Hi All,

Until recently I have assumed that turbo spool is directly related to displacement (given everything else being equal).

Real world example, if a turbo spools up by 3500 on a 2.0 - what does it do on a 2.2 or 2.5?

2.2 is 10% more displacement over a 2.0, so does that mean a 2.2 will spool 10% quicker? ie 3150rpm?

What about a 2.5L? will it spool by 2625rpm?

I cant really see how that would be possible, I am hoping it is, but I dont think it will.

Does anyone have an real experience with this? Or examples from our CT9A brothers?

25% quicker would be sweet, it would make all those lag monsters be pretty damn good on a 2.5L..

TIA!

 

it seems that it isn't quite as much faster as the displacement increase would give you, but it is close. 2.5 might spool ~20% faster or so

 

Your black on a 2.1 spools up a little slower than what I would hope for... 5k?

so on a 2.5L you think that would spool by 4k rpm? probably later i'm guessing..

 

my spool is purposely slow - we wanted to keep the drivetrain alive and I have no use for a torque hit like that on the track.

Look at hollywood's spool on his 2.3, or murlo's on his 2.0. 3700 or so on the 2.3, 4200 on the 2.0

 

AMS claims 300-500 rpm quicker spool on the 2.2 big bore, I would assume the 500 is a stock frame turbo or so and 300 a 35r turbo.

The real problem is how much air and fuel is put into that 2.0 after that you could calculate what a 10% increase would be. Then you could figure on how much faster the spool will be by how much more air is moved into the cylinder. This would be a basic way to figure it out. Now remember there are alot of other factors that would be involved in the increase of spool of te turbo. Mainly fuel type.

 

I would assume the other way around... if it's percentage based, then a bigger turbo (which spools slower) would have more RPM's to gain...

 

Not necessarily. I tried to come up with an analogy but yeah I can't. If your increasing the volume of air that natural flows through a turbo it will increase speed because the turbo is a restriction. In a larger turbo it's less of a restriction because the turbo will flow more air naturally. Like taking an air hose with a small nossel, the air comes out fast and at a high pressure. Now take a large nossel and it will come out at less pressure and slower.

Take a stock evo turbo, it will spool at the given rpm, take that same turbo and put it on a v8 5.0, it will instantly be spooled as soon as you hit the gas. It's the same principle. Now take a large turbo, put it on an evo and it will take time too spool, put that same turbo on the v8 and it may reach peak around the same time an evo will with a stock turbo. It takes more air to spool a larger turbo than a small turbo, increasing displacement for that will increase a stock turbos spool Faster than a larger turbo.

 

I'm having trouble trying to explain my thoughts.

 

I think I see what you mean.. but I'm not sure it works like that...

 

You would think that for a 2.2, for any given rpm, there will be 10% more exhaust coming out of the motor.
For a 2.5, 25% more exhaust.

But "spool" for a given turbo probably isn't governed by a nice easy linear equation. It hopefully is close, though
A given turbo will need x amount of exhaust turbine flow to spin the compressor at a certain rate to generate a certain pressure. Based on that assumption, it should be fairly linear, but I'm not sure say a 2.5L makes it 25% "better".
Better than what? you don't know where the end points are, where that line crosses the axis.

Like if a 2.0 spools a turbo at 4000rpm, will a 4.0 spool it at 2000rpm? Same exhaust flow through the turbine, so in (my simple) theory it should!
But everything i have read so far - you never get results as good as that percentage.
25% increase in displacement might get you 15-20% better spool.
I guess it all depends on the VE of your motor too. You might have more displacement, but if the air can't get in/out of the ports.... you'll see less improvment.

 

Keeping all things relative and keeping in mind that the turbo is reliant on exhaust flow/pressure/volume etc. Does a 4.0 use exactly twice as fuel and air as a 2.0? I don't know for sure but I don't think it does. For example my dad's 2006 5.7 V8 uses less fuel than his 1999 3.8 V6. And then you need to look at air fuel ratios and the conversion of fuel and air into exhaust.

Feel free to correct me if I said something stupid but from what I know those will be contributing factors to spool time.

 

Well your not really keeping everything equal there..

new tech, probably lower reving, probably different weights, different driving styles, etc...

if you literally keep everything the same then doubling the displacement probably goes towards 80% of doubling the aiflow through the engine...

So I reckon a 2.5L will increase spool by about 20% over a 2.0L... (keeping everything else EXACTLY the same)

 

i was under the impression the bigger displacement is for help to the slower spooling bigger turbo at lower rpm. So they give more low end TQ by displacement to make a nicer performance curve / range. Not really for a "faster " spooling.

 

More liter's more quick spool.

 

on my previous set up 2.0 with fp black spool was around 4400.....current set up 2.4 with 3586 spool around 4600. I should have put the 3586 on the 2.0 just to compare, but I do think it helps.