I was just at another site and it said that with 25.7 " diameter tire (275/40/17) with a ZF 6 speed, if you hit like 4300 RPM in 6th gear, you would hit 200 MPH.

Has anyone ever hit 4300 RPM in 6th gear, and how fast were you going?

Anyone ever try hitting nitrous in 6th gear for a little boost? What would hitting nitrous in 6th gear do? Damage? Too hard on drivetrain?

 

Your assuming you'd have enough power to do so, stock not even close.

 

Even with my stock 2.59 rear gears it would take 5,000rpm to hit 200mph in the .70:1 4th gear.

What is your 6th gear reatio and rear gears?

 

I read somewhere, or heard somewhere that the HP needed just to go up an extra 1 mph or so past a certain point has to be cubed.

In other words it might only take you like 250hp to reach 165mph, but it would take you 500hp to reach 200mhp, and if you wanted do reach like 210mph it would take you like 1000hp.

I'm just giving an example, but that's honestly how it works.
I'm guessing its possible to reach 200mph at 4300rmp in 6th gear, but you would need A LOT of hp.

 

I would say I'm not close to stock in performance terms.

The ZF 6 speed gears are..

1st is 2.68
2nd is 1.80
3rd is 1.30
4th is 1.00
5th is 0.75
6th is 0.50

I'm pretty sure that is very close to the actual gear ratios.
I have a 3.33:1 rear gear ratio.

How much hp would it take? I've heard from between 550 and 600 hp.
A 400 hp motor with a 150 nitrous kick would put it somewhere close. But I am not sure about the stress it would put on the drivetrain to use nitrous in 6th.

Anyone know of possible drivetrain problems?

 

A stock LT4 coupe will go about 170mph and they dyno at about 350 hp flywheel hp.

Power required is about proportional to the cube of the speed.

200 hp will take about 570 hp. Actually a bit less because part of the drag is rolling resistance and that doen't go up with the cube. But more than 540hp.

 

Just want to know. But I don't think I am brave enough to do it top speed on my supercharged 383LT1 around 700rwhp 3.45 gear ZF6 speed
at 5th gear and 6000rpm will it pass 200mph?? just curious


Bruce

 

I got close once on the dyno :lol:



KM

 

So, a 400 hp motor spraying 150 could do it or come real close? :confused:

 

Callaways Sledgehammer hit 254mph with around 900hp. Lingenfelter did 220mph in a 415cid ZR-1 (approx 650hp). Stock ZR-1's are good for 180mph with 375-405hp. Based on this I'd say it would take around 500-550hp to hit the 200 mark. The trick is the car must be geared so that max hp and max speed occur at the same point.

 

My STOCK 1997 Trans Am (A4) went 165mph+ (speedo stopped at 165mph, we're guessing I let off around 175mph according to other cars flooring it around us and how it slowly crept up at the end) and was still pushing but SLOWLY, also I have NO idea what the stock gears were, I'm guessing the 2.73-2.97 whichever it was that year. I also ran a 14.1 @ 98mph in a stock LT1 Trans Am which SOME people think is crazy for around here, who knows, maybe it was a factory freak. Not even trying to bullpoopie you guys, had about 5 friends there. Also passed another friend who was in a Dakota R/T on the road when I pushed it the longest, we flew by him, he said it seemed like he was standing still (he was going over 100mph) I didn't expect that much out of a rated 285 stock hp, but it did it. I don't think my C4 would get there as fast as the t/a did, I think my C4's only good for around 155-165mph, safely anyway. I've never gone above 145mph so far in the C4 and it had a LOT left in it, not a lot as in to 180, but a lot as in to 160mph pretty easily, but due to balancing and some loose stuff when I first got the car, it was shaking like CRAZY! That was before any mods as well, I'm pushing roughly 263rwhp right now. Those are some decent examples, but I'm not sure how they fit into your calculations.

Don't know if those mph's help any, but maybe they'll lead you to figure out exactly how much you need :confused: :cheers:

 

What would you consider optimal gearing then?

5th gear in ZF 6 speed is 0.75:1
6th gear in ZF 6 speed is 0.50:1
My rear gear is 3.33:1

I've heard that top speeds will always be reached in 5th.
Since I've only taken mine over 6000 on occassion, I'd be doing 184 MPH at 6000 RPM, if it would do 6K in 5th which I doubt somewhat. That is why I was asking about 6th gear top speeds.

