LOL I was just googling that :)

I haven't seen a magical coil make a measurable hp increase but I have seen a fancy coil KILL some hp for some reason. A few months ago I dynoed a 600 hp Pontiac 455 street engine that I built for myself thats running a mefi4 ecu and harness. We were chasing a problem on the dyno of the motor going on a rev limiter in the programming at 6375 rpms that we could NOT get to go away AND a random breakup that would occur between 5700-6200. Using taylor 10.5 mm wires, a DUI 8 pin ignition module, dui's fancy gm style 2 plug connector coil that would fit most of our gm marine ignition systems all fired by a Crane hi 6 box. The dyno operator suggested wiring in his house coil that they use on most the engines that go acrossed his dyno, a msd hi tower drag 3 racing coil. In back to back pulls motor promptly LOST 25 hp/ft lbs of tq acrossed the peaks. I also substituted a stock mercruiser 2 plug coil vs the dui and saw no measurable difference. I also ran motor on just the mefi with Crane hi 6 box bypassed, no difference in hp except before installing the dui ignition module motor would break up randomly between 5700-6200 when the dwell load would over heat the stock ignition module, it would literally be so hot your fingers would blister if you touched it. With the Crane hi 6 box we were able to turn the dwell in the mefi software down close to 1.2 ms vs the 3.0 ms that is pretty much standard in most programs at 6k/14 volts because the ignition box was giving the ignition all the dwell it needed and the module would then only be warm. It still did this with the fancy dui module BUT it shifted up about 500 rpms and again went away when dwell table was reduced while running Crane box so from my personal exerience there is some reasons to run some of these boxes when you start turing stuff near or past 6k, Smitty
On a side note, we also lost a SOLID 40 hp on the top when trying to run a K/N 3x9 air cleaner like I see on MANY bbc boats that are carbureted !!

Lots of good debate and facts on this issue. In my case I have a 12.5-1 432" Hemi, with ported and raised intake runners, rat roaster intake, single dominator no choke,big roller cam, running Sunoco 110, not so happy idling when cold (or hot),changing to the MSD helped cold idle and low speed (less than 2500 rpm) performance. Was it the coil or the multi spark at low speed? Dont know but the product worked for me. Allows engine to idle cold and pulls hard right to 7k rpm limiter.

Great minds think alike!:drink::drink:

As always, good info Smitty!

How are you liking the Crane Hi-6M's so far??? And did you use the Crane PS-92 coil in any of your tests?

What did you use in it's place if anything?

it was an easy fix. he finally remembered to take it out of the plastic wrap before he installed it.

seriously tho, smitty, why do you think that was ? that implies the thing acted more like a restrictor plate than a filter ... was it just sized way way too small for the demand ?

I have a pair of K&N's----can't remember the exact measurements, but they're about the same diameter as Smitty's and probably about 10" tall or so. I tested them on Tom Earhart's dyno with one of my 540cid N/A engines way back around 2002.

We started out with a BARE/OPEN carb---no filter or spark arrestor of any sort, then I wanted Tom to do some pulls with the tall K&N air filter on and I distinctly remember getting a 3-5hp gain---I was kind of surprised so, I had Tom do another pull just for accuracy and then took it off---still 3-5hp difference between bare/open carb and the K&N air filter!

that sort of thing is not uncommon for a lot of reasons. the whole inlet tract from carb inlet to the lip of the intake valve is all one system and changing anything always changes everything. sometimes in a big way, sometimes almost not at all. i have seen 500 different instances of exactly the phenomena that you describe for 500 different reasons. i have seen an air filter make 5 less hp and then you space it away from the carb inlet by a couple inches and it makes 10 more hp ... why ? same filter... so that tells you that it isn't the filter at all but some how some way it is changing the velocity or pressure gradations as the air get down past the throttle plate...

its a weird and complex deal that i don't claim to have any mystical insight into. all i have are the learned lesson from screwing with a million combinations in a million different ways and trying to make solid engineering and scientific sense out of the results so that the knowledge is transferable to another application.

it isn't an easy thing to get perfect and it isn't something that normal intuition generally supports...

remember the frog joke ? scientists want to see how far a frog can jump... so they put him on the ground and yell... " JUMP FROG! " and the frog jumps 4 feet. They write that down... " frog w/ 4 legs jumps 4 feet...

so they cut off one of his legs and yell JUMP FROG ! and the frog sort of scrabbles a bit and jumps 3 feet. so they write that down... " frog w/ 3 legs jumps 3 feet ...

and so on 2 feet for 2 legs, 1 foot for 1 leg and finally they cut off his last leg and they yell JUMP FROG... nothing... and they yell JUMP FROG ! still nothing...

so they write down " Frog with no legs goes deaf..."

thats what working with inlet tracts and cylinder heads and intake manifolds is like... just when you think you understand what's really happening, you draw entirely the wrong conclusion based on what you think is true...

Hey Steve, Love that story of scientific analysis of measuring frog jumping performance! LMFHO!

As with engine performance, there always is an actual reason, no matter how small or big that always answers the question of why did the outputs change. The reality is though sometimes its just not worth the trouble to find it depending on the net benefit.

An interesting fact here about the K&N filters for the Merc 496 which we have tested and saw some reduced power versus the good old stock Merc flame arrestor. The Mercury flame arrestor has a nice internal bell mouth opening into the throat versus the K&N filter that has a sharp edge opening into the throat. Air as most know likes to flow over and into bell mouth openings and at higher air flows this can make a measurable difference. Does the K&N filter filter air better than the wire mesh openings of the stock flame arrestor, YOU BET! Is its extra filtering needed in a boat, I guess that depends on the cleanliness of the boating enviroment you are in. If the extra filtering is not needed then the expense of the aftermarket filter and its resulting power loss make it not such a great buy.

It always kind of amazes me how much money, time and effort performance seeking users will spend trying to practice "Engine Alchemy" with some of the so called "magical" products that are supposed to make serious power and performance increases. If sometimes they would just spend their time and money looking at a lot of things on their boats especially hull straightness and condition, drive efficiencies in X-diemnsions, setbacks and prop setup and selections they would see and benefit from some much nicer performance increases.
I am an engine builder by profession and as such I can really appreciate products and knowledge that can and do create good added power and performance from marine engines.
I have to say though that there are small items like, which good oil I run, which good oil filter is better than another, which ignition coil I am using, what spark plug size wires I am using, and such really won't make enough improvement to be even measureable let alone translate into increases in boat performance on the water!
When a performance boater "GETS THE NEED FOR MORE SPEED!" they should try to spend their time and hard earned money on upgrades and improvements that will really translate into good measurable performance "IN THE BOAT - IN THE WATER!" , everything and everywhere else "DOES NOT MATTER!"

Best Regards,
Ray @ Raylar