Category: Rear Suspension
More welding and rear suspension..
Have been doing lots of underbody welding.. so not a whole lot of exciting progress to see latetly.
Added the final pieces to the rear of the subframe connectors to make them blend into the rear frame rail. Once the IRS comes back out, this can be finished up. Also started to weld the connectors to the floor pans.
Now that the rosisserie is in use, we added the final bracket to the IRS in the middle of the car. These IRS units are notorious for wheel-hop issues, so hopefully stiffening all of this will put that to rest.
Konis and Fuel..
Scored a pair of used Cobra IRS Konis for car #2. Fresh rebuild on these with zero miles. Came with shock dyno sheets too which was a bonus. With car #1 getting closer to an operational state by the day, we are trying to get everything in hand to be able to dive into the next one.
Moving onto the fuel system – we decided to run a 2003/2004 Cobra fuel pump assembly. This is a unique 2003/2004 only setup that comes with dual pumps to provide additional fuel with the supercharged application. Since they cost a fortune new, we opted to go the used route as usual. We decided to run a returnless system like the stock vehicle. This system uses an FPDM (Fuel Pump Driver Module) to duty cycle the fuel pumps to target a desired fuel pressure which is measured by the computer at the fuel rail. Alternatively, we could have run a return system with a pressure regulator, but we opted to use what came with the Mustang originally.
As for fuel tank – for now we will use a stock 68/69 Torino tank. We will weld in a flange on the top front center area to allow this fuel pump module to bolt right in. We will build a reservoir/baffle setup at the base of the tank similar to what is in a newer Mustang to help prevent fuel starvation. Float rod will be a custom one using a stainless welding rod to take the shape of the Torino tank into consideration.
Rear Suspension Near Complete
Finished tacking in the pass side wheel well and made up the shock mount for that side too. Everything is ready for final weld. Time to move back to something we have been putting off for a while now – spring mounts, spring sizing and locking in the ride height with all these parts which turned out to be easier said than done. As you can see – we ended up making a new upper spring mount to clean things up and transition it into the existing frame.
Three main parts to the rear suspension travel – and each stage has it’s own issues:
Rebound/full droop position – this is with the wheel pushed all the way down. The car will rarely see this position, but is is possible and will always occur when lifting thcar in the air using a hoist. The first issue we ran into is that our springs are too stiff and the spring will just fall out of the car as is as they are all their free length at this position. Simple solution – just buy longer springs right? Unfortunately not that easy – if you get longer springs, the car will just sit that much higher. Since the motion ratio is approx 0.5, if you make the spring .5″ longer, the car rides 1″ higher. Solution here is to run Hypercoil helper springs. You can completely compress these springs by hand, but there is enough spring force to keep the main sping in place. They compress to a mere 0.3″. The keep the lower spring in place on the lower mount – we opted to use a nylon part made by Vorshlag which some may recognise as a BMW parts supplier. To keep these in place, we just made up 1 3/8″ posts as you can see in one of the final pics. We also used a similar sized spacer to keep the ride height adjuster in place. The other key point about this position is still being able to get the spring adjuster in position on the top post.
Design position – this is the position the car naturally sits at full of fluids on the ground. To fine tune the ride height, we opted to use 60mm ride height adjusters made by AST – yet other BMW part. Based on the second picture – you can see that the helper springs are full compressed and the entire weight of the car is now in the springs. To get the car at the correct height was a combination of spring length selection (since the rate was fixed to achieve a certain ride frequency), helper spring height, coil spacer height, and ride height adjuster overall height. The goal was to have the height adjusters at their midpoint at design position (which they actually sit at although not shown in the picture).
Jounce position – this is with the wheel pushed all the way up and riding on the jounce bumpers, which in this case are built into the shocks. Couple of issues you have to watch out for here – coil bind on the springs, control arm contact to the frame, and upper and lower spring seat misalignment. For the purpose of illustration, I stuck another spring on the car as compressing the other springs would require anchoring the car to the ground.
With all this in place and all the issues worked out (for now), the rear suspension design is complete and just needs to be final welded in place. This will make the process much easier on car #2.
