Pulsator

[earlbrown]

In that case Steve means the lean side of right. Not to be confused with not enough fuel

[Steve Wood]

LOL

Typically, the most hp is made at wot at the leanest possible A/F mixture that is not susceptible to detonation.  On the street, it is safer to be slightly richer than the leanest possible because ambient conditions may change a little and you need some margin of error for safety.

To illustrate, go find an old car with a manual choke on it, put the pedal to the metal, then pull the choke on....it will slow down and start to blubber...an extreme case, but too rich slows the car down, drops the hp, and makes the turbo spool slowly...

Why?  the richer the mixture, the cooler the burn.  Heat drives the piston up and down....leaner burns hotter....but detonation which is the combustion of the gases in the cylinder by something other than the sparkplug (after the plug has fired) spark tends to drive the piston down in the opposite direction of the normal engine rotation.  In other words, detonation is the auto combustion of the a/f mix from a source of heat other than the spark plug once it fired.  The plug fires and sets flame to the a/f near the plug electrode.  This flame spreads smoothly across the top of the piston until the entire mixture is burning about 15 degs or so after top dead center.  Detonation explodes the mixture around the edges of the chamber before the fire from the spark plug gets there.  This results in the big bang that happens before the piston has got to the top....stuff breaks and the engine tries to turn backwards right before you drive over the crankshaft....


Somewhere in there is an answer, I think

Not to be confused with preignition which is the combustion of the a/f mix in the cylinder before the plug fires.

[phil_long]

Ah.  Makes sense. My FP was really high after replacing the FP, and i drove the car to put gas in it.  On the way to the gas station I hit it to see if the FP was rising as it should, and it did. Those O2's that was shared earlier in this post are extremely rich;  BUT, it WASN'T at the top of 3rd gear.  Those numbers posted where a 1st gear pull only.  Are those O2's relevant?  I know it was said that there aren't any magical numbers, but on the vortex-buicks site, that 780mv was at the top of 3rd gear.  Sorry if i sound dumb, but I'm just trying to make sure i understand.  Thanks a bunch for the response

[Steve Wood]

Ideally, one would like it to be as lean as possible at any given point in any given gear when at wide open throttle.

The simpler chips may allow you to program for wide open throttle only and this is a one time correction for all gears, all rpms, etc.  Therefore, I picked top of third gear as this is typically where the load is the greatest, the combustion chamber the hottest, and the fuel pump the most tiredest so it is the point where we are most likely to suffer detonation all things being equal....meani ng we don't have too much timing programmed in, a kink in the fuel line, a pump that dies when hot, a black cat that ran across the track just as we launched, a big jump in air temperature or such.

If wot throttle is one of the main things we can change, then if it is safe at the top end of third, then it should be safe in all other conditions when the pedal is on the metal.  This does not mean it is absolutely optimum in other cases, but it is close enuf not to matter.

If you have one of the more sophisticated chips that offer all kinds of changes, you may be able to change things in first and second as well as third and fourth or even finer changes.  I think there are about 21 things I can change in my TT SD chips.  Bob's high end chips may offer even more things.  Aftermarket fuel management systems are almost infinite in the control they offer.

In the real world, if you take your car to the strip, once you shift out of first gear after launch, the car is probably operating in a rpm band that is 800-1500 wide and it is pretty easy to get the fueling close enuf over such a narrow range that all the bells and whistles in the world will not make any difference when it comes to a car that can be driven on the street no matter how much you pay an expert to tune your car on the dyno.

In theory, we know that a factory O2 number like 780 is meaningless because the sensor is a narrow band unit that only means something at 441 which is equivalent to about 14.7-1 a/f (stochiometric).  In reality, a wide open throttle number like 780 is quite repeatable if you have a wideband O2 sensor to check it by.   But we will also note that a 780 at wot is not the same a/f as a 780 at idle...or at cruise.

I can tell you that an 015 is consistently about 16.5-1 at cruise for whatever that is worth but it is where I get the best gas mileage!

usually, if you are seeing 780 at wot, you are getting close to the limit on pump gas altho the amount of timing, air temp, octane rating, etc. all come into to play.  That number is based on experience.

Spraying alky, I often see a number of more like 740 with no detonation with boost in the the 25-27 range.  I have seen lower.  I could add a couple of degrees of timing and be in big trouble.

The trick is to not look for a given magic number.  The trick is to look for No Timing Retard.  NO TIMING RETARD!  Don't run against the ragged edge.  The closer you get, the less pick up in performance you get, so back off and add a couple of percent of fuel to protect against the unknown.

