Mr. Spam's Street and SCCA Autocross build (modified)

[STHeart]

Also, I created this checklist document to help me in removing my transmission. Thought it might be useful for other folks who want to drop their transmissions as well for whatever reason.

 

[STHeart]

New license plate!

 

[Fusion Works]

Why do you have rafter ties inside your wheel well?

 

[STHeart]

Those are brackets for home-made ride height sensors. I get voltage changes with ride height and correlate those with downforce (or lack of!). I WAS in the middle of working on underbody fairings (which seem to help) when I had the AutoX transmission incident.

 

[STHeart]

Why do you have rafter ties inside your wheel well?

See above.

 

[STHeart]

I've done one-side.

 

[Fusion Works]

How much lift are you seeing?

 

[STHeart]

How much lift are you seeing?

I haven't really re-run numbers yet - wanted to get both sides done before doing that. As noted above, I'm working through the transmission issues. I'm literally going to actually drop the transmission tonight. Got both axles out last night (pictured). I figured while I've got everything out I will also:

- replace control arms with the DNA (not adjustable) set
- replace all motor mounts with the Damon motor mount set
- do the Whoosh over-driven lightweight water pump pulley
- as long as I'm Whooshing, install the Whoosh motorsports stage 3 COMPLETE SMF clutch kit. I had the Spec stage 3 kit, but I've had nothing but transmission headaches ever since installing that kit (lost reverse synchro x2). The Whoosh SMF kit seems to not cause those kinds of issues, and folks are using it in 350+ hp builds, so I'm giving it a try.

Any other ideas? I'd be interested to hear from people who have done axle upgrades (MFactory, Traxxis) as to what their experiences might be.

 

[STHeart]

How much lift are you seeing?

Also, re-reading your question - I AM seeing a good bit of lift. About 12-15 pounds between stand still and 90 mph. The lift seems to be mid- car - maybe a bit more on rear wheels.

Based on the numbers I'm getting, this is my best guess for distribution of lift forces at speed on the Fiesta ST. First image is just my best guess about where the lift forces are located. Basically the car is wing shaped (curved on top, flat on the bottom) and it's going to produce lift.

One way to counter the lift is to create a complimentary shape on the under side of the car - ideally a bulge dipping toward the ground at the mid-body - but in reality folks use things like rear diffusers, rear wings, front canards and front rams to try and achieve this. I'm actually using the panels to try and create a small "bulge" like I just mentioned. The second picture gives the idea - obviously the picture is exaggerated for emphasis, but shows the concept.

 

[Fusion Works]

You are better off restricting how much air goes under the car to begin with. Deep front airdam/splitter combination, deep side skirts, etc. If you keep the air out from under the car, the pressure can be lower.

I figured it made lift, most OEM production cars do. Its also part of why the car is so sensitive to cross winds at highway speeds.

Factory axles are fine. Traxxis is RC car axles, LOL.

Running a Spec Stage 3 with a Fidanza flywheel. Have no transmission issues since I put it in the car 30K miles ago.