Hoenda

...yeah right! Like I understood 1/2 the things Jim was saying.
No, for real, Jim are you saying that the S2000 shouldn't run 'rich' at all and if your motor does then you need to have the fuel/air mixture adjusted?

BTW is that an S2000 engine doing 250+mph?

RACER

Dude whats up? There have been a lot of posts on this forum about black smoke coming out of the exhaust. Quite a few members (including myself) have reported black residue on their exhaust tips. When my car was brand new (less than 500 miles) I noticed a bunch of black shit on the bumper. Moderator, are we allowed to say shit? Anyway I washed it off and after another couple hundred miles, my bumper was covered with black specks, soot. I now have 3,000 miles on my car and the bumper for the most part, remains fairly clean (very few black specks) The tailpipes are always black. When ever I drive my car it is long and hard. I get the bloody thing hot. All the carbon should be burned away but the tailpipes are BLACK. This kinda contradicts what you stated above (no disrespect).

My car is bone stock, I have done 140 mph downhill with the wind blowing from behind me. This is far from 258.839 mph. When you say your S2K is bone stock, you mean the inside of the engine. You have mods that affect the way this engine performs, therefore, theoretically, it is not stock. You don't run the stock ECU and it has been professionally tuned.

Dude, can you reiterate about dynoing with the wide band O2 sensor, sounds interesting.

Thanks Jim

RACER

RACER

Yes it is a S2000 engine. Normally aspirated with stock insides. The diameter of the rear tires are rather large which affects the gearing, thus allowing it to go well over 200 mph.

xviper

I don't wish to get into any kind of "friction" with Jim as it appears he is a tuner extraordinaire but, these have been my observations:
All S2000's I have seen, have black, sooty tail pipes. All S2000's I have seen, have exhaust tips that get soot buildup very rapidly and are hard to keep clean. I don't have a wide band sensor, but the one I do have (autometer) shows that whenever the car is NOT in steady state driving and NOT being decelerated, the a/f is always slightly in the rich. In fact, even though the gauge lights are moving like a christmas tree, it is not difficult to see that during everyday driving, that the a/f tends to be more in the "rich" than it is in the "lean" or "stoich" areas of the dial and I have always thought that this is the way Honda meant it to be. So far, these observations go hand in hand.
As for the engine "sucking" fuel out of the fuel rail when the fuel pump is disabled, I'm not so sure about this one either. I have also observed that when I try to start the car with the fuel pump disabled, the engine will NOT start.
Granted, the S is classified as a LEV (low emissions vehicle) but this is not so much as it runs stoich most of the time as it is due to the extensive "emissions control" systems on the engine. If this car is driven with any kind of vigor, the fuel economy is not so good, whereas, if one were to put it on "cruise" all day, tremendous fuel economy can be realised. What does this mean? Maybe nothing, maybe something. These are simply "observations".
Many owners have posted here to indicate that when they "tune" their cars with a VAFC to "lean" out the fuel, more output can be achieved. So, if it were NOT rich to begin with, how can this be? Again, I'm not making any claims, only observations.

jimknapp

Hoenda and Racer,

Your questions one at a time, in a moment.

First let me say that I have raced on and off for a long time and continue to get smarter and smarter. Somehow, though, at the same time I continue to seem to know less and less. And please remember I do not drive an S2K in the real world (hmmm, maybe I should change that?).

First a little racing theory.

I bought a Honda motor out of my respect for the company and their attention to detail. I mean how else can you get 2 hp per cubic inch on 91 octane unless you are massively anal retentive? And I am always amazed at how much you can beat the crap out of modern factory iron and it still keeps coming back for more and more, while my expensive race motors can seem so fragile.

Now a basic, but often overlooked (because it's so basic, I believe) truth about racing is, you can't win if you don't make it to the finish line. That means all the little things, like if you get a flat on your trailer and don't have a spare, you don't win. Now I have seen an awful lot of folks (guys and gals) line up with these big stompin' "ego" motors and "lunch" them even before they get off the line, not to mention the "lunches" I've seen once they get underway.

So when I decided I wanted to own a world record (or two) I decided that, at least in the beginning, I would do it with a stock motor. And what better 2 liter motor than an S2K? There is enough to worry about as a rookie at 200+mph without worrying about hurting the motor, so I wanted to keep it stock. Now for the purists out there it is not 100% pure stock. Only about 98% I guess. I use a TEC III to run everything because I'm not smart enough to figure out the ECU, and a while back I fried the motor (that "smart" thing again, see thread at http://forums.s2ki.com/forums/showthread.p...threadid=162556 for more info), warped the head and had to take .008" off of it to get it smooth again. Also I had these grand plans about a snaky exhaust system until a couple of old hands said exhaust is the number one source of fires so just get it out of the car quick as you can. So I fabbed up my own exhaust but still use the four stock pipes out of the head and down to where they merge into two. And I made a little scoop out of 2 1/2 in exhaust pipe that hangs off the side of the car to help push the air into the intake.

And stock it is. I pull to line alongside these rumbling nitro snorting rides and watch while they go through their starting drills, and then have to get pushed off. I push the button, let it sit there idling quietly for 30 seconds or so, and then just motor off. In less than 2 miles I'm over 200 mph.

So let's get to your questions.

Hoenda, I say that a rich running motor indicates un-burnt fuel a big no no in the emissions world and not so good in the performance world. Again I don't drive in the real world but it seems that something is out of place. A modern tailpipe should be light charcoal gray inside. But again my first thought is maybe their engineering staff is smarter than me so I pay attention. Maybe they have to dump extra fuel into the tailpipe to keep that Cat lit. Who knows? Still it doesn't seem right.

Racer. I make my speed with the car, not the motor. The car is a streamliner and built to only do one thing. TOP SPEED. Period. It hardly even turns and is only 26 inches wide at its widest point. And it has been professionally tuned. We get 225 to 230 hp at the rear wheels which I think is pretty good, but still no barn burner in the S2K horsepower race. And to get to your second post, I do run bigger rear tires (24.5") but I also run a 2.56 rear end ratio in a narrowed 7.5" Chevy rear end.

Now O2 sensors. A stock 4 wire sensor is of value across a very narrow band of mixture, very close to stoichiometric only (about 14.7:1) And all it tells the ECU is plus or minus voltage. In other words it will not "tune" a poorly running motor. But it "only" costs $100 or so. A wide band sensor provides relevant amounts of voltage data to the ECU from about 8:1 to about 17:1 (I think) so it can go a long ways towards helping a poor setup. Also a stand alone unit costs about $1200. Most dyno shops use a wide band but they may have weld a bung into your exhaust to give you what you need.

Hope this helps a little.

Keep grinnin,

Jim