Bolt on turbo sizes

[caffeind]

Okay i only skimmed over the turbo posting rules so dont flame please but i'll try not to break any. I was wondering what the largest bolt on turbo is (i think it's the mitsubishi 20g), how much lag is there on it, and what type of horse power gains should i expect from 15-16psi of boost. Oh yeah, i dont have a eclipse yet but i was looking at the 1g talon/clipse TSi/GSX. Thanks guys,
Luke

 

[deth2u]

Originally posted by caffeind
Okay i only skimmed over the turbo posting rules so dont flame please but i'll try not to break any. I was wondering what the largest bolt on turbo is (i think it's the mitsubishi 20g), how much lag is there on it, and what type of horse power gains should i expect from 15-16psi of boost. Oh yeah, i dont have a eclipse yet but i was looking at the 1g talon/clipse TSi/GSX. Thanks guys,
Luke

a bigger turbo will do (almost) absolutely nothing for you without supplimental mods.

 

[Enigma_Man]

Yes. In general, a bigger turbo isn't really going to benefit you without changing other parts of the car.

I'll explain why though

Because 13 psi is 13 psi, no matter what turbo is producing that 13 psi.

The only real difference you'll see with going with a bigger turbo and no other changes is a decrease in intake temperature a little. This is beneficial because colder air is more dense, and less prone to detonation. Denser air = more fuel = more power. Detonation = ECU pulling timing = less power. So, you _might_ see some performance increases, but barely any, maybe a few horsepower. The reason why the air is colder is because a bigger turbo has to spin slower to produce the same amount of pressure, and has less friction on the air, so it doesn't get heated up as much. But a bigger turbo has more mass, and will take longer to reach the same PSI as a smaller one.

The real benefit to a bigger turbo is when the engine is sortof... out-pacing the turbo. If the engine is drawing as much air or more than the turbo can put out, then the psi is going to decrease. A bigger turbo can keep up with a modded engine better. Bigger turbos are also more efficient at higher pressure levels than with a smaller turbo, so running more pressure is easier, and more beneficial with a big turbo. There's also ball-bearing turbos available that spin up real quick.

But more pressure requires a better fuel supply, bigger injectors, and whole lot of work (beyond just a couple PSI increase over stock).

So, unfortunately a bigger turbo doesn't really mean more power by itself. But think of a bigger turbo as giving you a higher limit on what kind of power you can produce.

Hope that helps,

-Jesse

 

[LaserRST]

You can reach 16 psi with a stock 14b. Set a goal and aim for it. If you just looking for 16psi than stick with the stock turbo. As far as temp differences, its really not that much is hp increase due to temps. Its somewhere in the 2-3% range from what the turbo size saves. Unless you set higher goals than the stock set up will work fine.

 

[-=TWITCH=-]

15 psi on a t-25 and 15 psi on a 20g are totally diffrent MORE CFM!!

 

[Agent Ezzard]

Originally posted by -=TWITCH=-
15 psi on a t-25 and 15 psi on a 20g are totally diffrent MORE CFM!!

He's right you know.

 

[Enigma_Man]

But you're forgetting something, more CFM doesn't matter at all when your engine isn't ingesting that much CFM. Just because a bigger turbo can support, say for examples sake 500 CFM @ 15 psi doesn't mean it's _going_ to push that much air. It can't push more air through the engine than the engine takes at that pressure. If the engine is ingesting, say 300 CFM @ 15 psi @ 5000 rpms, then as long as your turbo can supply at least 300 CFM @ 15 psi, any turbo is going to be exactly the same at that 15 psi, other than the temperature difference.

If the engine surpasses the CFM of the turbo, then the pressure will drop anyway. So no, CFM does not matter in that respect.

Like I said before, a bigger turbo is just a higher limit to what power you can make. More CFM = more potential, not anything else.

-Jesse

 

[Agent Ezzard]

Originally posted by Enigma_Man
But you're forgetting something, more CFM doesn't matter at all when your engine isn't ingesting that much CFM. Just because a bigger turbo can support, say for examples sake 500 CFM @ 15 psi doesn't mean it's _going_ to push that much air. It can't push more air through the engine than the engine takes at that pressure. If the engine is ingesting, say 300 CFM @ 15 psi @ 5000 rpms, then as long as your turbo can supply at least 300 CFM @ 15 psi, any turbo is going to be exactly the same at that 15 psi, other than the temperature difference.

If the engine surpasses the CFM of the turbo, then the pressure will drop anyway. So no, CFM does not matter in that respect.

Like I said before, a bigger turbo is just a higher limit to what power you can make. More CFM = more potential, not anything else.

