:
What is the air doing down inside the plenum with the opening at the engine end open to the engine compartment?

Answer:
The air pressure down inside the plenum under these conditions is somewhat higher than out at the opening. While it doesn't show it on the chart, the readings at the bottom of the unsealed plenum were ever so slightly higher than at 3" down from the top. I didn’t record them because it didn’t seem significant enough.

Question:
How can the pressure at the bottom of the plenum near the taillight area be higher than at the top where the air is supposed to come in?

Answer:
Testing the air pressure in the engine compartment proved that there is higher pressure in that area (however slight it may be) than there is in the plenum. This means that in an unsealed plenum, the air coming into the engine compartment is at a higher pressure and appears to be forcing it's way into and up the plenum.

Question:
Does adding a scoop to an unsealed plenum create more pressure in the bottom of plenum in the area where an intercooler or oil cooler would be mounted?

Answer:
Yes it does! The addition of the scoop increases the pressure in the bottom of the unsealed plenum to just a hair over that of the engine compartment itself. However, the tiny increase in pressure is no where near what I would consider adequate to provide any significant amount of airflow through this area.

Question:
So what if we sealed up this plenum to separate it from the affects of the pressure in the engine compartment?

Answer:
With no scoop added, the louvers in place and the plenum sealed from the engine compartment but with the exception of the snorkel to the airbox still installed, pressure in the bottom of the plenum in front of the taillight showed a fairly large increase.

With a scoop added to the above scenario and all other things being the same, the pressure increased to it’s highest recorded level.
[/color]With no scoop and the louvers removed from the vent opening, the pressure dropped lower than it had been with the louvers installed.

With a scoop added and the louvers removed from the vent opening, the pressure was lower than with the scoop and the louvers but still significantly higher than just he louvers and no scoop.

To clarify, removing the louvered panel from the opening of the vent reduced the pressure in the plenum under all conditions tested. Adding the scoop to the vent opening increased the pressure under all conditions. Sealing the plenum from the engine compartment and adding a scoop made the most pressure in the plenum for the given tests.