Scca STX autocross build

[Cligedy]

Hi Jonathan, I remember you. I also remember Dixie that year. I did not drive well. Ugh.

Sorry for the lack of updates. Progress has continued, but a bit behind schedule. This is the newest addition to the FiST. I've had these seats for several years. They are from a Lotus Elise; I bought them to put into my Miata but never got around to it. Now they are Fiesta seats.

Because these are OEM seats, not universal aftermarket, they didn't fit up to the sparco base/ sliders and I had to fabricate brackets. When I did this I was doing final assembly the night before my last autocross, the last bolt wouldn't fit because tolerance stacking meant that the holes I drilled were misaligned by 1/8". It was already late and I needed to be on the road at 6 am for the event. I called it a night and left the seat for later.

At the event, I had easily my best drive of the season. Maybe I'm finally shaking off the cobwebs. I took open STX by almost a second on a 55 second course. I also drove within a second of a very well prepped and driven STX FRS in pro class. That I am closing in on his times is very encouraging. If STH comes to reality next season, then I may have a car competitive nationally. Recall at the beginning of the season I didn't think that was likely.

I hadn't made any changes to the car since the previous event, but now I'm sure that I want to stiffen the rear shocks for better rotation. If that does what I expect then the car balance will be just about spot on, with just a bit of lift-throttle oversteer at the limit.

A bit more camber up front, plus wider tires should get me pretty close to being competitive in STX as is. I'm happy with how things coming together and look forward to further improvements.

 

[M-Sport fan]

^^^GREAT results!

Is SCCA considering breaking the Street Touring class up into individual (by each car's power to weight/etc.) classes, just like /Street is now, or does that H in STH stand for something else?
(I don't get the SCCA rag, so therefore no 'FastTrack Newsletter' IF that is what they still call it.)

Is that a CG Lock I spy on the factory seat belt?

 

[Cligedy]

^^^GREAT results!

Is SCCA considering breaking the Street Touring class up into individual (by each car's power to weight/etc.) classes, just like /Street is now, or does that H in STH stand for something else?
(I don't get the SCCA rag, so therefore no 'FastTrack Newsletter' IF that is what they still call it.)

Is that a CG Lock I spy on the factory seat belt?

The current proposal is to shakeup the ST* classes to further accommodate the proposed ECU rules change that would allow boost changes in tunes. The STH would essentially be the hot hatch class, with the FiST, FoST, Gti, etc. This would take the FRS/BRZ out of the equation for FiST competition. Another proposal would push the Mini Cooper not to STH, but to STU(!) which immediately takes the current top dog out of the class. The FiST won't come close to the power or fitting as much tire as the other big dogs in STH, but we have a meaningful weight advantage so I like the odds of the FiST being a top tier choice.

Good eye on the pics, that is a CG lock. I've been using them for 10 years and I really believe they help when on course. There are similar choices for less money, but I've had to use their warranty before and they stand by their product. Good company.

After installing the seat and driving with it for a week, I'm going to pull it out and fab new brackets. The first time I wasn't 100% sure how I was going to build it, and I had some concerns about clearances and fitments. Now that the seat is in, I see that I have enough room to build a tighter setup. The seat as is sits too high, about an inch higher than stock. I've ordered some angle aluminum and will rebuild what I've already done which should drop the height by about 1.75" and take about 4lbs out of the mounting.

Btw, the stock seats weigh 42lbs. The Lotus seats weigh 21lbs. My full assembly weighs 32lbs. Switching out the steel tubing for the aluminum will bring me down to about 28-29lbs. That is still well above the required minimum but a decent loss compared to stock.

 

[Reaper]

If you know, why pick on the MINI? What secret sauce do they have that the other hot hatches can't compete with?

Their weight is 2600-3000 vs our 2700 lbs, so it can't be that.

 

[Cligedy]

If you know, why pick on the MINI? What secret sauce do they have that the other hot hatches can't compete with?

Their weight is 2600-3000 vs our 2700 lbs, so it can't be that.

I think they are slightly lighter than the FiST with a better rear suspension. The main thing is that they can easily fit wider tires. Maxxis and BFG just came out with 245 width 15" tires, which is a shitload of tire for such a lightweight car. That plus extra power next year gets them the bump.

I will add that that the move seems... excessive. The car probably won't be competitive there.

 

[JLAXR]

The GTI seems to be the middle ground, weight-wise, contender but with great tuning potential. Our wheel and fit really limit our tire options. The 245-40-15 Rival S 1.5 will be at its best if pinched, so 8.5 or 9 wheels are optimal. Our gearing is also such a weak spot, and the BFG 245 has a diameter which is less than 23". Of course the extra torque might make 3rd the gear of choice.

