Air:Fuel Ratio

[ZT-R]

Hey guys, what kind of air:fuel are you guys running at idle, cruise, and WOT?

Mine seems to like 14.7-15.0 idle, 13.7-14. cruise, and 12.3 WOT.

Just seeing if that it is inline with you guys. The 12.3 makes me a bit weary, but I do know some people run that. I am running a good amount of timing I think, but i dont know much about timing.

Stock cams.

[pat1]

At Idle in closed loop ~14.7 and cruise in closed loop should be around ~14.0-16.0 for the best fuel ecomony with stock cams.

wot air fuel ratio should be between 11.6 - 12.3:1 If it was my motor I would be running around 11.0-11.2 at the most to deal with any problems that might occur ie amb temp,intake temp,crappy fuel and so on.

 

12.3 at wot is asking for trouble with advanced timing. Your on the outer limits. One hicuup and your done.

 

With all the money you have in that swap get it tuned by a experienced tuner. In my area it only costs 400.00-600.00 Then run the @#$% out of it with no worries.

Edited November 28, 2011 by pat1

[ZT-R]

Yea I did have it tuned by aem guy, but I am disappointed that the knock control is off. I am tweaking this tune and am bumping the boost compensation some to richen it up some.

[pat1]

The knock control is off? That means that there is no other table/map for the ecu to use when knock is heard from the knock sensors, What's the point to have that built in safety. Man if it was me I would take it back and get it retuned. A nice hot day would make a bad day for you or some crappy fuel that we are getting.

[ZT-R]

IAT compensation table is tweaked, but i am planning on upgradeing the turbos here shortly so I will be retuning it at that point.

[240zdan]

i like to run 11.0-11.5 but occasionaly ill see 10.8 or even a 12.0

your timing map looks good but why are you using the "all in" approach? if you look at your timing map the values are the same across the entire rpm range. you can actually start advancing after you make maximum torque, cylinder pressure starts decreasing and its safe to advance the timing. your timing map looks very similar to mine, i made 430whp@19 psi using similar timing values with 94 octane with just slightly less timing but almost identical.

 

i wouldnt play with timing though until you have the afrs dialed to 11.0

like stated a hot or even cold day, inaccurate iat correction settings and itll ping (ive had this happen, now i shoot for 11.0)

Also you wont gain much power by leaning it out from 11.0 to 12.2, if your concernced about the power lost just turn up the boost, but maintain the 11.0 ratio. its much safer for tuning/street/everyday use.

 

so to answer your question yes 12.2 is lean! i would be comftorable with that type of afr only with race gas or running meth injection, bu tnot with pump gas.

(even on my methanol 23 psi dyno 485whp i still shot for a 11.0-11.5 ratio though)

Edited December 7, 2011 by 240zdan

[rayaapp2]

I found that 10.3 or so is the rich wall you dont want to hit and 12:1 is the pretty much the lean wall under heavy loads and WOT. Top of last 3 gears(5000+) is super critical AFR & timing. I found that 3rd with my setup will survive 12.2-11.9 AFR, but no such luck with 4th and 5th. I ended up bringing my AFR down to 10.9-11.2 on that whole part of the map. I also gained all around power in 3rd gear pulls doing this! 23 hp and 33 Torques. I ended up pulling back timing for the load cells that had to do with the 4 & 5th gear pulls. Its still not totally correct though. Sometimes I can get my knock warning to go off in 4th gear near 6000 rpms(you can image though how often I actually hit 6K in 4th though as there are not to many places safe and legal to do that).

[ZT-R]

I actually had this tuned by a tuner up in Charlotte. The dyno numbers looked alot better with the 12 afr and i dont know much about timing so i dunno there. Anyway I think I am going to take it to a different tuner. I hate to pay another 700 bux though..grrr

[rayaapp2]

I hate to pay another 700 bux though..grrr

 

 

Damn! that's expensive for tuning!

