Ok, I need some help.
03 F7
20/41 w/10 tooth drivers
I'm trying to get to an RPM of 7900 through the shift 8000-8100 at the end.
This is in 500'. assuming everything else is good (Pipe hot, belt deflection good....)
I'm getting off the line like a rocket. like three sleds ahead, however i'm completely shifted out by 300' and cannot gain any more Rpm. So there catching me.
Clutching:
185/300 pri. spring
weights: Cuttler MAG 62 pulled at 7300-7400. Now gound down to 58gr. pulls at about 7500-7600. Cuttlers use a more agressive profile.
Helix 60/53
Secondary spring D&D purp. (Heavy) Tightened up in 4th hole.
I also use a larger roller in the Sec. this will make the helix act steeper.

I thought I was heading in the right direction by taking weight out. But I'm not sure. Everyone else I speak with is running a stock profile at about 70-72 gr. along with less angle on the helix.
I tried a 60/44 helix, It made the sled even flatter on the end. I'm looking for Ideas. Should I keep taking weight out to get the rpm up and will this slow the shift a little at the end. Keeping me from over shifting.
Or, scrap the agressive profile weight and load it with the heavy weights and get a lesser deg. helix?
What is happening is I'm over shifting. Too much,too fast. With the great leap I'm getting at the start it keeps me in front. But I shouldn't get shifted out at all with these gears.

Thanks for any input

Matt

I'm no clutching expert (especially with AC) but, heavier weights tend to work better for drag racing (with matching stiffer springs to boot). They tend to grip the primary much better. Trick is to find a balance. Try two / three more grams from stock. Heavy tip comets are good for top end. Find a spring that's stiffer on pre-load but relative the same as stock on shift out.

What's the stock engagement speed and top RPM? your rev limiter (cdi) may be effecting your top RPM too. Nothing you can do unless you reprogram.

Check to see if your getting full shift out on the secondary. Mark your sheeve and helix with a felt marker and do a run. Check to see where the belt and helix ends up. Generally speaking a steeper helix means a more aggressive shift-out (lets the secondary "slip the belt" to open up faster). If too steep it may translate to belt inefficaintcy and hot clutches. Do a few runs and see how hot both clutches are getting. Hot clutch = Poor efficience. I suggest you re-test that 60/44 with a stiffer secondary spring and more pre-load. If secondary is still too hot, work you way down to shallower helixes. The more you do that, the more you will have to rely on calibrating your primary to ensure good acceleration. Shallow helix = better grip = better top end.

You may already know all this. My two cents for what its worth.

Thanks for the reply.
The springs Don't get any stiffer for the sec. and the best you can do on the pri spring is 190/335. I have a 185/320. Didn't work. What your missing is the profile of the weight is more agressive than std. profiles so it will behave like a heavier weight.

I do get a full shift, at 300'. Completely shifted out. I should never be able to completely shift in 500' with the gears I'm using. I think I could help the problem a little with a more shallow start angle on the helix but I don't want to lose the jump I'm getting.

Matt Gilbert

Hey Matt,

I'm not there to see what your sleds actually doing but, it sounds like to me the little 58g weights arn't pulling your load. Call me a pesimist but, I don't buy that "acting like aggresive weights" speel. General rule of thump for weights is the more curve the fly weight has, the more aggresive the upshift is. The shallower the curve the "slower it upshifts". I would do one of two things; buy some notched weights that are heavier then stock or get a set of comet or AC racing weight (lots of curve) that have the weight on the tips (for better top end).

That is a stiff spring! Unfortunaly I'm still learning this stuff too. But, try a few different helix spring combos. Fortunaly for you AC helixes are cheeper then all the other brands.

Good luck.

I'm trying to get to an RPM of 7900 through the shift 8000-8100 at the end.
This is in 500'. assuming everything else is good (Pipe hot, belt deflection good....)

I used to think like this about climbing rpms to the finish, but now I don't after being on an inertia dyno watching an engine "accelerate" then seeing dyno numbers, boy have I changed my tune.

I have actually never heard anyone explain to me why tuners want to tune their clutches to reach an RPM that is prior to peak power [in your case 7900] and then make the engine labor to rev to power peak for the last few hundred RPM's. [in your case 8100]

Why does one not want to clutch the engine to be on power peak RPM for more of the run?

For lack of better numbers lets say:
You have slight over 80 foot pounds of torque beginning at 7900 RPM's.
Your engine remains at slight over 80 foot pounds of torque until exactly 8100.
Your power area then to be 200 RPM's wide.
Your actual power peak is at 8050~8075 RPM's on a dynograph.

Would you not want to be on peak torque for as much of the run as possible; Which looking at your powerband of 200 rpm then clutch for 8100...8150 RPM's?