We have three basic variables.  Boost, Timing, and A/F.  On the street I have found boost to make more power than timing so I play with boost and fuel more than timing.  I may add a degree or two in low gear but typically, the two decent chip makers, Eric and Bob, have a good handle on timing and for the street, I trust in them.

[Steve Wood]

The change in performance is not linear so don't expect major changes every time you take fuel out.  I have found that anything over about 810 on my cars...will slow the turbo spool down and hurt mph on the top end...notice I said my cars!

Also remember that you cannot make up for lack of octane with more fuel and that too much fuel can trigger the timing retard as well...whether it is rich detonation or the onset of hydraulic lock, I cannot say, but it will damn sure do it.

[Steve Wood]

Earl does it like this!

http://www.wallaceracing.com/plug-reading-lm.html

[phil_long]

Wow, this stuff is extremely intriguing.  My car runs better with the stock chip right now.  The fuel pressure for the stock injectors should be around 38 lbs static right?  Asking becuase right now its at about 42 lbs static, and my O2's are extremely high under heavy acceleration.  I did see some retard of about 3.8 and with an O2 reading of about 890.  Would lowering the FP lean that out?  Or Should i mess with my translator settings?  AGAIN, im going with the TT chip and some new injectors in about a month or so. This is purely for knowledge and making sure I max out my current setup now.  Thanks for your patience man.  Reading about this stuff and then watching it in action is amazing to me.  Only issue Im really having is that the BLMS arent agreeing with my O2's, but I'll tackle that later.  My lazy behind need to clean my air filter cuz it's filthy. 

[Steve Wood]

assuming the translator is set to the base settings, lower the fuel pressure

[Steve Wood]

if that drops the idle numbers too much, reduce the wot fueling on the translator

[phil_long]

ok cool.  thanks steve. idle blms are at 138 right now.  translator is set at base settings

[Steve Wood]

if idle is that high on the blms, then I guess I would go down one notch on the translator's wot setting

[earlbrown]

Earl does it like this!

http://www.wallaceracing.com/plug-reading-lm.html

My first thought was "why the hell does wallace racing have some of my old porn scenes?" !!


I like their http://www.wallaceracing.com/dynamic-cr.php Dynamic compression calculator. Didn't know they had an actual article on plug reading. Not the "make the ceramic look like cardboard" method

[smokin-6]

"but detonation which is the combustion of the gases in the cylinder by something other than the sparkplug (after the plug has fired) spark tends to drive the piston down in the opposite direction of the normal engine rotation.  In other words, detonation is the auto combustion of the a/f mix from a source of heat other than the spark plug once it fired. The plug fires and sets flame to the a/f near the plug electrode.  This flame spreads smoothly across the top of the piston until the entire mixture is burning about 15 degs or so after top dead center.  Detonation explodes the mixture around the edges of the chamber before the fire from the spark plug gets there. "

Not to be confused with preignition which is the combustion of the a/f mix in the cylinder before the plug fires.

Steve, I think I understand this...So detonation occurs at the same time when the plug has fired the A/F mix..they just meet at some point and slam into each other. AND preignition is an explosion of the mix without spark?

I always was hazy on those two words.

[Steve Wood]

yes, detonation always occurs after the spark plug fires.

In a normal series of events, the spark plug fires as the piston is coming upward.  The gas/air mix in the cylinder is ignited by the plug and the flame front spreads consistently away from the plug until all has been burned about 15 degs after top dead center...a smooth progressive burn.

If the combustion chamber is too hot, there may be a spontaneous combustion of the gases around the outer edge of the chamber before the flame front from the plug gets there.  This causes an abrupt pressure spike which is the noise the knock sensor hears.  This pressure spike is what blows head gaskets, or worse.

High octane race fuel takes a lot more heat to fire of the mixture so we can get by with more boost and/or timing.  Alky injection cools down the temps in the mix and makes it less likely to auto-combust.


Preignition happens before the spark plug fires.  It is caused by something like a glowing bit of carbon in the combustion chamber or a too hot spark plug electrode.  Because it happens well before the piston gets to the top instead of a few degrees, it is far more damaging.

Here is a link to a much better explanation  http://www.contactmagazine.com/Issue54/EngineBasics.html

[Steve Wood]

That article states that most detonation occurs after TDC which makes sense if one considers that the end gases in the chamber are the ones that auto combust before the flame front has reached them.  Therefore, detonation usually pushes the piston down in the normal rotation direction instead of backwards....l earn something everyday!