Sequential Gearbox Upgrade

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PostPosted: Thu Mar 11, 2021 2:39 pm
I believe we will see 8-10 Sadev cars at Rd Atlanta. My guess is more at VIR which will certainly provide good data from different level drivers. Going back to Orange roll hoops might be the answer for distinguishing the two transmissions. We have a great CSR network and I would recommend contacting them for any questions or concerns you may have. Nothing is secret, unfortunately we are not CNN or Fox News. It is my understanding that there are 75+ orders in place.

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PostPosted: Thu Mar 11, 2021 6:19 pm
I guess it's safe now to take the orange tape off my roll hoop from the Gen3 upgrade :)

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PostPosted: Thu Mar 11, 2021 8:02 pm
Ed Cavalier wrote:Can someone post the gear ratios and final drive? I assume that at this point there's no reason for them to be in "double secret probation"?

Also, why is this information coming from unofficial sources? Why hasn't there been a technical bulletin, an official memo from Enterprises, or even something on the SCCA-E website?

I'm grateful that my CSR forwarded the "CSR Call Report" and that Grayson has provided important information, but is that really the way that something as significant as this should be promulgated to all of the drivers? Shouldn't Enterprises have sent the "send in your check" notice to all the drivers at the same time? I realize that most of the driver's are in a CSR or a professional support shop's stable, but does that justify them getting the information before the drivers that aren't in those stables?
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PostPosted: Thu Mar 11, 2021 10:34 pm
From that table it is easy to see why there is a performance boost.

Given that you shift at 6,750 (perfectly with no RPM loss...) here is where start the next gear with the current transmission:

1:2 3,632
2:3 4,732
3:4 5,076
4:5 5,358

That will now be:

1:2 4,635
2:3 5,079
3:4 5,444
4:5 5,616
5:6 5,906

2nd gear will be more useful, and the tight grouping of 3 to 4, 4 to 5, 5 to 6 will
keep the RPMs in the higher part of the power curve.

Now add in a faster shift with less loss of RPM using the electronic throttle body,
and even if that saves a 1/100th of a second per shift...it will add up.

I was a careful shifter and had 1,100 laps and 3,400 miles on the box before it broke.
Looking at AIM data, I could see how much speed I was loosing on 4 to 5 trying to avoid
going from 4 to 3 by accident, but I really didn't want to zing the motor. This is going
to help a lot.

Is it time to start the over under pool on the weight penalty?

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PostPosted: Fri Mar 12, 2021 1:01 am
A weight penalty (in addition to the extra weight already inherent in the new box) that keeps the old transmissions competitive would be interesting, although a few skinny little people like me are already carrying around alot of ballast. Now there's a debate we haven't visited in a few years :)
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PostPosted: Fri Mar 12, 2021 2:43 pm
Interesting comparison gear ratios. If I translate that to shifts at Thunderhill, for example, we would need a shift to 5th on the front straight, then a downshift through T1 to fourth. We rarely get to 5th in an SRF3 without a tail-wind/draft. Apex speed is 95-100, so 4th gear is the same. Entry to two would be between mid to upper 70's mph, so 3rd gear.

This is one area where we "debate' between staying in third and going up to 4th in the 3, since hitting over 90 is likely, so the Gen 4 will likely require an upshift to 4th before getting to T3. Probably a wash, so I'll call it even for the required up-shift and subsequent downshift to 3rd into T3. T3 to the Crow's nest is from ~70 mph to low 80 mph, so that all within the 3rd gear range.

Gear-wise, the Crow's Nest would, technically, be a 2nd gear corner (apex high 40's mph), but since it's immediately downhill, most leave it in 3rd. Entry to T6 is in the mid-80mph range (ideally), so still in 3rd. Shift to 4th would be slightly earlier, carrying you to T9.

Interestingly, T9 will be right on the edge of the SRF4 limit, but under most conditions it looks like the RPM limiter won't be hit, so a downshift to 3rd takes you to an upshift to 4th before T10. Apex speed in T10 is would require a downshift to 3rd.

T11, with an apex speed in the low to mid-50's, is one of those six-of-one corners where 2nd gear is tempting, but most will live in 3rd gear. This is one place where an LSD might be helpful since it's an up-hill left (1.5g), followed by an immediate flatter right / left. Using 2nd gear would require an upshift near the apex of T12, so it's TBD if the 4 has an advantage (and how much).

Up to 4th down the backstraight to the T14/15 turn back to the front straight. Maxing out at under 110mph, that sets up another possibility to use 2nd gear as the apex speed is in the upper 50mph range. Most just leave it in 3rd. Back to the front stretch to finish the lap, with an upshift to 4th shortly after entering the straight.

