EdyJun

With all this talk of new turbo and hybrids I started to think about how much boost (PSI or Mbar) can our engine run safely?

I know there was a person here that blew his engine on a dyno run and I think he was running something like 1.9bar, this was on a dyno so the load on the engine may be different than on the road.

I know MTM likes to replace the head gasket on our car to reduce the compression. (Stock RS4 is 9.0:1; Stock S4 is 9.3:1)


Mike doesn't like to run anymore than 24 PSI (if I am not mistaking) on his RS6/K04s because of the fear that the engine can't handle it. There is not much info on the new the GT turbo setup for our cars and how much boost they run or what the engine can handle. Just that those who are doing the GT upgrades are building up the engine.

So once again:

What is the maximum safe boost that a 2.7T motor can run in STOCK format?

Also what parts are the weakest links?


Edy

<start discussion>

Honda ETR

How much power can our engines handle is the correct one. PPL think that boost is hard on a motor but it isnt. The amount of power that you make with it, is the important factor. Someone with 500hp with 20psi has the exact same stess levels on his motor (gaskets, connecting rods, etc) as someone with 500 hp on 28 psi (crappy tuning). There is no reason that ppl can't be running 500hp on pump with ~25psi (except for ko4's). Lets turn up the boost

FixedWing

Power limits are dealt with by building up the internals of the engine. As Edy says, those talking about the GT turbo set-up will do exactly that -- they will replace the con-rods and pistons thinking those those are the weak points of the engine.

The real limit is detonation. There is only so much air/fuel mixture you can stuff into the cylinder before it self-ignites.

Stephen

ryans4

i dont think anyone can answer that question. but my money is on rods going first on stock stuff...

Honda ETR

true, but what is the biggest factor we can play with to off set detonation? Timming.

If someone wanted to test this "max boost thing" All they should do is go on a dyno and and keep adding boost untill the maps start to go slightly lean (ward off any chance of detonation). This is the basics of tuning

My Guess is with proper fueling and a solid open loop tuned program, 30 psi should be no problem, Longevity may be though.

FixedWing

There is a lot you can do to reduce detonation...

Intercooler are for this.

My Porsche will actually cool the fuel before it is injected. Same idea.

Play with timing as you suggest.

Additional fuel can also be added to reduce the mixture.

Ditto water injection.

Better swerl patterns on the injectors and better flow patterns on the intake manifold will even out the mixture in the combustion chamber which can avoid lean spots and hot spots which might detonate.

But even with all of this, ultimately, the limit is detonation. Once the mixture detonates then the engine is going to rip itself apart.

Stephen

TwinTurboTerror

<GASP> You mean that's not in your FAQ directory? 8^)

EdyJun

Yes, i was shocked also. But soon it will be. :-)

TmS4

the amount of force that is created is the limiting factor torque is a good way to measure this. The con rods are the first to go on a 1.8t my geuss is same on the 2.7t pistons are probaly good unless you want a different comp. ratio

EdyJun

Are you talking about pressure vs volume? Can you explain what you said in your post a bit more?