N-Dub

I used to have that ***** little thing on my car, till I sold it to Tool for a bigger one

mtnman82

Did I hear someone mention Nutella?

vt951

Let's see "the physics and math of it all" then... what do you think ST's car should be putting down?

vt951

Darn, I was really hoping for a little turbo physics education. Does it really all just come down to air flow (cfm), fuel supply (lph), and redline (rpm), or are there more tricks to it? I can see how there's a lot of art in tuning a setup for a useful power band, but for peak hp are you just trying to maximize air, provide enough fuel for that amount of air, and get the engine to wind as high as you can? I guess what I'm asking is, what is the ST magic that makes his engine put out more than any other 2.5L on here?

Ian Carr

he does has the special tool..

Chris White

Pretty simple really, you tune the system (turbo, cams, exhaust, intake and such) to be as efficient as possible for a certain bandwidth. If you are tuning for a good street car you want 2500 – 5500 rpm, a good track car 3500 – 6500 and for all out dyno power 5500 – 7500.
The higher the Q of the system (the more ‘tuned’ to a particular frequency/speed) the more efficient it is for that speed and the worse it will be outside of the narrow parameter.
Street engines should be tuned for a flat and wide as possible torque curve, race engines operate over a narrow rpm range so you can tune them a little ‘tighter’ and dyno monsters are tuned for a big peak power output at a very narrow rpm range.
ST’s engine is a great example of tuning for a narrow rpm range, it is very successful within that range but not outside of it. Great for a dyno pull but a little tougher at the drags or the track. An engine with a peaky power curve can be difficult to drive fast – lots of traction problems when the power comes on suddenly and not much torque if the rpms drop (but a crap load of fun when its peaking!).

A.Wayne

Tool has the correct power tool for the drag strip .........

He just F/U and took his Bonneville setup to the drag strip ..............

Duke

Ultimately - yes.

If you want to calculate maximum potential power at a given rpm you only need to know the amount of air for each stroke that the engine can inhale to get close to the correct power number.

That also means that if you have a given power number at a given rpm level at a given boost level for a given engine size - you can reverse calculate the VE needed to obtain that power.

vt951

The Q and VE stuff is clear as mud, but thanks for your replies anyway. I guess I need to actually read that Corky Bell book (Maximum Boost) I bought years ago, rather than just look at the pictures. Is that a good source for this info?

blown 944

VE education would be best served by doing research on various cylinder head designs and portwork. It isn't just about the amount of air that can be ingested, it is also about the velocity at which the cylinder head can ingest and dispose of the air. Perfect case is the GM LS1, the runner design is tall and narrow to create a high velocity for the runner/valve size. get good headporting book and this will give you some background.

Garrett also has a quick tutorial about turbos on their site.

Chris White

Sort of....higher velocity will increase the amout of air that a cyliner can ingest due to a tuned air column moving at high velocity causing a ram effect. So it is about the amount of air ingested - in fact thats what VE is all about.

95ONE

A little attempt at the definition we're all trying to make here.

Make a huge hole in the intake runner of the head that say 1000cc can flow through. Not at any speed but it's there. Great. The piston can only ingest say a nice round number. 250cc. So... because it has no problems breathing from 1000cc. It gets the full 250. Take a head with an intake runner that can flow 225cc but with intense speed/velocity effectively ramming more air into the combustion chamber. Up to 260-270. More efficient. Slower moving runner with no speed does not have this effect. One flows 1000cc, another 225cc. Yet the 225cc flowing head works better due to design & Flow.

So... Semantics. Yes, more air, different ways to go about it.

So flow numbers do NOT clearly give the whole picture. Please do not be fooled by larger numbers.

TurboTommy

Well, we can just throw some numbers at this, for the hell of it:

HP = torque times rpm divided by a constant
So, let's say we compare a stock turbo S (247 hp) and St's 680 hp.
They both make their peak hp at the same rpm and the constant (5252) is obviously the same, so we can forget those two numbers, and focus on the torque figure.
According to the hp differences between the two cars, ST's engine would need about 2.75 times the torque than the stock turbo S.
Basically, the torque generated on a turbo engine comes from absolute intake manifold density and the volumetric efficiency at that RPM.
Let's assume the stock engine has a VE of 80% (I'd say it's close, but experts can chime in if it's off too much). Maybe ST's engine has achieved 90% at that RPM; that's a 12.5% increase (it's alot, but possible, I suppose). That still leaves almost 2.5 times the absolute intake manifold density that needs to be achieved (which comes from boost, and the cooling of that boost)
Absolute intake manifold pressure on a stock turbo S is about 14.7 + 9 psi = 23.7 psi
St's engine would need an absolute manifold pressure of about 23.7 x 2.5 = 59.2 psi.
Therefore boost pressure would be 59.2 - 14.7 = 44.5 psi

So, if ST's engine is running in the low 40's boost, at sea level, at 6,000 rpm, with great volumetric efficiency, with intercooling that can take the intake temps down close to stock levels, then I'd say that power is possible.

Other opinions would be great to tell me where I'm off.

333pg333

Paging Mr Tool, Mr Tool??

N-Dub

I like Tool.. He just builds and lights a fire then relaxes and enjoys it.. Something about watching the flames of a fire, it never gets old...