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[Atticus]

long story short i dont want any ricer bov that sounds like shit
i modified a dsm bov to support high boost (not crushed) and it was surging at high boost for a quick sec before the bov opened.
my vac source is T'ed off the main break booster line

http://www.thedodgegarage.com/turbo_bov_mod.html

2 questions

1 will the holset anti surge housing help and prevent surge
2 if not how bad is a a little surge before the bov opens

[Joseph Davis]

The anti surge feature has to do with the compressor building significant pressure in very low flow operation - familiarize yourself with the surge line on a compressor map, it's meant to modify that for a broader area of compressor operation.

You need to run a TPS-actuated switch to go from normal to no-leak, that way when you let off the pedal it doesn't surge.

[dr3w]

Instead of buying a new turbo why don't you just by a good diverter valve and recirc it if you dont like the sound of a bov

[clwtwizted]

Run two blow off valves, and recirculate them both to keep it quiet.

[Atticus]

The anti surge feature has to do with the compressor building significant pressure in very low flow operation - familiarize yourself with the surge line on a compressor map, it's meant to modify that for a broader area of compressor operation.

You need to run a TPS-actuated switch to go from normal to no-leak, that way when you let off the pedal it doesn't surge.

ahhh, makes sense

Instead of buying a new turbo why don't you just by a good diverter valve and recirc it if you dont like the sound of a bov

already have  the holset

i added a nipple to the old dsm and made a new flange today
most likely going to go on the hot side with an electric solenoid for quick open and high boost

Run two blow off valves, and recirculate them both to keep it quiet.

[92CXyD]

Run two blow off valves, and recirculate them both to keep it quiet.

That is what I'll be doing on my setup using two DSM 1g bovs. ;D

[Atticus]

Run two blow off valves, and recirculate them both to keep it quiet.

That is what I'll be doing on my setup using two DSM 1g bovs. ;D

modified or stock?

[crx-t]

We're adding a second bov to try to keep the surge down in my buddies supra. One before IC, one after.

[keelay]

We're adding a second bov to try to keep the surge down in my buddies supra. One before IC, one after.

Get both of them as close to the compressor as you can, numbnuts.


I guess we got another "my buddy's car" guys.


































































Stay wednesday.

[HiProfile]

Instead of buying a new turbo why don't you just by a good diverter valve and recirc it if you dont like the sound of a bov

already have  the holset

I don't think you understand what an anti-surge housing is intended for. It's not to prevent off-throttle surge, it's to prevent WOT surge. Surge as the turbo is at full boost is what kills turbos. Flutter/surge when you let off isn't the most destructive type, but it's still not helpful to turbo life.

i added a nipple to the old dsm and made a new flange today
most likely going to go on the hot side with an electric solenoid for quick open and high boost

Run two blow off valves, and recirculate them both to keep it quiet.

The electric valve is a good idea though, that will let them open fast when boost is in the line, but stay mostly closed for most vac levels. If you want to say fuck it and go with aftermarket BOV's, get 1-2 forge recirculated BOV's. They're almost impossible to hear - no whistle, just a quiet "shuuu".

I guess we got another "my buddy's car" guys.
Stay wednesday.

My buddy's car just pulled a 9.9@146 first run with his slicks and th400 installed. I bet it's faster than the n00b's buddy's car.

[jabberwock]

2 modded BOV's....?

[keelay]

2 modded BOV's....?

Yes, oh wait, b&

[onlyflash944]

Get both of them as close to the compressor as you can, numbnuts.

i would argue the opposite, as far as trying to vent the excess air.  when the throttle plate slaps closed whouldn't the pressure wave build up from there back toward the compressor?  think about a column of air running into a brick wall.  it would be the front of the column that crumples first.  what is the theory behind your reasoning?

[keelay]

Because the whole point of them is to prevent the air from slamming back into the compressor, and either slowing it, stopping it, or worst case, reversing it. Which will kill a turbo, and increase spool time. Fuck the throttle plate, it's those spinning fins that matter.

[Joseph Davis]

Vent as close to the turbo as possible.

[onlyflash944]

interesting

i'm not doubting anyone, but i'd like to see test results with both options.

[keelay]

interesting

i'm not doubting anyone, but i'd like to see test results with both options.

I honestly would too, just to see if there is any definitive data on the subject. Close to the turbo is just the general consensus, but I've learned that things that people disagree on like this, and there is no clear cut advantage, the difference/gains are very minimal.
   From MY knowledge, I've seen no data, what I know is what I've learned and researched, with no hard evidence, just theory.

[kgx]

2 questions

1 will the holset anti surge housing help and prevent surge
2 if not how bad is a a little surge before the bov opens

1. no. that's not its purpose.
2. lift-off surge is no big deal.

i've found throttle response between shifts to be better without a BOV. i have no plans to run a BOV ever again. why dump all that boost that you just spent energy compressing?

i really should dig up the datalogs of the pressure spike that supposedly "damages" the turbo when the throttle plate closes. it's essentially a pressure wave that's +/- 3 to 5psi above/below nominal boost pressure, and it decays as the impeller slows down (which is due to the loss of drive pressure on the exhaust side, NOT the compressor surging). at full boost, the turbo impellers are spinning with the stored energy of an engine flywheel at 3/4 redline. they don't give a shit about a piddly pressure wave.

edit- here it is:


this was from an autospeed article a few years back. 3psi/div vertical; 200mS/div horizontal.

BOV/BPVs are an emissions device. they keep the compressor backwash from upsetting the hotwire MAF sensors that are typically mounted directly in front of them.

[snm95ls]

Hmmm.  Great info to have, kgx.

I was always concerned about the extra thrust loads placed on the compressor wheel, but with such a relatively small flux in pressure, it seems to be a non-issue.

[kgx]

for what it's worth too, they had an interview with one of the aussie nissan race techs and he said that they had tested their race car with and without a BOV and on a track with a 1:40 average lap time, running without a BOV was typically worth 2 seconds a lap.

on top of that, i've never seen, nor heard of a turbo that failed from lift-off compressor surge. i don't know anyone who has (i have a friend who works for honeywell- he hasn't either). i know there are a lot of warnings that it damages the turbo, but the evidence (or lack thereof) just doesn't lend credibility to those warnings.

[snm95ls]

for what it's worth too, they had an interview with one of the aussie nissan race techs and he said that they had tested their race car with and without a BOV and on a track with a 1:40 average lap time, running without a BOV was typically worth 2 seconds a lap.

on top of that, i've never seen, nor heard of a turbo that failed from lift-off compressor surge. i don't know anyone who has (i have a friend who works for honeywell- he hasn't either). i know there are a lot of warnings that it damages the turbo, but the evidence (or lack thereof) just doesn't lend credibility to those warnings.

2 seconds improvement in lap time is a huge improvement for such a small change.

Wow!

[onlyflash944]

that printout looks like it came of a gameboy


interesting info for sure

[kgx]

We used a Fluke 123 digital Scopemeter and a Fluke pressure transducer.

here's the scope capture from the BOV activated:


i wish they had done scope captures of an actual shift though, logging the pressure after you get back on the throttle after a shift.