Question about boost / RPM / engine damage

[theblacktexta]

This is about my girly car - Fiesta ST. I was reading a modding thread on some forum, possibly called homosexualsanonymous.com, that when you have fiddled with your boost, as I have, you have to be careful about stepping on the gas in the higher gears. Eg:

On an unmodified ecu the torque in 6th at low rpm is limited. This is to prevent rod and skirt damage.

When chipped the torque limit is removed and the car makes more power. In 6th gear there's a ton of load on the engine which gets the car on boost faster and at a low rpm. Combine the low rpm and very high torque situation and you're really pushing the limit of the stock internals.

My rule of thumb... If I'm on the highway in 6th and below 3000, I don't give it WOT.

Too much boost at too low of an rpm makes cylinder pressures go through the roof. In my case the hg went instead of something else.

If you don't think it's a problem then by all floor it at 2400 rpm in 6th.

When you build boost, cylinder pressures rise. In a lower gear it's much easier to transfer this pressure and related forces into the drivetrain due to the mechanical advantage afforded by the gearing. When you're in fifth or sixth, the mechanical advantage is not there. Not only do you accelerate slower, but that pressure has basically nowhere to go. This loads up your pistons and connecting rods, and while it won't cause an immediate failure it will definitely weaken them over time.

Thoughts?

[Rorz de Puniet]

Stuff it back into third every time you want to accelerate on the freeway just to be safe.

[jimmyg]

The science is valid. Might be worth going easy in 6th gear.

[lickmyleftone]

Prolonged pinging is bad for your turboed engines health. Don't make it labour. Get up it all the time cunt and she'll be apples.

[Captiva Fan]

Surely the ECU's a POS if removing a boost-limit also removes it's ability to manage pinging under low-revs load like that?
Or are the mods stuffing the ECU's inputs?

[The Pupat]

I'd be more worried about stripping teeth of 6th gear than worried about too much torque wrecking rods and pistons.

[Gary2JZ]

Big load small turbo = more boost at lower rpm. As for the internal strength of the engine I got no fucking idea.

[RB30-POWER]

I'd be more worried about stripping teeth of 6th gear than worried about too much torque wrecking rods and pistons.

I agree, if engine doesn't ping it's fine, might be more general wear and tear sure...

Overdrive gears are for cruising they are generally smaller than the first 4 cogs, so I'd be more concerned with the gearbox also.

[Motherfucker Jones]

Umm… doesn't it have warranty?

Explode engine
Remove extra boosts
Return for warranty
Profit?

[cracka]

Fit a much bigger turbo so it wont make dangerous low rpm boost, and only safe high rpm boost.

[darkside]

Had heard with evos for example, the thing that kills stock internal motors is this same phenomena. ie High boost/cylinder pressure and big torque in tall gears bending rods and ventilating blocks. No det involved, just too much boost/torque.

[lickmyleftone]

^^Typical Nicol response.

[Rona]

Umm… doesn't it have warranty?

Explode engine
Remove extra boosts
Return for warranty
Profit?

They can check when the ECU was last flashed, you are up shit creek without a paddle.

[The Pupat]

Had heard with evos for example, the thing that kills stock internal motors is this same phenomena. ie High boost/cylinder pressure and big torque in tall gears bending rods and ventilating blocks. No det involved, just too much boost/torque.

Yeah but that's how you kill any motor too much torque and the rod just gives up. It doesn't matter what RPM you generate that amount of Torque at.

[Greg Rust]

The XR5 is very similar with what you're experiencing, I'm careful not to load it up hard in 5th and 6th