Proposal: EFI for 2 strokes

[jim murphy]

Now that a source for 2 stroke motors has been secured for the forseeable future, let's look at another issue facing the F500 class.
One of the major objections with 2 strokes from the outsiders' viewpoint is the touchiness of the carburated 2 stroke motors to changes in air density (which happens all the time during the course of a typical day or different locations). Now that the EPA is pushing harder to get 2 strokes to be more emissions clean I have seen more and more closed loop (O2 sensor) EFI's on 2 strokes in various other drivetrains (boat motors come to mind). This leads one to explore the possibility of doing the same for the 593/493/494 motor family with an OEM or aftermarket one - if there is such a device even in existence that will work on these motors. IF this can be cost effectively accomplished and added as an option in the class rules then yet another objection has been overcome that outsiders have been adverse to for many decades in joining our F500 community.
SO, let's hear it from our 2 stroke gurus, please research this and start the process toward helping grow our class entries. A good starting point might be to talk with all the snowmobile race shops that do motor work.

Jim

Addendum: This thread has changed to what it will take to grow the F500 class in general.

[jim murphy]

My information about the EPA was based on several PWC dealers down here in the south stating their opinions about the future of 2 strokes so cool your jets until you get both sides of the story. Now, given your valid points that EFI may NOT be needed and that the TM40 and an aftermarket compensator MAY (?) be able to alleviate the touchiness objection I am now asking the 2 stroke guys to conduct a due diligence research project with dyno or whatever data is needed to support a proposal for a rule change in F500 to help.
Let's focus on the goal of making F500 more attractive and not me.

Jim

[Marshall Mauney]

One of the major objections with 2 strokes from the outsiders' viewpoint is the touchiness of the carburated 2 stroke motors to changes in air density (which happens all the time during the course of a typical day or different locations).

Jim - I believe that there is more perception than reality in this view (though perception can certainly impact an individual's desire to enter a given class).

A few random thoughts:

1) Of all the things I found troublesome and a pain to deal with on my F500, jetting wasn't one of them. Once you buy a density gauge, log the EGT and build your chart, it's a setup step that's no more difficult than changing tires or putting gas and oil in the tanks.

2) Anyone coming from karting will already know how to jet an engine.

3) Many of the other formula classes still use carbs and require an understanding of jetting. They may not be quite as touchy as a 494, but I somehow doubt you'd be able to win a race using the same jets at Pike's Peak in mid-summer as you would at Portland in the spring.

4) Changing fuel types generally requires a re-jet or re-map for just about any class -including some of the "spec" classes that use closed-loop EFI. The fact that you cannot change the ECM programming does NOT mean that you can't tune the engine for air/fuel using other means. Ask a few of the front-running SM guys how many times they've been to the dyno......

5) Some classes which use EFI still require tuning for air density, since they run open-loop control (like my FE). As above, we can't touch the ECM, but you won't be fast without managing air/fuel.

6) Carbs and jets are cheap and easy to work with. ECMs and injectors are expensive and more difficult. I can rebuild my own carb, no problem; injectors have to be replaced or sent out for matching. Tuning a carb is 5 minutes with a couble of dedicated wrenches, a chart, and an air gauge; tuning an ECM is 30-45 minutes with a laptop, fiddling with fuel pressure, fiddling with a MAP sensor, fiddling with a TPS, checking to make sure that your wideband sensor is still working and calibrated properly, etc. If I lose an EGT at the track, I can still run based on air gauge readings and history; if I lose a MAP, TPS, lambda or wideband O2 sensor at the track, I'm parked unless I have a spare and a way to calibrate it.

My point is that you have to understand air-fuel mixture management in just about any racing situation. These aren't street cars, they're race cars - if you want to run up front, you can't afford to ignore the engine, no matter how much you may want to believe that the ECM does the work for you. You can set it on autopilot and run around at the back of the field if you like, but that's not what racing is all about, IMHO.

[jim murphy]

Marshall,
Good points. Then, what do you see as the number one objection that can be fixed?

Jim

[Marshall Mauney]

Marshall,
Good points. Then, what do you see as the number one objection that can be fixed?

I'm not sure that I'm the right person to answer that question, because I've actually owned and driven F500. Thus, I understand what really IS an issue vs. what ISN'T an issue.

For example: I've heard guys talk about "wanting to shift gears". Being someone who has actually driven a number of race cars with various types of transmissions, I find this to be a ridiculous objection. Changing the type of transmission doesn't make the racing any better or worse, unless you mandate something that is unreliable enough to cause a significant number of DNFs.

