[Dirtboy]

So, my wife and I are just getting into doing a little amateur racing with our 15 A8 Hellcat. Nothing serious, just having fun. Was just looking for some insight to next mods, or direction we should take. Or if we just need to practice and get seat time for a bit. (Which is what I'm thinking). Currently have CAI, Metco 2.85, Kooks long tubes w/high flow cats, 180 T-stat, 18" MT ET street's, Demon injectors, engine and Trans tune, and I think that's it. On the list is, rear cradle lock, DSS drive shaft, and 3.09 gearbox. Should I just practice on driver mod now after I get the DSS and cradle lock? (Can add gearbox later). Any input is appreciated. Thanks. I even have the hellcat head vinyl stickers which gives like 10 more h.p.

 

[baabootoo]

One word; PRACTICE. You need to get to know your car as it is.

 

[Dirtboy]

Yup, that's kinda what I was thinking too. I figured the driver mod was what I really needed next. Definitely getting the drive shaft tho. Thanks for the reply.

 

[Himmelkat]

Demon stock driveshaft is the best.

 

[Himmelkat]

So, by racing you mean drag racing?

 

[Dirtboy]

Yes sir. Drag racing. Probably hard to get your hands on a demon drive shaft tho. Correct?

 

[Himmelkat]

I don't know how hard they are to get. Maybe they are the same part number as the Redeye or Super Stock items, and may be readily available. Check the online Mopar parts places.

Also, if you are drag racing, anything you can do to help the car rotate entirely onto its rear tires will help you launch. This means decreasing weight ahead of the center of gravity and below it, and increasing weight behind the center of gravity and above it, if just dealing with weight.

If you could remove a few hundred pounds up front, and put them in the form of lead sheets securely glued to the underside of the roof over the rear seat, the weight would have the most dramatic effect (given the stock envelope) that it could in helping shift the car's weight onto the rear tires on launch.

I am not advocating this, just commenting on the physics.

Also, raising the rear end or front and rear will help with this, as it will increase the height of the center of gravity, which is free weight transfer with no added weight, just some more drag.

When a car wheelies, it rotates its mass about the center of mass (gravity) first, then when it has exhausted all travel available by compressing rear springs and extending front ones, it then starts to pivot the entire car about the contact patch of the rear tires on the pavement.

You don't want the rear end to squat, PER SE. You want the rotation of the car and weight being transferred to the rear tires, which is shown by the springs compressing in the rear. Lowering a drag car does nothing to assist it in weight transfer, though it may look cool. Top fuelers are so low because they have to tune things to FIGHT doing wheelies. It's one reason they subtracted some frame members in their traditional design, to allow the rear part of the car to rotate a bit, while the front end still droops and stays in contact with the pavement. They have so much power, they can wheelie at will. What they are aiming for is maximum weight transfer while still having some shred of steering contact with the track.

Pro Stockers can also wheelie regardless, so they tune the launch to just skim the asphalt with the front tires, which is an ideal launch, according to Bob Glidden, the winningest Pro Stock driver in history.

This is stuff you won't find in "textbooks," but it is physics, and it is undeniable. Gassers looked like this

and Altered cars had an altered wheelbase:

Notice rear wheels moved substantially forward from stock.

This was done to make the right triangle between the center of gravity and the rear contact patch and the ground to be as steep as possible, which made it easier to transfer weight to the rear tires, because, as one guy said from back then, the tires were skinny and terrible for traction, so they had to use all means available to put more weight on them.

Now, for road racing, you want quite the opposite. You want about 60 percent rear, 40 percent front weight distribution, STATIC. Then you want the cg as low as you can get it so all four tires get to maximize their traction, as very little weight shift occurs at any time.

 

[Dirtboy]

Will do. Thanks again. I appreciate it. I'd love to do some swapping with someone on a diablosport trinity 2 and unlocked pcm for a 6.4/5.7 on a driveshaft, but I haven't made it to my 40 posts yet to list it in buy/sell/trade.

 

[burbigo]

Hey, thanks for all these details but where can we find these heels?

TweakBox Tutuapp

 

[Hossfly]

They are the same as Redeye. I have one boxed up and ready to go with bolts and carrier. Come from my 19 Redeye. Has 15 k miles on it.
400.00 plus shipping

 

[Dirtboy]

I don't know how hard they are to get. Maybe they are the same part number as the Redeye or Super Stock items, and may be readily available. Check the online Mopar parts places.

Also, if you are drag racing, anything you can do to help the car rotate entirely onto its rear tires will help you launch. This means decreasing weight ahead of the center of gravity and below it, and increasing weight behind the center of gravity and above it, if just dealing with weight.

