Thread: Jetting with NOVI's.
03-21-2008, 10:09 AM #1
Jetting with NOVI's.
3 years ago when I was going through the pains and trials of getting to the 80mph gauntlet, I had one sticking point that no one could help me with.
Lowell porting, 1300 with triple pipes and the "package"..Nando and myself almost fought over jetting specs. His were totally different than mine, which I never figured out why except maybe there were small changes in Lowell's porting specs and differences in engine set-ups. Whatever the case..a quick call to Tim @ NOVI made the difference in rpm's and speed.
After the changes it was the fastest speed I had ever reached on Thunder (GPR) to date. 85.8 mph
Now I have a new challenge while building another big bore without triples but with NOVI's. NOVI's hit so hard it is crazy compared against other carbs. That it is the main draw I have to get NOVI's, they hit hard and whatever your engine has, it will let it breathe.
For some of you building triples with big bores here are my notes from that fast day in January 2006.
175 main 1 1/2 turn
120 pilot 1 1/4 turn
Stock pumps on carbs, RIVA f/a's, V-Force, 150 lbs. compression
Return jet 120 fuel pressure @ 8lbs.
7870 rpms with 2 gallons of fuel, half & half race/pump gas, MX2T premix 40 to 1
RAD 99.5% HP 103%
85.8 mph 800 grate/superman
Total speed package (Kerry) Nozzle one click up (zeroed in)
That was on 1/16/06
Just wanted to share the notes...Duke is helping someone get their NOVI"s dialed with triples and this stirred me to put this up.
Whenever you are dialing in any carbs, it is important to not just rely upon someone else's jetting specs but use them as a baseline to reach your own conclusions. It is always better to go fatter with mains then jet down, even if the ski chugs with too much fuel, smoking like crazy, you can always go down with jets. This is the best way to find your max rpm's and run safely with out sticking a piston.
BTW when I went from a 160 main to a 175 there was 150 rpm jump.
Last edited by Pistonwash; 03-21-2008 at 05:33 PM.
03-21-2008, 10:12 AM #2
Mike, I would like to make this a sticky. There has been some talk/questions and inquiry in the past with NOVI jetting and I think this would be good to have at the top since NOVIS are still around even with EFI growing.
thanks for sharing that
03-21-2008, 11:52 AM #3
03-22-2008, 11:21 AM #4
Great post Mike.Just curious,i run my Novi's between 5.5-6 psi, with a 110 return jet,how are you getting 8psi with a 120? I agree,i love the Novi's,they hit hard for sure.They will make your new ski come to life.
03-22-2008, 03:11 PM #5
I do not remember, but that was what was in the notes. I changed that jet a couple of times, it might have been an 80 or a 90. But, there was another day when I had the 80 in the return and 140 mains, the psi was around 10-11lbs.
It could have been because of the stock pumps too, I had been running just 2 externals until I switched to the stockers.
The main thing was to keep it between 6-8lbs. according to Nando, but Tim said 4-5lbs. Higher pressure won't hurt it either, just not too high.
03-24-2008, 12:57 PM #6
- Join Date
- Aug 2005
Your right mike, the novis do hit hard. Especially when they are working right. Im glad I have mine.
03-24-2008, 08:45 PM #7
"Whenever you are dialing in any carbs, it is important to not just rely upon someone else's jetting specs but use them as a baseline to reach your own conclusions. It is always better to go fatter with mains then jet down, even if the ski chugs with too much fuel, smoking like crazy, you can always go down with jets. This is the best way to find your max rpm's and run safely with out sticking a piston."
-What does this mean??? i am a lil confused
03-25-2008, 04:55 PM #8
I hope that clears it up. If you a mild mods done to your ski, there will be an overall consensus of what your jetting needs are. These are pretty uniform in there applications. But, when you start porting,pipes and different carburetors, this is where you need to be rich and work your way down. You can svae your engine that way.
04-04-2008, 04:08 PM #9
- Join Date
- Oct 2006
this is all very interesting and new to me, let me get this straight the return jet sizing is derived from the pressure reading you get from the fuel return line and the only way to measure this accurately is to get a fuel pressure gauge hooked up onto the return line???
the sweet spot is anywhere from 5psi to 8psi.....but no higher???
04-05-2008, 05:43 PM #10
I wish I knew how to make that diagrahm..it would be easier to cut and paste it up. I still have a copy in my note book.
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