Yep, I actually have two Tees but for purposes of explaining this mod, I simplified it.

Yep.
Oops! I wrote vacuum where I should have written boost. I will edit my post to read: "I may try a one-way check valve in the long vacuum line to prevent the bypass diaphragm from seeing boost, but I'm not sure if this is needed."

 

This looks good - with the diagrams it's very obvious. Please keep us up to date on and changes, perceived or measured (throttle response, MPG, bypass valve imploding ) :smile: Thanks for sharing all your info!!

 

Subjectively, I just can't get over how nice it is to be able to accelerate smoothly at any pedal position and at any boost gauge reading. I guess I had trained myself to not use the 0-5 psi range for any steady-state acceleration, to avoid the unstable zone. Now that it's useable, I sometimes pick a boost/vacuum reading on my gauge and just move the needle there with my right foot.

When the engine is into the boost, letting off quickly does cause an increase in engine-braking at first, but then as soon as the bypass valve opens, a fraction of a second later, that increase disappears. The net result is a more pronounced jerk when closing the throttle quickly (my MCS was never smooth while doing this). Stiffer motor mounts may help alleviate this sensation by controlling engine movement better.

 

maybe you should patent it...becauses you can?

 

How bad was your yo yo problem? Do you think all MCS would benefit from this? Especially if we aren't noticing anything (are we used to it?).

Paul

 

I have felt for a long time that my bypass valve operated in a inconsistant manner. This inconsistancy is made up for by my right foot as you say, you just get used to the way the car responds and compensate.
This post has convinced me! I need a boost/vacuum gage to install while doing this Mod. if the results continue to be positive I.E. gas mileage doesn't suffer to much.
Thanks for your reply and Very nice diagrams.

 

FWIW, here is how mine is currently routed, incorporating the boost gauge. I had already installed the boost gauge and run its vacuum line long before I tried the VGS, so I could clean up the routing if I did it over again. Anyway, here's how mine is currently laid out:

 

We just got dumped with close to a foot of snow. The VGS makes it much easier to modulate the throttle to control wheelspin, although nothing can make the "all-season" 185/65-15 Conti's perform well in this fourth season.

So far, so good.

 

It looks like you just sourced the vaccum from the intercooler exit/manifold entrance to the manifold dead-end. The BPV sees boost with the stock setup, you just changed the location of the source, not the method. The longer line/different location is something I theorized would work to help reduce feedback in The Yo-Yo Chronicles; glad to see someone try it and see it work.

 

Nope. I tried a longer hose in the stock location first and it had no effect. The vacuum upstream of the supercharger is different from the vacuum in the manifold. Read over this thread and you will see what I mean. I'd be happy to send you my data showing both locations and how they differ.

 

Looking at Andy's "artistic" rendition of the stock vacuum lines, Im not sure I understand how the stock setup sees boost if all of its vacuum connections are pre supercharger?

 

would this set-up of andy's be a problem with the ryephix stiffer bypass spring or would the stock spring be needed to use andy's set-up?

 

Go back to OEM spring and use Andy's method IMHO.

 

I'd say try both. I haven't driven or done any testing with Ryan's spring. From his testing, it looks like a VGS/Ryephix#2 would have the bypass closed most of the time, since the spring by itself only allows the valve to open halfway at 23-in Hg. It may end up being no different than Ryephix#1 in practice.

 

This thread has been returned to circulation. Please keep the discussion on the topic at hand and within site posting guidelines. Thanks!

Mark

 

Good stuff

 

Any measured affect on gas mileage yet?

 

I was curious to see if this mod would affect the drivability on my car. I have a problem in the light throttle and the best way I can describe it is it feels like a flatspot similar to the oldschool carburated cars.

I followed the directions and re routed the vac line and plugged the original vac port. I was surprised how much smoother it is, I still have the flatspot somewhat but its much much easier to work around now, most of the low speed thorottle bouncing around is gone.

Let me tell you if you dont have tiny little hands getting the vac line on the port under the runner is a PAIN!! but it can definatly be done and I would recomend the car being 100% cooled off or you WILL burn your hands.

Thanks for posting the info it definatly helps drivability !

 

My always-innacurate OBC is reporting mid-20's for my around-town driving, just as it always has. I haven't gone through much gas yet, so no real numbers.