If you could remove a few hundred pounds up front, and put them in the form of lead sheets securely glued to the underside of the roof over the rear seat, the weight would have the most dramatic effect (given the stock envelope) that it could in helping shift the car's weight onto the rear tires on launch.

I am not advocating this, just commenting on the physics.

Also, raising the rear end or front and rear will help with this, as it will increase the height of the center of gravity, which is free weight transfer with no added weight, just some more drag.

When a car wheelies, it rotates its mass about the center of mass (gravity) first, then when it has exhausted all travel available by compressing rear springs and extending front ones, it then starts to pivot the entire car about the contact patch of the rear tires on the pavement.

You don't want the rear end to squat, PER SE. You want the rotation of the car and weight being transferred to the rear tires, which is shown by the springs compressing in the rear. Lowering a drag car does nothing to assist it in weight transfer, though it may look cool. Top fuelers are so low because they have to tune things to FIGHT doing wheelies. It's one reason they subtracted some frame members in their traditional design, to allow the rear part of the car to rotate a bit, while the front end still droops and stays in contact with the pavement. They have so much power, they can wheelie at will. What they are aiming for is maximum weight transfer while still having some shred of steering contact with the track.

Pro Stockers can also wheelie regardless, so they tune the launch to just skim the asphalt with the front tires, which is an ideal launch, according to Bob Glidden, the winningest Pro Stock driver in history.

This is stuff you won't find in "textbooks," but it is physics, and it is undeniable. Gassers looked like this
View attachment 584331
and Altered cars had an altered wheelbase:
View attachment 584332
Notice rear wheels moved substantially forward from stock.

This was done to make the right triangle between the center of gravity and the rear contact patch and the ground to be as steep as possible, which made it easier to transfer weight to the rear tires, because, as one guy said from back then, the tires were skinny and terrible for traction, so they had to use all means available to put more weight on them.

Now, for road racing, you want quite the opposite. You want about 60 percent rear, 40 percent front weight distribution, STATIC. Then you want the cg as low as you can get it so all four tires get to maximize their traction, as very little weight shift occurs at any time.

That is a well informed write up. Makes sense. Very good information there. What are your thoughts on drag springs? Or demon/super stock springs? Would this help any with putting power to the wheels? It's just a fun street car that my wife and I take to the strip occasionally. I Definitely don't want the car lowered anymore tho. Especially since the kooks hang down quite a bit.

 

[Dirtboy]

They are the same as Redeye. I have one boxed up and ready to go with bolts and carrier. Come from my 19 Redeye. Has 15 k miles on it.
400.00 plus shipping

So what is the difference in the Redeye/ Demon shaft vs. Hellcat shaft? I've just been looking at the DSS shafts.

 

[Dirtboy]

They are the same as Redeye. I have one boxed up and ready to go with bolts and carrier. Come from my 19 Redeye. Has 15 k miles on it.
400.00 plus shipping

I sent you a PM. Thanks again

 

[Hossfly]

Dirtboy
when you get your post in I may have some interest
pm me when your legal if interested in the ds.

 

[Dirtboy]

Dirtboy
when you get your post in I may have some interest
pm me when your legal if interested in the ds.

Good deal. Thanks again. I appreciate it sir.

 

[Himmelkat]

That is a well informed write up. Makes sense. Very good information there. What are your thoughts on drag springs? Or demon/super stock springs? Would this help any with putting power to the wheels? It's just a fun street car that my wife and I take to the strip occasionally. I Definitely don't want the car lowered anymore tho. Especially since the kooks hang down quite a bit.

The lower your car is, the less weight transfer to rear wheels when launching, and the less weight transfer in any maneuver at all, for that matter, even with the same spring rate.

Drag springs on the front are taller, softer springs designed to fling the front end of the car up, thus raising the cg, and assisting in transferring weight to the rear wheels due to acceleration. They squash down to normal height when installed, but they really wanna throw up that front end on acceleration, the goal being raise cg, make right triangle between cg and rear contact patch have vectors that allow all weight to end up on rear tires, and thus enable harder launches.

If you like a rough ride, hard springs of the same ultimate ride height as you have now will make it feel sharper in cornering and braking, but provide less "front end jump" on acceleration, but the they will allow less rear and squat on acceleration, too.

The harder your springs, the less your shocks will have to work, as the springs will be doing some of the work for them.

It depends on what you want.

If you rake the car from front to rear, you get better downforce overall, better engine bay air removal, less drag, and more than half the lowered cg reduction of lowering the entire car the same amount, as more than half the weight is over the front wheels.

