Overfueling
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Mathew
Overfueling
hey Lou, how did you fix the overfueling problem on your car. I think thats causing some of my problems. can the superchargers fuel setup be adjusted to give less fuel at startup/low revs, without affecting the fuel flow at high revs?.
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Lou Girardin
Overfueling
Hi Matt,
I'm not sure about your set-up. Mine has an AFPR that's adjustable to change
fuel pressure under boost. I don't remember if your's has that fitted. If
so, fuel pressure should be 48 to 52 psi at idle, raising to 75 psi at 6lbs
boost. This with stock injectors, with 1.8's the pressure needs to be lower.
I've heard 35 to 40 psi at idle. While on the subject, it's a good idea to
replace the fuel filter once a year. You do have 1.8 injectors though and on
normal JRSC's they will cause overfueling at idle or lean at the top end,
depending on fuel pressure. Unless there has been some kind of compensation
made for this, the normal solution is to fit an '86 - '88 RX7 air/flow
meter. This has the extra benefit of giving increased air flow at high revs.
There's lots of info on Miata Forum.Net
Having said all this, I don't see the point of 1.8 injectors unless you're
running over 7psi boost. With WI mine goes to 7.5 psi, I've never had a
problem with leaning out including track days, etc.
Good Luck
Lou
I'm not sure about your set-up. Mine has an AFPR that's adjustable to change
fuel pressure under boost. I don't remember if your's has that fitted. If
so, fuel pressure should be 48 to 52 psi at idle, raising to 75 psi at 6lbs
boost. This with stock injectors, with 1.8's the pressure needs to be lower.
I've heard 35 to 40 psi at idle. While on the subject, it's a good idea to
replace the fuel filter once a year. You do have 1.8 injectors though and on
normal JRSC's they will cause overfueling at idle or lean at the top end,
depending on fuel pressure. Unless there has been some kind of compensation
made for this, the normal solution is to fit an '86 - '88 RX7 air/flow
meter. This has the extra benefit of giving increased air flow at high revs.
There's lots of info on Miata Forum.Net
Having said all this, I don't see the point of 1.8 injectors unless you're
running over 7psi boost. With WI mine goes to 7.5 psi, I've never had a
problem with leaning out including track days, etc.
Good Luck
Lou
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Ray
Overfueling
Matt
although i agree with Lou on the fuel pressure, i feel that they do need the 1800
injectors, because they do run lean in the midrange on full throttle acceleration,
on of the reasons Lou fitted his home made WI, which works very well, on our very
first track day at Pukekohe both Lou and myself were getting overheating problems
after 5 laps and i put it down to them running lean, and i put this down to adding
the non return valve to the idle hose which gives more boost,if you want your car
to idle better and run smoother remove the 1800 injectors and the non-return valve
set the timing to 8 degrees and your problems will be solved, albeit a loss of performance,
bare in mind that Lou and i also run J&S knock sensors which gives you better control
over your timing, i also dont think adding the RX7 air flow meter will solve your
problems as i think they will return to the lean situation again, if you stick to
the original Sebring set-up you will not have any problems, i didn't for three years
untill i added the non-return valve, and thats when everybody started getting problems.
Ray
[...]
although i agree with Lou on the fuel pressure, i feel that they do need the 1800
injectors, because they do run lean in the midrange on full throttle acceleration,
on of the reasons Lou fitted his home made WI, which works very well, on our very
first track day at Pukekohe both Lou and myself were getting overheating problems
after 5 laps and i put it down to them running lean, and i put this down to adding
the non return valve to the idle hose which gives more boost,if you want your car
to idle better and run smoother remove the 1800 injectors and the non-return valve
set the timing to 8 degrees and your problems will be solved, albeit a loss of performance,
bare in mind that Lou and i also run J&S knock sensors which gives you better control
over your timing, i also dont think adding the RX7 air flow meter will solve your
problems as i think they will return to the lean situation again, if you stick to
the original Sebring set-up you will not have any problems, i didn't for three years
untill i added the non-return valve, and thats when everybody started getting problems.
Ray
[...]
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Lou Girardin
Overfueling
Phew! Thats a stack of queries.
!st, I have no leaning out probs according to an A/F ratio check I have
done. I still run the check valve and see 7.5 psi boost.
My overheating was caused by the location of the reg plate, it hasn't
occurred since, under any conditions. The J&S does protect against
detonation, but it never triggers with WI fitted. I fitted both to allow me
to run 14 degrees advance which boosts low RPM power considerably, 1 - 1.5
secs quicker from 80 - 110 km/h in 5th. One thing to remember is that the
JRSC is designed as a package, at 6 - 6.5 psi there is no need for other add
on's for reliable running
An AFPR is boost dependant, it raises fuel pressure 6psi per 1 psi of boost.
