its the amount of air its feeding it so more air=more fuel

 

but surely its feeding it the same air if the boost preasure is the same

 

LOL, I bet this thread goes to 5 pages ......

 

the t34 needs more fuel after a certain rpm .. a t3 type chip will not do this ... i think...

 

this is too complicated , i'm going to annoy the rsoc board for 1/2 an hour, more on my level

 

the volume its like a baloon you can get a small baloon and fill it with air till it hits 22psi then get a big baloon and fill it with 22psi but it will take more air to get to 22psi than the small baloon

 

so do any stg3 chips have a map in them that covers both a T3 and a T34 ?

and if not, why not ?

 

Gus, you're not explaining though mate... you may well be stating the truth, I'm trying to understand WHY..

Why does a fixed 22psi in the plenum flow different amounts of air through the engine with a different pump pushing it in??

 

hey gus, that is a very good analogy

 

This is actually quite a complex subject and i spent literally HOURS one night on the old RSBB and did an essay to try and explain it in laymans terms.. so here it is. It's dealing specifically with why a T4 makes more power than a T3 or T34 at the same boost level because thats what was being argued at teh time.. enjoy

------------------------------------------------------------------

Let’s go back right the way to basics…

Why is it, that a turbocharger is universally is recognised as the ONLY form of forced induction that COSTS power?

Well let’s look at this shall we?
We have a decently specced engine, say an Rs2000 I4 and we are making 170bhp through our otherwise std setup with some head mods and cams.

To make this power we are utilising the air pumping ability of our 4 x 500cc cylinders.

They are drawing in enough air and fuel at the correct ratio and importantly, expelling it again to produce this power. This ability incidentally is related to its volumetric efficiency which i will touch briefly later.

The I4 is making its 170bhp with its nice, well-designed STANDARD 4-2-1 exhaust system.

Let’s now redesign it in the great Ford RsBB fashion and remove the nice exhaust system and stick a tiny pathetic straw sized .48A/R turbine housing on it with a closed wastegate and the turbocharger actually welded tight so it can’t spin.

Does ANYONE on this BB think this engine will now make 170bhp? Well It will be very lucky to make 120bhp now.

So whats happened?

WE HAVE INCREASED PUMPING LOSSES DRAMATICALLY.
This is the biggest issue. The reason this costs us power, is a great proportion of the energy produced from the power stroke of 1 cylinder burning our nicely presented charge of fuel and air is now wasted trying to push the spent gas out of the previously active cylinders exhaust valve and through the tiny turbine housing.

We now have some detrimental knock on effects:
The friction on components caused by this pumping loss now adds heat to our engine too. This heat was part of our power strokes energy.

This pumping loss has also caused the overlap events effective scavenge volume to drop massively as the nice, meticulously calculated pulsation vacuum that designers spent hundreds of hours to create has now been exchanged for BACKPRESSURE.

This backpressure has now also decreased the amount of air the exhaust pulse drew through the inlet valve at overlap when piston speed was at its lowest so maximum cylinder fill has reduced, down goes VE.. Things are looking bad for our power curve now.


So conversely, as we now have LESS airflow on overlap, we are going to start dumping heat through our exhaust seat and port and are heating our soft alloy head up.

WHY? Very simple ,
Designers use scavenging on overlap as a very simple and very effective way of cooling valve seats, guides and ports.

How? Also very simple ,
As we reach overlap in our cam timing event we have both COLD inlet and HOT exhaust valve open, this gives the exhaust valve and relative components time to be cooling from their grievous job only moments ago of shifting a mass of immensely hot air through its system so it’s a great relief to sit in some nice cold flowing air for a second and transfer a bit of excess heat away!!

Our fancy new engine / design isn’t looking too hot now is it? (Well actually, its getting damn hot.. )

So,
I hope this large and simply worded explanation helps you to understand that a turbo DEFINATELY costs power by its very presence on your engine and also why it does so?

Ok? Good!!

So what the hells that got to do with today’s BB argument? Oh yeah, sorry........

Exhaust backpressure caused by the turbine housing assembly’s restriction is our key element between T3 and T4.