 

[Reaper]

. Our gearing is also such a weak spot....

I would agree. But that's what they said about the ND Miata, and it's tearing things up. I asked a couple top guys how they were handling that and they just shrugged and said "shift". Maybe it's not as big a deal as I've always thought.

 

[KKaWing]

I would agree. But that's what they said about the ND Miata, and it's tearing things up. I asked a couple top guys how they were handling that and they just shrugged and said "shift". Maybe it's not as big a deal as I've always thought.

Well, I guess that works... the FiST does have tonnes of torque down pretty low and the stock ND also is tuned for a whole bunch of mid-range. Not like it's a B16A with a 5 speed where if you drop out of "tak" the car goes limp.

 

[M-Sport fan]

Good eye on the pics, that is a CG lock. I've been using them for 10 years and I really believe they help when on course. There are similar choices for less money, but I've had to use their warranty before and they stand by their product. Good company.

I know, I have one as well for this car, even though I had a 4 point, autocross ASM Schroth installed on a Sparco recliner shell (no longer made) in my A2 GTI 16V when last I autocrossed (LOOONNNGGG time ago!).

That is still well above the required minimum but a decent loss compared to stock.

SCCA sets a minimum weight for seats in the ST/ classes??
Was this done to keep the ultra-wealthy from having an advantage by being the only ones able to afford seats such as the (12 lb.?) $4K+ Sparco S-Light and such?

I was considering a fixed back shell seat for mine, but so many on here (and elsewhere) have given stern warnings as to how potentially catastrophically dangerous those can be when driven on the street, and being involved in a major collision, due to the fact that the factory (and other NTHSA approved aftermarket recliner type seats) are designed to 'give way' safely, whereas one piece shells are NOT (hence why all sanctioning bodies safety rules seem to require a seat back brace type bar with their use, I guess. ).

 

[M-Sport fan]

I think they are slightly lighter than the FiST with a better rear suspension. The main thing is that they can easily fit wider tires. Maxxis and BFG just came out with 245 width 15" tires, which is a shitload of tire for such a lightweight car. That plus extra power next year gets them the bump.

I will add that that the move seems... excessive. The car probably won't be competitive there.

Is /Street Prepared still the lowest class (mod-wise) which allows LESS THAN a 200 tread wear rated tire (i.e.; the Hoosier A/R 7s and the like)?

 

[Reaper]

Is /Street Prepared still the lowest class (mod-wise) which allows LESS THAN a 200 tread wear rated tire (i.e.; the Hoosier A/R 7s and the like)?

Yes, if you don't count SSR.

And I think they got after the seats when people started showing up with kart seats for the driver and child seats on the right.

 

[JLAXR]

Oh, I know our gearing issue is more manageable with our available torque. I am actually curious about how a shorter tire might work with 3rd being the gear of choice. At this year's Fort Myers Pro Solo. King was not shifting to 3rd on his tall 215/45/17 RE-71Rs, while I stayed in 3rd for most of the course on 205/50/16 RE-71Rs. Our set up differences are significant with me on Assetto Garas with everything else showroom stock (including alignment settings) and King on the very heavy stock wheels with single adjustable Konis and larger FSB, and aligned to his settings. I need to ask him if he found better alignment settings than that event. King is a muti national champ in FWD cars but he was still likely getting used to the Fiesta ST, when he beat me by 0.011 seconds after two days. I have always defaulted to 3rd gear even when not optimal for others, so maybe a shorter tire would be the best option for us.

 

[Cligedy]

I haven't done a thrust chart, so my own testing has some variables but I've used solostorm for analysis. When I tested the car in Street trim, the car accelerates as fast in 3rd gear as it does in 2nd at speeds above 45mph. This is partially due to the 2nd gear torque reduction, and helped by the huge low end torque.

Most FiST tunes give better gains at the low and midrange, so ST* with open boost still won't affect us at the top of the revs. So with next year's open boost rules and smaller diameter tires, that would bring the sweet spot for shifting into 3rd down by a few mph. Figure 1-2 mph from the tires/gearing and...

You know what, I'm going to try and build a thrust chart for the car. Does anyone have a good dyno chart they could share? At minimum a high resolution image, or even a .csv file?

 

[Reaper]

I think the 2nd/3rd ratios are 2.05 and 1.36. That would mean when you shift you retain only 66% of your gear multiplication. To have the same resulting acceleration at that point you'd need to be making 50% more torque after the shift. You believe that's the case?

 

[JLAXR]

You would also need to make assumptions about time lost between shifts. Whether that is lost on an up shift to a third gear which could add time to acceleration, or in the often likely scenario, in which third is definitely needed multiple times, save time between multiple shifts. Of course you could always have a tall and short tire setup to help with different course designs.

