What air filter set up is every one using.

[TomsSVX]

Originally Posted by Trevor

I would suggest that the existing filter and associated space, is the point at which a tuned length commences in accordance with the OEM design criteria.

Then that must be the design for ALL subarus, because their airboxes are all interchangeable. It was also argued that the flex joint was part of a plan for velocity when that was grossly incorrect. Who would design an intake for engines with 1/3 more displacement to have equal designs to that of the lesser (the 2.2 I am referring to). From this I can only deduce that the airbox was used simply to keep it simple and not for performance. Why would you want a brick wall in the way of fast moving air??

Tom

[Trevor]

Originally Posted by TomsSVX

Then that must be the design for ALL subarus, because their airboxes are all interchangeable. It was also argued that the flex joint was part of a plan for velocity when that was grossly incorrect. Who would design an intake for engines with 1/3 more displacement to have equal designs to that of the lesser (the 2.2 I am referring to). From this I can only deduce that the airbox was used simply to keep it simple and not for performance. Why would you want a brick wall in the way of fast moving air??

Tom

I am not about to commence an argument, my comments is one of interest.

The size, design, construction of any box surely matters naught, as I suggest that the tuned portion/length does not include any box, which in effect becomes a plenum.

[TomsSVX]

I understand and I am not arguing but merely asking your point.

I know that the airbox can act as a reducer but they usually are smooth redcutions, where as our airbox has very sharp angles and dead corners. We have been toying with the idea of molding a fiberglass reducer to fit in the stock airobx to improve it's ability to flow

Tom

[Trevor]

Originally Posted by TomsSVX

I understand and I am not arguing but merely asking your point.

I know that the airbox can act as a reducer but they usually are smooth redcutions, where as our airbox has very sharp angles and dead corners. We have been toying with the idea of molding a fiberglass reducer to fit in the stock airobx to improve it's ability to flow

Tom

Tom, as usual our ideas are in agreement and the topic is one of alternative diagnosis and therefore added interest.

[Dessertrunner]

The guage has a problem in that it is too accurate and does not read high enought for the kinds of vacuums you can expect. It does how ever have two inputs, a low and a high so it is possiable to put test point on either side of the restriction being test. In this way it ignores atmosphere.
I plan to drill in test points at various locations along the intake so as I can measure the restriction at each step.
From my reading it seems that any gain on the intake can be quickly lost if you don't improve the exhaust. I tend to think the intake on the SVX will be a problem as we have a Liberty 2.2l and it has the same airbox & filter.
Tony

[Trevor]

Originally Posted by Dessertrunner

The guage has a problem in that it is too accurate and does not read high enought for the kinds of vacuums you can expect. It does how ever have two inputs, a low and a high so it is possiable to put test point on either side of the restriction being test. In this way it ignores atmosphere.
I plan to drill in test points at various locations along the intake so as I can measure the restriction at each step.

Tony you saying that the gauge has a high and a low input relative to the scale. The specified maximum pressure of 100 would indicate that a second high connection will provide an alternative scale of times ten of the dial figures. Blow hard and test both.

This would mean that two ranges of sensitivity are provided for, but both would be against atmospheric pressure. An instrument measuring a differential in pressure as I see it, would be rather different in construction.

I sincerely hope that I am wrong and you can be sure that all is as you say.

P.S. An exhaust system working as an extractor will assist to increase the rate ot flow through the intake. However this will have no bearing on the degree of obstruction imposed at restrictive points, which is the essence of your interesting exercise.

[Dessertrunner]

Trevor the unit measures the differential vacuum between two points, the problem is that its range is only 1.5 psi. Which is to sentive. I have a single input gauge that will read up to 15 psi vacuum coming. Have I cleared that up. As regards the exhaust I have seen dyno reports of before and after intake manfolds rework and in the cases of the WRX all the power gain was at low revs. They assumed that the loss of gain at higher revs was related to the exhaust.
Tony

[YourConfused]

As I recall from past posts your exhaust is beat to hell. Do your tests now and fix your exhaust and then do these test again. Let us know what it all adds up to. Thanks for the effort and money you have expended in this quest for power/efficiency.

[Dessertrunner]

Your right about my car but the wifes is in perfect order ideal for a good test bench.

[Trevor]

Originally Posted by Dessertrunner

Trevor the unit measures the differential vacuum between two points, the problem is that its range is only 1.5 psi. Which is to sentive. I have a single input gauge that will read up to 15 psi vacuum coming. Have I cleared that up. As regards the exhaust I have seen dyno reports of before and after intake manfolds rework and in the cases of the WRX all the power gain was at low revs. They assumed that the loss of gain at higher revs was related to the exhaust.
Tony

Tony,

Sincere apologies. I have done a search and the gauge you have is exactly as you say. This type of instrument is usually centre scale and it is now clear why the one you have has ports labelled high and low. I was stupid not to have done a search before. Furthermore I would estimate that the scale is in line with your requirements. Go ahead and do some testing.

The figures which you obtain can only be considered as relative with each other and a guide as to where improvement may be possible. For any comparison in this regard, the flow rates must be equal and you should record all comparative readings within the same engine speed and load situation.

Importantly, any the measurement will vary considerably and you should be able to take measurements at an engine speed providing a pressure drop within the calibration of your existing gauge.

Yes, loss or gain in engine power output will change relative to the exhaust set up, but this does nor relate to the experiments you propose. You are testing to find points within an existing intake system, which can be identified as obstructing or causing resistance to flow. The actual figure registered at each point will be dependant on the rate/speed/volume of flow at the time of measurement. This will vary in accordance with engine RPM and load, quite independent of other factors.

I have blasted you with a lot words because what you are doing is a quite special project, which I will keep following with much interest.

May satisfaction result. Trevor.

[Dessertrunner]

One question I need to be clear on will the amount of air drawn (air Flow) in by the engine change if the engine revs are constant but the load changes?

[Trevor]

Originally Posted by Dessertrunner

One question I need to be clear on will the amount of air drawn (air Flow) in by the engine change if the engine revs are constant but the load changes?

Yes, because if the load changes, in order to keep the engine at the same RPM, a change in power output will be required. This will call for the throttle opening to be adjusted, so as to vary the density of the charge at ignition, thus altering the amount of air consumed and flowing via the intake manifold.

[Motorsport-SVX]

I run my CAI intake with our green filter on
my silver car and a green drop in in my 97...
have been for a few yrs.
We just modded our short ram and cai kits with
a new billet style maf sensor btw, think it came out
pretty nicely.

both are advantagous in their own right.

[Dessertrunner]

Trevor I think what I will do is put the car climbing the same hill at the same rev's, at the same time and see what the maxium number I get at each test points, that should work out pretty close. What would be interesting is if we took a reading at the throttle body (maxium loss) then removed the exhaust and see if the vacuum increases, which should mean the car is taking more air.
I had to purchase a second gauge that would read high enough. This one will read -100 Kpa or -15psi. If our intakes are above that we have real problems. What I have read says should aim below 8 psi, the lower the better.
Tony