How To Tune To Stop Flutter/bovs Causing Stalling.

[Rolls]

Yep, that's why i'm keen to see the factory map of a vehicle that came BOVless, just like you. What cars were like that again? I never knew there were any

FJ20 cars like DR30s, all turbo HR31 skylines, VL turbos, C32 Laurels, Datsun Z31 300zx and possibly early cefiros (have a redtop with a silvertop cam cover lol).

Edited September 14, 2011 by Rolls

[Legionnaire]

OK, thanks, I'll see if I can find them in Nistune ROM database.

[Borci88]

Does anyone realise that whenever 98% of the population hears a BOV, the first thought that goes throught their head is usually "wanker" or "dickhead"...

lol

That fact is it? Funny because I think quite the opposite and do admire a nice Bov or Flutter.

[Rolls]

That fact is it? Funny because I think quite the opposite and do admire a nice Bov or Flutter.

Lol don't even bother, mafia trolls 99% of threads here.

[lilcrash]

The Toyota 3tgte also ran a hot pipe with out a bov. They had a 3 foot long intake pipe to the afm though, mayb that helped.

[The Mafia]

Oh it's fact. You're just in the 2%.

[Jeremy93]

Mafia, how can you prove it's fact when no studies have been placed upon the subject?

Personally I find BOV's awesome, had a HKS one on my line for a few months but removed it as it sounded weird with the old stock exhaust, I had only had it stall a few times on me (maybe it was just a slipping clutch?) but in my opinion it was worth it.

Just my 2 cents.

[DVS JEZ]

The stalling can be avoided with a different driving style. Mo old skylines had atmo BOV and would only stall if u clutched in above say 3000rpm and let it return to idle.

So to avoid it use the engine braking till the engine is below 3000rpm then clutch in and the engine will be able to catch itself becore stalling.

Havent tested this with an atmo BOV but in the ign maps i normally add a few degree's of extra timing in very low rpm area's to help bring the engine rpm up when it tries to stall

[The Mafia]

I think that having to tune your car and change your driving style, just to sound like a dickhead is the stupidest thing I have ever seen.

It's a MAF system, it's not meant to have a Atmo leak in it. When are you people goin to learn?

If you want to sound stupid, with your car sneezing all the time, get a MAP ECU

But usually, people that are stupid enough to want to chance the bov just for sound dont understand how the air measurement system works...

[Rolls]

mafia just stop posting, ironically you are the one who is being a dickhead here.

[SargeRX8]

mafia just stop posting, ironically you are the one who is being a dickhead here.

Sorry mafia but I am agreeing here...

My old r33 with the pfc hated the blocked bov and stalled every time. This car I got now, when it was stock, never stalled and it came with an atmo which I then swapped top a stock blocked bov fluttering day and night without an issue. Even now after jez tuned my car I had my bov blocked and it was awesome. Just a couple of days ago.I've began stalling even with the plumb back bov running... I've got a vacuum leak or my aac is hating life.

[The Mafia]

Having a blocked bov is just as bad - Nissan designed the car to have it there.

If you, right from square one just left it plumb back, you would have saved time and money to have to tune out the massive air leak in the first place.

So no, im not the dickhead. I'm the educated tuner that knows a MAF system is not meant to have any air escaping from any point past the air flow meter. Anyone that introduces this does not understand how it works, and just wants sound, just to be a dickhead. It's not performance enhancing at all.

And don't use the crap excuse that the tuner "says its ok", you want it, so he'll do it and take your money. He'll even tell you it's ok. If he ever tells you that a MAF system is ok with a ATMO bov, find another tuner. A real tuner will still do it but tell you it's not ideal and go with a MAP engine management system.

People ask me to make their car run better because it's stalling and carrying on - I do it because that's what they want. But certainly not a free tune. I also tell them that it is making a system not work how it is supposed to - and half of them choose not to keep the atmo bov because they understand and want their car to run perfect, and only put it on because some clown said it was better and they didn't know any better themselves. (we were all new at some point)

So - whatever you want to do. But, doing it can only be for noise, and that means you're an attention seeking dickhead. And, ruin it for the rest of us because now cops hate skylines and pull them up just because of that - they are a skyline.

[paulr33]

i agree with mafia's thoughts on this

the car should work correctly as it was designed and match the system setup ie ljetro with re-circ value (i dont think any OEM's call it bov)

tuning around the stalling (the purpose of this thread) is a good way to resolve it, but why bother? why not just run the correct re-circ setup?

learning is good and solving complex problem is good but it sounds like a workaround more than anything

[BOOZTJUNKEY]

The stalling can be avoided with a different driving style. Mo old skylines had atmo BOV and would only stall if u clutched in above say 3000rpm and let it return to idle.

So to avoid it use the engine braking till the engine is below 3000rpm then clutch in and the engine will be able to catch itself becore stalling.

^^^this Thanks

Havent tested this with an atmo BOV but in the ign maps i normally add a few degree's of extra timing in very low rpm area's to help bring the engine rpm up when it tries to stall

[paulr33]

Definitions

A typical piston-type dump valve, used in auto racing. Unlike a blowoff valve, this one does not vent to the atmosphere. The small hose at the top is a feed from the intake manifold.

