Increase boost or adjust timing?

4.2 V8 40v biturbo - 450 bhp
4.2 V8 40v biturbo - 480 bhp (plus)
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mavada
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Increase boost or adjust timing?

Post by mavada » Sun Jul 21, 2013 6:15 pm

As above, whats the best trick to gain power?
Ive heard that running more boost actually makes the car slower due to greater timing correction. The stock turbos are just too small and not very efficient at higher boost levels leading to a big drop off in the higher RPMs and a lot of heat. This motor seems to love timing.
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Re: Increase boost or adjust timing?

Post by posterboyj » Mon Jul 22, 2013 6:14 am

Too much Boost = heat soak=increased air intake temps = timing pull (knock) = reduction in power.

Advancing timing could cause possibly stress the engine - cylinder head damage etc.

Ensure that your vacuum and boost pipework system are leak free.
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Re: Increase boost or adjust timing?

Post by JCviggen » Mon Jul 22, 2013 6:40 am

I don't think these engines love timing particularly...the compression ratio is too high for that. This makes the engine quite drivable off boost and slightly more fuel efficient (hahahah) but if you want to make loads of power then the method is simply tons of boost with appropriate timing. In the end you need more air and fuel in there and timing doesn't do that.

Our engines need larger turbines and better manifolds...in other words, the exhaust side is what chokes them in stock form. That's why all those compressor upgrades still flatline around 550bhp no matter what you do. But, the automatic gearbox is in the way to truly upgrade the turbos so unless you want to go manual you're stuck with it.

I'm pretty sure that ~800 bhp is easy peasy if you could just slap 2x GT2871R .63 AR turbos or something on there, but you can't. Ignition timing is just messing around in the margins somewhere, it's not something that on its own can make anything happen...the spark timing simply needs to be correct and when it is you can't really improve further. So considering we already have easy upgrades to the maximum reachable power levels, both routes are a dead end for everybody with the auto box.
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Re: Increase boost or adjust timing?

Post by bam_bam » Mon Jul 22, 2013 1:21 pm

This.
JCviggen wrote:I don't think these engines love timing particularly...the compression ratio is too high for that. This makes the engine quite drivable off boost and slightly more fuel efficient (hahahah) but if you want to make loads of power then the method is simply tons of boost with appropriate timing. In the end you need more air and fuel in there and timing doesn't do that.

Our engines need larger turbines and better manifolds...in other words, the exhaust side is what chokes them in stock form. That's why all those compressor upgrades still flatline around 550bhp no matter what you do. But, the automatic gearbox is in the way to truly upgrade the turbos so unless you want to go manual you're stuck with it.

I'm pretty sure that ~800 bhp is easy peasy if you could just slap 2x GT2871R .63 AR turbos or something on there, but you can't. Ignition timing is just messing around in the margins somewhere, it's not something that on its own can make anything happen...the spark timing simply needs to be correct and when it is you can't really improve further. So considering we already have easy upgrades to the maximum reachable power levels, both routes are a dead end for everybody with the auto box.
Even with good manifolds the turbine housing is too restrictive.
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