A/F Ratio discussion

[Sixpipes]

We had an interesting discussion concerning the A/F ratios while at the dyno yesterday. I added some 104 octane to my 93 octane pump gas yesterday before going on the dyno. I decided to do this because I had not previously run the new Swanson race program and was concerned about detonation and a potentially high A/F ratio.

There was some feeling that the higher octane fuel would prevent detonation, but not help prevent problems caused by a lean A/F ratio. I don't understand everything there is to know about the subject, but this is what I assume.

A higher octane fuel allows me to run a leaner A/F by keeping the octane to air ratio the same as a lower octane to lower A/F ratio. My assumption is that:

An A/F ratio of 13 using 100 octane is the same as an A/F ratio of 12.09 using 93 octane. This is assuming:

A/F=13/x (where x=100/93 octane)
A/F=13/1.0752688
A/F=12.09

Anyway, there is no secret to horsepower. Something to think about; if you continually push the limit by leaning your truck out to gain horsepower, you are putting your truck at risk. The luxury that some of the TALON guys have is a safe distance from a lethally high A/F ratio. More mods allow them to duplicate similar horsepower numbers with a much richer (read safer) A/F ratio.

I originally started with a Super Chip back in the summer of 1999. Big difference in perfomance from stock, but still very conservative with the A/F ratio. Early on, tuners were very cautious with Lightnings because they didn't have a clue how tough the engines actually were. I went to Swanson because I felt he was more agressive with his chips than most of the early tuners. I had a level of confidence in his product because he had a 99 Lightning, owned a dyno, and did a bunch of research with the CUX-1 computer.

There are a number of good tuners out there and most have become more aggressive with their chips. In the recent past, there have been a number of engine failures attributed to one particular tuner who many feel went over the line with respect to the A/F ratio. I don't know if that can be factually supported, but I believe that is quite possible (One particular guy from Canada will back me on this).

There is some ego that comes with having the fastest Lightning on the block, but there also comes with the title, a danger. How far do you push to stay ahead of the crowd? Is the risk worth the reward? I've got to honestly say in my book, "no". I plan on sending my chip back to Danny for a little "detuning" and will be replacing my TR6s with Densos next weekend. I suspect the TR6s are mortally wounded after my dyno experience yesterday.

Note: This Sunday's sermonette is available on cassette or CD. Please send a check or money order for $4.95 to:
Save the Go_rila
BR594
TooLean, TX

And we thank you for your support.

:beer:

[andy_cain]

Dennis:
I could not agree more.
I first started with a genneric (no tuner touched) off the shelf, Diablo chip...keeping in mind that it was a "generic" and that it was going on a 100% stock lightning, i felt there was no need for a "Custom tune".
One I put the chip in, the truck came to life...only problems were my pipes were white inside, and it was detonating at WOT, that made me worry.
At the dyno the is proved my concerns valid 13.2:1
I sent the chip back within the 30 day window for a free refund.
I then hooked up with TALON and Terry and had him do a "Tune Up" on my L.
What I have found in my limited experience is that without fail, my PSP chips (single and 4 way) have very conservative tunes in reguards to afr#'s. My last reburn on the PSP showed 11:1 numbers and my numbers dropped slightly from the previous burn with AFR#'s being 11.7:1.
None the less, I myself would prefer to have a fatter (safer) AFR since the truck is more times that not used as a daily driver in regards to driving 80 miles to Ennis to run 4 passes it just doesn't make sence to run with what I would consider dangerous tunes.

In addition, I have opted to go with NX Wet and a 50 shot in combination with my mods for the simple reason that given the choice of adding a 6 #er and removing my 4 #er or a 50 shot...the 6#'er is on all the time, any time the foot is in boost, the 6#er is working...with the NXkit, "I" tell it when and where I need it. I can keep the drivability and bolt on instant power that is shall we say, "In the Bank".

I just picked mine up from Terry last night where he did a great job on installing and building my electric fan kit, changing the water pump and putting in the 170 thermostat and wiring the whole thing up...Can't wait to get to the dyno. I also found that My Single Blade TB that I bought on line and installed myself was not set correctly, to whick Terry readjusted it for me and is going to check the voltage on the TPS for me when I catch him with his NGS scan tool...Hell of a deal...and "OK" I am retarded...didn't even know about the voltage issue...duhhhhhhhh

In spite of the long list of countless dollars I have added to my list of mods, I still am running a VERY safe tune and believe that it will pay off in the long run to add more bolt on's and have a fatter chip tune. I have seen people who have posted lately asking about why when the weather gets cold they get detonation...Might want to look at the AFR#'s

As to the octane boost additive and it helping, NO CLUE, ask 6 people and probably get at least 3 answers.

Sorry to hear about Go_Rilla....he is my inspiration!!!

:banana: :banana:

[Silver_2000]

In at least one sense Higher Octane wont make up for A/F ....

More fuel cools the cylinder... Raising octane wont cool the cylinder.