But, many do not like the raked look. However, it gives better ground clearance for anything behind the front wheels than the fully-lowered look, and less ground clearance for anything in front.

A) Short answer: hardest springs you can tolerate for road racing and cornering, that will drop the car as low as you can get away with while only scraping your skid plates on rare occasions, which plates are installed specifically for protecting the underside from scraping. The only way you can know you have a low enough car on the track is if it scrapes once in a while. If it never scrapes, you are not low enough. F1 cars use them.

B) for normal Hellcat driving, stock springs are perfect.

C) For the drags, front springs that boing the front end up as high as possible, hard rear springs to keep cg high, I would think.

What matters most to you?

 

[Himmelkat]

I sent you a PM. Thanks again

That's a frikking bargain.

 

[Dirtboy]

The lower your car is, the less weight transfer to rear wheels when launching, and the less weight transfer in any maneuver at all, for that matter, even with the same spring rate.

Drag springs on the front are taller, softer springs designed to fling the front end of the car up, thus raising the cg, and assisting in transferring weight to the rear wheels due to acceleration. They squash down to normal height when installed, but they really wanna throw up that front end on acceleration, the goal being raise cg, make right triangle between cg and rear contact patch have vectors that allow all weight to end up on rear tires, and thus enable harder launches.

If you like a rough ride, hard springs of the same ultimate ride height as you have now will make it feel sharper in cornering and braking, but provide less "front end jump" on acceleration, but the they will allow less rear and squat on acceleration, too.

The harder your springs, the less your shocks will have to work, as the springs will be doing some of the work for them.

It depends on what you want.

If you rake the car from front to rear, you get better downforce overall, better engine bay air removal, less drag, and more than half the lowered cg reduction of lowering the entire car the same amount, as more than half the weight is over the front wheels.

But, many do not like the raked look. However, it gives better ground clearance for anything behind the front wheels than the fully-lowered look, and less ground clearance for anything in front.

A) Short answer: hardest springs you can tolerate for road racing and cornering, that will drop the car as low as you can get away with while only scraping your skid plates on rare occasions, which plates are installed specifically for protecting the underside from scraping. The only way you can know you have a low enough car on the track is if it scrapes once in a while. If it never scrapes, you are not low enough. F1 cars use them.

B) for normal Hellcat driving, stock springs are perfect.

C) For the drags, front springs that boing the front end up as high as possible, hard rear springs to keep cg high, I would think.

What matters most to you?

Wow! Thank you for all the information, insight, experience, and your time posting. I truly appreciate that. There is alot of things that people don't think about like CG and the triangle. (Least newbies like me). The car is 98 percent daily and 2 percent track/street racing. So yes, it sounds like I'll just be sticking to the stock springs. I was just seeing if there was some kind of happy medium spring out there that kinda doubled as a daily driver /stock spring, but gave some extra benefits for amateur drag racing. I was trying to dig up some info on the springs that HHP has as they seemed to be close to that happy medium I was searching for. Seemed like, anyways.

 

[Dirtboy]

That's a frikking bargain.

I agree. I would buy it today if I had my 40 posts in. For the power I'm running I think the Redeye shaft would be just fine.

 

[Himmelkat]

Wow! Thank you for all the information, insight, experience, and your time posting. I truly appreciate that. There is alot of things that people don't think about like CG and the triangle. (Least newbies like me). The car is 98 percent daily and 2 percent track/street racing. So yes, it sounds like I'll just be sticking to the stock springs. I was just seeing if there was some kind of happy medium spring out there that kinda doubled as a daily driver /stock spring, but gave some extra benefits for amateur drag racing. I was trying to dig up some info on the springs that HHP has as they seemed to be close to that happy medium I was searching for. Seemed like, anyways.

Another point few on Earth have ever thought about:
Supposing the balance of vectors at launch puts the center of gravity directly in line with the thrust vector sum to the rear tire patch, the car will not stay static in its stance, but wheelie because in addition to the thrust vectors from gravity and forward acceleration, the rear axle is also being twisted with about 7-8 times the torque that is exiting the engine due to transmission and rear end multiplication, so if the car has 700 ft-lbs aggregate torque at launch, that is around 5000 ft-lbs of torque exercised on the entire car pivoting on the rear axle center lines.

5000 ft-lbs is not much, but it is part of the equation that results in a wheelie, because if the car is trying to turn its wheels forward, the torque is trying to flip the car over backwards, so at, say, ten feet from the rear axle is around 500 pounds of additional lift on the front axle.

If rails were to accelerate with all 10,000 hp and their front end was locked down from lifting, they might produce so much g that the driver would pass out.