Rotary-Celica

OK
problem 1

I cant get a O2 sensor to last more then a week. Broke a cheapo sheebay special in 3 days and now broke a Bosch sensor in less then a week. They just either read crazy or like now no movement at all. 1st one had a cracked ceramic inside. What brand are you having luck with. My gauge is not a wideband just a autometer air/fuel gauge. The sensor is about 2 feet down stream from the motor and is not damaged or shorted.

problem 2

Tuning the carb. After searching here and reading what everyone was running for jets I deceided to start with RBs recomendations on jetting. But I was running rich on the gauge and black plugs. So I first lowered the fuel bowl level then pressure to 3.5 psi. Still rich, but ran strong and pretty smooth. I leaned out the mains and it ran leaner at top end but still rich at idle. So I changed to smaller idles. My gauge has since broke so I dont know what air fuel ratio is now BUT it now stumbles when I step on the gas but seems to smooth out at mid range. From the *** dyno it dosent seem to pull as hard as when it was rich. I figured it would pull harder as I leaned it out but its not.


Setup
13b 4 port large street port
48IDA with 3rd progression hole mod and fuel bowl mod
40mm venturies
idle jets started at 70s now running 60s
F11 tubes
mains -started 190 now 180
air - what ever Rb said I forget havent adjusted yet
timing locked dist set at 23 deg


Any help suggestions

peejay

You need more timing. 23 is not enough for a 13B.

I used to run 22ish on my 12As. The more port the less timing. The streetport didn't like any more than 20.

My 13B feels pretty damn good with 27 degrees, and it's got honkin' big street ports. Most people run 26 in the pre RX-7 style engines.

Rotary-Celica

Ok I have noticed it hits a meaner brap with the timing up around 27 but I thought it was too much so I turned it back.. Ill turn it back up tomorrow and give it a try.

Tom93R1

iTrader: (2)

In my experience the stumble when you hit the gas is from too lean of a main jet or at the very least needing to richen up the idle mixture screws.

Rotary-Celica

Ok I advanced the timing and now it runs 100% better at low speeds not perfect but much much better. Top speed seems a little flat so tomorrow I will swith the main jets back to the bigger ones to see how it changes it.

Still need some info on what to do about the O2 sensor. Do I need one specificaly for a mazda or should any O2 sensor work??? I would have thought any brand would handle the heat but I could be wrong.

peejay

The one I am using is a 120k mile old 4 wire unit from my coworker's wife's Windstar, after he replaced it with a new one just because he was in there.

I have never had problems with O2 sensors. On the other hand, I only use takeoff OEM units. Before I had the Megasquirt, I had a whole supply of Chrysler units, which have a problem with the heater circuit bleeding through to the sensor wire. (You'll see well over +1v on the signal wire... hmm major clue). I'd just clip off the extra wires and use it as a nonheated unit.

Tom93R1

iTrader: (2)

Crap, I meant too lean of an idle jet. The main jet is probably fine. Sorry

Rotary-Celica

changed mains today I had 170s went up to a 180. Car pulled much nicer felt strong again. With the 170s in the plugs looked a nice shade of dark tan but the 180s pull harder.

I am prob going to swap the 60 idles out for some 65s to see if I can get rid of the last little bit of stumble.

I guess Ill go get another bosch O2 sensor see if it holds up better if not Ill try to get a oem from the junkyard

dj55b

iTrader: (2)

curious do you have some sort of heat sink in there for your O2? One simple method to do so is getting a piece of copper plate and drill a hole in it for the O2 to sit in when you have it on the headers to act as a heat sink. Or if you want to be a little more fance you can go with the root that i went with:

http://images.google.ca/imgres?imgur...%3Den%26sa%3DN

Its pretty pricey i know but you get the idea.

Also Peejay would you be able to share your Timing and AFR target rance for a 12a from your MS. I'm trying to get mine to squeeze out more power, but having a hard time. My timing goes up to 28 degrees actually on my 12a from what BDC gave me when I went to get a tune from him, but today just to give it a try, I increased my bottom end timing and reduced my top end to about 24 i think pulled out some fuel (about 12.7 AFR) and it didn't seem to be as rev happy but could definatly feel better pull in the mid range. I took the car to an industrial test road that I normally go to, before I would always struggle to hit about 120kph before i'm at the end of it, by me just moking things up with your idea I was actually able to hit 130kph fairly easily.

peejay

No idea, I've never tuned for AFRs, just MPH in the 1320!

Same with timing... although I've never played with timing at the dragstrip at all! I did play a lot searching for MPG.