Pulled out some fuel in 5,6,7,8k rpm ranges, brought down o2 reading from .95 after transition to .89. Man, what a differnce, it is amazing. ALso, my inj. duty down, (obviously) to like 89.5 at redline. I love it. I can't wait to do it right on a dyno. Tyres broke loose at like 5k in 1st, squelled a bit into 2nd, then grabbed, it was nuts.

Are there any drawbacks to using PIM volt menu. It seems maybe it would be advantage becaue it takes out fuel at partial throttle too, or am I asking for trouble in long-run by doing it this way?

 

You can use the PIM two ways. One is like you did by adjusting fuel by RPM. This is a fast way to adjust for dyno or O2 on the street. As you seen, it also affects off boost. What you can do is run the dyno at a low boost like 10PSI and also at a high boost like 12+ using this to adjust fuel and record the values. Afterwards, you can go to those fuel cells and make the corrections there so they can be removed from the PIM. This is the hard way but is most accurate.

Another way is to not use the PIM RPM, but use the PIM MAP SENSOR VOLTAGE. This changes fuel based on boost. The RX-7 manual does not give a good mapping of this. You will have to first "MAP" the output voltage of it to boost pressure. You can do this by using a hand air pump connected to the sensor and boost gauge through a one way valve. Connect a high impendance voltmeter to the sensor output. As you increase pressure (look at boost gauge) record the voltage output. From this you can draw a graph of boost vs voltage. Then when you go into the PIM VOLTAGE map which lists voltage, you will know what boost corresponds to that point.

By using all three(1) INJECTOR CELLS, (2) PIM RPM, and (3) PIM VOLTAGE; you can fine tune your
engine.

 

great information, thanks a lot.

 

Pardon my ignorance.. Whats a PIM ??

 

The manual does not define what PIM stands for, but the PIM screen is used to adjust/change fuel (injector pulse width) by steps of 1000 RPM and/or MAP sensor voltage(boost).

 

Ok, I'm pulling some fuel out and have some questions before I go much farther.

I know the o2 should not go below .82 or so and I plan on getting mine to about .87 but is that at WOT only? What about cruising? Is it ok to dip below .82 while cruising as long as I'm in the mid/high 80's while at WOT or what?

I'm only pulling fuel from 4K - 8K. So far I have all those field down to 82% (cant remember the exact number) and I'm still in the low to mid 90's but it has come down from where it was, which was high 90's. My question is how far have you gone down with yours and what boost are you running???

My next question is about the "next" screen that shows the PIM voltage and has 100% next to it. The manual says that lowering the % will lessen the Basic Fuel Injection amount. What exactly does this mean??? Should I mess with it? All of my volts are at 100%

My very last question (I promise ) is about the O2 reading. Have you guys ever noticed at say 5K rpms for example under light throttle seeing low O2 reading like 70's, 50's ect for a split mili second? Its like its staying around 90's but jumps to something real low then back in the blink of an eye. Is this ok and normal or does it mean that for a split mili second I'm running lean? I'm assuming its basically the same as when you totally remove your foot from the gas and it drops to 0 or close but I just want to make sure its ok.

I think that gets it.

 

I think I lowered mine to 88.8, and tick higher at redline.

if you are down to 80 that is a lot of fuel out. I am running .90kg/cm2

I really don;t know much more to help you, I am new to this thing as well. I am sure cewrx7r1 wil chime in, he knows his **** on PFC.

 

What O2 readings do you get while cruising?

You know what, I bet the reason I have to dial so much more out is because I'm using a XS Engineering base map. They tuned everything for me and then he said I would prefer to add alot of extra fuel and have me just pull some out till it looks good and I agreed that would be best since his map is from a dyno tuned car and is very fine tuned.....all car are different so maybe it would have been to lean for me.

Anyway, thats probably why I'm having to pull more fuel. I didnt think about that.

Thanks,
STEPHEN

 

Well, I might have just answered my own question about the o2 reading being borderline in the low 80's at partial throttle and high 80's during WOT. I think the partial throttle does make a difference. I just pulled up to a stop sign and my idle is rock solid at 900 but my engine is lumpy. I think i blew a apex seal

BTW - at WOT it NEVER went below .89 but that using the stock POS o2 sensor, maybe it just didnt sence it. Oh yea, my PIM was at 83.? between 4K and 8K

Damn

PS - Hopefully I'm wrong about this but I have a bad feeling that I'm not

Later,

 

How lumpy? Does the car really shake? Before you panic, check your hoses for any air leaks. Have you lost alot of vacuum at idle?

What are your O2 readings at idle?

You might want to have someone drive your car while you watch the commander and take notes. Tell the driver how you want him to drive and record what you see. It does sound like you pulled alot of fuel. I think XS changes the base map first; cause they can!

I would definitely call XS, especially if they said it was ok to pull out some fuel.

