Dyno reading

jc57

Member
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I'm trying to figure out gearing for our super stock class. Which is predator 212 with governor removed, billet flywheel, and 22lb springs. We race a 1/10 mile with hairpin turns. I do not know what my rpm drop is. Where should I be looking for rpm out of the corner and max rpm? Do I want to be out of the corner closer to peak horsepower or peak torque? Any info helps. Thanks.
 

Skidude

Member
I’d say if you go over 6000 drop a tooth off the axle sprocket and see if you’re faster or slower. If slower, add it back plus another and check your time. If faster, drop another one and recheck. That should get you started.
 

jc57

Member
I’d say if you go over 6000 drop a tooth off the axle sprocket and see if you’re faster or slower. If slower, add it back plus another and check your time. If faster, drop another one and recheck. That should get you started.
Great thank you. right now my biggest struggle is my tach. im waiting on an alfano 6 which will be a great help. but now i am using a cheap max rpm only tach.
 
Your new tach will help tremendously.
I'd aim for 1000+ rpm above peak HP depending on how much rpm loss you are seeing in the corners (it's probably more than 1000 rpm on a tight paperclip 1/10 mile track.) I suspect your best lap times will occur by turning the engine 67-6800 without looking at the actual numbers from your graph. For sure you want to keep the engine in the meat of the power curve at all times. The best "average" CHP under the curve is better than gearing to "peak" CHP. Next, do you, (or are you allowed,) have a billet rod? It looks like you'll be needing one.


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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 

jc57

Member
Your new tach will help tremendously.
I'd aim for 1000+ rpm above peak HP depending on how much rpm loss you are seeing in the corners (it's probably more than 1000 rpm on a tight paperclip 1/10 mile track.) I suspect your best lap times will occur by turning the engine 67-6800 without looking at the actual numbers from your graph. For sure you want to keep the engine in the meat of the power curve at all times. The best "average" CHP under the curve is better than gearing to "peak" CHP. Next, do you, (or are you allowed,) have a billet rod? It looks like you'll be needing one.


-----
🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
32 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
no billet rods in this class. that was another concern of not wanting to turn it too hard if i dont have to.
 

flattop1

Dawg 89
It made it too 6500 on the dyno once , at least .
I agree with Sundog , gear for 6000 see how it preforms .
You won't know how many rpm is too many till it Pops .
 

kmoody6

Member
I've seen several "OTB" Predators with the governor still hooked up deliver a lot more TQ and HP with almost no curve than what you have posted.

I'd say you are going to be left off the corners pretty bad.

The Dyno graph on RaceStudio3 matched what I saw on the dyno for the engines we ran.
 

"J'-remy

Member
look at your rpm drop on your tach. you want your hp peak at the start of your drop and a few hundred past (whatever your drop is) at the end of the strait. you want to have maximum pull from the apex of the corner and should be falling off the peak at the end of the strait. that's how you gear a single ratio race car/kart/motorcycle for speedway
 

"J'-remy

Member
in other words keep in in that hump of the curve
I've seen several "OTB" Predators with the governor still hooked up deliver a lot more TQ and HP with almost no curve than what you have posted.

I'd say you are going to be left off the corners pretty bad.

The Dyno graph on RaceStudio3 matched what I saw on the dyno for the engines we ran.
I have dynode several OTB predators and am finding it hard to believe this motor docent have a cam. 22lb springs would be overkill for a stock cam and all the predators I have ever seen make their peak power around 4000. rpm. and the dyno operator has done a fair bit more. if you have an honest legal OTB predator that makes that power on my friends dyno I'll give you triple what harbor freight asks for.
 

kmoody6

Member
Ours does come out of the box, but the tape and staples have been cut and removed by the time it gets to us. I will say that all of the NC OTB predators have great cams in them after the initial dyno run.

The "OTB" rules we have are- No tape on the side cover, have filter sock, no addition holes in the airbox, oil sensor maybe unhooked, 5500 RPM rule and must surge. Sometimes there is a max lift rule, sometimes a minimum lift rule in the DNQ series as- depends on how bad the race director wants his series sponsor to win that night.

Peak HP is right past the 5252 crossover, Peak TQ is whatever RPM that dyno run started at.

When it's time for a fresh one- we either claim one, or buy 5 new ones and tune the one that graphs the best- usually there is one that is astronomically better than the other 4- sometimes no.


Our RPM drop is normally 300-450, unless we are just on a off night on tires.
 

kmoody6

Member
To the original poster- sorry about the side conversation.

Do you have a way to tell your RPM out of the corner? Since that is what you seem to be asking.

By your graph, I would always try an keep the Min RPM above 5500 -5700, what ever produces the best lap times, and not care what the Max RPM is unless it's just crazy high. Clone rods are doing over 7k without issue.

What are you rules for Super Stock? I would just be using some used 18lb springs out of a clone unless you can go with a crazier cam.
 

"J'-remy

Member
ooooooh its a Carolina "OTB" which means the cam was twisted the crank gear was advanced, aftermarket 10.8 springs a reworked carburetor, jetted, 3 angle valve job, decked, honed rod and everything was reworked to look 'as cast' then broken in and tuned on a dyno. real stewards of the sport over in The Carolinas what's just as bad is the promoters and track owners let it happen.
 

kmoody6

Member
Nowhere near that much work.

Replace cam, springs, change the muffler to an original predator one. The other stuff doesn't help one bit with the air box/ surge rule.

But if the engine is a turd out of the original box, nothing you can do to help it.
 
ooooooh its a Carolina "OTB" which means the cam was twisted the crank gear was advanced, aftermarket 10.8 springs a reworked carburetor, jetted, 3 angle valve job, decked, honed rod and everything was reworked to look 'as cast' then broken in and tuned on a dyno. real stewards of the sport over in The Carolinas what's just as bad is the promoters and track owners let it happen.
Just going by the rules and the way they are enforcing them.
 
ooooooh its a Carolina "OTB" which means the cam was twisted the crank gear was advanced, aftermarket 10.8 springs a reworked carburetor, jetted, 3 angle valve job, decked, honed rod and everything was reworked to look 'as cast' then broken in and tuned on a dyno. real stewards of the sport over in The Carolinas what's just as bad is the promoters and track owners let it happen.
Should have never let it get to this but they did, the racers are just playing by the promoters rules.
 

"J'-remy

Member
around here the predator class was/is becoming the biggest class around. but you can hear a lot of new guys completely frustrated and ready to either get a clone or quit racing karts altogether . people don't like showing up ever week paying their entry and have the same group of 3 friends lap the field. this doesn't grow the sport, it shrinks it.
 
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