 

Blah.. a stock 300 (+-30hp) will be limited to the 170mph range(+-5mph).

It takes mucho horsepower (around 600hp) to push a stock Vette past 200mph.

Reference this link...
http://www.caranddriver.com/article....&page_number=1

 

To find your cars optimal gearing you'll need to do some dyno runs to see at what rpm your engines peak horsepower falls at. I have heard of people topping out in sixth but these cars are running steeper rear gears (4.10 and such) with a lot of horsepower. There is a speed in gears calcuator on the internet somewhere which you can use to play with gear ratios and tire sizes. Cant remember where it is right now but I think it was an F body site. Maybe someone here knows where to find it. Your info on 4300rpm in six being 200mph is probably close to the mark given your 3.33 rear gearing. The problem is that you'd have to be making 550hp or so at only 4300rpm to actually see 200mph. Just a guess but I'd say your engine is probably spinning faster than this at peak.




[Modified by locobob, 12:26 AM 2/14/2004]

 

:bs

A stock LT1 Trans Am will not do 175 mph. Proven in every magazine test of that type of car. Either your speedo is off and/or nonstock tires sizes. 160 mph is more like it, sorry.

Gearing: I believe all topenders are running in 5th and using rear gearing to maximize the mph. 6th gear is a double overdrive and and gasoline engine won't make the kind of power to push 200 mph in a C4. Folks have used deep rear gears (~4.56's) in ZR1's to raise the rpm and the car still wouldn't pull past what the OEM gearing in 5th was (3.45 rear gears) not to mention the driveshaft speed at that gearing/speed!

I'm sold on the fact you will need to use 5th and gear accordingly. Calculated, my car will hit 200 mph at 6800 rpm in 5th (ZF, 275 rear tires, 3.45 gears). Mine will be naturally aspirated so RPM is the name of the game. While you could lower that rpm (and use lower numerical rear gears) by using a supercharger-I would expect.

Bottomline: the car will need some serious solid power with gearing optimized just right or it come close.

Good calculator to play with some numbers:
http://www.f-body.org/gears/


[Modified by No Go, 5:45 AM 2/14/2004]

 

:iagree:

I even recall a Road & Track top speed test where a Rippie ZR1 DRM 500 couldn't pull sixth at the Firestone test centre with 4.09 gears. 5th is the top end gear in my opinion.

edit I recall at least a year ago one of the guys who posted in the ZR1 section was aiming for 200mph in sixth gear in his Callaway TT - I don't recall if he ever acheived his objective though - he doesn't post here anymore unfortunately. I think he did at least get close FWIW.


[Modified by Red 90 L98 Coupe, 1:54 AM 2/15/2004]

 

6th gear (.5) is steep in the ZF, drops the car too far off the power band. I've tried to drop into 6th at 150-160 MPH, car won't accelerate and begins to heat up, strains the clutch also. I can cruise along at the speed achieved in 5th but cannot accelerate.

Heard Rick Doria asked Bill Boudreau to manufacture a lower (.65-.7) sixth gear but Bill claims it was too expensive and one was never produced?

 

Car was completely stock, including tire size. I assumed at least one guy would call a bullpoopie flag, but fact remains it did it. Once again, my speedo also stops at 165, we estimated about 10mph more because of other cars around us (a viper and a few ricers and according to where they topped out). Car also shifted, I'm guessing into overdrive at 135-140mph, which jumped it ahead a little more. You don't have to believe me, but we did it and it was one of the funnest times I had in that car plus we have about 5 people that where there, 1 of them was in the car too. :seeya I bet there was also never a magazine in the world that said a stock LT1 vette was capable of sub 13.2s, and I believe forum members have proved that wrong.


[Modified by BowTieBlood, 1:03 PM 2/14/2004]

 

Yea, no stock engine would be able to handle that. You would almost have to have a completley remanufactered performance spec engine with a larger bore and such. Even with all that and some nitrous i wouldnt risk my car trying to hit 200. However if your looking to hit 200. Go to this site its open road racing and if you have the requirements they will allow you to attempt 200mph. so go to this site. http://www.OpenRoadRacing.com :cheers:

 

Most of us believe you believe you did it, but that doesn't mean you actually did it. Speedometers lie a lot.