The beginning of the run at 7900 and let it climb to 8100 means that you will purposely be running with less average HP thru your run.
At 7900 your engine makes XXX.0 HP and 80+ foot pounds of torque.
Quoting Freddie Klies...
Why would you want to puposely run without as much power than your engine actually has?
This as SUPERTUNER calls "A Rolling Bog".
You are making the engine struggle by not allowing it to run at it's power peak.
Your engine Bog's from 7900 and grinds out a bog of 200+ rpm to it's power peak at the finish line.
..............It's power peak "AT" the finish line.....
What about all that distance before the finish line back to the start line when the engine was NOT at power peak?
...end quote

Here is a dynoplot of my 440 engine.

> 7650 - 65.2 @ 86.2
> 7700 - 66.6 @ 88.9
> 7750 - 66.3 @ 90.4
> 7800 - 66.0 @ 90.7
> 7850 - 66.5 @ 92.0
> 7900 - 65.8 @ 91.4
> 7950 - 65.5 @ 91.5
> 8000 - 64.6 @ 90.8

In a case like you mention, I would climb from 7650 from the start line and then accelerate the engine to 8000. Since secondaries are Torque sensitive and shift in proportion to the torque applied, would I not want to be at 8000 instead?
I will now run at power peak for as much of the run as possible.
When you run over your torque peak and torque starts to drop slightly, the secondary is going to think you "The driver" let off the throttle a bit and upshift slower.

After racking my brains with efforts of climbing rpms, and rarely getting a consistant time, I now have my engine at pretty well at a small rpm window from start to finish line. I am still having a bit of a time with it in the first 30 feet or less due to me trying to pick a "required" start helix angle, but once hooked up my engine hardly varies 70 rpm from bottom to top.
Since I have done this, my times have been consistant consistant consistant. I can repeat runs.
I get RadChad or Rotaxman "experienced driver" to run it and they are slower, but their runs are the same time.
I have it to the point now where I change a main jet, my times change and e.t's get worse.
Now for me when I change clutching, the results will give me a direction to go for the next change.

I will add from watching my engine go over 8100 in a race...it for me is disastrous.
I cannot believe how much my sled lays down and accelerates slowly.
Running at below 8100....wooo!!!

is this for grass racing...if so ive been to the last 5 in michigan. we are running a firecat f7. the rpm you want is 7600 to 7700. almost all of the f7 are running 70grams and a red spring.

IMO dynamo joe, torque is to GET you moving, horsepower is to KEEP you moving. thats why you clutch 200rpms low then climb up to peak hp rpms. i do have alot of respect for you, joe, maybe your on to something.

Well if Horsepower is [Work/Time] and you have 6 seconds to do a certain amount of work...
Which one would you chose to use?
Lets eliminate all the numbers in the middle and use the data from both ends of the power curve.

Rpm.....Tq.........Hp...time
7650 - 65.2 @ [86.2 / 6 ]=
7950 - 65.5 @ [91.5 / 6 ]=

Being that you have to move the sled off the line and there is grass, dirt, skegs in the ground, the load of the clutches, heat building in the pipe, speed increasing, I would think that I want to clutch a little over the peak power so when the sled is set going down the track, the engine has a better chance of pulling down on the peak power...peak torque.
Theoretically there would be no rolling bog as you would always seem to be on the power peak...to as you say "keep you moving" ? :)

Gasman, I think your not getting what I'm saying. Using more shift profile will load the motor harder. You can get the same force in the pri. by using more angle and less weight or more weight with less angle. By angle I mean the contact point of the weight and the center of mass of the weight. The advantage of the lighter weight is more engagement rpm without having to grind notches. The weights are pulling the load I believe, too well. I just spoke to another guy that was telling me there are some guys using a 53gr weight in order to get more agressive off the line and run the rpm up to near peak right off the line like Joe was saying.

Joe, I always understood the idea loading the motor at the lower side of the torque curve was too build heat in the pipe. The idea being you can't get the pipe up to temp. on the stand without getting the motor too hot. Unless of course you have a tight pipe, designed to build hp quickly.

At any rate I'm going to test both schools of thought. I'm going to take a little more weight out and try a more shallow start angle on the helix. This should let me do what Joe is suggesting.
I will also be trying 72gr weights with a std profile. I'm going to have to grind notches to get the rpm up off the like. This set up will also require less angle in the helix.

My guess is the lighter weight will pull harder, quicker but lose a little on the end ascompared to the heavy weights whitch I believe will have more pull from the mid to end. I'll let you know what I find.