Only thing left in the rear suspension area now are the brake line routing and getting all the ABS parts in place.
Minitubs..
Managed to get some things done over the past month or so. Floors are in the car and basically done and now ready to weld in. Decided to move back to the rear suspension and things back together for good. First step was to add 1.5″ to the rear wheel wells to make them clear the tires, and then notch the frame out for the 2.75″ shock mount tubes. Once the shocks were in, we were able to confirm the shock jounce and rebound travel and everything looks OK clearance wise. Wheel wells are now tacked into place and ready for final welding. Sure would be nice if someone out there made Torino sheet metal parts :). Still lots of welding to do here, but getting much closer by the day.
Firewall, cooling module and more..
Suppose it is about time to post some updates. Making some decent progress lately.
Keeping in the theme of used parts.. picked up some more of them. Found a set of nearly new Energy Suspension 4.6L motor mounts and also a Wilwood proportioning valve. Had to buy the oil filter adater new though – the one from Ford Racing is a nice piece (M-6881-C). Planning on running a remote oil filter w/t-stat and also an oil cooler in front of the cooling module. This part also increase the block inlet hose to 2″ to further reduce the possibility of water pump cavitation.
We made up custom radiator and condensor mounts which allow us to get them both between the frame rails to keep them as low as possible. This way the degas bottle can be mounted where it was intended to go and remain the highest point in the cooling system, but at the same time being low enough to clear the hood which is does nicely. All these parts are from a 2004 Cobra which uses a 36mm all aluminum radiator. All other Mustangs except the Mach 1 have plastic end tanks. A/C compressor is now in and the new Mustang heater box also fits on the firewall. Just need to run the lines and the A/C system will be complete.
The firewall has been completed and is ready to install along with the floor pans. Rear suspension is nearing completion and just needs to be final welded. The only thing missing in the pic is the upper coil spring retainer. ABS wiring is now in place. Last thing to do is run the hard lines which will come next.
As an aside – I had never used the wet toilet paper trick to remove a pilot bearing so I figured I would give it a try. I am used to the messy grease trick. Surprisiningly this worked like a charm and clean-up is a breeze. You sure can fit a lot of paper in there! Installed a resurfaced 2004 Cobra aluminum flywheel, clutch, pressure plate, throwout bearing and clutch cable. Trans side of things is ready to go. Just need to get the mounts in.
We put the car on the scales and put every part and piece we planned on putting on the car. Looks like the car will come in at around 3450lb curb weight (56%ft/44%rr). With driver and gear we are looking at around 3650lb track weight. We put the car in the air and measured all of the corner weights and using the motion ratios front and rear figured out what spring rates to use. We are using 2.5″ ID front springs and 60mm rear springs from Hypercoil. The target is to run a front ride frequency of ~1.55Hz and 1.7Hz in the rear for the street. For the track the ride frequencies will be similar front to rear.
IRS Bearings..
Front wheels went out a week or so ago to Weldcraft Wheels to get narrowed 1″ to 18×9 and we expect one set back this week. After that the car can actually sit on the ground on actual suspension and not have the tires rub on something. Replaced the rear wheel bearings on the IRS as they are a weak point in the design and one was on its way out. They are done and back in the car again now after cleaning them up and pressing in new bearings. Also mocked up the front sway bar and fabricated most of the parts needed for the rear spring perches. Need to grab some more pictures and post them.
Rear IRS and new wheels..
Moving right along.. been a busy week. Our goal was to have the car ready to go on the ground by the end of March. We were working right up until 12:00 and baraly finished most everthing. Just need to finish up the rotisserie and it can go back on the ground for the first time.
Drilled out the frame for crush tubes and welded those into the frame so the brackets can be safely bolted to the frame structure. Once those were done, it was time to weld the tubes at all 4 corners of the assembly. We pulled the entire IRS out and finished all of the welds up. It kinda looks like the tubes came that way from the factory :).
Also may be changing the wheels up a bit. We got a couple of set of Roush forged 18×10 wheels (scratch and ding models) and decided we may like these better. As luck may have it, the offsets were very close front and rear. Only problem is that an 18×10 won’t like the front clearances, so we are going to have to get the fronts narrowed since there is no such thing as an 18×9 in this model. Not the hugest fan of chrome, but it is growing on me.
