Air fuel mixture???

[MAX EVO]

For an "04" Fatboy FI what would be a good air/fuel ratio I have done numerous mods to her ?????I am asking just so I can have an idea for when I take it to get tuned.

[Jeff S.]

There is no 1, A/F good, you need to have multiple. As an example, @ wide open throttle, you dont want 14.7:1, depending on the bike, you would want it closer to 12.7 or so. But you would not want that @ idle. And you dont have to now with EFI. So find yourself a "good" dyno tuner, not just someone who has a dyno. And make sure it is a load control dyno with sniffer. Then if the dyno tuner is any good, he will tell you about where you should be from how the bike runs in those areas.

[HDMD88]

Originally Posted by MAX EVO

For an "04" Fatboy FI what would be a good air/fuel ratio I have done numerous mods to her ?????I am asking just so I can have an idea for when I take it to get tuned.

Although 14.7:1 air/fuel ratio is the ideal ratio chemically, not every oxygen molecule will link up with a fuel molecule with which to react or burn. As a result, we add more fuel to the air to achieve maximum horsepower. For a street bike, as a tuner, I look for 13.0:1 to 14.0:1....13.5:1 being my target.
For a race engine I look for 12.0:1 to 13.0:1......12.5:1 being my target.

Horse power falls off slower on the rich side of the maximum horsepower than the lean side. To protect race motors against potential damage from excessive heat, its better to jet slightly rich rather than lean.

As Jeff has stated above find your self a GOOD tuner....each engine is different and this requires different air/fuel ratios. For an example if you have more compression than stock you have a more efficent combustion chamber, being more efficent means I can burn more fuel, more fuel means more BMEP. (Thats only one example)

Jeff spoke the truth about people who run Dynos, some can tell you how much horsepower you have and others actully use the dyno as a diagnostic tool to find problems such as air/fuel, mechanical, and electrical. These are the guys that can tune a bike, they can squize ever bit of horsepower out of the package you selected. If you don't know of a place like that call Dynojet and they will tell you where the closest Tuning Center is to you.

Good luck

[csoday]

Mine runs fine, makes good numbers (112hp and 120tq) and stays pretty steady at 14:1

[HDMD88]

Originally Posted by csoday

Mine runs fine, makes good numbers (112hp and 120tq) and stays pretty steady at 14:1

Those are good numbers for a 103 but if your running 14:1 there are more ponys waiting for you at 13.5 to 13.2. Don't take my word for it, try it, the dyno won't lie.
Seems your running a little bit more compression than the standard S/E 103" motor....and if you are I would be real concerend that my fuel was at 14.1.
Again good job in getting those numbers from a 103". Where they taken on a Dynojet or a Super Flow Dyno? Quite impressive.

[GRock]

General rule we use here is idle at about 12.8 to 13. WOT around 12.6 - 12.8 (Some performance engines with higher CR as low as 11.5). And cruising AFR is usually good around 13.8 - 14.0. These values are after warm up. As Jeff says, there is not one good range for all throttle positions and RPM ranges. And on EFI, you don't even want to know all the tables for AFR at idle for different air temps, engine temps, time elapsed, hot soak, and everything else that EFI needs just to start and idle correctly.

hdmd88,

I'm a little surprised at your target of 13.2 - 13.5 for street bikes. We usually start to lose power below 13.6 with most efficient being 13.8 - 14.0. Now we all know it depends on the build, and I know you have been doing this for a while, but I was going to tell you that there are ponies waiting for you at a little higher AFR. And I'm pretty sure Chuck Soday maintains a well tuned machine. Accepted tuning and engineering is in the ranges that I stated. And we tune everything from harleys to marine engines to snowmobiles. Teach me something I don't know, buddy. Always looking for more and better.