Looks like, at a minimum, an upshift to 5th will be required into T1 (and subsequent downshift to 4th). T2 to T3 will require an up-shift to 4th and downshift to 3rd entering T3. There may be use for 2nd gear in the three areas of the track, but likely not required (or helpful without LSD. The 4th gear ratio will likely make the most difference in overall performance. I suspect the sequential shifting will help on up-shift times for some, but on a two gear track, with 4-5 upshifts, I suspect that won't make a large difference.

On the weight I think a nice round number like 1,600 would work for SRF4... (that should get things going!)... (and take SRF3 down to 1540...) ;-)
Bob Breton - SRF 51 - San Francisco Region
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PostPosted: Sat Mar 13, 2021 3:54 am
Thanks Jisu and also thanks to Tom, Paul, and Bob for the subsequent, insightful posts.

I'm really looking forward to reviving the minimum weight thread. Considering that I'm 165 lbs, I'm in favor of "lower is better". On the other hand, for the COVID-19 vaccine wait lists, I'm 5' 6" and 200 lbs. (Not really, just joking. But I did register with factual information for the wait lists in every county around my home county of Harris Texas and I got "picked" in Chambers County for the Moderna vaccine. It was a 45 minute drive to get there, but that's a small price to pay. I am a bit concerned about my subsequent, intense desire to throw away all of my Apple hardware and buy Microsoft products. I'm sure that it's just a passing phase.)

A question for those of you who understand the Zuckerberg universe: After seeing the link to the Facebook group, I decided that I needed to join Facebook to keep-up with the SRF community. I created an account and requested to join the "Spec Racer Ford" group. From that point on, I can't access that group. I get a "This Content Isn't Available Right Now" screen. If I log out of Facebook, I can see all the content. What the heck is going on with that? I can see the content if I'm not logged into my Facebook account but I can't if I'm logged in?

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PostPosted: Mon Mar 15, 2021 1:50 pm
Just got the email this morning. Looks like this will take me out of the class in the next few years. Just did a Gen3 upgrade with transmission rebuild/upgrade and have only been able to run 1x due to COVID and kids. I can't take a $12.5k hit on new hardware then add install and still have budget to run. The sole reason I got into this class and out of formula cars was so that I could run competitive hardware with the guys up front. No more excuses when looking at timing sheets. I get that we needed an update to the gearbox. I agree that this looks really cool, but with the price tag it seems like this just became another $40k+ car class. Wish they could have done this with a smaller budget in mind. Maybe that's not possible. Maybe I'm the minority who is trying to do this on a (much) smaller budget.

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PostPosted: Mon Mar 15, 2021 3:12 pm
I think you'll have plenty of company through 2022 as people take time to upgrade. Conversely you can still sell a good 5-speed box for decent money for another year which softens the blow. I agree for all-new chassis and upgrades it's really a $40k+ car (plus you need to tow it), but I think you'll see second-hand SADEV cars become available eventually.
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PostPosted: Mon Mar 15, 2021 7:21 pm
roun0016 wrote:Just got the email this morning. Looks like this will take me out of the class in the next few years. Just did a Gen3 upgrade with transmission rebuild/upgrade and have only been able to run 1x due to COVID and kids. I can't take a $12.5k hit on new hardware then add install and still have budget to run. The sole reason I got into this class and out of formula cars was so that I could run competitive hardware with the guys up front. No more excuses when looking at timing sheets. I get that we needed an update to the gearbox. I agree that this looks really cool, but with the price tag it seems like this just became another $40k+ car class. Wish they could have done this with a smaller budget in mind. Maybe that's not possible. Maybe I'm the minority who is trying to do this on a (much) smaller budget.


I feel for you. Seems like we have stepped a bit away from one of the main aspects of the class, budget oriented. Back when the class started a car was $10k according to some info I have found, that amount adjusted to 2021 is a bit over $25k for a brand new car!

I know that racing costs are always increasing, but that initial value is a bit jarring compared what needs to be spent upfront for a car now. You will struggle to find a used car for $25k. I have been trying to roadmap about going to Gen 3 in the future from Gen 2. Now it looks like I will be staying in a 2 for the foreseeable future. The Gen 2 field here in Cendiv has good counts, but I would like to have raced at other tracks in the country and race against more people in this great community. No way that is happening if I have to spend for the Gen 3 upgrade and a Sadev.

I am not knocking Enterprises. The team has done great to keep this class going and has to look for class longevity. The gearbox was the weak link for this car we all know that. We are not only competing against each other but other classes to bring in new drivers and customers. Where does the SRF fit now in the price range when a Spec Miata can be had for under $10 and a Radical can be had in the 40 - 60k range. There are some drivers I was unable to convince to race SRF. But they went the Miata route, due to price, ability to race anywhere and also the Mazda shootout and chance to progress. How do we get those new drivers?

Maybe the gearbox will be one of the answers, but that pricepoint is going to be really hard to swallow, especially with so many having to cut back or not even race this past year due to covid budgeting restraints.

Thank you all who have posted the information and have done the calculations.
Chris B
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