Hello guys,

I have 2 questions. that could spawn into many questions....

does any one know the actual size (mm) and flow rate (cfm) of the stock L31 throttle body?

Thanks,
Joe

72mm if I remember correctly.

okay so according to the net.. 72mm should flow about 700-750 CFM.. if you have a forced induction unit that will produce 1000 CFM are you creating a huge bottle neck using a 72mm t-body? Assuming the engine wouldn't blow up at 1000CFM would you see an increase of power going to a larger throttle body?

Depends where it is. If it's turbo or centrifugal you have pressure blowing through. Air under pressure is more dense and will move a greater volume through the same area.
Even with a roots or twin screw it's a negligible factor too. Consider this - at WOT naturally aspirated you'll see manifold pressure reach nearly 1 BAR. There will be only 1 or 2 psi difference between atmosphere and manifold, so imagine that it's only taking that much pressure to flow the air through the TB. Add a supercharger and you've got greater vacuum behind that throttle body. The super charger could create a difference of 5 psi between its intake and atmosphere, for example. Even though minimizing restrictions into a supercharger inlet is always worth the effort you can see that it really isn't mandatory to upsize the throttle body when working with forced induction because you have a mechanical advantage moving more air through it.

So, there is some benefit... but in reality the turbo/blower should force the same air flow.

I have "heard" that in a forced induction application, that reducing restriction before the compressor can make a bigger difference. So if a setup is a suck-through or draw-through setup, the t-body restriction is more important than a blow-through setup.

I remember 1 of the aftermarket F$@D Rustang air intakes claiming a 53 rwhp gain by using a low restriction air intake on a suck through DOHC forced induction setup. Even if there was actual gains 1/2 of the claiom, that is still impressive and sort of illuistrates the sensitivity of forced induction applications to air intake restrictions.

I seem to remember the L31 t-body measuring around 72-73 mm as per Ken K1500 383. I remember him measuring the inside diameter of the L31 t-body with a homemade caliper setup.


Be sure to remove the EGR difusser 1/2 moon device on the backside of the t-body blade as well.
I drilled out the 2 rivets, removed teh blade, and re-rivetted the 2 of the 3 remaining holes. 1 hole is meant to be left "open" as it functions to aid in a stable idle.

peace
Hog

Hog wrote:

Be sure to remove the EGR difusser 1/2 moon device on the backside of the t-body blade as well.
I drilled out the 2 rivets, removed teh blade, and re-rivetted the 2 of the 3 remaining holes. 1 hole is meant to be left "open" as it functions to aid in a stable idle.

peace
Hog

I ground the half moon off mine because the riveted plate has a smaller hole than the butterfly valve and heard the larger hole causes idle problems...

CrazyHoe wrote:

Hog wrote:

Be sure to remove the EGR difusser 1/2 moon device on the backside of the t-body blade as well.
I drilled out the 2 rivets, removed teh blade, and re-rivetted the 2 of the 3 remaining holes. 1 hole is meant to be left "open" as it functions to aid in a stable idle.

peace
Hog

I ground the half moon off mine because the riveted plate has a smaller hole than the butterfly valve and heard the larger hole causes idle problems...

Really?, that's interesting. I didb't even realize that the 1/2 moon thingy had a different diameter idle hole in it.

peace
Hog

I guess that makes a difference for ppl with stock injection/pcm. I just didn't want to take a chance at the time.

The lip was the first thing I removed when I got my truck.. way back before I even was dreaming about moding it.. I did a throttle body cleaning and noticed it was there. I thought it was screwy and I ground it off right away, I used pop rivets to seal the holes and ground the rivets down.

http://www.summitracing.com/parts/SUM-227727/?rtype=10

does any one know if this will work with my stock IAC motor and TPS or will i need to buy Ellsis juan parts (LS1)

Thanks,
Joe

tagging along

bump,

has any one changed to an LS style Tbody like this http://www.summitracing.com/parts/SUM-227727/?rtype=10 will the stock IAC and TPS work with it?

Thanks,
Bowtie

I know that the L31 TPS is the same as the LS style TPS (same part number). The IAC's are different. I bet with tuning it could work.

thank you,

I ask because its an additional cost on top of the throttle body that i want to be ready for when I order. and it could potentially justify the purchase of a used one at the right price.

Janzer makes a great ported TB that will not break thr bank...high recommend him...Find him on Ebay

I have an L31 throttle body that has been polished and opened up a bit. If you are interested, pm me and I'll send pics....