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TRACK CAR
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Discussion Starter #1
I have been running 2 HKS SS BOVs on both the lower intercooler pipes with seperate vacume lines running to them. It seems like this setup works fine for both low and high boost but in some partial throttle situations it seems like the car will physically buck from surge. I am redoing my intercooler piping and was wondering where you guys put you BOV(s) and what kind you use for quick response. I was thinking about maybe switching back to just 1 BOV because two didnt really seem to help anything except block airflow to the power steering cooler. So maybe a Tial mounted close to the throttle body? Just wanted to check out what setups the serious guys run? Thanks for the help.

Mike
 

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Banned
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i originally heard tb which makles sense for response but it leaves all the piping before the bov to have air in it. I have one there and one on the lower ic piping before the intercooler on the turbo side...... i was getting surge after i went single with only one BOV on the tb side this only happened on very ligth throttle appliacations or when free revving. I have noticed taht most shops put them on the piping right after the turbo whcih makes the most sense in preserving the turbo....all in all i am happy with one close to the turbo and one close to the tb i added the hks pruple insert in both of them and it isnt that loud and is a different noise than most BOV's we are all use to hearing
 

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Since the pressure wave travels towards the turbo, IMHO, that is the best placement for venting properly if you are using one valve. With two, it makes no diff, since you have one on either end, other than to be as close to the turbo, and the TB plates as possible. Carl
 

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OG
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IIRC, Andi B had the same part-throttle surge issue, and solved it by adding a Blitz BOV. I dn't know what is different about the Blitz, but it seemed to fix his problem.

Cheers
Rich B
 

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TRACK CAR
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Discussion Starter #5
Rich B said:
IIRC, Andi B had the same part-throttle surge issue, and solved it by adding a Blitz BOV. I dn't know what is different about the Blitz, but it seemed to fix his problem.

Cheers
Rich B
Do you happen to remember where he had both of them located?
 

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boost freak
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in2twins said:
Since the pressure wave travels towards the turbo, IMHO, that is the best placement for venting properly if you are using one valve. With two, it makes no diff, since you have one on either end, other than to be as close to the turbo, and the TB plates as possible. Carl
while the wave does travel towards the turbo, it starts @ the closed throttle plate. putting the BOV as close to the throttle plate as possible allows you to stop it @ the source....and as an added bonus, the turbo is free to continue spinning and keeps the IC/pipes full of air so when the BOV closes and the throttle plate is opened, you're back on boost more quickly.

as for response, the SSQV doesn't do so well @ lower boost levels, it needs a fairly large pressure differential to open fully. at least it doesn't leak...
 

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OG
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I don't remember at all.. THe salient point was that the blitz valve did the trick as far as part throttle surge went. PErhaps if you PM him he might tell you..

Cheers
Rich B.
 

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Supra OG
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1,002 Posts
MTR said:
I have been running 2 HKS SS BOVs on both the lower intercooler pipes with seperate vacume lines running to them. It seems like this setup works fine for both low and high boost but in some partial throttle situations it seems like the car will physically buck from surge. I am redoing my intercooler piping and was wondering where you guys put you BOV(s) and what kind you use for quick response. I was thinking about maybe switching back to just 1 BOV because two didnt really seem to help anything except block airflow to the power steering cooler. So maybe a Tial mounted close to the throttle body? Just wanted to check out what setups the serious guys run? Thanks for the help.

Mike
Adding a blitz DD with the stiff spring helps.... and I would recommend it. My setup was 1 HKS + 1 Blitz DD... and the blitz helped with the part throttle surge a good bit.

More importnatly though, I later discovered the reason for the part throttle surge was that my boost controller was controlling manifold pressure and not IC pipe pressure. Pretty much all EBCs are designed this way, and they tell you in the directions to connect the reference hose from the head unit to the manifold. This is retarded, they should know better -- but I guess they only care about drag racing and don't give a flip about dirveability. So at part throttle, hypothetically, you may have only .4 bar in the manifold, so your boost controller isn't doing shit to limit the boost, while your turbo is making upwards of 2 bar of boost and it doesn't have anywhere to go bacause your throttle plate is limiting the flow, your HKS SSQV is slam-sealed by the 2 bar of boost (since it's a pull-type and boost seals it), and you haven't yet installed your blitz DD that would open up at part throttle on boost...... See where I'm going with this?

The solution is:
- make sure your boost controller is controlling ***IC PIPE PRESSURE***, not manifold pressure. Ignore the directions, they're retarded. Reroute the reference hose from the EBC to some pre-TB nipple.
- for those times when you're running high boost and your boost controller would STILL not be invoked at part throttle...... you'll still need to have a bov that's good and responsive at part throttle even on-boost... so add a good push-type BOV that is responsive and doesn't leak at moderate levels of boost at WOT... IME the Blitz DD with the optional stiff spring installed does the trick nicely.
- last but not least, make sure you've got a turbo with a halfway decent surge line... i.e. *NOT* a T70 or something like that with an awful surge line.....

Best regards,
Andi
 

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TRACK CAR
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Discussion Starter #9
Thanks a lot for the help andi. Where exactly did u have the bov's mounted and how did you run the vaccume lines to them? Single lines for each of them or one line T-ed off?

Mike
 

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Supra OG
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MTR said:
Thanks a lot for the help andi. Where exactly did u have the bov's mounted and how did you run the vaccume lines to them? Single lines for each of them or one line T-ed off?

Mike
The HKS was here:


And the blitz was on the IC pipe going to the throttle body, in that bend, kinda between the radiator shroud and the throttle body...

If I recall correctly (I am NOT 100% sure), I had one line for both BOVs off the manifold, T'd or Y'd to the two...

Andi
 

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OG
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I feel stupid, now that I read Amdi's post. IIRC, after Andi's experience, a lot of us (myself included) moved the BC reference to the IC pipe.. I'd forgotten that we collectively thought it was the solution to part-throttle surge, and that the Blitz valcve was a more like a decent band-aid.

If you move the BC reference to the pipe exiting the IC and have a VPC, you might as well also drill and tap a reference for the VPC temp sensor. I also went ahead and drilled and tapped another hole and put a plug in it, in case I want in the future to inject meth, or want another port to measure intake air temperature or pressure.

Cheers
Rich B.
 
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