Wastegate Flutter.

[Tricky-Ricky]

So are we saying this happens? On a pre-turbo (or draw through) system:

 

1. On full boost at WOT, MAF reads X amount of air. Engine adds X amount of fuel.

2. You come off the gas completely. TB shuts closed.

3. Compressed air has nowhere to go, so pushes back into the turbo.

4. Air goes through the turbo back past the MAF into atmos pressure, causing the MAF to read air again.

5. As the MAF is reading air movement, the engine adds X amount of fuel despite no extra air going past the TB.

 

That's the only way I can see a non-BOV system adding fuel after you close the TB. On a system with a VTA BOV that sits after the MAF, then yes that would cause the engine to run rich as you've dumped metered air (as has already been said).

 

No because the MAF has pre read the airflow and ECU has already added the correct amount of fuel, throttle closes, DV dumps the now presuriasd system, but because the mixture is now over rich, it tends to ignite in the hot exhaust, don't forget you dealing with micro seconds at say 5-7K RPM, and usually highish boost pressure.

Edited April 20, 2016 by Tricky-Ricky

[Ekona]

I get that, but I'm referring to a system with no BOV at all. I guess I'm struggling to see how the car runs rich when no air is being removed.

 

Should probably have corrected my post to show I was replying to Richf rather than yourself though, you nipped in before I posted

[Richf]

The maf cant accuratly read the air being blown back past it the wrong way

[Tricky-Ricky]

I get that, but I'm referring to a system with no BOV at all. I guess I'm struggling to see how the car runs rich when no air is being removed.

 

Should probably have corrected my post to show I was replying to Richf rather than yourself though, you nipped in before I posted

 

Its simple, with no dump of airflow that already been read by the ECU, the mixture is correct and not rich, I think your trying to over think it, there is not enough air movement in reverse for an AFM to read, although I am pretty sure it could read in reverse as its not directional,

An AFM reads the cooling effect that airflow has, its basically a heated wire that shows a voltage increase as its cooled

 

Also when the throttle plate is shut there is the closed voltage signal sent to the ECU which in response will shut off the injectors, its a bit more complicated than that but...

Edited April 20, 2016 by Tricky-Ricky

[Ekona]

Exactly! So how does the engine run rich? It's not seeing any more or less air than it's supposed to.

 

I don't get this at all.

[Tricky-Ricky]

Exactly! So how does the engine run rich? It's not seeing any more or less air than it's supposed to.

 

I don't get this at all.

 

Which scenario are you referring to?

Boosted with BOV, or boosted without?

 

With BOV the already metered air is dumped, so ECU has already added the correct fuel, but as some of this air has been dumped, the fuelling is rich.

 

Without BOV there is no change in fuelling when the throttle is shut, as the metered air is the same, so fuelling is correct.

[Ekona]

Boosted, no BOV.

 

Richf said his car stalls due to running rich when run with no BOV on a draw through system. I are teh confuzed.

[Tricky-Ricky]

Boosted, no BOV.

 

Richf said his car stalls due to running rich when run with no BOV on a draw through system. I are teh confuzed.

 

Really never heard of that happening before now, I think it may well have been due to another problem, and not related to the AFM and boost,unless it was faulty.

Edited April 20, 2016 by Tricky-Ricky

[TT350]

[Richf]

Boosted, no BOV.

 

Richf said his car stalls due to running rich when run with no BOV on a draw through system. I are teh confuzed.

 

Read post 28 , how the air is directed through an afm is important let alone the difference between drawing nice cold air in , compressing it and mixing it with other vapour and then blowing it back through the turbo

[Ekona]

How does that relate to the car running rich and stalling, on a system with no BOV?

[Husky]

Car supplies the correct amount of fuel for the air that is metered in. For simplicity let's say 1 amount of air gives 1 amount of fuel. Air coming back out the air intake due to closed off bov will be read again (albeit not accurately), now car thinks theres more air coming in even though there isn't. 2 air now gives 2 fuel. The problem is that the engine is actually only getting 0.1air but it's still going to give that 2 fuel as dictated by the AFM.

 

That's my grasp if it thus far.

[Tricky-Ricky]

I have never heard or experienced this happening, for the reasons I have already mentioned, its not possible to get enough flow back through the still spinning turbo compressor impeller, as it breaks up any flow, besides once the throttle plate is closed, which sends a voltage signal to the ECU, it then shuts off the injectors so no more fuel can be added anyway.

[Rock_Steady]

Either way, i loved the sound of the flutter. i was running a hybrid ball-bearing turbo with a metal hot side impeller, straight intake and pop charger. Sounded really

Edited April 22, 2016 by Rock_Steady

[Husky]

Ok, so if one were to feel the need to remove their BoV and block that off, what would a noob use to achieve this?

[Tricky-Ricky]

Ok, so if one were to feel the need to remove their BoV and block that off, what would a noob use to achieve this?

 

 

Err remove the BOV and block off the mount/pipes, it will have either a mount that fixes it to a boost pipe, or a hose from said boost pipe, and a small trigger pipe from a vacuum source.

