Home Forums Shifter Karts Moto engine timing advance

This topic contains 24 replies, has 7 voices, and was last updated by  Bill Schmidt 4 years ago.

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  • #31130

    Bill Schmidt
    Participant

    How far advanced from stock setting does anyone go on moto engines? 4, 6, 8, 10 degrees?

  • #31131

    Chris Hegar
    Participant

    If your talking about open motors then the world is your oyster with a programmable ignition. Towards the end of our 250 twin program BRC was headed in the direction of a different curve for each gear selected. Don’t know how that turned out but it was on the table. Your going to get 100 different views on degrees.

  • #31141

    Bill Schmidt
    Participant

    Well, I am talking about scca rules. I am running the non-P.I. weight of 385 lbs. But porting and ignition advance is wide open.

  • #31167

    James McMahon
    Participant

    You mean static advance then? I dont have a number for you but will say that I think thats going to be hard for anyone to give you a solid number. It will depend on your compression,  squish (area and shape), fuel, pipe etc etc.

    Plus on such a short run you could maybe get even MORE aggressive. Test 0.1mm increments at a sprint track for a single lap (or two) and see how it goes. Even include your launch. Thats the only way to really find out I think. Start with wherever a SKUSA timing plate fixes it and advance from there.

    Buy a couple pistons :)

  • #31174

    Chris Hegar
    Participant

    Honestly Bill for AutoCross your not going to see much in time gains from 1 or 2 hp differences which I think at best is about the most your going to get playing with factory timing. In that arena I’d spend my money on the softest qualifying tires money can buy. Grip will gain you massive time on a green surface like that with minimal wear based around how long your running.

  • #31200

    Bill Schmidt
    Participant

    James… Yes, I do mean static timing, as I am not interested in P.I. and its extra weight penalty. I have no idea what a skusa timing plate is.

    Chris….1 or 2 hp sounds pretty good for free hp. Everyone I know of already uses MG greens, myself included.

  • #31208

    Chris Hegar
    Participant

    If your looking for a hp advantage buy a 250 single it will eat them alive if you can keep it between the cones.

  • #31261

    Bill Schmidt
    Participant

    250cc motos are not allowed in scca autocross.

  • #31280

    Chris Hegar
    Participant

    Pop a big bore kit in your 125… winner winner chicken dinner.

    BBBBRRRRRRRRRPPPPP! BBBBBBRRRRRRRRRPPPPPP!

  • #31289

    Bill Schmidt
    Participant

    Also , not legal

  • #31298

    Chris Hegar
    Participant

    I never said it was legal. I bet tech is marginal at any of those events especially with the karts. Just sayin if you want free fun power without banging your head and wallet against the wall bore it otherwise driver will be about 90% of the speed with Autocross. Best memory and car control will win +/- 2 hp isn’t the answer. To many people feel they get out horse powered when that’s not it.

  • #31299

    Bill Schmidt
    Participant

    Try telling that to the guys that have 45hp. I have about 30hp.

  • #31301

    Chris Hegar
    Participant

    They don’t have 45 hp, they have a dyno printout of a motor that has 45 or they have a big bore kit already.  ;-)

  • #31305

    Bill Schmidt
    Participant

    Well, after about 5 years of autocrossing karts, here is my take on the hp ratings:

    spec Honda… 34hp

    mod Honda with stock ignition…39hp

    mod Honda with PI…….45hp

    ICC engines……………….48hp

    All are rough, approximate figures

     

  • #31447

    Chris Hegar
    Participant

    I’ve seen a good spec Honda blow away some very good open moto with the works in upgrades, depends on the track, driver, ect. Myself I’ve been at it for 25 years running everything from 4 stroke low HP to 250cc twin 100 hp motors. We currently have 3 stock moto packages and 2 ICC in house all running long track and some sprint. Even on a full 2 mile course your only going to see about a 1-1.5 second difference in lap times ICC to Stock moto, I have all the data to support that. If the numbers you have given were correct that would put a 14 HP difference between stock moto and ICC. That type of difference would mean the ICC would lap a stocker on a 2 mile track in no time at all and the overall lap time difference would be massive. Not trying to be mean or condescending but your rough numbers have way to much spread. 125 hp variables are not that great from one to the other it’s all 125cc displacement, there is no magic. Drive ability on the other hand can give a false since of additional HP. An ICC has better power application that even stock moto, the stocker is harder to drive based on big bottom torque when you hit the throttle. An ICC does have more peak power based on RPM but often the bottom is easier on the pilot because it’s a soft hit.

    Just my opinion.

  • #31464

    Bill Schmidt
    Participant

    Chris,

    Take the 4 categories/specs that I listed and replace the hp #’s with your own to let us all see what your opinion is.

