exhaust?
07-19-2003 | 04:46 PM
#2
RL Technical Advisor
Joined: May 2001
Posts: 11,871
Likes: 66
From: Portland Oregon
Hi Paul:
Generally speaking and all things being equal, ones fuel management & induction system determines A/F ratios.
Exhaust tuning and dimensions and mufflers does alter that.
May I ask in what context you are asking? What car are you referring to?
Generally speaking and all things being equal, ones fuel management & induction system determines A/F ratios.
Exhaust tuning and dimensions and mufflers does alter that.
May I ask in what context you are asking? What car are you referring to?
07-19-2003 | 05:29 PM
#3
Thread Starter
Pro
Joined: May 2001
Posts: 544
Likes: 0
:
Steve,
I appreciate you taking the time.
I have a 2.5 944-spec racer. So that means basic stock motor with 10.2 88 pistons, custom chips with proper a/f mix and max ignition advance w/o detonation. Tested on a dynojet to get max trq/best a/f...ect...
I upgraded from the 83 cast stlye header to the factory late model tube type header. Now the factory tube type has cracked so I got a set of equal "tuned" 4-2-1 tube type header with matching pipe also supposedly tuned it is "28 inch's long".
Anyway my concern was that I'm going to WS next weekend from Phx. and won't have time to test it before then and with the new exhaust I wondered if there would be a difference?
I am thinking it shouldn't be any worse than stock? I am really concerned about losing low-mid trq!
Thanks,
Paul
I appreciate you taking the time.
I have a 2.5 944-spec racer. So that means basic stock motor with 10.2 88 pistons, custom chips with proper a/f mix and max ignition advance w/o detonation. Tested on a dynojet to get max trq/best a/f...ect...
I upgraded from the 83 cast stlye header to the factory late model tube type header. Now the factory tube type has cracked so I got a set of equal "tuned" 4-2-1 tube type header with matching pipe also supposedly tuned it is "28 inch's long".
Anyway my concern was that I'm going to WS next weekend from Phx. and won't have time to test it before then and with the new exhaust I wondered if there would be a difference?
I am thinking it shouldn't be any worse than stock? I am really concerned about losing low-mid trq!
Thanks,
Paul
07-19-2003 | 07:29 PM
#4
RL Technical Advisor
Joined: May 2001
Posts: 11,871
Likes: 66
From: Portland Oregon
Hi Paul:
Boy, you have me here
....we are 911 specialists and my 944 knowledge & experiences are quite limited.
I would ask whether the Dynojet tests and optimizations were done with the cast manifold, or the 4-into-1 Factory header.
IMHO, I think you'll be just fine changing from a 4-into-one header to a tri-Y style (4-2-1) header. The operational differences are in the shape of the torque curves and there will be some changes in the A/F ratio. I do not think they will cause you any grief, given the conservative setup of your engine.
You should gain mid-range torque with such a header.
Boy, you have me here
....we are 911 specialists and my 944 knowledge & experiences are quite limited.I would ask whether the Dynojet tests and optimizations were done with the cast manifold, or the 4-into-1 Factory header.
IMHO, I think you'll be just fine changing from a 4-into-one header to a tri-Y style (4-2-1) header. The operational differences are in the shape of the torque curves and there will be some changes in the A/F ratio. I do not think they will cause you any grief, given the conservative setup of your engine.
You should gain mid-range torque with such a header.
07-25-2003 | 12:29 AM
#6
Burning Brakes
Joined: Nov 2002
Posts: 761
Likes: 0
From: 2 ends of the Pacific
Did you increase the header and secondary pipe sizes? Increasing that will give you a higher peak hp but you might lose some low end especially if the headers are not equal length. Is that 28 inches from engine to the merged single pipe? ie. the last "Y"