Using ryephile's numbers (" My new spring only allows about 50% opening of the valve at maximum engine braking (about 23 in-Hg), and full closed at about 10 in-Hg). This differs from stock dramatically (full open at 15 in-Hg and full closed at about 1 in-Hg). ") I calculated the percentage of valve opening for 3 separate drives, with varying amounts of traffic, acceleration, etc. Using the logged upstream and downstream MAP data, I averaged the calculated % bypass opening during each run for each method, stock, Rye#2, and VGS. I also calculated the percentage of the time that the bypass was fully closed during each run for each method, stock, Rye#2, and VGS. The distinction is that Rye#2 never fully opens, so it skews the average throttle opening downwards. Keep in mind, the MAP readings are MEASURED, but all of the other info is CALCULATED based on Rye's figures.

Run1: Work to home for lunch, moderate acceleration.

%open:
stock: 89.7%
rye#2: 15.3%
vgs: 84.3%

% fully closed:
stock: 1.4%
rye#2: 19.4%
vgs: 5.6%

From the above, it looks like the VGS behaves much more like stock than it does like the Ryephix#2.

Run2: Home to work, more aggressive acceleration:

%open:
stock: 91.7%
rye#2: 26.7%
vgs: 76.7%

% fully closed:
stock: 1.3%
rye#2: 12.6%
vgs: 13.9%

The above run was interesting, I was surprised to see the VGS fully closed MORE often than the Ryephix#2. I looked up through the data and sure enough, there were instances where upstream MAP was, say, 591 mbar and the downstream MAP was, say, 1135 mbar. With those and similar conditions, stock would be open 81.7%, Ryephix#2 would be open 2.7%, and the VGS would be completely closed.

Run3: Work to home, mixed driving

%open:
stock: 96.0%
rye#2: 29.1%
vgs: 87.0%

% fully closed:
stock: 0.9%
rye#2: 5.9%
vgs: 5.5%

Remember, the above is merely the theoretical bypass opening based on my logged MAP data, coupled with Ryephile's findings about vacuum and bypass valve opening.

 

Thanks for all of the testing Andy

 

I did another theoretical test with my data. I looked at the conditions under which the bypass valve would be 100% OPEN. Here it is, combined with my earlier data:

Run1: Work to home for lunch, moderate acceleration.

average % opening of valve:
stock: 89.7%
rye#2: 15.3%
vgs: 84.3%

% of time valve is fully closed:
stock: 1.4%
rye#2: 19.4%
vgs: 5.6%

% of time valve is fully open:
stock: 70.5%
rye#2: 0%
vgs: 65.3%

From the above, it looks like the VGS behaves much more like stock than it does like the Ryephix#2.

Run2: Home to work, more aggressive acceleration:

average % opening of valve:
stock: 91.7%
rye#2: 26.7%
vgs: 76.7%

% of time valve is fully closed:
stock: 1.3%
rye#2: 12.6%
vgs: 13.9%

% of time valve is fully open:
stock: 81.7%
rye#2: 0%
vgs: 65.9%

The above run was interesting, I was surprised to see the VGS fully closed MORE often than the Ryephix#2. I looked up through the data and sure enough, there were instances where upstream MAP was, say, 591 mbar and the downstream MAP was, say, 1135 mbar. With those and similar conditions, stock would be open 81.7%, Ryephix#2 would be open 2.7%, and the VGS would be completely closed.

Run3: Work to home, mixed driving

average % opening of valve:
stock: 96.0%
rye#2: 29.1%
vgs: 87.0%

% of time valve is fully closed:
stock: 0.9%
rye#2: 5.9%
vgs: 5.5%

% of time valve is fully open:
stock: 91.0%
rye#2: 0%
vgs: 78.7%

Remember, the above is merely the theoretical bypass opening based on my logged MAP data, coupled with Ryephile's findings about vacuum and bypass valve opening.

 

I attached my vacuum hose where the red circle is as I misinterpreted the drawing and didn't have the photo handy at the time.

Any problem with hooking it there instead?

 

Is that also a vacuum nipple on the intake manifold? Shouldn't be a problem if it is. Have you driven the car yet with the VGS in place?

 

Actually I pulled the plastic hose loose from the rubber nipple and inserted the tee there. After that, it's connected like your diagram.

I've attached a couple of pics showing how I have it routed.

The car drives fine and there's no noticeable yo-yo - which is a BIG change from box-stock.





Sorry for the picture quality. It's dark and I was juggling a digi-cam and a flashlight and trying to get a picture of the right thing...

 

Vacuum connection CoryB used for his vacuum source.
Andy, any more feedback on performance or gas mileage?