As I understood it Octane was simply a reference number relating to detonation resistance... Slows the burn across the cylinder.

I am not sure enough of my info to offer it by mail order but but me a beer and Ill spout more of the same BS...

Doug

[1BADTK]

Six, clean out your PM's, forum says they are full and won't take anymore.

[Sixpipes]

Originally posted by 1BADTK
Six, clean out your PM's, forum says they are full and won't take anymore.
Check. :burnout:

[WA 2 FST]

Sixpipes,

I've never seen the formula you used in the first post, but I am not sure it is the most important element to your discussion.

As you increase cylinder pressure, you must raise the octane for a given ignition timing, lower ignition timing, or you do run the risk of too high of an A/F ratio.

As Doug correctly points out, higher octane only results in a slower burn rate (which DOES help stave off detonation). However, there is a limit. I've seen engines with too much dynamic compression and 11.0:1 A/F ratios still have detonation problems.

That being said, another thing you have to consider is that the BSFC (brake specific fuel consumption) of a forced induction motor is always higher than that of a N/A engine...no matter the base or dynamic CR. Part of this is again due to what Doug points out. You must, in essence, "waste" some fuel just to cool the cylinder. So you use more fuel per a given HP in a forced induction application.

I do know that from my experience, I try to keep the 93 octane A/F ratio a good 1 to 1.5 points lower than when running on race gas. This typically means less ignition timing under boost. On my 5.0 Mustang I was able to run 13.0:1 A/F ratio, if I wanted to, with 105 unleaded (B42...Phillips 66 race gas...honestly, this is the BEST race fuel you can buy. It is not a bunch of anti-knock additives which is popular in a lot of junk race fuels we can buy. Phillips also offers plenty of leaded race fuels as well). However on 93 octane, I'd get that A/F ratio in the 11.5:1 range. This was not accomplished through any extra fuel delivery, but rather a reduction in ignition timing. I would see ~35rwhp drop going from one gas to another (again, due more to a different state of tune than anything).

Also, I must emphasize that one L motor running 8psi can safely see a leaner A/F ratio than another one running 14psi...assuming the same quality of gas is used. The thing is, you can certainly run into diminishing returns as boost climbs b/c you must fatten the A/F ratio that much more to handle the increased cylinder pressures. At some point, its better to just go into the motor, drop CR more, in order to run gobs of boost AND timing.

The bottom line is "one A/F ratio does NOT fit all".

Not sure if this helps at all. I'm scattershooting here.

[Sixpipes]

Originally posted by WA 2 FST
Sixpipes,

I've never seen the formula you used in the first post, but ....
Wes

That's because I made it up. :tongue:

I decided to come up with a formula to explain the benefits of running higher octane fuel and that's the best I could do. The kid at Speedworks indicated that my A/F was dangerously high. He went on to say that if I ran a high octane fuel (such as Phillips 106 unleaded) that I should be OK. The guys at Speedworks have forgotten more than I'll ever know about these type of things. That's why I wanted to start a thread on A/F so that some of the folks that actually have factual information can post. Feedback like yours is exactly what I was hoping to get.

I don't understand all the implications of high octane fuel, but understand that higher octane somehow protects the motor as opposed to 93 pump gas. If this is entirely due to detonation protection, then my thinking is incorrect.

I know that there are a number of ways to roast a motor. Most Lightnings seem to be throwing rods. Is this due to the inability to handle excessive horsepower? I'm guessing, yes. It seems to be resulting from short bursts of WOT. I have not heard of anyone burning a piston which I would attribute to high A/F run over an extended time period (example would be a closed circuit track or open road event).

I am going to send my dyno graphs to Danny Swanson tomorrow and get his opinion on the whole situation. I'm just trying to pin down cause and effect. Doug and I talked about this very thing yesterday and the last thing I want to do is replace my motor because I was making some incorrect assumptions about A/F and high octane fuels. I also thought it would be helpful for other TALON guys to understand the risks before continuing to push the envelope on the horsepower thing. I know that must sound funny coming from me. http://www.fordvschevy.com/forum/images/smilies/shifty.gif

[L8 APEX]

It is agreed higher octane is mainly to support more timing and absorbs more heat due to the slower burn . Here are my random facts of the day.
1) Race fuels are hard on fuel pumps, filters, and rubber lines. I spilt race gas on the back window of our GT1 car and it ate holes in the lexan:eek2: Make sure to check or change your filters after running a batch of race fuel. Something in it swells or clogs fuel filter cores:confused:
2) You must take into account the specific gravity (big word:D) of the race fuel being used. Running a face fuel with a lower SG? will flow more fuel in a given time frame i.e. injector pulse width. This is important when dyno tuning a vehicle for use with a specific brand of race fuel. You damn sure can't jusdge them on octane alone like Wes said. Howell race fuel rocks:tu:
3) You only want as much octane as you need to supress detonation. Any more is a waste of money and horespower. It will go through the motor as unburned fuel.
4) Race gas has more engery per volume than pump gas, To take advantage of it you must have the appropriate compression and timing.
5) Rod failure is more often caused by detonation or just too much power:D Lean A/F on forged pistons usually eats electrodes off plugs before burning a piston. Unless you run indesrtuctible plugs.
6) It smells good, and I knew Dennis made up that formula:D

[Silver_2000]

To get away form the DEEP tech talk - I'll offer some SMACK

I hereby decree that I will have the Highest dyno HP with the Fattest A/F in all of TALON land....