But let’s deal with the delivery of our air first and we will use the good old YB for our examples.

A T4 produces far more VOLUME of air at a given pressure from its HOUSING than a T3.THATS UNIVERSALLY AGREED.

Now if we quickly use this bizarre volume of air example supplied by someone earlier...


quote:
--------------------------------------------------------------------------------
Foolishly, sorry, Originally Posted by erm.. someone
Look at it this (simple way so you understand ), imagine a 1 ft diameter balloon inflated to 15psi. Then imagine a 2ft ballon inflated to 15psi - are you trying to tell me that both have the sane volume of air in them?
--------------------------------------------------------------------------------



That balloon is actually bigger so yes it holds more volume, but this is not applicable to an engine because even if we take all the inlet valves out and pressurise the system with our turbochargers, we are still presenting each turbocharger with the same volume to fill, lets say 2000cc for the cylinders and 1000cc for the intake of the head and the plenum / hoses.

So we have a 3000cc volume to pressurise with air. This does not change unless the engine begins to operate. An engine will only generate more power by shifting more air at the correct AFR. SIMPLE.

The engine will only shift more air if we do one of the following:

1) Improve the airs route into the head.
2) Increases the pressure we push it in with.
3) Improve the mapping.
4) Improve the volumetric efficiency.

So,
We still know a T4 WILL make more power than a T3 at the same boost so why is that?

We don’t appear to have done any of the above mods do we?
The head hasn’t been ported.
We are running the same boost.
We aint touched the chip cos PHIL cant remember what spec it was for!
So have we changed the engines VE?

Good question, and back to turbo’s.
A T3 50trim with our desired pressure ratio of 2.4 (14.7psi inlet +20psi outlet divided by 14.7psi inlet) will be spinning at 134,000 rpm with a compressor efficiency of 70%.

A T4 60 trim with our desired pressure ratio of 2.4 (14.7psi inlet +20psi outlet divided by 14.7psi inlet) will be spinning at only 97,000 rpm with a compressor efficiency of 82%.

Now lets go to the turbine housing.
The T4 P trim wheel flows a lot more air than the Std T3 trim rear wheel. (They are all the same as std on T3) but it conversely takes more to spin it to speed.

We now have an exhaust backpressure IMPROVEMENT due to a better flowing rear wheel!!!!!!!

Secondly,
We now have a wastegate that will open much sooner and much wider than it would on the T3 as less exhaust volume is required to spin the turbine as we have a 37,000 rpm improvement in efficiency at our 20psi.

HEY, we have another exhaust backpressure IMPROVEMENT.

If our T4 is using a bigger housing, and it IS if compared to a T3 we have another exhaust backpressure IMPROVEMENT!!

So lets go to boost at the intake:
Now our exhaust backpressure is reduced, our cylinders demand for air has increased. We have overlap efficiency gains, we have thermal efficiency gains so we can suck more air and we can suck it with a greater pull because we are actually revving more freely so our peak piston velocity has increased.

So we are CONSUMING more air and this T4 can supply it for fun… But… we aren’t making more power because the T4 pumped more air at 20psi.

We are making more power because this turbo improved the volumetric efficiency of our engine mainly through exhaust backpressure reductions and an improvement in outlet temperatures at the compressor outlet due to Adiabatic Efficiency which we may or may not discuss later.

Goodnight folks,
If anyone wants to know what the compressor maps do and how to decipher the turbo specs, let me know when ive slept cos this essay took me four hours to write in a fashion that anyone can understand!! It would take about 15mins using techie terms

Best Regards and goodnight,
Stu

--------------------------------------------------------------

Does that help guys?
Lots more interesting essays and info here: https://passionford.com/forum/viewforum.php?f=56

 

Fook... why did i used to waste hours writing essays like that?

 

One example richard,

Think of a larger exhaust housing on the turbo being added.
Engine inherantly has ability to flow more gas.
Hence will require more air in the inlet.
Less residual gas in cylinder draws more air from inlet thus flows more
for same pressure volume.

 

i can also get the balloon theory but cant understand the difference between 22psi of boost going into the engine being different because of the turbo. 22psi is 22psi no matter what is producing the preasure???????????

