MAF and injector size for homebrew using hybrid turbos
03-01-2006, 02:32 PM
#1
AudiWorld Super User
Thread Starter
Join Date: Dec 2002
Posts: 2,718
Likes: 0
Received 0 Likes
on
0 Posts
MAF and injector size for homebrew using hybrid turbos
I am looking into what setup I may want for my homebrew S4 (K04/RS6, GIAC X, TCD, and EBC), trying to find a mathematical solution for MAF and Injector size in hopes to not have to do too much tweaking and also to keep the software close to what setup it was intend for.
73mm maf= 36.5*36.5*3.1416=4185.39 = Stock
83mm maf= 41.5*41.5*3.1416=5410.62= 29% larger than stock
85mm maf= 42.5* 42.5*3.1416= 5674.5 = 35.5% larger than stock
88mm maf= 44*44*3.1416= 6082.1376= 45% larger than stock
90mm maf= 45*45*3.1416= 6361.74= 52% larger than stock
349cc/min - S4 w/4bar (stock) 0% larger than stock
380cc/min - 36lb Bluetops w/3bar 8% larger than stock
390cc/min - S4 w/5bar 12% larger than stock
422cc/min - 36lb Bluetops w/4bar 21% larger than stock
440cc/min - 42lb Greentops w/3bar 26% larger than stock
481cc/min - RS4s w/4bar 38% larger than stock
488cc/min - 36lb Bluetops w/5bar 40% larger than stock
508cc/min - 42lb Greentops w/4bar 46% larger than stock
538cc/min - RS4s w/5bar 54% larger than stock
568cc/min - 42lb Greentops w/5bar 63% larger than stock
Am I just totally wrong in my thinking?
Edy
73mm maf= 36.5*36.5*3.1416=4185.39 = Stock
83mm maf= 41.5*41.5*3.1416=5410.62= 29% larger than stock
85mm maf= 42.5* 42.5*3.1416= 5674.5 = 35.5% larger than stock
88mm maf= 44*44*3.1416= 6082.1376= 45% larger than stock
90mm maf= 45*45*3.1416= 6361.74= 52% larger than stock
349cc/min - S4 w/4bar (stock) 0% larger than stock
380cc/min - 36lb Bluetops w/3bar 8% larger than stock
390cc/min - S4 w/5bar 12% larger than stock
422cc/min - 36lb Bluetops w/4bar 21% larger than stock
440cc/min - 42lb Greentops w/3bar 26% larger than stock
481cc/min - RS4s w/4bar 38% larger than stock
488cc/min - 36lb Bluetops w/5bar 40% larger than stock
508cc/min - 42lb Greentops w/4bar 46% larger than stock
538cc/min - RS4s w/5bar 54% larger than stock
568cc/min - 42lb Greentops w/5bar 63% larger than stock
Am I just totally wrong in my thinking?
Edy
03-01-2006, 02:54 PM
#3
AudiWorld Super User
Join Date: Jun 2002
Posts: 12,088
Likes: 0
Received 0 Likes
on
0 Posts
That's the basic calculation to figure out if it will work with tweaks or not...
88mm ID MAF housing combined with ~510cc worth of squirt is a great combination. Nevertheless there are variations in MAF curve due to sensor and intake type.
Bosch are less forgiving than hitachi with regard to MAF overrun due to the central mounting position of the Bosch sensor. But, the Bosch is more accurate because of this.
Intakes need to be smooth, avoiding any dramatic ID changes and isolated from engine-bay heat.
Bosch are less forgiving than hitachi with regard to MAF overrun due to the central mounting position of the Bosch sensor. But, the Bosch is more accurate because of this.
Intakes need to be smooth, avoiding any dramatic ID changes and isolated from engine-bay heat.
03-01-2006, 03:00 PM
#4
AudiWorld Super User
Join Date: Jun 2002
Posts: 12,088
Likes: 0
Received 0 Likes
on
0 Posts
To apply this to your car is another issue...
You have to ask how fast you want to go and what your tuning philosophy is.
Mine is to run the largest injector at the lowest pressure possible due to the fact that injectors operate most effectively at a lower rated pressure as does the fuel pump.
That being said: a 90mm MAF and ~609cc of squirt (630cc injector at 2.8bar) is my choice.
Mine is to run the largest injector at the lowest pressure possible due to the fact that injectors operate most effectively at a lower rated pressure as does the fuel pump.
That being said: a 90mm MAF and ~609cc of squirt (630cc injector at 2.8bar) is my choice.
03-01-2006, 03:03 PM
#5
AudiWorld Super User
Join Date: Mar 2002
Posts: 17,933
Likes: 0
Received 0 Likes
on
0 Posts
but can't you start to run into an issue of too large of an injector running at too small of a
pressure? I would think there's a happy medium to stay within......same thing would apply to duty cycle.
03-01-2006, 03:09 PM
#6
Not that this really is a consideration when you get to this point, but...
what is your fuel economy like? Is it bad only when hammering on it or does it get worse even when highway cruising?
Trending Topics
03-01-2006, 03:14 PM
#8
AudiWorld Super User
Thread Starter
Join Date: Dec 2002
Posts: 2,718
Likes: 0
Received 0 Likes
on
0 Posts
Imolavirus:Infected that is what I was thinking. (more)
Also, with too large of a MAF your TRUE MAF @ ideal will be way off when it comes to MAF reading, right?
That could cause some misfires I believe.
That could cause some misfires I believe.
03-01-2006, 03:16 PM
#9
AudiWorld Super User
Join Date: Jun 2002
Posts: 12,088
Likes: 0
Received 0 Likes
on
0 Posts
Yea, you can run into an issue if you try to run an injector rated at 3bar at 2bar...
I've run mine as low as 2.5bar with no problems, except that it wasn't enough fuel.
There are also sweet-spots in duty-cycle (80%-95% is good) and MAF (Over 250 g/s peak)
It's by no means a simple problem.
There are also sweet-spots in duty-cycle (80%-95% is good) and MAF (Over 250 g/s peak)
It's by no means a simple problem.
03-01-2006, 03:18 PM
#10
AudiWorld Super User
Thread Starter
Join Date: Dec 2002
Posts: 2,718
Likes: 0
Received 0 Likes
on
0 Posts
I want ....
I want the most optimal for my setup with some head room for later. I will be running GIAC X (K03) and would be using it for day to day driving.
I guess what I am trying to say is that I like to keep the same setup/logic/ratio that GIAC X (K03) has but with hybrid turbos @ ~24 PSI.
Does that make any sense?
Edy
I guess what I am trying to say is that I like to keep the same setup/logic/ratio that GIAC X (K03) has but with hybrid turbos @ ~24 PSI.
Does that make any sense?
Edy