Take this with a grain of salt.

This is two back to back runs with a modified 3.4 DOHC engine I had. The only change was a different IAT sensor. Obviously it was very poorly tuned, but notice the power increase and spike advantages of the leaner curve. Also notice that the steeper acceleration rates go right inline with the lean spikes in the A:F ratio.

 

You don't need a dyno but you do need a repeatable,
quantitative measure of engine output across the RPM
band.

A flat stretch of road on a still day, and an accelerometer
would do as well; locked converter rolls from 40 to 80MPH,
or whatever you can do for maximum consistency / least
sources of variability.

If you can "shotgun" fuel and spark as independent axes
(safely) for a matrix of tunes, accumulate the acceleration
data and overlay the curves in an Excel plot you can pick
off the "top line" and its EQ, advance values are what's
right at that RPM. Which line wins at any point, may
change but you can follow it back to the fuel & spark
each point along the way.

It's work, but it should be relatively pleasant.

I have bought Analog Devices accelerometer eval
boards that provide 2-axis, voltage-mode accel
outputs for about $30 and with another $5 of
Radio Shack parts (or the European equivalent)
you can have an accelerometer box that plugs
straight in to your HPTuners Pro cable and log
acceleration to your heart's content.

I don't think you can get a clean answer, but you
could provide the first

 

Your calibration is too rich anyway, on the like 10% excessive in places, and rediculous near redline.

From what I've seen on engine dynos (I'm a calibration engineer), below 12.5 will reduce power a tad. Into the 11.8's, and you're down maybe 2 percent. 11.5's and you're down a few more percent. 12.6-13.1 won't change much. 13.8 will be down a few percent again.

EGT is a very important thing to consider as well. I usually see 12.5-12.8 without EGT problems, unless the timing is too retarded. 12.0 is cooler yet. 13's and up are pretty hot.

I agree with a previous poster's tuner's comment about set WOT A/F to safe (EGT, knock), and get power with spark without tickling the knock sensor too much. Don't go too low on spark either, as any wasted efficiency goes to EGT and the cooling system.

 

Where do you measure EGT?
How far from the heads?
Do you need to measure each bank separately?
Do you need to merge the gasses of the 4 cylinders of the same bank?
Or can I chack just one cylinder (for example using the AIR or EGR manifold flange)?

What are reasonable temperatures for NA / FI?
I know EGT is used for tuning, but I don't have a clue. I only go by wideband.

 

Yah, as I said, grain of salt. The tune was the stock tune, on a motor with a 13mm larger throttle body, equal length long tube headers, short runner intake, higher compression, CAI, full exhaust, UD pulley, and other things. So yah, bad tune...lol. We wanted to see how bad.

But it's interesting to see, the steepest acceleration slopes coincide with the 2 "lean" spikes, and the blue curve is higher beginning to end, and it is also the slightly leaner curve. So nothing we didn't already know, just thought I'd throw it out there. Plus, don't even try to tell me you don't like checking out dyno runs, imagining what driving that car might be like

 

ls1's that i have seen tend to not like it above 13 up high...but my buddy still made power he runs 12.5 or so down low and up to 13.4 up high made 47x and 44x

currently on my FI setup i'm running 12 almost across the board..more like 12.3 down low

 

The efficiency of port work really matters here as well. Weak ports make power richer. IE Stock heads untouched. A well set of ported DARTs will make better power leaner. Thats a fact!

 

How many PSI? How much power?
I tune it to have 12.5 with water alone, then add 5GPH of 50% ethanol what brings the AFT 0.5 points lower (12:1). This starting from 1 PSI.

 

Where do you measure EGT?
How far from the heads? As close as convenient, or about 3" if possible.
Do you need to measure each bank separately? Only if you care about it enough. You could also pick a "known" hot cylinder.
Do you need to merge the gasses of the 4 cylinders of the same bank? No need, unless you're measuring cats.
Or can I chack just one cylinder (for example using the AIR or EGR manifold flange)? Yes, but make sure the tip of the thermocouple is in the flow a ways (try for middle).

What are reasonable temperatures for NA / FI? NA 850°C is very dangerous, try to keep below 800°C (usually not very close to that on the stuff I work with in China). Depends on the valve and valve cooling, though. FI will be higher, regardless, just keep it rich enough to avoid detonation without extreme retard, and build it with good valves and extra attention to the exhaust cooling ability (seat width, cooling flow in that area, guide thickness).

