Same boost different turbo\'s...

[Archbish]

night night Glenn (poor bloke\'s gonna be dreaming of turbo housings and stuff now.... *grin*)

Presumably, if the compressor turbine is clipped (the blades of the turbine being shortened) air will flow round the blades better, resulting in less backpressure, so higher flow through the engine.  Although lag will increase, the power will be higher for the same pressure, as more flow will be required to maintain the manifold pressure.  The stock twins must result in higher backpressure, so for the flow required to maintain the manifold pressure is lower than for a single.

IT\'S A MIRACLE - I SEE HOW IT ALL WORKS NOW!! *grin*  Thanks everyone, you\'re all wonderful.

[bnaellis]

Originally posted by Archbish
I understand the temps raised issue, but prior to the manifold, it doesn\'t matter if the boost is coming from Darkest Peru if the manifold pressure is consistent.

Gurj is running ENORMOUS hp at less than standard boost, and without freezing air to 0 degrees kelvin, slicing it up and dropping it into the lower manifold I can\'t see the how the temp can be low enough.  From the engine back, the manifold and impellor are the only differences, but is this enough to cause the couple of hundred hp extra Gurj gets??

If Gurj ripped out his single (and gave it to me), and whacked in stock twins (inc 3 miles of vacuum hose), and ran exactly the same boost, he\'d still lose about 12389129365 hp (at the flywheel).  maybe an extra 10 - 20 degrees intake temps, but no more.  Infact, if he stuck on a little T04, at the same 10 psi, he\'d still lose power.

it stinks of witchcraft to me.....

Hi Mate,

There is not that much difference depends on how the car has been tuned. e.g gurj I think Has about 347 flywheel horsepower at .75 bar
smifta has stock twin turbos at .7 bar got 326 flywheel horsepower on a non ported engine also.
If you have a injector say 850cc with at 45psi of fuel pressure it will flow a given a mount of fuel for a given time frame put a 1600cc injector in it\'s place have the same fuel press the same time frame it will of flowed more fuel in the same period of time.

Same for a bigger turbo for a given amount of pressure a much larger turbine will flow a larger volume of air at the same psi than a smaller turbine would in the same given time period.
Volume is the key not only pressure.
Another example on my car with downpipe,  catback, induction, ecu, and intercooler running at the same psi my injector duty cycle was 100% under wot consistently. when I removed the intercooler and put the stock one back in running the same psi my max injector duty cycle was 84.6 consistently. This was because at a given psi the larger intercooler affected volume a lot mor ethan the stock one does, again same thing applies for the twins(small) turbine and the singles (large) turbine scenario.

rgds

[Archbish]

I think I understand how the different turbo\'s work, and (if I\'ve got the hang of it) that explains how the intercooler affects it too.  For consistent turbo\'s, engine, exhaust and intake, the flow reduction of a given intercooler will result in less air getting to the engine, so the injector duty will be reduced.

the difference with the turbo\'s is the different EXHAUST flow characteristics as the impellors flow much more air than the stock twins (speculation on my part), so more air can get through the engine.  

It\'s not so much the turbo\'s can put out much more air, it\'s that they are less restrictive AFTER the engine, before the exhaust.

[bnaellis]

Originally posted by Archbish
I think I understand how the different turbo\'s work, and (if I\'ve got the hang of it) that explains how the intercooler affects it too.  For consistent turbo\'s, engine, exhaust and intake, the flow reduction of a given intercooler will result in less air getting to the engine, so the injector duty will be reduced.

the difference with the turbo\'s is the different EXHAUST flow characteristics as the impellors flow much more air than the stock twins (speculation on my part), so more air can get through the engine.  

It\'s not so much the turbo\'s can put out much more air, it\'s that they are less restrictive AFTER the engine, before the exhaust.

It\'s actually a bit of both. The larger compressor wheel on s single turbo will flow more air into the engine than the stock twins would and the larger exhaust housing on the turbo as  you mentioned does the same trick in a different way however porting of the exhaust ports and size of the exhaust system plays a big part as well.

rgds

[grinder]

good god - the most technical thread i have ever read on here - and to make it worse OJ started it

what is this world coming to ??

its been a good read though

[Archbish]

In theory, if the compressor side of the stock turbo\'s were kept as original, but the impellor turbines were clipped, they\'d flow better, so more power would be produced - albeit in a smaller power band as they\'d take longer to spin up.  Right?

See Grindy, I can be techy too!

Of course, neons increase the flow rate too...

[grinder]

well of course neons do - and go faster stripes add 20BHP !

so are you thinking of changing your turbo - or just gaining info so that you can call gurj\'s turbo ?

[antnicuk]

Bish
if you get a chance to have a look at a stock turbo unit, you will see just how small and restrictive it is. The manifold and opening into the the turbine wheel really are small especially compared with a to4.

[scooby_si]

& OJ if yer guna "call gurj\'s turbo" like Grinder suggests i suggest you watch yer back i hear he is very protective http://www.smileycentral.com/?partner=ZSzeb008\' target=\'_blank\'>http://smileys.smileycentral.com/cat/10/10_1_114.gif\' border=0> lol
Si

[DRAGON]

The intake temp and the backpressure will be completely differnt on the T78 compared with the twins. Therfore you will get more air into the engine at the same boost and this will equal more power. HOORRAYY
 
Basically you can get different flow rates through the engine at the same pressure due to changing one or more parts within the inlet or exhaust.

[Glenn Butcher]

Originally posted by Archbish
night night Glenn (poor bloke\'s gonna be dreaming of turbo housings and stuff now.... *grin*)

Presumably, if the compressor turbine is clipped (the blades of the turbine being shortened) air will flow round the blades better, resulting in less backpressure, so higher flow through the engine.  Although lag will increase, the power will be higher for the same pressure, as more flow will be required to maintain the manifold pressure.  The stock twins must result in higher backpressure, so for the flow required to maintain the manifold pressure is lower than for a single.

IT\'S A MIRACLE - I SEE HOW IT ALL WORKS NOW!! *grin*  Thanks everyone, you\'re all wonderful.

You were right! was dreaming of turbos!!!  

So - does this mean in the formula, that \'V\' is not constant as I thought?  Would it be fair to say that flow would be the same as volume in this case?

[Archbish]

does this mean in the formula, that \'V\' is not constant

Yes and no...  in a snapshot of the 2 setups, the volume will be identical (I was only talking about the intake manifolds), but given a period of time, the higher flow will result in a higher volume of air...

[iaint]

My understanding is that the intake manifolds are not the same for stocks and singles (as Ross was saying I think) therefore, while V is constant for a given set-up, V was not equal for the two examples.

Iain

[Archbish]

The upper and lower intake manifolds are different?  I thought it was the exhaust manifold that was different - as that provides the feed to the turbo\'s impellor housing...

Certainly the upper intake manifold is the same, and that\'s where the boost is measured, and the lower intake manifold is simply the connection between the UIM and the rotors...:confused:

[Carl]

Hi All,
If the single and twins are on an identical  highish boost,say 12 psi, then answer is simple.(This is just for the sake of argument)

The twins heat up the incoming air more than the larger single does,which means even though they are at the same boost pressure the single is more efficient due to more air molecules being present per square inch of incoming air.

There are many other parameters, such as compressor maps, that come in to it but that is the simple answer as to why the right single turbo can make more power at the same or sometimes even less boost.

Kind regards
Carl;)