Normal to have to add fuel after LS1 MAF conversion?

[jskarateka]

Upgraded to new LS1/Translator(regular) from the stock MAF. Used the same 3in pipe and 9in cone filter and just fitted it with couplers. Left dial settings at 0 and set the switches per the instructions.

Wideband at WOT was about 11.0 before the swap and increased to about 11.7 after. Boost level was about the same at 23lbs. Was getting a little knock so I ended up having to add about 6% fuel to get the A/F back down to 11.0.

I know the TA49 doesn't have to work as hard now and that there is probably less back pressure, but I was surprised I had to add that much fuel. Is that normal? How is it getting more air at the same boost level? Is it just cooler air now? (Just trying to learn something)

Car seemed to run perfectly with the old MAF and the logger files were showing it maxed out at WOT like it should. Runs perfect with the new one as well and seems a little faster on the butt dino, but haven't been to the track yet this year.

Thanks guys.

 

[Turbo6inKY]

Yes.
The stock MAF is what, 2.5" inches in diameter? Stepping up to a 3" removes a restriction in the intake, assuming the piping is 3" everywhere else. Flow rate through a tube is a function of the area of the orifice and the pressure differential between the inlet and the outlet. A 2.5" MAF has 7.85 in^2 of area. A 3" MAF has 9.42 in^2, a 20% increase. A 3.5" MAF has 10.99 in^2, 40% over stock.

So yeah, opening the intake up that much will get more air into the engine and you'll have to adjust the fueling.

 

[jskarateka]

Yes.
The stock MAF is what, 2.5" inches in diameter? Stepping up to a 3" removes a restriction in the intake, assuming the piping is 3" everywhere else. Flow rate through a tube is a function of the area of the orifice and the pressure differential between the inlet and the outlet. A 2.5" MAF has 7.85 in^2 of area. A 3" MAF has 9.42 in^2, a 20% increase. A 3.5" MAF has 10.99 in^2, 40% over stock.

So yeah, opening the intake up that much will get more air into the engine and you'll have to adjust the fueling.

Thanks Turbo6.

Still very curious though. I get that it flows much better and easier into the turbo now, but if the manifold boost pressure after the turbo is the same as before, how is there 'more' air now?



.

 

[Turbo6inKY]

Thanks Turbo6.

Still very curious though. I get that it flows much better and easier into the turbo now, but if the manifold boost pressure after the turbo is the same as before, how is there 'more' air now?



.

Several things could be doing it. Restrictions put heat into the air charge. So you've lowered the temperature of the air entering the turbocharger. Denser air means more air at the same pressure level. You've also smoothed out the flow entering the turbo, which means it's going to move air more efficiently. If you could measure the RPMs the turbine was spinning before the new MAF and after, I'd wager it went down. More air through the turbo means it doesn't have to work as hard to create the desired manifold pressure, which also reduces heat.