What IS an issue is the point made in the discussion on the 593 - the width of the power/torque peak, and tuning the CVT to stay on-peak. That said, this is NOT rocket science. It's basic physics, and there is at least one F500 vendor who will sell anyone a pair of clutches tuned to a VERY good baseline. From that starting point, you can figure it out. In fact, I would state that pulling and tuning a F500 clutch pair is every bit as easy as setting up a Hewland Mk9 or a LD200 - and a lot less expensive.


The single biggest issue I ran into, though, was the variety of seemingly unrelated mechnical failures I experienced in F500. In a matter of a couple of years, I had DNFs or lost qualifying sessions due to:

• Failed left-rear hub, resulting in loss of a wheel at speed (CMP 2004)
• Hole in radiator due to the fire bottle attachment tab breaking off the chassis (Nelson Ledges 2004)
• Broken final drive belt (not clutch belt) - Race Lap 1 (CMP 2005). Belt was three races old - apparently snapped due to stress caused by chassis flex.
• Lost seal in two three-piece wheels (Hoosier guys nicked them while mounting tires - they gave way at speed on lap 1) (BeaverRun 2005).
• Broken chassis welds - multiple, generally in either the sidepod frames or rear suspension area. I learned to carry a welder in my trailer.
• Failed water pump (Glen - 2004)
• Starter solenoid failure (went through three in one weekend until I shock-mounted it) (Glen 2004).
• Holed piston (never found the root cause - EGT in left cylinder suddenly increased 200 degrees and went boom) (Summit Point 2005).

I could go on, but the point that I would make is that the reliability issues I dealt with had nothing to do with the CVT or two-stroke. They had to do with the high level of stresses put on the chassis by a car with so much lateral grip only weighing 800 lbs.

Now, if I suggested that we put in requirements to meet real welding standards, minimum construction requirements to strengthen key components, a ban on kart-based components, and a homologation system that would force builders to add gussets and reinforcement at the right locations, it could solve a LOT of the real day-to-day problems faced in F500. Somehow, though, I doubt it would do much of anything to change the perception of the class amongst those who don't actually own and drive these cars.

[lancer360]

Very good points Marshall. As a engineer and a newbie jumping into F500 I kind of liked the idea of the CVT. That wore off pretty quickly when I realized it was probably going to take several years to build up a solid knowledge of tuning the CVT. 6-8 weekends a year doesn't give you a bunch of time for testing and tuning to build up your knowledge of the various changes you can make to the system. On top of this, you need at a minimum a basic data logger so you can so you can see what the changes are doing. As a budget class, many are only using a basic EGT and RPM dash that only records the peak number. Unfortunately, I really don't see any fix for this. You can't spec a clutch setup for everyone as it would really hurt the performance of the cars when the conditions and track weren't ideal for that clutch setup.

Jetting the carbs wasn't really a big deal once you had the data, but getting that data would again take several years of running in all kinds of different conditions to build up a good baseline. Unless you get lucky and the previous owner has already logged this data and passes it on. While trying to get this data, if you make a mistake going too lean it will cost you an engine rebuild and your weekend unless you had a spare motor. I wonder if anyone in the 2-stroke community has tried to develop a EFI system based on EGT's since O2 sensors won't survive in the oily exhaust?

[Daryl DeArman]

For example: I've heard guys talk about "wanting to shift gears". Being someone who has actually driven a number of race cars with various types of transmissions, I find this to be a ridiculous objection. Changing the type of transmission doesn't make the racing any better or worse, unless you mandate something that is unreliable enough to cause a significant number of DNFs

Count me as one who "wants to shift gears". You may find that desire ridiculous and you are entitled to choose your race cars for reasons of your chosing, as I will mine.

I raced 2 stroke clutch karts for a few years, a shifter kart, a CDCRA car (5 speed sequential) an IT car, two EP cars, a FV and a FF. So I've ran the spectrum from no shifting at all to 30+ gear shifts on a 50 second lap. While there isn't any direct correlation between the quality of racing and the number of shifts some of us just prefer it.

[Marshall Mauney]

As a budget class, many are only using a basic EGT and RPM dash that only records the peak number.

I have a really hard time with this statement, even though it's been repeated many times in the F500 camp. A basic AIM system doesn't cost much more than a plain old EGT gauge and tach. Add in the price of a temp gauge, and you've paid for a basic karting datalogger with a wheel-mounted display. [MyChron 4 suggested retail is $429 with lap time, tach and EGT included.]

Frankly, I would suggest that some form of datalogging is going to be necessary just to get a final drive ratio set, much less doing any sort of tuning for ANYTHING on the car. I find it incomprehensible that anyone who is building a new car would even consider using anything less than a basic datalogger - it's like buying a knife to take to a gunfight.

6-8 weekends a year doesn't give you a bunch of time for testing and tuning to build up your knowledge of the various changes you can make to the system.

