mgb-v8
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Re: Ignition and sparks

To: Theo Smit <theo.smit@dynastream.com>, "Daryl M. Naskale" <mgb@naskale.com>
Subject: Re: Ignition and sparks
From: Barrie Robinson <barrie@look.ca>
Date: Mon, 30 Jan 2006 10:18:01 -0800
Cc: mgb-v8@autox.team.net, mgs@autox.team.net
In-reply-to: <43DD1201.2040103@dynastream.com>
References: <019e01c6243d$7de28500$650fa8c0@daryl> <43DD1201.2040103@dynastream.com>
Reply-to: Barrie Robinson <barrie@look.ca>
Sender: owner-mgb-v8@autox.team.net
Theo,

Thanks for your input - Very interesting !!!


At 11:05 AM 1/29/06, Theo Smit wrote:
MSD does two things. First, below 3000 RPM you get multiple spark events, which is helpful in preventing misfires and the resulting plug fouling. At high RPM, the high coil primary voltage (up to 300 or 400 volts) saturates the coil even though the time between ignition events is drastically reduced. Conventional coil drive systems lose most of their fizzle at higher RPM, and this can lead to high speed misfires. I'm not saying that they are a cure-all, and you are correct that without a good timing reference the battle is lost from the outset, but the MSD systems and their ilk do provide useful benefits besides the big decal. A system like the MSD6AL also includes a rev limiter, and if you're at all interested in running your car in track or autocross events, then a rev limiter is an absolute must.
You can use the optical sensor from the Allison system to trigger the MSD input as well, and get the benefit of more reliable ignition triggering plus the improved coil firing that the MSD offers. No sense in going halfway...

To answer Barrie's comment - the problem with ignition is that the typical engine cylinder is not a big room filled with an explosive mixture - it has rich spots and lean spots all swirling around. If the coil fires when there's a big glob of fuel hanging on the electrodes, it won't fire the plug... and it also won't fire if the mixture at the plug, at the firing instant, is 25:1. The multiple spark business gives you better odds, and it does actually work. You just have to decide whether or not it's worth the $130 or more to get it, and I do agree that if you're on a budget, then fix your distributor first, and install an Allison, Pertronix, GM, or other points replacement trigger and amplifier.

Best regards,
Theo Smit

Regards

Barrie Robinson
barrie@look.ca
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