Placing a screen under the throttle body

[Reishi]

In my constant quest to get better gas mileage in my 94 chevy truck I often ring up engine performance to mechanics that I run in to.

Well, an older man that I ran into told me that I should get 2 throttle body gaskets and place a wire screen from lowes in between. Making a sandwich out of the gaskets with the screen in the middle. I thought that he was just kidding with me but he swore up and down that this was an old trick to use on TB's because the screen will cause the gas to spray out into thinner molecules before it hits the combustion chamber.

Before I waste my time making this contraption does anyone see any benifit or possible problems if I do this? Has anyone ever heard about this before and does this contraption make any sense at all?

Thanks in advance,
Reishi

[Erik]

I am doubtful that it will help. The gasoline will atomize when it is sprayed out from the injectors.

I would think that if it would really help, car companies would already be doing it on FE cars like the Prius, Yaris etc..

[RoadWarrior]

Aluminum window screen has been known to oxidise and break up getting into the motor, so would be better to find some good quality stainless steel mesh. This was an old trick for carbs, which tend not to spray so good as TBI does. The idea is that it catches the bigger droplets, or busts them up and they evaporate off the mesh in the airflow. Is reported to work well on some vehicles, maybe lose a touch of throttle response if the mesh is restrictive. May work well in combination with a "warm air" intake. Haven't tried either myself, just have MPFI vehicles to play with, so this is just stuff I've picked up by osmosis hanging round fuel economy sites for years.

[RoadWarrior]

Originally Posted by Erik

I would think that if it would really help, car companies would already be doing it on FE cars like the Prius, Yaris etc..

Modern higher pressure injection systems have a better spray pattern, so those would definitely not need it. TBI is typically lower pressure, around 9-15 PSI and droplet pattern is often rather coarse.

[mustngr]

Ditto. Usually results in fuel "pooling" on the mesh, yielding goofy throttle response and a host of other issues.

The idea was sound in certain carb situations, such as on race motors where atomization was less than optimal and the motor spent a lot of time at WOT.

[Reishi]

Thanks for the responses.

The guy I talked to was certainly a good mechanic in his day but I don't know if he knows much about the newer vehicles. Although he did say that he did this on the same model truck that I have so I guess I could give a try and measure its effectiveness over a few tanks.

[lunarhighway]

i was looking into mesh behaviour for a totally different reason (grillblock) but it turns out a fine grit will smooth out airflow and destribute the pressure over it's entire surface.

and the flow will remain straight for some distance after the grit after wich it will go turbulent again. so perhaps the grit will even out the turbulence caused by the throttle valve. on the other hand it might cause a slight restriction wich would cause you to run higher throttle setting for the same airflow.

if this guy has tried it as says it's successful i'd sure give it a shot... i don't see any huge problems this could cause if it's carefully constructed out of the right materials.

[Pete]

Mesh screens are used to help even out the flow and pressure variations in the throttle body intake tract , especially where the butterfly can cause disrupted flows.

Not seen so much these days as most engines are multi point injection.

Cheers , Pete.

[Reishi]

I went ahead and made the contraption and placed it under the throttle body this afternoon. I took the truck around the neighborhood and it feels really responsive. Almost like it isn't struggling as hard to get up to speed. However, this may be wishful thinking though so I measure any difference over the period of a few tanks of gas.

I generally average right at 11.5 mpg so I am looking for anything to help.

[SD26]

The screen obviously reduces the area of the intake. Might just help increase the intake velocity. I've seen that done with epoxy on some racing motorcycle intakes.

Looking forward to your follow up.

[Lug_Nut]

The doubling of the gasket is probably more a contributor to the seat-of-the-pants improvement than any restriction you've added.
You've begun on your way to creating a 'high-rise' manifold, a long known performance enhancer.

[Reishi]

Well, I already have a TB Spacer under the TB. I placed the screen under the TB spacer.

I am looking forward to seeing how this pans out as well as I am barely able to afford gas for this thing as it is.

[kamesama980]

Originally Posted by SD26

The screen obviously reduces the area of the intake. Might just help increase the intake velocity. I've seen that done with epoxy on some racing motorcycle intakes.

Looking forward to your follow up.

That's a completely different thing. the screen will increase velocity for the franction of an inch of it's thickness but the air will slow down again as soon as it's past it. using epoxy in the manifold/runners is to eliminate dead space and therefore eddies in the air as it flows through. it keeps the velocity constant and reduces destructive turbulence

[101mpg]

And then again, you would think that car companies would be shipping the European and Japanese more fuel efficient versions of the same US cars we have right now but they can't manage THAT either.

Originally Posted by Erik

I would think that if it would really help, car companies would already be doing it on FE cars like the Prius, Yaris etc..

[red91sit]

Interestingly enough, a college used this trick to convert a car to run on Ethanol, this, as well as a bit of heat made the ethanol atomize to combust even on the coldest of days. The only problem i see with this ( as well as on mechanical injection systems" is that an intake block, will make you have to open the throttle more to get the same power, but with out an o2 sensor (i have one hehe) it will not know that it is getting less air than it usually does at this throttle opening.... Rich booo.

[Reishi]

So should I invest in one of the O2 sensor trickers?