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Old 08-17-2007, 02:23 AM
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Need help on my engine.

I have a 350 chevy motor. Standard bottom end with Brodix raising heads standard cam and rolar rockers with aPredator carb and a Wiand blower(not the roots type).The engine starts to ping when I boost over 1bar.What can i do to over come this problem. Will a octane booster or raising fuel help for my problem.
Thanx....

Francois

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Old 08-17-2007, 11:05 AM
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Hi,
Keep the boost below one bar, just kidding.
I don't know the answer to your question
as I'm learning about forced induction now,
but by giving some kind of answer, it will put
your question out front where someone who
knows will be able to answer it.
Good luck,
rich
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Old 08-17-2007, 11:30 AM
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Need help on my engine.

I found this stuff on the "supercharger store website". From what i read it sounds like the solution to the ping or knock is either boost timing retard, inter cooler, or higher octane fuel. Hope it helps


" What type of fuel do I need with a supercharged automotive or truck engine? The primary issues that determine the type of fuel needed are whether the engine is fuel-injected or carbureted, the compression ratio of the engine, and whether or not the supercharger system is intercooled

For Intercooled ProCharger EFI/TPI applications with compression ratios less than 9.5:1, boost levels of 14-17 psi can be safely run with full timing on pump gas, and will produce horsepower gains of 75-100% (depending upon the boost level and the motor specifications). For 9.5:1 EFI/TPI applications running without an intercooler, boost levels above 5 psi will require the use of ignition/timing retard on pump gas, and will produce horsepower gains of 35-45%. Boost levels above 12 psi should generally be avoided even with racing fuel on a 9.5:1 motor. Of course, lower compression motors will be able to run more boost, and higher compression motors should run less boost, everything else being equal. All Intercooled ProCharger systems for street applications are designed to allow the use of pump gas with full timing and will not affect daily drivability.

For carbureted motors, the rules are slightly different. Carburetors deliver the vast majority of fuel in a liquid state, and as this raw fuel atomizes from liquid to gas, a chemical state change actually occurs. Due to this endothermic reaction, which draws heat and cools the incoming air, a carbureted motor can safely handle more boost than a comparable EFI/TPI motor. For carbureted engines with compression ratios of 9:1 or less and boost levels in the 8-14 psi range, pump gasoline works very well. Compression ratios of 10:1 and higher require lower boost levels, higher octane fuel, intercooling, or some combination of the above. Compression ratios in the 7or 8:1 range can usually handle 12-20 psi on pump gasoline.

What is detonation, and how can it be controlled? Detonation, or engine knock, occurs simply when fuel pre-ignites before the piston reaches scheduled spark ignition. This means that a powerful explosion is trying to expand a cylinder chamber that is shrinking in size, attempting to reverse the direction of the piston and the engine. When detonation occurs, the internal pneumatic forces can actually exceed 10x the normal forces acting upon a properly operating high performance engine. Detonation is generally caused by excessive heat, excessive cylinder pressure, improper ignition timing, inadequate fuel octane or a combination of these. Of the previous, excessive heat is usually the culprit. As an engine is modified to generate more power, additional heat is produced. Today's pump gas will only tolerate a finite amount of heat before it pre-ignites and causes detonation. Although forced induction engines usually produce far less heat than comparable naturally aspirated high compression engines, the cylinder temperatures in intercooled engines are radically cooler yet. It is rarely boost that causes detonation, just unnecessary heat. An intercooler is such a natural solution for forced induction, that in almost every sophisticated application, intercooling is part of the package.

For engines that are experiencing detonation problems, the primary options are the use of ignition/timing retard systems, higher octane fuel, or intercooling. While ignition retard systems can be helpful in certain situations, they can also greatly reduce the horsepower output of an engine, as any reduction in timing will reduce horsepower.

And while a reduction in timing can save a motor from detonation, the excessive heat which was causing the detonation is still present.

Intercooling, on the other hand, actually removes the heat which causes detonation, and allows higher boost levels to be safely run with full timing on pump gas. This produces the maximum benefit in terms of both horsepower gains and engine protection, without any additional maintenance or hassle."

forgot to add the link, so here it is: http://www.thesuperchargerstore.com/FAQs.html

Last edited by mettalone; 08-17-2007 at 11:36 AM.
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Old 08-17-2007, 11:46 AM
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I would recommend 110 fuel, a boost spark retard.

Out of curiosity, whats you base Compression ratio?
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Old 08-18-2007, 07:06 PM
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Vapor injection. All the P-51 racers run high boost and it is the only way they keep an engine from self destructing.
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