N/A runs lean above 6500
Thread Starter
I "lost" my emissions....
Joined: Apr 2005
Posts: 1,764
Likes: 6
From: lillington, nc
N/A runs lean above 6500
88 gxl running a 91 n/a
running pacesetter header, no cats, to borla mufflers
K&N intake
No emissions
rebuilt injectors and freshly replaced orings
No vac leaks
new rewired fd fuel pump and strainer and new fuel filter.
Safc
OK so according to my dyno runs the car has a rich spike at 6500 to about 12 afr then begins to run lean above 6700-6800 rpms in the 14-15 afr range. its kindof spiky which seems to rule out the fuel pressure idea.
Ive tried adding fuel via the safc and im getting no response.
advanced and retarded the timing with no improvement on afr.
Its like either the injectors cant keep up or im seeing a loss of fuel pressure.
it doesn't make any sense as the injectors should be good enough for this application; and the fd fuel pump has got to be good enough to maintain pressure for an n/a
any thoughts?
running pacesetter header, no cats, to borla mufflers
K&N intake
No emissions
rebuilt injectors and freshly replaced orings
No vac leaks
new rewired fd fuel pump and strainer and new fuel filter.
Safc
OK so according to my dyno runs the car has a rich spike at 6500 to about 12 afr then begins to run lean above 6700-6800 rpms in the 14-15 afr range. its kindof spiky which seems to rule out the fuel pressure idea.
Ive tried adding fuel via the safc and im getting no response.
advanced and retarded the timing with no improvement on afr.
Its like either the injectors cant keep up or im seeing a loss of fuel pressure.
it doesn't make any sense as the injectors should be good enough for this application; and the fd fuel pump has got to be good enough to maintain pressure for an n/a
any thoughts?
Thread Starter
I "lost" my emissions....
Joined: Apr 2005
Posts: 1,764
Likes: 6
From: lillington, nc
Measured fuel pressure last month and it was within spec. I will be installing a shrader valve inline and check at wot in 2nd gear pulls. I cant imagine its dropped in the last couple weeks but anything is possible.
Joined: Mar 2001
Posts: 31,835
Likes: 3,232
From: https://www2.mazda.com/en/100th/
i think what's happening is that the AFM is 100% open, so you can't go richer than that.
you could try a few things.
more fuel pressure, or bigger injectors
you could try a few things.
more fuel pressure, or bigger injectors
If your SAFC is attached as it should and working properly, it sounds like you have a fuel supply or pressure problem.
Did you run the car and watch the fuel pressure? I did this buy buying a 5/16 line adapter with a 1/8 NPT port in it. I got a small mechanical fuel pressure gauge, some extra fuel line and ran it under my windsheild wiper So a friend could watch the fuel pressure as I drove. When I was done i removed the extra line and ran the gauge on the fuel supply line underhood.
If your fuel pressure is good, you can rule out the regulator.
Make sure your secondaries are working, make sure the injectors are clean.
It could also be the fuel pump. IN fact you may want to pull the fuel pump and check the fuel pump prefilter for debris first. If that is clean change the main fuel filter if you havent recently and if that does not work start checking the fuel pressure etc.
Did you run the car and watch the fuel pressure? I did this buy buying a 5/16 line adapter with a 1/8 NPT port in it. I got a small mechanical fuel pressure gauge, some extra fuel line and ran it under my windsheild wiper So a friend could watch the fuel pressure as I drove. When I was done i removed the extra line and ran the gauge on the fuel supply line underhood.
If your fuel pressure is good, you can rule out the regulator.
Make sure your secondaries are working, make sure the injectors are clean.
It could also be the fuel pump. IN fact you may want to pull the fuel pump and check the fuel pump prefilter for debris first. If that is clean change the main fuel filter if you havent recently and if that does not work start checking the fuel pressure etc.
My s5 N/A used to have a similar problem starting at 6300 rpm. My injectors had flow-tested ok and a rebuild did not help.
The secondaries were dropping out just when they were needed most:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/power-drop-noticeable-hesitation-issue-high-6300-rpm-802779/
Start reading at post #19.
"Primary pulse -- starts at 2.6 ms, reaches high of 8.4ms @ 6300 and drops down to 5 ms, staying there all the way to redline.
Secondary pulse -- @ 3500, starts at 5ms, slowly climbs to 6ms, jumps to 11ms and @ 6300 drops to 5ms and then to 0 by 7000."
If you have datalogging capability, it would be helpful in diagnosing the lean condition more precisely.
The secondaries were dropping out just when they were needed most:
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/power-drop-noticeable-hesitation-issue-high-6300-rpm-802779/
Start reading at post #19.
"Primary pulse -- starts at 2.6 ms, reaches high of 8.4ms @ 6300 and drops down to 5 ms, staying there all the way to redline.
Secondary pulse -- @ 3500, starts at 5ms, slowly climbs to 6ms, jumps to 11ms and @ 6300 drops to 5ms and then to 0 by 7000."
If you have datalogging capability, it would be helpful in diagnosing the lean condition more precisely.
Thread
Thread Starter
Forum
Replies
Last Post
Jeff20B
1st Generation Specific (1979-1985)
4
Jun 26, 2016 10:21 AM
smikels
2nd Generation Specific (1986-1992)
3
Aug 18, 2015 01:26 PM