Matt Gilbert

No, no, I read you loud and clear. You just said what I'm was beating around the bush with. There are many different possible combinations you can use. I'm just telling you what I've tried and know what works. I've tried the notched weights and know they work. I've also tried a stiffer spring on pre-load to increase my engagement slightly. That works. As long as it does effect your peak RPM, thats fine. Personally, I've used heavy weights for drag racing and know they work to grip he belt better (sometimes too well). There is nothing wrong with loading the motor a little more then stock. As long as the engagement RPM and peak RPM are acceptable. I'm with Joe, the faster you can get to peak RPM the better. If you want to heat your pipe, well get a track stand and warm it up before a race. ;o) You could always find out if the new 440 red button and CDI works on your F7 if it means that much to ya?!? Sorry I'm being facetious. ;o)

Another suggestion I had is the AC race manual have quite a few race set ups for many application. $65 CAN.

I'll stop now before I put my "foot in my mouth".

Cheers

joe, i would use both. but you have done more testing than me. im a snow racer and my dadinlaw races f7 in grass. is your tach calibrated? why is your sled faster when you over rev it? this may just be typical of a small engine (440) also. i hear those are a ##### to clutch.

Gas man, I'd say were on the same page in understanding whats happening.I always seem to end up taking weight out. No matter the sled.

I'm just fishing for opinions and getting great input.

As far as warming the sled on the stand the problem with that on the EFI's or even other sleds is they will go into a safe mode when the water temp. gets too high. On the F7 it goes to a rich mode, other sleds will retard the timing. Probably not a problem if you have a race program but stock its in the program. So that would mean a heavy weight would work better using the logic of loading the motor to build heat.

Matt Gilbert

if your worried about the safe mode, go to radioshack and get an adjustable resistor. 140° f is 750k resistance. so unplug you temp sensor and wire the resistor in. we will be trying this at hastings this weekend.

Tifa, I'll be looking for you on Mon. I've had problems with this sled going into safe mode while trail riding. Intrested to hear how it works for you this weekend.

Matt Gilbert

were going to the shootout friday. we cant seem to get this pig down the track. maybe we are encountering a safe mode issue. the first pass is always the fastest and they go down from there. sometimes .4 off the field. ill be sure to fill you in.

You know for sure your secondary is shifting out? That big secondary spring comment stirred thoughts of two much preload which obviously would yeild the same results. If somebody touched on this , I readthe post quickly but I personally would look there. The whole building up to rpm thing is a cold motor, cold pipe, grass drag , technique which I`m sure joe is aware of, ya made a good point but the motors max power rpm will change as the pipe heats up, and not all sleds can be fortunate enough to be optimum on the clean out stand without building excessive coolant tempature which also drags you backward.

Dynamo:

My experience with setting up the clutches to work below peak "hot" power is just that. When you take off "cold", the power peak is a couple hundred RPM lower. As the pipe builds heat, the power peak comes up a couple hundred. I would say that this trick is better for trail racers who sit around BSing and then jump on and race with a colder pipe. Does it work? I don't know for sure. I know several people that subscribe to this way of thinking and their stuff runs real well.

Just my $.02

I understand what you say.
I was being very specific for the discipline that was originally mentioned. [500' drag]

I design my trail kits to run at peak pretty well straight on the money. They run straight shift rpms with the settings I provide. Have large angle at start to load engine for brief period of time to take advantage of cooler pipe condition, then progress to lower angle to take advantage of pipe heat.

My personal sled slight overrev's by about less than 100 rpm when cold because of way I clutch for 90% of my terrain. I change helix when I goto other areas, but for where I do 90% I really enjoy the present setup. I have a suspension that is valved stiffer than factory sno-x calibration which is required for how I drive.
When you get into deep bumps that cycle the suspension fully with stiff sno-x suspension, then you need engine to be "there" and not come in lower than peak as that could be the difference in clearing or casing a whoop. Its ok to do that at low midrange speeds where you are on somewhat flat trail, but not at high speeds of 50 mph in extreme terrain in heavily loaded clutch conditions.

I always keep the hood ducts closed and have even taped off vents.
I like gobs of underhood heat in the early part of the day when its crisp and cold, then when the day progress late into afternoon "If its warm out", I will open up a vent near the upper part of the hood.

I kind of skimmed over most of the post, but reading your first post I would say your heading in the right direction by taking weight out. Im not sure exactly how the ac helix numbers stack up but I would look for some lower angles to grip the belt and bring your rpms up. Heavy weight and high helix = low rpms.

Originally posted by tb2@Oct 10 2003, 01:15 PM
Heavy weight and high helix = low rpms.
Generally speaking that is the case. But, I think you’re over simplifying it. If you kept the spring variables the same and added more weight, naturally your engagement and peak RMP’s decrease. Your not taking into account how the spring rate effects engagement RPM, peak RPM and shift rate. To give you an example my 2001 Pro x 600 stock has 58g with an almond / red spring (165-310) engages at 4800 RPM and peaks out at 8100 RPM. I put in both 60g & 62g AC weights with a super-torque black spring (?180?-360). This time she engages at around 4300 to 4500 RPM and the 60g still peaked out at 8100 RMPS while the 62g “bounced” on the rough terrain between 8000 & 8100 RPM. Needless to say my shift rate was not as desirable and the 62g weights did not work with the driving I was doing BUT, I only cared about my top speed and I still achieved the 8100 peak RPM with the 60g heavier weights. I still had options to play with my shift rate to suite a different style of driving!

