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Cars, Tuning, Running Rich And Fuel Efficiency

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Suspense Proficient

Suspense

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Hey I have got a PFC and around 240rwkw... and my car uses a fair amount of petrol, when i am fanging it periodically fuel effiency can drop down to around 18L/100km and general town driving would see me get aroudn 14L/100km driving smoothly...

When i accelerate hard i can expect a moderate sized cloud of black smoke trailling behind me do to the car (r33gtst) tuned to run rich....

My question is why is it that there is a perception that the car should be tuned to run rich to the point where smoke comes out of the exhaust...?

I have seen porcche's and ferrari's launch off the mark and go for a good fanging without leaving a trail of smoke....

Is it just that i have a bad tune? or is it necesarry to run my car this rich?

your thoughts?

mad082 Grand Master

mad082

Posted
Posted

if you are getting unburnt fuel coming out the exhaust then it is running rich. it should be tuned so that the afr's are around the 11.8 to 12.0:1 range. easiest way to see what its like is to stick it on a dyno and see what the afr's are like.

Suspense Proficient

Suspense

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if you are getting unburnt fuel coming out the exhaust then it is running rich. it should be tuned so that the afr's are around the 11.8 to 12.0:1 range. easiest way to see what its like is to stick it on a dyno and see what the afr's are like.

They are at that range.... however i still get a fair bit off black smoke coming from the exhaust

Kinks Grand Master

Kinks

Posted
Posted
I have seen porcche's and ferrari's launch off the mark and go for a good fanging without leaving a trail of smoke....

I've seen exotics running rich on occasion too.

gotta burn fuel to make power, stoichiometric is 14.7:1 so even at 12:1 you are putting more fuel in than can be completely burnt. unless it's excessively rich i would not worry.

benm Grand Master

benm

Posted
Posted

My car is tuned rich (CRD) and when I was getting my new cat-back exhaust fitted yesterday the bloke said that normally when he pulls off an exhaust they have about 1-2mm of black crap lining the insides where as mine has 3-4mm which he said was 'too' rich.

It does blow plenty of black crap when I give it a belting which does become expensive but then I read threads of engines blowing up due to bad tuning and I sorta forget all about my engine running so rich.

Cubes Grand Master

Cubes

Posted
Posted

Is it really blowing that much smoke? If its

I see in the headlights of a car behind a hase of smoke that one could consider a cloud. On the dyno and my other half strapping it past from the side of the road there is zero smoke.

How long has it been since your tuner calibrated his o2 sensor?

  • 3 months later...
The Alchemist Collaborator

The Alchemist

Posted
Posted

Accel pump settings are set high on a PFC. The setting is in Milliseconds, so if you change to a larger injector they will be way to big making the problem worse. And "no" the accel pump settings are not scaled when you change the injector size settings in the PFC.

This setting can give you the big puff of smoke when you first accelerate and cover the back of your car with black crap.

This puff should clear quickly to no smoke on gentle acceleration providing the rest of the tune is good.

Mike

Cubes Grand Master

Cubes

Posted
Posted
Accel pump settings are set high on a PFC. The setting is in Milliseconds, so if you change to a larger injector they will be way to big making the problem worse. And "no" the accel pump settings are not scaled when you change the injector size settings in the PFC.

This setting can give you the big puff of smoke when you first accelerate and cover the back of your car with black crap.

This puff should clear quickly to no smoke on gentle acceleration providing the rest of the tune is good.

Mike

I tend to agree with this.. I've pulled dialed mine back a little past ~1/2 of the std value and still haven't experienced any drivability issues.

R31 Chick Mentor

R31 Chick

Posted
Posted

Just remember that TOO rich slowly glazes shit up and = death eventually. You need to find that comfortable medium.

My car is running a Wolf and off boost is an absolute dream on fuel (500km to a tank city driving), on boost it uses more, blows a bit of black smoke but nothing exessive and pulls hard, back off boost, comes back to good fuel economy. Its making 274.8rwhp too out of a fairly stock RB20DET (exhaust, Wolf, RB25 turbo and fmic) and the car is happy as.

SilverECR33 Veteran

SilverECR33

Posted
Posted
Hey I have got a PFC and around 240rwkw... and my car uses a fair amount of petrol, when i am fanging it periodically fuel effiency can drop down to around 18L/100km and general town driving would see me get aroudn 14L/100km driving smoothly...

When i accelerate hard i can expect a moderate sized cloud of black smoke trailling behind me do to the car (r33gtst) tuned to run rich....

your thoughts?

strange u get better fuel econemy running it harder, than putting around, my car is total opposite. a little black smoke is normal from a highly boosted engine, as where then it would be practical to run it a little richer.

My question is why is it that there is a perception that the car should be tuned to run rich to the point where smoke comes out of the exhaust...?

seems hes running it richer, so it doesnt lean out up top. leaning out is bad , but of course running rich alot is bad also, over time, it will wear out ur rings.

Is it just that i have a bad tune? or is it necesarry to run my car this rich?

maybe try a new tuner. should be able to rectify that with ur PFC i would imagine.. just gotta find someone who knows how to tune the pfc properly.

The Alchemist Collaborator

The Alchemist

Posted
Posted
I tend to agree with this.. I've pulled dialed mine back a little past ~1/2 of the std value and still haven't experienced any drivability issues.

Well I have 700CC injectors and dialled my Accel pump setting to 1.5ms at 1000rpm down to 1ms at 3&4000rpm, much better and no black puff or cloud when I drive away. The setting is best felt by the driver on the road of course but with only gentle acceleration. The bit you're feeling for is the very initial push as you just open the throttle. Slaaming the throttle open especially at rpm under 3000 allows you to feel no change regardless of setting.

Zero them out and gradually increase them and you will see what I mean.

Mike

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