  • #31477

    Chris Hegar
    Participant

    Your going to get 20 opinions on dyno hp numbers which can all be related to calibration and or who’s the biggest BS machine trying to sell motors. What I can tell you is that the spread your showing is to great and 48 is into open alky motor range, I think many might agree with that statement. My opinion on dyno testing will always be the same, does it run consistent from top to bottom and can it be replicated on track, numbers are nice but don’t buy into it until you see and feel the difference. I can get you a great number  just before it blows up.   ;-)  My dyno is a 2+ mile long track and it works great.

  • #31478

    Jimmy McNeil
    Participant

    I’ve heard numbers as high as 42hp (debatable) for stock Honda and 48 for the latest and greatest icc’s. A SCCA driver on a 48hp national caliber ICC would get smoked by a top 10 SKUSA driver on a stock Honda any day of the week. I know its fun as heck pumping up an engine with Pi’s, high comp, big carbs etc etc, but the bottom line is, focusing on your driving would prob make you faster than additional hp, especially on an autocross track.

    • #31492

      Vernon Head
      Participant

      I see once again, not many answers to the original question, just a lot of “learn to drive better” comments.

      I’ve never seen any of these “Top 10 SKUSA drivers” win a national level autocross event, and if they did I doubt they would smoke the rest of the field. It’s much harder than it looks. Much different than showing up at a nice, smooth, tidy track and getting hundreds of practice laps before competing. First, it’s done on some pretty rough surfaces, not smooth tracks. You walk the course, get no practice laps, and usually 3 to 4 runs and they aren’t back-to-back. The courses have a much different look, being laid out with cones. It’s hard to memorize a course after only walking it a couple of times. The line is not easy to understand since there is no road to follow.  You can’t look ahead very well because all you see is a sea of cones. Everyone is making mistakes out there.

      I have a lot of respect for WTW racing. I’ve done it, and it’s a very tough sport but for different reasons. I like to practice at kart tracks to get seat time, but I also have to work on skills specific to autox.

      Even if I need to drive better, hp will still make ME faster. I think it’s true for everyone. Otherwise, why do we have all these engine builders?

       

  • #31540

    Bill Schmidt
    Participant

    When I read Vernon’s posting, I had to stop and think,”Did I post this, or did Vernon?” Thanks Vernon, I couldnt have said it better myself. I agree 100%.

    Chris,      I didnt ask for 20 different opinions, I asked for yours, but didnt get it?

    Jimmy,    How do you propose that I “focus on my driving”? I have over 50 autocrosses on my same shifter kart in the last 5 1/2 years. Do you think that 55th or 60th event is going to magically make be a winner? I bet an extra 5hp would help immensely.

  • #31547

    Jimmy McNeil
    Participant

    Sorry if I offended  you guys.

    When I was club racing, we put 38mm carbs on our icc’s and were slower. To much wheel spin out of the corners. Moto engines are worse, big time bottom end, high comp will add bottom end so will advancing the timing. Im assuming an autocross track is very low grip, prob already a challenge to get it to hook up off the corner.  Also, if you pump up a moto engine, they become very finicky, hard to tune and easy to damage. Ive raced both built moto and stock moto in the same weekend and in a few sessions was faster on the stocker. The built moto had a very small tuning window, if you didn’t hit it rite, it was a turd.

    You can work on your driving in places other than an autocross track. Go to the local sprint track (if you have one) and pound out laps. Learn to drive in a little deeper, be smoother on the wheel, spend time changing the chassis, learning how to take out and add grip etc etc.

     

     

  • #31548

    Matt Dixon
    Participant

    Bill have you made chassis changes in those 50 autox’s?

    Tried different axles, hubs, wheels???

    As Jimmy was saying HP isn’t always they ticket to quicker times

    94y

  • #31552

    Chris Reinhardt
    Participant

    The same solo national champion won with a mod Honda PI and after with a mod Honda stock ignition a few years back.

    Weight advantage goes to non PI ignition…

    I don’t believe anybody has won anything in karting with a KX125…  I would be willing to bet cash money, a “stock” Honda would eat that KX alive no matter where you put the timing…

    CR

    Chris Reinhardt

    CR2 Motorsports

    http://www.cr2motorsports.webs.com/

    XV Racing Products

    http://www.xvengineering.com/

    ­­

  • #31582

    Vernon Head
    Participant

    That’ pretty good knowledge, Chris. Yes, Paul Russell won once with Pi and the 25lb penalty. But  never with a  stock Honda. It was modified with stock ignition.

    Jommy, thanks for what you said. Yes, seat time, hubs, alignment, etc are more important than power.  But there is nothing wrong with working on ALL aspects of getting faster. That includes little details like ignition timing.

    I have read that too much advance can kill your over rev.

     

  • #31588

    Bill Schmidt
    Participant

    Jimmy….I have recently joined the local sprinters and have pounded out a few laps.

    Matt….I have changed toe-out, moved seat to the rear, added seat struts, tried 4 different carbs, 3 different tire compounds, different sprockets, the list is endless. Havent tried axles since 1 3/8″ size dont exactly grow on trees.

    Chris….I agree, but dont have the $1000 or more for a used Honda engine.

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