2mm foam tuning advice

[medicevans]

This morning was 67-70* on the ride to work and had just rained so medium humidity. I'm working on getting the foam on the 2mm dialed in perfectly. It seems that this morning when I rode, the bike was running really well and had a lot more umph down low than it has lately. Does temperature make that big of a difference? If so, what should I do to the foam for hotter and colder?  Bigger when hotter and smaller when colder or vice-versa?  I have quick on and off side covers, so I don't have a problem carrying two or three pieces of foam around to get it dialed in appropriately for most conditions.

[Equito]

Steve will be along for the dial-in, but you're correct in suspecting that temperature can make a huge difference to the impact of a static fuel mix (power and mileage per gallon).  Cold air is denser, so there's more air to the same fuel, so cold temps lean out the fuel mix.  Warm temps do the opposite and richen the mixture.  Incidentally, the same is true for altitude - higher elevations = less air = rich mixture, so if you're jetted OK for sea level, you can have the bike barely run at high elevations and if it's hot in the mountains, you're going to start fouling plugs (if it's cold, then you're in better shape).

You'll never have "perfectly" dialed-in foam for every temperature and/or elevation and/or barometric pressure - only fuel injection can do that.  Hard to know what sizes of foam to carry for different temps (20 degree differential?  10?) without a dyno, or consistent recorded observations resulting from experimentation.  Certainly, you could pull the foam for mountain riding.

Ideally, you'd pick a single foam size that was perfect for the mid-range of your usual riding temps and elevation, and live with less than perfection otherwise.

[medicevans]

Thanks for that informative reply. I will continue to experiment. I like things to be as close to perfection as possible. Its really more for fun, but I wonder if I could make an adjustable flapper and use it to develop "presets" for different temps, kind of like the adjustment on the rear shock. I ride from 10* to 110*, so it might be kind of a pain to set it for 55* .  Have a chart in 20* intervals and dial in the airflow for the temp that day. Again, I'm probably not ever going to have the time or inclination, it's really just more for learning and introspection.  I have been chewing on using an oxygen sensor to provide voltage and then an onboard controller to monitor the voltage and restrict or open the airflow to maintain a stociometric mixture. I have no idea how to do it though.........

Sometimes you have a nail and have to find a hammer, sometimes you have a hammer and you are looking for a nail!

[Equito]

It's a pity politics got in the way of institutional memory, but the previous board contained a ton of useful info that appears to be lost - among the casualties were a couple of good threads by people actively working on adjustable flapper mods to the air inlet - haven't heard anything since the original board fell.

[medicevans]

If I remember correctly, Steve tends to frown on those, as he says kind of what you said in the beginning:  Just pick a spot in the middle.  Like I said, it's fun to kick around those kind of ideas, but sometimes a person just needs to know when to quit......

[jim snyder]

I am the one who made the adjustable airbox plate which would solve medicevans problem.

[Steve in Sunny Fla]

 I think Equito's answer was spot on.
   Jim Snyder has developed a sliding, easily adjustable airbox restictor that will work well. The reason I chose to do the foam rather than something more elaborate was because 1) price; and 2) I think most guys would mess with it until they totally screwed up and have no idea why. When it comes to carb jetting, a little information is almost a bad thing, because it only raises more questions; I think the simpler the restriction is for most guys, the better. There are those who may be more informed, and those guys should check with Jim and see if hes willing to follow up with the sliding restrictor plate - HTH, Steve

[medicevans]

Shucks, Steve. I usually start with a little information and go slow until I feel comfortable messing with something. Then I come running/calling when I need help. I have really really toyed with the idea of buying a cosmetically wrecked Conc and stripping it down into a bracket racer. I had even wondered what you, Steve, could do with gearing to make it a dedicated 1/8th mile bike.

Jim, pm inbound on the adjustable plate.

[Steve in Sunny Fla]

For a dedcated drag bike I'd start with putting a zl900 / 1000 bevel drive on. 8% lower than a connie. Yeah, i know some tricks! Steve

[medicevans]

Well, I need another project like I need another hole in my head.  But I will keep that particular piece of info in my head for the future.  The proper opportunity might present itself.  Actually, I should just make my current bike into a dedicated racer as the cosmetics are wonky anyway, but I would have a hard time justifying spending that much money on a most-likely-non-money-making-venture.  Drag racing is kind of like owning a boat. 

Oh, also, I bet putting velocity stacks on a Conc will make it produce more horsepower!!  That always works on other bikes! 

[medicevans]

Seriously though, for a dedicated bike, what would a person do for exhaust? Straight 4-into-4 weedburner/streetpounder style setup?

[jim snyder]

Seriously though, for a dedicated bike, what would a person do for exhaust? Straight 4-into-4 weedburner/streetpounder style setup?

For a dedicated drag bike I would remove the oil cooler and then you could find several 4 into 1 pipes that would fit.

[medicevans]

Why 4 into 1?  What does that accomplish?

[timmerz]

Scavenging, I bet...

[jim snyder]

Why 4 into 1?  What does that accomplish?

Because it works that why. There are hundreds of thousands of dragbikes out there with 4 into 1 exhausts, and its been that way for 30+ years. That should tell you it works. People ask me all the time why do I have a 4 into 1 on my
Connie, and I tell them because it works, but just as important is the fact that it SOUNDS AWESOME !!!
 

[Squishman]

Steve's instructions with the 2 Minute Mod says (under "tuning"): "In most cases, I find 1/2" removal to be just perfect from an economy and power standpoint".
When I read that, I was relieved that I probably could get away without doing any tuning. Because I was not confident in my ability to distinguish small changes. So I put it in like that, and I was happy from the get-go.

[medicevans]

Well, I like to tinker.  It gets me into trouble sometimes, but I take steps to minimize my risk from myself.  When/if I build the adjustable air plate, I will mark where I start comparable to my current foam, then fiddle from there. 

[jim snyder]

Well, I like to tinker.  It gets me into trouble sometimes, but I take steps to minimize my risk from myself.  When/if I build the adjustable air plate, I will mark where I start comparable to my current foam, then fiddle from there.

Ok here is the plate I told you about.