Air bags and power

[Kyle@FTP]

I have done a few searches and read through a lot of threads. But I cant seem to find good info on the subject.

What is the fastest someone has gone on an airbag?

I know everyone says it wont work. But a lot of people said we couldnt walk on the moon. I love trying to break the mold. Even if I fail, I always learn.

[Domer]

are you looking for track times or actual top speed? I have gone 151mph in my 77 C10, and that's bagged, body dropped, and making 608hp with a blown small block, th350 and 3.08 gears, with 275/35r20.

[Kyle@FTP]

I would like to see some 60ft times, 1/8th and 1/4 times. I know not a lot of guys run bags so this might be a dud thread. But it may lead to some good discussions.

Beautiful truck Domer.

[Domer]

I figured that was what you were looking for. Thanks for the compliment though. I am in the middle of a rebuild, working on going for an all around performer. Do decent at the track, and still be able to corner well and be comfortable to drive on the street...

[BR3W CITY]

Generally I see the bags used in the Pro Touring type cars, less so on drag-oriented vehicles.

If I had to guess why bags weren't being used as much, my guess would be that the consistency of an oil/gas shock would outdo an airbag which can change based on pressure (whether or not you want it to). They also don't like being landed on, were you to be able to pick the front end up.

[Kyle@FTP]

for argument sake if the suspension is designed to not wheel stand and separate instead of squat. why wouldnt it work?

[tinydb84]

From what I read the issue in the front is due to a lack of potential energy needed for the weight transfer. Super73 would probably be a good person to ask about this.

[low&slow]

You know i've been discussing this same exact topic to my buddy for about the last month or so. As my truck went from the idea of a drag truck only to a driver that sees the track every other weekend.

I think bags wouldn't really be ideal for drag racing just because of what's been mentioned about stored energy in the front, but how much "all of a sudden" weight can be put on bags when doing a hard launch for the rear?

[Kyle@FTP]

Low and slow, Its all depends on how the rear is set up. You can build separation into the rear suspension. Basically when you leave the axle drive into the ground and the body lifts slightly or stays neutral. so the bag wont see the load like a conventional set up.

When you stay potential or stored energy are you refering to how fast the front unloads at launch?

[low&slow]

potention or stored energy in the front springs that allow weight transfer when the vehicle launches. I don't think bags up front would have much of that to allow much weight transfer to the rear.

[Super73]

Kyle,

You are talking about anti-squat in the rear, when IC is at/above CG. The roundy round guys put massive amounts of anti-squat in their vehicle to slam the tire in to the ground. There are some tradeoffs with doing that.

It hits the tire very hard
More Anti-squat = More Anti-rise of the front end = Less weight x-fer

If you think about the roundy round guys, (they do lots of weird things) I can understand why it works for them. Their moment of inertia is much different than a drag car. The dirt cars are already rolling and the fast guys will ride the brakes applying power at the same time waiting for the flag to go green. This loads the suspension prior to acceleration. The term my dirt racing buddy uses is “on the bar” The tire does not see that initial hit that a drag car would. They still do have a lot of stored energy in the front allowing the front to rise, but the whole car planes up like a boat would in water at speed. My buddy tells me his gopro shows the rear spring literally extends fully then separates from the spring pocket 1-2”. They have to have a center locater to keep it in place.

A drag vehicle applies power completely different. For instance and NA setup would typically have the converter set to 200-400 rpm above peak TQ. The converter also multiplies the TQ until fully coupled. My truck makes >450ish ftlbs to the tire on motor at 5,700 rpm. Converters often multiply that by 2x. Think about the moment of inertia at the line. I am hitting the tire with +/- 900ftlbs while trying to move 3,200lbs. If I had 100% antisquat the rear theoretically would neither separate or squat. All of that load would translate directly in to the tire (provided the front end wasn’t rising). Without a big sidewall to help soften that hit, it is likely the tires will not hold the power.

I am just brushing the surface here.

IMO in order for the large anti-squat set up to work at a dragstrip, you would have to have a lot of stored energy in both the front and rear which your bags are not going to provide. Or.. You are going to have to have a BIG sidewall tire to absorb that hit on the line.

That is my two cents.

[Kyle@FTP]

Originally Posted by Super73

Kyle,

You are talking about anti-squat in the rear, when IC is at/above CG. The roundy round guys put massive amounts of anti-squat in their vehicle to slam the tire in to the ground. There are some tradeoffs with doing that.