Within 120 miles of me there are a ton of these tuning places. Must keep the prices down. Ive seen tuning for $30 a run on your own, and I paid $295 for the last tuner to tune a car in San Jose(was for a Hondata'd Turbo Intergra that had to be programed from almost scratch if it makes a difference). Sacramento Ca has a lot of places too that are all under $400. Although Im sure thats not to helpful to you where you are at, but I would think that since your tune is already close that it would only take a few more runs to get it sorted out. Its not like starting from scratch again. A good tuner should be able to get you sorted out pretty quick and therefore it SHOULD not be another $700... Id expect $200-$300 max. More than likely less.

Not that tuners shouldnt get paid for their time. Dont take it that way. But for that Id expect a flawless tune that took at least 4 working hours on the dyno.

 

EDIT BELOW:

If you need clarification on what I am saying read bradyzq's response below regarding a retune cost. I would agree with his response. The only thing I would argue is the 10+% excessive fueling. For stock to mildly modded(<300hp)RB25, going into the low 11 AFR's @WOT is not to uncommon under heavy loading. I am not a tuner by trade, but I do tune and I have a small amount of experience in this area including the RB25's. So take my input with modesty.

Edited December 9, 2011 by rayaapp2

[bradyzq]

Hi All,

 

Disclaimer: I am a tuner!

 

$700 for a full tune is not expensive if it REALLY IS a full tune. 4 working hours on the dyno is a reasonable estimate assuming no issues are encountered.

 

Yes, of course we don't want our engines to blow up, but flooding it with 10+% excess fuel as a buffer instead of fixing the compensation tables makes NO sense to me.

 

Also, does your car run well? If so, what's the issue? 12.3:1 by itself means nothing, and, by itself, is nothing to worry about.

 

If I were you, I would call my existing tuner, ask him about the 12.3:1 AFR at WOT, the flat timing curve, and the knock control. When dyno tuning, you usually want it off. If he gives you good answers and the car is running well, you're golden and it won't cost you another cent!

[240zdan]

I wouldnt consider 11.0-11.5 "flooding the motor". 12.3 is borderline lean. There is no point running the motor that lean, it will just reduce the buffer zone of preventing detonation. If it were me id argue to the tuner the motor is running too lean for my liking and a AFR of 11.0-11.5 would be safer with pretty much the same power.

 

I am NOT a tuner but I have tuned my car and it runs fairly well.

 

I have yet to find a excellent "tuner" in my area. I want a guy who knows everything inside out, most tuners here are just guys who know how to operate their/someone elses dyno and know a bit about afrs and a bit about timing, as well as using a computer.

Another thing to consider: No dyno tuning can simulate real world conditions. My car showed no knock on the dyno, and proper afr. When I took it out on the street after tuning it knocked. I had to revise the tune. Temperature change also affected everything drastically. This is hard to simulate on the dyno,, temperature usually remains constant. IAT correction table must be well sorted.

Edited December 9, 2011 by 240zdan

[bradyzq]

Assuming the tuner in Charlotte knew what he was doing, at least in a general way, what is the point of paying him (and thinking of paying another tuner for more work) if you don't trust his tune when he's done?

 

Re: detonation avoidance techniques, I would suggest that getting the timing dialed in is how you want to go about it, rather than adding too much fuel to compensate for over-advanced timing.

 

From the OP's comments, it sounds like the tuner experimented with different AFRs, so he must have shown at least some interest in optimizing the tune.

 

I'm not saying that the tune in the car is the best ever. Rather, that richening up the high boost areas by 10% just "because" when there are no hints of a problem and with unknown ignition and fuel trim tables, is not good. The result will be a loss in power and an increase in fuel consumption.

[bradyzq]

More clarification:

 

Wideband readings vary, sometimes a lot. It also depends where they are mounted, and, if needed, how they are calibrated. Tailpipe probes may show leaner at low load, and if there is an exhaust leak.

 

So, taking that into account, I do what the dyno tells me to do. If it makes more power with no negatives (like knock) at a leaner AFR, then usually I'll leave it there.