-Jesse

So what your saying is if the turbo is the only variable then at WOT with a T-25 @ 15psi is gonna make the same power as WOT with a Big 16G @ 15psi at any RPM? When explaining turbo sizes to people that ask I always use the garden hose/fire hose comparison. There will be more water coming out of the fire hose at the same pressure then the garden hose. How this relates to engines is that if that the turbo "A" is producing more volume at the same pressure than turbo "B" then you are gonna create more power becuase then engine has no choice but to ingest those extra CFMs.

 

[RocketBoy]

Have you been in a car with a 20G at 15psi and car with a t-25 at 15psi??? Don't tell me there's no difference. It all lies in the CFM.

 

[nine5raptor]

in order to get more cfm through the engine, no need to increase the pressure; or change cams.
you give it no choice by increasing the pressure

 

[nine5raptor]

take your two hoses and hook them up to a sprinkler. you get the same result with either as long as the pressure is the same.
sprinkler=motor

 

[Agent Ezzard]

You don't have to tell me there's no difference.

 

[nine5raptor]

"Have you been in a car with a 20G at 15psi and car with a t-25 at 15psi??? Don't tell me there's no difference. It all lies in the CFM."

that lies mostly in having the larger exhaust housing, making the engine breathe more efficiently

 

[Enigma_Man]

Yes, exactly. People that have a 20G on their car probably have a _lot_ of other supporting mods than with a T-25.

To continue with the "Garden Hose / Fire Hose" analogy, think of it this way:

Both the Garden Hose and Fire Hose are set up to supply 15 psi. The engine is like a spray nozzle handle on the end of it.
On a stock spray nozzle (motor) the same amount of water is coming out of the nozzle reguardless of the supplying hose. 15 psi is 15 psi, because both hoses can supply 15 psi at that flow level without a problem. (see attached picture) The spray nozzle (motor) is the restriction, and going with a bigger supply hose doesn't really make a difference (the water coming out is slightly cooler, cause it doesn't have to flow through a more frictionfull space to get to the nozzle, but it's essentially the same).

The real benefit to a bigger turbo is when the engine is modded, and can flow a lot more air (on picture, two nozzles on the right). Because the engine can ingest a lot more air, the turbo needs to be able to supply a lot more air. Now, because the bigger turbo can supply more CFM, it can keep up with the demands of the engine better.

You can't force more CFM through an engine just because your turbo can support it. The amount of air the engine takes is based on pressure, not flow rates. The flow rate just represents a maximum to the whole system.

The CFM through the motor depends ONLY on pressure, and engine modifications.

If anybody would like an even more detailed explanation, I can draw up a nice animated gif and stuff

 

[RocketBoy]

I'll post this in the "Extreme Forum" and see what others have to say.

 

[2boosted]

What kinda of supporting mods would make a turbo beneificial? Becuase i was think of changing my turbo?

 

[Dieselboy]

Anything and everything to free up horsepower and flow. Intake, exhaust, Downpipe, ported O2housing and exhaust manifold, UICP, LICP, FMIC, list goes on. Think of it as blowing through a small McDonalds straw with no mods. Then after those mods above, think of it as blowing through an empty toilet paper roll. Much easier to breath. Dont forget of course venturing deeper into mod territory, you come upon tuning/fuel issues as well

 

[insane147]

ive been in cars with bigger turbos just slapped on, and the difference is night and day. there is way more power up HIGH because that is when our 14bs and t2smalls run out of breath and cfm catches up. you should atleast have fuel control for them though due to the larger amount of cfm taken in. also remember that no matter what kind of restrictive exhaust you have, the pistons are forcing out the gases with immense force, the turbo does not push the exhaust gases out, so restriction there is alot less important than in the intake side>

"You can't force more CFM through an engine just because your turbo can support it. The amount of air the engine takes is based on pressure, not flow rates. The flow rate just represents a maximum to the whole system.

The CFM through the motor depends ONLY on pressure, and engine modifications. "

so your sayin i can turn my motor off, hook up an air compressor for 120 psi and have huge power then right? i mean if flow is unimportant this would be the way to go? but its not, flow is important, and more to the point, the flow of the 15psi into the cylinders is important. if the stock turbo isnt keeping up, which its not, you need more cfm to be able to maintain the pressure ratio and keep making power. if you look at POLKs head and intake flow numbers, you ll see each runner for ours cars CAN pull in 240cfm or more i believe. thats a good deal of flow so i dont see much restriction in the way for the air to get into the cylinders.
your gonna need a turbo one day, research it alot, go big and buy it once. first buy all the supporting mods because 14b's can be made quick with them.....1 believe the record is 12.49 with no nos...

 

[streetraceboi]

what modifications do you have to have to bolt on the 20g?

 

[2boosted]

thanx for the info, i think i might upgrade i do have a few of those mods, thanx!