Very upset...!

[MOD(S)QUAD]

For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich


Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.[/QUOTE]

Unless I am missing something here, 13.0:1 is still way lean from my understanding

 

[VPRPWRD]

The first number is parts air, the second number is parts fuel. Fewer air parts, 13, to the 1 means it is rich.

 

[ralphie]

I thought a good number to shoot for was around 12 under a load...! dang....just when I thought I had a handle on the a/f deal. lol

 

[505'sFastestViper.]

Justin will get you dialed in

 

[Psycho1122]

Those A/F numbers are rich not lean. Stoichiometric is 14.7:1 which means 14.7 parts air to 1 part fuel. A lower number means less air to fuel ratio - a.k.a. a fatter mixture. You get the best power being slightly rich although I think being a full point rich may be a little too much for a N/A vehicle. Also every dyno test that I have attended the tech either locks the vehicle in whatever gear gives them a 1:1 ratio (3rd gear in our trucks) and tries not to get it to kick down a gear. Not sure if that is for accurate readings or just to limit wear/damage on the dyno. On our trucks they can activate the tow/haul mode button to keep it in third gear.

This information is correct in a perfect world. A "hunting" 14:7-1 is great when highway cruising under steady throttle (No load). However, our engines do NOT have an efficient combustion chamber and need to be on the rich side to make smooth, strong torque and detonation free H.P. at high R.P.M.

this is mine...looks lean to me...

YES, too lean by about a full point. especially from 4500 rpm to 5500. It does however "nose over" nice at redline.

so...under a load, mine ended up at 13.6 too lean...right? and a good target is 12.5-13.0 ?

Yes. 12.7 / 12.8:1 would be ideal.

This is a good explanation:

When discussing engine tuning the 'Air/Fuel Ratio' (AFR) is one of the main topics. Proper AFR calibration is critical to performance and durability of the engine and it's components. The AFR defines the ratio of the amount of air consumed by the engine compared to the amount of fuel.

A 'Stoichiometric' AFR has the correct amount of air and fuel to produce a chemically complete combustion event. For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air to one part of fuel. The stoichiometric AFR depends on fuel type-- for alcohol it is 6.4:1 and 14.5:1 for diesel.

So what is meant by a rich or lean AFR? A lower AFR number contains less air than the 14.7:1 stoichiometric AFR, therefore it is a richer mixture. Conversely, a higher AFR number contains more air and therefore it is a leaner mixture.

For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich


Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.

12:8-1 and richer to keep combustion chamber temperatures cooler. Add up to what some say +23 to +25 total ignition advance and KEEP the ratio at 12:8 or just under and your engine will make great N/A power.

For Example:
15.0:1 = Lean
14.7:1 = Stoichiometric
13.0:1 = Rich


Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.

Unless I am missing something here, 13.0:1 is still way lean from my understanding[/QUOTE]

Yes. 13:0-1 is still too lean at WOT.

Cheers Guys!

 

[VENOMOUS1 RACING]

Again he dynoed on nitrous plugs and sounds like overdrive so it surely wasn't an optimal set of pulls. Still unsure why one sheet reads one way and the other opposite? Anyone else see that?

 

[ralphie]

Scott, the dyno sheets that were close-up, were Stealth78's...not mine. we were comparing. His looked good to me. Here is mine.

 

[VENOMOUS1 RACING]

Scott, the dyno sheets that were close-up, were Stealth78's...not mine. we were comparing. His looked good to me. Here is mine.

Duh, I don't know how I missed that.
I don't like either! His starts off lean and fattens up nicely. You're starts out nice and leans out too much. Both are scary situations but I'd expect your numbers to be close to Stealths on NA plugs and tune corrected.

 

[ralphie]

We'll

We'll get it. Between Justin, Torrie, Scott and everybody here, we'll, or I should say, they'll get it. To much knowledge not to. Can't wait to get it cammed and dyno-tuned Thnx everybody....!

 

[JMB Justin]

Got it fixed up, 488whp/486wtq with JMB/PBJ cam and minor tune changes. That's through unlocked 3000 stall converter, 93whp and 84wtq gain over what it made before. I'll post a new thread with dyno chart Monday.
Justin

 

[505 V10]

Got it fixed up, 488whp/486wtq with JMB/PBJ cam and minor tune changes. That's through unlocked 3000 stall converter, 93whp and 84wtq gain over what it made before. I'll post a new thread with dyno chart Monday.
Justin

Question? What does the stall of a converter have to do with max output on a dyno? I am under the impression that stall only affects launch from a standing start.

Just wondering. Personally, anything without a 3rd pedal is boring to me.

 

[ralphie]

I have no clue. Maybe somebody can elaborate. All I know is, my truck sure runs alot better after the new camshaft got installed.

 

[505'sFastestViper.]

if the stall isn't locked up you have slippage . slippage equals horsepower loss

 

[ralphie]

Justin will have to elaborate on the "unlocked" converter. I wasnt there when they dyno tuned it, so I have no clue what they(Justin, Torrie and Perf. by Joe) did. Hell....had I been there, I'd prob. still been lost..! lol