[SILVER BULLET]

Originally Posted by GRock

General rule we use here is idle at about 12.8 to 13. WOT around 12.6 - 12.8 (Some performance engines with higher CR as low as 11.5). And cruising AFR is usually good around 13.8 - 14.0. These values are after warm up. As Jeff says, there is not one good range for all throttle positions and RPM ranges. And on EFI, you don't even want to know all the tables for AFR at idle for different air temps, engine temps, time elapsed, hot soak, and everything else that EFI needs just to start and idle correctly.

hdmd88,

I'm a little surprised at your target of 13.2 - 13.5 for street bikes. We usually start to lose power below 13.6 with most efficient being 13.8 - 14.0. Now we all know it depends on the build, and I know you have been doing this for a while, but I was going to tell you that there are ponies waiting for you at a little higher AFR. And I'm pretty sure Chuck Soday maintains a well tuned machine. Accepted tuning and engineering is in the ranges that I stated. And we tune everything from harleys to marine engines to snowmobiles. Teach me something I don't know, buddy. Always looking for more and better.

GRock I really think it depends on cam,comp,and head design. I start to lose tq. when I get higher than 13-1 13.3 -1 I might be able to gain 1-2 hp. but thats not what I'm after.

[csoday]

Originally Posted by hdmd88

Those are good numbers for a 103 but if your running 14:1 there are more ponys waiting for you at 13.5 to 13.2. Don't take my word for it, try it, the dyno won't lie.
Seems your running a little bit more compression than the standard S/E 103" motor....and if you are I would be real concerend that my fuel was at 14.1.
Again good job in getting those numbers from a 103". Where they taken on a Dynojet or a Super Flow Dyno? Quite impressive.

We started at a flat line of 13:1 and worked it up to 14:1. I'm running all SE with HTCC CNC heads and pistons and a 257 cam. Comp at 10.5:1.

[GRock]

Bullett,

I don't tune for HP either. (Unless we get some whippersnapper in here who wants to be a dyno king). I don't have to tell you that Torque is what gets to from point A to point B. But we are talking street bikes here. And I will agree that the more modified the bike the more power to be gained with a little richer AFR, but if you maintain very high velocity intake charge on mild to medium mod bike, and keep too much reversion from coming up the pipe, which, by the way, can cause you to tune for richer AFR in error as you know), that we have always found that much below 13.5 will cost us. A lot of times with open pipes and big exhaust valves, you have to get a little richer, but I consider that tuning to correct for problem caused by the those errors in the build. I am a great fan of no larger that 1.590 exhaust valve and like to use 1.90 on intake up to 107". Lots of guys like to go with the bigger valves for "more flow", but we are actually able to get a bigger charge into the chamber using higher velocity and higher cylinder pressure. Besides, I've also found that the range of the gas analyzers can vary a good amount, so maybe that is where the difference lies. I buy the good ones, as the cheapies just don't make it for us and don't last.

[SILVER BULLET]

Hello GRock I think its more sniffer than anything. My jetting for 95 inch 10.5 - 1 comp. 110 tq. is 170 main in mikuni 45. Thats NOT rich. I still like seat of pants tuning and reading plugs. Magnifying glass ! {EYES DON'T WORK ANYMORE} I agree with your valve selection. I use 1.900 intake and 1.570 ex. but I modify the valve {Ferrea} I also believe in velocity ! I stay around 1.660 on cross section {intake} and leave the floors alone. 87% on seat. I totally agree with you on bigger ex. valve needing richer as intake charge excapes on overlap. I modify ex.valve to control that. A modified 1.570 valve will flow as much as a 1.615 ! I also do some heads with 1.940 intake but do not see much gain over 1.900 maybe 3 hp. but no tq.

