SGT/SC Top end

[AstroDan]

Maybe someone can help me. If you install a SC into the SGT, what difference is there in the top end speed. I would assume that you'll run out of tach before you run out of acceleration....

I've had my non-SC at @125 mph at @ 3600rpm (on the track, of course :D )and think I would run out of tach around 150-155mph...

Comments?

 

Dan

 

http://i259.photobucket.com/albums/hh299/AstroDan/004.jpg

[LuLu]

Maybe someone can help me. If you install a SC into the SGT, what difference is there in the top end speed. I would assume that you'll run out of tach before you run out of acceleration....

I've had my non-SC at @125 mph at @ 3600rpm (on the track, of course :D )and think I would run out of tach around 150-155mph...

Comments?

 

Dan

 

http://i259.photobucket.com/albums/hh299/AstroDan/004.jpg

 

I buried the speedo on the way home from the dealership, and only 45 miles into ownership. Can't prove it right now, but it happened. I figured that it's going to break, best to happen ASAP, right?

 

SC or not, the redline on our engines is 6200 RPM. After that, you're toast.

 

I need to get some new add-on gauges that record this data to my notebook.

[04Retro]

Unles the Shelby/Ford Racing chip reprograming changed it the car is electronically limited to 150 give or take (some say 149 others say Ford has it at 151 etc -- and yes some brag that their speedos showed higher--understand that at that speed the speedo itsn't accurate to 1 mph)) regardless of blower or not (rear end heads towards the world of unstable above that speed).

[69dejavue]

In theory, and practice, the top speed will be the same assuming the same number of rpms. The speed is determined by the diameter of the rear tire, the differential ratio (3.55 standard on the SGT) and rpms.

 

if you have two SGTs, one normally aspirated and one supercharged, both with identical tires, transmission gears, rear end ratio, and both turning the same number of rpms, they will be travelling the same speed.

 

The actual formula is MPH = rpm x tire diameter

gear ratio x 336

 

 

The only effect the super charger will yield is getting to the top speed quicker. We are limited by a chip and the physical limitations of our drivetrain. We do not have lightweight pistons, forged rods, forged crank, lightweight flywheel, and most importantly, improved valve train and springs. Thank God we have a limiter or too many of us, myself included, would push the actual red line and beyond until things inside the motor break.

 

Oh yeah, the super charger sounds better at full throttle!

 

re the red line the vehicles are supposed to have a rev limiter that will limit us to about 6200 rpm. we shouldn't be able to exceed that limit no matter what internal modifications we make unless we make changes to the computer.

 

I have thought about a SC but once you get to top speed you are at top speed. The super charger will not increase the top speed. Just get you there quicker.

 

I also had mine near buried, about 142+ and this was verified by a GPS system. Had to do it at least once.

[SGT2666]

I calculate that we're geared for well over 200 mph is that correct ? I'd be interested to see what a blown car can pull, I'd expect 170 180 range. This is what I put together quick not sure if its correct.

 

.062 final drive

3.55 gear ratio

83.98 tire circumference

6200 red line

 

6200 / .062 = 10,000 driveline speed

10000 / 3.55 = 2817 Axle speed

2817 * 83.98 = 236571.66

236571.66 / 12 = 19714.305 feet per minute

19714.305 * 60 = 1182858.3 feet per hour

1182858.3 / 5280 = 224 miles per hour

[ShelbyPilot]

Has anybody seen a posted top speed of a stock GT500. Most of us with blown cars are around the same 500. Only a few hundred pounds lighter shouldn't make that big of a deal on the top end. Aren't aerodynamics playing a huge role at those high speeds.

 

EDIT: Ok, after reading 07SGT's comments which make perfect sense maybe the GT500 comparisson won't work. They have a smaller gear (stock).

 

I also had mine near buried, about 142+ and this was verified by a GPS system. Had to do it at least once.

 

 

Were you at the red line or rev limiter?

[04Retro]

Sorry guys-- AREO plays a huge part (Mustang = brick, Ford GT = aero slippery but even with 550 hp it could bearly break 200)---even with a blower you do not have the HP to pull redline rpms in 5th gear..the math above is just pure math but leaves out road friction (on the tires) aero and the general laws of physics--the blunt non-aero nose pushing air out of the way etc.

