tarek001

Hi guys, I've been reading these forums for a while but finally made an account to get some help with an issue I'm having.

Im trying to figure out exactly whats causing my AFR to reach 20!
Ive changed my coils and spark plugs twice in less than 20,000kms (I've also bought BHR coils which I'm waiting to receive).

Initially i though it was a coil issue but after running some logs and looking at the results it seems as the issue is possibly related to something else. Currently my O2 sensor apparently has a stuck signal (so this could also be causing issues?)

From the provided log would the fuel pump be the most likely issue or am i missing something here?

I've narrowed down the possible causes of AFR hitting 20 from the items below.

-Fuel Pump
-Injectors
-MAF
-ESS
-Rear O2 sensor

Any help would greatly be appreciated. Ill be cleaning the MAF and ESS tomorrow or the day after to eliminate those possibilities as soon as i can.

edit additional info:
2004 SI RX8 Manual 177kw
run BP Ultimate 98 octane
Items below were done @ 81,000km car has now done 97,000kms
Engine rebuilt with steel apex seals
Excedy clutch
Replaced rear O2 sensor because the original had failed
Replaced CAT

I got the Steel apex seals etc because i was thinking of 'turboing' this car (but have decided against this haha)

wcs

iTrader: (2)

I'm going with your foot is off the gas

tarek001

that would be quite a blonde moment ><
excuse my stupidity!
Ill just wait for the new coils and test with them to see if it gets rid of the misfire issue.

thanks

wcs

iTrader: (2)

You need to add engine load to your log and throttle

tarek001

I've now added both those PIDs to the log.
Would it matter whether its absolute engine load or just engine load? (added both anyway)

Ill try get a run with those new PIDs included later on today

thanks for the help so far

tarek001

After doing a run everything looks ok to me except my MAF reading seems low at idle.
I'm still getting misfires but ill be able to sort that out soon.

I've removed a lot of other options i was logging from the excel file and will do a run tomorrow with less inputs as it seems to have slowed down the amount of data pulled (as it repeats quite often).

The blue highlighted section is a small run in first then 2nd gear.
would the low MAF reading at idle and 6.25/ 3.25 LTFT point to a vacum leak? or would the LTFT values have to be higher for that to be the case?

wcs

iTrader: (2)

You're bang on about the polling of data,

Maf readings at idle aren't bad
5 g/s is the "goal" but if it idles screw it.

You're pulling 205 g/s at 8k rpm that's a healthy number.
Running rich but that expected from the stock tune.
The LTFT is ok anything between +3 to -3 is good.
You're at +6 in spots, not bad for a untuned car.
When or if it gets up around 20 you need to figure something is broke.

Unless you have a check engine light on ....

tarek001

Yes i do have CEL on because of the Misfires and stuck O2 sensor! (so it could very well be the cause of these issues)
I was actually expecting the BHR coils to be delivered already but customs kept them for 2 days :/
I've ordered a new rear NTK O2 sensor but i wont be getting that for 2-3 weeks unfortunately.

The 20 AFR seems to only happen after i lift off the throttle, so I'm not sure if that's common or not (I'm assuming it is after you pointed it out in the previous log)

wcs

iTrader: (2)

Bah rear O2 sensor is for catalyst efficiency it aint doing nothing to your LTFT

Misfires are almost coils.

Go turbo...

tarek001

Yeah i figured as much initially but decided that it couldn't hurt to replace it anyway. The main reason I'm looking at other issues is because the coils have failed twice in under 20,000kms. This will be my 3rd set (and hopefully final set).


After reading up on the forums about all the trouble with turbos and what not I'm not sure ill have the time with my new job starting in 2 weeks. I can buy a decent car to get me to and from work or i can get something like a 2010 lancer and put the difference (assuming 10-12k) into adding a turbo to the rx8, but like i said the main issue is time.

You've definitely been a great help!
many thanks.

Roytary

20 afr is damn lean, somethings wrong for sure. If your maf is right, o2 sensor or sensors might be responsible.
What wcs meant by his response was ... wankels and 2 strokes are kinda alike ... they need a little ''throttle bumb'' once in awhile to give em' something to drink on, because when driven soft they tend to starve a little. But not doing so still shouldn't give u 20 afr, do you have a afr gauge or you only trusted oem o2 sensors reading ? bad o2 sensor(s) would give u bad numbers to start with.
A bad cat would give u a richer mixture and might cause flooding, it would also kill your o2 sensor.
I'm not looking to be tree huggers ennemy #1 but honestly any wankel+cat = not a good match. they just dont last long or become half efficient really fast, Get rid of it and weld a longer o2 bung to keep optimal readings.
Coils/wires/plugs aren't your issue, until you go on the rich side, never suspect weak sparks.
When lean on a stock motor, your first guess should be either electronics ''maf/o2 sensors'', misscalibrated tps, or fuel feed ''Pump,inj,fuel filter'' BUT those items ''unless MAJOR failure'' should be compensated by electronics. Unless WOT minor fuel feed lack wont affect afr once electronics fix this lack, on wot, lack of fuel can't be fixed.

tarek001

See the thing is that the AFR is fine until i lift off the gas, so what your saying is after lifting off the gas the AFR should still not hit those levels?

The only other issue other than the AFR after lift off and running a bit rich was the low MAF value at idle.

I'm using the inbuilt sensors for all the readings. I'm happy to change anything that needs to be changed but I'd like to narrow down the cause instead of just basically changing everything out and hoping for the best.

Any chance anyone else has logs (perfectly working rx8) i could check out on a pull then deceleration?

I'll probably install the BHR coils and see if it solves the misfires then take each issue as it comes/remains from there on in.

