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Dakota Performance
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mills
GenIII
 
12/18/2002
21:33:10
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 Subject: 4.7 leach flash
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im doing this as a consolidation post....i cant figure out from all the others who is talking about which engine.
anyway, im considering the mike leach pcm flash. who has one? what do you think? what did it give you? will i have to upgrade to 93 octane?
sorry about adding another pcm post, but im just plum confused by all the others.
mills
I'd go crazy if I cared!
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.alex.
Dodge Dakota
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12/19/2002
08:48:15
| RE: 4.7 leach flash
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1. Leach can't flash any truck beyond a 2000. They don't have the codes ready yet.
2. I run 93 octane in summer. With colder air in the winter, you could probably get away with 89 octane. But I don't. When you advance the timing (like they do) it will be more susceptible to pinging (long slow engine death).
3. What it gets you is no more rev limiter, no more speed limiter, and lots more horsepower & torque. It's a blast to drive once you get this flash!
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Waltherone
Dodge Dakota
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12/19/2002
15:55:31
| RE: 4.7 leach flash
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What exactly IS pinging? What does it sound like??
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.alex.
Dodge Dakota
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12/19/2002
17:04:17
| RE: 4.7 leach flash
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1. When you are accelerating very hard or accelerating up a long hill and you can hear what sounds like a Coke can full of marbles from the engine compartment, that is pinging. The harder you mash the gas, the more qucikly the marbles shake around.
2. The cause of those marbles rattling around is the explosion in the cylinder happening prematurely. The spark plug is supposed to ignite the gas & air mix while the piston is at the very top of it's stroke in the cycle. What's happening with pinging (or detonation or pre-ignition) is that the cylinder walls or the cylinder head or just the air in the mix is too hot and the mixture is exploding before the spark plug actually lights off. It's also happening before the piston reaches the appropriate position.
3. The result of this early explosion is two things.... first, that power cycle is wasted. For every individual ping that you hear, that cylinder has had a premature explosion and the piston did not get pushed back down into the cylinder as hard as it should have. Less force on the crankshaft, less torque, and therefore, less performance.
Second, for every one of those individual pings that you hear, it is like taking a center punch and a hammer and striking a divot in the top of the piston. Every little ping is a little pock mark in the piston surface.
With a supercharger or turbocharger (if the motor runs lean), the pinging will happen too fast for you to let off the gas pedal, and usually blows the top out of the piston. That sends metal chunks flying and your motor blows. Without forced induction, you are still sending little metal pieces flying, but much more slowly and much smaller pieces (just little grains). But, you get the picture.
There are several ways to stop the pinging:
1. Retard the spark timing. This makes the spark plug ignite later in the piston cycle to make damn sure the piston is at the dead top of its cycle.
2. Run better gasoline. Octane is simply a rating of a gasoline's RESISTANCE to detonation. The higher the octane rating, the less gasoline wants to combust. 93 will stop pinging if it pings on 89 gas.
3. Cool the intake charge. Colder outside air going into the motor will keep the combustion process from happening on its own. It will be depending on the spark plug to ignite the process and not explode on its own. Ways to cool the intake charge include cool air tubes, aluminum heads, small shots of nitrous oxide (50 hp or less), run a cooler thermostat to cool the combustion chambers better, or richen up the gas portion of the mixture with things like the IAT adjustor.
So, you can see how some things go hand in hand. If you get a PCM flash, they are generally going to advance your timing and richen up the fuel mixture. Sometimes they advance your timing so far that you are then required to run 91 octane to prevent pinging. But if you can advance the timing a LOT and keep it from pinging, then you are able to make a lot more power. If you run cheap gas and have a flash, you are tearing up your motor. If you are too cheap to run good gas, then you are not a good candidate for a PCM flash. If you know that your timing curve is very aggressive, then you also need to not stomp the gas in very hot weather without keeping an eye on the temperature gauge. You just have to be more responsible about how you drive. When you go to the drag strip in hot weather, it's a good thing to get some octane booster. That way your PCM flash won't harm your motor, and yet you still get the benfit of full power.
I'm just rambling, but that's what pinging is....
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graphiteRT
R/T
12/19/2002
17:30:20
| RE: 4.7 leach flash
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Alex, pre-ignition and detonation are two different events, though one can lead to the other. In the simplest terms, think of detonation as explosive combustion creating abnormal and excessively high cylinder pressures. Pre-ignition, OTOH, is normally associated with an incorrect ignition event relative to the combustion cycle, doesn't necessarily produce the high cylinder pressures, but DOES produce excessive heat and is actually the more dangerous of the two phenoms. Detonation will usually take out head gaskets. Pre-ignition will melt pistons.
Here's a couple of good pieces to read that explain the differences:
http://www.streetrodstuff.com/Articles/September_2000/Engine_Basics_I.php
http://www.avweb.com/articles/pelperch/pelp0043.html
Bob
'01 Graphite CC R/T, MP headers, Magnaflow muffler into 'Cuda style exhaust, M1 2bbl, ported 2.02 R/T heads, custom grind cam, Crower SS rockers, Paxton Novi2000, Boyd's 20s w/Dunlop SP9000s
Soon: Viper 4 wheel discs
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graphiteRT
R/T
12/19/2002
17:33:05
| RE: 4.7 leach flash
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Meant to note that detonation is not always audible. That's a common mistake many make. Usually by the time you can hear it it's moderate to severe and damage is being done, particularly in forced induction apps.
Bob
'01 Graphite CC R/T, MP headers, Magnaflow muffler into 'Cuda style exhaust, M1 2bbl, ported 2.02 R/T heads, custom grind cam, Crower SS rockers, Paxton Novi2000, Boyd's 20s w/Dunlop SP9000s
Soon: Viper 4 wheel discs
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.alex.
Dodge Dakota
JOIN HERE
12/19/2002
17:59:49
| RE: 4.7 leach flash
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Right.... what he said.
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DakotaCC
Dodge Dakota
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12/19/2002
19:19:35
| RE: 4.7 leach flash
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Ok, so the leach flash will give more power and torque and will possibly require premium fuel, for sure in hot weather. My question is, what will it do to fuel mileage??
Thanks,
DCC
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.alex.
Dodge Dakota
JOIN HERE
12/19/2002
19:52:07
|  RE: 4.7 leach flash
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If you are even remotely able to keep your foot off the floor, and continue to drive like a normal sane human, you may actually see an INCREASE in mileage. But if you're like me and you can't keep your size 14 foot off the pedal, you may see a decrease......
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Curt
Dodge Dakota
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12/20/2002
17:47:04
| RE: 4.7 leach flash
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HiYa,
I have been reading and adding my 2 cents every so often but, I have read many times on the '00 4.7 a flash or module will not help nor remove the speed limiter. Tell me if I am wrong!
Curt
'00 4.7, auto CC, 3.55 LSD, Flowmaster(SUV Perf),
and my homemade air intake
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.alex.
Dodge Dakota
JOIN HERE
12/21/2002
13:39:46
| RE: 4.7 leach flash
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You are wrong.
We spun mine up to 142mph on the dyno.
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