Hybrid Turbo Question: What's the deal?
08-08-2001, 12:32 PM
#1
New Member
Thread Starter
Join Date: Jun 2001
Posts: 26
Likes: 0
Received 0 Likes
on
0 Posts
Hybrid Turbo Question: What's the deal?
So hybrid turboes -- like t3/t4 use turbine housing of a small turbo t3 and the compressor of a big one t4. Thus you get a faster spool up of a small turbo, but the airflow of a big turbo.
Are there any drawbacks to a hybrid turbo? Why doesn't everyone use them? The smaller turbine can't turn the compressor fast enough? Is this turbo good only if you are looking for both good bottom end and top end?
Are there any drawbacks to a hybrid turbo? Why doesn't everyone use them? The smaller turbine can't turn the compressor fast enough? Is this turbo good only if you are looking for both good bottom end and top end?
08-08-2001, 01:05 PM
#2
AudiWorld Super User
Join Date: Nov 2000
Posts: 2,365
Likes: 0
Received 0 Likes
on
0 Posts
Re: Hybrid Turbo Question: What's the deal?
I'm not an expert, but I would think that a smaller turbo working like a larger turbo would get hotter faster. Also, the decreased surface area would make it dissipate heat slower. Just a guess. I think that is why the K04 still has an advantage over the stock turbo in the 170hp 1.8T's.
08-08-2001, 01:08 PM
#3
New Member
Join Date: Apr 2001
Posts: 167
Likes: 0
Received 0 Likes
on
0 Posts
AFAIK the smaller compressor will allow faster spool but less effeciency up top
IE: it will spool to 15psi fast but wont go over. a larger like a true T4 will boost a lil slower than a t3/t4 but will boost to example 20psi. well at least thats how it would work in my crugged up head
08-09-2001, 05:28 PM
#6
AudiWorld Super User
Join Date: Mar 2000
Posts: 3,359
Likes: 0
Received 0 Likes
on
0 Posts
The definitive answer...
...from someone with two hybrids (one in the car and one on the bench)
Hybrids (with a small turbine side and big compressor side) work becuase a small turbine housing and small A/R are good for fast spool up. The fast spool up gets the larger compressor into its efficiency range quickly. The magic of the hybrid is at higher flow levels though. Because the larger compressor is more efficient at higher flow levels, it needs to turn far fewer RPMs to generate the same CFM. The reduced RPMs are good for the turbo. They are also good for the temp of the air charge because as you overspin a small turbo to get the higher CFMs, its effiency is decreased and the air charge temps start to rise.
Actually, my K04/16G hybrid spools up by 3000rpm to full boost (17psi) and I am running wastegate frequency figures of nearly 100% at WOT which tells me that the ECU is trying to divert as much energy from the turbine wheel as possible to maintain 17psi. Translated, the turbo isn't working that hard for the PSI I am asking it to.
Mike O.
Hybrids (with a small turbine side and big compressor side) work becuase a small turbine housing and small A/R are good for fast spool up. The fast spool up gets the larger compressor into its efficiency range quickly. The magic of the hybrid is at higher flow levels though. Because the larger compressor is more efficient at higher flow levels, it needs to turn far fewer RPMs to generate the same CFM. The reduced RPMs are good for the turbo. They are also good for the temp of the air charge because as you overspin a small turbo to get the higher CFMs, its effiency is decreased and the air charge temps start to rise.
Actually, my K04/16G hybrid spools up by 3000rpm to full boost (17psi) and I am running wastegate frequency figures of nearly 100% at WOT which tells me that the ECU is trying to divert as much energy from the turbine wheel as possible to maintain 17psi. Translated, the turbo isn't working that hard for the PSI I am asking it to.
Mike O.
