Butterfly

Post by **VimyJ** » Wed Dec 18, 2002 9:02 am

Is there any reason why the butterfly valves on the J30 throttle body don't open a full 45 degrees with the accelerator fully depressed? Wouldn't this impede air flow at WOT?

Post by **Chally** » Wed Dec 18, 2002 9:02 am

Try checking the cable adjustment. Get someone to push the accelerator to the floor, & see if you can move it further by hand at the butterfly. If you can, then you have to take the freeplay out of the cable. I have even found pedals bent causing the same problem.

My Q was only getting about 90% when I bought it, & the extra 10% does help

Post by **VimyJ** » Wed Dec 18, 2002 9:02 am

Chally wrote:Try checking the cable adjustment. Get someone to push the accelerator to the floor, & see if you can move it further by hand at the butterfly. If you can, then you have to take the freeplay out of the cable. I have even found pedals bent causing the same problem.

My Q was only getting about 90% when I bought it, & the extra 10% does help

Nope. My cables are tight. I noticed this situation while I was cleaning the throttle bodies. When holding the cable cam back as far as it goes, the butterflies don't open the full 45 degrees. This seems to be designed into the system. I take it from your experience that you think that these valves should open fully. There seems to be a designed throttle body constriction engineered into engine. I wonder what purpose this might serve and if altering the stops could give some performance gains?

Post by **Chally** » Wed Dec 18, 2002 9:02 am

Seems as if that's the case for you engine. The manufacturer does, in some cases, leave full throttle a bit shut (so to speak). I've seen it on a few Jap cars.

Why???, probably for performance reasons.

It would be interesting to see what whould happen if you got the full opening, maybe it'd go worse,

but if you can do some changes, I'd be interested in the results.

Post by **VimyJ** » Wed Dec 18, 2002 9:02 am

Chally wrote:
Why???, probably for performance reasons.

The valves look like they're at least 10% closed at WOT. This would create a lot of turblulence at WOT. Perhaps this is desired? I am leery of messing with the OEM set up if we can't deduce why Nissan engineers would purposely set the throttles up in this manner. One consequence of altering the OEM stop would be extra rotation on the TPS. Maybe this wouldn't be a bad thing or maybe it would. Dunno.

Post by **Q451990** » Wed Dec 18, 2002 9:02 am

Be careful taking too much slack out of the cables... at least on the Q there's a little slack built in. Take it out and they'll bind giving you a lovely 1200 RPM idle. Also, make sure any adjustments are done after warm-up since the fast idle cam sets the lower stop higher when the engine is colder than operating temperature.

Not sure if all of this applies to the J, but stuff to think about.

Heath

Post by **Chally** » Wed Dec 18, 2002 9:02 am

VimmyJ, I think your corncerns are good. Depending on what TPS you have will determine if it makes any difference. A lot of Nissan TPS's only use the 3 stage one where it's Closed, for idle, nothing in the middle & Wide open, for full throttle.The other type is a variable resistor. This type gives a more accurate reading as to where the throttle position is. Some Nissans use both!.

If it has the Variable Resistor (potentiometer)then measure the resistance at WOT, so you have a base to go back to. Then you can try opening it up that last bit & see if there is any improvement.

Why I say "probably for performance reasons" is that it's embarrasing for a car maker having a sedan beating a more sporty version with the same motor.

Good luck.

Post by **VimyJ** » Wed Dec 18, 2002 9:02 am

I've been having a bit of a dialogue with a 300zx na expert who has performed the butterfly modification on his car. Other 300zx owners have made this adjustment and claim that it makes for another 9 hp in the na verson and 15 in the Twin Turbo with no drivability issues in over 20,000 miles. Hmmm.... Surely, the Nissan engineers had a method to their madness. But what?

A 9 hp gain in a VG30DE (albeit in the 300zx set up) is nothing to sneeze at.

Post by **mateo** » Wed Dec 18, 2002 9:02 am

VimyJ wrote:Nope. My cables are tight. I noticed this situation while I was cleaning the throttle bodies. When holding the cable cam back as far as it goes, the butterflies don't open the full 45 degrees. This seems to be designed into the system. I take it from your experience that you think that these valves should open fully. There seems to be a designed throttle body constriction engineered into engine. I wonder what purpose this might serve and if altering the stops could give some performance gains?

How hard is it to get to the throttle body on a 93 J30? I am someone mechanically inclined and I'm a DIYer. I need to clean them. However, I'm not even sure where to start. I have the owners manual but it doesn't reveal much.

Mateo

Post by **Mayhem_J30** » Wed Dec 18, 2002 9:02 am

mateo wrote:How hard is it to get to the throttle body on a 93 J30? I am someone mechanically inclined and I'm a DIYer. I need to clean them. However, I'm not even sure where to start. I have the owners manual but it doesn't reveal much.

Mateo

If you can open the hood, then you can get to the TB's.There's two of them. One on the left and one on the right. The black plastic intake system is hooked up to them.

Post by **mateo** » Wed Dec 18, 2002 9:02 am

What specific cleaner do you recommend. How often should this be done? I notice that a throttle body cleaning was recommended in some kind of recall or service suggestion for this car.

Post by **VimyJ** » Wed Dec 18, 2002 9:02 am

I clean them whenever the throttle gets "sticky". Pretty easy job.

Butterfly

Butterfly

Nissan Forums

Infiniti Forums

Datsun Forums

Technical Forums

Classifieds / Marketplace

Nissan Motorsports

General Forums