gze question for the pros

[ae86driftmaster]

i found a Cusco Air Bypass valve....is it worth getting? i know these are very hard to get basically rare in the US .......suppose to work well avoiding doing the abv mod and easier on clutch engagement....they sold for over $400 new....
i have a ae101 w/NST 180mm pulleys still in the process of getting the motor started
before rebuild it was @ 10psi on stock pulley

or should i just get rid of the abv completely ?

i managed to find the old ad ...but trying to find info on this is difficult ..if anyone knowd anything on this item please share

[Lauren]

Pouring your money down the drain IMO. Better off just to remove the ABV completely.

Or just block it off.

I had a custom outlet made up for mine:



In summary just get rid of the ABV. The VSV mod is crap and still leaks boost. Taking the ABV out of the equation is the only way really. Easiest way is simply to plug the SC outlet to ABV with something.

[Ivan141]

I'm not an expert, but if all it does is bypass air to vent pressure spikes, you could just use a 20 dollar bosch valve instead and save some money. There is the matter of fitment though, that flange looks awkward.

[Lauren]

You don't need to bypass air. Just run it all through the SC, it's not a problem.

A round bit of metal of a size that can form a plug can be put inside the pipe between the SC outlet and ABV. Cost is nothing really.

[ae86driftmaster]

i thought of removing the abv ...but i always feared that would mess up the idle?

this is the info i got
The adjustable abv allows you to set your maximum boost level. This can be useful for a number of purposes, such as, a) alleviating stress on your sc by avoiding high temp boost levels caused by overheating the sc when it is run for long continuous levels of boost, b) test/dyno purposes, c) maintaining boost limits for engine longevity/reliability, etc.

Using the adjustable abv also allows you to avoid having to run the normal vacuum hose bypass in order to get the maximum boost when adding an overdrive crank/sc pulley. This can simplify connection of a boost guage, and probably give you more consistent boost readings when not having to share one port with so many items. It also allows your sc clutch to operate in a completely normal manner, in that it will allow the sc to slightly ramp up rotational speed before engagement of the sc slutch, thus saving some wear and tear on the sc clutch, and thus providing better clutch engagement. You could also set the boost at various levels for things such as smog testing, or when having to leave the vehicle somewhere such as a repair shop or valet service when you don't want the car being abused behind your back, lol.

[Lauren]

Seriously, it has no effect on idle. Myself and a number of my friends took the ABV out of the equation with no ill effects.

Think that stuff you posted is just sales pitch type stuff in all honesty.

[ae86driftmaster]

im not denying your guys performance with out the abv im sure it works i was going to do the same thing...but i started thinking why would they make them if they didnt have some kind of benefit? im sure they knew about removing the abv mod.....
cusco make great products and they are not the only ones who made the abv for the gze hks and a few others did

me i like the fact you can adjust the boost levels

i will do this ....when the car is finished and ready for tuning i will try both ways and see what is out come

[Lauren]

Do it and report back, nothing wrong with that.

Boost levels are dependent upon the intake charge temp. Generally I found that the car was quickest at an indicated 11psi. On the later spec GZE with DLI, you get boost cut at 1bar, so you can't really go over that. The only time I had that was through really bad heatsoak which knocks up the boost pressure but reduces the power.

The car shot 2 foot flames out of the exhaust at 145mph (so my other half following me told me!).

The ABV merely vents off boost pressure, but if you are running a big pulley it effectively becomes redundant. I guess with a variable pressure ABV you can set it at a given pressure to vent, but in all honesty, the only time that is likely to happen is if you get heatsoak. So, just using a boost gauge you can see what it's doing boost wise and you'll see that with a big pulley providing you are well intercooled enough the boost will stay at a steady level, so no need for an ABV IYSWIM.

If any of you guys with SC's want access to some expertise on SC's then let me know as between myself and my fiance we run an AW11 SC forum which has been going since 05, though we had SC's way before that. Most of our close friends had SC's as well, so there's a lot of knowledge on there. PM me if interested.

[Ivan141]

What this type of valve does for turbo'd engines is make sure the charger can keep spinning without having to work against the pressure peak in the inlet once you close the throttle (assuming throttle is behind the charger).
This avoids the turbine slowing down on every shift and is easier on the pressure plumbing.
I suppose it is less of a problem on a more mechanical supercharger, but I'm sure it is harder for the charger to try to add pressure to an already excessively pressurized inlet.
That being said, you only need to bleed off spikes, dont use it as a boost controller, it's not meant to work like that, the pulley on an SC mostly dictates the on-throttle boost levels I presume.
As I said, just slap on a cheap bosch valve that will work at the pressure spike level you want to get rid off. They have a few different types and ranges.

[Lauren]

Doesn't work like that, the throttle is before, so not like a turbo at all. SC is after the throttle, so there is no issue of what you speak of.

SC is driven from the crank and you want to get all the boost pressure into the inlet. There are no boost spikes to speak of. Having an ABV means you might lose some of that pressure. If you are running more than stock boost and have a big pulley, junk the ABV, weld it up etc.

There is no downside to doing this other than you ensure you get maximum boost pressure in the inlet.

I expect the reason Cusco make such a device is purely because people will buy it, when really you don't need an ABV at all.