redline?

[faster_than_u]

hey

i was wondering what the redline was on the focus, also when does it hit the revlimiter? also what is your favorite rpm to shift at when racing? thanx guys

[QQQQ]

I take mine to the limiter when racing as that is how I have achieved my fastest times.I don't have a tach,but I have read the factory limiter is around 6.8k.My Xcal2 bumped it to 7.4k(like I requested).Once I install my pwsc I plan on a shift light install.Mabye a tach some day,but I don't watch it anyway...

[fokuzx3]

on a standard zetec...even with stg. 1 cams or stg 2 cams like fr and comp you wont see any power gains after 6k if that...my advice is to shift right after 6k, power shifting will make you hit the rev limiter and catch back right above 4k...watch the beginning of this vid...http://videos.streetfire.net/search/...334064bfd4.htm

[Pkmgarf]

Well, my ATX shifts at about 6.5K or maybe a little higher when at WOT. But, the above post is 100% correct, anything after 6K or so is just a lot of spinning and not more power...

[hEaT]

I shift at 5500. Limiter kicks in around 6750 I believe.

[tweakfreak88]

Stock Zetec internals are good until 7500RPM at which the oil pump gives way. The stock springs are actually much stronger that what most people think.

Concerning the shifting issue...

Most folks shift far to early here on the forums and do not take advantage of "Mechanical Advantage". The transmission multiples the torque to the ground thats made by the engine. As you upshift that multiplication factor decreases every time putting less torque to the ground. The HP curve is actually irrelevant(for the most part) when determining the shift points on an engine. Here is an example Bolt-on Zetec Dyno:



What you want to observe is the torque curve. Granted it does start to fall fairly quickly after 5000 RPM, but that doesn't mean thats where one should shift gears.

These are the stock ratios of MTX-75 trans compounded w/ the final drive for the first 4 gears(5spd in the Focus)
12.75:1 first gear ratio
7.98:1 second gear ratio
5.40:1 third gear ratio
3.84:1 fourth gear ratio

(based on the graph above)
As suggested above if you should shift at 5500RPM you would be exiting 1st gear with (125ft-lbs*12.75)1593 ft-lbs. of torque to the ground. You would enter 2nd gear around 3700RPMs and applying (121ft-lbs*7.98)965lbs of torque to the ground which is considerably less then the previous gear. The objective when determining to shift is to be able to apply the most amount of torque to the ground throughout the entire 1/4 mile.

Lets change are shift point to 7000RPM. At 7000RPM in 1st gear you would be exiting the gear with appox. (85ft-lbs*12.75)1083 ft-lbs of torque. Entry to 2nd gear would be around 4600RPM and would be applying (128ft-lbs*7.98) 1021 ft-lbs of torque to the ground. Thats much more then 965lbs of torque.

I know this looks complicated but the basic objective is to have same amount of torque to the ground exiting a gear as entering into the next which applys the most amount of torque over the period of the acceleration. It's pure physics folks, this car will accelerate faster shifting high(7000RPM) even a Zetec close to stock form, the 1-2 gear is 7k for optimal acceleration. Each gear as you calculate the RPM drop the shift point will be a little bit lower each time because the ratio difference isn't as significant.

So in a nutshell

1-2, shift at 7k
2-3, shift around 6800rpm
3-4, shift around 6700rpm

If anyone has questions please don't refrain from asking.

For more information on how compounding gearing works look here.

http://www-education.rec.ri.cmu.edu/...edia/cgr.shtml

-Tweak

[QQQQ]

Gee,I guess that's why my best times are when I shift almost at redline.Thanks tweakfreak88 for the reasoning behind it!I always wonder why I win most races against other Foci owners.Then again,they probably aren't really racing...

[tweakfreak88]

Mind you the shift points I stated above for each are for folks that are N/A w/ stock internals(cams etc.). With a full length header i'd prolly add a bit more, but if you really want to know what you optimal shift point is then you have to dyno your car and see where your torque curve is at.

[tsmitty025]

6750 is the correct number for redlining... how hard is it on an engine when you redline???

[RhodySVT]

Running an engine to its rated redline as long as its well maintained is no problem. Running constantly at redline causes premature wear of the rotating assembly. Bouncing a car off a hard rev-limiter can cause wear to the timing system or cause it to jump timing which would hurt the engine. But running it up to redline, shifting, up to redline again etc. will not harm the vehicle in moderation.

[jfocus69]

dam man, you are the new numbers guru........cuz i shift high anyway
..........ooooohhhhhhhh i just copied your chart!!!!! lol

[tweakfreak88]

Based on that dyno above and factoring inertia(when shifting gears), I figured these shift points.

1-2@7400
2-3@7000
3-4@6700

I don't recommend these exact points for other bolt-on's Zetec engines because the torque curves differ slightly based on cam timing etc. You really need to dyno your car to see what your torque curve looks like. For most factory cars however shifting a tad before the rev limiter in 1-2 shift is usually optimal and sometimes even for 2-3.