Superbikes Of Supercross - cycle world. More food for 2T thought

[VintageBlueSmoke]

Sorry to have to tell you, cars changed to FI for performance...not the evil EPA. Even my 1970 Porsche 914 is FI (and I was pissed when i got it because I wanted Webers! I soon learned better.)

What you are missing about the simplicity of carbs are that they are so 'simple', they are only perfect at one point in the atmosphere at one point of the throttle opening. Eveything else is a compromise. Sure your carb'd bike runs fine because a it is like a bell curve. However, with FI fuel/air metering becomes more linear.

Yes, you do add other parts that could fail but the technology has come along far enough where those failures are rare.

[TMKIWI]

People complained when CDI's replaced points ignition.
Bloody electronics.

[VintageBlueSmoke]

Wow, TMKIWI. You sure know how to start a flame war. Bloody CDI. Give me points anyday! At least when they go out, all I need is a file and a matchbook cover to clean and adjust them (several times a ride!) out in the back country. So much better than my Motoplat that I set and forget and when it goes bad (after 30 years), I just have to walk home and buy a new one!

[Micahdogg]

Exactly - VintageBlueSmoke.

Here is some food for thought:
-1970 Chevy Vega, carbed 2.3L making 90HP.
-1990 Chevy Corsica, injected 2.2L making 120HP
-2010 Chevy Cobalt, injected 2.2L making 155HP

That is progress.  Anyone care to take a stab at how much the two stroke has progressed in the past 20 years?  I'm not talking, chassis or ergo's - just straight up motor progress.  Cause from where I sit it appears very little has changed - rather it has just been refined. 

I love two strokes, but not because they are relics.  I know the design is superior - that is why I choose them.  But we don't have to become stagnant.

-2013 KTM 250sx, carbed, 49HP
-1993 Honda CR250, carbed 45HP.

Go back to 1984 and the CR250 was advertised has making 43HP.  So in 30 years, the motors are making 14% more power?  That's just not acceptible.  Would anyone have bought a 2000 Chevy Cavalier with a carbed 2.2L that made 100HP?

[factoryX]

2010 chevy cobalt DOHC vs 1970 Chevy Vega SOHC, lmfao Great comparison there buddy. Another thing you need to realize is that these motor's were designed during the worst time in automotive history, AKA the 70's. Almost every car sufffered performance wise. The porsche 928 is a great example. Fully adjustable double wishbone suspension all the way around, Adjustable shock tower height, 50/50 weight balance(Motor front, trans axle rear), a little heavy at 3600lbs(To many over engineered electronic parts) but with a little gutting 3000lbs easy,  passive rear steer, and is one of the first cars if not the first car to be crash tested. Its an awesome car. The problem? The motor! It had 4.5 liter DOHC motor that only made 210hp. EPA had got so nuts with environmental crap, that these motors were completely plugged off. Simply changing the headers out is apparently good for another 30-50hp haha. in 1986 the 928 had 4 catalytic converters...

[Suzuki TS250/185]

"Here is some food for thought:

-1970 Chevy Vega, carbed 2.3L making 90HP.
With a compression ratio of 8.0:1 and 2 valves per cylinder

-1990 Chevy Corsica, injected 2.2L making ***120HP???*** ***WRONG ANSWER*** It actually makes only 95 Horsepower - BECAUSE of a substantial compression ratio increase over the aforementioned engine, to 9.0:1 (That's an 11% increase in compression) also 2 valves per cylinder

So... the Vega had 1/22 more displacement and 11% less compression, and it produced 90 Horsepower..... And the Corsica with Fuel Injection, 1/22 lesser displacement, and 11.2% higher compression produced 95 horsepower???

That's really not impressive... After all, any of our bikes could surely produce 5% more horsepower if granted a 11.2% increase in compression.

[Micahdogg]

You don't have to make excuses for the Vega.  Single cams are just fine, my v6 tbird makes over 500HP with one cam. (> Porsche 928 )

[citabjockey]

At least he didn't use a Pinto as an example.

