Blow through

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Slunch

New Member
I know there are a couple of threads on this topic already but it would be great if we could visit it again. I have a Z32 and want to it set up as a blow through. I noticed a few on here have installed the sensor in a three inch pipe which I fancy having a go at, any hints would be greatly appreciated.

I've been doing a bit of research on the topic and a lot of bods suggest moving the bov to a pre maff location to resolve the rich overun issue and associated pops and bangs.

I was thinking of siting the bov pre intercooler with the maff in the middle of the straight run from the front to the plenum. Anyone done this or can foresee any problems?
 
S

Slunch

New Member
rich1216 said:
I made my z32 in 18" of 3" stainless with the bov in standard position and had no issues
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thanks Rich, sounds like the kind of thing I'm thinking of. How did you go about yanking the Z32 apart and securely mounting the sensor, do you have any pictures? I rather avoid a whoops..... does anyone have a Z32 for sale... I run a standard maff and bov off the plenum at the moment, well it's hiding under a cover on the drive but when it was on the road, and pretty well every time I lifted off I'd get bangs. I have got a pretty big cooler though so it's dumping a lot of charge.
 
campbellju

campbellju

Moderators
Staff member
What HP/boost you running. Might be simpler just to remove your BOV to eliminate the cause rather than trying to alleviate the symptoms?

Up to 450hp/2bar you can manage without. Approaching >2bar boost you might need one but I don't have personal experience above this level.
 
rich1216

rich1216

Member
Slunch said:
thanks Rich, sounds like the kind of thing I'm thinking of. How did you go about yanking the Z32 apart and securely mounting the sensor, do you have any pictures? I rather avoid a whoops..... does anyone have a Z32 for sale... I run a standard maff and bov off the plenum at the moment, well it's hiding under a cover on the drive but when it was on the road, and pretty well every time I lifted off I'd get bangs. I have got a pretty big cooler though so it's dumping a lot of charge.
Click to expand...

Sorry don't have any pics got rid of it now. Just carefully cut a z32 open and take the board and sensor out. I cut an exact hole in the tube for the sensor so it will seal with the o ring. Then I made a base plate around the hole to screw the board to and just made stainless sides to make it into a box and sealed the original z32 lid back on. Didn't have any problems with it.
 
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Slunch

New Member
Low between 300 and 330, basically maxed out the stock turbo, maf, injector combination with a piggyback, wide band and egt and supporting mods. I am planning to head for 400+ but that is a way off. What boost I end up running will depend on the turbo I get. It may be getting on for 2 bar as I'd like to go as small as possible and get the torque, it's going to depend on budget at the time. At the minute I want to lay the ground work, get all the plumbing in etc to support that goal before I take the car to see Ed to get mapped and probably a list a faults that need addressing. If a recirc will manage it why not, though like most I have been indoctrinated into the raaaah whoosh of performance turbo ownership. Would you recommend a stock valve or some other?
 
campbellju

campbellju

Moderators
Staff member
I ran a 3071 which was fine running 1.9Bar without a BOV for around 20K miles. The engine gave up first before the turbo.

I just got an Engineering shop to cut off the outlet for the BOV from the manifold and weld up the hole for about £20 cash. I first tried it capped and played around with BOV vs. no BOV. Occasionally the cap would fly off at high boost so I got it welded and never looked back.

Recircs do very little expect dampen the noise. Even without a BOV the intake system dumps it's pressure very quickly. The idea that the recirc keep the turbo spinning is just untrue as a large part of the air will be going the same way as when you don't use a BOV.

With no BOV you can get issues with the MAF reading when the air is moving the wrong way and you get back on the throttle but it's easy to map around with accelerator input settings.

Helped to tidy up the piping mess in that area and saved some more weight in the engine bay :)
 
S

Slunch

New Member
rich1216 said:
Sorry don't have any pics got rid of it now. Just carefully cut a z32 open and take the board and sensor out. I cut an exact hole in the tube for the sensor so it will seal with the o ring. Then I made a base plate around the hole to screw the board to and just made stainless sides to make it into a box and sealed the original z32 lid back on. Didn't have any problems with it.
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That sounds very doable, thanks. Extending the plug wires isn't a bother, I saw a post from Jon a while back when I was building an airbox seems to work fine. Blow through here we come.... Unless there's a solid reason for not doing it that someone's sitting on?
 
S

Slunch

New Member
campbellju said:
I ran a 3071 which was fine running 1.9Bar without a BOV for around 20K miles. The engine gave up first before the turbo.

I just got an Engineering shop to cut off the outlet for the BOV from the manifold and weld up the hole for about £20 cash. I first tried it capped and played around with BOV vs. no BOV. Occasionally the cap would fly off at high boost so I got it welded and never looked back.

Recircs do very little expect dampen the noise. Even without a BOV the intake system dumps it's pressure very quickly. The idea that the recirc keep the turbo spinning is just untrue as a large part of the air will be going the same way as when you don't use a BOV.

With no BOV you can get issues with the MAF reading when the air is moving the wrong way and you get back on the throttle but it's easy to map around with accelerator input settings.

Helped to tidy up the piping mess in that area and saved some more weight in the engine bay :)
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Mate I'm stunned, I've heard of motorsports cars running without a bov and antilag etc but assumed there would be serious reliability/ driveability issues on a road car. BOVless is worthy of serious consideration. Do you know anyone else who's done this.

Would free up a little change, assuming I could find someone wanting a genuine HKS SSQV, and my engine bay does look like a snakes wedding. I may end up giving it a go.

But I'm sort of exploring ways of stabilizing airflow around the maff rather than dialing it out during tuning and avoid backpressure on the compressor. I've seen turbos with the bov built into the compressor housing. I'm thinking stick a big intercooler in between that and the maff and the airflow back from the plenum should be minimal when the throttle snaps shut and no back pressure on the turbo. If the bov's on the plenum then the intercooller would depressurise across the maff, primarily, big rich lump, plus a bit of backpressure to stall the turbo. Best I can do is put the bov in pre cooler- theoretically does this work?
 
red reading

red reading

Active Member
I used to run 2 bar on a 3076 with no bov and blow thru maf, awsome throttle response and no maf issues or turbo issue, now run 2 bar on a differant ecu and map but still no bov .
 
red reading

red reading

Active Member
He ment thankyou for not making him explain, maka is a man who is a bit clever with turbos and the like and has explained all the bov things many times before.
 
campbellju

campbellju

Moderators
Staff member
Our resident turbo guru not wanting to explain why BOV's are not required and why the air rather than the turbo stalls. Ed designs turbos for a living and its an periodic question he answers. In the past someone might have flamed you but we're all more relaxed nowadays
 
campbellju

campbellju

Moderators
Staff member
Slunch said:
I may end up giving it a go.
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Remove the air feed from your current BOV actuator to test the theory. The BOV should never operate and act like a cap..... unless of course it's an old leaky BOV which is another reason to bin it and weld up the hole :)

P.S. Your theory about how the air moves around is off the mark. When the throttle closes I would drop from 1.9 bar down to about 0.7bar in 0.5s or about the time it took to change gear. The other 0.7bar bled out in the following 1s. With a BOV it went to 0Bar (atmosphere) in about 0.1s. It's not anti lag but it did help with response and stopped the BOV dumping air out every time you came off the throttle under normal driving.
 
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M

Makaveli_se7en

Member
sorry just being grumpy, if you do a search for BOV/ dump valve you should find one of my previous posts with the technical detail behind why they're a waste of time.

Not in the turbo design business any more. Have a new job doing vehicle aero and brake cooling (which was the subject of my PhD, so going back to my pre-turbo days)
 
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