turbos
Turbo Mini Forums

Dave, I never intended to answer the question of which one is best!

If I can get all the maps, for all the trims I might have a go thou lol

Then again that would be purly theoritical.

Wil,

The air flowing through the inlet becomes the exh gas, thats all I was getting at.

Alex

AlexF

[scouce accent] calm down calm down [/scouce accent]

I'll repeat:

"Dave, I never intended to answer the (t2 vs t3 : which is best!) question of which one is best!

If I can get all the maps, for all the trims I might have a go thou lol "

I've addmitted on this thread I like T3s, I have plenty of them and I dont want to buy new when what I've got will work.

The original point of my ramblings was to point out theres a difference between air flow and PSI. Its kinda gone in all directions after that.

Ultimatly a t3 will flow more air than a t2 and so will make the most powerful engine. As to one from of proving that (drag racing) I wouldn't be in a position to comment really!

Alex

PS all the T range is antiquated

AlexF

I think there is some confusion here over what a turbo can flow and what it actually ends up flowing when installed. Its the mass of the charge the engine burns that determines what power it produces (at any given outside atmospheric pressure).

Think about this. If you set up two different turbos on a test rig and on the outlet side fixed a restriction of fixed size. then at any given pressure both turbos flow the same (given same temp at the restrictor). An engine is just like a fixed restrictor, at any given rpm and pressure it will consume X cfm of charge.

When the maps are produced i would think that they are done with a variable size restrictor, i.e. a spring loaded valve of some sort. Under this kind of test a larger turbo would flow a greater cfm and mass of air. The maps would be done like this to allow you match the turbo to the engine size and power output required. So when selecting what turbo to use you would look at what what your engine will consume and select a turbo that flows this mass of air most efficently. Here's another thought for you, would you select a units whos peak efficiency matches your requirements at peak power or peak torque ??

Turbines.
a turbo extracts energy from the exhaust gasses to compress and thus flow a greater mass of air to the inlet of your engine. In theory to compress air to a given pressure requires a fixed amount of energy. Or looking at it another way to accelerate and move a given mass of air takes takes a certain amount of energy. So in other words the turbine has to extract a given amount of energy from the exhaust gasses in order to perform the work of compressing / moving the required mass of air at the compressor side of the turbo. Effectively the energy extracted is proportional to the pressure drop over the turbine. So if you discount the efficency factor of a large or small turbine for a second and assume they are the same. The exhaust manifold pressure would be the same. Think of the exhaust manifold gas pressure as potential energy. In real life this is not the case as the different turbines will extract the required energy differently due to there characteristics at a given flow of gas into the turbine and so you would see variance in the exhaust manifold pressure dependant on the efficency of the turbine at that rate energy absorption from the gasses. Exsessive pressure/potential energy is released by wastegate. So you choose the turbine that best extracts the energy you need at the given amount of flow your engine will exhaust (flow in / out of engine obviously directly linked) or where in the engines power band you want peak efficiency to be.

Hope this makes some kind of sense, i've had a beer or two.

Anybody tempted for one of my T2.5 hybrids ???? lol.

Dont mean to butt in just a litte thought that has been slightly over looked, unless i missed it haven't got much time to read it right now

The sooner the inlet pressure is built up the sooner that is actually acting upon the pistons.

Although Alex you say the smaller turbo will being creating more resistance to the exhaust stage this slighty counteracted by the the pressure on the pistons on the inlet.

Just a little thought saying that I am still using T3

Edited by mikemph on 14th Aug, 2005.

Good thoughts there M.

"Here's another thought for you, would you select a units whos peak efficiency matches your requirements at peak power or peak torque ?? "

I'd go for peak torque - assuming I was after more peak torque. Currently I want less peak but a much wider band.

Alex

AlexF

Hybrid T2.5 eh? Mirage

I'm assuming that you have put this together with 1275 motors in mind.

We are currently planning on changing to a GT5 T2 on our 998 (rather than the Metro T3). How would your hybrid T2.5 stack up against the T2 on a 998 do you reckon?

And what's the price, were putting togethetr a budget at the moment.

Good explination aswell btw.

Cheers

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

well we may be able to clear this up nuy the end of the wekk as im changing my old t3 .25 to a t3 .36 so we will see what the difference on the rollers, thats going to be the only way.

as im sure we have all seen in the past theory and pratice some times are miles apart.

always looking for them bigger bunches of bannanas

sounds interesting hoggy let us know the results.....