Just bought and installed a Ron’s terminator setup on my 421 SBC. Trying to learn a little about the nozzle jets and bypass pills. First week out 33 nozzles 86 bypass car was way rich and started missing around 500’ out. 6.36 and ended up 6.27 so I’m getting there. I started leaning it out and the miss stopped at 115 bypass and ended up racing with a 125 and it was still rich. Called and got another tune of 32 nozzles and start at 120 bypass. My question is how much leaner is going down 1 size nozzle jet. Is it like going up 8 sizes on the bypass jet or does it lean it more. I know smaller nozzle jets and bypass means more fuel psi. Pump is twin gear 0 1/2. James has me on the right track but wanting to learn what I’m dealing with.

Nozzle Bypass
33 125
32 117
31 109
30 101
Is this how it works or am I in left field on my thinking

MFI is just a big math problem. let me explain, you have 100% pump output and the pill and nozzles decide what % goes where. you do this by finding the total area of the nozzles and pill combined, then dividing the nozzle total to come up with the % of the pump.
so for your 33 125 combo, 35.80% of the pump goes to the engine. if you were to go down to a 32 125 combo you would have 34.40% of the pump going to the engine. a 32 120 combo would result in 36.26% of the pump going to the engine.

Joe

Thanks Joe. Wasn’t sure how the nozzle jets compared to changing the bypass. Makes since figuring it like that

Here’s something to consider trying to get you close to a tune up with mfi. Put an EGT sensor in one of the pipes and record what the max reading is at WOT during the run. Try and get in the 1100* range for 1/8 mile and then tune with the pill for the best mph.

I recently changed from Enderle to Rons nozzles and the suggested starting pill size for this conversion was over 10 sizes too large (lean). I knew this because I installed an egt and it read over 1300* max in the 1/8. Once I switched to a smaller pill and had 1100* in the 1/8 I removed the egt and now tune for the most consistent ET.

I believe the difference in how efi will best run in a sbc can be dramatic in pump / nozzle / pill combination. Even over or under driving a pump can alter / achieve the desired results.

I had several different EGT and on my car if you had 1100* temps at finish line then it was blubbery fat and .20 slow. Car ran best at 1350* in 1/8 mile and 1400* in 1/4 mile. I have zero faith in EGT temps. Totally useless in my opinion.

I have and EGT and for what ever reason with a carb or injection no matter if the car is lean or fat it reads the same. That was with a stand alone or the racepak. I know the car was way fat because it was missing and taking fuel away got rid of it. Started out with a 33/86 and ended up 115 to stop the miss and car picked up each time I leaned it. I’ve run injection years ago on a car I drove and it was deadly but was on the car when I started driving it. I’m learning and just trying to figure the math for what each pill or nozzle change does. I think a week or two I’ll have it close if not where I want it.

If its blubbering its fat, lean it either on the main pill or on the port nozzles. You can work the nozzle size down and main pill down to get to a desired system pressure but that's something you should talk over with James Monroe or someone at Ron's.

On the enderle side of things, NA with an 80A pump, if you get above 125ish main pills you should consider getting smaller nozzle jets, not mandatory but the tuning window on the enderle setups seems to be between 90 and 120 for the main pills. Some setups like high speed lean outs some dont. Gotta test and tune to see what works best for you, if you dont' have a HS lean out consider getting one as it may put you in the sweet spot, then again it's not necessary on the majority of MFI setups.

Reason for 90 to 125 on Enderle stuff is consistent amount of flow change in that area. If you look at gpm the change becomes more drastic out side of that range. Not a ton but not as consistent .

If you want to check as see pressure difference FIE site has a tune up calculator thats pretty good. BAsically all you need to know is pump flow at 4000(pump speed same as 8000 engine) and nozzles.

If you go down n nozzles you will need to do same with jet to get enough fuel.Smaller bucket more push same amount crap in kind of thing. This is after you have decent tune on it of coarse. Which in bracket car most wouldn't want to change if it was good.

As for EGT's. They are a tuning tool. If used wrong they will not work just like any tool. Easiest way to dial it in is O2 and EGTS. Get O2 in one cylinder and match other seven to egt using nozzles to fine tune it it. Remember when you lean one cylinder you richen the others by a very slight amount and if richen you lean others, Its not much when doing one but do 3 or 4 and it will have you swapping nozzles for weeks. All of which is probably more pain then needed in bracket only car,but a perfect tune should be more consistent.

If no egt or O2 then old school.Spark plugs and et slip tune it.Low tech but have been working for years. One change at a time is golden rule either tuning method.

quote:

Originally posted by C Hodge
Just bought and installed a Ron’s terminator setup on my 421 SBC. Trying to learn a little about the nozzle jets and bypass pills. First week out 33 nozzles 86 bypass car was way rich and started missing around 500’ out. 6.36 and ended up 6.27 so I’m getting there. I started leaning it out and the miss stopped at 115 bypass and ended up racing with a 125 and it was still rich. Called and got another tune of 32 nozzles and start at 120 bypass. My question is how much leaner is going down 1 size nozzle jet. Is it like going up 8 sizes on the bypass jet or does it lean it more. I know smaller nozzle jets and bypass means more fuel psi. Pump is twin gear 0 1/2. James has me on the right track but wanting to learn what I’m dealing with.

Nozzle Bypass
33 125
32 117
31 109
30 101
Is this how it works or am I in left field on my thinking

In my opinion the 0 1/2 gear pump is pretty big for a small block, unless you making a lot of power. I ran one on a 414 and it took me a while to get the tuneup right. It would go rich before the shift and before the stripe. I think i ended up with a 30 nozzle and around a 100 on the bypass.

^^^^^^^ I agree with this. I have a friend with a 417 and 0 pump. He overdrives it with a 20 T drive sprocket, 32 nozzels and I believe a 90 pill (may be incorrect on pill).

i would also agree on the pump sizing. james set me up with a 0 1/2 on my SBC, and it was difficult to tune. Swapped for a 0 and the tune became much easier to find

Hate to by a pump with this being brand new and 1 weekend on it but don’t mind putting a bypass on it. Ron’s has a bypass for when to big of a pump is used and also a dual for pump and hi speed bypass.

quote:

Originally posted by C Hodge:
Hate to by a pump with this being brand new and 1 weekend on it but don’t mind putting a bypass on it. Ron’s has a bypass for when to big of a pump is used and also a dual for pump and hi speed bypass.

Call and ask to send it back and exchange for 0 pump. Doesn’t cost anything to ask.

My pump is too big also and I have a high speed bypass to help. On mine I have a .050 pill and it comes in around 7000 RPM.
You need to know your pressure at RPM to set up a bypass but not a big deal.