[HDMD88]

Originally Posted by GRock

General rule we use here is idle at about 12.8 to 13. WOT around 12.6 - 12.8 (Some performance engines with higher CR as low as 11.5). And cruising AFR is usually good around 13.8 - 14.0. These values are after warm up. As Jeff says, there is not one good range for all throttle positions and RPM ranges. And on EFI, you don't even want to know all the tables for AFR at idle for different air temps, engine temps, time elapsed, hot soak, and everything else that EFI needs just to start and idle correctly.

hdmd88,

I'm a little surprised at your target of 13.2 - 13.5 for street bikes. We usually start to lose power below 13.6 with most efficient being 13.8 - 14.0. Now we all know it depends on the build, and I know you have been doing this for a while, but I was going to tell you that there are ponies waiting for you at a little higher AFR. And I'm pretty sure Chuck Soday maintains a well tuned machine. Accepted tuning and engineering is in the ranges that I stated. And we tune everything from harleys to marine engines to snowmobiles. Teach me something I don't know, buddy. Always looking for more and better.

Hey there GRock
I respect your tuning ability, I even directed a person to ask you about his fuel injection problem. I also respect Chuck Soday for his ability to get that Torque out of a 103'' Screamin Eagle build....thats awesome. I'm not going to sit here picking at this key board saying who is right and who is wrong. Frankly, I think we all major in the minors on most issues on this Fourm. I look at your target numbers, my target numbers, Hdwrenches target numbers, on and on, and all I see is Air/Fuel ratios SO Close to each other who's to say which one is better. I believe altitude, humidity, temperature, cams, compression, head flow, valve size, leak down, piston configuration, etc. all come into play with A/F ratios. A target is nothing but a target, something we shoot for. We don't, as tuners, stop at those targets....we go for the max torque that we can get without detonation. Do you agree so far? I hope so...let me babble on. I believe builders build packages that work for them, what I mean buy that is I know what works for me and I tend to stay in that paramater. Now with my experance for building Pro-modified drag engines I found that a 12.5:1 gave me the max HP and TQ I could get out of that package. The street engines I do get the max HP and TQ around 13.7:1 to 13.2:1.....my engines detonate at 14.0:1 so I try to stay away from that area. This is where I (my mouth) made a mistake, I shouldn't be so opinionated on what others are doing with their engine packages just because that works for me doesn't mean I should tell you thats where you should be.....so I appolize to all concerened in this matter. Bottom line, would I let you tune my engine? ... Yes! Would I let HDwrench tune my motor?...Yes! Would I let Mr. Soday tune my build?....YES! (then I'd richin it up a bit) NO, JUST KIDDIN. How about Silver Bullet..... Sure! The thing is I know each and every one in this thread will tune to get the max of what that engine has to offer.....with out a doubt. Thats what we do as Tuners. Lets get the A/F ratio at our target, what ever that my be, and then optimize the tune-up. Thanks guys for showing me how to look at things in a different light.
Oh, buy the way the 116'' Pro-modified Sporster....182 HP....167 Torque, at 12.5:1........I had to through that one in ...lol lol lol

[SILVER BULLET]

HDMD88 WOW ,nice #s on that sportster ! You are dead on !GRock got me all pumped up,so I hit the dyno today. Tried every jet known to mankind ! {45 mikuni} got a little flatter tq. curve with really lean 14-1 but lost power {as always} ended up at 13 - 13.2 - 1 From my experience I know that different pipes really make a difference ! One thing I do know,is that #@^&$##@* dyno room was hot !!!!

[GRock]

hdmd88,

Well written post, as always. Well said about ability to get most out of what we're workin' with. I think the whole thing has to do with what a street bike is. Is it a 95 build with a 37B and pipes? Or a 113" with Woods TW9b, heads, high comp ratio, and the rest of it? Have to balance between a guy who wants a little more power to haul his other half around the country and is looking for good gas mileage, and the one that wants to tear up the pavement every time he hits the throttle. In any case, my brain hurts from all this, so I think I'll mosey on over to the Religion & Politics threads and get into a real battle.

Bullett,
Don't tell me that an ole' timer like you second guessed yourself because of a couple of tenths of AFR. Hope your didn't lose too much weight in the sauna. I owe you a couple of cold ones.


Anyway, as for MAX EVO, the guy that started the thread, sorry, but it looks like we haven't given you a hell of a lot of info as to your original question. Between the guys that have put in their 2 cents, we probably have, combined, well over a hundred years of experience, so what the hell do we know anyway.