No boost = no pressure rise. This is why 1.8 injectors overfuel at idle
where the fuel pressure is controlled by the Mazda regulator, lower fuel
pressure with these injectors corrects the mixture under boost An RX7 AFM
compenstes for overfuling at idle when the flapper wheel is altered 1 - 3
clicks from stock. This is not that difficult, many owners have done it with
success.
The stock ECU will only cope with injectors up to 270cc, over that you need
add-on engine management.These control the injectors, not fuel pressure, a
relatively low cost ignition control unit is the Bipes ACU @ $US200, it's
had good reports. Dick Bipes is also working on a fuel control system too.
Hope this helps.
Lou
!st, I have no leaning out probs according to an A/F ratio check I have
done. I still run the check valve and see 7.5 psi boost.
My overheating was caused by the location of the reg plate, it hasn't
occurred since, under any conditions. The J&S does protect against
detonation, but it never triggers with WI fitted. I fitted both to allow me
to run 14 degrees advance which boosts low RPM power considerably, 1 - 1.5
secs quicker from 80 - 110 km/h in 5th. One thing to remember is that the
JRSC is designed as a package, at 6 - 6.5 psi there is no need for other add
on's for reliable running
An AFPR is boost dependant, it raises fuel pressure 6psi per 1 psi of boost.
No boost = no pressure rise. This is why 1.8 injectors overfuel at idle
where the fuel pressure is controlled by the Mazda regulator, lower fuel
pressure with these injectors corrects the mixture under boost An RX7 AFM
compenstes for overfuling at idle when the flapper wheel is altered 1 - 3
clicks from stock. This is not that difficult, many owners have done it with
success.
The stock ECU will only cope with injectors up to 270cc, over that you need
add-on engine management.These control the injectors, not fuel pressure, a
relatively low cost ignition control unit is the Bipes ACU @ $US200, it's
had good reports. Dick Bipes is also working on a fuel control system too.
Hope this helps.
Lou
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Mathew
Overfueling
Mucho thanks to Fletch (the Miata Messiah), Lou and Ray for the very helpful Info. I can't afford to get a link computer to run the 1800 injectors properly, and if I install the RX7 air flow meter I'll have to get my custom K&N filter mount remade so I think the easiest option might be to source some 1600 injectors and give them a go.
Have you guys heard anything bad about the MSD ignition control unit. There is a version specifically for Sebring Miata's which seems to do whats needed, yet costs less than half of what you'd pay for the J&S.
Cheers
Matt
Have you guys heard anything bad about the MSD ignition control unit. There is a version specifically for Sebring Miata's which seems to do whats needed, yet costs less than half of what you'd pay for the J&S.
Cheers
Matt
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Ray
Overfueling
Matt
when you get round to the 1600 injectors dont forget to adjust the AFPR pressure
for the 1600 injectors, the pressure that Lou quoted, and also disconnect the battery
and either turn on the headlights or leave overnight before connecting, to reset
the ECU, you could also consider WI, Lou will let you know how its done, his cost
about $100 i think, a cheap safeguard, that way you can run your timing at 10 degrees,
without i would set the timing at 8 degrees to stop any detonation.
the MSD unit is supposed to work fine, i feel its not needed with a basic Sebring
setup, its good if your running much higher boost pressures.
Ray
I install the RX7 air flow meter I'll have to get my custom K&N filter mount remade
so I think the easiest option might be to source some 1600 injectors and give them
a go.
less than half of what you'd pay for the J&S.
[...]
when you get round to the 1600 injectors dont forget to adjust the AFPR pressure
for the 1600 injectors, the pressure that Lou quoted, and also disconnect the battery
and either turn on the headlights or leave overnight before connecting, to reset
the ECU, you could also consider WI, Lou will let you know how its done, his cost
about $100 i think, a cheap safeguard, that way you can run your timing at 10 degrees,
without i would set the timing at 8 degrees to stop any detonation.
the MSD unit is supposed to work fine, i feel its not needed with a basic Sebring
setup, its good if your running much higher boost pressures.
Ray
I can't afford to get a link computer to run the 1800 injectors properly, and ifMucho thanks to Fletch (the Miata Messiah), Lou and Ray for the very helpful Info.
I install the RX7 air flow meter I'll have to get my custom K&N filter mount remade
so I think the easiest option might be to source some 1600 injectors and give them
a go.
version specifically for Sebring Miata's which seems to do whats needed, yet costsHave you guys heard anything bad about the MSD ignition control unit. There is a
less than half of what you'd pay for the J&S.
[...]
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Fletcher Blades
Overfueling
Matt,
If you want to try the RX-7 AFM, you wont have to change the adapter that
much... its mounting holes/bolts are the same spacing... you just have to
widen the air-flow hole a bit... This does of course mean you need some
strategy to close it back up again if you decide to go back...
Fletch.
If you want to try the RX-7 AFM, you wont have to change the adapter that
much... its mounting holes/bolts are the same spacing... you just have to
widen the air-flow hole a bit... This does of course mean you need some
strategy to close it back up again if you decide to go back...
Fletch.
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