A compressor bypass valve (CBV), also known as a pressure relief valve or diverter valve, is a manifold vacuum-actuated valve designed to release pressure in the intake system of a turbocharged vehicle when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor.

A blowoff valve, (sometimes "hooter valve", not to be confused with a bypass valve) performs the same task but releases the air into the atmosphere instead of recirculating it. The blowoff action produces a range of distinctive hissing sounds, depending on the exit design. Some blowoff valves are sold with a trumpet-shaped exit that intentionally amplifies the sound. Some turbocharged vehicle owners may purchase a blowoff valve solely for the auditory effect even when the function is not required by normal engine operation. Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere.[citation needed]

Blowoff valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine. When the throttle plate on a turbocharged engine closes, the high pressure air in the intake system is trapped by the throttle and a pressure wave is forced back into the compressor. The compressor wheel slows rapidly and may even stall, and the driver will notice a fluttering air sound. The rapid slowing or stalling stresses the turbo and imparts severe turbo lag if the driver accelerates immediately after the surge event.

Disadvantages

In the case where a mass airflow sensor (MAF) is used and is located upstream from the blowoff valve, the engine control unit (ECU) will meter out excess fuel because the atmospherically vented air is not subtracted from the intake charge measurements. The engine then briefly operates with a fuel-rich mixture after each valve actuation.

The rich mixing can lead to hesitation or even stalling of the engine when the throttle is closed, a situation that worsens with higher boost pressures. Occasional events of this type may be only a nuisance, but frequent events can eventually foul the spark plugs and destroy the catalytic converter, as the inefficiently combusted fuel produces soot (excess carbon) and unburned fuel in the exhaust flow can produce soot in the converter and drive the converter beyond its normal operating temperature range.

One approach used to mitigate the problem has been to reduce the boost pressure, which reduces the required venting volume and yields less charge over-calculation by the ECU. The air can also be recirculated back into the intake, a typical stock setup for cars with an upstream MAF sensor. The situation can also be corrected by switching the fuel metering system over to a manifold absolute pressure sensor, a conversion that usually requires a compatible aftermarket ECU or piggy-back fuel controller. The MAP sensor monitors the absolute pressure in the manifold at all times and will correctly detect the change that occurs when the valve vents, allowing the ECU to reduce fuel metering accordingly.

[SargeRX8]

Let me understand then what exactly is happening on throttle off. When you come off boost and shut the throttle the air will revirb back and flow through the recirc pipe back into the turbo and stay in the system. Correct? Ok now lets say, just for simple example, the car measured 10 litres of air coming in and allowed 200ml of fuel to be added for this air. The engine does its cycle on boost, burns 8 litres of air and 100ml of fuel. You back off the throttle and the plate shuts with this 2 litres of air still in the intake before the throttle and 100ml of fuel for the counted air. To prevent the car from stalling is this where the AAC valve kicks in? Since the throttle is closed you are going to need to let this air come in to burn this fuel to keep the engine on and from stalling. My car for the last week has been stalling its nut when I come off boost and let the revs drop. I am running a full recirc system.

What is the cause of this stalling state? Ive cleaned the AAC but have not taken it for a drive yet. Am I right when I am saying the engine is using the AAC to let in this air to burn off this fuel? When the throttle is shut, obviously air isnt going to get in there but if there is fuel in the piston its going to need air to burn...

Why do people drive motor bikes with exhausts so loud they can be heard kilometers away? Why do people run screamer pipes? Why do people run straight pipe exhaust? Why do people run titanium exhausts? Its their car. If you run a pod filter, most people are immediately going to say that you have a vented bov because the sound which comes through the BOV, so already you are a dickhead. And these days it doesn't take a BOV to make you a dickhead, people see you in a skyline and label you as a dickhead. Everyone here chose to drive a skyline. Thank your selves you don't live in america driving a jap car.

[GTSBoy]

Let me understand then what exactly is happening on throttle off. When you come off boost and shut the throttle the air will revirb back and flow through the recirc pipe back into the turbo and stay in the system. Correct? Ok now lets say, just for simple example, the car measured 10 litres of air coming in and allowed 200ml of fuel to be added for this air. The engine does its cycle on boost, burns 8 litres of air and 100ml of fuel. You back off the throttle and the plate shuts with this 2 litres of air still in the intake before the throttle and 100ml of fuel for the counted air. To prevent the car from stalling is this where the AAC valve kicks in? Since the throttle is closed you are going to need to let this air come in to burn this fuel to keep the engine on and from stalling. My car for the last week has been stalling its nut when I come off boost and let the revs drop. I am running a full recirc system.

What is the cause of this stalling state? Ive cleaned the AAC but have not taken it for a drive yet. Am I right when I am saying the engine is using the AAC to let in this air to burn off this fuel? When the throttle is shut, obviously air isnt going to get in there but if there is fuel in the piston its going to need air to burn...