 

Same thing with timing. Sometimes you can get scared of advancing the timing past a certain number. But if you do and find the best result is, for example, at 7 degrees past the previous "certain number," you are getting the most out of the engine, and would never have gotten there if you had followed the collective "wisdom."

[ZT-R]

What really started me guessing is i had to the the IAT comp table and no knock control. Mainly the knock control

[240zdan]

 

I'm not saying that the tune in the car is the best ever. Rather, that richening up the high boost areas by 10% just "because" when there are no hints of a problem and with unknown ignition and fuel trim tables, is not good. The result will be a loss in power and an increase in fuel consumption.

 

Im sure thats the last thing youre worried about in a car like this: fuel mileage under full boost. If a tuner told me he didnt think a bit of extra fuel was needed because fuel milage would suffer I'd tell him to get the car off the dyno ASAP and hand me the keys. I probably get 5mpg under boost, what do I care?

 

The reason I stated a slightly richer AFR would be beneficial is because I doubt the tuner tuned all the compensation tables to perfection. All it takes is that one condition to make the motor run slightly leaner and then detonation happens. I speak from experience. I would never trust a dyno tune fully. Take a motor that has been dyno tuned to a 12.3 afr onto a road course or highway rampage and you'll see what I'm talking about. Stuff changes. A dyno can never simulate "real world" conditions. This is why we back off timing a few degrees and add a bit of fuel. You are in control of the tune, not the car or dyno! The car responds to your changes and common sense. It doesnt "tell you what to do", and if it did it would probably tell you to turn up the boost!

 

As far as power loss, show me proof. I noticed no difference in power, a few hp a most. When youre running 500+ hp a few hp lost for reliability's sake is a good tradeoff.

Edited December 11, 2011 by 240zdan

[240zdan]

More clarification:

 

Wideband readings vary, sometimes a lot. It also depends where they are mounted, and, if needed, how they are calibrated. Tailpipe probes may show leaner at low load, and if there is an exhaust leak.

 

 

And another reason to tune on the richer side. Why risk it?

 

Quality of pump gas is another reason.

[pat1]

Are both you guys tuners?

[ZT-R]

Im sure we could go all day its just like rich or peak and lean of peak for airplanes. Pros and cons of both.

[bradyzq]

Hi again all,

 

I wrote this last night but hybridz went down for awhile and I couldn't post it:

 

Im sure thats the last thing youre worried about in a car like this: fuel mileage under full boost. If a tuner told me he didnt think a bit of extra fuel was needed because fuel milage would suffer I'd tell him to get the car off the dyno ASAP and hand me the keys. I probably get 5mpg under boost, what do I care?

 

You should care because it means the tuner has not optimized the tune.

 

The reason I stated a slightly richer AFR would be beneficial is because I doubt the tuner tuned all the compensation tables to perfection.

 

Right, and I suggested that that is the wrong approach. You can do the fuel IAT compensation mathematically then tweak it for extremes and engine protection. IAT timing trim can be done however conservatively you like. At least the ECU will begin its compensations from a well-tuned starting point.

 

All it takes is that one condition to make the motor run slightly leaner and then detonation happens. I speak from experience. I would never trust a dyno tune fully. Take a motor that has been dyno tuned to a 12.3 afr onto a road course or highway rampage and you'll see what I'm talking about. Stuff changes. A dyno can never simulate "real world" conditions. This is why we back off timing a few degrees and add a bit of fuel. You are in control of the tune, not the car or dyno! The car responds to your changes and common sense. It doesnt "tell you what to do", and if it did it would probably tell you to turn up the boost!

 

And what condition would that be? If it's not related to the tune (as in fuel pressure drop, dying injector, spark issues, etc) then a little extra fuel is not likely to save your engine. If the ECU doesn't know about a problem, it can't compensate for it. And, right, a good loading dyno (Dyno Dynamics in this case, I think) cannot simulate real world conditions. It can load the car even harder than it would ever be loaded on the street/track. So if you can't make it knock on the dyno, it shouldn't knock on the track/street. By doing "what the dyno tells me," I mean noting where gains do or don't occur and tweaking the tune accordingly. It's not always where we think, either. And, when tuning, I am in complete control of the dyno and tune, and, to a large extent the entire car. Don't know quite what you mean by this.

