XR4ST

[85merwhat?]

Several years ago I bought a non rolling shell from Robert Urfer. It is the fifth Merkur I have owned. A couple years ago I started putting together some ideas I have had into this shell. The purpose of this build was for race only. First I needed to get the car rolling. I brought it home on a pile of pallets. I knew of the VW strut idea and found a Solo Werks Golf MKIV R32 kit which had front coilovers, rear springs, and shocks. I had new front control arms laying around and the shell came with most bits to put the rest together. The rear springs and shocks weren't quite what I had expected but I wanted to try them out anyway. Here is what I came up with:










Next, I wanted to put in a modern engine. I thought about doing the 2.0 or 2.3 ecoboost but the price of the engines scared me away. Then I found the 1.6 ecoboost. Engines are cheap and readily available from Escapes, lightweight, and capable of over 400hp. To make it run I found SCS Delta makes standalone ECUs and harnesses for many different applications, including all the 4cyl ecoboosts. The ECU and harness work great. To make the 1.6 engine fit required lots of fabrication. Notched the front subframe, cut into the firewall and trans tunnel, grind bosses and material from oil pan, fabricate mounts, etc. RWD Motorsport make conversion bellhousings for lots of things, including the Ford Sigma pattern(1.6 Eco) to T9 trans. Having owned 5 merks I should have plenty of those right? Nope, only own T5s, so I had an adapter plate made for the RWD Motorsport bell. Installed an Aerostar driveshaft, foxbody gas tank, Wilwood 4 pots and Focus SVT rotos up front, Focus front calipers and mustang cobra rotors in back, other necessities to make it go and I had my first Auto X event last weekend. Here are some pics along the way:

[85merwhat?]

Here is a pic from the Auto cross event and the results,32 X prepared. Please keep in mind i havent autocrossed in over 5 years, this was the first time driving the car hard, first time driving the car with those tires/wheels(brand new Toyo R888R 245/45-16 16x8). I flat-towed the car to and from the event cause I figured something would break lol.

[John Brennan]

Nice going! I have this engine in my FiST, and even bone stock, it's very potent, really moves the car. Props for innovation and execution, looks terrific in there!

[nathankershaw]

You definitely win the award for thinking outside the box.

Great build!

[merkurdriver]

Really cool build

[DPDISXR4Ti]

Way cool! Neat that you moved the engine back enough to use a 45.5" Aerostar driveshaft as-is. Or did you have to shorten even that?!

Any pics of the inside where you came through the firewall with the engine? No heat on this car?

I like the convenience of using the short rear springs, but I wonder if that's just too little travel? Are the short rear shocks supposed to be matched to those?

[Esteban]

I was worried the rear spring would unseat and not line up when it compresses again.

[85merwhat?]

The 96-97 4wd aerostar driveshaft is the same length as the mustang shaft. I swapped over the rear flange with a conversion u joint. The front slip yoke, although shorter, had the same splines and rubber ring dampener so I left that alone. Still using the adapter for the rear flange. It is almost all the way in the trans so I may make it shorter at some point due to the dust boot on the tailshaft seal is being compressed.

I shaved down the rear rubber bump stops to fit very snug inside the top spring perch. The perches are adjustable for height but the height was too tall for my liking so I took out the bottom rubbers and put in the thin plastic ones the springs came with. The adjusters still are turned all the way down, I would like it to be shorter still but oh well. With the suspension in full hang the springs are still compressed so they can't come off the bump stop nub.

I thought I took a lot more pictures along the way but can't find them. There is definitely no room for a blower or heater box, the DI pump sits off the back of the head. I will grab some more pics in a bit

[85merwhat?]

Here are some more pics. Hard to tell how far i cut into the firewall since I put in new sheet metal and thermo-tec foil and retardent but a lot of room is needed back there for the vacuum pump, direct inection pump, water outlet, and sensors. I used block off plates from SBD Motorsport for the water solenoids and installed an external oil cooler. The one pic shows how close the oil pan is to the steering rack. I thought about switching to a Titan dry sump oil pan from SBD but dont know how much more clearance it would have given since the pickup is at the front. I am using the AIM MXS Strada dash display which communicates with the SCS Delta ECU. Dash piece is very nice, able to fully customize. I just need the GPS Speed module so I can tell how fast Im going. Next step after that is to get an LSD in it.

[Marc]

Nice to see someone thinking outside of the box.

But I do have to say that a few things don't really seem like a great idea to me... The rear springs don't have much travel and will probably coil bind which you don't want. Apart from that it also seems like they could pop out quite easily. I also don't get the point of using the extensions on the shocks, it seems they would have fitted straight away... But in general I don't understand why you are fitting springs and shocks with (I assume) unknown spring and damping rates that are probably not matched to each other. There are lots of options available that will give great handling. Why bother with random parts that are not intended for this car?