AAC valve plays no part. When you are at highish revs (let's say >2000) and you close the throttle, there is enough vacuum in the inlet manifold to keep pulling air past the throttle butterfly regardless of how open the AAC valve is. The high pressure air that is trapped in the inlet tract between the turbo and the throttle also adds to the driving force to push a little air past the throttle and through the AAC valve. This should easily be enough air to keep the engine running when you clutch in for the gear shift. The compressor bypass valve just lets the air go round and round without any air flowing forwards or backwards through the AFM. It is also why the engine usually has a TPS with throttle closed indication so that the ECU can know that regardless of what has just been happening with the rpm and the measured air flow, the engine is now in "gear shift mode" (for want of a better term) and it injects fuel accordingly. If you have a venting BOV then the AFM continues to measure foward flow and that can seriously interfere with the ECU's understanding of what condition the engine is in and it may ignore the TPS and just inject too much fuel, blah blah blah, stall.

Why do people drive motor bikes with exhausts so loud they can be heard kilometers away? Why do people run screamer pipes? Why do people run straight pipe exhaust? Why do people run titanium exhausts?

One the street? Generally because they're stupid enough to think that it will make chicks pull the clothes off and give them a blowie on the spot, or they think the cops don't mind, or they think they're more important than everyone else and need everyone else to be able to hear that important fact.

The truth is, there's a limit to how much weight you need to save on a road car (or bike), there's a limit to how much power you can use in a street car (or bike), there's a limit to how much noise you can get away with before your neighbours dob you in to the cops for being a wanker, etc etc. As a result, there's really no need to have full race style mods on a street car. A piped back wastegate is sensible. A quiet enough exhaust is sensible and will still flow damn near as much as a stratight through. A titanium exhaust doesn't have to be noisy, but why would you need to spend so much on a street car?

Its their car. If you run a pod filter, most people are immediately going to say that you have a vented bov because the sound which comes through the BOV, so already you are a dickhead. And these days it doesn't take a BOV to make you a dickhead, people see you in a skyline and label you as a dickhead. Everyone here chose to drive a skyline. Thank your selves you don't live in america driving a jap car.

I'm not following this last bit. The factory BOV sound through a pod sounds nothing like a venting BOV. And what if I bought my Skyline before all the venting BOV wankers did? (which I did by the way, I have had it since last century). And what the hell would be the problem of having a Jap car in the US? Have you ever been there? Last time I was there, the few decent Jap cars I saw were like little breath of fresh air and they looked cool. Are you saying that US folks look down on Skyline drivers more than Aus drivers do? Why?

[Rolls]

Having a blocked bov is just as bad - Nissan designed the car to have it there.

All the cars I mentioned nissan released from the factory with a MAF and no BOV. I realise that the new cars did hence I wanted to know how they tuned it out.

This thread isn't about should I get a bov or should I make my car flutter, it is how did nissan tune out the stalling issues, that is all.

I'm not following this last bit. The factory BOV sound through a pod sounds nothing like a venting BOV.

With a pod my stock BOV was ridiculously loud, I ended up making a small gasket for the BOV so that it couldn't vent as fast, it still stops reversion (doesn't flutter) but it is much quieter now.

[GTSBoy]

OK, next question. Why did you put a pod on?

[SargeRX8]

I'm not following this last bit. The factory BOV sound through a pod sounds nothing like a venting BOV. And what if I bought my Skyline before all the venting BOV wankers did? (which I did by the way, I have had it since last century). And what the hell would be the problem of having a Jap car in the US? Have you ever been there? Last time I was there, the few decent Jap cars I saw were like little breath of fresh air and they looked cool. Are you saying that US folks look down on Skyline drivers more than Aus drivers do? Why?

http://www.youtube.c...h?v=1jOZjTTWtOI Fast forward to 2:50. This is my car, apexi pod and stock BOV with sleeved standard rubber pipe.

Have you seen any of the videos or read any forums of US cars. They absolutely hate japanese sports cars. No matter what the car is, its always a ricer to them as they love their muscle cars. Just watch videos of organised street racers of JDM cars vs muscle cars and the shit the drivers often cop. Ive seen a lot of videos over the past years. Its alot worse than driving here. I'm not saying their JDM cars are shit, but from what I recall, skylines are not allowed on the streets of america so they are often hated against. Reason they aren't allowed on the street is due to their performance and likeability which will throw people from paying america for more fat ugly american muscle cars. They don't look down on skyline drivers, there are no skyline drivers there. They look down on JDM drivers. Simple as that. ANY video you see of any JDM car, no matter how fast it is, how stock it is, how what ever it is, the comments from other americans will always read "piece of shit japanese ricer shit' and the alike. At least down here people admire our cars.

I remember the first time I went to a skyline meet. It was across the road from my place at the park. I'm not sure if it was SAU but there were obviously heaps of skylines there, a porsche and some other cars. Most had BOV's on them. More often than not when I hear a skyline or JDM car pass me, or go past my house, the bird whistle often follows. Its much more frequent with the evo drivers.

I'm considering upgrading to a MAP based ECU in the future purely to make these issues a thing of the past. Damn power FC should have some adapter things I can hook up to it.

Edited September 18, 2011 by SargeRX8