Still surging after BOV...

[KATwo40]

As ya'll know, I'm workin' up a fully built KADE, but I'm currently running the old 200k mile engine into the groun with a T3/T04E @ 8psi.

During this build-up process, I've been installing various parts that will be necessary for the built setup (400whp goal) to keep the downtime at a mininum. This way, it will be simply a removal and installation, rather than removal, re-do stuff, install new stuff in the bay, install engine.

Anyhow, to the point...

Yesterday I installed a Greddy Type-R (Standard spring) BOV on the hot side, right at the intercooler. I have the spring at the softest setting (adjusting bolt barely touching the spring plate) and I can hear the valve opening a little on light pulls, but on a hard pull I can't hear it open, resulting in some NASTY compressor surge (that high pitched pppffwwhiirriirirriirrirrr).

Is this characteristic of the Type-R valve? Will it open fully on higher boost levels (12psi daily, 20psi strip) and stay open long enough to kill the surge?

Anyone with some knowledge on this valve, please let me know if I've chosen the wrong part for my application.

Thanks in advance.

[Florida240sx]

Where is your vaccum source???

[KATwo40]

The tube is pretty long, as it has to go from the driver side of the intercooler to the back of the intake manifold...that's what, about 4ft.?

I will be installing a vacuum manifold soon, so maybe I should plan on locating that near the front of the engine bay, reducin the length of that line.

What baffles me, however, is that the vacuum will open the valve on lower pressure runs, where the charge pipe pressure doesn't abruptly spike from slamming the throttle shut, which should assist the valve in opening even more.

[Florida240sx]

I have the RS from greddy and i hate it....sounds cool....from what I can hear it's the bov makign the sound but then of course their is still some harm gettign to the turbo....

[darkforcejackal]

The Greddy-R is designed for higher boost, but it should be opening regardless...so your situation does sound a little strange.

After you've double-checked your BOV vacuum (intake mani) source, i'd say try adjusting the BOV much, much tighter and slowly backing it off a bit at a time with road testing. Sounds odd to tighten it when there's surge and all but I had the same issue with Greddy-S and RS valves when vented and this did the trick.

Good luck.

[KATwo40]

I tried it with the stock setting, first, then backed it off incrementally, test driving between adjustments. It was only slightly opening at the weakest adjustment (screw off the spring plate).

One other guess is that this valve might have been supplied with the STIFF spring, rather than the SOFT, as it comes in both options.

[nissanfanatic]

The Type R is unnecessary... Type S would have been fine.

But that is why I switched from my Type S to the TurboXS RFL.

[KATwo40]

What about the Type R is unneccessary, per se? I chose the type R because the Greddy site said it was applicable for 280-450hp, which is right there where the new engine will be.

[C-Kwik]

One possibility that I can think of is if it was installed backwards.

[AZhitman]

Backwards? Tell me more, as I'm having the same issue.

[KATwo40]

You can't install it backward. The outlet is a round tube and the inlet has a flange w/ bolt holes.

I finally got it to start opening. After some monkeying, it does open, but it's VERY quiet. Just a gentle "wwwsshshhh" and no loud noise like you'd hear from an RFL.

I still have the problem of it being a delayed opening, in contrast to the surge event. Basically, it takes a little longer than it should to open after the throttle is closed, resulting in a quick surge, then the quiet "wwwshshshs" from the BOV.

I think it might be a result of the 5ft long vacuum tube leading to the BOV. Since I have it mounted right at the hot side of the FMIC, I have to use a lot of line. I will install the vacuum manifold soon and re-route some lines. If I mount the manifold in the stock battery tray area, I can discard about 2ft of tubing. I'll post the results.

[lrb_2000]

you could hook your boost gauge source to the same line as your bov to see how much vacuum there is as soon as you let off the throttle... but then again, I probably don't know what i'm talking about.

[DammitBobby]

That is why I am glad I have a HKS Type 1 BOV. It has a secondary port you hook up to the vacuum line to assist when you are not in high boost. Never had compressor surge with it.

[lrb_2000]

Maybe you could sell your current BOV for one that is proven to work well by other KA-T'ers.

[KATwo40]

I just realized the Type R also has a secondary port. DOH!!!

I'll hook that up and see how she goes.

DammitBobby:

Did you use two seperate vac. sources for each port?

Thanks again!

[lrb_2000]

I just realized the Type R also has a secondary port. DOH!!!

I'll hook that up and see how she goes.

DammitBobby:

Did you use two seperate vac. sources for each port?

Thanks again!

I doubt it matters if you use the same or different vac sources.

At least you know what's wrong now!