[Micahdogg]

Hey there you go, lets look at the 2.3L lineage.  Oh wait, next I'll hear about the compression ratio and 1/11th size bigger displacement - because lord knows the carb was king in fuel delivery. 

[Suzuki TS250/185]

Are you saying that you wouldn't expect a 5% gain in horsepower if you increased compression by 11.2%

All I'm saying is that the increase in compression accounts for the increase in horsepower. With that much difference in the compression ratios in favor of the fuel injected example of nearly equal displacement, it doesn't appear that there was much gain, if any, resulting from the fuel injection. It appears to have resulted, in fact, from other differences in design.

The other demonstrative precedent is the fact that 4 Foopties haven't gained any horsepower as a result of fuel pumps, fuel pressure, and the resultant, frequent failures associated therewith...

[Micahdogg]

There are really too many variables to even compare anything.  You can't even compare the fuel used in the 1970's with the detergent rich stuff we use today.

I still contend, despite the teething process that fuel injection will go through - it will lead to increased power and efficiency alone.  And I'm happy with a carb on my bike.     

[factoryX]

But modern carbs today are showing increased efficiency, so much that they are on par if not slightly less efficient  Your super coupe may kickass, but there is a lot of work done to that stock 300hp super charged set up haha. I also think of the 89-97 t-birds/cougar xr-7, mark 8's to be some of the best cars in creation despite fords short comings aka half assing everything. The double wishbone suspension is to die for.  Funny that you should mention the t-bird, my dad actually dumped his 92 5.0 sport/lx due to the lack of tunability of the stock EFI set up.

[SwapperMX]

Suzuki TS, you really should post more often. Great posts !!

4 Foopty, love it !!

[2T Institute]

The fuel injected engines will make more HP on less fuel, also throttle response is increased, which on a race engine is everything. Lets you get on the throttle much earlier.
A 5.0 litre V8 fitted to many cars here make way more HP than they ever did on carburetor. V8 Supercar race versions were about 120HP up on carbed versions with a 9.0:1 comp cap and 7500 rpm rev limit.
Fuel injected 4T MX bikes will be the same more predicable torque to the rear wheel at any throttle opening.
 

[citabjockey]

I would agree with the prior post regarding better throttle response and more predictable output and perhaps a tad more peak horsepower. BUT all of these grains are, as TS points out, at the expense of a very simple and reliable fuel delivery method. At the top levels of MX this may be the point where FI is required to podium. And this increases the budget requirement of the teams for now. As the systems mature the cost will drop and the reliability will go up. Engineers working on a system just have that effect over time. For the average rider? Probably not necessary. At this point. BUT -- keep in mind that in the not too distance future (maybe 5 years maybe 10) we will "jet" our bikes via bluetooth to your FI computer from your cell phone. That is if it needs any tweeking at all. And the system will be very reliable. This is all for four strokes.

For two strokes we have a different ballgame. Very few examples of FI two strokes exist as models for guys (like Uniflow) on which to base their experiments. yes, I know there are some outboards and some snow machines but compared to the ocean of automobiles that have had FI for a couple of decades now the amount to two stroke FI knowledge is quite small. So the "issues" seen currently with injection on the 4-stroke MX bikes are orders of magnitude more difficult for two strokes I would think -- just because this is a NEW art.

BUT -- a FI (or heaven forbid DI) two stroke may have much larger advantages over carbie bikes than the FE 4T had over the carb 4T. Features like 30% smaller gas tanks and ability to get green sticker registrations in CA. These are features that have far more impact for the average rider than the FI on 4 strokes have. I for one welcome the coming change -- if it comes to pass before two stroke bikes disappear completely.

Again, for myself, I fully embrace the functionality, reliability, simplicity and serviceability of existing carbs. I would be fine keeping them and think that having CARB and EPA worrying about emissions from such a tiny set of ICE's is ridiculous. BUT such wishful thinking is unrealistic. I really believe that for the long term continued production of two strokes we must have a technology jump. Eventually.