If I fail at that Ill change the rules for the next round....

:D ;) :p :cool: :d :banana: :twitch: :beer:

[andy_cain]

Doug:
I want some of that action...except the rule changing part:beer:

[Sixpipes]

Doug

Any formula I make up would probably be won by a stock Lightning. Since most of them run an A/F of ~8, they only need to crank out 320 rwhp to beat my newest formula. That is:

Doug Rating = RWHP divided by the A/F ratio at peak horsepower.

Using your graph we have: 402.2rwhp at an A/F of 10.6

Doug Rating (D/R) = 402.2/10.6 = 37.92

Say we have a stock Lightning at 330rwhp (which is normative). We could find the winning margin of the stock Lightning by using:

330/37.92 or 8.70 (or less)

My D/Rs are 31.92 and 33.5 for the 415rwhp and 402rwhp dyno runs respectively. Based on what I have seen, I would be concerned if my D/R dropped below 30 so I would say I'm safe for now. :cool:

[wesman]

I'll give my opinions tomorrow after some of the beer has worn off...it's all making my head hurt right now :beer:

--wes

[Badcarma]

Let's see if I got this right in short form:

If the air/fuel is "lean" then excess oxygen will be present in the exhaust, which tends to work as a heat sink-lowering peak firing pressure in the engine-which it will begin to misfire and lose power.


If the air/fuel is "rich" then excess methane will be presentin the exhaust. The excess methane will ensure that complete combustion occurs with the oxygen-which generally result in increased peak firing temperatures, but if too "rich" than potential for detonation and pre-ignition occurs.


Summary:


Ideal combustion=if fuel and air consume each other completely " Stoichiometer combustion ":eek2:

[Mark #2]

Doug,
Smack back, already beat you on the street side. Pegged the A/F meter at 10 with 407 and 505.:)

[jmlay]

Here is a calibrator for the PRO M

http://www.nloc.net/forum/showthread.php?s=&threadid=30513

[Ivanhoe_Farms]

What I don't get is . . . . . . . since we are running in Top Truck for the most part and . . . . . . Top Truck is Bracket Racing, why tempt the fuel/air to the point to lose an engine when in bracket racing consistency is the goal. Secondly, if you are trying to go as fast as possible, why use a GEN II when a GEN I can blow the doors off of a Gen II for considerably less money and be much safer in terms of engine life????:confused:

[L8 APEX]

Ivanhoe I think most of us want a safe A/F. I race my truck instead of a gen1 because of financial reasons. I think ALL of us would love to have a gen1 to race instead of the expensive gen2's:tu:

[Ivanhoe_Farms]

Gen Is are more expensive than GenIIs to race .... now exactly how many times have you redone your tranny, and what is the cost of all of the speed parts --- Gen 1s are 6-10k and a 351/427 shortblock is 2500 and a good set of heads 1500 and nitrous 800!!!:tu:

[WA 2 FST]

He's saying he can't have BOTH. He would rather have a Gen 2 as a driver...and thus, races his driver. :)

Having owned both trucks (black '94 I bought new years ago and later sold when the '96 Cobras came out), I would say without a doubt that for a driver the Gen 2 truck is far better. Much more refined and you can still retain a warranty and run 12s. Can't do that with a Gen 1.

My '94 was a great truck, though. 15.2 @ 88mph stock at stock weight. Then I bolted on an 8psi Vortech A-trim, SVO shorty headers, roller rockers, shift kit and ran 13.4 @ 103mph on stock radials. Not shabby. Still, my '99 is faster and much more comfortable and fun to drive.

But, no one (I don't think) is arguing that for a RACE vehicle, the Gen 1 truck is tough to beat. Those things are easy, easy to work on and modify. :)

[L8 APEX]

Thanks for setting it straight Wes. I was meaning to say G1's are a blast I would love to road race one. The twin I beam rails turns. But the G2's are what we all have financed/warrantied/whatever so that is what we try to have fun with:tu: There are a lot of cheap ways to run a quick quarter. But they all require buying and building a seperate vehicle.

[Sixpipes]

Originally posted by Ivanhoe_Farms
. . . . . . Top Truck is Bracket Racing, why tempt the fuel/air to the point to lose an engine when in bracket racing consistency is the goal.
Top Truck champ this year was Kevin Todd who drove an older F-150 that ran consistant 17s. Probably one reason FFW decided to lower the Top Truck qualifying requirement to 14.99.