[AMC-list] spark lead question for tuning experts like Nick Alfano...

[Nick ALFANO <71amx@xxxxxxxxxxxxx>]

Tom,

I am blushing at the accolades but I don't claim to be an expert. 

On a stock engine, the returns are not going to be that noticeable when you are talking 34 degree Vs 36.  Someone said NASCAR guys say they run best just before the blow.  That is pretty much true (ever notice your grass trimmer or leaf blower seems to get a boost in power just before it runs out of gas).  The most power your engine is going to produce is going to be as lean as possible with the most timing it will take before it explodes.  Basically, the more heat you can produce in the combustion chamber, the more power you will be creating.  This also means the closer you are to a melt down.  The problem with detonation in a stock engine is most often it is going to happen when the engine is under load and doesn't have enough power to work through it quickly.  Every revolution under this condition until it moves into an RPM where it is making power more freely, especially with cast pistons, the closer you are to disaster.  Don't
 chance it with cast pistons.  The difference in 1 or 2 degrees is not going to be worth much.  If at 36 degrees of total timing you have detonation, back it off a degree at a time or throw more fuel at it until it goes away (slight detonation is hard to hear with headers and dual exhaust).  The balance between fuel and timing is key to hp and hard to achieve without some sort of monitor like a dyno with sensors looking at the fuel/air as well as power graph, blips in the chart that might indicate detonation, fuel consumption and or exhaust temps across the power band.  I have seen engines where all cylinders look great except one where the exhaust temps were 100 degree more than the others telling me that hole wasn't getting at much fuel as the others.  My suggestion to you for a some what stock engine on the street is, find your spot just before detonation while getting a nice read on the fuel mixture by your plugs a little towards the lean
 side.  Run that tune only when racing.  For the street, back it off a degree or two more and not as lean for normal street driving.  The difference is only going to be a few hp that you most likely wont even feel.  The flip side is running on the edge, it only takes one tank of bad gas or a hot day to push you towards a melt down that will be costly for what, maybe 5hp.  Not worth it. 
.

Good luck

Nick
 Alfano Performance
4849-76 st.
Kenosha, WI. 53142
262-308-1302
262-942-8271 after 6pm central and weekends 


Message: 6
Date: Mon, 19 Oct 2009 21:30:07 -0700
From: tom jennings <tomj@xxxxxxx>
To: "AMC, Rambler, Nash, Jeep and family" <amc-list@xxxxxxxxxxxx>
Subject: [AMC-list] spark lead question for tuning experts like Nick
    Alfano...
Message-ID:
    <c81e13650910192130x47686fbt606221cdfbb4b80b@xxxxxxxxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"

Someone with dyno experience ought to know this stuff by the seat of their
pants, me I'm stabbing in the dark...

When you have a motor dialed in, just how sensitive is it to ignition lead
timing when it's under heavy load? In other words, if you have the timing
dialed in reasonably close, how many degrees away is detonation? How much
power is lost is it's retarded another degree or two or three?

I know it will vary with combustion chamber and compression and a whole slew
of factors. But for "sort of stock" or stock motors, how touchy is maximum
ignition timing, power-wise?

Bottom line is, how close to detonation should one push timing before it's a
waste of time?

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