Is this a common modification on N/A engines and are any advantages measurable?

Cheers

 

very minimal advantage (its along the lines of throttle body porting) and alot of people tell you it really isn't worth your time but, I have done it along whith porting my throttle body removing the old screws and countersinking new ones and grinding off the excess threads that stick out the bottom along with grinding away a small amount of the rod all too increase the maximum area of the throttle body and i ported the throttle body and knife edged the butterflys. In my opinion it is worth (every little bit counts when your NA)

 

I havent heard of it before this post; in itself it probally a very minor mod, but if you find different minor things like this it will add up to several horsepower before you know it.

Like the saying 'Focus on the ounces and the pounds will follow'

 

can u explain more rotary84autox ?

 

Throttle body port, knife edge backside of leading edge of throttle plates, contoured secondary shaft/half shafted primary shaft, countersunk screws.

Here is my FD TB, but same ideas.

 

The only thing I noticed was crisper throttle response, but it could have been my solid motor mounts.

I'd like to see a dyno sheet someday to see how much this mod does or does not do.

 

check out this link has pics along with a dyno graph

http://bdc.cyberosity.com/v/Throttle+Bodies/

 

Thanks man! That's a nice gain, but it's not on an N/A which is what I was referring to. I'll be sure to do the throttle body mod when I get a TII of my own.

 

at 6000 rpm there is nearly 100HP and 100ft*lbs gain from just a modified throttle body? I think thats quite optimistic. Those dyno plots are 8 months apart and there was likely alot of tuning, and other improvements in there. I would take that "evidence" with a grain of salt.

Not to say its a pointless mod, but dont expect 25% power gain from it boosted or not.

 

The dyno sheet says "after break-in, tuning and throttle body mod." I would have to believe the majority of the increase was from the tuning.

If it was only from the throttle body mod (better flow) then you would see more gains higher in the rpm band. That sheet has better power all around.

 

I'd like to comment on this seeing as how I partially built and tuned the car in question as well as did the throttle body. The tuning? There virtually was none by then. There was certainly nothing changed on spark advance or base timing that would suddenly yield loads of torque. Basically, the throttle body enables the turbo to hit more aggressively and a bit earlier in the RPM band. That translates to peak torque being achieved earlier which explains the difference between the two torque curves. The actual peak power isn't much higher at all (I think 15-20hp?) but it did hit 400hp 1000rpm earlier than it did w/ the stock TB. Even though his car is a higher power output one, it does display the difference the modified TB gives. All of my customers as well as those that've done it on their own all pretty much say the same thing -- boost hits harder, car feels quicker and more responsive, but no real major increase in actual peak horsepower.

Hope that helps!

B