Roytary

I see I see ... lean #s on deceleration is normal stuff, idle afr depends on oem maps, 8's are rich @ idle on oem map, they are rich period lol. if you get 20afr on accel. thats an issue. I wouldn't worry about decel afr's or idle unless you have issues.
From your thread intro, i tought you had issues like power lost or rough running motor to bring afr issues in the first place.
If no symptoms, no issues with stock afr mate.

tarek001

Yes WCS kindly pointed out the obvious (which wasn't so obvious to me at the time haha) that the high AFRs were during times that i was getting off the throttle. After taking his advice and adding extra PIDs it was much easier to read and it showed no real issues except the MAF being low.

I remember doing a run from 0-100km/h and got about 7.1 seconds (need stickier tyres to get any better). Launched from 4000 revs to get that. so ill probably try again to see if i have any power loss once i get the new coils
I know its not exactly accurate and there are many variables but a there abouts number would be good regardless

Roytary

lets put it that way : ecu analyse o2 sensor readings first, then adds maf ones and calculate how much fuel should be injected. when one of theses goes wrong o2 sensor will prevail. when data given doesn't make sense, it will usually go in limp mode ''rich safe mode''. if you get lean afr readings and you get no misfiring codes, o2 is wrong. Bad cat could also make the o2 sensor go nuts but it would have to be really fu**ed. Random ''extreme'' lean afr's on accel is a bad o2 sensor. do you have a cel ?

logalinipoo

What do you call rich at idle? Stock they tend to be around 14.7 unless the car is cold. They do get very rich in the maps to protect the cat, but you can safely pull a lot of that extra fuel when you are catless. You might even gain a little power there.

If you get 20 AFR on accel and you are still accelerating then your sensor it bad. At 20 AFR the car wouldn't really have power to accel at all.

As already pointed out. It cuts the fuel off when you take your foot of the gas. Then the sensor goes to it's lean limit of 20. you can make this very obvious by leaving it in gear with your foot off the gas. It also has a rich limit of 11.2. Which can very just a little by the car. So if you are seeing a steady 11.2ish then you are probably richer than that. If it is bouncing around a bit. Then you are right at it.

logalinipoo

I think you're a little backwards on this.

Closed loop( Idle to cruise speeds normally)
It uses the MAF to see how much air is going in. Then calcualtes the fuel to add. Then uses the o2 sensor to see the end result. If it is off. It will add a fuel trim to hit the desired AFR.

Open loop(full throttle normally)
It uses the Maf to calculate how much air is going in. Then calculates the fuel. Then it doesn't care What the AFR is. it just gives fuel based on the MAF.

With no o2 sensor the car will go into open loop.

With no MAF sensor it then uses additional data and max load tables to calculate how much fuel it should add. ( I'm not sure if it will use the 02 sensor to develop trims in this case)

Roytary

Yup, oem flash overall are running rich,idle too, air pump will give you average readings yes since more (uncalculated maf) air is injected in the exhaust, therefore o2 sensor. Ecu @ Hotter temps will lean out a little. As far about the rest of what you said i mostly agree. o2 must be faulty here. maf failure would bring limp mode

logalinipoo

The air pump only runs During a cold start up to get the cat up to temp. That is why it runs rich at a cold idle.

You can unplug your maf completely and not have limp mode. It might cause limp mode, but won't necessarily cause it.

tarek001

Starting it up today, seems like its smoking fairly heavily. I'm thinking the CAT might also be gone due to the misfires the past couple of weeks.

Still no sign of those coils :/


edit: just received them yay!
Unfortunately they were opened and inspected by customs hence the delay. Almost every package I've purchased from overseas has been inspected :/
I probably wont be able to put them in today as its raining currently.

tarek001

sorry forgot to update this thread.
Turns out the misfires were from the spark plugs and not the coils.
Tested by putting in the old ones and no issues what so ever. Still put in the BHR coils anyway.

Still doing a fair bit of research in regards to putting a turbo on the RX8, it looks like there is a fair bit of risk involved if you want more than 200kw at the wheels. Personally i think 200kw is plenty but my thinking is that if i'm going to turbo it might as well try get the most out of it without having to rebuild then engine again and having more work done to it. A realistic target i was told is about 270kw at the wheels ill need a few other mechanical components changed as well.

Are these realistic targets? or am i having my leg pulled? because im getting a lot of conflicting information on the net.

Please note this is going to be purely a weekend car since I already have a daily driver.

edit: no cel codes etc anymore as well

wcs

iTrader: (2)

Realistic is directly proportional to "How Deep Your Pockets Are"
IMO

Lemme see 270KW to the wheels is roughly 360 WHP

It depends on a great many things.

If you ask Brett he totally thinks it's realistic. Are you willing to go through the amount of effort he is?
https://www.rx8club.com/series-i-maj...-turbo-258781/


But in a nutshell I think 360whp is pretty aggressive target for the "I want bewst and more powar but oh it's my daily driver so it needs to be reliable" type person.
I guess what I'm trying to say nicely is if you have to ask then it's not realistic for your current project.

Maybe the next one.

tarek001

Yeah i figured as much as well. Looking at the effort involved i definitely do not want to have to go through that. Its definitely not my daily driver either, but ive been doing some pricing research and a good price point for me personally seems like the $10k mark for 200kw at the wheels from a few places.
I have done some work already when i got the engine rebuilt previously and apparently they've been running the turbos with 200kw with stock factory engines. Ill have a more thorough read of Brettus' thread.

one in particular is LINK

there are other places as well but didnt want to add all of the links :P

Your help has been much appreciated
thanks.

Darrenseeram

Where can I find the wireing diagram for my 2005 mazda rx8 air pump mine is not getting power and I urgently need hell cause my car is just sitting beside the road side

Legot

iTrader: (1)

Yeah... The air pump isn't the reason your car isn't working...