But, I do agree with you on the helix angles.

matt

friday just before we left to go to the races we found a malfunctioning "smart" valve in the gas tank. we spent all week going over the sled with a fine tooth comb, checking everything.

we did not try the resistor because we found the problem. if your sled is going into safe mode the temp lite WILL come on, if it doesnt thats not your problem. you may want to get a new temp sensor or check the old one.

Tifa, I only had the temp. light come on once at the end of run. It was about 85 deg. that day

What was the valve doing and how do you check it?

Matt

there was a recall on these for this sled. connected to the pump in the tank there are two of these. one front, one back. they close when they are not in fuel. the back one was sucked in on itself. to check it we just looked at it, outside of the tank, after we took it out. this probably isnt your problem.

have you removed the airbox?
where is your air temp sensor mounted?

Haven't removed thebox, but I do have a 4" intake. Air sensor is in the stock location.

PM. me

Matt

arent you running grass?

I don't have only a clutch prob.

I've been having problems getting rpm up. so I finally let it rip on the stand. Runs up to 7500 hard and hits a wall. Like it has a rev limit. I found a smart valve stuck and removed both. Same result, 7500. Shortened center distances ( maybe the belt is too short) No, thats not it. Then all of a sudden, 8200 and it hits a wall there. I would think on a stand I should be able to run it up to what ever my nerves could stand. Any Ideas?

Stock ECU, Valves clean and move freely.

Thanks

Matt Gilbert

One time I work like a dog on my friend Alan''s XLT Polaris to figure out a problem.
Sonofabeotch would barely muster 8300 on the jackstand but drive sled on the ground, 7000 rpm and that is it.
No more rpm. Just "Blaah & Sputter" Nothing sounds worse than a sick triple.
I was just sick after rebuilding the guy's engine for him.
Because I could not find the source of this problem, I spent hours of tearing all peripheral components apart.
While I was loading a full clip of #5 slugs into my shotgun, pointing at the XLT, I spent a moment and asked the owner of what he changed before he brought the sled to me.

Alan mentioned that he changed the spark plugs and plug caps.* He continued that he purchased (No Resistance) components.
Alan's brother tells him to run "0" ohm plug caps and B9ES plugs. "Yeah this will make more power." he says..."Less resistance = more hp"

I said...."DUH"* I point the gun away from Alan's sled and started to wish his brother was standing in front of it while I massage trigger with finger.* :hallo3:

I think how the heck could Alan's brother believe this and for me to agonize thinking I put something together wrong.* All this work for Fk-All. :cussing:

As I put the shotgun on the bench, Im thinking...Hmmm:
Should have B®9ES plugs.
Should have (5000) 5K ohm plug caps.

I check and lo and behold..."0" caps...B9ES plugs.

Lets talk theory here...
(I*R)=E
(I)Amps * ®Resistance[Ohm] = (E)Volts
For fun lets say this Example for lack of better numbers:
[im just pulling numbers out of the air here]

10 Amps * 5000 Ohms = 50000 Volts to fire the fuel.

10 amps * 200 ohms[natural resistance of wires...etc] = 2000 volts to fire the fuel???

That is disastrously low voltage. The engine will never rev up.
Alan had the old plugs and caps in the sled's travel bag.* I re-installed them and WHAMMO.....8250.** "Yeah baby, Just like Downtown!"



May not be your problem, but I figured I would ask you to check spark plug assembly and explain "why" it is not such a lame suggestion.

Oh and anudder ting!...If you been using Aluminum tipped spark plug caps, check plug tip to see for wear. If worn even a little bit to take shiny surface off; Ditch the plugs and buy #1 plugs with solid top and now change plug caps.
I also like to put a small ty-rap around the spark plug cap to make the cap be fastened very tightly to plug.

Interesting Joe, I didn't mention one cylinder lost a plug while I was messing around. After I removed the "smatr valves" only one cylinder. I didn't have another br9eya but I did have a br9es. Thats when I got the 8200, after it cleared its throat. Berrlly Interlesting.


Matt Gilbert

Thanks JOE, I changed my wires and caps also plugs. Seemed to help. I also went with the heavier weights. I ran good this weekend. The next issue I have is getting enough heat in the pipe without overheating the motor. Being as the ECU is still stock it hard to do. I am running very strong though.

Matt Gilbert

run sled for 15-20 seconds in the pits with your cooldown cart connected before you dolly sled up to the line ? ? ?

That's what I see most of the top guns doing.