What 3.15 or 3.31 on FI Power Pack (From 3.73)

[K4fxd]

I think the fastest cars are running 3.15. With the gear ratios of the A10 a 2.73 might be better??

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[Jackson1320]

3.15 is the fastest stock gear

 

[tdstuart]

I think 3.15 and a tire will help. I have the 3.15 gear N/A but with the 6r80. Boosted it would be great, especially with the 10r80.

I've been on really bad tires and could light up the rears from 30mph, N/A with some bolt-ons. I think you just need some time and practice. I've been in the rain and went WOT to spin at 80, the car was fine.

275 is not a wide enough tire. The biggest on these cars is about a 305 street tire, even then it doesn't help that much. You need a street slick. Something like the nitto 555 r2, or a MT street radial.

The 3.15 gear itself will likely not solve your spinning problems. 3.15 and a tire should. But I think you should try to get more confident with spinning and controlling the car. IMO while driving straight you should be able to go WOT from 30mph, spin, and hold it for at least a few seconds. Sounds like you are afraid of the car. There may be times when you think the car won't spin, and it will randomly spin, and being able to control the car is very important. I would practice spinning at different speeds and controlling the car. Then get the gears and the tire to hook.

 

[Ptrug]

Can't get pp2 with the auto.

I think 3.15 and a tire will help. I have the 3.15 gear N/A but with the 6r80. Boosted it would be great, especially with the 10r80.

I've been on really bad tires and could light up the rears from 30mph, N/A with some bolt-ons. I think you just need some time and practice. I've been in the rain and went WOT to spin at 80, the car was fine.

275 is not a wide enough tire. The biggest on these cars is about a 305 street tire, even then it doesn't help that much. You need a street slick. Something like the nitto 555 r2, or a MT street radial.

The 3.15 gear itself will likely not solve your spinning problems. 3.15 and a tire should. But I think you should try to get more confident with spinning and controlling the car. IMO while driving straight you should be able to go WOT from 30mph, spin, and hold it for at least a few seconds. Sounds like you are afraid of the car. There may be times when you think the car won't spin, and it will randomly spin, and being able to control the car is very important. I would practice spinning at different speeds and controlling the car. Then get the gears and the tire to hook.

You are 100% correct. I know I need to relearn how to drive her. But regardless, confidence does not stop her from loosing control WOT as she’s configured now.

My tuner (Lund racing) also gave me a mechanical reason to swap the gear. I’ve been working with them for years and they never steered me wrong. After more conversation he agreed 3.15s.

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but as you add power the taller gear will be much harder to hook. also, the taller gear will not have as much top end. with a centri blower top end is what you want, they live in the top end. and the last part is we want to do everything we can to keep it in gears 1-6 at WOT. 7th gear on the 10r80 is the weakest clutch pack so it will slip at WOT. once that clutch pack slips and gets smoked it will take out the rest of the clutch packs and its rebuild time. 3.31s will get you through the 1/4 mile at around 7400 rpm in 6th.

 

[Cory S]

275 is not a wide enough tire.

I'll show you how well my 275/40/19 555Rll's hook at my power level on the street. No different than my 305/45/17 SS's. Wider tires on street asphalt doesn't really do jack but improve cornering. Anything over 650whp should be running a Drag radial anyway.

 

[Ptrug]

I'll show you how well my 275/40/19 555Rll's hook at my power level on the street. No different than my 305/45/17 SS's. Wider tires on street asphalt doesn't really do jack but improve cornering. Anything over 650whp should be running a Drag radial anyway.

So your saying don’t worry about the rubber because it won’t do as much? I’m running 275 PS4s right now.

 

[Cory S]

So your saying don’t worry about the rubber because it won’t do as much? I’m running 275 PS4s right now.

I'm saying...... if you want more grip with your power level now, put a Drag Radial on it. A 305 regular street radial will do nothing over a 275 but corner a bit better.

 

[Ptrug]

I'm saying...... if you want more grip with your power level now, put a Drag Radial on it. A 305 regular street radial will do nothing over a 275 but corner a bit better.