It hits the tire very hard
More Anti-squat = More Anti-rise of the front end = Less weight x-fer

If you think about the roundy round guys, (they do lots of weird things) I can understand why it works for them. Their moment of inertia is much different than a drag car. The dirt cars are already rolling and the fast guys will ride the brakes applying power at the same time waiting for the flag to go green. This loads the suspension prior to acceleration. The term my dirt racing buddy uses is “on the bar” The tire does not see that initial hit that a drag car would. They still do have a lot of stored energy in the front allowing the front to rise, but the whole car planes up like a boat would in water at speed. My buddy tells me his gopro shows the rear spring literally extends fully then separates from the spring pocket 1-2”. They have to have a center locater to keep it in place.

A drag vehicle applies power completely different. For instance and NA setup would typically have the converter set to 200-400 rpm above peak TQ. The converter also multiplies the TQ until fully coupled. My truck makes >450ish ftlbs to the tire on motor at 5,700 rpm. Converters often multiply that by 2x. Think about the moment of inertia at the line. I am hitting the tire with +/- 900ftlbs while trying to move 3,200lbs. If I had 100% antisquat the rear theoretically would neither separate or squat. All of that load would translate directly in to the tire (provided the front end wasn’t rising). Without a big sidewall to help soften that hit, it is likely the tires will not hold the power.

I am just brushing the surface here.

IMO in order for the large anti-squat set up to work at a dragstrip, you would have to have a lot of stored energy in both the front and rear which your bags are not going to provide. Or.. You are going to have to have a BIG sidewall tire to absorb that hit on the line.

That is my two cents.

All very good points. With anti squat built in and lots of adjustments in the shock and playing with tire pressures I think the initial hit can be softened enough. In may hurt the 60ft and we may need to take some timing out at the hit but I feel all the bugs can be worked out.

Either way its going to be fun trying!

[slowcpe]

Good topic. I was looking for a thread on this very topic when debating on bags vs coilovers. May have made the wrong choice pretty sure my track days are close to over anyways as both our local tracks have closed. Would still like to maximize my setup though.

[Super73]

Some Honda's 60' 1.3x. So lots can be made to work. Doesn't mean easy.

[tinydb84]

You could do a turbo set up that leaves soft(er) and let the power come on later:

https://www.youtube.com/watch?v=OgGgShB1iHQ

[Kyle@FTP]

Fairmonts are so cool!!!!! haha

Engine is build. 752hp with plenty of gogo juice to run deep into the 9s.

Its just a theory right now. Start playing around with some solidworks and see what happens. Its always fun to bench race and try and learn.

[BR3W CITY]

What I'm wondering is if something like a modified air strut ( air can/cylinder) could work. We're talking just-for-sh!ts now, but at least in the rear, I wonder if it would work?

An air can doesn't have a flexible body, so the bellowing or any other "uncontrolled" transfer of energy would be limited more. Technically with an air can, you can limited the compression and return like a shock also.

*I don't even know if there is an air can small enough yet strong enough to even handle these forces. I just know they exist for other functions.

[moggey01]

Fastest I know of is a 7.70. It was an experimental Pro Stock truck. Todd Bevis built the truck for Raymond Martin. It used an air bag on top of the rear end as a stabilizer with coil overs. Rodger Brodgon bought the truck and never qualified with it. It had longer than normal 4 link bars . They thought this was worth a try because of the wheelbase. It was off from the conventional setup by over a tenth.. 60 ft was a 1.06-07,1/8 was 4.80s. 7.70s at 175 or so. It was off everywhere and down on power.

[Kyle@FTP]

Originally Posted by moggey01

Fastest I know of is a 7.70. It was an experimental Pro Stock truck. Todd Bevis built the truck for Raymond Martin. It used an air bag on top of the rear end as a stabilizer with coil overs. Rodger Brodgon bought the truck and never qualified with it. It had longer than normal 4 link bars . They thought this was worth a try because of the wheelbase. It was off from the conventional setup by over a tenth.. 60 ft was a 1.06-07,1/8 was 4.80s. 7.70s at 175 or so. It was off everywhere and down on power.

Great info, thank you. I will look it up. Although it is a bag and a coil on the rear ill take that as a a good sign. 7.70 is a little faster than I would like to go in a truck.

[Wasted Income]

My 69 turbo 5.3 C-10 on air went 11.95 @ 115. That was at about 500 rwhp...would have went faster for sure if I'd turned the power up instead of building the blazer. Dead hooked, and was solid and stable all the way down the track.

I'll try to dig up the timeslip.

[low&slow]

Originally Posted by Wasted Income

My 69 turbo 5.3 C-10 on air went 11.95 @ 115. That was at about 500 rwhp...would have went faster for sure if I'd turned the power up instead of building the blazer. Dead hooked, and was solid and stable all the way down the track.

I'll try to dig up the timeslip.

You got bags on all four corners?

[Wasted Income]

Originally Posted by low&slow

You got bags on all four corners?

It did. It's a K10 now with leaf springs on all 4 corners