Sorta hypathetical question; if i was to take say a standard zetec engine from a Focus how do you go about making it safely rev to 9000rpm+ weak points/concerns?

CJ

 

remove the rev limit lol.

lots things affect rev limits, like pistons, rods, crank, valves, valve springs, lifters etc etc etc

 

As Dan said - many things mate... Rodbolts, crank and the head are the main places to look...

Cam durations and lifters/springs need all to work together

 

Raising the rev limit often requires bigger injectors.

This is because, the higher the revs, the shorter the time you have
to squirt the fuel in so the injectors need to be bigger as they will put
more fuel in for less time.

Generally, unless the injectors are on the limit, you can get away with
about an extra 300 - 500 rpm with changing them providing the
ecu rev limit is removed and the maps are adjusted to suit above
the original rev limit.

 

Changes also required to breather system, oil system, ecu, clutch and gearbox as well

 

Simon - just out of curiousity - if the rev limit was say raised by 2000rpm, i imagine the standard management would have run out of load sites for that?

Can the standard management load sites be re-done at say 600rpm intervals instead of 500rpm to allow a greater range but without changing the number of load sites?

 

Big Will 85,
Yes, even on factory ecu's depending on the skill of the mapper.

 

Things to consider for strength:

Block itself not letting the crank loose from the mains (in some cases you need to strap them or run a girdle)

Rod bolts are under ENORMOUS extra strain at the end of the exhaust stroke at very high RPM and normally are the first thing to be needed

Rods themselves may stretch

Valve springs may not be able to shut the valves quick enough

Oil pump may start to cavitate and not work properly, same for water pump, and alternator may not be able to hand it and need an underdriven pulley



Things to make it worth revving that hard, As Simon briefly mentioned, you have a shortened induction stroke timebase to work with for each cycle, so consequently you need to do things in order to maiximise the VE of the engine, such as:

Larger ports in the head / better inlet (eg ITB's)

Hotter cam with both more duration and more lift

Higher CR to actually maximise the torque from the underfilled cylinder

Larger valves to increase the breathing effiency





so basically, you are hardly going to have anything you dont have to modify at massive rpm like 9000+ on most engines.

 

it's very easy - throw out the shitty ford engine and drop in a honda one

 

LOL @ Nick, fair point though.


Integra Type R engines etc even have solid lifters as standard

 

So does my fiesta zetec and my 16i did too

 

At least they have ONE redeeming feature then despite all evidence to the contrary

 

Git

 

PMSL @ your signature site

 

Say if needed to uprate the crank and rods any point in changing the stroke too?

 

Making the stroke SHORTER will make it rev harder generally, but will result in less torque too, so it depends on what you are trying to do.

Often shorter strokes only exist in order to allow more valve area (bigger bore) for the same capacity, like a 970cc mini for example which is MUCH bigger bore than a 998cc mini despite them both being nominally 1 litre, as the 970 is based on a 1275cc engine stroked right down so is a much bigger bore.

Personally, i would soon have more CC in general though, not less.

 

I wish it was as easy as steel internals and raising the limiter

You get to a point at which the piston cannot accererate quick enough to cope with the revs.

This can result in worn skirts on the piston and eventual engine failure due to the stress of the engine not coping.

I wouldn't rev it past 7.5k IMO with all the right internals with an 88mm crank.

Most motorsport engines rev at 20+ m/s piston speed

Formula 1 engines run at 25+ m/s


At 10'000 rpm a zetec would be around 29 m/s

Even 8'00rpm gives 23.46 m/s

7'500rpm gives 22 m/s

You decide

 

Austen, good point about piston speeds, another reason for a shorter stroke of course

 

So how do you overcome the piston speed problem if shorter stroke typically gives less torque, sort of beats the purpose of making high revs for more punch.

 

it's not so much about the piston speeds, as the acceleration needed to acheive those speeds first up, and then down etc

 

More revs for "more punch"

Sorry, but you have NO idea what a high revving engine is like i suspect!

If you want "punch" go for:
more cc
forced induction



Higher RPM is about stringing every last BHP you can out of a moderate torque figure due to limited capacity.

 

ofcourse i dont have a clue, thats why im asking

 

What car is it and what do you use it for?

are there any race regulations regarding CC etc, or is it just a road car and you can turbo it etc if you wished?

 

Asking generally and used my focus as an example

 

What do you use your focus for?

road driving?

trackdays?

race series?

 

I aint going near race tracks they scare me



100% road legal please

 

high rpm wears things more than lower rpm regardless.

are you asking cause you wanna, or just to learn.

as its totally pointless (unless your limited to certain mods due to race regs, and your not) when you can easily get a zetec producting 600bhp+ and not revving past the usual 7.5k or so...

 

Turbo is your best bet then mate, you dont want to be revving the tits off a zetec all the time, AND its cheaper.

 

just wanna learn


I hate text books all seem to be written for ther peers or hide behind mass of numbers to appear intelligent

 

well i could be tempted, since earning me a lovely pug 407 company car

 

What you up to tomorrow night mate?

come along to the surrey RS owners club meet and i will chat to you in plain english about how to make power from engines in different ways and what the pros and cons of each are if you like mate?

 

Working long hrs doubt i can make it to surrey in time



Appreciate the offer, actually have a confession to make never seen a cosworth up close, let alone been for a ride

 

I'm having trouble sleeping,could you phone me with that very conversation tomorrow night?




BU DUM TSchhhhhhhhhhh

 

PMSL @ bud-weis


CUNT

 

Well you should definately pop along sometime, or to the halfway house meet or whatever, quite a few meets in or around the london area.