Top speed run. Can this be right?

[exgmguy]

After leaving the Woodward cruise I smoked this LS1 SS on the E-way pretty easily. Then fellow board member FastGTragtop appeared out of nowhere behind us and stepped up to knock him out of the park as well.

Now here is the kicker. I pulled to the outside lane and let those guys start racing from behind me. They came whipping by and I sprayed it in 4th, then into 5th and held it to the mat. I ran 5th gear up to about 5400-5500 rpm. A tad below my shiftlight.
My brakes felt as if they went out. When I slowed down I could smell major burning pads. I figured I was hauling balls, until I plugged my numbers into the analyzer.

5400 rpm in 5th gear on a T-5 car with 28" tires comes out to be about 175 mph!!!!! Can that be right? If it is, I am indeed the STUPIDEST MORAN A$$WIPE on the planet for pulling that move.

Drag springs, 90/10's, and skinnies. Freakin' retard!

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1988 Mustang GT
11.8 @ 123 (7/14/01)
1992 BadAzz Wrangler
1993 Explorer

[Rev]

With your power, I would believe it. What's your axle ratio again?

Rev

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'66 Coupe, 306, 300 HP, C-4, 13.97 e.t., 100.3 mph
1/4 mi.

[dinomite]

YEE-F*CKING-HAW!!!!!!!!!!!!!!!!!!! wow, i think i can believe it. you sure you were in 5th gear?

[Dark_5.0]

Man you are crazy.

I bet that you were going 175mph on the juice.

You have bigger balls than me my friend............

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88 mustang gt convertible bored to 306 BBk equal length headers mac cold air fender kit 3.73 FMS gears cowl hood nitto drag radials ford racing clutch flow masters h-pipe 160* thermostat 16 degrees of timing electric fan off 94' t-bird jacobs electronics cap and wires. Edelbrock 1 1/2 inch drop springs.

[Dark Knight]

I doubt it...the faster you go, the more HP it takes to overcome wind resistance..the resistance at 175 is WAY higher than even 150.. you'd probably pull a higher MPH in 4th than 5th really, you loose torque multiplication in 5th gear..
cant remember the formula off hand...

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84 convt,'95 302,AFR's, performer
3.55's, underdrives BBK shorties
stock cam, 1.7's
13.85@102.5
and a '68 stang that WAS nasty ;-)

[SaleenGTS]

Heck yeah...I believe it. Try the car acceleration program on here. I plugged my numbers in to it to see what my top speed would be. Given my car specs, and aerodynamics, gear ratio, it said I should hit 181. You have a few more mph in the 1/4 than me, so I don't doubt it at all.

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Dustin
89 Saleen GT Sport,428 rwhp,TFS Street Heat Intake,TFS TW Heads,TFS #2 cam,BD-11A 9 psi,Crane 1.6 rr's,BBK 70mm TB,Pro-M 80mm MAF,MSD 6BTM, FMS 9mm wires,BBK longtubes,BBK Short H-pipe,American Thunder cat back,3.55's

12.3@119 street tires

11.496@121.08slicks

[96GTfanatic]

did u remember to calculate wind resistance and resistance from your tires onto the road in the equation? that 175 mph is probobly the speed ur tires would spin at if u lifted the back end off the ground and reved to that rpm in that gear. how much hp do u have? it is possible but unlikely unless u have like 500+ hp

[exgmguy]

I have 3.73's and I was in 5th gear. I am not exactly sure how much power I am making, but I trapped 123 mph last time out with a stinky slipping clutch. At a 3000 lb race weight it should take about 400-420 rwhp to turn that mph. I guess that comes to approximately 500 crank horsepower, or 180 hp at the wheels on a Mustang Dyno. (funny if you read the thread....)

It also did not seem to take too long to get up there either. Hard to judge though when you are all adrenalized in the middle of it.

[smithbling]

Originally posted by 96GTfanatic:
did u remember to calculate wind resistance and resistance from your tires onto the road in the equation? that 175 mph is probobly the speed ur tires would spin at if u lifted the back end off the ground and reved to that rpm in that gear. how much hp do u have? it is possible but unlikely unless u have like 500+ hp

Weight has zero effect on top speed. This means that whether or not the rear tires were lifted from the ground is irrelevant. Based on his calculated top speed at 5400 RPM wind and aerodynamics too are irrelevant. In other words if 5400RPM in 5th=175MPH then when you achieve that you are doing that.

exgmguy

5400 RPM in is what you reached but your speedo only reads somewhere lower. Go out and do 1800RPM in 5th. Record the speed. Say 50MPH. You can simply triple the speed and RPM to get 5400RPM and 150MPH. This works only if you remain in the same gear and it also works because there is a linear relationship between speed and RPM in a given gear. This method is FAAAARRRRRRRR more accurate than the calculators.

For those of you who like calculators try this:

Achieved RPM*Tire/Rim height
-----------------------------------------
Rear gear ratio*Tranny ratio for gear*346

Take this number and decrease it by 7.4%. You will also be very close to your top speed but likely a little optimistic still.

Any questions class?