????

Perhaps for a new driver who doesn't know what an A/F ratio is to begin with, but it only took me a few weekends to get my chart built for the 494. I'm sorry, but I truly don't understand what's so difficult here. I've dealt with both carbs and EFI, and I frankly find carbs a LOT easier and quicker to deal with.

[Marshall Mauney]

While there isn't any direct correlation between the quality of racing and the number of shifts some of us just prefer it.

I agree that it's a personal preference issue - my point is that racing is just as good with or without a clutch/CVT/auto-shift. I've also run the gamut - RotaxMax, FF, FE, F500, SM, etc. The racing was good in all of those classes, and the transmission choice was WAY down the list of reasons to select any of these classes...except that the shifting class trannies were/are a lot more expensive. The cost of replacing a single gear pair in FF/FC/FE will cover several seasons' worth of CVT tuning parts and belts; the cost of a new FE clutch kit will buy a pair of CVT clutches; the cost of a replacement gearbox is enough to buy a used F500 (as my wife is very fond of reminding me....).

For those who like a CVT, there is only ONE option in SCCA today - F500. If you really want to shift gears and use a clutch, there are 25 other classes that provide that option.

Let me be clear - I'm not "against" bike engines in F500. I just don't think that the bike engine by itself is going to solve any of the problems that caused me to leave the class. From my viewpoint, this whole argument is just keeping people away by avoiding the real issues facing the class and creating an atmosphere of uncertainty.

[F five hunj]

Marshall,

I've never seen any kind of description on how to put together a data set to help guide your jet changes day to day as the weather fluctuates. As someone with a brand new engine type this year, and no data to use to guide my tuning, I, along with many people would find it quite helpful if you could describe that process.

I had my car out at a T&T two weeks ago in 38 degree weather and I was quite surprised to find my EGT's were only peaking around 900. I thought something may have been wrong with my data system, or a thermocouple type mismatch with the logger, but everything is working correctly.

Regarding the clutch tuning, you're all right, the basic principles are easy to understand. After a session, I think it's probably pretty easy to look at your data and figure out what, if any changes are necessary to your setup. What I think is much more difficult, is to be able to figure out what to change before the session, reacting to changing weather conditions etc....

[lancer360]

I have a really hard time with this statement, even though it's been repeated many times in the F500 camp. A basic AIM system doesn't cost much more than a plain old EGT gauge and tach. Add in the price of a temp gauge, and you've paid for a basic karting datalogger with a wheel-mounted display. [MyChron 4 suggested retail is $429 with lap time, tach and EGT included.]

I agree that data logging has come down in price and most if not all of the fast guys are using some type of data, but I still see many regional cars without it. Maybe it is a complexity or computer illiteracy issue and not money though. We could do a poll on the F500 site for curiosity sake. Anyway, many have the perception that it will take several seasons to develop a strong clutch tuning skill set as a barrier to entry.

[Marshall Mauney]

I agree that data logging has come down in price and most if not all of the fast guys are using some type of data, but I still see many regional cars without it.

Sure - but those older regional cars aren't the real issue. Anyone who has the financial wherewithal to consider a new car or a 600cc conversion isn't going to be limited by the cost of a basic logger.

Anyway, many have the perception that it will take several seasons to develop a strong clutch tuning skill set as a barrier to entry.

No argument - from what I said in my first post in this thread:

I believe that there is more perception than reality in this view (though perception can certainly impact an individual's desire to enter a given class).

Again, speaking as someone who has actually raced a F500, I don't see it as an issue. My view is that the issues that people outside the class perceive as the "problems" aren't the same as the issues that the people actually racing in the class deal with. YMMV.

[Marshall Mauney]

Marshall,

I've never seen any kind of description on how to put together a data set to help guide your jet changes day to day as the weather fluctuates. As someone with a brand new engine type this year, and no data to use to guide my tuning, I, along with many people would find it quite helpful if you could describe that process.

I had my car out at a T&T two weeks ago in 38 degree weather and I was quite surprised to find my EGT's were only peaking around 900. I thought something may have been wrong with my data system, or a thermocouple type mismatch with the logger, but everything is working correctly.

Get an air density gauge and forget about everything else. All of the other stuff - altitude, temperature, barometer reading, etc. - is used to determine air density, which determines your desired jetting. With a decent air density gauge, you just read the number right before the session and put in the correct jet from your table.

http://www.intercomp-racing.com/tech...ir_Density.pdf

[DB4 Tim]

Boys Boys Boys...be nice

[Evl]

As another one of the seemingly many F5->FE drivers, I have to also say that the carbs/clutches didn't seem like an insurmountable obstacle to being fast. (Not that I actually got there.) I figured there was more black magic in the rubber suspension than anything else, and I have as many variables in setting up my FE as I did with the F5.

