High reving

[LucasHigh]

Hi all I'm planning to take off the head of my car here in the next month (have plenty of parts on the way), While I'm in there I'm doing timing belt, water pump, head studs, block mod, and most importantly to the question at hand is valve springs). What's the highest that is recommended to rev without keying the crankshaft?

The reason I want to rev higher is I currently have a garret 2560r turbo and am not happy with the power band and want some extra rpm of usable power.

 

[dhminer]

Hi all I'm planning to take off the head of my car here in the next month (have plenty of parts on the way), While I'm in there I'm doing timing belt, water pump, head studs, block mod, and most importantly to the question at hand is valve springs). What's the highest that is recommended to rev without keying the crankshaft?

The reason I want to rev higher is I currently have a garret 2560r turbo and am not happy with the power band and want some extra rpm of usable power.

Most limit to 7k, some are comfortable with 7200, and I’ve never seen someone over 7400.

 

[Dialcaliper]

Hi all I'm planning to take off the head of my car here in the next month (have plenty of parts on the way), While I'm in there I'm doing timing belt, water pump, head studs, block mod, and most importantly to the question at hand is valve springs). What's the highest that is recommended to rev without keying the crankshaft?

The reason I want to rev higher is I currently have a garret 2560r turbo and am not happy with the power band and want some extra rpm of usable power.

Stock head and especially cams basically run out of breath at 7k, going much higher is squeezing blood from rock. To do so you’d need longer duration cams, which depending on how aggressive you go, might mean upgraded valve springs (especially as the revs get higher)

 

[Intuit]

In addition to the above, the bore/stroke ratio is not optimized for ultra high revving. Places too much stress on the lower end. Frequent rebuilds will be required to keep it together.

 

[M-Sport fan]

Yes, generally, 'under-square' engines are not built/designed to be high rev 'screamers'.

 

[scooter123]

In addition to all of the above you have to consider the volumetric capacity of the turbocharger. Once you hit the limit for CFM output more revs won't provide any more power because you won't have enough air to gain in power. Basically it's very likely that your best option is a larger turbocharger. I will also note that once you exceed 300 HP you will eventually find that the stock rods and pistons cant handle that much power and be reliable. Sooner or later you will blow up the engine. If you want 400 HP then you should really start with the Mountune premium Long Block with the cylinder support system and forged pistons and rods designed for that level of power. Then you'll find that the stock transmission won't holp up so that will be another 10K or so for a more capable transaxle.

Personally if I wanted to build a killer Fiesta ST I would start with a used one with a blown motor where you can get it cheap. Then I would strip the body down to the basics and start installing chassis braces. After that I would get a wrecked Focus RS with an intact powertrain and spend time shoehorning than into the Fiesta ST. End result is a 2.3 litre engine that has proven reliable at well over 400 HP and all wheel drive to get it to hook up with all that power. I expect that the end result would cost less than building a 400 HP two wheel drove Fiesta. Rumor has it that there are two of these conversions in the Metro Detroit Area and one has a full tilt 630 HP 2.3 that likes to humiliate the Red eye Hellcats.

 

[M-Sport fan]

^^^I'd like to know/see build videos on how they adapted the RS's AWD system/drive train/subframe into the back of a Fiesta.

Most likely yes, MUCH less co$t than trying to get the Rally 3 AWD drivetrain 'kit' from M-Sport and adapting that, with the added benefit of not having to deal with a frequent rebuild required sequential gearbox, and 'on-off switch' racing clutch on the street (as cool as that would be if one could swing that expense and inconvenience, and stay totally away from stop and go traffic jams).

The thing is, just how many wrecked FoRSes are out there to begin with?

 

[Dialcaliper]

^^^I'd like to know/see build videos on how they adapted the RS's AWD system/drive train/subframe into the back of a Fiesta.

Most likely yes, MUCH less co$t than trying to get the Rally 3 AWD drivetrain 'kit' from M-Sport and adapting that, with the added benefit of not having to deal with a frequent rebuild required sequential gearbox, and 'on-off switch' racing clutch on the street (as cool as that would be if one could swing that expense and inconvenience, and stay totally away from stop and go traffic jams).

The thing is, just how many wrecked FoRSes are out there to begin with?

Given that specialty wreckers probably snap them all up and there were only 12-15k RS sold in the US, probably not many