P
paulrandy
Guest
:lol: :lol: :lol:
G
GartracS2
Guest
Anti lag is old school and wouldnt be on my shopping list. Your all twittering on about DV`s and chatter. Has anyone ever heard of a system whereby the excess air from off throttle between gear changes can be utilised by forcing into the exhaust turbine thereby keeping it spinning between gearchanges thus reducing lag? EGR system but inlet air is used as opposed to exhaust gas. You have no Dump Valve and no chatter and no lag. PERFECT.
S
stokie1
Guest
EGR ? is this the same as air injection ?
If so big turbo and no lag is good but have heard management
is expensive
If so big turbo and no lag is good but have heard management
is expensive
F
Forge Motorsport
Guest
C
chrislloydus
Guest
So you mean like a recirculating dump valve.........AKA the stock systemGartracS2 said:
A
Anonymous
Guest
:shock: Turbo opened, bits of compressor blade everywhere.MarkTurbo said:
Thought that was what happened with nowhere for boost to dump- plenty 'o backwash to ruin ur blades and slow as slow spool up :?:
The definitive DV guide from one of the leading scooby tuners on scoobynet.
Our ECU will work in a similar fashion to the scooby but our standard turbo's will not shatter as they are not ceramic. The standard bearings will wear faster but no one could say whetehr its 1 year or 10 becasue of all the comments already made in this post.
Can of worms closed??
Jim
-----------------------------------------------------------------------------
There are a number of issues to consider when using a VTA or blanking off the OE recirc valve.
VTA (and recirc) DV's come in a range of opening pressure settings. Whether high or low pressure, with a VTA there can be issues.
1 - Overfueling due to excessive venting to atmosphere
2 - Stalling the turbo
3 - MAF revertions and System volume
4 - Repressurisation time
5 - High pressure damage
Looking at the issues one at a time,
1 - Overfueling due to excessive venting to atmosphere
If you run a standard pressure vent to atmosphere dump valve (BOV, VTA, Atmo DV) with a mass air flow monitoring ECU such as the OE Subaru, then you can have problems when the DV opens under cruise conditions. The DV allows air to escape from the system during the high vacuum conditions during cruise, The reason for this is the signal side of the DV is subject to vacuum and the flow side is subject to slight boost pressure (the difference across the throttle valve) If this exceeds the spring pressure then the valve starts to vent.
This airflow has been monitored by the ECU and fuel is added accordingly, the result is too much fuel for the air being consumed by the engine.
Best case - You just waste fuel but who cares when you get that 'pschhhht' you've always wanted
Worst case - You cause bore wash, increase oil consumption and reduce engine life.
2 - Stalling the turbo
The term turbo stall refers to stalling the airflow across the compressor blades, not physically stalling the rotor (common misconception)
This is a case of what happens if you don't use any DV or use a valve with too strong a spring.
When you lift off the throttle on full boost, the compressed air has no where to go and blasts back across the blades giving that (lovely ) sharp 'cacho' or WRC chirp as some call it. Very taxing for the turbo, all this backwards flow.
Best case - Runs forever (TD series generally tougher than VF series)
Worst case - Shatters compressor wheel or thrust bearing fails
3 - MAF revertions and system volume
This is not such an issue with a TMIC but when FMIC's are used the system volume is so large that when the throttle is brought back from power (boost) to cruise, if a strong spring DV is used (strong enough to eliminate issue 1 ) then you can get a sudden pulse of pressurised air back out of the MAF, this is measured as an airflow (the meter can't differentiate) and the engine overfuels giving a hicup/jolt
Best case - Slightly jerky drive as you come off throttle
Worst case - Very jerky !
4 - Repressurisation time
This is where the stiff spring DV or running without DV scores a point. The system holds more pressure between gearshifts as the DV isn't venting it. Boost recovery in the next gear is improved (slightly)
Best case - Improved response after a gearshift
Worst case - Issues 2 and 3 above.
5 - High pressure damage
If you use no DV or a high pressure DV spring then when the turbo is spinning at high speed and the throttle valve is snapped shut, there is a pressure pulse in the system
which can be high enough to damage the intercooler etc.
Best case - At boost below 1.5 bar you will probably be ok
Worst case - Bigger turbo's/ higher boost may pop hoses off or 'balloon' the intercooler core.
Options ?
A light pressure recirc valve (just like std) overcomes all of the above issues but sounds a bit boring
Sequential dump valve. At light pressure it recircs, at high pressure lift off it still goes Pssshhht
You pays your money, you takes your chances.
