My bypass valve (used, whole Vortech kit is used) leaks vacuum.
So, I used a barb on the up-pipe (plastic) that the previous owner apparently had been using as the vacuum signal source for the bypass valve.

This solves my vacuum leak problem, but leaves me with some questions:

1. the Vortech instructions say to plumb the vac signal for the bypass directly to MANIFOLD vacuum, and this makes sense... but if this is true, the bypass valve has to hold vacuum like the FMU and EGR (for instance)... is this correct?

2. my best guess guess is the blower will cause the up-pipe to pressurize, and thus close the bypass valve when I start my engine, and it will remain closed... meaning it is worthless the way I have it plumbed... if I'm right... does anybody know?

3. If the bypass valve is indeed closed all the time, would this cause "blower surge" at about 2000RPM? I think I have that symptom...

4. Did early kits from Paxton and Vortech not get by w/out the bypass valve?

5. If you are not making proper use of the bypass valve, is the effect a hit on economy in form of parasitic engine drag, and blower surge?

Sorry for such goofy details, but think this through and tell me if I'm right or wrong... I am trying to decide whether or not I HAVE to shell out the money to Vortech for a new valve which very -well may start leaking on me again (this kit is about 2 years old, BTW).


Terry

BTW, engine is totally stock even to the manifolds, I have a MSD coil, the Vortech kit with Crane ignition included (with variable boost retard), and a cat-back FlowMaster.
My cam, rocker ratio, etc. it completely stock, and I checked all my vacuum leak potentials (FMU, EGR, 2bar MAP for the Crane, my boost gauge line) and they are rock-solid and hold 20inHg steadily.

 

The bypass needs to be run off the manifold. Pretty much anytime you don't see boost on the guage, the bypass will be open. And boost in the manifold will close it.

It sounds worthless they way you have it now, Because:

The main idea is when you let off the gas at 6k rpm/ X#'s of boost, the throttle body slams shut. Your supercharger is still spinning the same speed, and pumping the same amount of air, and it has nowhere to go. THIS is what causes compressor surge. The bypass is supposed to open at this time, to relieve that extra pressure. (they way you have it now, it will be closed)

Also, You will have vacuum in the manifold at idle, so the bypass will be open at idle. It will keep you from cramming in more air than the motor needs at idle, This will make it so there is less load on the SC.

I'm don't think the early kits came with a bypass. They didn't feel it was ablsolutely necessary with a low boost setup.

I'd just vacuum the bypass of the intake, and see if that solves some problems before you order a new one.

 

Thanks for the reply!

Yep, sounds like my bypass is not gonna help at all the way it is now.

Thanks for the explanation on blower surge. I understand it much better now.

My bypass was originally plumbed to the manifold.
I changed this last night.
The reason I changed it is I tested the bypass (and FMU, EGR, Crane 2bar MAP, and boost gauge) with a manual vacuum pump (hand pump used for testing things like EGR and bleeding brakes, etc).
The bypass won't hold any vacuum.
It is damaged or defective.
So, I have no choice but to both replace and re-plumb it BACK to the manifold for proper operation.
In the interim, I at least have solved my vacuum leak and still can use the blower.
I ordered a new bypass valve today.
Vortech gave me the Bosch part number, and I saved about $30 (paying $36 vs. $62 if ordered from Vortech) by ordering it from a local VW import shop.
It is not a Vortech-specific item, luckily.
Should get it tomorrow, and I'll then start working with PCMFORLESS again to re-tune.
We've been (probably) fighting this problem for about 3 months in tuning my car.
I hate to have waited so long to get under the hood and check it out... I knew by the 10inHg erroneous reading my boost gauge gave at idle that something was afoot (matter of fact, when I first plumbed it all up, I had a proper 20inHg at idle... this means when I first put the blower on, the used bypass valve was working fine).
So, things like this happen I guess.

Thanks again for the reassurance... feels good to know, and the blowe surge explanation was very insightful.

Terry

 

The stock Vortech blowoff valve is junk. They say it will hold 10 psi, but I was able to make mine leak by blowing into it (<1 psi). You can get many others (mine is a stock Mitsubishi Eclipse unit) for much cheaper that actually don't leak boost.

Mike

 

Thanks for the heads-up Mike.

I already ordered the new bypass, so wait and see how it does (too late to send it back).

If it fails prematurely, I'll be talking to Mitsu about one.

Vortech is surprising in the quality of their blower, but the up-pipe (plastic) and the inlet pipe for the blower (the corrugated flex tube) were surprisingly chinsy for such a high dollar kit.

And the instruction flat out LIE when they tell you the install can be done in 12 hours.
That is IF you don't replace injectors, don't mount any gauges or the Crane retard dial, and don't upgrade fuel pumps (dropping the tank down sucks on an F-Body GenIV).
And that 12 hour number is in a comfortable shop with a lift and at least 1 other person.

Then, take me, I bought a used kit... had to get the instructions off the 'net, find all the missing little items like screws, washers, compression fittings, wiring, etc.

And last but not least while I'm whining about Vortech, I found it absolutely impossible to mount my Crane box as they show.
I have a huge factory wiring bundle in that area, and there is no freakin' way I could've mounted the box flat.
I had to mount if on the "back" side of the radiator support by only using 3 of 4 screws, which I drilled and tapped the radiator support to use (and used pieces of heater hose as rubber "feet" to even up the mount). And then I had to cut the smog pump relocating mount bracket to clear that huge wiring bundle.

Oh well, anybody that has put one on has gone through similar crap.

Guess overall the Vortech kit is "do-able", which is better than probably some stuff on the market (we've all heard the horror stories).

Other items like the T-Rex instructions were not quite right, in that if you reverse just one of the fittings combos, you can then easily remove the T-Rex and hook the stock line right back up to itself if needed (I took the time to do this just in case I ever sell my blower kit for any reason, or have to replace a failed T-Rex, etc).

I've also de-tuned the knock sensor a bit, and am presently working on alky injection (home-brewed using the washer reservoir for the windshield wash and the factory in-tank fuel pump).

This has turned out to be a 6month project for me to get it the way I want it (and on a budget).

In all this mess, I have to say (again!) how much I appreciate and like PCMFORLESS.COM for tuning my car.
Al has me on the 26th iteration now, and is relentless and always willing to work with me, even though I wore out my "buyer's rights" some time ago to continued service.


Terry

 

It took me and a friend about 12 hours to install a kit on my '95 -- without the retard box and the T-Rex. And we'd recently installed a kit on his '02 GT so we were familiar with the basic order of things. So, I agree that the 12 hours is a LIE.

You won't know when the stock bypass valve is leaking. It just doesn't make the power and boost that it should. For instance, instead of making 9 psi, it might make 8.

Mike

 

Guess I ought to say that my bypass valve was leaking, but not in its ability to closed...

The valve was not able to hold vacuum on the actuator side, that is, the vacuum line going to it was basically seeing a leak path through the valve to the up-pipe from the compressor.

The result, was that the valve was never "opened" by vacuum, and remained in a closed state... thus, my blower pressure and max boost were fine, but I had blower surge.

I replaced the critter, and the car is baby smooth to drive again.
But when I romp the gas, it has a delay and then hits hard.
I figure this is the result of having tuned the car around the darn bypass valve being stuck in the "boost" position all this time.

So, I have contacted PCMFORLESS.COM and we're gonna collect some data, and then re-tune.

This thing goes out again, I'm going to a Mitsu dealership

Terry