 

Yes if you cancel the speed limiter in the chip and ignore the basic aero package of the car in which you will lose rear end stability above 150s and crash (and kill yourself - that huge tall wing on the 2000 Cobra R actaully served a prupose)..the SC car with more HP will go faster then the normally asperated car - but your only talking about 5-10 mph tops.

 

A non-Ford world example. C 6 Corvette Coupe at 400 hp hits 186. The Z06 versin at 505 hp hits 198. 25% more HP, going from 400 to 505 only gains 12 mph. And the drag coefficient on that Vette is mles beyond that of a Mustang. I'll even give a reverse example. A 2004 C5 Corvette Coupe -long glass back- at 350 HP tops out at 174. A 2004 C5 Z06 at 405 hp (underrated)..tops out at only 172. The reason being the longback copue plays better as far as top end Aero then the 'hardtop' samll top Z06. 55+ less hp but he Coupe has better top end aero and thus a slighlty higher top end.

 

[

 

I calculate that we're geared for well over 200 mph is that correct ? I'd be interested to see what a blown car can pull, I'd expect 170 180 range. This is what I put together quick not sure if its correct.

 

.062 final drive

3.55 gear ratio

83.98 tire circumference

6200 red line

 

6200 / .062 = 10,000 driveline speed

10000 / 3.55 = 2817 Axle speed

2817 * 83.98 = 236571.66

236571.66 / 12 = 19714.305 feet per minute

19714.305 * 60 = 1182858.3 feet per hour

1182858.3 / 5280 = 224 miles per hour

 

 

Correct if your running in a vacum or outerspace...sorry your leaving the atmosphere and gravity out of the equation -- but great work!!!

[mccoystudio_merged]

Guessing about 150 after I passed the 140 on the speedo.....149 or 151 I don't know I did not notice any unstability and did not crash obviously. I am calling it 150. BTW not on a public roadway...so do not flame me. No s/c currently on my car.

[ilmor]

I read a magazine test report once that said the top speed of the SGT (non-S/C) is 150. I guess I'll have to take their word for it!

[LuLu]

We do not have lightweight pistons, forged rods, forged crank, lightweight flywheel, and most importantly, improved valve train and springs.

I'm not sure exactly what you mean here, but I'll work with it because you're mostly right.

 

The stock SGT 4.6L-3V internals are much lighter and more flexible than any aftermarket rotating mass. Lighter is good, flexible is not. Step up to a steel forged crank, aluminum forged rods and pistons, stronger valve train, ect., and like any body builder, while you gain strength, you end up with a weight problem to deal with. This upgrade stuff is heavier and consumes twice as much energy in rotation than the stock components.

 

While this seems counterproductive to achieving top speed, or, building power, it's not. It's just that stock components won't take such abuse very often, or, stay together very long. After 6200 RPMs, the stock engine will come apart, and a built engine will do okay through 6500 RPMs more often, but that's it. You're done, you have reached your limit either way.

 

By improving internals, you gain strength and can pump the boost (or, add juice) to overcome this initial loss due to heavier components, and stay together. But, it remains true that if you like high speed (120+ MPH) that much on a regular basis, you bought the wrong car. The 4.6L is a "square" design, 3.55 bore by 3.54 stroke, thus it will rotate only so fast. When you reach this limit, remember to ask for a flat-bed.

 

I hit my top end just once, and I felt more limited by the quality of the road than anything else. I may like to go fast, but there seems no place to drive fast anymore. Best road I ever drove is still I-65 in Indiana, between Merriville and Indy. That road is "born to be wild" flat, open, and clean. The Ohio Turnpike (I-80) is second best on my list.

In theory, and practice, the top speed will be the same assuming the same number of rpms. The speed is determined by the diameter of the rear tire, the differential ratio (3.55 standard on the SGT) and rpms.

 

if you have two SGTs, one normally aspirated and one supercharged, both with identical tires, transmission gears, rear end ratio, and both turning the same number of rpms, they will be travelling the same speed.

