max boost for forged Hawk Sti?
 

I've got a Hawk STi with a forged engine, mods below. I'm experimenting with tuning and wondering what the max boost would be for it? It was recently mapped by a specialist (who built the engine) and he mapped it for 19.7psi max, but I'm guessing he was playing it safe.

Appreciating that the stock turbo won't be able to blow that much at the top end, I'm after tuning it for mid range torque more than top end power.

I'm guessing peak boost would be ~21 psi max, seem reasonable or way off?


Cheers!

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Relavent Mods
ACL Race Bearing Set
Rebore & Hone To 99.75mm
Mahle 4032 Piston Set Inc Rings
RCM 11mm High Tensile Head Stud Kit
RCM 0.78mm Stopper Head Gaskets
Cobra sports cat downpipe
Cobra sport centre
Prodrive backbox

Should be good for 1.5bar (22psi) peak then tailing of up the Rev range...anything more and 14mm head studs would be playing safe IMO

Max boost will be determined by what turbo you have not what engine you have in most cases.....

You will need to calculate how much air you want to move, at what rpm etc from the flow graph from the manufacturer.

On a CT9 there isnt any point in running more than 1 bar of boost as it is out of the turbos effiency range and will just heat the air up rather than pressurise it.

And unless you understand the relation in how efficient the turbo is in relation to its CFM of air moved you cant really determine what boost to run. And just copying other people isnt going to help you understand this in context to learning to map

thanks both for the answers, certainly looking at the compressor efficiency map was on my list of things to consider, but can anyone point in the right direction to get it?

Std Hawk Sti turbo is: CT9 and/or IHI VF43 and/or GTXXX?

Plenty of people running 1.5 bar on a VF 43, standard boost is just under 1 bar

A ct9 was just an example. They are fitted to toyotas.

To map it succesdfully you will need to see and figure out the conpressor map and understand it

good luck finding a compressor map for a VF anything they are next to impossible to find with any type of scale on them. 1.5 bar mid range and taper down up top if you want to get the absolute most out of it - however the specifics of your car/intercooler/fuel quality may limit you getting the most out of that amount of pressure so don't be all gloomy face if you find that 1.5 bar isn't giving you as much lift as 1.45 bar.

Without the compressor map you'll have to feel it out with gradual increases to boost (followed by revisiting timing/avcs/fuel) then compare before/after virtual dyno runs to see what kind of benefits you've unleashed. Rinse and repeat until your happy with your work.

I would definitely recommend a decent set of det cans if you don't have any already and don't forget to test your car in different circumstances after you've been making changes. What works fine on for a 4th gear rolling start up the motorway in the cold intake temps of a cold night may not be as good on a twisty backroad lunchtime blast in hotter intake temps.

thanks as always for the advice! I did make my own det cans from a knock sensor, a laptop, a set of in ear headphones and some ear defenders, it works ok but gets a lot of crackling and interference from about 4k rpm onwards which I think makes it difficult to hear knock at the higher RPMs. I'm looking to get the ones you suggested previously (http://www.phormula.com/KnockAnalyserPro.aspx) as well and Innovate wideband next month.....