Visit The Dirt Forum for More Information

Author Topic:   killing horse power on dry slick track.
juni
Dirt Maniac

Total posts: 184
posted March 21, 2005 03:36 PM  
We have a a mod best of everything car is a rocket on tacky and heavy track but when the track goes black cannot hook it up have tried different chassis set ups does not help . I am wondering if we use our big carb for heats and time trials and go to smaller carb for feature race any one else trying this ?

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 21, 2005 03:50 PM  
The smaller carb(depending on how small) will actually make it tougher to drive on the slick. It will help the midrange and make the throttle more responsive, the opposite of what you want on slick. The bigger carb will kill some midrange and softern the torque a little and move the HP up in the range.

Also larger headers will soften the midrange and move the torque up in the rpms where it is easier to control on the track. Same thing can be done with gear, more gear and you can move the rpms up out of the power range for the motor and make it easier to hook up, plus if the tires break loose they will come back under the car quicker.

Try lowering the throttle linkage on the pedal. This will slow the reaction down and give the driver more time to ease into it instead of getting into it and blowing the tires off. Throttle/driver input plays a large role in hooking the car up on dryslick.

Lastly you can pull a couple degrees out of the timing but i would use this last. Id concentrate on the other stuff first.

juni
Dirt Maniac

Total posts: 184
posted March 21, 2005 09:21 PM  
How about a restictor plate ?

fastow
Dirt Maniac

Total posts: 168
posted March 21, 2005 10:05 PM  
I have toyed with the idea of just adding a stiffer spring for the feature.

ruggs66
Dirt Maniac

Total posts: 193
posted March 21, 2005 11:02 PM  
How about trying a Vac. Secondary Carb for the feature?

you can adjust it as to how fast the secondarys open.

just an idea....


krace72
Dirt Roller

Total posts: 16
posted March 22, 2005 11:55 AM  
If you go to the December 2004 circle track article of 2004 there is a article called poor mans traction control.By using a crank trigger and a regular distributor with a switch between the two if legal you can switch back and forth.It says you set the crank trigger at optimum performance and set the distributor 4 degrees retard.When track goes black switch to distributor and it will lose approximately lose 5% of power which is just enough to tone down the motor and control wheel spin.I put one on my latemodel over the winter but have not run it on a track to see how good it works.The article is written by Clements Racing Engines.The only thing the article does not tell you is you have to buy spacers for the water pump because the crank trigger wheel is 5/16th or so thick I bought them from CV Products for $10.00 Each.It was very simple to put on I just hope it works like the article says.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 22, 2005 12:48 PM  
you can also buy a timing retard control and adjust the timing with a small knob if you wanted to. Set your timing like normal then dial back as necessary for track conditions. I think most mod rules wont allow it though, just like the swithcing between crank trigger and dist.

mekomod51
Dirt Full Roller

Total posts: 42
posted March 22, 2005 02:39 PM  
In the past we have run a different gear and this helped, for example if we know the track is really fry come feature time, and we normally run a 5:67 or 543, we have switched to a 514 and this killed th elow end and helped the car hook up on a dry track.

Racer111
Dirt Freak

Total posts: 259
posted March 22, 2005 05:35 PM  
What kind of a car brand ?Whats the rear suspension and what do you do to it.

racerwilson
Dirt Freak

Total posts: 357
posted March 23, 2005 07:53 AM  
Cut down on the size of your air filter. For dry/slick we drop down from a 6" x 11" to a 2" x 11" that works well when the track gets slick by feature time. We also use Willey's carb slide spacer plate works awsome when feature starts out tacky then goes slick. We won 10 A main features with that set up last year each race track started out heavy then turned slick.

Kromulous
Dirt Forum Champ
Total posts: 796
posted March 24, 2005 06:23 AM  
TRaction control retards timing, to take away power. Seems to me retarding the timing would be the first thing to go to.

Feature time, set the timing to about 25 to 27 degrees and roll with it. Less timing isnt going to hurt the motor, but it may change the jetting requirements in the carb. I'm not to sure about that one, gonna check with the engine builder.

The lower gear theory works well to.

outlawstock17
Dirt Forum Champ
Total posts: 1363
posted March 24, 2005 09:30 AM  
traction control BRIEFLY retards the timing. i wouldn't recommend running an entire race with the timing locked severely retarded. you could burn up the exhaust system and anything close to it.

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 24, 2005 09:36 AM  
To go along with outlawstocks post TC only would retard it breifly when it was needed. You back your timing down 10 degrees and its that way through the whole race. What if the track changes and you need the extra timing then your screwed? A few degrees might be fine but i would not back it off 10+ thats for sure.

Also on the gear thing, I'd be careful going down in gear numbers to get rid of torque, Going from a 5.67 to a 5.14 will drop the rpms considerably and maybe to the point that you start lugging the motor, which is extremely hard on the motor. IT may be easier to hook up but keep in mind whats its doing to the rest of the engine.

Kromulous
Dirt Forum Champ
Total posts: 796
posted March 24, 2005 09:36 AM  
Retarding the timing from 32* to 27* or so, does that qualify as severly retarding?


dirtbuster
Dirt Forum Champ
Total posts: 2007
posted March 24, 2005 10:23 AM  
I wouldnt go more than 2 degrees but thats my opinion.

outlawstock17
Dirt Forum Champ
Total posts: 1363
posted March 24, 2005 11:23 AM  
5 degrees from optimum is quite a bit.

i've considered trying an MSD 2 step rev limiter like drag racers use. in the high limiter i would use a max rpm chip(7500 for example) to protect from over revving and in the "launch" part of the limiter i would use a max corner speed chip(5500-6000 for example). i'd put the button on the steering wheel and press it when i backed off to enter the corner and hold the button down until the car was back on the straightaway. this would limit the rpms in the corner to whatever chip you had in the "launch" part of the limiter regardless of how far you had your foot in it. you could also bump the the button in the corners if the car started getting loose or get off the button if the car felt hooked.

you'd have to play with different chips to figure out which one worked best but if one particular chip didn't work right you could drive the car normally without using the button. i never actually tried this, but i think there may be something in it.

i'm not sure if it would be considered illegal or not...

