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Author Topic:   Building HELP!
41j
Dirt Roller

Total posts: 17
posted February 03, 2005 10:04 AM  
I am building a IMCA HOBBY (85 montie carlo)car this year. This is the first car that I have built. I have the cage bought from SCS Racing. Where is the best place for the fuel cell-in the middle of the trunk- or to the left side more?? Also the battery?? Where should I put that?

The track that I am going to run is 1/2 mile with pretty high banks. It is also a track that will go dry slick by the end of the night.

What is the best way for this car to scale out? What sould I be running for percentiges?

[This message has been edited by 41j (edited February 03, 2005).]

thebomb
Dirt Maniac

Total posts: 149
posted February 03, 2005 12:56 PM  
im sure youll get verying answers on this, however we have allways mounted it to the left, as high up as we can get it, has allways worked well for us,

dirty58
Dirt Maniac

Total posts: 115
posted February 03, 2005 03:53 PM  
not sure on scaling but build slides on your cell that way you can adjust it for what works. battery I mount mine over the left rear shock mount works good for me

racer17j
Dirt Forum Champ
Total posts: 5390
posted February 03, 2005 06:34 PM  
What about height? How high do you mount your fuel cell? I've seen guys that drop it through the trunk where the top of the fuel cell is level with the frame. Which way is better? On the trunk pan or through the pan?

[This message has been edited by crc1124 (edited February 03, 2005).]

thebomb
Dirt Maniac

Total posts: 149
posted February 03, 2005 10:56 PM  
the way i understand it, is on dirt you want it as high as posible to aid in roll over, pavement i understand that you want all weight in the car as low as possible, also on pavement, if its to hi i hear it will up set the car,

kevinwardracing
Dirt Full Roller

Total posts: 35
posted February 03, 2005 11:40 PM  
Had to jump in this one for a couple of reasons; I setup for a very fast metric chassis that runs at an extremely competitive ˝ high banked track and the car scales out at 48 - 49 % rear. That shocks a lot of people at the track.

Why do we though? I follow the rule that says you keep ballast in-between the axles. Two cars with the same equipment: the car with the lowest polar-moment of inertia (weight toward center) is fastest. I’ve preached it. Still I see tons of (successful even) grand nationals and mods that do not understand the concept. Still, just last week Mike Loescher, FinishLine Racing School Chief Instructor, joined Speed channels “Two Guys Garage” team to set up an IMCA Modified. During that program, Mike explained that the mod’s 56% rear weight was too much because of all the weight hanging out past the rear axles. He explained that the weight needed to go in-between the axles. Now he never did say where his final rear % was, but I have no doubt that it would surprise a lot of serious racers out there.

Also, another rule is to run ballast high and to the right for a dry slick track. I don’t mess with it though. What I do is keep my fuel cell to the right. Scaling the car tells me that if you keep the fuel cell on the left, you lose .2% cross (RF – LR) by the end of the night. Leaving the cell in the center has no effect on cross. Moving it to the right will add .2% cross to the chassis. Which is right?! Other factors play into the equation as well, so I can’t answer that. I can only say where I ran it last year. Why? Because I went with the idea that you need to tighten the car as the track loosens. Not being able to do anything to the car once in goes onto the track, I let the natural cross gain from a right side fuel cell mount do what I thought was needed. Also note that moving the fuel cell to the right will change the left %’s by a few fractions as well. We’re about 53.7 – 54 % over there.

Our battery is over the LR shock as well.

As for cross, with low rear % like the metric chassis has I'd suggest you try 48.5% - 50.5%. But if that's not working, then go with the same as the left side. I use Bob Bolles chassis R&D program, and it would suggest 48.5% for us, but as his book (Stock Car Setup Secrets) suggest that there are two ranges that may make the car neutral in handling and the latter being the same as the left side %...which is what our car actually likes best. I believe the difference is driver preference. For me, my driver likes to hit the corner harder than anyone and drives the corner harder than anyone...so he works best with the higher cross weight. The lower cross weight does allow your stagger to be off a bit more than the higher cross numbers, which is why I suggest you start there.

Good luck, 41j


[This message has been edited by kevinwardracing (edited February 03, 2005).]

