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R/TBlues
Dodge Dakota
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1/24/2004
20:26:09
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 Subject: RE: leech flash 2000 4.7
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The more compression ratio have the faster the fuel ignites. NASCAR engines run over 14:1 where as the 4.7L is something like 9.5:1 give or take .3. That means the more compression ratio you run the less full throttle ignition timing you have to run. It wasn't but just a few years ago that Ford was running 42 degrees full advance on their 351. An engine that has a very good combustion chamber design can run higher compression ratios without detenation. The better the combustion chamber design also relates to how fast the flame travels across the piston. If you have excellent flame travel combined with high compression ratio then you run a lower full advance ignition timing. If you have slow flame travel (poor combustion chamber design) combined with a low compression ratio like 8:1 then you have to run a very high wide-open-throttle (WOT)
ignition advance like 42 degrees. If the 4.7L is actually set from the factory for 17 degrees full advance then they must have an extremely efficient combustion chamber design because they don't have enough compression to be running that little amount of timing. A good race engine with 13.5:1 compression ratio will typically run between 26 and 32 degrees timing at WOT. On the late 70's early 80's 351 and 400ci Ford small block the initial timing (timing at idle) was set at 14 degress and if you wanted them to run good you had to crank that up to 16 or 17 degrees. They ran better at 18 degrees (44 degrees WOT), but the starter would kick back sometimes. I doubt seriously if the WOT timing on the 4.7L is 17 degrees. If that is all it is then it would most definately see improvement in every aspect of performance including gas mileage if it were bumped up to at leat 27 degrees. I think it would be safe to run 34 degrees with 93 octane. Assuming what Alex said is true then there is no doubt in my mind that the 4.7L would get 20+ mpg and smoke any R/T by simply bumping the timing up using the Leech Flash. I will have to investigate this further. I may be kicking my ass for selling the 2002 4.7L SLT. It did have much better throttle response than the R/T's 360.
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kowalski
Dodge Dakota
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1/25/2004
09:47:41
| RE: leech flash 2000 4.7
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I wouldn't doubt that alex's timing was set to 17 degrees if thats what he claims; however that doesn't mean all 4.7s are set to that. I suspect the manuals may get more spark advance from the factory and there may be other variables too. When I called to get the flash I was told how much performance gain I saw would depend on how much spark advance I had to start with. So you can't make generalized guesses about combustion chamber design based on the timing of one truck.
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.alex.
Dodge Dakota
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1/25/2004
12:33:45
| RE: leech flash 2000 4.7
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The efficiency of the 4.7 is one of it's strongest selling points. It replaced the 318 motor and kicks the 318's ass in all arenas. Mileage, power, and I'd be willing to bet... longevity. The 17 degrees of advance is but one of the factory settings that I've heard. I know of one truck who recently received the B&G flash thru KRC Performance where the WOT timing was 14 degrees total. But that was because his PCM had been flashed with a factory autorized software update that basically retarded the timing even further. There are about 10 different PCM manufacturers that assemble and program the PCMs for Daimler Chrysler and they all set the timing up differently. There are boxes that are at 21 degrees from the factory, some are at 19, etc.
Leach advances all of them to 29 degrees total.
To relieve a LOT of your doubts and answer a lot of your questions, you really need to call Mike Leach's Postive Performance in California (at the number listed above) and ask for Tom Fox. He will explain all of this to you and then you can compare NASCAR theory with him.
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Dakdoc
Dodge Dakota
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1/25/2004
13:22:06
| RE: leech flash 2000 4.7
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All of the stock 4.7L in the shop here come out to 8.6 and 8.7 compression with no more than 23 total and average being 16-17, lowest being 14. The Ho head has a slightly better quench pad than the stocker, allowing for higher compression.
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Duner
Dodge Dakota
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1/25/2004
13:23:20
| Fuel
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The amount of timing an engine needs or can use is largly dependent upon the FUEL you get to burn. If all you get to burn is 87 octane you aren't going to be able to use more timing like you could with 100 octane fuel.
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.alex.
Dodge Dakota
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1/26/2004
09:29:11
| RE: leech flash 2000 4.7
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Marty? 8.6 to 8.7?? I thought these things were rated at 9.3:1 from the factory?
What's the deal there?
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R/TBlues
Dodge Dakota
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1/26/2004
13:43:37
| RE: leech flash 2000 4.7
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I wouldn't doubt it one bit that the compression ration isn't what they advertise. Dodge lies about everything else. They claimed the 94-99 5.2L had the same HP and torque ratings at the exact same RPM's as the 93, yet they had smaller camshafts and smaller exhaust manifolds than the 93. Either the 93's had more HP and torque than advertised or the 94's and up had less. Either way, the RPM's at which the peak HP and Torque occured should have changed and they used the same graph in their brochures for 7 years. You can't rely on any published data Dodge puts out.
Higher compression engines require less advance. If the 4.7L only has 8.7:1 it desperately needs at least 29 degrees full advance. If you run racing fuel (110oct) at the strip with 8.7:1 and only 17 degrees full advance a Yugo will out run you. Hell, for that matter, it may not even run.
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kowalski
Dodge Dakota
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1/26/2004
16:04:53
|  RE: leech flash 2000 4.7
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You're really over simplifying here about compression and advance; there are other factors involved too. For example, they found the 426 hemi would take a lot more advance than the earlier hemis; even though the 426 typically had higher compression. I'll take a 4.7 Dak with only 17 degrees advance against a Yugo any day, that is just so wrong ! Care to grab a wheelbarrow full of cash and put your money where your mouth is ?
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5.9R/T
Dodge Dakota
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2/07/2004
20:55:04
| RE: leech flash 2000 4.7
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Does Leech have a flash for the R/T. If so will it change the Top Speed Limit? Will it stop the code for taking too long to warm up with the 180stat?
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5.9R/T
Dodge Dakota
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2/10/2004
20:29:59
| RE: leech flash 2000 4.7
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Does Leech have a flash for the R/T. If so will it change the Top Speed Limit? Will it stop the code for taking too long to warm up with the 180stat? Does it change the air/fuel ratio?
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CThomp
*GenIII*
2/11/2004
07:16:43
| RE: leech flash 2000 4.7
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5.9RT: Look into the M1 Flash from B&G Chrysler. It costs more than the Leech flash but is supposed to be the best for the money. I think the Leach Flash was supposed to be specifically for the 4.7L. Kenne Bell's optimizer flash is also available for the 5.9L.
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5.9R/T
Dodge Dakota
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2/11/2004
08:23:08
| RE: leech flash 2000 4.7
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THANKS!
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