I know EGT is used for tuning, but I don't have a clue. I only go by wideband. It's not terribly important for most people, until you start doing top speed long distance stuff (like we do with OEM calibrations), or are nitrous/forced induction (or both). Drag racers expect to go through engines before the valves go anyway , and as long as the tune isn't terrible, it won't be a serious problem. Towing guys should pay attention though.

 

First Off, Let Me Say, I Am In No Way An Expert. I Am However A Long Time Student.
There Are A Tremendous Number Of Variables That Come Into Play In This Type Of Question. When You Find The Perfect Air/fuel Ratio For Any Point In Your Power Curve, That Perfect Ratio Is Only Perfect At That Air Temperature, Cylinder Temperature, Plug Temperature, Mixture Velocity Through The Port, Mixture Velocity Through The Squish Area (piston And Chamber Design As Well As Proximty Of One To The Other), Fuel Atomization, Timing, Etc, Etc, Etc. I'm Sure There Are Many Others That I Can't Think Of At The Moment, And Many More That I Can't Even Imagine! (and I've Been Doing This For A Very Long Time) My Point Is That The Only Method To Find Optimum A/f Ratio And Timing For That Matter, Is The Scientific Method. I.e. Controlling And/or Recording As Many Of The Known Variables As Possble And Making Small Changes And Recording Those Results And Then Verifying Those Results. Thusly The Only Way To Accomplish This Is With Some Way To Quantify Both The Baseline And The Changes. A Dynomometer Is By Far The Best Way To Do This. There Are Of Course Other Ways, They Are However Less Scientific As You Have Less Control Over The Variables.
Now That I've Said This, I Need To Say That As Soon As You Change Any Of The Variables The Optimum A/f Ratio And Optimum Timing Change. Weather Changes, Mechanical Changes (even Of A Very Small Nature), Etc ,etc Have An Effect.
If One Is To Quote A/f Ratio's As A General Guideline, Then They Should Be Quoted On Generally Accepted Safe Parameters. 12-12.5 For Na Applications. This Is Not To Say There Wont Be A Better A/f Ratio For Your Particular Application, But Merely To Say That If You Wish To Maximize Your Tune You Need To Quantify The Optimum Results.(dyno, Track, Performance Meter And Consider The Enviroment). Dyno Tuning Is Best Because You Can Establish The Perfect A/f Ratio And Timing At Every Rpm Point In Your Power Curve (limited Only By Your Patience And $$). No Other Measure Of Performance Is As Valuable As The Other Methods Can Only Average The Total Performance Change.
Sorry About The Long Winded Opinion But It Is A Complex Question.
Jack.

 

I really wish people could just type, like normal, like everyone else. I didn't read past your first sentence because you can't even type. Why capitalize every word?

 

True power comes from spark and Timing. A/F is to keep it safe IMO. You can change the A/F and see changes but you are fooling yourself. Also be careful on what plug you use.

 

MS Word fixed it for him (well sort of):
Has anyone else noticed that the member from Switzerland has better control and mastery of the English language than many North Americans? Pathetic.

 

You don't know how long it takes me to post an answer
Anyway: thanks!

 

It's probably a damn good thing Tici doesn't post in French or German (native languages of Switzerland) as most Americans are much to lazy to learn another language.

 

...or Italian (my firs language)
Actually I know car stuff better in English than in other languages (all I know comes in fact from this plus a couple of other forums)

About the AF-ratio (actually the starting point of this thread): I understand that it's much more complicated than what it looks like.
I'll stick with a conservative tune (stock timing table) and 12.5 for NA.
When the blower is ON I go 12 AFR, spray some alcohol and go low in timing to 17*.

A G-meter could help to find out a better setting... actually I should check how flat my wife's ***** become during aceleration...
DD > D > C > B > A > FLAT! (it's clear she doesn't know I'm posting here).

 

Gasoline - Gasoline is what most of our cars came setup so it's usually what we stick with. Gasoline is a mixture of hydrocarbons. The petroleum distillate fraction termed "gasoline" contains mostly saturated hydrocarbons usually with a chemical formula of C8H18. The air fuel ratio, A/F Ratio, for complete combustion is 14.7:1, stoichiometric. The A/F ratio for maximum power is approximately 12.5:1 - 12.8:1. This means that our engine at max power, 12.8:1, consumes 12.8 pounds of air for 1 pound of fuel. Gasoline has approximately 18,400 BTU/lb . Using the air flow calculator with the default inputs we get our 355 SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and consumes 2.89 pounds of fuel. Therefore if we are using gasoline our engine is producing 53,176 BTU's of energy at 6500 rpm.

