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top speed of a 3L hybrid with headers and no cats? (on a track of course)

KyleQ said:
Huh - I've got a Taurus PCM setup for a 3L with a top speed limited @ 200mph - just a rough tune to get it to run :cool:

Couldn't one find out the absolute top speed just be using the gear ratio's in the transmission? That is the absolute limiting factor - no HP. When you get tuned, they almost always "adjust" the top speed being it is as easy as editing a text box...
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NO. The limitation is not gear ratio. It is POWER. Sometimes lowering the gear ratio will raise top speed.

As someone else mentioned, the additional power needed to even gain one more MPG is considerable. It is a logarithmic function. A 20% increase in power will not provide a 20% increase in speed.

Now if you were racing in a vacuum with no atmosphere to create interference that would be a different story.

My SWAG remains at 150 MPH. 160 MPH with forced induction. 200 MPH would take a HUGE increase in cylinder displacement as well.
 
Big Jim said:
NO. The limitation is not gear ratio. It is POWER. Sometimes lowering the gear ratio will raise top speed.

As someone else mentioned, the additional power needed to even gain one more MPG is considerable. It is a logarithmic function. A 20% increase in power will not provide a 20% increase in speed.

Now if you were racing in a vacuum with no atmosphere to create interference that would be a different story.

My SWAG remains at 150 MPH. 160 MPH with forced induction. 200 MPH would take a HUGE increase in cylinder displacement as well.
Click to expand...


All I'm saying is that you are limited by gear ratio - I'm not talking about wind resistance, track length - you motor will find an absoulte peak rpm and stay there (removed rev limiter and all) Sure with more power you can go faster - think about it - your motor wont make it past 10K RPM - with gears, you can obtain any speed - as long as your car can push it's own weight that fast...
 
KyleQ said:
you motor will find an absoulte peak rpm and stay there (removed rev limiter and all) Sure with more power you can go faster - think about it - your motor wont make it past 10K RPM
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I think your motor throw a rod before you find this "peak rpm" even if it's slowly pulling past 8k rpms I don't forsee it lasting long :laugh: You can run out of gears... but it's not going to happen with an NA 3L thats for sure.
 
With FI, your guess is 160?

That is attainable.. with a FI'ed 3L... trust me
 
KyleQ said:
All I'm saying is that you are limited by gear ratio - I'm not talking about wind resistance, track length - you motor will find an absoulte peak rpm and stay there (removed rev limiter and all) Sure with more power you can go faster - think about it - your motor wont make it past 10K RPM - with gears, you can obtain any speed - as long as your car can push it's own weight that fast...
Click to expand...

Trust me. Gear ratio is not your limitation. Additional horsepower is needed to pull taller gears. Horsepower is the limitation.
 
Look, as you can all see there are three right answer to the top speed limitations.

1. One is a speed limiter...but SVTs don't have a speed limiter so forget that one.
2. Two is a rev limiter. You hit the rev limiter in your top gear and you aren't going any faster.

3. Three is a power limiter. Lets say you have tall gears, no speed limiter, and no rev limiter, but you just don't have enough power to go any faster through the wind resistance. This is also known as drag limited in cars. That is the case of the stock SVT and mos likely the NA 3L engines with even a stock rev-limit left in place.

With a boosted contour you will hit the stock rev limiter in 5th gear ~161mph with 235/45-17s at 6750rpm...well a powerful 2.5L or a 3L boosted contour that is.

Then lets say you remove the rev limiter entirely and the contour can then pull say 8000rpm for a short time before you blow a rod or overheat the pistons and melt them. That is 192mph@8000rpm in 5th gear and 235/45-17s. And that is on the stock 4.06:1 gear ratio.
None of our cars can pull that on any possible street-trim engines.
So in the last case you will be drag limited to the 160s, I'd guess about 168-170mph with a 400hp 3L turbo.
 
Tom, just out of curiosity, plug the zetec final drive with 235/45/17's into your charts and figure out how fast at 7000 rpm a Contour would be moving. :) I am quite curious.
 
Big Jim said:
NO. The limitation is not gear ratio. It is POWER. Sometimes lowering the gear ratio will raise top speed.

As someone else mentioned, the additional power needed to even gain one more MPG is considerable. It is a logarithmic function. A 20% increase in power will not provide a 20% increase in speed.

Now if you were racing in a vacuum with no atmosphere to create interference that would be a different story.

My SWAG remains at 150 MPH. 160 MPH with forced induction. 200 MPH would take a HUGE increase in cylinder displacement as well.
Click to expand...

All very interesting.

So my 170hp Mystique ATX Ford says has a top speed of 168mph, then with 240hp or so from a 3L I should approach 200mph or crack the sound barrier or sup'm, right??

:laugh: Just bein' funny.
 
Big Jim said:
Are you going to tell us what you were on when you took that trip?
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lol,
I DIDN"T go 204mph, I responded to his question about theoretical top speed through calculations of ties sizes and gear ratios. I put together a spreadsheet that does the work by putting in the relevant information.
The zetect FD with an 8000rpm engine and 235/45-17 tires can do 204mph if it had unlimited engine power.
 
Where is that spreadsheet tom? I saw it awhile ago, and I would like to check out some stuff and change some values around if you don't mind posting a link. ;)
 
155mph! what engine mods do you have?

the track thing is a joke i just didnt want to get **** for speeding on the highway dangerously. i went 140mph before i removed my cat and and put on the cherry bomb actually on the way to do the exhaust but i got cut off so i had to slow down.

i would definetly think top speed of around 155 though, she had some left.
 
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