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Discussion Starter #1
OK, what stops you from doing this? As Turbo engines hit high boost levels they tend to hit their 'limit'. Now what stops a LET running at 2 bar? Is it pressure (2 atmospheres breaches the head gasket or something like that) or is it because the mixture and the engine just get too hot and can't be cooled enough?
 

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Depends on the revs and the 'breathing capability' of the engine

The KKK could probably be configured to hit 2 bar at 4Krpm (with a crappily-flowing engine)

But so what? Boost is just a means to an end.

It's not boost you're after, it's horsepower.
Which is airflow through the head.
Boost is the resistance to additional airflow

What you want is a LOT of oxygen molecules crammed into the chambers, mixed with the right amount of fuel, then get them to get the hell outta there (save the whales etc)

A stock KKK would be totally outside it's operating range at 2bar anyway, heating up the air to beyond 200C above ambient.
I could tell you exactly how much, but it doesn't matter as it would self-destruct after a while spinning at 200.000+ rpm:beer: :beer:
 

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Getting a Turbo to 200K rpm is a difficult task!

And getting more Oxygen into the engine is the job of the compressor turbine in the Turbo.

Compress the air and ram it into the head
 

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Discussion Starter #6
lmao you guys are missing the point of the question. Ignore the fact that just raising the boost is bad and and that the KKK won't supply it.

When rasing boost, is the limit governed by pressure or heat or both?
 

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Cemesis said:
.. is the limit governed by pressure or heat or both?
both.
a turbo left alone (with no wastegate) will spin itself to destruction once you floor it. Quite easy, actually.
In the meantime it will be producing really HOT air that won't do your engine any good.
Usually it's the pistons that buy the farm first (I know, coz I've run full throttle with no wastegate ):p :eek:
However, if intercooling is damn good(say NOS), I would expect the turbo to exceed 2 bar before it breaks apart.
Stock turbos can do a few bars before they give up the ghost:beer:
 

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I understood it as heat, so the turbo causes's the air to be "super heated" and it made the charge density to drop so less oxyegn is going in, hence big intercooler.
When do the rings go, crank etc??
 

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j1400 said:
I understood it as heat, so the turbo causes's the air to be "super heated" and it made the charge density to drop so less oxyegn is going in, hence big intercooler.
When do the rings go, crank etc??
You're thinking of over-revving the engine.
Different kettle of fish.
Here we're talking of overrevving the turbo. These two don't go together necessarily.
 

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Capacity doesn't really come in with turbochargers, what is important is mechanical strength and thermal efficiency.

Why do you think that during the 80's they had 1.5 litre F1 engines running over 1500bhp, they were limited to about 4.5 BAR to. The figure to aim for was 666bhp a litre which is if we are honest about it bloody evil! lol

Theres only so far you can go before a gasket/bore splits/con rod bends and so on.

Anyway boost isn't the main thing to think about, all engines really respond to is airflow (like JohnA). Sticking on a larger turbo with the same boost as a turbo half the size will give more power.

Look at it this way a small turbo might get a pint into the cyl at 8PSI boost while the larger turbo might get a litre in at the same boost. It simply shifts more air.

Also with a small turbo like John also said you get to a point where the airs so hot that its the heat thats giving the pressure increase.

We can talk more about things if you want.

Chris
 

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So does that mean a larger turbo on the equivalent engine will be able to hold the same boost for further up the rev band??
 

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Yes

Like everything in life it's give and take, you trade something for something else, so beware of hard'n'fast answers, they can't show the real depth of the issues involved.:beer:
 

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There are no problems running my Ecotec at 2.7 bar, thats 40 psi:) But then I do have a decent ecu and turbo.
 

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ATC website is actually a decent one. The engines section about the CR is a prime example.

I feel like belting peopel when they sit there and say I can drop the CR and up the boost and I will get great power - muppets.

If the engines well designed actualy upping the CR while retaining the same boost can drop EGT's, up the power and retain the same fuel consumption. You just need to make sure its burning right.

Although I wouldn't trust a stock block etc with 2.7BAR for long.

Chris
 

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Why not?

BMW M12/13 engine from 80's Brabham F1 car was essentialy 2002 block with steel crank etc, engies made 900 bhp at approx 11,000 rpm
 

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The block may have been a production block but it would have been X rayed, pressure tested and so on.

Sadly not all engines are equal, one may take 6 BAR of boost and make a billion bhp but th eblock cast 2 secs later may go pop at 1 BAR.

if it were my engine I would have a look at it at least. You have core shift and all sorts to think about.

Chris
 

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A block that has coverd more than 100,000 miles will have less inherent stresses than a new block, true the blocks need to be carefully selected and tested but for the most part the block is not usually the cause for concern, the reciprocating parts are. None of the BMW blocks were new they vere all salvaged items.
 

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Indeed a seasoned block is a better staring point. New or 'green' blocks are a pain in the arse for tuning really.

Seasoned blocks are nice and relaxed for want of a better word.

So you trust your engine to run 2.7 BAR all the time then?

Chris
 
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