N00b-type question: Does a VTA DV affect fuel consumption?
12 March 2003, 10:59 PM
#3
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Yes, it affects fuel consumption. Would you notice it? No, probably not - the amount of fuel used to compensate for the metered air you just threw away isn't that large compared to a wot run.
Richard
Richard
13 March 2003, 07:55 AM
#4
I've heard a lot of people say it increases fuel consumption because the cars run rich on lift off but i've never been told a good reason. Personally i don't think it does (apart from when you first get the DV you thrash the car everywhere to here the psssssst). The air flow meter measures the amount of air that goes into the engine..... the ecu then adds the correct amount of fuel for this air. However when you lift off some of this air gets VTA so the car runs rich because it has less air and NOT more fuel. The only way it would use more fuel is if in some way the DV made more air flow past the MAF..... this it will not do.
Tony.
Tony.
13 March 2003, 08:12 AM
#5
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Thread Starter
Many thanks to the replies..... and now to my next question.....
....I just received a red (stiff) and a yellow (not as stiff) spring in the post this morning from Forge (top support there
)
Which will give me chatter, rather than woosh?
If that makes sense? lol
....I just received a red (stiff) and a yellow (not as stiff) spring in the post this morning from Forge (top support there
)Which will give me chatter, rather than woosh?
If that makes sense? lol
13 March 2003, 08:12 AM
#6
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The ecu is expecting that metered air to be present in the intake, added in behind the MAF everytime the the bov operates. Its not much but it does cause richer than normal a/f when you dump that air to the atmosphere.
13 March 2003, 08:50 PM
#7
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Er...Tone...you are way off there, mate.
As mlambert says, the factory system is a closed loop. So the MAF only meters air going into that system. When it gets re-circulated, it is not re-metered, so the ECU assumes it has x amount of air in the system.
When you fit a VTA, you "blow off" a bunch of charge to the atmosphere. This means there is now less air within the system, so more rushes through the MAF. The ECU sees this as the engine needing more air on top of the air that it thinks it still has (it doesn't know you blew it away) and so assumes the engine is sucking in more air and adds a little fuel to keep the mixture rich.
As mlambert says, the factory system is a closed loop. So the MAF only meters air going into that system. When it gets re-circulated, it is not re-metered, so the ECU assumes it has x amount of air in the system.
When you fit a VTA, you "blow off" a bunch of charge to the atmosphere. This means there is now less air within the system, so more rushes through the MAF. The ECU sees this as the engine needing more air on top of the air that it thinks it still has (it doesn't know you blew it away) and so assumes the engine is sucking in more air and adds a little fuel to keep the mixture rich.
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