2nd Generation Specific 1986-1992 Discussion

Engine And Fuel Q's

Old 02-02-2004, 12:54 AM
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Hey all,



I just wanted to get some opinions on what "the next step" should be. I'm not looking for the bragging rights or big dyno numbers or whatever, just reliability.



I have a 88 AE, had to replace the engine with a mazda reman. While that was happening, I found out that all of the exhaust was shot/useless/rusted out, so I replaced that. I replaced it with a 2.5" downpipe (no precat) to a hi-flow cat to a 3" pipe (keeping the dual system). Minus the generic cone filter, everything else is stock. So my question is: what is the next step? I'm really focusing on fuel-cut issues right now. I really don't want to replace the engine ... again.



I've been reading about the rtek7 chip upgrade - sounds promising, but there's very little comments, positive or negative, said about it. Also, with any FCDs, the job is to not cut the fuel, so technically the last good number a FCD sends (tricks) the ECU with is just below fuel cut ... while that's good, doesn't that make it so that instead of "no fuel + a lot of air" (which is really bad) it makes the situation now "some fuel + a lot of air (better, but not the best). is there a solution/product or a combination of products that make the best solution (proper fuel + a lot of air)?



I'm also worried about the creep as well. The previous owner put an aftermarket gauge in and the car seems to boost to 6lbs in all gears and all speeds (before I had to replace the engine). I had the car on the road for a little bit. All the way up to 90mph, the gauge had a 6lbs reading. I have no idea if there is a FCD already there - seems like it. If there is, where would he have put it?



Thanks. (sorry for the long post)
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Old 02-02-2004, 01:02 AM
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FCD plug into the boost pressure sensor



look at the little black box on the passenger strut tower...till have a harness clip in it and a vacuum line in it



if it goes straight to the harness then you dont have one



if you have a little box in between the harness and sensor then you have one



if you dont have one , i have a racing beat FCD for sale... im asking 70 shipped...they cost 107 from racing beat...



lemme know and good luck
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Old 02-02-2004, 12:45 PM
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As far as creating a reliable car, I'd focus on maintaining the stock cooling systems. I won't comment on the fuel thing because I've always been n/a so don't have first hand experience.



Make sure that your oil cooler is in good condition (huge importance) and, if you can afford it, replace the lines with braided ones. Breaking a line not only gives a high chance of a blown engine but also makes a ridiculous mess in the engine bay.



The stock cooling system should be adequate for you, provided you flush the system and bleed it well. Here, again, make sure the hoses are good and the radiator is flowing nice.



Investing in the crucial gauges is a good idea too. Beyond boost, I'd say water temp, oil temp, and oil pressure. A/F ratio may be a good idea for you too but it seems like it would tell you you're lean a bit too late to matter (though it would be nice to know). WATCH YOUR TEMP ALWAYS.



For your next move regarding performance, how bout some suspension work? The KYB AGX's are phenomenal for the price and perform really well. Coupled with some decent springs makes a great combo. Brake lines and pads are always a good investment too.



Sorry if these comments are fairly simple, I don't know your level of RX-7 knowledge and it never hurts to mention the basics. Good luck.



Redwood
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Old 02-03-2004, 07:55 AM
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FrestyleFC3S:



Doesn't seem like I have one. A friend of mine is helping me get the car back on the road and he cleaned out a lot of "useless" wires. I think the previous owner had an alarm system so he pulled that out and it looks like it was installed in that area of the car. No FCD to be found. I'm guessing there's no other place possible to install it correct?



I'll keep you in mind for the FCD. Right now we're working on trying to get the idle back to factory spec. It's currently sitting at 1500 and won't come down any more. We're actually going old school and pulling out the factory manuals and see if we missed anything.







Redwood:

The stock cooling system has been replaced with a new one. The oil cooler is stock and the 2 main oil lines are brand new. Oil was leaking from it when I got it, so I replaced them both. Probably when those break, I'll go braided. As for the suspension, I replaced the rear 2 with KYBs while I left the front alone only because I can probably get a little more miles out of them before those die. The back were blown - if you touched the spoiler it would bounce more than a cheap hotel coin-operated vibrating bed. =P.





My main "problems"/concerns are:



* 1500 idle - working on it

* fuel cut

* boost creep
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Old 02-03-2004, 10:38 AM
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for the idle check the thermowax, they like to stick/clog/have airbubbles.



fuel cut is supposed to happen at like 8something psi. if you're holding 6 thats fine, its prolly the cat. also if you're holding 6 psi even in the upper gears that means you're not creeping either, witch is unusual but good.



the way the ecu/fuel cut works is that you can either put a clamp on the pressure sensor circuit or you can put in a chip that limits the pressure sensor circuit. the stock chip isnt writeable, so all fuel cuts work the same, its just either inside or outside of the ecu case.



fcd's can be by the pressure sensor, or by the ecu externally, or it could be chipped
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Old 02-03-2004, 10:47 AM
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As far as fuel goes, you don't need anything more right now. Stock system can support 230-240rwhp safely. If you really want to be on the safe side, just upgrade to a 255lph walbro fuel pump. Once you get beyond that rwhp or roughly 11-12psi the fuel pump and some bigger secondaries are needed. But bigger secondaries require either a standalone or piggyback such as an S-afc.



I would just work on general maintence, fuel filters/plugs/wires/fluids, clean up the grounds etc.



Check the thermowax as J9 mentioned and check to see if the butterflies are jammed. You can also adjust idle by using the air bleed on the firewall side of the throttle body. Its just a screw with a spring behind it. Vacuum leaks also cause a higher idle, that might also explain your low boost in higher gears..
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Old 02-03-2004, 12:34 PM
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Yeah, that idle should be addressed.



It sounds like you know what you're doing with the car so I'd say just keep on doing what you're doing.



Redwood
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Old 02-03-2004, 06:37 PM
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Thanks for the replies.



I'll just keep an eye out on the boost needle for right now until I get something permanent (mechanically or electronically) so I won't have to babysit the gauge.



I was thinking the final solution would be the rtek7 chip and perhaps a safc2. The rtek7 will kill the fuelcut (if it every occured) and i would make the safc2 activate only on the upper range to compensate for the lack of fuel that the ecu/car/engine was not intended to be at. And if not a safc2 .. whatever product that does whatever i described. That's it. That's all i'm looking for.



But again, thanks for the replies.
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