Slow after 5K rpm
07-15-14, 09:31 PM
#1
Slow after 5K rpm
Alrighty!
-85 GSL
-12A carby, stock Nikki
-All stock with exception of air pump being gutted (no vanes, but still in place for appearance/belt on WP reasons) & blocked off air passage to cat (aftermarket cat w/o bung for split air pipe
-former automatic, converted to manual. Vacuum half-re done for manual (no switching valve, or richer solenoid that's specific to the manual. Plumbing up near WP changed to manual spec however.
-Timed correctly per FSM
-secondarys I believe to be working, based on:
1) spring linkage on rear of carb is all hooked up/assembled as should be.
2) secondaries are smooth operating by hand, & not binding. depressing throttle 100% makes them open ~1/3 the way open
3) vacuum actuation diaphram working, via the remove, and close port & see if lever holds test.
-High 7's (bar) @ 315 RPM all faces compression via mazda compression tester.
-stock exhaust w/ exception of catalytic section being replaced w/ aftermarket cats. Appeared clear & un-obstructing on inspection during manual swap
-I did seafoam the car & that seemed to help. I also removed the OMP in favor of premixing as I prefer it for lubrication purposes.
Here's what IS wrong, or yet to be addressed
-leaky carb body, saturated looking, especially around accelerator pump/lower base flange of carb
-haven't yet changed fuel filter. Haven't inspected inside of tank, or pump. Also don't know fuel pressure. All these are on-the-list.
-haven't opened carb, but DO intend to unless it's an easier fix
My symptoms, is the car is just plane sluggish after about 5k, or around the time the secondaries come fully online. I mean good lord, you're just watching the rpms creeeeeeeeeeep up to redline, it's sooo painfully slow. It's like, first gen RX7 up until 5k, and then, geo metro from that point onwards.
I hope I've provided enough info to at least steer me in the next directions. It's definitely GETTING THERE, but some guidance would help as I'm much more keen on the 86+ EFI systems for now. haha
Thanks!
Landon
-85 GSL
-12A carby, stock Nikki
-All stock with exception of air pump being gutted (no vanes, but still in place for appearance/belt on WP reasons) & blocked off air passage to cat (aftermarket cat w/o bung for split air pipe
-former automatic, converted to manual. Vacuum half-re done for manual (no switching valve, or richer solenoid that's specific to the manual. Plumbing up near WP changed to manual spec however.
-Timed correctly per FSM
-secondarys I believe to be working, based on:
1) spring linkage on rear of carb is all hooked up/assembled as should be.
2) secondaries are smooth operating by hand, & not binding. depressing throttle 100% makes them open ~1/3 the way open
3) vacuum actuation diaphram working, via the remove, and close port & see if lever holds test.
-High 7's (bar) @ 315 RPM all faces compression via mazda compression tester.
-stock exhaust w/ exception of catalytic section being replaced w/ aftermarket cats. Appeared clear & un-obstructing on inspection during manual swap
-I did seafoam the car & that seemed to help. I also removed the OMP in favor of premixing as I prefer it for lubrication purposes.
Here's what IS wrong, or yet to be addressed
-leaky carb body, saturated looking, especially around accelerator pump/lower base flange of carb
-haven't yet changed fuel filter. Haven't inspected inside of tank, or pump. Also don't know fuel pressure. All these are on-the-list.
-haven't opened carb, but DO intend to unless it's an easier fix
My symptoms, is the car is just plane sluggish after about 5k, or around the time the secondaries come fully online. I mean good lord, you're just watching the rpms creeeeeeeeeeep up to redline, it's sooo painfully slow. It's like, first gen RX7 up until 5k, and then, geo metro from that point onwards.
I hope I've provided enough info to at least steer me in the next directions. It's definitely GETTING THERE, but some guidance would help as I'm much more keen on the 86+ EFI systems for now. haha
Thanks!
Landon
07-16-14, 09:57 AM
#3
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well if you have ruled out any physical obstruction, plugged exhaust, etc then it is either a spark or fuel problem.
step 1; is to change the fuel filter, the fuel system doesn't have a lot of margin, so a small restriction at the fuel filter is a big deal.
step 2; i like to look at the ignition. spark plugs should be newish. cap and rotor should be perfect. check the wires, i think the spec is 7k ohms, new wires are like 3.5k, the higher the resistance = less spark energy.
step 3: usually not needed!
step 1; is to change the fuel filter, the fuel system doesn't have a lot of margin, so a small restriction at the fuel filter is a big deal.
step 2; i like to look at the ignition. spark plugs should be newish. cap and rotor should be perfect. check the wires, i think the spec is 7k ohms, new wires are like 3.5k, the higher the resistance = less spark energy.
step 3: usually not needed!
07-17-14, 09:55 AM
#6
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07-17-14, 10:01 AM
#7
Keep in mind, stock secondaries do NOT open based on RPM, they open based on the combination of engine load (controlled by vacuum) & throttle position. May be that they are not opening fully due to a binding linkage, or not staying open due to a leak in the diaphragm as noted above. Real hard to judge what they are doing since there's no easy way you can see them work under load conditions.
Wiring them to open mechanically will insure they will open, but they will do so every time you stroke the throttle regardless of need, and your gas mileage will fall pretty dramatically.
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07-17-14, 01:57 PM
#8
My wiring the secondaries suggestion was as a way to see if the secondaries are indeed opening.
If they do, with the wire, it's a confirmation of the diaphragm leaking.
That said, using only the throttle return spring without the emergency return spring, my throttle is very light and offers some resistance at full primary. It's like having an easily useable switch for the secondaries. Which I like.
If they do, with the wire, it's a confirmation of the diaphragm leaking.
That said, using only the throttle return spring without the emergency return spring, my throttle is very light and offers some resistance at full primary. It's like having an easily useable switch for the secondaries. Which I like.
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