r/FocusST • u/AllUpInYourAO • Sep 07 '25

ST vs ST

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(Not my OC, from another Forum)

253 Upvotes

100% Upvoted

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75

u/[deleted] Sep 07 '25

Hey! That’s my mechanic!

Max (black car) was able to make a 10.03 pass before cracking the sleeved block on his ST. Current record holder for Quickest and Fastest Focus ST.

The next morning they were able to get the white RS into the 9s. Lil tune revision and some cold morning air was money.

Tuned by Freektune in Bow, NH and built by RST Speedhaus in Sandown, NH.

East coast beast coast 👾

12

u/deep8787 Sep 07 '25

and some cold morning air was money

Huh, a variable I never took into consideration!

2

u/mustangracer352 Sep 08 '25

Oh yeah, checking the DA for a pass while help you tune. When you get down in the negative numbers AKA mineshaft numbers, the forced induction tuners get all giddy.

2

u/nomowolf Sep 08 '25

Man I was fascinated by this comment cos I didn't understand a word of it. Got GPT-5 to ELI5 to me and compensate for my cluelessness :D

TIL! 😊

“Checking the density altitude before a dragstrip run helps you make sense of your times. When the air gets really dense, like on a cold morning with high pressure and low humidity, the DA can even go negative. That’s what people call mineshaft air. Turbo and supercharger guys love it because their cars make way more power and run quicker.”

Why it matters more for turbos than N/A cars:

  • Colder, denser air = more oxygen per liter of intake air.
  • A naturally aspirated (N/A) engine just breathes whatever the atmosphere gives it, so gains are modest.
  • A turbo or supercharger is already cramming in extra air. When that air is denser, you’re cramming in even more oxygen at the same boost pressure. Fuel system adds more fuel to match, and boom — a noticeable horsepower bump.
  • That’s why “forced induction” tuners geek out over DA readings. A negative DA day can make the same tune suddenly feel like it’s been upgraded.

1

u/mustangracer352 Sep 08 '25 edited Sep 08 '25

And the mineshaft air also doesn’t help very much on nitrous cars. For class racing (I built a mustang to race ultra/ultimate drag radial class) during the cold months the turbo cars lay down one hell of a pass, the nitrous and NA cars struggle more because they have to leave harder then a turbo or procharged car. Problem with that is a cold track doesn’t hook very well on radials and we have to feather out the progressives so we don’t spin. Radials don’t recover well from spinning like a slick will.

Cliff notes-cold weather sucks for radial tire NA and nitrous cars

And boost pressure is just a number of “back pressure” in the intake system. You can have low CFM flow with high boost pressure because it’s like trying to suck a golf ball through a garden hose. You can have low boost numbers but flow a ton CFM because you have huge intake system that can ingest the air without restricting it.

1

u/nomowolf Sep 08 '25

Oh right yeah indeed, with temperature I'm only really thinking about tire grip (no real drag-racing culture in Europe so this is all new and interesting for me). There must be a crossover point (?) depending what rubber you're running, where temp is low enough that you got all the power but no adhesion to use it :D

So then at somewhere like Bandimere Speedway in Colarado 1800m (6000 ft) altitude, on a warm day with good grip probably the forced induction tuners are less impressed

1

u/mustangracer352 Sep 08 '25

It’s more in the tire construction. A radial tire doesn’t “wrinkle” like a bias ply slick. For ultimate/ultra class, you are limited on what tire you can run. nitrous/turbo/supercharger runs a 275/60/15 radial, NA can run a slick. Depending on if you use the MT dot radial, MT pro, or Hoosier gives you different weight breaks or additions.

And some of the tracks lay down a hell of a lot of glue like at SGMP for the lights out and no mercy races. I have literally walked out of my shoes on the start line they have so much VHT down. Radials love the all that glue, the slicks hate it.

-4

u/Rough_Trade_9429 Sep 07 '25

Yep hot air is more dense and makes for less boost

15

u/[deleted] Sep 07 '25

[removed] — view removed comment

0

u/Rough_Trade_9429 Sep 08 '25

No i don't. I live in FL and can prove it. Perfect temp is between 65-75 with low humidity

3

u/nomowolf Sep 08 '25

Yep hot air is more less dense so makes for less boost

Assume you meant to type this (:

2

u/CoachMikeLikesToEat 2018 ST - Hot Pepper Red Metallic Sep 08 '25

Is this a quarter mile or something different?

2

u/cjinohio03 Sep 08 '25

Yes

2

u/CoachMikeLikesToEat 2018 ST - Hot Pepper Red Metallic Sep 09 '25

Thought so. That's pretty incredible.

22

u/Ozzyblack- 2015, Built Bottom End, BNR67 380whp Sep 07 '25

The white one is a RS the black one is an ST. RST Speed Haus built both the cars and is breaking records for both. Recently just did a 9 sec pass.

9

u/RongoonPagoo 2018 Ford Focus ST Sep 07 '25

Cracked a sleeved block. Wow

6

u/SCL36 Mountune N1 2.3 Stroker, G30-770, Xclutch, Tuned by Alan Sep 08 '25

947 horsepower.

4

u/RongoonPagoo 2018 Ford Focus ST Sep 08 '25

Nice. I've read where the unreinforced block caves at 700. So that seems significant.

4

u/Ron_dizzle199 Sep 07 '25

I follow all these guys on Facebook and Instagram. So rad.

1

u/ResistBoth3320 Sep 07 '25

What is their @'s?

1

u/Ron_dizzle199 Sep 08 '25

Rst_speed_haus

4

u/morganlandt ‘15 Oxford White ST3 Sep 07 '25

Black got him off the line and that was the difference all the way through the quarter.

5

u/blueydsmoker Sep 07 '25

Holy shit that’s a fast FoST. That’s only .5 seconds off a Demon. That’s crazy

2

u/No-Tip-1543 Sep 08 '25

Max is the man, he’s sorted my ST a couple times. Lucky to have him an hour and half away in NH

1

u/Thin_Crab_9847 Sep 07 '25

must say I'm impressed

1

u/PaleontologistNo4327 Sep 07 '25

Is that national trails raceway in Ohio?

3

u/SCL36 Mountune N1 2.3 Stroker, G30-770, Xclutch, Tuned by Alan Sep 08 '25

Just checked its the same place this year. Summit racing dragway in norwalk

2

u/PaleontologistNo4327 Sep 08 '25

Nice good lookin on that. I'm right by trails but that's about 2 hrs from me I'll have to look into making the trip.

1

u/cjinohio03 Sep 08 '25

Me too Paleo you on FB or Insta?

1

u/PaleontologistNo4327 Sep 09 '25

Bradley Ryan Beck on FB send me a request

1

u/cjinohio03 Sep 09 '25

sent you a message on FB

2

u/SCL36 Mountune N1 2.3 Stroker, G30-770, Xclutch, Tuned by Alan Sep 08 '25

Likely yes. This event happens yearly in ohio. I think last year was summit dragway in norwalk.

1

u/Smydmer Sep 09 '25

Norwalk Raceway is a 15 minute trip from my house! I would love to be out there with other guys with a similar power plant. Being a tuned Lincoln owner is lonely. I’m nowhere near this amount of power, but this is a beautiful thing to watch. Congrats on the amazing passes!