fuel injection to carb conversion
09-04-01, 10:03 PM
#1
fuel injection to carb conversion
I am converting a fuel injected motor from an 87 rx7 to carbuerrated. I am putting on the Weber side draft carbs, useing stock lower intake manifold and Weber upper manifold. I have a couple questions...
1) What is the best way to plug the fuel injector holes? There are no threads so brass plugs won't work too well. should I find something that is close to the same size and jbweld whatever that is I find into the holes?
2) This is going into a REPU and I had to use the front cover off the 12a that was already in the truck. The oil metering pump hookups on the 87 front cover will not bolt to the 12a front cover which only has 2 oil line outlets. Will I have problems if I just pull 2 of the oil injectors or should I find some kind of line splitter and rig something to get oil to all 4? Should I just eliminate the oil injection and add a little oil to the tank every time I fill up?
1) What is the best way to plug the fuel injector holes? There are no threads so brass plugs won't work too well. should I find something that is close to the same size and jbweld whatever that is I find into the holes?
2) This is going into a REPU and I had to use the front cover off the 12a that was already in the truck. The oil metering pump hookups on the 87 front cover will not bolt to the 12a front cover which only has 2 oil line outlets. Will I have problems if I just pull 2 of the oil injectors or should I find some kind of line splitter and rig something to get oil to all 4? Should I just eliminate the oil injection and add a little oil to the tank every time I fill up?
09-05-01, 09:57 AM
#2
I'm not a Midget!
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I was using an ’86 13B with Webber 45DCOE carb, so I am familiar with this setup. Blew apex seal last month, so I’m in the process of re-building…
1) Racing Beat sells an injector block off kit. I think it was about $20. Nice turned aluminum rods with o-ring seals and mounting plate. Mazdatrix also sells the Racing Beat part.
If you want to go the cheap route and have the stock injectors and fuel rail, just leave the injectors in there. You may have to grind part of the fuel rail away to clear the carb.
Don’t use JB weld! I would not trust the stuff to stay there and not fall directly into the port.
2) You have 2 options: a) get an ‘84-85 GSL-SE front cover that uses the 4 port oil metering pump (OMP). You will also need the GSL-SE oil pan and oil pick up tube.
b) get a 2 port OMP to use on the 12A front cover. Block off the oil injectors and run the OMP lines to the carb bowl.
I went with option “a” above when I converted my motor. I think you will need the GSL-SE oil pan and pick up for either, but I’m not sure.
1) Racing Beat sells an injector block off kit. I think it was about $20. Nice turned aluminum rods with o-ring seals and mounting plate. Mazdatrix also sells the Racing Beat part.
If you want to go the cheap route and have the stock injectors and fuel rail, just leave the injectors in there. You may have to grind part of the fuel rail away to clear the carb.
Don’t use JB weld! I would not trust the stuff to stay there and not fall directly into the port.
2) You have 2 options: a) get an ‘84-85 GSL-SE front cover that uses the 4 port oil metering pump (OMP). You will also need the GSL-SE oil pan and oil pick up tube.
b) get a 2 port OMP to use on the 12A front cover. Block off the oil injectors and run the OMP lines to the carb bowl.
I went with option “a” above when I converted my motor. I think you will need the GSL-SE oil pan and pick up for either, but I’m not sure.
09-05-01, 01:33 PM
#4
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About 30lbs less weight, and a lot less to go wrong. Better flow. Most of the sensors used in the FI system cost as much as my carb did.
I'm "old school" and prefer to have something to play with without needing a laptop.
My$.02
oh - the Mazda FI system would not fit under the hood. It is too tall.
I'm "old school" and prefer to have something to play with without needing a laptop.
My$.02
oh - the Mazda FI system would not fit under the hood. It is too tall.
09-05-01, 01:41 PM
#5
Formula Mazda Driver
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I'm sure there is no definitive answer here...but realistically, can you get as much power on a carb system? I don't mean all out, how much can you spend power, but pretty much stock efi vs. stock carb, which is gonna provide more power?
09-05-01, 04:33 PM
#6
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Top end power will be the same if the flow is kept constant between the two. All either one does is introduce a air/fuel mix to the motor. However, I've been told (I don't have a flow bench) that the carb will flow more that the FI intake system.
The advantage to FI is that it is more accurate at ALL throttle settings, where as the carb comes close, but is really usually tuned to only one band for power (low end, mid, or high end). For racing, it should not make a difference. On the street, the FI will probably run better and be easier to tune (damn, I said it...)
The advantage to FI is that it is more accurate at ALL throttle settings, where as the carb comes close, but is really usually tuned to only one band for power (low end, mid, or high end). For racing, it should not make a difference. On the street, the FI will probably run better and be easier to tune (damn, I said it...)
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