 

spautos, did you ever notice a worthwhile gain in power while leaning it out? i pulled fuel out of individual cells in the inj map and didn't notice any difference. i took out around 10pts without noticing a change at which point i chickened out using the stock 02.

if i remember right, the base map is way more aggresive at light boost levels. wouldn't that make using the pim voltage through an entire rev range dangerous for the normal base map. if someone is pulling out fuel for 4k+ RPM at WOT, they'd be in dangerous teritory anytime they're at part throttle above 4k.

 

Okay this is going to sound pretty dumb but where do I find my O2 readings on my comander? Sorry new to this programming stuff.

 

to check o2 sensor readings, go to the etc. menu and open the sensor window. it shows all the sensors readings and which ones are operating or are off.

 

Ok guys, here is the deal, my o2 reading were fine and yes pulling fuel out made a HUGE difference. That being said, i dont think anyone should try to tune thier own car unless you have tuned before and REALLY REALLY REALLY know what your doing!!!! I was watching my o2's but that isnt enough. If you dont have a GOOD o2 like a wideband AND a egt gauge I dont think you can really tune your car and know for sure whats going on. The relationship between timing and a/f is one that I'm not ENTIRELY familiar with and if you arent either I suggest you dont try to tune your own car. I dont know exactly what caused my problem (not sure if its a/f ro timing or what) but I put everything back to where it was so I dont blow my new engine. I'm going to be posting tuning questions in the big single turbo section because thats where all the major tuning gurus hang out, some of you guys might want to keep up with it so we can learn exactly how all this works together.

At least my car is still running ok, hopefully it will last till next weekend when I can rebuild it. Port job here I come!!!!

Later,

 

a/f ratios have little to do with timming, much less than boost, porting, and lack of intake and exhaust restrictions. As the more volatile the the mixture becomes ie more air(porting, inatek, more boost) the more you must retard the ignition to get maximum power.

 

A/F ratio only insures that you have the correct amount of fuel for the amount of air being burned in the engine for a given rpm and boost. You can still blow the engine due to incorrect timing or too high of temperature for the intake charge. To measure A/F ratio correctly, you need a very good linear O2 sensor that is calibrated to it's monitor. Using the stock O2 sensor will only provide a very rough assumption of correct A/F ratio.

Back in the days when the PFS PMC was popular, the rule was to tune for a range of .86 to .9 volts. This would normally give a safe A/F if the timing was correctly retarded.

Timing will not have a noticeably affect on the A/F ratio. The mixture will always burn the same. Too much timing advance will only blow the engine or cause loss of power due to the peak combustion pressure occurring too soon. This will also cause lower exhaust temps because the mixture burns earlier and the engine absorbs more of it's heat. Too little timing advance will cause loss of power due to late peak pressure and the mixture could still be burning as its exits the exhaust. This will cause higher exhaust temps.


Richer A/F ratios are used to compensate for too much advance or high intake temps. Most ECUs are programmed with extra retard and rich fuel to make it safe of the average engine. If you have a fuel system that can safely handle your engines max fuel requirements, an ignition system that will always fire the mixture, and a large enough IC, then you can really start to power tune.

A weak ignition system can cause some misfiring under high loads which will in turn cause a false lower A/F reading when in reality the A/F could be high.

Some people tune for about 12.1 A/F with confidence and others stay down in the 11.5 to 11.8 safer range. The leaner mixture will give more power.

 

I heard this from another source as well. I do have a question about it though and maybe you can answer it. My understanding is if you have a egt gauge that reads C you shouldn't go over about 850C or so because its too high. Your saying that lower egt's are bad for the engine because that means it retaining heat. I dont really understand this. I understand what your saying and it makes sence but I dont understand why high egt's are bad if this is the case. Seems like low egt's would be whats bad not high egt's

Can you please explain that???

Most people here are like me and they are simply trying to learn and get thier car tuned by themselves, most (like me) have inadequate equipment and knowledge about the fine points of tuning. I still feel like my recomendation about not tuning yourself unless you REALLY know what your doing and unless you have the proper equipment stands as a valid recomendation and I hope people listen to it!!!!!! I think everyone tuning themselves needs a good o2 (if not a wideband) and a egt gauge. Even with the proper gauges you still need to REALLY research the fine points of of tuning and the in's and out's of how everything works together.

BTW - based on a crude compression test, I'm getting inconsistant reading from 2 of the 3 faces on my rear rotor.....you know what that means......low compression ie bad seal

Later,

Later,

 

I agree with you about tuning our engines by ourselfs. The most effective tuning that most of us including me can do, is adjust the fuel. This can be done on a dyno or the street. If on the dyno, use 4th gear so as to load up the turbos more. And you need a good linear O2 sensor. Safer to stay in the mid to high 11s.

Further tuning will require much dyno time with small incremental changes in timing and measuring egt. That reduction in egt that I mentioned is small in comparison to an incresae caused by not enough of advance.

