Your Boss 302 Top Speed

[Grant 302]

I need to find faster tracks. Funny though my favorite track so far is the slowest, Laguna Seca. Grant what's your top speed at Fontana?

I've only run the GT at Fontana...145+ In the Boss at Laguna, I only had GPS on the car for one session and that was recorded at 112. I thought I saw more than that on a previous session on the speedo and might have tagged the limiter in 4th a couple of times.

 

[pufferfish]

Please pardon my ignorance, but what gear do our cars hit top speed in? I'm guessing 5th, not 6th?

stock tire height, stock 3.73 gears, rev limit at 7500, max speed is 156mph. i believe they are electronically limited to about that. so, technically, no gains in 6th gear. with a tune that eliminates the limiter, who knows, but i can't find a stretch of track to get high enough to find out. i max out at 145 at summit main. i could probably pick up more speed if i could exit turn 10 faster than 75-80 and get more braking power at the end of the straight...ala r compounds. when i do, i will be going to a shorter 18" combo, which drops my max speed in 5th to 150. i think thats plenty fast ;D

 

[Sesshomurai]

Please pardon my ignorance, but what gear do our cars hit top speed in? I'm guessing 5th, not 6th?

stock tire height, stock 3.73 gears, rev limit at 7500, max speed is 156mph. i believe they are electronically limited to about that. so, technically, no gains in 6th gear. with a tune that eliminates the limiter, who knows, but i can't find a stretch of track to get high enough to find out. i max out at 145 at summit main. i could probably pick up more speed if i could exit turn 10 faster than 75-80 and get more braking power at the end of the straight...ala r compounds. when i do, i will be going to a shorter 18" combo, which drops my max speed in 5th to 150. i think thats plenty fast ;D

That's right. 6th is really an overdrive gear (fuel efficiency, less engine load). I can only get to about 132-135 on summit main - primarily because of my turn 10 exit speed (lower than I'd like because of the rear-end lightness I had before (see thread on hard braking issue).

In general, it's kind of a crawl from 60-140 and (for me) there's usually not enough track (pedal to the floor). VIR back stretch is way longer but the faster you go, the slower it is to go faster - with the stock gearbox/diff/torque. Those upgrades coming down the road....

I'm running a steeda CAI tune that removes the speed limiter though....

 

[ls110]

Does removal of the speed limiter let you exceed 7500 rpms, or is it allowing you to exceed at set mph, which I assume is 155?

 

[cloud9]

Does removal of the speed limiter let you exceed 7500 rpms, or is it allowing you to exceed at set mph, which I assume is 155?

Those are actually separate actions. On my GT500, I raised the rev limiter to 6500 from 6250 and eliminated the speed limiter. At BIR I could hit 160 on the front straight even though from the factory the car was speed limited to 155. I hadn't topped out the revs in 5th gear, just my cahonas heading into Turn 1 ;D

 

[ls110]

So if I understand this correctly, and Pufferfish's calculations are correct, to exceed 156 you would need to remove both the rev limiter and the speed limiter. Not that I am going to find a place to exceed 156 as at BIR I am into turn one and just approaching 150.

 

[cloud9]

So if I understand this correctly, and Pufferfish's calculations are correct, to exceed 156 you would need to remove both the rev limiter and the speed limiter. Not that I am going to find a place to exceed 156 as at BIR I am into turn one and just approaching 150.

I've got it calc'd at 161 mph at 7500 RPM using a 26.9" stock tire height, 3.73 gears and 5th gear at 1:1, but you're probably running an 18" track tire that's closer to 26.1? Anyway here's a calculator you can play around with to see:

http://www.wallaceracing.com/calcmph.php

 

[ls110]

I ran the calculator using my 18" wheels and 26.1" Conti tires and it came out at 156.2. Thanks for sharing that calculator!

 

[Sesshomurai]

So if I understand this correctly, and Pufferfish's calculations are correct, to exceed 156 you would need to remove both the rev limiter and the speed limiter. Not that I am going to find a place to exceed 156 as at BIR I am into turn one and just approaching 150.

I've got it calc'd at 161 mph at 7500 RPM using a 26.9" stock tire height, 3.73 gears and 5th gear at 1:1, but you're probably running an 18" track tire that's closer to 26.1? Anyway here's a calculator you can play around with to see:

http://www.wallaceracing.com/calcmph.php

5th gear at 1:1???

 

[cloud9]

So if I understand this correctly, and Pufferfish's calculations are correct, to exceed 156 you would need to remove both the rev limiter and the speed limiter. Not that I am going to find a place to exceed 156 as at BIR I am into turn one and just approaching 150.

