I'm running 150 shot with the 6 degree retard on 355 SBC and I've been seeing recommendations at of 11.5 air/fuel ratio. My question is that at wide open throttle(WOT)? My plugs seem a little on the rich side with those numbers., they are quite black.

 

anyone?

 

Yes thats at wot only and when you are spraying. Thats a rough guideline. It may want to be leaner. I really hope you arent running 11.5 all the time at idle and cruise?

6 deg is safe for now, it may only need 3-4 deg out tho. Have to sneak up on the tune

make sure you are getting complete ignition. Whats plug gap? Tighten up on spray. Also plugs should be roughly 1-2 steps colder than stock depending on the heads compression etc. so ngk 6 heat range is where id start

 

Running 12.8 + or- at cruise, and was running 11.5 at wot without nitrous . The gap is 35deg and I'm running 8 plugs

Autolite AR133

Thanks for the response, I'm decreasing jet size by 2 in my holly 4150 750 ,bringing it to 12.5 at wot without nitrous/

 

Yes, try get more like high 13’s low 14’s at cruise and idle, and mid high 12’s at wot without nitrous

then tune the nitrous plate (im assuming wet plate) for mid high 11’s afr on the spray.

 

I'm at 12.2 at wot without nitrous, I still have 3 sizes smaller jets, so I can improve on that. And again, thank you very much. Oh ya I'm at 13.2 at idle. I have carboned plugs, but haven't looked at that after the last jet change.

 

To keep plugs clean you must run 14.8 to 15.2:1 air fuel for idle and cruise. Up to 15.9 is fine also.

14.5 to 14.7 will Tan them up, I don't like it

14.2 to 14.5 will brown them
13's will gradually blacken or foul them and also deposit carbon around combustion chamber, rings, etc... not good.

 

I'm tuning for nitrous , I can't use those numbers. Unless I'm missing something.

 

You dont use nitrous at idle or cruise lol

 

Wait a second my friend, what ever you set air/fuel up for idle or cruise, sets it for Nitrous use also. Unless you have nitrous controller, which Me and most people don't have. And to my knowledge, they don't set the air/fuel mixture. They set the volume of nitrous or shut off.. (If I'm wrong, let me know)

 

lets hold up a second…

what is your engine type? Is it carb or efi? If carbed, idle and cruise circuits are different from wot. Im not a carb guy so seek others help with tuning in the other boards here. If efi, idle and cruise fueling and wot fueling are totally separate in a sense, depending on the system.

what nitrous setup are you using? Is it wet or dry? Plate or nozzle? These questions need answered to understand what you are doing. Wet kit has a separate fuel supply, so the carb or efi does not need to do anything here. The fuel jet size tunes the air fuel ratio, once carb or efi is tuned naturally aspirated for max power which again can be 12-13:1 afr

dry nitrous is nitrous only and if thats the case then wot tuning of the carb or efi needs to be in excess to account for the nitrous. So when running off nitrous, your wot tune will be very rich. Now some efi has dry nitrous tuning ability… but thats a different more detailed topic not needed yet until we know what system you are using

this really should be moved to the power adder board or tech/general engine

 

Every car and engine ever made uses different fueling for idle/cruise vs wide open throttle


otherwise the plugs would just foul and blacken and the combustion chamber would carbon up with black hard diamond-like coating within the first 500 miles and it would ruin the engine oil and make the car need 500 mile tune ups

 

ROUGH guidelines I use.......

Idle and cruise 14.7-15.2

WOT NA 12.5

WOT NITROUS TO 150 OR SO 11.7 -5* then how it runs best on motor.

Of course there are a lot of variables, but this gets you in the ballpark

 

I have now changed jets 3 sizes and with each jet size changed, it has changed my Idle air/fuel metric my cruise air/fuel mixture and my wot(no Nitrous) air/fuel mixture. Separate and with different air/fuel ratios, but with every jet change all three have changed. I'm at 13.3 at idle, a little more at cruise and 12.2 at wot. Without nitrous. I'm running Nitrous Express ML1000 Mainline Carbureted Nitrous System with a Holly 750 4150 Carb , I've been running at a 100 shot, and I'm changing to run a 150 shot. And I'm getting this down to as safe as possible. With the air/fuel mixture. I still have 2 more smaller jets sizes. Kingtalon I misread your comment about air/fuel numbers . Thanks everyone.

 

Sounds like you may need some carb tuning advice on the other boards.

 

I might recommend here for carbs
https://www.theturboforums.com/forum...carb-tech.284/