Is there such a thing as...

[FalconGTHO]

too small of or not enough blow off valve size? Applies to a D1sc application.

 

[KenB]

Yes definitely. It shouldn't hurt anything being too small but will really effect driving if it's too small. When you come off boost if it can't relieve the pressure it has to go somewhere. I've seen the air filter blow off a procharger. Also, hanging idle following closed throttle after boost etc.

 

[TheKurgan]

I think the bigger the better. The faster you can get rid of that unused air, the less compressor surge.

 

[19COBRA93]

I've been fighting a balance of noise and pressure relief with my F1C/setup. That big blower moves a ton of air, so I've got a couple valves on it to help relieve it when off the throttle. One of them is the standard stage II Procharger valve with the little filter and it's not big enough to handle it by itself. So I also have a 50mm BOV on it that's adjustable. With the 50mm loosened up so it opens all the way when I let off the car sounds like a damn street sweeper (likely louder than a street sweeper). I hate it. It works the best, but I hate it. If I tighten up the valve so it only opens partially under higher boost, I get hanging idle and slight compressor surge in certain situations. But the car is reasonably quiet at part throttle that way, and is more pleasant to drive (it's a street car after all, not a race car).

To answer your question, yes you can have too small/not enough blow off valve. To know that, as mentioned, you'll have some compressor surge at high RPM when you let off, and you'll get the sticking idle. Which basically is, when you let off at 6500 and the car doesn't decelerate like it should. It sort of wants to keep going for a moment. If that makes sense. It's kind of a scary thing.

This first video is my car, and when I let off you can hear an echoing "chirp". That is compressor surge. At this event, my valves were responding very slowly. I later found a cracked vacuum T as the cause. A too small of a valve will show similar results. -Side note, this video was shot using the 'iPhone under the passenger headrest' trick.



In this second video, also my car, when I let off at the end, all you hear is a "whoosh". That is a BOV functioning perfectly. That dyno run was about 6500 rpm and 14lbs.

 

[KenB]

I've been fighting a balance of noise and pressure relief with my F1C/setup. That big blower moves a ton of air, so I've got a couple valves on it to help relieve it when off the throttle. One of them is the standard stage II Procharger valve with the little filter and it's not big enough to handle it by itself. So I also have a 50mm BOV on it that's adjustable. With the 50mm loosened up so it opens all the way when I let off the car sounds like a damn street sweeper (likely louder than a street sweeper). I hate it. It works the best, but I hate it. If I tighten up the valve so it only opens partially under higher boost, I get hanging idle and slight compressor surge in certain situations. But the car is reasonably quiet at part throttle that way, and is more pleasant to drive (it's a street car after all, not a race car).

Exactly! The main reason people don't go bigger is sound. The big ones are really loud and annoying to many people. On my car I'm going to try and use the TIAL bypass valve and feed that into a box that vents to air. The idea is the box will work like a muffler.

 

[Tre06GTP1SC]

Thats what mine "used" to sound like when I had the P1 and the mondo bypass. Upgraded to a D1 and the bypass would make a fluttering sound. This would happen even if I wasn't in full boost. (My car wasn't tuned)

Now that it is getting tuned the inlet pipe keeps getting blown off the TB, and this is with the T-Bolt clamps on it.

The thinking is that the bypass isn't big enough. For reference its a D1SC with a 3.4 pulley and custom 3" piping throughout.

 

[19COBRA93]

Thats what mine "used" to sound like when I had the P1 and the mondo bypass. Upgraded to a D1 and the bypass would make a fluttering sound. This would happen even if I wasn't in full boost. (My car wasn't tuned)

Now that it is getting tuned the inlet pipe keeps getting blown off the TB, and this is with the T-Bolt clamps on it.

The thinking is that the bypass isn't big enough. For reference its a D1SC with a 3.4 pulley and custom 3" piping throughout.

You're moving a lot of air with a D1 and 3.4" pulley. Fluttering is definitely a lack of flow through the valve. I would think the Mondo would keep up though. Make sure it's opening all the way, make sure it's got a good strong vacuum source, and make sure there are no flow restrictions at the valve mounting point, or valve exit point (dump to atmosphere or no?)

 

[Tre06GTP1SC]

yeah it dumps to atmosphere. The valve has been checked and it opens all the way, also the vacuum source has been checked and determined to be adequate. The only flow restriction I see that could be a concern is that the valve is mounted in an elbow as it turns into the inter-cooler.