[This message has been edited by outlawstock17 (edited March 24, 2005).]

droper23
Dirt Freak

Total posts: 233
posted March 24, 2005 04:12 PM  
We like to use the cheap method. FOOT CONTROL. Press the gas pedal like there is an egg under it. When the track here turns dry, I am only at WOT for a split second around the flag stand. A lot of times when the track dries, people still want to drive like it is wet, and you will do nothing but burn tires that way.

jercer2004
Dirt Roller

Total posts: 12
posted March 25, 2005 09:06 PM  
A throttle sponge won't hurt anything either , just a thought, we run one.

juni
Dirt Maniac

Total posts: 184
posted March 26, 2005 10:24 AM  
Where do they grow these at ? Maybe on the bottom of a pond in south.

jercer2004
Dirt Roller

Total posts: 12
posted March 27, 2005 06:03 PM  
juni, lol, it's a spring that is in your throttle linkage deadens the response of the carb. We bought ours at Close Racing Supply in Elbridge.PA

juni
Dirt Maniac

Total posts: 184
posted March 28, 2005 08:03 AM  
LOL..... I learned somthing new I will check them out thanks .

jercer2004
Dirt Roller

Total posts: 12
posted March 31, 2005 05:49 AM  
Yes we do. KP if your out there i'm sure you know what they are (throttle sponge) . I think i explained it right.....Thanks

goinrcn44h
Dirt Freak

Total posts: 205
posted March 31, 2005 07:12 PM  
taking gear away in my opinion is making the problems worse. like someone said the 5.67 to 5.14. I would do the exact opposite. slick means corner speeds are slower, takin gear away will lug it bad. then hit the torque all at once.. insta-spin.... goin the other way will keep the r's up and above the torque. plus its easier to catch the rpm on the top end than it is on the bottom end. plus the chassis is more free in the higher rpm area in my opinion.and transfers faster as well, this I know. but I always run throttle springs that hover on too stiff to way too stiff just for that reason also. and if its wet and heavy or rough you want stiffer springs so your foot dont bounce as bad. bounce the throttle in a sprint car a few times and see what happens.... lol
44H

mod15racing
Dirt Roller

Total posts: 12
posted April 04, 2005 09:42 PM  
Move the linkage up on the gas pedal this will slow the carb opening up. unhook the back half of the carb and run it on the front two this wont hurt a thing and will smooth it out. this work's for us also just apply the throtle smooth and easy and dont let it break loose

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 05, 2005 07:50 AM  
Actually you want to move the linkage down on the pedal, and/or up on the throttle arm.

I'd be careful running on only the front half of a 4 barrel. It wasnt designed for that and you risk leaning it out and burning something up.

mod15racing
Dirt Roller

Total posts: 12
posted April 06, 2005 12:38 PM  
If you move the linkage down on the pedal you will open the carb up faster, it dose not have to pull as far the lower you go down. Go to the top hole and it has to travel a longer distance so it is slower. if you dont think so next time you are on a dry slick track try it in the lowest hole and see what happens

outlawstock17
Dirt Forum Champ
Total posts: 1363
posted April 07, 2005 05:31 AM  
no mod15, you're thinking on the wrong side of the teeter totter...

your foot has to travel farther with the linkage in the lowest hole on the pedal.

i doubt this is the best answer to hooking up on a dry slick though. a sensitive foot will work in any of the holes...

[This message has been edited by outlawstock17 (edited April 07, 2005).]

dirtbuster
Dirt Forum Champ
Total posts: 2007
posted April 07, 2005 07:48 AM  
mod15racing,
just like outlawstock said, you want your foot to travel furthur not the linkage end. You have to move the linkage down on the pedal to acheive this. Think of it this way. IF you move the linkage to the top and it is 6" away from the pivot and the foot pad is 6" away then it is 1:1. 1" travel with your foot=1" travel at the linkage. Move the throttle linkage down to 3" and the ratio becomes 2:1. 2" travel on the pedal = 1" travel at the linkage. That means your foot has more distance to feather into it, without just blowing the throttle open.

goinrcn44h
Dirt Freak

Total posts: 205
posted April 07, 2005 01:17 PM  
If the guy can't figure out which setting the pedal moves further than the last, then maybe just maybe, he shouldn't be behind the wheel... just a guess. I wouldn't change the ratio anyway. I always want as much travel as possible, and I use 3 light springs that make it consistant throughout travel but stiff enough.
if tires spin.... roll out slightly or drag the brakes a little. how tough is that...?
44H

outlawstock17
Dirt Forum Champ
Total posts: 1363
posted April 07, 2005 05:57 PM  
lmao! that was harsh 44h!

dirtzone
Dirt Maniac

Total posts: 102
posted April 10, 2005 07:17 AM  
quote:
Originally posted by goinrcn44h:

if tires spin.... roll out slightly or drag the brakes a little. how tough is that...?
44H

Agreed! Just need to have patience on the slick stuff.

Back to the Archives