Throttle Bodies and MAFs LTx

[Fox Slaughter]

When is a bigger TB and MAF needed? Well lets go into the numbers here.

A 48mm stock TB flows 783cfm without airfoil.
821.9cfm with an airfoil.

Stock LT1 MAF will flow 719cfm with the screen removed (do not recommend).

So lets crunch some numbers.
The formula we are going to calculate engine CFM with is as follows.

CI x RPM x .5 x VE / 1728

So lets take a LT1.

350 x 6000 x .5 x .85 / 1728
= ~516cfm

So as we can see, a stock LT1 at 6000rpm will consume roughly 516cfm. The stock TB will flow 783cfm, still higher. The stock MAF will flow I'd say with the screens in probably +600 so still not a restriction.

Lets say your car is a beast and is 100% VE.

350 x 7000 x .5 x 1 / 1728
= ~709cfm

At the PCM limit of 7000 and a perfect VE which is not going to happen without boost, a LT1 will consume ~709cfm. So at this point, the MAF would become a restriction with the screens in.

Just some number crunching for thought. Cause bigger isn't always better.

[JoeliusZ28]

Exactly why i still have a stock throttle body

If i were to upgrade, id want a bigger lid and MAF as well.

[Fox Slaughter]

Exactly why i still have a stock throttle body

If i were to upgrade, id want a bigger lid and MAF as well.

Or be like me, I got my RC-5000 filter on, MAF delete and Elbow will happen tomorrow after work. So its going to look like a Ram Jet 350 under the hood.

502_Crate_Engine_350.jpg

Cause I have an Open Loop Speed Density tune.

EDIT: Great, turns out the RC-5000 only flows ~600cfm, the RC-5050 will flow ~1000cfm. Looks like I will be ordering a new filter.
Eh for my purpose it will work for now. I don't spin to 6000rpm so.

[JoeliusZ28]

You will probably notice as much difference with that as i did with my lid, assuming you have the tune right. Personally I'd prefer keeping the MAF, but thats just me. I've always had better luck that way but I also believe in building a perfect speed density tune before adding the extra precision of the MAF.

edit: what does an LS1 lid filter flow?

[Fox Slaughter]

You will probably notice as much difference with that as i did with my lid, assuming you have the tune right. Personally I'd prefer keeping the MAF, but thats just me. I've always had better luck that way but I also believe in building a perfect speed density tune before adding the extra precision of the MAF.

edit: what does an LS1 lid filter flow?

Um what part number?

33-2118 for KN.
I'm finding ~900cfm.

Could be wrong though. It was from some stupid shopping site, I would call up K&N or email them to find the exact flow.

[JoeliusZ28]

That could be right... I havent heard of an ls1 filter being a restriction for anyone yet

[c0ncEpT]

So as we can see, a stock LT1 at 6000rpm will consume roughly 516cfm. The stock TB will flow 783cfm, still higher. The stock MAF will flow I'd say with the screens in probably +600 so still not a restriction

For sake of conversation what your saying is you don't think a stock motor will make more power by adding a larger MAF and throttle body?

On LS cars porting the stock 78mm TB is worth 5hp and I'm sure in theory it would flow more CFM than you would calculate a stock LS1 uses.

[JoeliusZ28]

For sake of conversation what your saying is you don't think a stock motor will make more power by adding a larger MAF and throttle body?

On LS cars porting the stock 78mm TB is worth 5hp and I'm sure in theory it would flow more CFM than you would calculate a stock LS1 uses.

Good point Mike... Id like to try a bigger TB if i could get my hands on one, but they seem o be worth their weight in gold?

[Fox Slaughter]

For sake of conversation what your saying is you don't think a stock motor will make more power by adding a larger MAF and throttle body?

On LS cars porting the stock 78mm TB is worth 5hp and I'm sure in theory it would flow more CFM than you would calculate a stock LS1 uses.

No what I am saying is a larger throttle body is for something later.