Big Al

Let's hear some feedback from folks that have had their throttle bodies bored. I am considering having it done and would like an update. I tried posting this a couple of weeks ago under Care Talk & got limited response. Maybe the folks I need to hear from are here!

Could you tell a difference in performance? Are you satisfied with the bang for the buck with this modification? Did you have any problems with idle stability or the ECU? Any other quirks or is it perfect?

krazik

[QUOTE]Originally posted by Big Al
[B]Could you tell a difference in performance? Are you satisfied with the bang for the buck with this modification? Did you have any problems with idle stability or the ECU? Any other quirks or is it perfect?

ultimate lurker

Has anyone dyno'd just the TB yet? I ask because throttle body overbores are notorious for misleading the 'ol posterior dyno if you know what I mean. They tend to alter throttle response characteristics more than other mods (duh, right, it's the throttle - that's me, master of the obvious).

Anyways, I'm curious since there seems to be no rhyme or reason to which cars benefit from overbores and which don't (I've seen some cars with really restrictive stock TB's and lots of other mods gain nothing from overbores, and others with big TB's to begin with actually gain a few hp)

UL

The Reverend

I haven't done it, but I too am I little confused how this would make power on the S2k... at least on my car, where the TB meets up with the intake manifold, the transition is pretty flush, maybe .5 mm off. I'd think boring the TB more than just enough to smooth that transition will just make for a harsh transition. Like UL said, I think maybe this is just playing with your ass-dynomometer... But I'm not sure - I'd really like to see a dyno.

krazik

it is a tapered bore, also if my memory serves me correct the stock TB is 68mm and the bored one is 72mm, also it the replacement butterfly has a much lower cross section at WOT.

The Reverend

So the opening where it connects to the intake manifold remains stock bore, correct? What about with the spoon tb?

How much is the proflow and how much is the spoon tb? proflow requires a core, right?

Pinky

How does it work....less restriction and more air getting into the engine. The lower cross section of the TB make less turbulance. The tapered TB also makes for a faster rush of air like a funnel.

My butt-o-meter definitly says MORE POWER! I have done the K&N air filter mod(not much power), Mugen Headers(much power!), I also took out the radiator grill cover(power over 35mph!) That last one is honest to goodness true. I put it back in one time took it on the highway and it had less throttle responce and accelerated slower.

Is the TB a great bang for the buck? Ohhh yea!

ultimate lurker

No offense Pinky, but that's exactly what I'm talking about.

First, are you sure that a faster rush of air into the intake manifold is good? Remember that the engine is breathing from the intake manifold. Assuming the runner, ports, valves, etc. don't change, the key determinant in how much air you flow is the pressure differential between combustion chamber and intake manifold plenum. If you speed up airflow, then pressure goes down, doesn't it? This isn't to say that the pressure in the intake manifold goes down (I wouldn't predict that without a CFD simulation, and too big a throttle body can hurt power in some instances), but it's just something else to consider.

Second, reducing a restriction at the throttle body will only provide noticeable improvements in power if the throttle body is indeed the primary restriction in the intake tract. That may or may not be true for the S2000, but it's just one more reason that someone needs to dyno (Richard Ming just put the Spoon in his car and has a baseline, so hopefully he'll do it).

Third, on the replacement butterfly having a lower cross section at WOT. You've got to consider two things there. First the cross section and second the Cd. Some throttle bodies actually seem to flow a bit better if the plate is not quite parallel to the incoming air, perhaps because it tends to "hide" the shaft/screws the plate rotates on.

Finally, throttle body overbores change the rate of opening for the throttle in terms of area. A bigger throttle body will flow enough air at 10% throttle opening that it'll feel like the stock TB at say, 15% (arbitrary numbers for illustration purposes only). So your first impression when you hit the TB is "Wow, this thing has so much more power when I just touch the throttle". But in reality it just improves throttle response unless your engine needs more flow there.

Anyways, this is not to say the throttle body doesn't make more power. But Honda is pretty good at matching stock TB bores to the engine's needs (try Ford or Chevy and you'll be surprised how small they are). Thus I'd really like to see a dyno.

UL

E30M3

You don't even need a dyno. Just use a water manometer to examine the pressure drops in different parts of the intake. You can make one for like 5-10 bucks and they are SO accurate. If the stock TB is not a significant flow restriction, no more power will result.

But as mentioned above, the tip in will feel different. We'll call that change "UL approved". (haha)

Cuz a given throttle opening angle will pass more air when using a larger throttle plate. You can lose the ability to modulate if you go overboard. It's sorta like stepping on the gas faster and harder without moving your foot as much. Some Porsches allow you to change the throttle pulley cam the cable rolls on. In that case you notice the same change in throttle progression which has fooled people for decades. But once the engine is limited by something else, no additional air will pass. It's a weak link in the chain thing - if you only beef up the strong links the chain is not any stronger.

Stan

ultimate lurker

Indeed, a manometer would be a great way to correlate intake pressures with power gains. I'll bet I can get a nice pressure sensor for a Fluke multimeter and avoid the "trouble" of making my own manometer.

Last car I did a big bore TB on did gain power, but after a while I noticed that going past a certain throttle input the car didn't accelerate any faster, whereas before I had to put my foot to the floor to get full power. Just what you were talking about. The engine didn't need as much air as the TB could flow (that was a 6mm overbore, 2-4mm probably would have worked fine).

UL approved, I like that, think I saw it on a lamp once :-)

UL