720cc primaries 550cc secondaries?
#1
Senior Member
Thread Starter
Join Date: Dec 2001
Location: Longmont, Co
Posts: 297
Likes: 0
Received 0 Likes
on
0 Posts
720cc primaries 550cc secondaries?
Is there any reason everyone runs the larger injectors on the secondary position? If they're in the primaries, it'll give you the extra fuel capability throughout the entire rev range instead of just after 3800, and with the rumour that many engines go due to leaning out before the secondaries kick in , it seems like the way to go.
#2
I HATE sleepy eyes
Join Date: Nov 2001
Location: Birmingham, AL
Posts: 1,180
Likes: 0
Received 0 Likes
on
0 Posts
there is really not that much need for larger primaries on a lightly modded car as the boost doesnt come on until the upper RPM range. Thats why most people start with upgrading the secondaries.
If youll look at the cars that are more modded with larger port jobs and what not, they are running bigger injectors all around.
If youll look at the cars that are more modded with larger port jobs and what not, they are running bigger injectors all around.
#3
Senior Member
Thread Starter
Join Date: Dec 2001
Location: Longmont, Co
Posts: 297
Likes: 0
Received 0 Likes
on
0 Posts
But even if they're not needed, why not put them in the primaries. You dont get any less fuel in the upper RPM range, theres still 2x550s and 2x720s going. Is it just because its easier to tune this way?
#4
Senior Member
iTrader: (1)
Join Date: Nov 2003
Location: miss, Ontario
Posts: 428
Likes: 0
Received 0 Likes
on
0 Posts
"But even if they're not needed, why not put them in the primaries. You dont get any less fuel in the upper RPM range, theres still 2x550s and 2x720s going. Is it just because its easier to tune this way?"
if u put them in the primary position, u will not give the fuel a chance to attomize as well at high rpm's, thus resulting in less horsepower.
if u put them in the primary position, u will not give the fuel a chance to attomize as well at high rpm's, thus resulting in less horsepower.
#5
Rotary Enthusiast
Join Date: Jan 2003
Location: fl
Posts: 1,255
Likes: 0
Received 0 Likes
on
0 Posts
it also has to do with the fact that higher cpacity injectors have a harder time injecting at lower volumes. i dont know all the details but i know that this is why mazda uses 2 injectors per rotor instead of just 1. it makes the feul delivery much more predictable and controlable when using staged injectors instead of just using 2 1200CC injectors for the whole motor.
Trending Topics
#8
Senior Member
Thread Starter
Join Date: Dec 2001
Location: Longmont, Co
Posts: 297
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by jreynish
I have the stock 550 primaries and 1600 cc secondaries! I dont' see any need to upgrade to larger primaries! unless you are running like 25 30psi on a larger turbo!
I have the stock 550 primaries and 1600 cc secondaries! I dont' see any need to upgrade to larger primaries! unless you are running like 25 30psi on a larger turbo!
And I'm not sure if I agree about the fuel atomization problems, does anyone have proof this is a problem (not saying I dont believe you, I'm just skeptical anyones actually measured it)?
Last edited by incendui; 03-08-04 at 03:28 PM.
#9
I'm a boost creep...
Join Date: Jan 2002
Location: Auckland, New Zealand
Posts: 15,608
Likes: 0
Received 8 Likes
on
8 Posts
Originally posted by BoostedRotors
there is really not that much need for larger primaries on a lightly modded car as the boost doesnt come on until the upper RPM range. Thats why most people start with upgrading the secondaries.
there is really not that much need for larger primaries on a lightly modded car as the boost doesnt come on until the upper RPM range. Thats why most people start with upgrading the secondaries.
But at low load and low rpm when only the primaries are firing, the injector pulsewidth are quite small, especially at idle obviously. A bigger injector would need smaller pulsewidth to flow the same amount of fuel, and injectors (especially big ones) don't work as well at very low pulswidths.
So smaller primary injectors allow better accuracy at low pulsewidths, improving idle quality, driveability, economy, emissions, etc. So you always use your smaller injectors as primaries, and you always upgrase your secondaries first.
Thread
Thread Starter
Forum
Replies
Last Post
eplusz
General Rotary Tech Support
15
10-07-15 04:04 PM