Dougs951

No isv on my cars. The S2 has more of a problem with it than the 951

s14kev

Your ISV was effectively deleted when the hose was squashed by the strut brace. No flow through hose = no ISV. Physically removing the valve probably helped further. Given how old they usually are it was probably poorly sealed and removing it removed a vacuum leak source. Your engine probably runs better now, at least until you start using the AC...

On a side note, what head mods have been done by Lindsey Racing? I am considering porting my own vs buying one of theirs.

On a side note #2, why are you running a vent to atmosphere BOV? Is it just to get the 'pttssch' sound? How do you get over the over fuel issue when it vents with an air flow metered car?

Dougs951S

No AC or power steering, and yes I did pick up 1" of vacuum so it must have been leaking though I have to insist my ISV was working fine before, trust me

I'm not some ricer LOL I did not do it to get the pshhh sound, you cant hear it vent over my exhaust anyway. Just did it because its an improvement in response ( in gear, not between shifts obviously because its running rich )over the old stock DV, but the REAL reason was because my new j pipe replacement does not have a provision to mount a DV where it normally sits. I will be dealing with the tuning issue shortly. with a speed density tune or a blow through MAF setup you can vent the BOV to atmos.

There IS a method to my madness I swear.

Chris White

BTW - did you know that the DV can be open when the engine is under vacuum? so it might just be sucking in some odd objects....

Dave W.

Just put a valvecover breather filter on the BOV outlet. Like this one;
http://www.summitracing.com/parts/knn-62-1170/overview/
works fine on my car since I also have a speed/density tune. Just choose a size to match your BOV outlet.

Dougs951S

No chris, I didn't know that! Is that a failure mode though? If it were open at idle wouldn't that constitute a vac leak, and same if I were to leave the port open and put a small filter on it like Dave suggested? I tested the DV it both sides were definitely air tight when I tried to apply vacuum with my mouth. Is that not a good test? This is something I've never heard before.

lart951

I got an avatar for you

Dave W.

No, it's not necessarily a failure. Some BOV's have softer springs and when combined with an engine with greater vacuum at idle the BOV might open. Sucking in dirt can obviously lead to engine wear, but it only happens at idle.

Paulyy

Lets answer a few questions here. Since i've had 3 different setups on my car from stock to speed density and maf.

The MAF and AFM (Stock) having the bov/bpv dumped to atmosphere, you'll loose response and your fuel mixtures wont be stable during idle, during shifts and deceleration.
MAP/Speed density setup, the bov can do as it wishes as there is nothing metering the air so there won't be any fuel change. You can even delete it and get the Sut Tu Tu Tu Tu noise and wont do much lol! just damage the turbo after a while.

Another thing to cover. Having the BOV open under idle is normal and doesn't cause a vacuum leak because it's before the throttle body. After the throttle body is where the vacuum is.

Dave W.

Good points. I just edited my post above to show that I have a speed/density tune, so venting the bov causes no issues.

s14kev

The BOV does not function at all when in gear. It stays shut when in gear. It should only open when the throttle is shut which occurs between shifts. Therefore the new BOV does not do anything except give poor driveability due to overfueling when it opens. If anything your driveability is worse since to run a BOV that vents to atmosphere in an airflow metered car usually requires high BOV spring tension to minimize the amount of time that it opens to prevent stalling from overfueling.

Still very interested in the modifications to your cylinder head. What stage Lindsey racing head do you have (stage 1, 2, 3?) and what are your thoughts? I'm trying to get as much feedback as possible on people who have used their modified cylinder heads since I'm on the fence about purchasing one or porting my own.

Paulyy

I have a CEP head, You will notice some what of a power increase. It's very hard for me to tell you how much because i did get a cam too at the same time.
So my torque curve is more linear than peak then huge drop off.

IMO if you work the head, you may as well get larger valves too.