 

The only effect the super charger will yield is getting to the top speed quicker. We are limited by a chip and the physical limitations of our drivetrain.

 

re the red line the vehicles are supposed to have a rev limiter that will limit us to about 6200 rpm. we shouldn't be able to exceed that limit no matter what internal modifications we make unless we make changes to the computer.

 

I have thought about a SC but once you get to top speed you are at top speed. The super charger will not increase the top speed. Just get you there quicker.

Very true. Supercharging doesn't change your maximum speed, it just gets you there sooner.

 

At lower speeds, my rev limiter seems closer to 5800 RPM, but I fully agree with your point. As it was pointed out here in another post, it's hard to dice up exactly what's going on at these speeds (RPM and MPH) and know exactly what's happening. We may be off by a few hundred RPMs, or, a few MPHs, but what's the difference? Either way, it's fast!, and not for the faint of heart.

 

Kids...Please don't try this at home?

[LuLu]

I calculate that we're geared for well over 200 mph is that correct ? I'd be interested to see what a blown car can pull, I'd expect 170 180 range. This is what I put together quick not sure if its correct.

 

.062 final drive

3.55 gear ratio

83.98 tire circumference

6200 red line

 

6200 / .062 = 10,000 driveline speed

10000 / 3.55 = 2817 Axle speed

2817 * 83.98 = 236571.66

236571.66 / 12 = 19714.305 feet per minute

19714.305 * 60 = 1182858.3 feet per hour

1182858.3 / 5280 = 224 miles per hour

 

Looks good on paper, eh?

[stump_breaker]

I'm in agreement with the aerodynamics. At ~130 the car seems to hit a wall on a N/A engine. It struggled to get to 140 but could keep going. I can only suspect with the SC it can push through this hurdle with ease.

[SGT2666]

Sorry guys-- AREO plays a huge part (Mustang = brick, Ford GT = aero slippery but even with 550 hp it could bearly break 200)---even with a blower you do not have the HP to pull redline rpms in 5th gear..the math above is just pure math but leaves out road friction (on the tires) aero and the general laws of physics--the blunt non-aero nose pushing air out of the way etc.

 

Yes if you cancel the speed limiter in the chip and ignore the basic aero package of the car in which you will lose rear end stability above 150s and crash (and kill yourself - that huge tall wing on the 2000 Cobra R actaully served a prupose)..the SC car with more HP will go faster then the normally asperated car - but your only talking about 5-10 mph tops.

 

A non-Ford world example. C 6 Corvette Coupe at 400 hp hits 186. The Z06 versin at 505 hp hits 198. 25% more HP, going from 400 to 505 only gains 12 mph. And the drag coefficient on that Vette is mles beyond that of a Mustang. I'll even give a reverse example. A 2004 C5 Corvette Coupe -long glass back- at 350 HP tops out at 174. A 2004 C5 Z06 at 405 hp (underrated)..tops out at only 172. The reason being the longback copue plays better as far as top end Aero then the 'hardtop' samll top Z06. 55+ less hp but he Coupe has better top end aero and thus a slighlty higher top end.

 

[

Correct if your running in a vacum or outerspace...sorry your leaving the atmosphere and gravity out of the equation -- but great work!!!

 

 

You shouldn't skip to the end you miss important info i know you won't go that fast I just wanted to see if gears were a lmitation and it doesn't appear so. The blown cars have plenty of HP but I don't know what the drag coefficient is for our cars.

[AstroDan]

All good points.

So, with an automatic and it's higher final gear, a higher top end is achievable?

I was on I-5 North of Bakersfield. Shoulda pushed all the way just to feel it myself. At 125 I felt like I could take my hands off the wheel and if I stomped on it, it would still have put me back in my seat. Any way you slice it, these cars are fun at 40-80-or 120!

My buddy let me drive his 05 LS3 (I think) Vette the other day. Definitely way more power than my NA Ford. Very nice car, but it felt like a passenger car compared to my Betsy. At 90, I had ahold of it like I would my Ram pickup. Maybe this is cuz it's not my car, but I would choose my NA Shelby over this $50k+ car any day.

IMHO a SGT/SC with like 440 RWHP would eat that Vette. :D

Dan