[lancer360]

Boys Boys Boys...be nice

No problem here. We are having a good discussion on the various viewpoints from inside and outside the class.

[jim murphy]

No problem here. We are having a good discussion on the various viewpoints from inside and outside the class.

I think he is reacting to post #2 on this thread by Dixon who later got banned.

Jim

[iamuwere]

Clutching is not hard. I used the setup Q recommended and he will tell anyone! I never changed anything but primary weights between two sets. It was good enough to win nationals, solo championships, and stumble onto the podium at runoffs. Clutching is not complicated unless you make it so.

Another F5-->FE convert.

Jim

[captaineddie1975]

Clutching is not hard. I used the setup Q recommended and he will tell anyone! I never changed anything but primary weights between two sets. It was good enough to win nationals, solo championships, and stumble onto the podium at runoffs. Clutching is not complicated unless you make it so.

Another F5-->FE convert.

Jim

Amen! Because of his argumentative nature Dixon got himself banned again but there is a lot of his useful info on the www.f500.us site under the clutching category. As for data logging I use a Digatron DT-54K RMT-4. I also bought the software and toggle to download into my laptop. I get 3 egt readings (one I leave near the carb opening to get ambient temps) RPM MPH and water temp. I also have the Laptime attachment and the button to push so I can get section times. I bought most of this stuff in 2008 and don't know what the current cost is but I bet I didn't have more than $500 in everything.

[tedsimmons2]

I find it interesting three (3) former successful F500 racers turned FE racers have commented “clutching is not complicated unless you make it so”. That statement basically shoots a BIG hole in one of the main tenants of the MC/Rotax argument. While I’ve not yet been as successful as Jim, Marshall, and Brian in F500 I also have not found “clutching” to be an issue. I purchased new clutches from Mitchell Racing Services and asked that they be setup with a really good basic package and have not had to make any changes except to add or take off weight in the primary clutch.

Much of what has been labeled as “outsider’s comments” about our class can and should be addressed by current/former F500 races to help dispel myths and rumors as to the complicated nature of racing a two-stroke/CVT/rubber suspension car. Every time I pass a FF I’m reminded this class provides incredible racing value for the dollars spent.

[nulrich]

I've been enjoying this discussion as an outsider. I know very little about F500 other than just reading through the rules in the GCR. How effective is the rubber suspension? Is it essentially a solid suspension, or do you get a fair bit of movement? I would think you could come up with some innovative methods of making whatever wheel rates you desired, but how stiffly are these cars sprung?

Is the chassis designed to flex like a kart?

It seems F500 and FF have comparable lap times. Are the cars significantly different in cornering or straightaway speeds?

A CVT is certainly an elegant engineering approach, but I have to admit my one objection to F500 is the sound, just doesn't seem "right" not to hear a revving engine! But I know it's not logical.

Nathan

[Marshall Mauney]

How effective is the rubber suspension? Is it essentially a solid suspension, or do you get a fair bit of movement? I would think you could come up with some innovative methods of making whatever wheel rates you desired, but how stiffly are these cars sprung?

It's not that much more solid than most other modern open-wheel designs, and certainly has more compliance than a kart. There are indeed some tricks to damping the spring action of the puck, as well....

You can actually get a LOT of movement in the rear suspension of most F500s. The 4-link designs allow a lot of shifting to manage side-to-side weight transfer. Keep in mind that they have a solid rear axle, so you have to unload the inside rear wheel to get it to turn. Thus, the balance between front-end caster and rear-end weight transfer is crucial to handling.

Is the chassis designed to flex like a kart?

No - at least not intentionally. The rear suspension handles it without needing flex.

It seems F500 and FF have comparable lap times. Are the cars significantly different in cornering or straightaway speeds?

Yes, as well as in HOW they corner. They are very different beasts, with the FF more "refined" and the F500 more raw and visceral. You have to be very aggressive with a F500 to hustle it around the track - it's a real kick to drive once you get used to it.

[Evl]

When I first got into an F5 I was amazed at what ~30 years of engineering and ingenuity on the part of the chassis builders can do to turn 4 pieces of rubber shaped like hockey pucks into a working suspension.

[jim murphy]

When I first got into an F5 I was amazed at what ~30 years of engineering and ingenuity on the part of the chassis builders can do to turn 4 pieces of rubber shaped like hockey pucks into a working suspension.

Except for the coil-over shocks the front end geometry of a FF and F5 are very similar.
The rocker arms really helped the rubber pucks to allow bigger wheel movement - mostly in the rear for greater rear end grip.

Jim