Boost and Standard Internals

[Moo]

I know 1.2 bar is considered the maximum boost you can run with stock internals and that running more boost can damage the pistons/ringlands but why exactly is this? What is it about running the higher boost that will cause the damage?

I'm just about to have a new turbo and ECU fitted and want to know if i can get away with running a tad more than 1.2 bar. I'm not the most mechanially minded person there is and don't really understand why running more than 1.2 bar on stock internals is dangerous. Informed answers would be appreciated!

[raptor95GTS]

ringlands I think go first as they're the weakest part of the stock engine and when you get some detonation at those boost levels they let go however for the sake of a few bhp why run the risk of popping the engine and giving yourself a huge repair bill.

[dawesy]

yep its not the boost but detonation that cracks the ringland (excessive presure on them from the shockwave)
i have seen a GT4 that was running over 400BHP from japan and the engine was running stock internals, it was mapped in japan and was mega rich though

[bri0905]

But the detonation is normally caused by excessive boost isn't it? The air entering is so compressed it is overheated and ignites before the point it should and breaks a ringland or worse a piston with it.

[NoddE]

Detonation
But also boost, as you will get higher compression ratio which might also kill the weak ring land on cast pistons. The rods however will hold up better than the pistons, just replace the bolts on them to arp if you want to rev above oem limits. The rods only downside is their weight compared to forged ones

[Marf]

Personally I'm not running more than 16psi with my setup.

I have an ST205CC so 18psi may be "OK" but I'm not gonna risk it.

In the real world the car is plenty fast enough on 16psi

[Chr15py]

Moo, might be worth noting that 1.2Bar on a std CT20B is a lot different to a Garrett/Disco 'tato/Hybrid running 1.2Bar. Obviously the pressure is the same but the amount of air is way bigger so surely it isn't going to be "as safe" running 1.2Bar on a bigger turbo as your internals are put under more duty.

Also, my cars engine failed at 1.1Bar....in my mind its luck of the draw
Chris

[greeny]

Although running a larger turbo will also mean the airs cooler at the same boost levels.

Every engine/setup will be different with the amount of boost itl handle remember boost/manifold pressure is a measurement of air not entering the engine.

Also remember some of these engines are 20+ years old now and it'd be wise to atleast do a compression check before raising the boost. I'm sure there's a few engines running around out there with cracked ringlands and not even realizing until they raise the boost and make the problem worse.

[Moo]

Thanks for the replies guys, some handy information there and I understand it a bit better now. General consensus then is don't do it with stock pistons, no matter how good your cooling is.

Will stick with 1.2 bar but think I will get a compression test done when fitting the new bits just to make sure all is ok. It's been running at 1.1/1.2 bar for years so might as well get this checked out.

Chris, will have to hook up with you and Matt when the work is done. It's a bit of a different animal to the last time you saw it

[ashley]

Looking forwards to hearing how it goes Paul, 1bar will be plenty to start with

[raptor95GTS]

Looking forwards to hearing how it goes Paul, 1bar will be plenty to start with

esp in first / second

[Rev 3 Kris]

ran td05 18g at 1.5bar on my standard rev 3 engine for 4 years with no problems and when i stripped the block pistons were in very good condition but was on standalone with radtec

[Moo]

Looking forwards to hearing how it goes Paul, 1bar will be plenty to start with

Won't be much longer now. Got turbo, ECU, injectors and fuel pump sorted, clutch and lightened flywheel on order. Car's going in for parts to be fitted in 2/3 weeks time with mapping to be done in March. Can't wait! 1 bar or 1.2? Decisions decisions

ran td05 18g at 1.5bar on my standard rev 3 engine for 4 years with no problems and when i stripped the block pistons were in very good condition but was on standalone with radtec

It's hearing about other peoples experience with higher boost on stock internals that prompted this post. Think I will play it safe though. Don't want the cost of an engine rebuild after just having spent all this money!

[sjm1984]

also its down to the person mapping it

How the engine copes with 1.0 bar to 1.2 bar of boost.

Some mappers can get more power out of lower boost settings.