High egts will weaken exhaust system and turbo components. Higher temps weaken all materials components. If the timing is too retarded, the exhaust gases can still be burning as they exit the exhaust port. This causes the highest egt and can act as an afterburner and over spool the turbo/s. But then these are extremes.

 

Hey Chuck,

I have a copy of your latest map (I think) and have been using both of the timing ones for a little while now. I had only briefly looked at your fuel map however and in doing so right now have come up with a question for you.

- Your correction values do correspond with others I have seen but in doing the actual A/F conversions seem to think they are way too RICH? The values you have up top ie.. 1.41~1.49 are in the high 9.7 to 10.3 range. Is there a reason why you run so rich because I have not seen any posts telling others about it if that's the case.

I have created a map that goes as rich as 10.5 which yields a correction value of 1.388. Maybe I am missing something here?

I have attached my fuel map for your amusement. Please look it over and let me know if anything appears to lean/risky.

Thanks,
Rob

 

I have run three A/F tests so far since getting the PFC preprogrammed by Ray. These were done before I replaced the hi-flow cat with a MP and replaced the 850 injector with 1200s. The first was with the stock O2 sensor setting fuel for .87v like was done in the PMC days. This test said I needed as much as 6% more full from 4-8Krpm. The car ran OK after this but felt a little more sluggish. Then I paid $75 to use a local shop's linear 5 wire Bosch sensor. It said I need an additional 3% for a total of 9% over original values. The car ran crappy after this. Then I went to a local "Honda" dyno shop who has a O2 sensor hooked up to their dyno and computer. The first run was with the 9% extra. O2 read 11.2. For the next two runs I lowered fuel back to the 6% extra level. HP went up and the O2 increased to 11.3. Looking at the O2 graph, I realized it was not a good sensor either. It's reaction time to A/F changes was too slow to give accurate readings. So I went back to Ray's original fuel settings. The car ran so much better.

Since then and going to the MP and 1200s, I have changed my fuel by analyzing all fuel maps posted for cars with similar mods. As I have stated previously, I am waiting arrival of a professional UEGO $1200+ O2 system to tune my car with since only crap is available locally here in Houston.

Unless you know the true base maps of a PFC, I do not think you can accurately calculate A/F from the fuel correction maps. The oringinal maps were based on the air flow characteristics of the stock engine. When the UEGO tests are done, I will dyno my car again and post all relative data.

 

Stephen,

About the O2 sensor at cruise, its in closed loop, so it will jump around from low to high numbers as it tries to maintain lean run conditions for fuel economy.

BTW, taking that much fuel out in the PIM maps will cause the car to run lean under closed loop, making the ecu try to compensate for the fact less fuel is being squirted by the injectors for each pulse. Althou you did say it was from 4k to 8k in the PIM scetion. Cruising is normally 2500 to 3000 rpms. But when you are starting from a stop, with some boost, you might shift around the 5K range as you accelerate under light to moderate boost. If so, from 4 to whatever rpm you shift at under mild boost is running it lean somewhat.

Using the PIM section to tune is alittle risky for that reason. I still maintain that using the map tracer to find out what cells you are in at WOT and then adjusting them to get to the .9 or whatever you feel comfortable with is the way to go. I did that and brought my O2 reading numbers from 1.17 down to point .94 to .96 during wot. I used the PIM map actually in the low range taking out only 2 percent from 3K to 4k. I took out more initially and like I said above, I could feel the car surge as it tried to compensate for the fuel being taken out in the low range while I was cruising.

Stephen, What where the compression numbers? Whats it vac (17?) at idle?
Tim Benton

 

My vac was right at 17, now its about 12.

I dont know exactly what my compression #'s are. I didnt use the Mazda compression tester. I just used a tester that didnt have a hold feature and watched for 3 bounces that were similar in readings. I would consistantly get one high bounce and then 2 low bounces. This was on the rear rotor. You could here it in the motor as it was spinning. It would sounds different when I got low readings versus when it got the high reading.

Its definatly shot. Hopefully I'll rebuilding it this weekend with the help from a good friend. Actually it'll probably be more like me helping him hehe

Later,

 

Sorry to hear that Stephen,

Let us know how the engine looks when you tear it apart. What kind of oil have you been using?

Later,

Attila

 

Yea, I plan on looking at all that and seeing how my oil is doing. I use Valvoline 20/50 racing oil and I also use Pettit Racing fuel additive about everyother tank. For coolant I use distilled water and redline water wetter (in the winter I add some antifreeze to it)

I'm hoping everything will be good, I dont want to replace any housings!!!!

My car only has 38,000 miles so it shouldnt be worn unless that broke seal hurt something.......I'm hoping it just cracked intead of breaking.

Later,
STEPHEN

 

To Rob (SilverR2),

I tried mailing you directly but you are not set up for that.
Contact me directly at cewrx7r1@yahoo.com.

Want to discuss your and my maps.