Got it! You think the 555RIIs 275 would still be just as good as 305s? What kind of mileage you get on those?

 

[Cory S]

Got it! You think the 555RIIs 275 would still be just as good as 305s? What kind of mileage you get on those?

Depends on what size wheel, and what look you're after as well. Mileage will vary IMMENSELY.. You could get 10K out of them, or you could get 2000 out of them.

 

[tdstuart]

I'll show you how well my 275/40/19 555Rll's hook at my power level on the street. No different than my 305/45/17 SS's. Wider tires on street asphalt doesn't really do jack but improve cornering. Anything over 650whp should be running a Drag radial anyway.

305s aren’t wide enough. Should be 315+ but not really possible on the car. Doesn’t make a huge difference but helps.

 

[Cory S]

305s aren’t wide enough. Should be 315+ but not really possible on the car. Doesn’t make a huge difference but helps.

We talking DR or street radial? A 315mm PS4 will give you zero straight line traction advantage over a 295-305. I've tested this many times over the past 25 years. Weight is what digs the tread into the asphalt. Going wider can spread out that weight to diminishing returns because the tread can't grip into the surface as well.

My fastest 60-130 was on my 275/40/19 DR's over my 305/45/17's by .12 seconds.

 

[tdstuart]

We talking DR or street radial? A 315mm PS4 will give you zero straight line traction advantage over a 295-305. I've tested this many times over the past 25 years. Weight is what digs the tread into the asphalt. Going wider can spread out that weight to diminishing returns because the tread can't grip into the surface as well.

My fastest 60-130 was on my 275/40/19 DR's over my 305/45/17's by .12 seconds.

Talking street tire. But if you have tested it and seen it doesn’t help, then that is better than my limited experience with it.

I just feel like the 275 width isn’t very wide, and there is a reason corvettes and vipers run such wide tires.

 

[Kennysum1]

Thanks for the reply. I have ps4 275/40 ZR 19 on now so I don't think the tire is the issue. Although I admit I could go bigger but at 800 a pop for the PS4 the gear is cheaper And honestly, I don't think she has that much clearance for a tire that big.

I had her tuned by Lund and my tuner told me that with FI and 3.73, she could hit 7th gear at to high an RPM and could burn the gear out and because of that it would be best to get a taller gear. And people seem to think it's worth it to upgrade to 3.73 on NA cars so I have to believe it will be a big enough difference in the opposite direction.

Bottom line is, with my build as she sits, it to much torque with the 3.73 and while a tire might help, I need a permanent solution to the torque and gear/rpm issue.

So back to, is 3.15 to tall to keep the performance running at about 8 psi

Good luck on your build. I put the G2 in my self, with the larger intercooler so let me know if you need any tips. Hardest part was getting that belt on lol

My full build list.

ESS G2 Supercharger
6PK 120mm Pulley (8PSI)
G3 Spec Intercooler (40% larger)
Summit Racing 50mm Blow Off Valve
FIC 1000 cc Fuel Injectors
Lethal Performane 40v Fuel Pump Booster
Ford Performance 87mm Throttle Body
IMRC Lockouts
Passenger and Driverside Oil Seperator
Resonator Delete with H Pipe
Roush Axel Back Exaust System
Tuned by Lund Racing

Not going to matter what gears you run with those rims and tires. Need some 305/17 inch in the rear. Then just whatever you want in the front to match.

Then proper camber and ensuring your alignment is good is all you can do until you swap over to a proper suspension setup.

 

[NJMike]

Got it! You think the 555RIIs 275 would still be just as good as 305s? What kind of mileage you get on those?

30mm difference between the two tires which is about inch and a quarter. On a drag radial you'll notice.
Is it that you want to keep the stock rims? Will the current rim fit a wider tire?

 

[Cory S]

Talking street tire. But if you have tested it and seen it doesn’t help, then that is better than my limited experience with it.

I just feel like the 275 width isn’t very wide, and there is a reason corvettes and vipers run such wide tires.

Those cars are class racing true sports cars that are road track ready. The whole chassis design is based around handling and tire specifics.

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