 

[M-Sport fan]

And I think they got after the seats when people started showing up with kart seats for the driver and child seats on the right.

OK, that makes MUCH sense, and I do not blame the Solo Board for the rule on that basis, since using a kart seat in a car, can be downright dangerous!

 

[Sprayed150]

Following this closely so i can learn off your build and hope for a competitive year for 2018 season, hoping STH happens and works well for us

 

[Cligedy]

I think the 2nd/3rd ratios are 2.05 and 1.36. That would mean when you shift you retain only 66% of your gear multiplication. To have the same resulting acceleration at that point you'd need to be making 50% more torque after the shift. You believe that's the case?

You are right. And now that I've run the numbers, it looks like I was close, but off by a little bit.

As a reference, I used this dyno chart. http://rallyways.com/wp-content/uploads/2015/06/rallyways_fiesta_st_stock_dynojet_chart.jpg I had to make some guesses as to the actual numbers at different RPMs, but we should be plenty close to make this exercise useful.

I also used this as my calculator- http://www.leany.com/DesktopDyno/Page2.html By the way, this guy put a lot of work into this spreadsheet. The conditional formatting to add color to the grids is a really nice, helpful touch.

The grids aren't quite precise enough to pic specific switchovers, but I appreciate the info. Anyway, according to this the car is still pulling strong at 45mph, but that is also where it starts to run out of steam in 2nd. It looks like 50mph is maybe a better cutoff point. Which is to say that if you are going to run out of 2nd gear, there is no need to run to redline if you have an opportunity to shift. If you have an element that requires a brief lift, that is a good chance to shift up. And according to this, unless you drop below ~35 you will stay on top of the broad torque curve. What this calculator doesn't show is the fact that the FiST reduces torque in 2nd gear, I believe by about 30lb/ft at peak. I don't think anybody in HS should shy away from 3rd gear if they are nearing redline.

 

[zohaib]

You are right. And now that I've run the numbers, it looks like I was close, but off by a little bit.

As a reference, I used this dyno chart. http://rallyways.com/wp-content/uploads/2015/06/rallyways_fiesta_st_stock_dynojet_chart.jpg I had to make some guesses as to the actual numbers at different RPMs, but we should be plenty close to make this exercise useful.

I also used this as my calculator- http://www.leany.com/DesktopDyno/Page2.html By the way, this guy put a lot of work into this spreadsheet. The conditional formatting to add color to the grids is a really nice, helpful touch.

The grids aren't quite precise enough to pic specific switchovers, but I appreciate the info. Anyway, according to this the car is still pulling strong at 45mph, but that is also where it starts to run out of steam in 2nd. It looks like 50mph is maybe a better cutoff point. Which is to say that if you are going to run out of 2nd gear, there is no need to run to redline if you have an opportunity to shift. If you have an element that requires a brief lift, that is a good chance to shift up. And according to this, unless you drop below ~35 you will stay on top of the broad torque curve. What this calculator doesn't show is the fact that the FiST reduces torque in 2nd gear, I believe by about 30lb/ft at peak. I don't think anybody in HS should shy away from 3rd gear if they are nearing redline.

This is amazing. Thank you!

 

[Cligedy]

Ok, back from the dead. Work traveling and family obligations have meant that I haven't made any more modifications to the car since my last post. This is especially disappointing since I have parts waiting in the garage to be installed. Nevertheless, I have driven the car in its current setup on a couple of our local sites and this has reinforced my previous feelings. The car does not rotate as well as it should and I need to loosen the rear end. My plan was to address this at the front end, as I have parts to improve front dynamic camber and front end compliance. Because of the time required to do this upgrade, I've been considering alternate approaches.

I have been researching rear sway bars to further stiffen the rear. I had originally not paid much attention to this as an option because the rear end of the FiST is essentially a big sway bar to begin with and I was dubious that a sway bar would be effective. In addition, I knew that the SCCA had declared certain types of rear sway bar as illegal on the Mazda 2, and I didn't want to fall outside of the rules. I think I have figured out their objection and it shouldn't be an obstacle. I've also been reading as much forum feedback as I could about whether a RSB would make the desired change on the FiST.

At this point I'd like advise from those who track or autocross their FiST and have added a rear sway bar. I'd like to know your thoughts on if/ how it affected the balance. Lots of people commenting about adding a RSB either don't directly address changing the balance of the car, or they sound like they don't really know what they are talking about. So to those of you who know the difference, what has been your experience? Will a RSB bring back the rotation I've given up in pursuit of ultimate grip? I look forward to your feedback.