Contour Enthusiasts Group Archives Forums Modifications Forced Induction Did he say twin turbo?

Ok... Lets debate this from a pure american stand point. Size Now lets talk about why exhaust flow is important. Higher boost thresholds make more power and why more importantly 2 turbo`s make less tip then one (turbine inlet pressure) First topic of debate. "A t3 turbine housing will flow more then anyone is able to bring out of duratec"

Well now.. Since exhaust flow a deteriming factor of tip pressure is directly related power I dont see how anyone can make a statement like that and know what the hell their talking about. If you bring TIP down power goes up. If you put a t4 turbine housing on a duratech with an equivalent a/r Tip will go down Power will go up and the boost threshold will go up as well. If you use 2 t3 turbine housings it would be obvious that tip would go down boost threshold would go up and power would go up as well.

In no case does a smaller turbine housing make more power then a larger turbine housing considering that the gas has enough power to spool the turbo to the same amount of boost as the smaller turbine housing.

A/R ratio`s are nearly directly related to the boost threshold and thus Using a numerically lower a/r has a numerically higher boost threshold. A numerically higher boost threshold (all other things reminaing constant such as shaft inertia and turbine design) will create more power at the same PSI rating because of superior gas flow.

It is my undata enrinched theory that tip can be brought down and the boost threshold brought up by using 2 good sized turbo`s (and more cheaply might i add if gotten from a junkyard) then using a single large low a/r ratio turbo that would have to be ordered from an aftermarket performance shop(expensive). And because of manifolding design the 2 seperate turbo`s could be made closer to the head so less heat would be loss to atmosphere. I have been rather unimpressed with the numbers the duratech`s have been made to bring about yet. Focus central has a 460 whp zetec
(230 hp per litre to wheels) while the highest number iv heard of is 450 whp from a 3 L (150 hp per litre to wheels) This concerns me because the v6 heads outflow zetec heads by about 60 cfm at maximum lift per a cylinder (the tumble port v6`s ) So im just asking questions and telling people what i think.

If someone has test data to show that Tip cant be reduced anymore with having maximum boost at 4500 then id be satisfied. But I dont need boost until 4500 rpms because The engine has above and beyond the torque i need below that. SO its useless to me. It occurs to me that yea to some people that torque is priceless but to me its all about what happens from that first second shift (7300-4700) and then after that everything is kept at or above 5000 rpms. By Keeping TIP down larger higher duration cams can be used without reversion being a menace. So this also helps out total engine breathing.

And mayby a custom intake manifold latter and youd see the numbers that the zetec is getting. (or even better i believe considering intake flow) So how exactly are these arguments wholly incomplete and inherently flawed. What i said at the beginning is exactly what im saying right now. Its what hopefully you already knew and what iv had to explain to you as if you didnt. Perhaps you would like to adress me with a new turbo theory on TIP Reversion and so fourth so i can tell the rest of the racing community about your discoveries. Because obviously if this line of thought is flawed then everyone down to Formula 1 is too.

Actaully i just check there and they were pumping out 259 whp per a litre. 518 whp 610 or so crank 500 ft lbs crank. For the duratec to be on par with the built engine it would have to see nearly 800 whp 950 crank and 740 ft lbs of torque at crank with 630 ontap at wheels. Right now the baddest of the bunch is producing half that.

im sure these foci are running lower compression pistons as well though, unlike any of the contour guys right now. btw, was that focus strictly boost or was it running nitrous as well?

Your whole theory about "turbine inlet pressure" being the #1 factor in turbine efficiency is flawed. It's obvious you don't understand the basic theory of turbines in that they convert thermal ENERGY, into mechanical, and that pressure is secondary.

The whole fact of the matter is that you're acting like a sea-gull: you come around, make a hell of a lot of noise, sh!t on everything and then leave.

Take a look at the turbo kit on a Contour and realize that there's no way in hell that 2 turbos of even the GT-T28 size, will fit in the Contour's engine bay. It's common knowledge that a Focus has a large engine bay to start with.

Plus, so far power output numbers on the turbo'd cars out there has been limited by static compression ratio. i.e. as high as 10.25:1 (like my 2000 SVT), thus boost is limited = = power output is limited.

A ZX3 has a compression ratio of 9.6:1 and Tom's 460hp Zetec has upgraded internals.

Wait until Jim's car is finished (forged low comp pistons & forged rods), then we'll compare numbers.

Its more pressure then thermal and further more I made numerous statements about how the v6 duratech is a better engine.. guess you didnt pick that up either..

I guess thats why they also do turbine maps in pounds of pressure instead of degrees. Pick up a book sometime. TIP is usaully 2:1 on a street setup. So if you make 10 pounds of boost 20 pounds of tip is produced in the head to turbine area.(34.7 atmospheric) Once it goes to the otherside of teh turbine you goto to basically 14.7 Thats a 68 percent drop in absolute pressure. Comparitivly temps drop do to adiabadic efficiency of going to one temperture gradient to another and do not really "fuel" the turbine as much as you would think though it does help. 34.7 at 1500 (1940 absolute) degrees to 14.7 is around 822 degrees absolute at adibatic. Although thermal does creat alot of the gradient the specific heat of the atmosphere doesnt really diffuse fast enough to suck the turbine anyfaster. gas pushing pressure creates more work.

Also did it ever occur to you that to make 20 pounds of psi in the exhaust chamber means that the entire combustion chamber volumn is no where close to emptied? So on the next engine cycle you have all these inert gasses taking up space and not burning anything. If you can get TIP below 1:1 you really flush the combustion chamber and real power can be achieved.. but this is pretty hard to do. This is the same concept as putting on an exhaust system that produces 20 pounds of back pressure. You wouldnt consider a system like that any more performance then i would consider a turbo that produces 20 pounds of back pressure (tip) Also you gotta remember all the pumping losses associated with all that back pressure. The engine uses 68 percent more energy to complete the exhaust stroke under that much back pressure then it would naturaully aspirated (at the top of the exhaust stroke) (the energy used is perportionate with the gradient of pressures before and after) with a completely untuned log style header. Tuned length headers create negative amounts of pressure to suck out exhaust.

SO dont even come after me telling me my tip statements are erroneous.

dang it, I wish I weren't so busy at work today . . . hopefully I can respond here this evening.

Im looking forward to it. I havent debated a good technical issue like this ina while. Mayby i can learn something.

I'll leave the technical arguements to Rara, as I know practically nothing on the matter, however, what I don't understand is why you're even still talking about the subject.

TWO TURBOS WON'T FIT!

How many times do people need to say it, geez... This is a pointless discussion, that while amusing in the beginning, becomes old very quickly. Why don't you move on to things that actually apply to our cars... just a thought