alpine003

You mean stock TB is 74.6mm? IIRC, my IPD was the same diameter as the stock TB opening. Pics of the ported IPD?

Also, I'm assuming you're going through Maxbore porting services which I also plan on using. FWIW, they've been in business for years and have ported a few of my TB's over the years. Never had any issues yet.

geetee

The stock non egas TB intake side is 74.6mm. TB manifold side opening is 77.5mm. My IPD was 77mm.
I used a dremel and opened it up to 79mm removing some of the orange coating that IPD has on the inside.
Yes, maxbore will be doing the porting.

geetee

I'm going to see how wide maxbore is going to go on the TB manifold side. I might have to port the IPD a little more but I'm getting close to the gasket.

alpine003

Thanks for the clarification. Yeah I'm also wondering how close I should get to the gasket.

geetee

Sorry for the crappy pic. I'll post more after i get my TB back and see if I need to port more.

onefastviking

Yes, I have used much larger GT3 TB's. The hp was minimal but did help, it did also move the tq curve a little, but the main thing to remember is that I did this on a non street car with multiple other mods. So your results on a street car will be different.

An engine is really simple, it's an air pump, more air in while more air out, makes more power.
Just more air in, will not necessarily mean more power. Many times it may make less power, this is why some see no gain with IPD. The key is knowing the weaknesses in where the restriction is and then modifying that to flow more air. Stock they are pretty matched up well, I think Porsche may have spent some money in the R&D dept.

Now if you've added headers,no cats,open exhaust, flowed your heads, or up'd displacement, by all means, add the TB, it will probably help.

Both JR and I run some bastard combos for the race cars, it works for us in our specific applications but neither of us JUST have a TB alone.

alpine003

Do you know if the mounting holes for the GT3 TB line up with the stock C2 plenum? I've thought about going that route but the only thing holding me back was the mounting issue.

onefastviking

No, you will also need to change the "T", as well as deal with the larger hose to the airbox, as well as possibly a vacuum line difference depending on year/ model. The easy way would be to get the "Race or Comp IPD" pleanum which makes it a bolt on. But then you are changing too many parts to know which one will be what gains you or losses you any power. Also keep in mind that porting your stock one does really change the flow a lot, be careful here.

alpine003

Thanks for the clarification. And yes, one of the reasons I want to stay with the stock is the minimal increase of around 2mm should be more compatible and less overkill than a gt3 setup, especially without having any kind of cams and headwork.

b8_rdc

Anyone who wants a New IPD plenum for an e-gas car PM me.

I will throw in an e-gas pedal for anyone thinking of doing a swap.

geetee

So, I got my TB back. FVD advertises as stock TB 74.6mm and enlarges to 76.4mm(1.8 increase). I have a feeling this is measured at the intake side opening?
My TB was measured at the narrowest point, the butterfly area. Stock measured 73.5mm. The butterfly was increased to 76.4mm(2.9 increase). The intake side opening size is right at 76.4 or .1 or .2 larger.
I wasn't able to drive around much as moderate rain where I'm at but observing 70-80% throttle up to 5k rpm's, throttle response is definitely noticeable. I'll report more after the weather clears up.

alpine003

Great to hear but my measurement came to 74.6(eGas) at the butterfly opening, however I did notice yours was non-eGas.

It would be interesting to see the effects after adaptation values have changed over time.

Any pics of the modified TB? Did they use the same material as OEM for new butterfly plate?

Unfortunately, I have to wait until George returns from vacation to do mine.

geetee

Maybe egas difference? George's measurement was 73.5(I didn't measure butterfly before sending out).
Sorry, I didn't get to take any pictures. I was busy reinstalling the IPD(such a PITA). The IPD was open up slightly larger than the TB manifold side. Also, cleaned up all the oil on the IPD and replacing the coupler hoses. I'm not sure on the butterfly material.

Tbred911

Let us know your air fuel ratios with the modified throttle body. Some say lean conditions are possible in the upper r band

Best is to throw it on a dyno once you've had a chance to drive it around and do a few pulls to make sure your not running dangerously lean.

Flat6 Innovations

Until we make serious internal mods we see very small gains from adding larger plenums/ throttle bodies and etc with these engines. In my experience those things generally create more negatives than positives. I start to worry about optimizing this when my 3.4 based engines are taken to my Gen3, 3.8 specs, or a 3.6/ 3.8 based up to a 4.0. At this level things start to make enough of a difference to tweak the induction, below this point I simply don't see the returns from the modifications being great enough..

Opinions will differ. Results will vary.