Guest bastaad525 Posted February 17, 2004 Share Posted February 17, 2004 Yo2001 - wasn't it you that was messing around with your spark plug gap while you were dyno testing? I remember an old post I think where you mentioned that... what did you find the best gap to be and how much of a difference did it make? I installed a new MSD ignition last week to replace the one I fried 4 mos ago, and for the first time read the manual... I guess it would be common sense but I never thought of this... with the MSD and stronger spark, they recommend that you can open up the gap on your plugs. I was running the stock gap of .045", and decided last night to only open them up a little to .050". The car now feels much smoooooooother to the butt dyno, and seems to pull a little harder. Dunno if it was because it was a cold, slightly humid morning or what (it wasn't an out-of-ordinarily cold or humid morning, anyways), but this morning on the way home from work with the bigger gap, getting the tires to spin from a 5mph rolling start became no problem, from EVERY light... usually not able to do this, at least not so predictably. Car definately feels happier. Tempted to try an even wider gap... would I see any benefit or problems from this? Does it make sense to get more power from widening the gap over stock? Quote Link to comment Share on other sites More sharing options...
johnc Posted February 17, 2004 Share Posted February 17, 2004 Increasing spark plug gap tends to help low rpm while hurting high rpm. That's a pretty broad generalization but it reflects the affects of cylinder pressures on spark. In your case, the difference between .045 and .050 is probably not measurable. I ran .050 when I had an MSD6AL on my BSP engine. MSD recommends a .060 gap but I found a little bit of misfire above 6K with that large a gap ona 9.5 to 1 compression NA engine. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 17, 2004 Share Posted February 17, 2004 high rpm performance would only be hurt if the pressure get's to a point where it's "blowing the spark out" though, right? I mean, lets say I open them up to .060", and get no problem with misfire (bear in mind I shift at 5500rpm as well so that will help) and get no problem with misfire at all, would my top end still suffer? Makes sense that it helped the low rpm though, I know you say it shouldn't be measurable but it really did feel happier on the street, more responsive. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 17, 2004 Share Posted February 17, 2004 and get no problem with misfire at all, would my top end still suffer? Probably not, but there's only one way to find out... Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 18, 2004 Share Posted February 18, 2004 LOL true true... Yo where are you??? I know you were doing this stuff on a dyno so you should really have a good idea of just how much effect it has.... Quote Link to comment Share on other sites More sharing options...
yo2001 Posted February 18, 2004 Share Posted February 18, 2004 patient, my brother I was actually doing some driving in my new car. 8) I did mess with the spark plug gap on dyno to get the jagged line on the graph. Well, it didn't. With MSD box, it ran fine with stock .044" I did regapped it to .033" and same power result, it turned out to be my total timing under boost was too low which was making the dyno graph jagged. But adding timing, I gain 15-20RWHP can't remember the exact number. I did run BPR7ES (I can't remember either) NGK. Anyway, with MSD, seens that gap can be pretty wide and still fire. But sometimes, you can get misfire and a fire ball out of tail pipe. Then better gap the plugs back some. And diffenally, get a projected tip plugs. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted February 18, 2004 Share Posted February 18, 2004 okay that's the info I needed. Okay well screw it i"ll leave them at .050", it's not much over the stock gap, and didn't notice any misfire up to 5500rpm... it's only .005" over stock so I dont think that big of a difference. I'm not gonna mess with timing at all, just leave it at stock. If anything I may retard it a little since I"m running lean on top and no I/C, would like the extra insurance, so may drop it down to 18* BTDC. THAT I can definately feel the difference driving on the street though... even 2* seems MUCH more sluggish off boost. Quote Link to comment Share on other sites More sharing options...
yo2001 Posted February 18, 2004 Share Posted February 18, 2004 just check th eplugs after awhile, like next week. with too much gap, the tip will turn whitish like it's running lean. And remember, less timing, higher EGT and lean, higher EGT, both mix is a deadly combo. keep your ears open. Quote Link to comment Share on other sites More sharing options...
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