[Husky]

Just need to find something to blank it with... Can I use a chunk of wood? Joke I guess I have to go get something machined then, or are there aftermarket parts for it? Only thing I've found under ST205 bov blanking is a 4 year old post which was a dead end.

[andybp]

Ok, so if one were to feel the need to remove their BoV and block that off, what would a noob use to achieve this?

My advice would be don't

It's there for a reason well several really

to prevent damage to the turbo especially if it has ceramic blades as some Celica's and Mr2's had from the factory

to stop the turbo stalling, which will increase lag

and stop over-pressure in the system between the turbo and the throttle body causing potential damage this was caused when the vacuum hose came off my BOV

 

 

if you really want this sound then get an adjustable BOV so you still have some protection

[Husky]

Basically my Blitz BoV blows too early since I had the hybrid turbo put in, so I have to keep the pressure down or it goes a bit crazy dumping every half second. There is an adjustment on the back but I've checked up on it, it's not an adjustment for the spring, it's for some factory calibration and shouldn't be fiddled with. So I'm back to square one of needing to shell out for a new BoV then, ahh well, thought I may have been onto a cheaper option there

[Ekona]

I've used a bolt, a bit of rubber hose and a couple of jubilee clips before.

[RobPhoboS]

Only the quattro is allowed to sound like Flipper.

[Tricky-Ricky]

Ok, so if one were to feel the need to remove their BoV and block that off, what would a noob use to achieve this?

My advice would be don't

It's there for a reason well several really

to prevent damage to the turbo especially if it has ceramic blades as some Celica's and Mr2's had from the factory

to stop the turbo stalling, which will increase lag

and stop over-pressure in the system between the turbo and the throttle body causing potential damage this was caused when the vacuum hose came off my BOV

 

 

if you really want this sound then get an adjustable BOV so you still have some protection

 

 

 

Turbos only have ceramic blades on the exhaust turbine, not the compressor, these are always metal or nylon, neither will be damaged by having no BOV.

[andybp]

Ok, so if one were to feel the need to remove their BoV and block that off, what would a noob use to achieve this?

My advice would be don't

It's there for a reason well several really

to prevent damage to the turbo especially if it has ceramic blades as some Celica's and Mr2's had from the factory

to stop the turbo stalling, which will increase lag

and stop over-pressure in the system between the turbo and the throttle body causing potential damage this was caused when the vacuum hose came off my BOV

 

 

if you really want this sound then get an adjustable BOV so you still have some protection

 

 

 

Turbos only have ceramic blades on the exhaust turbine, not the compressor, these are always metal or nylon, neither will be damaged by having no BOV.

 

well since i'm obviously dumb i lifted this straight off Garrett's site but what do they know

 

Q. What is compressor surge?

A. The surge region, located on the left-hand side of the compressor map (known as the surge line), is an area of flow instability typically caused by compressor inducer stall. The turbo should be sized so that the engine does not operate in the surge range. When turbochargers operate in surge for long periods of time, bearing failures may occur. When referencing a compressor map, the surge line is the line bordering the islands on their far left side. Compressor surge is when the air pressure after the compressor is actually higher than what the compressor itself can physically maintain. This condition causes the airflow in the compressor wheel to back up, build pressure, and sometimes stall. In cases of extreme surge, the thrust bearings of the turbo can be destroyed, and will sometimes even lead to mechanical failure of the compressor wheel itself. Common conditions that result in compressor surge on turbocharger gasoline engines are:

 

-A compressor bypass valve is not integrated into the intake plumbing between the compressor outlet and throttle body (BOV)

-The outlet plumbing for the bypass valve is too small or restrictive

-The turbo is too big for the application

[brillomaster]

Basically my Blitz BoV blows too early since I had the hybrid turbo put in, so I have to keep the pressure down or it goes a bit crazy dumping every half second. There is an adjustment on the back but I've checked up on it, it's not an adjustment for the spring, it's for some factory calibration and shouldn't be fiddled with. So I'm back to square one of needing to shell out for a new BoV then, ahh well, thought I may have been onto a cheaper option there

 

if you're gonna be shelling out for a new BOV it cant hurt to have a play around with the current one first (assuming you don't make it worse and blow your engine up) or would you hope to sell on the Blitz one once you have a replacement?

[Husky]

Basically my Blitz BoV blows too early since I had the hybrid turbo put in, so I have to keep the pressure down or it goes a bit crazy dumping every half second. There is an adjustment on the back but I've checked up on it, it's not an adjustment for the spring, it's for some factory calibration and shouldn't be fiddled with. So I'm back to square one of needing to shell out for a new BoV then, ahh well, thought I may have been onto a cheaper option there

 

if you're gonna be shelling out for a new BOV it cant hurt to have a play around with the current one first (assuming you don't make it worse and blow your engine up) or would you hope to sell on the Blitz one once you have a replacement?

 

If it's in good condition and working I guess I could sell it, I have a habit of being far too lazy to sell stuff though and it just lays about in my garage. I have a ton of 350z stuff all boxed up in there