41j
Dirt Roller

Total posts: 17
posted February 04, 2005 08:04 AM  
so what I have found out from what is said is that I should mount my battery on the lfet side right by the shock mount.

So about the fuel cell...would if be safe to say that it should go on the right side? Where at, should you put it as close to the axel as you can get it? Or should you put it towards the rr corner of the car? I am thinking that it should go by the axel? What do you all think?

Like I said, I am very new to all this, any and all help is great fully needed..thanks.

kevinwardracing
Dirt Full Roller

Total posts: 35
posted February 04, 2005 12:22 PM  
We didn't mess with the over the axle rule with the fuel cell. We just put it in the stock location and had at it. We did put it on rails that allows us to move it 6" right or left of center depending on what we wanted. Do I now believe the extra work was worth the fractions you get cross % wise?! The knowledge was worth it... Would I put it over the axles if I had to do it all over?! It's such a high spot...it'd have an effect on center of gravity...but the theory of polar moment of inertia is hard to deny. It's a good question...I think I'll email a few people on the subject. Note this -- I don't see it there very often, but I like the idea.

I'll let you know what I find out.

k

41j
Dirt Roller

Total posts: 17
posted February 05, 2005 07:03 AM  
kevin,,,just looking to see what you have found out?

Thanks...J

racer17j
Dirt Forum Champ
Total posts: 5390
posted February 05, 2005 09:50 AM  
There you go again 17j..making sense! I saw that show (last few minutes anyway) and I wondered about who in the heck it was setting that ride up! I have raced on both asphalt and dirt and "they are different animals" is an understatement! Ask any asphalt driver how to promote sidebite and he'll look at you like you are from Mars.

41j
Dirt Roller

Total posts: 17
posted February 10, 2005 01:52 PM  
just looking to see if anybody else has any ideas on how to do this or even what they are running know? Thanks for all the help

kevinwardracing
Dirt Full Roller

Total posts: 35
posted February 15, 2005 02:09 AM  
I got an email back from Mike Loescher, he told me he would put the fuel cell above the axle on a dirt car that ran in mostly dry-slick conditions. He said this would not be good for an asphalt car, as the low center of gravity is more important in that case.

Also, if you heard correctly during the show -- "it's important that all fluids be in the car (including fuel) before you scale."

I do agree that Shyrock is the man when it comes to modified. I also believe that he runs his car more like an asphalt car than any mod driver I’ve ever seen. You never see his LF raise more than an inch (if that) when he turns a corner. The guy is just awesome. I don’t know his thoughts about rear% but I don’t doubt your word. I will ask him (if given the chance) in a few weeks (March 18 & 19) at Thunder Hill Speedway outside of Topeka, KS when the USMTS shows up for a spring fling. We talked once before and he was really cool and openly informative. Also, I did note that on night he was running no rear ballast -- however, it was a black (rubber covered) track. It looked like asphalt by the end of a two day mod and late-model special.

[This message has been edited by kevinwardracing (edited February 15, 2005).]

racin78p
Dirt Freak

Total posts: 333
posted February 15, 2005 12:30 PM  
I will not agree with anyone that you need to put more weight on the right side and have your ballast HIGH for a DRY SLICK TRACK. Tried all the variations you possibly can for dry slick, and the only way I could get any improvement in hooking up in the corners was to equalize the weight to all four corners, especially the left rear (getting more bite out of it).

Here is the deal. On a tacky track, getting the right side to DIG into the track gets you more traction and away you go. On a dry slick you try that and away you go into the WALL or infield. You have to equalize your tire tread contact and weight to that tire(s) because (duhh) you are NOT DIGGING INTO THE TRACK SURFACE!!! You are gliding on slick dirt, like ice, maybe? Anyone driven on ice before? Same principle, people. This may be news to some of you, but I doubt it. Around here when we start off the evening (with a wet slick mess of a track) we have our rear stagger (right rear about 1" more than the left rear with the right front having the MOST or tallest stagger) and after the heats and B's, when the track gets very dry slick a simple trick to get the car to hook up on "ice" is to do a reverse stagger. Simply switch the right and left rear wheels/tires to the other side. IT WORKS!!! This is simple "ain't got much to change but I will do this" stuff, especially when your track rules keep you very limited in what you can change. Okay, now that I have vented, here's the deal about dry slick. Having your ballast high can make the car roll over quicker, and more. Especially more. That is not good for dry slick. Period. Think about it. Lower, less body roll, tire tracking becomes more equal, more traction, more speed through the corners, faster lap times. As Rome says, I'm out. Race on.

