New intake plenum

[Jason84NA2T]

This plenum was made by LP Performance. After I did the testing, they gave me the option of buying it at reduced cost instead of sending it back (because it was used). I was going to just put it on ebay, but decided that with some elbow mods it might really move some air. A 3" aluminum pipe was cut and welded in place of both the elbow and step in the back of the plenum. It now maintains a full 61mm at the TB opening and tapers to about 69mm which continues all the way into the main chamber.

Just my experience here, NOT a TB debate: I installed the 60MM throttle body and the throttle was so touchy I almost could not drive the car. If I simply touched the throttle with my foot it will be at 2000rpm instantly. The engine revs so fast to begin with, that the larger TB only made it a pain in the ass to drive. I could not maintain speed on the highway very easily, I was always unintentionally revving way too high on takeoffs, so I swapped back to a stock 52mm unit and it's fine now... I noted no difference in performance otherwise.

The plenum on the other hand, I did notice a small difference. It seems like power delivery below 4000rpm is enhanced, and the engine revs much more freely with very light load. This is kind of the reverse of what I expected, but I suppose that step in the back was doing more harm than good.

[Steve88t]

Sad you're starting to reach the point where too much is just....well too much.

The increase on the low end may indicate that the elbow was simply too much of a restriction period. High, mid, low, whatever.

[G-E]

I especially like the vacuum panel

but yes you removed the one major restriction in the intake, and the air will flow and flow.... the airflow change at the low end could be adjusted by using a radially increasing half-moon for the cable so the same foot movement gets progressively more throttle opening... they do this kind of thing on hondas

just for the physics challenged: having a small orifice doesn't create nearly the same restriction as a smaller diameter of tubing assuming there is sufficient force pushing the air through it, however in a vacuum or low force/pressure scenario it is the opposite and the restrictor can cause more restriction than a smaller tube section

the caveat for the above being shape, shaping can change the whole dynamic

I wonder how the airflow change for tps setting would affect an automatic car.... the shift/load/kickdown points would be entirely different from the power delivery

[MikeZ]

You took care of that issue.

[OR-Zman]

GE-
I follow your logic on the tubing vs orifice size and the differences between forced and NA applications.

However, what would your thoughts be as to using a radially increasing half-moon on an NA with the plenum Jason posted? (stock TB or 60mm but I was thinking stock) I thought of it but really wasn't sure at all.

Here is my thought. I have an L&P plenum on the way and had the same idea Jason did (I had no idea what he was up to)...open up that neck after the TB. I havent gone past the thought stage because Lee is finishing the plenums still, (he is port matching the lower as well) but...this subject dovetails nicely with what I was already thinking.

Here were thoughts, but now I have to get another chassis to work with to get this done :evil: :

Open up that intake elbow similar to what Jason did and modify my current intake piping to help make the bends as gradual as possible. Taper from the stock TB to the 3" elbow much like Jason did. My thought being that reducing the total degrees of bends between the filter and the plenum is a good thing and where bends are required then make them as gradual as possible.

I came up with this idea/thought process while installing the new intake tubing but I could very well be off base when it comes to an NA.

Guys:
I appreciate any thoughts other than 'turbo it' because I have already made that decision. Yes, I often take the road less traveled and yes I know the conventional knowledge on this whole NA subject...just humor me if you would. :wink:

[G-E]

toblerone you yourself know fueling and afm readings are what determine his power and if he tuned it correctly for one plenum then the engine afrs shouldn't change more than .1 (the rising of boost, afm metering and fueling lag)

no he's just ingesting too much air at part throttle

or-zman: I think if you cut off the back of the plenum you could possibly get a full 90 degree 3" mandrel bend in there and have the t/b in roughly the same position as stock, just before you reach where the "hump" is you flare outwards to meet all the sides of the rest of the plenum.... should be very nice, make sure the new tube has a trumpet shape into the plenum, if you don't you could potentially starve the nearest cylinders of air, a curved wall will laminate some air to the sides of the chamber and slow the air velocity so it won't be such an issue

[SteveZ]

This thread will not turn into another throttle body debate, I'm just sharing my experience with it

This mess of a Thread has been swept up

Crowbar your pissing me off start a new thread and argue in circles with yourself

[crowbar]

Jason84NA2T wrote: My other 60mm throttle body is being used right now. I plan to swap back to it whenever I can take it off their car. The current one came on a car and appears to have the 240SX linkage? My old one had the Z linkages and didn't have this issue, it also had cruise control. I'll try that before swapping back to the stock tb.

I already have the throttle stop adjusted to control idle speed. Yes, I can see the rapid change in terms of vac as well as how quickly the engine revs.

yeah, I would just use a vg30e compatible throttle body. No debate from me.

PS This thread had more moderators than posters? Thats odd.