Post by Bob Vehring on May 3, 2012 15:17:54 GMT -5
I realize this is a very slow part of the year, very few people watching forums. It is however the time when the rules you race under change and you have right now to talk about it.
Currently there are some proposals being passed around that would change the carb rule from the oem part in CHAMP class, to an aftermarket carb. No carb has been chossen at this point but several are suggested, Mikuni, Keihen and Delorto ranging in size from 18mm to 21mm. Its not my or Regans list, or proposal, but I would certianly ask that a spec size Tillitson be under concideration also.
In the next month or two, sorry I don't have the date, the ISR Rules meeting will be held and a decission will be made on the rule for next year. I sincerly hope people talk this out so you have a say in your rule for next year. Bob
Post by Bob Vehring on May 3, 2012 17:21:05 GMT -5
Here is the copy of the proposed changes I recieved, Again we here have nothing to do with it. I'm looking for oppinions from the racers and their various series so their thoughts can be sent into ISR
April 28, 2012
SUBJECT: 120 Champ Carburetors
Taking into consideration the amount of money a Champ owner has invested in the current offering of modified units, one would think they would and should work perfectly.
However, quite the opposite seems to be the case here. Champ owners and engine tuners have had to deal with these units for over 10 years now without having a single rule change implemented towards improvement.
Icing, Sudden Unexpected Lean Conditions, Peruiduc Throttle Hesitation, Vibratring Main Jets & Internal Epoxy Issues are just some of the negative features and characteristics owners are forced to deal with when using a modified OEM carb. The bottom line cost of purchasing these highly modified units is also insane!
If a solution could be agreed on, it is my thought that one would probably be wise to stay within the current flow characteristics of our existing carb packages. This would hopefully assure some level of engine reliability.
With this theory in mind I began to compile flow chart information for the comparison of our current OEM units vs. some popular, readily available slide valve type carburetors.
NOTE: All flow testing was done using 10.00" of vacuum.
The aftermarket carbs listed here are all commericially available from several distributors. They all offer a wide range of tuning components. The retail prices range from $65.00 to $120.00. Mounting flanges and throttle cables are also available for all of the above as well.
Pete, I agree with that, but what I think is important is these changes be well thought out first before other issues are created, Some thing to think about.
Some flow numbers are given in the proposal for different brands of carbs. I know that flow will vary with weather, I don't how the testing on those carbs was done, but to be relative it wuld have needed to be done all at one time or corrected for weather to be compared. Then that needs to be conpared wide range of the current carbs available for Champs out there now. Theres alot of differance between them.
How these carbs fit on the different sleds would also need to be checked. Their different physical size and each chassis is different. In ovals custom chassis are used by some. You do not want to create a custom intake manifold situation because theres power differances there.
Currently the Honda/SkiDoo carb can not be opened up to the same point as the A/C or Pol. it is still fairly competative. I would like to see some serious dyno testing done with these carbs to make sure power remains equal between the brands , not that one suddenly wakes up and the others have a hard time competing.
Current rules have created a carb that while st. based, because of rules in place, is very exspensive. How will these new carbs be governed? I build alot of big Mikuni carbs for my hot rod trail sleds, simply specing a size and using a no-go won't give you a cheap carb. Alot of work can be done to slide carbs and its would take some serious rules to keep them in line other wise you have what we have now. Right now alot of racers have big money stuck into their carbs. I doubt they'll want to throw those out, just to have to turn around and stick again that much into a different carb.
The reason I suggested a spec size Tillitson carb is because of its ajustability. Anyone now racing knows you have to dial in you carb jetting now continuosly throughout the day as weather changes. In the Kart racing world, in the open class, we can run any carb we want, slide or butterfly. 99% choose a Tillitson simply for the reason it has low and high speed ajusting screws on the side of the carb. You can dial it in instantly with just your hand. No parts to change. Slide carbs have different, P. jets, main jets needles, needle jets, air jets and slides. All require that the carb be taken apart and the various parts changed. You can't dial it in with the engine running while watching your EGT and if your stuck on the grid waiting for a while and weather changed, theres nothing you can do.
I am not against this change at all, but before it moves forward, I think theres alot of questions that need to be answered and alot of testing to be done to besure we just don't create more problems
Any time you make a change to the ISR rules, it costs racers some money. It would be interesting to know who is suggesting the changes. I do not know if it is the case here or not, but when someone asks for a rule change, there is usually a motive that is not always the bast for the sport. We need more information and more testing, as Bob suggested above. Since this topic has not come up to An ISR meeting in the last 8 years that I have been going and this is the first I heard of the issue out loud (believe me I know the OEM carbs and modified OEM carbs can be a pain) I would be against any rule change without a lot more information. Making rule changes too quickly can be baddddd! Glad to discuss further and perhaps you can sway me, but I will need a lot more info!
Post by Bob Vehring on May 6, 2012 14:18:36 GMT -5
Yesterday I was at the ISR rules meeting for big sleds, privately I asked someone fron ISR and right now they didn't have a date on the 120 meeting and to the best of his knowledge, no motions for change have come in yet.
Of the people I have to talked to, all were open to concidering this, but all also wanted more testing.
So lets get to the problem, if we ASSUME, that these carbs would be used stock, and there would be rules developed to govern that, using the base costs suggested in the proposal above, $65- $125 each, lets use $100 as the middle avg price. Now if we want to concider each of the 5 carbs talked about here, some one or hopefully multiple people/shops would need to buy $500 worth of carbs. They would need to flow test them on either a flow bench with weather station or be able to do all 5 quickly at the same time.. Then each of the 5 carbs would need to be dynoed on the same dyno, again with weather correction on all 3 engines to check how they really make power. Untill we really understand how these will need to be jetted, that means quite a bit of money invested in the various jets used for each carb. Next each carb would need to be checked for fit with the engine instaled in each of the chassis,remember some Pol use the stock (back) carb configuration, some come out the side.. This needs to be check for not only fit but clearance for the various bells or air horns some people choose to run, and filters if they run them. We need to know if there is room on each brand for sufficiant air flow and this can be done without serious cutting of the bulkhead to the point of loosing strenght. The last thing needing to be done is real world testing to make sure it really runs well on the track, which at times is certianly different then what the dyno shows..
As you can see, seriously testing this will be about $700 and several weeks of time, then track testing. No idea on who is doing this testing.
Post by Mike Malueg on Jun 1, 2012 11:34:57 GMT -5
I have been thinking about this for a while now and I can't say that I have come to a final conclusion. However here are my thoughts.
1. Champ racing is expensive, but i don't know that a carb change is going to make it any less expensive in the long run.
2. ISOC tech can't even tech 3 MFR carbs (even though they are modified), how are they going to tech and know the specs for other commercially available carbs. Sounds like an opportunity for the not-so-honest daddy's out there to cheat.
3. If we really want to look at reducing the cost of champ racing, why don't we look at eliminating ALL modifications and going to a bigger stock engine where zero changes can be made. These engines can be bought brand new for around $700 - $800 and can be bolted right in. To me, this seems like a better and more reasonable solution. Then we wouldn't be pushing engines to their limits (I understand we will all optimize the engines, I'm talking about the extra mods pushing an engine to its limits) resulting in unplanned mechanical failures leaving a happy child in tears.
Like I said, I'm not certain about my final stance. But I don't think a carb alone is going to make it cheaper for champ racers. You really should spec a whole new engine that can run stock.