Rotisserie Begins..
Hoping to build a majority of the rotisserie this weekend. Picked up the steel last Friday, and the rest of the parts and pieces should be here by this Friday. Managed to find an auto supplier that had excess steel from jobs that had been cancelled so got it for a good price. Got some 3″x3″x3/16″, 2.5″x2.5″x3/16″, and some 2.5″x2.5″x1/8″. I already had the 2″x2″x1/8″, and that covers everything besides the plate.
Hit a major milestone over the weeked – front k-member is now welded in and the strut towers have both been finished off. We verified the caster and camber settings, and once we established they were correct, it was welded in for good. Front suspension is now ready to go on the ground! Just have to weld up some of the seams once on the rotisserie and it will be a done deal on the front.
Sway bar is the only thing left. Will be using a straight splined bar from Speedway Engineering with offset sway bar arms. Will use a PVC pipe to package one in for now until the bar rates are selected. To select those, final springs rates need to be selected, which is waiting on the overall corner weights of the car. Won’t have those for a while.
The push is now on to get the rear on the ground. We cut the rear mount to size and welded the tube to it. Just need to drill holes through bracket and frame rails, weld in crush sleeves and weld the tube to the IRS cradle. The front mounts are also done and just need to be welded to the IRS cradle. After that it will bolts right up to the frame in the rear. That leaves the shock mounts and springs mounts which are also nearing completion. Looks like we will be on the ground soon. Just need the rotisserie done so we can pick it up of the chassis jig and put it back down on the ground.
Rotisserie ready to build
Made some more progress on the front suspension/firewall. Pass side firewall is now near completion and mates up nicely with the torque boxes (easier said that done). After that, the rear closeout was welded in for good, and then the strut tower was tacked in too. Will finish welding up the tower and then weld in the k-member this week. After that – front suspension is basically done except for the swaybar setup which should be fairly easy anyway. It will be based off a Mustang one.
Moving on the rear IRS once again, we bent up some 1/8″ brackets for the rear mounts. Have the pass side mount almost ready to go. Just need to get some crush sleeves made up for the frame and these will be ready to weld in for good. May be hoping in getting the car back onto the ground for the end of the month. This means car #2 can begin. This also leads to the next step which you can see below.
Almost ready to build the rotisserie. Finally have the design near complete. Casters are ordered, I have the hydraulic jacks from when they went on sale last week, and also have a bearing/housing setup that I found kicking around. Just need to grab the steel. Rotating part is based on a std. trailer spindle which make things cheap and easy to find parts for. Also makes it easy to seal things up for bringing near the sandblaster etc. We will just run dynamic trailer seals on both side of the bearing. Worm gear setup on the end is from a Harbor Freight winch. Made this up in Solidworks 2010 – CAD sure has come a long way. Have this designed so it will pick the car up off the chassis fixture (remove the center section and add the 3rd set of wheels).
Shock towers in.. IRS continued
Couple more updates..
Finally stuff on the front suspension is going in for good. Final prepped everything on the drivers side strut tower, drilled all kinds of holes for plug welds and welded everything in. We will wait until we get the car on a rotisserie to well all the way from top to bottom. With the plug welds ground down, it looks like the pieces were supposed to be there. Just need to weld in the pass side and it will be time to put the k-member in for good. Almost done with the front – hard to believe.
On that note – time to catch up on the back suspension. Finally decided how to do the rear mounts on the IRS. We used one of the 2.5″x1/8″ tubes we have made up for the front mounts, cut one in half and will use the 2 pieces to make up both rear mounts. We lucked out and it looks as though the rear tubes use the same 5″ radius as our bends do. Big thing is the rear mount will still clear the 315’s with stock wheel lips. Just need to go grab some more steel to make up the actual brackets that bolt to the frame as we used a scrap piece for now that was a bit too small. Next we need to make up pockets in the frame for the shocks and clearance for the upper control arms. We’ll be on the ground in no time.