 

Read above gentlemen.
I hope it works for you as i spent many many hours rewritting that in simpler and simpler terms so as many folks as possible would benefit.. i could explain it in tech terms in about 20lines

 

it has just klicked it is like the argument me and a mate had when we were 13 on the back field about there being twice as much alcohol in a 2 litre bottle of cider than a 1 litre, he said there wasnt cause it was still 9% but as i pointed out 9% of 2 litres is twice that of 1 litre, but is still a fixed 9%. A bit of a funny comparison but i can now see that there will be loads more air going into the engine with a t4 at the same boost preasure as a t3. Thank fook for that

 

Time to lock thread - Everyone keeps going round in circles

 

i all ready understand so no need for me to read it anyhow i read that on rsoc

 

i prefer the cider explanation its much more simpler

 

re write it in tekky terms, I wanna see it

 

Seems natural progression to me Simon

Is chip the same.. answered...

Whats different? Answered.....

How come its different?..... working on answering

 

so if you changed the intercooler ... that could in theory adjust the map ....

 

whys it a waste dude? i bet alot of people have read that

you might as well say tis a waste doing anything on here

 

it wont adjust the map,, but the map will need to be adjusted,, alot of people dont,, but really it should!

 

alps, as i understand this
e.g
22psi coming out of a 10 mm wide pipe is not as powerfull as 22psi coming out of a 1000mm wide pipe, because theres 10 times the airflow because the pipe is bigger even though the pressure is the same, thats why on a turbo 22psi gives different power on what size outlet its coming through coz theres more air even though the pressure is the same

is that right techheads?

 

thats what i said diddle i using the cider theory

 

yeah i cant see only lesser knowledgable people starting to understand

 

Well.. kind of, but due to the fact the ecu has an air temperature sensor and associated compensation algorythm it is largely self compensating as its designed to roughly calculate air density from pressure and temperature although i would never be happy until id checked it was fuelling fine with my own equipment

 

thanks Stu/Simon!

of course.... as I predicted...
It's not just the inlet pressure that's important - it's the total pressure equation across the engine.. DOH!!

Gus - you may have 'understood' but you're shite at explaining

Stu, those essays are Ace! not a waste of time at all!

 

the strut brace,


not really right,,

 

can we have that again please

 

Not quite but your at least heading to the point of accepting its different. Perhaps re read it again and concentrate on the points about the engine having an easier time to pass the air and why it is easier....

 

t3vst4 comparison there

 

but som e "off the shelf" chips are more tailored than others, take the escos AB stg3 chip with pectel board from woodford/PJ - speak to ahmed and this has beed written for 803's 3 bar, 23psi, std turbo, full decat exhaust, no dump valve and std airbox with new (clean standard) paper element and an uprated fuel pump. but llike the discussion goes on - no, you cant just go whacking different turbos, cams etc on and expect it just to work, as the software is written and tailored to how itall works together (and usually on a fairly healthy engine) no point added 10 psi of boost with bigger injectos etc on a fooked engine - you will just sentence it to an early grave.


but i agree totally - if my car was live mapped it would probably yield more power, torque and better fuel economy as even every new engine will vary vastly due to manufacturing tollerences. but if you've already outlayed money down one route - you either stay down that route or cut your losses and go to the more accessable route

 

Thanks Rich & Gareth i take that as a huge compliment coming from you two guys as i consider you both very clever people indeed having watched your own postings for many years.

Thanks again

 

but Gus, that ISN'T the reason is it?..... it's the exhaust side restricting the outlet flow and restricting the VE that's the issue ...

 

i was trying to do the comparing turbos explination thing, nowt else, so i'm a bit right , fuckin get in!!!

stu , you'll be headhunting me for mapping and tuning next

 

 

Stu @ M Developments, thanks for the compliment stu,,, its nice to have a compliment from someone i look upp too

 

no because what about a .48 t34???????????? that needs more fuel correct me if im wrong

 

The improvement in airflow at a given pressure from a bigger compressor is only any benefit if the overall VE of the whole engine is improved - in this discussion that comes from reducing the backpressure at the exhaust side.