------------------
racin78p
if it ain't fun, then don't run

kevinwardracing
Dirt Full Roller

Total posts: 35
posted February 15, 2005 02:54 PM  
I agree. I was just passing along the information.

Ego Racing
Dirt Forum Champ
Total posts: 724
posted February 16, 2005 08:18 AM  
Kevin I agree 210% We found on our late model and mods that mounting the fuel cell to the right allows the car to gain wedge as the fuel burn off, so as the track gets dry the car is trying to tighten the chassis. Also we mounted it as close a possable to the rearend. If we needed moer rear % we would add lead over the rear, not past the centerline of the rearend. We would have to add more than if it were farther back but it did not act like pendulem when we put the car into the corner. We found through testing that our setup was about 130lbs above minum weight and was faster and easier to drive than a minimum weight setup with the weight mounted farther back. Shocks/springs and everything else stayed the same.
One last thing is if the weight is farther past the shocks and springs the shocks will need to be stiffer to control it. If you hold a bowling ball on your hand and move it you can control it's movements. If you hold it at arms length and move it you have a harder time controling it. A lighter ball is still harder to control at arms length than a heavy ball closer to you. This the same as weight mounted to your car.

AtomicPunk
Dirt Maniac

Total posts: 130
posted February 16, 2005 08:47 AM  
We run a fast metric also. Somehting else to ponder: Our track is dry-slick berore the mains even start. Our car scales out at 50.5% rear and 49% cross. Battery is over the lr and fuel cell is mounted at trunk floor level in the middle. You want your car to be as light as possible, of course, but if you can't hang lead to gain the percents you need-take more off the front. Cut as much as you can, use the tubing allowed up front and the least amount of it possible. Another thing to think about whether its lead or a battery (try this on the scales if you don't believe me), 50# beside the drivers seat is 50#, that same weight stting on the rear bumper weighs 52#. Hope this helps some.

Xtreme12x
Dirt Forum Champ
Total posts: 874
posted February 16, 2005 08:56 AM  
I'll tell you right now there's nothing "Asphalt" about a Shryock Chassis. He doesn't get up on three wheels like a lot of the other guys but he still gets it up there. You have to realize that asphalt and dirt have 2 different characters as far as grip and so fourth, so mixing the two still won't work. We've run a Shryock Car for the past year and I can tell you it's about as old school as it gets. Kelly keeps it simple and doesn't have you adjust your bar angles a thousand degree's at a time. The car to me seems more like a 2 link on steriods.

As far as mounting weight, I don't care what anyone says, you need it behind the axle to gain your foreward bite and rear percent. In order to get 60 rear percent on a modified you can't just plop lead right over the axle, you'll have to add way too much. The Bowling ball theory is true, but you aren't going to add that much actual weight to the springs. In a hobby stock 51-52 percent rear is sufficient, a little more is even better.

On a tacky track you don't want the right side to be biting. Why do we move our rearend to the right with wheel offsets when it is tacky?? The track provides the grip that we need, and we have to take the grip out of our cars. When it goes dry you really want both the right front and right rear to get you your grip while your left rear is your pivot point, then once the car is turned you want both rear tires to help get the car going forweard while the right front tire keeps the car turning. If you don't have enough rear percent, your going to start spinning tires sooner and get passed.
Now to get that sidebite, how do we do that? The typical left side weight percentage should be in the ballpark of 51.5-54 with the driver in the car. The faster and more grip the track provides, the more left.

Now throw all this out of the equation when the track goes rubber down. Now you want to keep the car straight and free just like on asphalt. Thats where you need to start making sure your weights are positioned just right, but on the normal Saturday night dirt track, no need to worry...

imcaracer84
Dirt Full Roller

Total posts: 33
posted February 16, 2005 09:29 AM  
Don't forget about rear percentage and momentum out of the corners. I'd use a lot less rear % on a 1/2 mile high bank than a stop and go tight cornered track.

    

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