Just rebuilt my nikki. I decided since I had the intake off I'd remove the "sniffle valve"and port the intake. I had heard less it more with porting on the eom manifold so I just layed my intake gasket on there and port matched both runners to the gasket. Pretty minimal stuff. The ports on teh engine are still quite a bit larger than the manifold.

I am running a header, bumped timing, no cats and fancy DIY cold air intake. So I thought (like a fool) lets just bump up the jets a little on the secondary side.

They are #100 jets i believe. This came down to a 1/16th drill bit. So I just bumped the hole up to a 5/64th (next size up in my bits). Definatly pulls less when the secondarys open up now. I figured for sure I was starving the engine of fuel before. (plugs were whiteish if just cleaned and I shut the car down after a 3rd gear redline pull).

I thought these little rotarys liked lots of fuel!

Anyway just wondering what size jet you would reccomend and where I can buy them?

Thanks...

 

you should be running stock size jets on a stock motor.... Make sure you clean the jets out when you rebuild the carb or else it may lean out. It is designed to run a tad rich with stock jetting IIRC. I have a near free flowing exhaust with a header and intake, haven't had any problems with leaning out.

 

I soaked and blew out every jet with shop air. Clean as a whistle in there.

Anyone have a WB02 setup? It just seems odd that with a ported intake and full exhaust that the engine wouldn't benefit from a little more fuel?

Although I only went 15% or so richer (on the secondary side only) the car feels a bit piggish. So your probably right. Still, anyone know where can I get some stocker #100 jets from? I screwed mine up


Thanks!

 

That was a huge jump ~56% bigger. Get a numbered drill bit set before you try this again. Those jets aren't junk though. You can use them for tuning just solder them up and drill then again. Champher the inlets and debur the outlets with a larger drill bit. It is best to use a pin vise and some vernier calipers.



Percentage increase = 100*(Dfinal²-Dinitial²)/Dinitial².

Try 5% or so... like a #52
1/16" = 0.0625"
SQRT(1.05*(0.0625)²)=0.064
#52 = 0.635"

Here's a drill chart:
http://www.carbidedepot.com/formulas-drillsize.htm

 

Not sure what you refer to with the #100 denomination, but the secondary jets are 160 for 1.6 mm or 0.062992126 inches, 0.063 for short or 63s.

You can buy them at Mazdatrix.com.

 

The stock secondaries are actually quite large. It's the primaries that are small. I tried switching from 92 to 94 and it helped a little. I left the secondaries and air bleeds alone.

 

I'm not sure what your talking about. The secondary jets on my 85 are #100's. They have the "#" sign and 100 stamped on them.

It was a snug fit but I could slide the base of my 1/16th drill bit through the stock jet. A 1/16 bit is .0625 a 5/64th bit is .0781. Thats sure not a 56% increase??? It's a .0156 increase per side?


I'm confused!

 

Look again. I think the first "0" in "100" is actually "6". 160.

btw, .0781" = 1.98 mm or 198, HUGE for secondary jets on a stock engine.

if you were to go for a size up, they're available in .05 mm increments. Like the next size up is 1.65 mm, or 165s = 0.0649606299, or 0.065 inches, or 65s.

So jumping from 160s to 198 is going up 8 sizes on the jets!

 

Sorry to confuse. 56% increase in jet flow area. Flow area is (Pi*diameter²)/4. It is best to think of jets in these terms since they are flow control orifii. 56% more jet area would flow something like 56% more fuel. Not exactly, but you get the idea.

Could you list all the jet sizes you are running so people can tell you how you setup is different? Primary and secondary air and fuel.

Also, I left a 0 off in the size of the #52. I meant 0.0635.

 

I'll solder them up tonight one way or the other...

I posted up here for a jet change question.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/nikki-jet-change-wtthout-removing-carb-598078/

 

The solder trick worked great. Slapped the 1/16th bit in the drill press and went to town. I got my HP back! Maybe even a little more... Made sure to debur and contour the jets as stated above.



Just on a side note when I ported my intake and removed the butterfly after fire valve. I went ahead and cut grooves in my intake like so...



https://www.rx7club.com/1st-generation-specific-1979-1985-18/cutting-grooves-intake-manifold-555308/

I'll post up any MPG gains or losses over the next week or so. I must say I'm impressed with the idle. I'll be happy to video tape it for the non-believers but with the car warmed up I can idle smooth as silk at 350rpm. Not that this is necessary for any reason but the car wouldn't do it before. It is definatly ALOT smoother. Where the engine would idle around 800rpm or so before it shook. Now if I were to video tape it and cut the sound you wouldn't even know it was running. Engine sits dead still.

Thanks for the jet help everyone!