Alcohol (Methanol) - Alcohol is usually used in the form of Methyl alcohol or methanol. CH3OH is the chemical formula. Methanol burns at a much richer mixture than gasoline does, between 5.0:1 - 6.0:1. That's 5 lbs of air to one pound of fuel. Methanol has approximately 9,500 BTU/lb. Using our 355, example above, SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and now at 6.0:1 ratio for Methanol is 7.11 pounds of fuel. Therefore if we are using Methanol fuel our engine is producing 67,545 BTU's of energy at 6500 rpm.

Nitromethane - is a fuel that is used mostly in specialized drag racing classes, "nitro funny cars" and "top fuel". Nitromethane's chemical formula is CH3NO2. The oxygen in nitromethane's molecular structure means that nitromethane does not need as much atmospheric oxygen to burn, part of the oxygen needed to burn nitromethane is carried in the fuel itself. Typical A/F ratio for nitromethane is 1.7:1 and nitromethane has an energy content of 5,000 BTU/lb. Using our 355, example above, SBC consumes 567.53 cfm @ 6500rpm which is 42.64 pounds of air and now at 1.7:1 ratio for nitromethane is 25.08 pounds of fuel. Therefore if we are using Nitromethane fuel our engine is producing 125,412 BTU's of energy at 6500 rpm.

TABLE 1 Fuel Engine Air Flow (cfm) lbs of air (lbs) A/F Ratio Pounds of Fuel (lbs) Energy Content of Fuel (BTU/lb) Total Thermal Energy (BTU)
Gasoline 567.53 42.64 12.8:1 2.89 18,500 53,176
Methanol 567.53 42.64 6.0:1 7.11 9,500 67,545
Nitromethane 567.53 42.64 1.7:1 25.08 5,000 125,412

Summary - As you can see from table 1 above the clear winner is nitromethane. But that doesn't mean to go out and pour nitromethane in your car and see how it runs, if you do your engine will surely blow up. Nitromethane is very expensive and dangerous to handle. The interesting alternative to gasoline is Methanol. Methanol will make more power, typically around 20% more power than a similar engine running gasoline. Some things to consider in running methanol is your fuel system will have to be completely changed / upgraded. Based on the table above the fuel system will have to flow approximately 2.5 times as much as the gasoline engine.

I guess the old saying is true. "Gasoline is for washing parts, alcohol is for drinking and nitro is for racing."

 

A simple performance test, can be in-car acceleration in a fixed gear between say 4000-6000rpm for example.

Obviously on a flat road etc.

If you can log rpm vs time then its fairly easy to do back to back tests this way.

Im still not convinced pushing a boosted engine into the 12.x AFR range is safe enough to warrant the risk. Keep it in the 11's for all the power it will cost you. Engine longeivity is much more important IMO.

Aside from that...anyone know any way of hooking up an EGT prove that will output a 0-5v signal for logging ?
I do have a Greddy EGT guage, but its kinda hard to watch that, and the road at the same time.

 

Would you say the same holds true in the presence of a good spray of methanol? Richer is obviously safer as a general FI rule when we think of 11.5 vs. 12.5, but what if that 12.5 is in the presence of IAT's 30 F below ambient with the extra octane provided by the methanol? Just curious what people think about that. To keep it simple, let's assume the methanol delivery system is dependable.

 

Basically,the more air and fuel you can stuff into an engines cylinders,the more power you can make.You want to refrain from going to lean or too rich.Lean mixtures burn slower and result in more complete combustion,but lean mixtures also cause internal parts to run hotter and also has a bad rep of causing detonation.Too rich can cause increased emissions and results in a loss of power in most conditions.Rich mixtures can also foul spark plugs and cause flooding or hard starting.When adding a Supercharger,Turbo,or N20 that is why we often install bigger injectors,fuel pump,or an adjustable fuel pressure regulator.We want to prevent from going too lean and causing engine damage.11:1 to 12:1 is usually a pretty safe AFR on most AA LS1 engines.You are constantly fighting a battle with the ECM on modern OBD2 vehicles.That is why I usually leave computer tuning to the pros.