 

[FalconGTHO]

You're moving a lot of air with a D1 and 3.4" pulley. Fluttering is definitely a lack of flow through the valve. I would think the Mondo would keep up though. Make sure it's opening all the way, make sure it's got a good strong vacuum source, and make sure there are no flow restrictions at the valve mounting point, or valve exit point (dump to atmosphere or no?)

As Tre said, yes, all checked. Shop redid the vacumm source earlier at my suggestion. We gauged it yesterday, signal is in the mid to high teens in inches and the valve itself was checked off the car with a hand pump and comes open somewhere around three inches, fully open by 12.

As engine speed increases the BOV outlet is blowing like a freakin hurricane, like leaf blower speed but through a small "Shop Vac" nozzle size, its insane. Shop THOUGHT the problem originally was just a weak worm gear clamp, replaced with a T bolt, things were fine, till yesterday. Popped off again and the brainstorm was, "Youre gonna need a bigger BOV" to paraphrase Chief Brody. I said, "Well, wouldnt two be better than just one big one?"

HOWEVER, the inlet tube is, and was before, popping off NOT at snap closed throttle off boost, but at 5600?/6100 rpm with just partial throttle, thats the thing. So we want to make sure that this popping off problem is caused by the BOV even though its not under conditions the BOV would necessarily function at.

This is what Tre has now:

I say to get another one like it. 8D204-010. What say you, members of forurm brain trust?

And yes, with the cars first few runs (not full pulls) on the dyno there was "run on" but the tuner figured that out within the existing tune. But, yes, there is that "stuttering" sound (IF the inlet stays on) when the throttle closes. Being the novice I am, even to me that didnt sound right and I asked about it early on if "all BOVs are created equal" and shouldnt it just be one big "pooooshhhh" sound.

 

[Twinscrewgt]

That mondo may not be enough. I've always ran at least a 50mm bov. My current setup has the standard stage 2 bypass and a 50mm bov just for a reference.

 

[TheKurgan]

Just get a 50mm Tial. This thing is amazing. I don't use t-bolt clamps, just the standard worm gear clamps. I also don't use any support for any of tubing. I've never had one tube pop off since I installed my SC almost 6 months ago. It is loud though. No getting away from that.

 

[Twinscrewgt]

It usually takes more than 12psi to blow piping off

 

[TheKurgan]

It usually takes more than 12psi to blow piping off

Vacuum blows piping off. Granted since I have FRPP cams I do have a little less vacuum, but not by much. I'll still pull -20 or so on the gauge.

 

[Tre06GTP1SC]

Yeah Im not worried about the noise. There isn't any hiding the Procharger anyway. I talked to the shop and we are going with a 60mm. He either said tial or turbosmart didn't catch all what he said because my cell was breaking up.

 

[Twinscrewgt]

If you're blowing off clamps when you let off I'd say your bov isn't doing its job.

 

[Tre06GTP1SC]

Good call genius! One post too late....LOL

 

[TheKurgan]

LOL.

 

[19COBRA93]

Vacuum blows piping off. Granted since I have FRPP cams I do have a little less vacuum, but not by much. I'll still pull -20 or so on the gauge.

Eh? Unless you're saying that not enough vacuum can cause the valve to not open all the way... Either way, vacuum doesn't blow piping off.

 

[TheKurgan]

Eh? Unless you're saying that not enough vacuum can cause the valve to not open all the way... Either way, vacuum doesn't blow piping off.

Why do they always come off on decel then ? There's no boost going on then. I think the TB slamming shut and the engine pulling alot of vacuum during that process is what causes the pipes to pop off. Please correct me with facts if that is wrong.

 

[FalconGTHO]

Why do they always come off on decel then ? There's no boost going on then. I think the TB slamming shut and the engine pulling alot of vacuum during that process is what causes the pipes to pop off. Please correct me with facts if that is wrong.

Umm, the engine doesnt spin down immediately neither does the s/c. Additionally, theres boost already in "the pipeline". The TB blade snaps shut, WHAM all that boost that was made just a moment ago slams against the blade forcing the tube off.

However, as I mentioned, the tube coming off happens even ABSENT of a full boost pull and off throttle snap close. The D1 is building SOO much boost in the pipe that it cant exit out of the BOV fast enough and it cant rush past the partially open TB blade fast enough either.

Ill post video of this soon once I isolate it.