Alright...I've heard alot of controversy about this. In the future I will be getting a bigger throttle body, not now, but I'm trying to figure out which one I want. I heard that if you're thinking about getting an intake manifold extrude hone, you might want to go with the 60mm. Now I've heard that the bigger you go the more you loose on the low end, which I'm trying to improve. But I also heard the best bet is to go with the 60mm if you're going to be doing alot of mods, which I am. Pretty soon I will have a header and exhaust system, and for the future I will have, of course, a performance throttle body, the extrude hone intake manifold, like I mentioned, cams, injectors...pretty much everything. So what are your opinions on this?

 

ugh i dunno why that myth continues to persist... you wont lose any low end. go straight for the 60mm throttle body.

heres KeithRT's dyno comparison:
mods at the time of the dyno: 98 R/T, mopar ecu, auto tb, pacesetter header, UR udp, iceman. Auto TB vs. 60mm TB


show me the loss?
go straight for the 60mm.

ive also seen other neons, in various states of "tune".. also post very similar results when just swapping throttle bodies.

 

I got the mtx, so would it actually do better than what you are showing me because of the restriction they put on the mtx, because I would be getting rid of that restriction?

 

That dyno is from an R/T, which means it is an MTX... The comparison is between an ATX TB and a 60mm TB. The only difference between the stock MTX and ATX TB's is the MTX TB tapers down to 49mm in a venturi shape (well, plus the TB spring and cam...).

We're talking a difference of less than a HP here, so the question is how much is it worth to you?

If you've ever taken apart a stock DOHC intake manifold, you'll notice that the hole coming from the TB neck is so small that a 52mm butterfly plate won't fit through it. That's the main restriction point, so putting a 60mm TB on a stock manifold equates to putting a 4" tip on the stock muffler... Yes, the 55mm and 60mm TB show gains, but again we're talking 1 or 2 HP, which could be nothing more than a change in the a/f ratio caused by a slightly less vacuum and/or lower temp seen by the IAC/MAP. You see the same gains going from a stock air filter to a K&N drop-in replacement. Same gains by removing the weatherstripping at the base of the hood to reduce underhood temps.

As much as I disagree with a lot of Gary Howell's performance theories (like the theoretical loss of low-end torque because of a larger TB... carryover's from carb performance that simply don't apply with electronic fuel injection), at least take a look a the Neon performance page at allpar.com. Keep in mind that the odds of you acheiving 100% Volumetric Efficiency on a streetable car is practically nil (figure closer to 85%, even on a well-built street car), and the odds of you pushing over 225 HP naturally aspirated are nearly as slim. The 55mm will do fine on just about any 2.0L naturally aspirated car. The 52mm (ATX) will do fine for most people, particularly anyone running the stock DOHC intake manifold (I plan on cutting apart both the aluminum and plastic SOHC manifolds later this year, so measurements on those will have to wait...). Nate Greer's 13-second SOHC ran with just an ATX TB (and PaceSetter header, and full interior).

You aren't going to hurt anything by going straight to the 60mm, so it's really a matter of what your realistic goals are and what your budget will support.

 

Yeah but if you're getting other things that will go along with the TB it might help a little more than 1 or 2 hp.

What I meant was since the auto Tb doesn't have the restiction from the cam that you would see less on that dyno test then comparing an MXT TB vs a 60 mm...know what I mean???

 

just to add another dyno comparison, in a slightly different state of tune.. here was Nick Riley's tb comparison: 60mm blue, 52mm atx in red

again, the 60mm comes out on top, this time at 5whp peak.

considering the atx tb is usually noted as a 2-4whp gain over the mtx tb.. yeah, if those dynos were the stock mtx tb, the gains for the 60mm would be a bit more in comparison.

while most people will often say that going from a 55mm tb to a 60mm tb is almost pointless and youd notice little to no gains, i would beg to differ. while i didnt dyno it, when i went from a 56mm tb to the mpx 60mm, i felt nice gains with the 60, as well as noticably better throttle response. the gains i felt tho, i didnt dyno so im not sure on how much of a gain i got from it.

 

Thank you, yeah that's what I was asking

That's what I want the most...throttle response. But when I get the TB I will be extrude and honing my manifold so hopefully I'll feel a little more.

 

youd be better off getting the manifold ported and polished than extrude honed.
the EH doesnt remove as much material as a nice hand port and polish job will.

 

Yeah I was looking at a company that does that. It costs a little more but my dad convinced me to do it. He says it's worth it. I agree because they say that the biggest restriction on the neon is the intake manifold

 

who ya lookin at getting your intake manifold ported and polished?

myself, i recommend either sending it to NRGYheads.com ... or Eddie Fierro (fierroracing.com i think?)

both do excellent work and well worth the $$

the biggest restriction in the stock dohc intake manifold is the area under the throttle body, mainly where it bends to meet the plenum. its smaller than 52mm at the opening. porting and polishing will open this up MUCH more than an extrude hone job will, and thats a good thing