Hey guys, I have just recently installed my racing beat street header back exhaust. I took a pic of the exhaust ports and sent it to a friend. They were very white, and he said that it may be running lean, which is weird for a rotary right?

I expected the car to backfire and shoot flames with the new header back exhaust on there, but I get nothing.

How can I tell if its running lean? I dont have a wideband that I can use. My first thoughts are fuel pump, fuel filter, fuel injectors. What do you guys suggest to check?
Thanks!
Jessica

 

if the fuel filter looks old it would be a good idea to replace it. depending on the car's mileage it might be a good idea to have the injectors cleaned.

Look at your Crank Angle Sensor and see if the bolt is in the middle. If it's been messed with might be a good idea to borrow a timing light and reset the CAS.

 

Show us the picture.


Without using a wideband it can be more difficult to tell the mixture. How does the car run? What kind of mpg do you normally see?

 

So long as you have an 02 sensor hooked up, most normal operation is under stoichiometric conditions (14.7:1), which will produce lighter colored deposits. I wouldn't read too much into it, unless you measure mixture with a wideband under load.

 

You could also pull out the spark plugs and see how they look for good measure.

 

Remove the spark plugs and look at them. If they're not covered in flaking black deposit I wouldn't worry about how much fuel the engine is getting.

 

it also depends on how many mils and or compression it has o and if u rely wanted some flame u should have a T2 with a straight pipe mmmmmmmmmmmmmm mmmmmmmmmmm

 

the exhaust port sleeves are no real indication as to how lean or rich the engine is running. usually they are cream colored on 95% of the engines i pull apart, the other 5% were running pig rich, had bad oil seals or had a blown rotor.

 

90% of driving is done in closed loop (14.7 afr), so it should be no surprise the exhaust ports are white

 

incorrect but the AFRs usually are in the 14's, they do dip pretty low into the 11's on S4 non turbos though at WOT, similar to both turbo models. the S5 n/a stays pretty close to 14.0:1 almost full time.

less than 5% of your driving is done in closed loop on these cars, they are not OBD compliant and are still fairly primitive electronic fuel injection systems.

 

exactly, when the exhaust port ISN'T white is when you have a problem!

 

Like this? (My old motor)

 

^ blown rotor. see, it's not that difficult.

 

i would say the exact opposite, about 90% of your driving would be in open loop. this isnt a 2007 civic we are talking about. pre obdII cars tend to not even have a true closed loop system, they still depend on the o2 sensor at full operating tempature during cruise to determine a/f ratio but unless you are in cruise control or very staedy with the throttle you are never going to see it go into closed loop.

 

Geez, you guys must drive with a lead foot at all times. It's extremely easy to stay in closed loop on the freeway. I watch my AFRs bounce around 14-15 AFR most of the time I'm driving because I'm cruising once I get up to speed. No need to be on and off the throttle unless you're going stoplight to stoplight. If you keep the throttle steady, and the RPMs under 3800, you'll typically be in closed loop.

 

^- This. I did extensive logging with my wideband before tuning the car with the RTek and most of the time it's between 14 and 15 AFR. At idle it's richer - about 12.5:1. At WOT, especially at 6,000-8,000 RPM, it's extremely rich - as bad as 11:1.

 

Yeah even the S5 n/a is pig rich at WOT from the factory...

 

You're not running lean, more than likely rich though. A properly working S4na runs quite rich, and if your Aux ports aren't opening like most are as of now (done by exhaust backpressure at the cat or resonated midpipe) it goes from rich to Cookie Monster. Mmm 87 Octane.... OM NOM NOM NOM!!!

Check your plugs' condition. Chances are they probably need cleaned with a wire brush too.

 

Heres a pic of the exhaust ports after i took off the stock header.


The car runs fine. It gets pretty decent mileage, but nothing to write home about.


Ok so to start with, I need to check:
1) Fuel Filter
2) Clean Injectors (Can I just use an injector cleaner that you put in the gas? Or do these need to be sent off?)
3) Check the timing vis CAS bolt
4) Check spark plugs

Heres a pic of the car, after my mods





Needs moar low, and camber in the front

 

Just to reiterate, those cream colored exhaust ports do NOT mean you're running lean and no need to worry right now.

It never hurts to check things like fuel filter and plugs but these would be regular maintenance.

Looks like a nice little car, good luck and enjoy!

-NJGB

 

If you're not having hot start issues, then just run some injector cleaner through the gas tank.

Fuel filters are cheap, so if it hasn't been changed since you got the car I'd do it now.

Pull the plugs and check to see how much electrod is there. If you haven't changed them since purchase, you might be ok to just wire wheel them clean. However, don't be surprised if your find that the electrods are now nubs and it's time to replace those as well.

 

just because the AFRs are at 14-15:1 it doesn't mean the car is in closed loop. mazda tried to target their AFRs and the ECU is mapped with that target in mind, so if the car is in decent mechanical condition it will be near stoich anyways.

in all honesty i have never even had a functional O2 sensor on my car(before it was modified) and it always got decent mileage.

 

... You're killin me!!!!!!!

you put new exhaust on it and you want it to backfire... all backfiring is going to do is get attention and blow out mufflers

 

^^^^
I can read 12pt font just, fine, no need for that

I guess ever since I got into cars, the FC in particular, I noticed the backfiring and flame shooting, and I always thought it was cool. Little things like that makes me giggle hehe.

Thanks for the help guys, im going to do everything on that list tomorrow hopefully.
I did however find a good deal on a Turbo II motor. $1000 for engine, ecu, wiring harness, tranny, and NIB clutch. However, its an S5 TII and im S4...still debating on that swap.

 

If u want the extra power, have the means and can deal with downtime on the 7, I say go for it. As for flame action go do a 2nd gear pull and engine brake.