thats why a .63 t34 flat out may just about make a genuine 400bhp and a .48 will just about make 360bhp

 

so what i want is a .63 and run it so im getting 360 ish then....

 

Your getting slightly confused here Gus, but to save my fingers il explain when i see you on Saturday pal

 

 

 

good read this

 

Your right Jim.. so BTTT for it

 

Excellent post! Quality essay, quality read! Why do most engines that use a t34 have low comp pistons and engines that have roller bearing turbos run a higher comp ratio engine?

Kind regards

Paul

 

Eh? I wouldnt say so at all, and what bearing core itd have would make no difference.

What you mean mate, got any examples?

 

I just wondered why most 380-450 ish bhp YB engines use low comp pistons and why Mountune use higher than standard comp on some of their engines and whether a compression ratio was picked to match the amount of air a turbo flowed.

Kind regards

Paul

 

HYBRiD_T, theres a good reason for that,, and the answer is all about the resitrictor

 

and Elf Turbo Max kind of fuels....

 

 

You can't seriously mean there is a difference in the following (except temp difference), and if I misunderstood you, then I apologize..
plenum pressurised with 22psi by a GT40
plenum pressurised with 22psi by a T-2

as long as whatever turbo you use as turbo can maintain the pressure, both cases will give excactly the same amount of air to the engine if backpressure was identical.

 

You've just answered your own Q. Exhaust Back pressure is'nt the same hence gas flow through the engine is far greater with a BIG turbo for the same boost pressures.

 

Theres a huge difference in airflow in those two exaamples

 

Morning Karl...
I must learn to refresh the page before answering a post i opened 5 mins ago... lol

 

LOL as Stu says, my engine equiped with a GT40 makes 530 bhp off 21psi. Try that with a T2 turbo!!! LOL

 

If both had zero back pressure, what will make the flow difference between a T-2 giving 22psi and a GT40 giving 22psi?
pressure in the plenum chamber is the only thing here that dedicates how much air the engine will consume.
This is the only point were choosing turbo comes in. when your engine starts to use more air than the turbo is able to give the pressure in the plenum chamber will fall as a result of the turbo giving less air then what is used by the engine.
this is the point were a GT40 will let the engine start producing more power simply because it CAN flow more air.

flow-capacities of the turbo aside, 22psi will be 22psi nomatter what chunks it into the plenum chamber. its very simple physics.

using a GT40 over a T-2 will give a much higher max BHP output with a theoretically non-existent backpressure simply because a T-2 can't flow enough air for 4-500 bhp.
if you still disagree and say 22 psi given by a big compressor is more air than 22psi given by a small compressor, still theoretically speaking (pr writing if u will:P) then explain to me HOW.

 

Here you go..
Took me 4hours to explain it so i hope it helps you to understand better...
https://passionford.com/forum/viewtopic.php?t=24009

 

RSCosworth,

You're being a bit daft and over simplifying the way an engine processes its air. It's not one single factor that contibutes to the power output but the overall dynamic mass engine air flow.

To further your point above, one of my dyno print outs for my engine shows 440bhp @ 6000rpm @ 21psi.

A T3 for example could just about make 21psi at 6000rpm but it certainly wouldnt make 440bhp.

Put simply you are totally ignoring that any back pressure or pumping losses will directly effect the mass air flow rate for the given plenum pressure.

 

"Sorry, but only Gold Members and/or Official Traders can read topics in this forum."

 

no-one said knowledge was free mate

 

never going to happen

 

bolt a T-3 to that engine of yours and it would most certainly not be able to hold 21psi at 6000 rpm. the pressure would start falling at around 300 bhp. it would not get much higher than 300bhp simply because it can't give more air than that. at what rpm that happens depends on the portjob and cam-setup.

For a person with little knowledge of engines and tuning it would be easy to conclude this discussion with
bigger turbo = more power.

If this is correct, then why arn't we all just buying T88's???

 

thats where you could be very wrong from the start,, it would made 21 psi but the air flow through the engine would be small (300hp small)

now you gotta think why have the airflow gone down? maybe more pumping losses?

 

and the inlet temps would be lovely

 

RsCosworth,

Unfortunetly I don't have the time to explain in detail on here, but you are a long way off the mark.

A T3 on my engine will make and hold 21psi at 6000rpm, depsite the engine being highly modified.

As I said its the total mass air flow thats the issue. Just because my engine itself is capable of flowing more air doesnt mean it will when a T3 is fitted. This is because the T3 DRAMATICALLY effects pumping loss due to the HUGE exhaust back pressure it causes. This means that the mass air flow is hugely reduced simply because the T3 exhaust stage massively restricts the mass air flow through the engine. (We must consider the entire pumping process not simply one static pressure point)

You can't add a large compressor to the T3 turbine stage as that will cause surge as you have a mismatch in the compressor/turbine air handling capabilites.

Likewise we dont all run HUGGEEEE turbos because the stall limit of the turbine is at a much higher gas flow which means for a 2.0 litre engine the spool up area will be at very high rpm (i.e. in the region where gas flow is sufficient to overcome the stall zone) and this is unsuitable for most engines and peoples expectations of the engine response.

 

ya like i said karl

 

Its its all explained in my essay in easy to understand laymans terms, which is precisely why it took so long to write......

 

but some people are hard to convince

 

Put it this way ive just thought of whilst doing something else

If we turn the engine off, and then use a drill to spin the T2 compressor up enough to read 21 PSi at the plenum...

How much airflow do we have now?






Sorry, i found that amusing so thought you lot may too

 

So could you use a drill to overcome Lagg???????????

Sorry, just being silly

 

You may scoff....
The new generation of turbos are going to do something just like that

 

Really

best charge up my Dewalt 24v cordless then

 

i have heard something about small motors being placed inside the turbo core,, and once spinning over the engine turning into dymos

 

You never cease to amaze me

The next generation of turbo has an electric wire wound core that will serve as a motor to spin the turbo to speed...

Once up to speed it will become an alternator to power he electrics of the car

 

Like them fooking things that you used to strap to the forks of your bike so that when the wheel spun round it made the light come on

Whats next, big handles on the front to start them

 

ya your dash lights will go bright and dim as you drive

now that is a complement

 

No like an Alternator you coooont