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TOPIC: 2003 Volvo XC90 petrol 2.5

2003 Volvo XC90 petrol 2.5 24 Oct 2019 23:51 #1

  • Simon Burdett
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Anybody know anything about this vacuum thingy, and how to modify it for maximum fuel economy?

Thank you.

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2003 Volvo XC90 petrol 2.5 25 Oct 2019 11:22 #2

  • Ron Hatton
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Many of the vehicles I term "exotics" (BMW, Mercedes, Volvo, Peugeot, etcetera) often use a style of baffles inside the intake managed usually by vacuum.

Idling is low vac, and have longer runners and higher RPMs they are shortened. (I think!) Either that or the opposite.

The results on the effects of The Groove are the same. They act to break down the wave form that allows for complete vaporization. This is what I would look at first, and move from there to testing for vacuum leaks.


BUT DON'T STOP GROOVING to solve for this one! Some never see mileage gains, but the VAST majority do!
Ron Hatton
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2003 Volvo XC90 petrol 2.5 25 Oct 2019 12:16 #3

  • GregK
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thingy? that's the intake manifold. The throttle body/valve (and the Groove modification) are what's discussed most around here, but you will also find that "porting/polishing" the individual runners to each cylinder is popular on the web.

Idling is high or deep vacuum, with pressures significantly lower than barometric/atmospheric, which helps liquid gasoline vapourize more readily (you understand that only the vapour can burn, yes?
Fuel injectors atomize fuel, but engine vacuum finishes the process of turning liquid droplets to burnable vapour).

the throttle valve actuated by your right foot lets the engine's computer know you wish to generate more power, and thus to deliver more fuel (by allowing the injectors to remain open longer, presenting more atomized fuel to the airstream), which consequently requires more atmospheric oxidant to enter the arena to compensate and thus achieve the desired result. Unfortunately, in doing so, the ability of the engine to more completely vapourize the fuel is diminished. (take that to an extreme when a turbo is pumping more air into the manifold to feed the engine)

The brilliance of the groove is that it causes a turbulence in the manifold which mixes more fully the air and minimal amount of fuel present at idle/low throttle angles to run the engine with as much power as when you've commanded increased fuel+air delivery with your right foot. It relies on oxygen sensors to confirm and adjust the injector pulse duration based on a misinformed ratio of air to fuel, and MAF and MAP sensors to further calculate the mass of air and the vacuum which that air is being subjected to, and this is why I advocate taking measures to adjust their inputs to the computer. In your case, there is a point where the turbo actuates - when you increase the air going into the engine, you also have to increase fuel. staying away from that range (and in the Groove's zone) as much as possible will help you achieve mileage gains/higher fuel efficiency

I just saw your videos that Michael posted...great stuff (I wasn't sure where in the world you were, but now I see you're down under). also - as for those electronics we've discussed in another thread - if you've only one tailpipe and 5 cylinders, you've probably only one upstream oxygen/lambda sensor and one downstream. You would need at MOST two EFIEs, if I'm correct, but more likely a single one on the upstream sensor would do the trick, making it a much more cost effective (and adjustable/controllable) mod than the unit you mentioned.
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Last edit: by GregK.
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