Our ECU will work in a similar fashion to the scooby but our standard turbo's will not shatter as they are not ceramic. The standard bearings will wear faster but no one could say whetehr its 1 year or 10 becasue of all the comments already made in this post.
Can of worms closed??
Jim
-----------------------------------------------------------------------------
There are a number of issues to consider when using a VTA or blanking off the OE recirc valve.
VTA (and recirc) DV's come in a range of opening pressure settings. Whether high or low pressure, with a VTA there can be issues.
1 - Overfueling due to excessive venting to atmosphere
2 - Stalling the turbo
3 - MAF revertions and System volume
4 - Repressurisation time
5 - High pressure damage
Looking at the issues one at a time,
1 - Overfueling due to excessive venting to atmosphere
If you run a standard pressure vent to atmosphere dump valve (BOV, VTA, Atmo DV) with a mass air flow monitoring ECU such as the OE Subaru, then you can have problems when the DV opens under cruise conditions. The DV allows air to escape from the system during the high vacuum conditions during cruise, The reason for this is the signal side of the DV is subject to vacuum and the flow side is subject to slight boost pressure (the difference across the throttle valve) If this exceeds the spring pressure then the valve starts to vent.
This airflow has been monitored by the ECU and fuel is added accordingly, the result is too much fuel for the air being consumed by the engine.
Best case - You just waste fuel but who cares when you get that 'pschhhht' you've always wanted
Worst case - You cause bore wash, increase oil consumption and reduce engine life.
2 - Stalling the turbo
The term turbo stall refers to stalling the airflow across the compressor blades, not physically stalling the rotor (common misconception)
This is a case of what happens if you don't use any DV or use a valve with too strong a spring.
When you lift off the throttle on full boost, the compressed air has no where to go and blasts back across the blades giving that (lovely ) sharp 'cacho' or WRC chirp as some call it. Very taxing for the turbo, all this backwards flow.
Best case - Runs forever (TD series generally tougher than VF series)
Worst case - Shatters compressor wheel or thrust bearing fails
3 - MAF revertions and system volume
This is not such an issue with a TMIC but when FMIC's are used the system volume is so large that when the throttle is brought back from power (boost) to cruise, if a strong spring DV is used (strong enough to eliminate issue 1 ) then you can get a sudden pulse of pressurised air back out of the MAF, this is measured as an airflow (the meter can't differentiate) and the engine overfuels giving a hicup/jolt
Best case - Slightly jerky drive as you come off throttle
Worst case - Very jerky !
4 - Repressurisation time
This is where the stiff spring DV or running without DV scores a point. The system holds more pressure between gearshifts as the DV isn't venting it. Boost recovery in the next gear is improved (slightly)
Best case - Improved response after a gearshift
Worst case - Issues 2 and 3 above.
5 - High pressure damage
If you use no DV or a high pressure DV spring then when the turbo is spinning at high speed and the throttle valve is snapped shut, there is a pressure pulse in the system
which can be high enough to damage the intercooler etc.
Best case - At boost below 1.5 bar you will probably be ok
Worst case - Bigger turbo's/ higher boost may pop hoses off or 'balloon' the intercooler core.
Options ?
A light pressure recirc valve (just like std) overcomes all of the above issues but sounds a bit boring
Sequential dump valve. At light pressure it recircs, at high pressure lift off it still goes Pssshhht
You pays your money, you takes your chances.
That bit must be the biggest load of crap i've ever read :lol: :lol: :lol: :lol: :lol: :lol:
Theres never going to be any more pressure going backwards than the turbo was producing in the first place :roll: You'd need a s**tload of pressure to "balloon the intercooler core" anyway :lol: :lol: :lol:
I think the guy was trying to give a conservative opinon covering all bases.... unlike yourself :lol: :roll: :lol:MarkTurbo said:
before you get upset I'm a supporter of the no DV philospophy too, have run without in the past and know many mates who've also de-BOV'd but it does have its limitations.
Agree that ballooning the intercooler core is pretty far fetched but his company are making 800bhp scooby's so when he says bigger turbos/boost he's thinking in a league Gti-R's aren't even considering.
You're right about the pressure being the same but he doesn't mean steady state but the pulse caused by the instant you "abruptly" close the throttle and the air has no where to go but is still being pushed in by the turbo. Again clarify this with the comment about big boost cars. A mates cossie split a hose at 2Bar, it does happen.
The writer is trying to cover all bases from std to 3Bar monsters and is the most considered reply I've seen to the issue in years.
Jim
I hear what you're saying 8)MarkTurbo said: