Whilst doing a bit of reading I found that some Garrett turbos are available with different size compressor inlets....The're available with 2.75" 3" or 4" inlets

I believe the 3" inlet is currently being used and wondered why this was?
Is it for any reason other than ease of inlet pipe fitment?

As the rest of the turbo is spec'd the same and the only variance is the inlet diameter I am interested to hear if this would make any difference to performance?

I see most people go for 3" inlets with fender mounted intakes
Has anyone tried 2.75" inlets with EvoMS 70mm hard inlet piping?

 

".....If you can drop the turbo outlet pressure, or raise the turbo inlet pressure, that will drop the turbo discharge temperature....."

Anyone have any thoughts?

 

The less the turbo has to work to inhale the easier it ought to spool and make power IMO. Given a choice I'd go for the largest inlet and inlet piping I could, I believe it will aid spool and ultimate power production so long as the inlet piping doesn't provide significant restriction - which our OEM piping DOES appear to do. The fender inlets drop all of that piping and breath VERY well. However you must go blow thru MAF and you lose the top half of the intercooler piping - boo! there are also some concerns about dirt kicking up in there since the inner fender lining must be cut to allow piping to pass through. I have this fantasy that some soft rubber ought to seal that area well but not having done it I don't know how effective that would be for stopping dirt infiltration - how much will those parts move? Obviously swapping out or cleaning air filters is a PITA when they are mounted in this way and fitting large enough air filters for the airflow needed is also difficult. IMO this piping should flow much better than the EVOMS setup - the question of the day being does the replacement piping for the OEM setup flow good enough for power that most of us are making?

 

Ask Joe - didn't he reach over 230 MPH in the mile with the EVO pipes? I think that's the fastest of any intake pipes...

 

I think Jo has the Evo intake and am absolutely certain this can be used to just as good effect as the fender intake.....absolutely certain

The bit I'm trying to understand is....

"Raising the pressure of the air entering the turbo will reduce the temperature of the air leaving the turbo"

I understand why it is beneficial to reduce the temperature of the air leaving the turbo, but to increase the intake pressure you would surely have to use a smaller pipe, and this would choke the turbos....this is where I get stuck

I have been speaking with a family friend today and he has been explaining it to me, but he's too advanced for me and I quickly get lost.

He's an engine designer, so he can tell me exactly what does and doesn't work and the reasons behind it, unfortunately though i'm too stupid to understand it

Can someone explain the bit about increasing the intake pressure

 

Ok, I have spoken with someone else more knowledgable than myself (thanks Earl)
and he has explained it in a way that I understand

With regards to "increasing the pressure of the air entering the turbos" we're not actually increasing the pressure as such, rather just minimising loses

ie, there will be restrictions and loses as the air goes through the intake piping (from the air filter to the turbo) meaning the air enters the turbos at less than atmospheric pressure (i think)

By reducing these pressure drops we have kept the air pressure closer to atmospheric and therefore "increased the pressure of the air entering the turbos"

As the air entering the turbos is now at a higher pressure than was previously possible the turbos wont have to work as hard to reach the pressure we require


So, we're not looking at increasing the pressure at all, rather just minimising loses along the way