Multi Spark Digital CD ignition

[RAF7789]

Summit Brand MS digi CD ingnition:

http://store.summitracing.com/egnsea...115+4294908395

What do you guys think?
My car is a daily driver with minor bolt ons as seen in my sig.

My goals with getting this is to get better mileage and more throttle-responsiveness. But i would rather hear it from someone NOT trying to sell something

Thank you!

[Rob B (shoebox)]

There is a chance your mileage may improve. Though, I would buy something like an MSD or similar brand that has the correct adapter harness available for your car, so that you don't have to do any real wiring other than power and ground for the box.

[Joe 1320]

I've found that a multispark/CD unit will increase your mileage somewhere around 4-5%. While that's not alot, it's enough of a difference that you may go another 20 miles on a tankful. Then there's the arguement that for what the ignition booster costs, you could buy alot of gas over the course of a year. So..........If you were to get another 20 miles per tankful at an average of 1 tank per week, it will take you roughly a year to recover the cost of a $135 ignition booster. After that point, you would be saving money.

The throttle response would be a little more crisp too. HP increase is marginal, torque increase in the low end is increased but hardly a seat of the pants noticed modification. If you want to increase fuel mileage, go with underdrive pulleys, ignition booster and a good catback exhaust. Then 2.73 rear gears, narrow tires inflated to a high pressure, and stay below 60 mph.

That last one is the tough one.

[RAF7789]

i would be pleased to see a change in the mileage/responsiveness et c. i have been driving extremely conservative the past couple months. In fact, i have driven 60 miles since my latest fill-up and the gas gage is still directly on the "Full" mark

as for the underdrive pulleys-- let me get it straight:
-they are larger than stock to make less resistance on the Crank--> thus spinning the accs. at a slower rate---> would this noticably affect the alternator?

also, do i have to worry about the opti wearing out faster because of the "multiple sparks at 3k or less rpm"?

[RAF7789]

PS: Thank you both for the help.

[Injuneer]

The under drive crank pulley will be a smaller diameter than stock. That slows down the belt, which in turn slows down all the pullies it is driving.

You can get either an under drive alternator pulley (larger than stock) that will slow down the alternator even more, but will increase the chances of the electrical system voltage dropping too low at idle, with the lights and A/C on, or other heavy electrical loads (e.g. aftermarket high power audio system). Or, you can get an over drive alternator pulley (smaller than stock) that speeds the alternator back up, to avoid any charging problems. Avoids charging problems, but also reduces what is already a very small HP savings for the under drive crank pulley.

To summarize, a smaller crank pulley slows down the loads. Larger pullies on the loads slows them down even more.

I had the MSD-6L and never noticed any power gains, or mileage increase or improved "throttle response".... although I don't know what throttle response can even be if it isn't accompanied by a HP gain.

The guys that designed the Delteq system claimed that multiple spark ignitions increased wear on the Opti by breaking down the dielectric strength of the cap, but I never experienced that either, in more than 50K miles. My Opti died from rust. But then, the Delteq guys have proven to be less than reliable in their design and in their claims.

[Joe 1320]

The only thing you have to worry about is to keep the rpm limit to stockish specifications. There have been some reports of the opti failure at very high rpms with the MSD, but I never experienced a failure from mine either.

[Rob B (shoebox)]

The only thing you have to worry about is to keep the rpm limit to stockish specifications. There have been some reports of the opti failure at very high rpms with the MSD, but I never experienced a failure from mine either.

Seems like high RPM failures would not be an issue, being that the multiple sparks are phased out in the higher RPMs.

I have had an MSD 6A on my car for about 10 years now. No problems associated with it.

[RAF7789]

The under drive crank pulley will be a smaller diameter than stock. That slows down the belt, which in turn slows down all the pullies it is driving.

i think i get it: the smaller the pulley, the more revolutions the pulley has to make to acheive the same circumference coverage. the larger the diameter, the faster the outside of the pulley (thus the belt too) rotates.

gotcha.

as for the alt pulley:

..an under drive alternator pulley (larger than stock) will slow down the alternator even more..or you can get an over drive alternator pulley (smaller than stock) that speeds the alternator back up..

Reducing the size of the alternator pulley will make the alternator spin faster but make the engine work "harder" to do so. so smaller pullies (as well as gears?) require more power to rotate than larger ones. gotcha

The only thing you have to worry about is to keep the rpm limit to stockish specifications. There have been some reports of the opti failure at very high rpms with the MSD, but I never experienced a failure from mine either.

my understanding was that there is no RPM limiter besides the mechanical limit of the valvetrain; springs, valve overlap etc. or did i misunderstand your above post?

[RAF7789]

Thanks to all for the profesional advice.

[Joe 1320]

my understanding was that there is no RPM limiter besides the mechanical limit of the valvetrain; springs, valve overlap etc. or did i misunderstand your above post?

There is an RPM limiter programmed into the PCM that cuts fuel I think at around 6300. If that is removed, there is no limit except for mechanical limits like valve float.

[Joe 1320]

I had the MSD-6L and never noticed any power gains, or mileage increase or improved "throttle response".... although I don't know what throttle response can even be if it isn't accompanied by a HP gain.

.

I hear that quite alot. The issue might need to be looked at just a little bit. If the boost in ignition energy creats an increase in road HP at cruise from 11HP to 12 HP..... thereby requiring just a little less throttle to maintain crusing speed yet at wide open throttle there is no increase in maximum horsepower, do we still say that there was no HP gain? That's what frequently happens. An ignition or some other part is added and immediatly a dyno pull is done. Of couse, they peg it at wide open throttle to test the HP and torque curves. Doesn't anyone ever test part throttle or cruise effeciency besides manufacturers? I've found that there are a few mods that do little if anything for maximum HP at wide open throttle, but sure seem to impact part throttle operation.