I've got it calc'd at 161 mph at 7500 RPM using a 26.9" stock tire height, 3.73 gears and 5th gear at 1:1, but you're probably running an 18" track tire that's closer to 26.1? Anyway here's a calculator you can play around with to see:

http://www.wallaceracing.com/calcmph.php

5th gear at 1:1???

Yep and that's the gear you'll want to use for dyno pulls too. A lot of people assume 4th is 1:1

 

[Tflong24]

I have had mine to 155(speedo indicated) many times. That's about redline in 5th. Without the limiter I do believe the car would pull pretty well past 155 in 6th. I had it in 6th cruising at 145 and with very little throttle application it would start accelerating. I think 170 wouldn't be out of the question. 6th doesn't bog the car at all above 140.

 

[Sesshomurai]

So if I understand this correctly, and Pufferfish's calculations are correct, to exceed 156 you would need to remove both the rev limiter and the speed limiter. Not that I am going to find a place to exceed 156 as at BIR I am into turn one and just approaching 150.

I've got it calc'd at 161 mph at 7500 RPM using a 26.9" stock tire height, 3.73 gears and 5th gear at 1:1, but you're probably running an 18" track tire that's closer to 26.1? Anyway here's a calculator you can play around with to see:

http://www.wallaceracing.com/calcmph.php

5th gear at 1:1???

Yep and that's the gear you'll want to use for dyno pulls too. A lot of people assume 4th is 1:1

Ahhh, yeah, I keep getting it mixed up with the Tremec trans I'm going to put in which is 1:1 in 4th.

 

[pufferfish]

i calculated it by hand using the 775 feet per rev for the 285/35/19 tire listed on tirerack.com

looks like i messed up and used 5680 instead of 5280 for the feet per mile...

7500rpm / 3.73 = 2010.7rpm (tire speed)
2010.7 x 775 = 14736.5 feet per minute
14736.5 / 5280(ft per mile) = 2.79 miles per minute
2.79 x 60 minutes = 167.5mph

there's no effin way i would attempt to do 167 without a slew of aero mods in this mustang! i imagine it would take a lot of tarmac to get there anyhow. the body lines don't exactly scream low drag...the bulldog faced grill in particular.

 

[cloud9]

there's no effin way i would attempt to do 167 without a slew of aero mods in this mustang! i imagine it would take a lot of tarmac to get there anyhow. the body lines don't exactly scream low drag...the bulldog faced grill in particular.

You're definitely shoving a brick through the air ;D

 

[steveespo]

I can see 165 without major aero mods. When I ran 152 at Pocono I was still running street tire so my exit speeds from Turn 1 were much lower than they would be on the slicks I run now and the car was still pulling strong. I also run 3.55 gears which keeps the car at 6250 rpm at 150, 165 would come in at 6900 which is right at peak power for my car. This is with 27" (685mm) tires, I have 665 mm rear tires as well which I plan on using at shorter tighter tracks like Lime Rock or Summit Shenandoah to get my overall gearing similar to 3.73 gears. There ar also 645 mm height slicks available to gear it even lower. I find this an easier way to change gearing than swapping rear gears.
Steve

 

[cloud9]

I can see 165 without major aero mods.

I agree in fact maybe 170 if you had room. I've run my GT500 to 160 at BIR a couple hundred times at least headed into Turn 1 and it didn't feel light at all. I have NO aero mods on it versus the WC splitter, Tiger hood and LS wing on my Boss.

 

[PeteInCT]

Weight = high speed stability ! ;D

 

[cloud9]

Weight = high speed stability ! ;D

Sweet I can run my F-150 up to 180 then ;D

 

[PeteInCT]

Downhill, yes. So I guess that when I trailer the Boss I can have the whole rig at 250 mph or so. No ? :

 

[drano38]

there's no effin way i would attempt to do 167 without a slew of aero mods in this mustang! i imagine it would take a lot of tarmac to get there anyhow. the body lines don't exactly scream low drag...the bulldog faced grill in particular.

You're definitely shoving a brick through the air ;D

Well, the Air Force found out in the '60s and '70s that a brick will fly if you put enough thrust in it . . . the F-4 and F-105 are 2 fine examples--very good fighters, but they were big, and heavy.

Now, back on topic . . .

My top speed was last summer at BIR's long course. Trackmaster and external 5 hz GPS said 145.99 mph--shoulda kept the pedal to the metal just a bit longer