 

The dyno, nor my Rice Krispies, would never tell me just to turn up the boost on an overfueled, under-advanced tune! I will proudly make the same power as you while using less boost, but an optimized tune. I will create less heat, and stress the engine and turbo less too. These are good things when on track or on highway rampages, and, ironically, actually help prevent knock.

 

As far as power loss, show me proof. I noticed no difference in power, a few hp a most. When youre running 500+ hp a few hp lost for reliability's sake is a good tradeoff.

 

Regarding power, I simply believed what the OP said his tuner told him.

 

All I am trying to say is that 12.3:1 is just a couple of numbers. As we all agree, many things can affect what numbers pop out of the wideband other than actual changes in combustion. Who knows what the "real" ratio is? This is why I suggested that one should trust the dyno. If it's making more power with no knock, you're going in the right direction.

 

Please do not read into this that I am suggesting you run on the lean ragged edge "just because." That is as silly as running way too rich "just because."

 

OP, I am sticking to my position that if the car is running well, then the AFR numbers themselves are nothing to worry about. Get your tuner to dial in those fuel and spark trims, as well as the knock control and it should (hopefully) cost you nothing more, certainly less than if you took the car to a new tuner.

Edited December 11, 2011 by bradyzq

[240zdan]

You should care because it means the tuner has not optimized the tune.

 

Thats a load of crap. Optimizing the tune for fuel milage is important for part throttle cruising and idle, but under full boost I couldnt care what it is. We arent building direct injection turbocharged sedans here that claim 50mpg.

 

Right, and I suggested that that is the wrong approach. You can do the fuel IAT compensation mathematically then tweak it for extremes and engine protection. IAT timing trim can be done however conservatively you like. At least the ECU will begin its compensations from a well-tuned starting point.

 

Still guessing.

You really need to go out and drive the car year round to tune these as Ive discovered.

 

Please do not read into this that I am suggesting you run on the lean ragged edge "just because." That is as silly as running way too rich "just because."

 

11.0-11.5 is not running way too rich. Im sorry.

 

I will proudly make the same power as you while using less boost, but an optimized tune.

And I care why? 500+hp is already way too much power for a little datsun on the street. The only thing you will accomplish by making more power is

A. Greater chance of detonation. Leaner is faster, but more risky.

B. More internet brownie points since you posted a dyno graph that made a couple more horsepower.

 

Perhaps if you worked on the tune and went over everything with a fine tooth comb, it could be safe and reliable. I am sure you are a good tuner and know how to tune, but you have to understand alot of these guys are just treating this as a job and not a passion. The beauty of tuning a motor is you assume no responsibility, there is no guarantee.

 

 

The dyno, nor my Rice Krispies, would never tell me just to turn up the boost on an overfueled, under-advanced tune! I will proudly make the same power as you while using less boost, but an optimized tune. I will create less heat, and stress the engine and turbo less too. These are good things when on track or on highway rampages, and, ironically, actually help prevent knock.

 

It meant to be a joke. It wasnt supposed to be related to this topic in anyway.

 

And what condition would that be?

 

Doing a 5 second full throttle pull on the dyno is in no way the same as bagging on heatsoaked car on a hot summer day for 30 minutes, whether itd be on the street, or the track. I drive my car hard, and Im sure people who get their cars dynotuned are expecting to do so as well.

 

 

Hey everyone has their own beliefs and ways of doing things. To the OP, next time you get the car tuned, just tell the tuner to shoot for 11.5 and dont lead him into telling you that mid 12 afrs are fine because the engine made more power. Leaner is always going to make more power, but there are risks involved.

Edited December 11, 2011 by 240zdan