Has anyone managed to get 350 BHP on 15psi of boost, I have been told this is possible.

This is with a standard engine and a FMIC.

Anyone?

considering that is only 3 psi over standard who ever told you that is a dreamer!

More like 270 bhp

Standard turbo too? No way

GET A GRIP !!!!!!!!!!!!!!!!!!

errr the standard MY97 WRX runs pretty much on 16psi
(maybe a smidge lower)
their output is 280 p.s

The guy is not a dreamer. just probably an error in facts. (Actually a top bloke!)

The car is due in at a local garage for a dyno day and I think he is going to be dissapointed.

Would you agree that if he has forgotten to add a modified turbo to his spec list this could account for it. Am I right in saying larger turbo at the same pressue = more power?

Yes

Nope..

15psi = 1.1bar, Depending on the year that will be standard boost or just over standard. The make/type of turbo Its irrelvent if its producing that much boost.

Nope 15psi = 1.03 bar
14.5 psi = 1 bar

therefore

1.1 bar = 15.95psi

Are you saying that two different turbos would produce the same bhp if the boost was the same?

I'm running 1.35bar, fmic, uprated pump etc and don't think I'd be near 350bhp...300 maybe.

Ok APPROX!

Of course it will, its only compressing air! Its the same air at the same pressure, it doesnt matter what compressed it

Think about it like this, If you fill a nice shiney metal bucket with a gallon of water and fill a plastic bucket with a gallon of water, they both still contain a gallon of water..

Some turbos do spin up faster, but the peak power will still be the same if the peak boost is the same.

So if one turbo is twice the size of the other one, both running the same boost then it will make the same power? dont think so...

So Davey, a td04 at 1.3 bar might get 280HP, what do you think a GT30 at 1.3 makes on the same engine? 280? Even though it has a cooler, denser charge?

Its not about how much boost/pressure a turbo can produce its the amount of air it can flow that matters

Riding the thread here a bit but does anybody know what bhp a standard 93/94 wrx turbo saloon should be kicking out? roughly?

240ps i believe.

If both are holding 1.3 bar at W.O.T. then both are flowing the same volume of air, its not rocket science!

So if thats true, why will one make 280bhp and the other 400bhp?

the larger turbo at that pressure also puts more IN to the system....if theres more going in then more can come out.

Ok so if we work out the maximum volume of air at a given pressure that can flow through THROUGH the engine at W.O.T. this value at a given pressure CAN NOT change regardless of which turbo you have fitted.

So when the turbo spools up and compresses the air the engine will obviously be drawing in air and creating a vacuum, the turbo has to compress enough enough VOLUME of air to create the given inlet pressure, if it compresses MORE air then the inlet pressure will be INCREASED..

Thats the way I see it unless someone can proove me wrong?

Your right it's not rocket science but that is the only thing you are right about.
A larger turbo will flow more air than a smaller one at the same pressure, otherwise everyone would keep there standard turbo's and just run more boost to get more power.
e.g. a td04 will make a lot less power than a td05 or vf34 at the same boost pressure and a td05/vf34 will make a lot less power than somthing like a garret gt30 at the same pressure.

You are seeing it correct, however the temperature of the air will be a lot lower with a bigger more efficient turbo, which will mean more oxy particles so a bigger bang! and more power. A scoob will always give the set pressure in the manifold but there is a big change in performance on a cold day to that on a summers day.

Also a bigger turbo will supply the flow of air for a lot longer giving an improved or longer torque curve and hence more BHP.

This is the way i've been told it works, if you were to fit improved headers, exhausts and have head work carried out then 15 PSI of cold air might be enough to get the required air into the piston to give 350 BHP, i know of several people getting that power by running 17 PSI with a standard TD05, so if air temp was a lot lower then maybe it's not so far fetched to get it with 15 PSI.

How is the bigger turbo going to provide cooler air? It is the compression of the air that heats it? And I am talking about W.O.T. inlet pressures so the size of the turbo is irrelvent, if it can produce more boost it wont because the waste gate will have opened as we are stating X psi is max boost.

If it's a bigger turbo it doesn't have to spin as fast to flow the amount/pressure of air required for the engine so is therefore more efficent and the turbo doesn't get as hot. It is the heat from the turbo which increases the charge temp. I think anyway.

Being a non techy I can sometimes put things across in simple terms.

Look at this way, you have a 1" diameter hose running 15 psi, it will flow x litres of water per minute. (someone work it please?)

If you have a 3" diameter hose running 15 psi, it will flow 3 times the amount in the same time, hence more air/fuel mixture.

Is this right?

But the pressure is measured in the inlet, we are not changing the size of the inlet.

I think it's more to do with temp than flow, there must be a physics answer as to why a bigger turbo can produce same pressures at a lower temp.

Just found out that he is running a TD05, so I can't think this will make that much difference.