I also wouldn't use the bracket for the front anti roll bar. Normally there is a recess in the chassis rail where the bush sits in. But it seems like you have fitted a flat plate behind the bush that has some open space on the back due to the recess in the chassis rail. When braking the arb takes about all the braking force and you get huge forces on these brackets. Now it seems like only the bolts are preventing the bracket from sliding down, that is if the brackets don't start bending first...

And lastly it seems there would be quite a big shear force on the bolt for the engine mount. I would expect it to shear off in time.

Please don't take my post negatively, I just don't want to see anyone crashing their car due to things that could fail...

[85merwhat?]

Constructive criticism is always welcome. As far as assuming, well u know what happens there. The spring rates provided from Solo-werks are linear rate 450lbs for front, and progressive working rate of 590lbs for rears. Regardless of spring rates, they we're designed for a heavier, AWD vehicle. If the coil travel/bind on the original intended application isn't an issue I don't see how it would be here. Also it's impossible for the springs to come off their seat as the shocks at full extension keep the spring slightly compressed. There is a 1.5inch long nub/stud thing encased in rubber in the center of the spring mount that keeps it centered. Now if the shock broke that would allow it to happen, but that's a different story.
The shocks require the extensions because they are 5 inches shorter than the original merks. I wanted to use them because Solo-werks states they are valved to match the springs in the kit(and they are a purty blue color).

I didn't study bolt shear force in college so I can only rely on the expertise of others(and Google) for me to think the engine roll mount I made is adequate. From what I can gather the basic shear force of a M10 grade 10.9 bolt is about 7000lbs on the threaded part of the bolt. This means nothing to me because I can't accurately measure the force being applied in it's application. The bolt holds a steel cylinder and clamps it to the subframe. The steel cylinder is encased in rubber which is connected to more steel which is attached to more rubber and that rubber is attached to different steel and that steel is bolted to the engine block. In other words the rubber portions absorb the majority of the shear force, and the bolt maintains the tensile force. I don't think there is enough shear force left to come close to 7000lbs. I can totally be wrong with my thinking and specs, but that's my logic. Even if the bolt did break, it would not result in a crash or an accident as the engine and trans are fully supported by the other two mounts

As far as the sway brackets go, I took into consideration the forces that are applied there. Didn't put too much thought into other than the new sway brackets and metal base plate are the same thickness as the original merks, and they are $30 for the whole kit. If it starts to show any abnormalities I can always source new original merk stuff. After autox and driving around for a month it looks the same as when I installed them.

[Mike McCreight]

Fab-tastic.
This is very refreshing, thank you.

[Marc]

Thanks for replying, some people wouldn't like any comments that could be regarded as negative. But it's good to hear that you thought about these things and know the spring rates.

The original rear spring is mounted much higher, so has much more travel. Normally the bump stop is mounted at the point where your spring starts. So when your spring is fully compressed the original one would have some travel left and then hit the bump stop, which it seems yours does not have.

Regarding the rear shocks to be valved for the springs, that's probably the case when fitted on the car they are intended for. But now you are using them in a different location which means the motion ratio for both the spring and the shock are very likely different than original, which means they aren't matched anymore. The spring has a motion ratio smaller than 1 (it moves less than the wheel), while the shock has a motion ration bigger than 1 (it moves more than the wheel). This means the shock needs less damping over a certain shaft length than when it would also have a motion ratio lower than 1. Of course it could by coincidence be that the motion ratios for both spring and shock are the same on the Golf IV, but that's seems highly unlikely to me.

But it's nice to see someone trying something different.

[85merwhat?]

Here is a good picture showing the original rubber bump stop inside the top spring perch. Setup is still going strong, slowly turning up the boost, up to 12lbs now. Have an autox event on 9/16 and another on 9/30.

[timxr8]

I'll hop on a little bit of a critique. Your brakes are very strange. Essentially, depending on piston sizing, you have more powerful rear brakes compared to the fronts. Doesn't matter if the front are 4 piston, they are the small Wilwoods. You have to seriously restrict the pressure to the rear, which delays the actuation of the rears and makes it dead weight until you get further down the pedal. If you go with a smaller piston rear caliper (43mm is stock, which still used a restrictor) you will get quicker actuation and better modulation.

What size pistons are on the front? They look like the Dynalite 3.5. You should really go for the Superlite Internals. They'll bolt right on and give you the correct pad sizing. Seriously, the Dynalite/Dynapro Pads are almost half the surface area of those 08-11 Focus Front Pads.