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88 Notch

MAC Headers, MAC H-pipe, MAC Pullies, KN, and BM Shifter

Best ET: 14.689
Best MPH: 98.54
Best 60': 2.333

[Red514LX]

Rob,

How much did Carl pull him?

Did he tell you about his awesome race w/ a 2001 Cobra 'Vert? (I'm waiting for him to get up off his @ss and post it!!)

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Jeff Kane
1990 LX Mustang Coupe

Very cool. Hard to believe, but I wouldn't doubt it by any means . Must've been a real rush!

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'90 LX 5.0;12K original miles (no sh*&);3.55 gears; March pulleys;Edelbrock Performer Heads;BBK 1 5/8" equal length shorties;MSD 6AL ignition w/ blaster 2 coil;FMS E303 cam;Pro-M 75mm MAF;BBK 70mm TB; Eibach drag-launch spring kit;Southside welded subs;9" K&N cone filter charger;Hurst shifter;Cervini's 3" turbo hood;A/C delete; gutted cats;2 chamber Flomasters;Corbeau racing seats;FMS 30# injectors;JMS chip; Holley 190lb fp;TFS track heat Intake (12.299 @ 113 - 1.78 60')

[jonnyk]

Originally posted by smithbling:


exgmguy

5400 RPM in is what you reached but your speedo only reads somewhere lower. Go out and do 1800RPM in 5th. Record the speed. Say 50MPH. You can simply triple the speed and RPM to get 5400RPM and 150MPH. This works only if you remain in the same gear and it also works because there is a linear relationship between speed and RPM in a given gear. This method is FAAAARRRRRRRR more accurate than the calculators.

The calculators are numerically based. Your speedo is not always accurate especially if you have changed gear or tire heights. Therefore, I would say the calculators are FAAAARRRRRRRR more accurate than "guesstimating" using a crappy stock speedo setup. If that 5400 rpm reading came from an aftermarket tach, then 5400 in 5th gear (0.68) with 3.73 gears and a 28" tire = 177.32 mph. I have created a nice little spreadsheet that calculates this.
The formula I used is:
RPM / (rear gear * tranny gear)*60*(tire circumference in inches) / 5280 / 12


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'91 LX Hatch, 17 ROH ZR6's, lowered, 3.73's, offroad H pipe, SN Cobra cat-back, ASP pullies, 14° timing, C&L 76mm MAF, 170A 3G, B&M Ripper on a T5
Best ET: 14.593 @ 94.62 2.292 60'
1991 LX Hatch 5.0L

[Stang Runner]

WOW 175MPH Cool.


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14.62@96.9 Engine: Steal Mounts, Under drive pulleys, K&N, Home ported Lower Intake, No power steering, No A/C
Drive Train: 3.55, World Class T-5,
NOW it is time for Real power STUFF I Have and will put on after I get everthing: Accel DFIMac cold intake, 70MM TB, Valve covers (COOL ONES)255 Fuel pump.
Next to get: rocker arms,Cam,TFS Heads,Injectors 26,Holley intake, What might I need???

[jimberg]

Originally posted by smithbling:
This method is FAAAARRRRRRRR more accurate than the calculators.

I can't agree with this statement at all. Your method of calculation through experimentation makes the assumption that the speedometer is correct. If it's not, the amount of error will also double or triple along with the velocity you're multiplying.

Using a calculator is the only way to do it accurately. If exgmguy really wants to know, he can take a tape measure and measure the diameter of his tire. I say this since measuring the height of the tire would be more difficult to do accurately and the size numbers of the tire are probably not correct anymore because they are worn.

Assuming that the tachometer is correct (which I do since it is an expensive one that is designed to be accurate), use this formula (It's essentially the same as yours):

Achieved RPM X Tire Diameter
-----------------------------
Trans Gear Ratio X Axle Gear Ratio X 1056

The 346 in your equation should be a 336 (1056/PI). The 1056 is the number of inches in a mile divided by 60.

Also, just for anyone who cares, if you must go by the size on the tire, you can figure tire/rim height in smithbling's equation with this formula:

(Aspect Ratio * Width)/1270 + Rim Height

Like I said, though, that assumes a tire with no wear. Oh, aspect ratio should not be converted to a percent for this equation to work. That's handled by the 1270 which is just the conversion factor for milimeters to inches multiplied by 50. It's 50 instead of 100 so that you don't have to multiply by two for the top and bottom of tire.

I would like to know why you said to decrease the result by 7.4%, smithbling.

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351W 89 Mustang GT Convertible

[jonnyk]

Originally posted by jimberg:
Like I said, though, that assumes a tire with no wear.

And also a tire that is inflated to it's correct level, and assuming there is no expansion at such a speed. Lots of factors...just easier to ballpark it



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'91 LX Hatch, 17 ROH ZR6's, lowered, 3.73's, offroad H pipe, SN Cobra cat-back, ASP pullies, 14° timing, C&L 76mm MAF, 170A 3G, B&M Ripper on a T5
Best ET: 14.593 @ 94.62 2.292 60'
1991 LX Hatch 5.0L