71 mm throttle body

[BIGBULS]

Prove it kills low end.

 

Direct proof on the LQ1?

 

I have none. I WILL admit that.

 

 

 

However. There HAVE been a few cases of other cars losing SMALL amounts of power at VERY low rpm. Conventional wisdom says that larger TB's mess with incoming air velocity, and in effect "fatten" up the intake runners........and as we all know, fatter runners are better for high rpm power gains, rather than low. Still, from the way this has been explained, it's normally more of a throttle response issue rather than an actual power loss though (or at least a very small power loss). I probably should have stated that you would possibly have a *FELT* power loss at low rpm (a lazy throttle can sometimes give this impression...which is why the "butt-dyno" is so inaccurate).

 

As far as direct dyno charts, I have only seen 2 that DID lose any actual low-end (Probe GT [from a guy on Probetalk] and CRX [in an old issue of SCC]...only the PGT is even close for comparisons sake here [since the CRX is an I-4])..........

 

 

 

BUT.

 

 

 

I have still yet to see any TB's make any kind of MEANINGFUL power on ANY modern car/engine.

 

Take for instance the Hyundai Tiburon GT......

 

It has a 2.7L DOHC V6 with a similar overall configuration to the 3.4L DOHC LQ1............in other words, long intake runners, and a fairly restrictive exhuast manifold setup (and a smaller TB to start with). Hell, it even LOOKS pretty similar.

 

No surprise then, that the power curve looks VERY similar to the LQ1:

 

Here's a stock Tiburon GT dyno chart (with a chart of the same car + CAI overlayed on the stock run):

 

 

And here is a stock LQ1 chart (with manual tranny):

 

 

VERY similar overall curves.

 

Now.............I know this is kind of like comparing cabbage to cauliflower, but here is what a larger TB does to a Tib GT (over a stock car with CAI and NO other mods):

 

 

As you can see, not a lot.

 

And I can pull out a fair number of OTHER dyno charts from other modern cars (mostly I-4's I'll admit) that produce similar gains from TB's.

 

Sure, NONE are LQ1's (which is why I'm eagerly awaiting Vegeta's testing...even if I AM wrong), but if you see a consistant trend across the board, I'd think that the theory of larger TB's making only SMALL power gains has some pretty solid support.

 

 

 

Hey.........I think it would be great if a larger TB DID produce a bunch of power on an LQ1, but I think the odds are VERY solid that you are going to see 1-3whp, with slower than stock throttle response at lower rpm.

 

Just be sure that when you dyno them that the car is already AT operating temp for the first run, and that you keep everything else as consistant as possible from run to run (same amount of cooldown time etc). That will keep the dyno as consistant as possible.......

[dohc v6]

i got the plates made but can not find a shop to mill out the throttle body. does anybody know of a good shop that can do it.

[SleeperRed90TGp]

Bore the TB on a lathe. Short jaws or spacers. Chuck it by the back end about 3/8 deep but stay within the step. Bore the front to size. Turn around and hold by the front with long jaws. Bore the back. If its anything like the 3.1 and 3400 it has a step at the back that is larger than the bore. That being the case a little mis match won't matter.

 

This would be alot cheaper than trying to mill it or bore it on a mill. Takes the centering problem out of the equation.

 

Good luck

 

 

Jud