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View Full Version : Better Fuel Economy from Increased Spark Gap?


99HXCivic
02-18-2008, 05:41 PM
For my Honda, they sell an MSD Distributor Cap that uses an external higher capacity coil. I was wondering if I got this and increased my spark plug gap, would fuel economy increase?

Has anyone already tried this and how did it work out?

slow poke
02-19-2008, 11:29 AM
Almost exactly what you are talking about has been covered and does work for some, see link. I have an F150 so the info on FSB is still relavent to me. These trucks seem to have a weak ignition system and crappy wires which cause misses at idle in particular. If your distributor is adjustable you can bump your timing a smidge as well, the combination is very effective.

http://www.fullsizebronco.com/forum/showthread.php?t=63592

I'm also running a single vacuum dual advance distributor on my 67 bug vice the mechanical it had when I bought it. I get more total advance smoother idle better mileage and cooler running of an aircooled engine with similar all out performance and no flat spot while driving on the street. John at ACN reports 3-4 mpg improvements are typical. If you check aircooled VW sites he is highly repected.

http://www.aircooled.net/new-bin/viewproductdetail.php?keyword2=IGD0001&cartid=

If you have a car that you can still tweek the ignition its worth a try but read up on old school ignition tricks. If you are brave enough and have a steady hand you can also try side gapping and indexing your plugs. With side gapping you typically want to reduce your gap by .010 depending on what works for your car. All of this has typically been done for all out performance but does help economy as well. I'm running side gapped NGK's in my Rio now.

http://performanceunlimited.com/documents/plugsidegapping.html

Good luck.

Daox
02-19-2008, 11:37 AM
Any engine with lean burn capability has a pretty darn good ignition system because lean air/fuel ratios are harder to ignite. I wouldn't waste your money.

shifty35
02-19-2008, 01:14 PM
I'd agree, Hondas have very high quality ignition systems. MSD and such are popularly done one them still, but the effect is mostly insignificant. I'd think the only thing that would improve is your idle quality.

Bear in mind that increasing the gap on your plugs simply increases the voltage required to fire them at the expense of spark temperature (related to current!)

Hotter spark is better than longer spark.

slow poke
02-19-2008, 04:32 PM
I'm no honda expert but which ignition parts are upgraded over say an LX model to run lean burn? I did not find any differences in my quick search. The idea of using a wider gap is because you are running a higher voltage coil that will jump the wider gap.

The concept has been proven in various models for years. That does not mean it will or will not yield a noticeable difference in any honda unless you can find multiple owners that have done exactly this upgrade with results in 1 direction or the other. In bronco's and F-150's it is a well known and highly touted upgrade especially if you are using and abusing your vehicle.

99HXCivic
02-19-2008, 08:03 PM
I joined a Honda Forum and will ask this same question too. I'm holding off on buying unecessary stuff for my HX until the 2009 Prius and Fit come out. These cars will determine if I keep my HX forever! If I do keep it forever, I'll max it out! Gonna get a carbon fiber hood too!

worthywads
02-19-2008, 08:45 PM
I respect this guys opinion.


http://www.fuelsaving.info/ignition.htm

If we're talking 67 bugs, yeah there is room for some improvement.

Maxx
02-20-2008, 07:48 AM
That side gapping info was pretty interesting.

Another trick to try is keying the spark plugs. It involves setting the plug gap to point toward at the intake valve. It may invovle changing the thickness of the washer on the plug so that it can still be torqued. Just use a sharpee marker and mark the top of the plug show where the gap is, then torque it down so that the mark points to the intake runner. Supposedly increases combustion... guess it depends on the head/engine.

Oh yeah, and don't forget the dielectric grease! It ensures a good electrical connection.

slow poke
02-20-2008, 09:46 AM
That side gapping info was pretty interesting.

Another trick to try is keying the spark plugs. It involves setting the plug gap to point toward at the intake valve. It may invovle changing the thickness of the washer on the plug so that it can still be torqued. Just use a sharpee marker and mark the top of the plug show where the gap is, then torque it down so that the mark points to the intake runner. Supposedly increases combustion... guess it depends on the head/engine.

Oh yeah, and don't forget the dielectric grease! It ensures a good electrical connection.

You learn something new every day. I have never heard it called keying only indexing, could be a regional term.

Little more info on keying/indexing.
http://www.advanceautoparts.com/english/youcan/asp/pht/pht20001001sp.asp

jcp123
02-24-2008, 01:17 AM
I got a better coil and ditched points/condenser in my high school '68 Mustang to good effect while widening the plug gap from .035 to .045. Mind you, the stock coil was pathetic, struggling to even put out 3/4 of the factory 20k volt rating, and points just never worked that well. Still, it picked up a better idle, better fuel economy, and better midrange torque and throttle response. Your results will vary.

I'd also heard of the indexing (never heard it called keying either), though I'd always chalked it up more to myth than reality. Dielectric grease is always a good investment, both on the plug wire boots and the lube-type stuff on the threads of your spark plugs.



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