What is Backfiring ??

[TitanRev]

I'm confused for this. Can backfire be heard ? or izit can see fire coming out of the exhaust ?
What about those modded cars when they release the throttle, there will be fire coming out or got Boom Boom sound ?

Heard that backfire is not good, why ? If a vehicle is running rich, will the unburn fuel ignite itself in the exhaust ?

My car got this sympton. But there's nothing wrong with the car. It only happens when I released the throttle not happening everytime lah. I've diagnosed the car too no problem shown in the ECU...

Can some one clarify ?

 

[BlackSamurai]

TitanRev,
may i know what car are you driving? Subaru WRX? like this?

http://photobucket.com/albums/b128/su8aru/th_impreza.gif
*Pinjam from WBH8668*

 

[TitanRev]

I'm driving a 206. Modded the exhaust from center to the end. The sympton happens after i changed the exhaust. My friend said can see firing coming out but not that geng like that WRX lah.

Only happens when i release throttle not tekan throttle.

 

[madpilot]

Back Firing Bam Bam Bam

Duhhh...!! :rolleyes: so hard to explain.. But this commonly used in rally ..so dat they called it Back Firing System to gain smooth power during entering n exiting the corner.. In ur case.. im not so sure.. how u treat ur car..but i guess it's a small amount of excessive fuel spill n came out from ur exhaust n the explosion does occur when it mix wit da air (O2 atm).No worrries... it juz kewl to be dat way.. dun 4get to check back ur plugs.. maybe 1 of them kong alleady....

 

[TitanRev]

Bro, those used in rally in called Misfiring system.

 

[MonkeyMagic]

some time when u hear the boom boom sound is they play with anti-lag.

 

[psyk]

googled-
Most often a backfire is the result of an air leak in the exhaust system. For a moment when you up shift and often when you let off the gas, there is a temorary "over rich" condition with too much gas in the cylinders. This blows into the exhaust and if there is oxygen (air leak) then it explodes in the hot exhaust pipe. Without the air leak, it is cooled enough not to explode by the time it reaches the atmosphere in a tight exhaust.

can go here oso.. - http://faq.f650.com/FAQs/BackfiringFAQ.htm :D

 

[BlackSamurai]

or this? :)

 

[wiramod11]

hahaha...where in earth got back-firing system..lol..hehehe
back fire normally happens when your engine were running too rich mixture...

anyway guys eventually i guess the mis-firing system name came
from initial D... but the real name is call ALS - Anti Lag System this been commandly use in WRC cars....

I just found some info around the web ....I think some people might find this information interesting!

TURBO-CHARGER ANTI-LAG SYSTEM

Autronic turbo-charger anti-lag system uses a coordinated fuel and ignition control strategy in conjunction with a large effective throttle opening to produce a substantial reduction in turbo-charger "lag". The system is effective from a standing start, throughout up & down shifts and when accelerating out of corners. The system can be used with a large fixed throttle opening, or in conjunction- with electro-mechanical throttle by-pass valve or a throttle "kicker" solenoid. The system incorporates an optional turbo-charger cool-down function that ensures rapid cool-down prior to engine shutdown.

This anti-lag system allows the engine's large throttle opening or bypass to produce a considerable amount of hot high velocity exhaust gas that sustains high turbo-charger speed.

This is achieved with a higher than normal idle speed (2000 to 4000 RPM typ.). The cool-down mode uses a different strategy to produce a large volume of cool exhaust gas for rapid turbo cool-down and it simultaneously controls idle engine speed with the large throttle opening required.

CAUTION

This anti-lag system, like all others, causes considerable heating of engine, exhaust valves, exhaust manifold, turbo-charger and exhaust system. Consideration must be given to the possibility of component damage or possible vehicle fire.

Set-up of the anti-lag system MUST NOT be attempted without monitoring EXHAUST GAS TEMPERATURE (EGT) in the vicinity of the turbine wheel. A knowledge of the maximum safe working temperature a of the turbo-charger turbine is essential. A turbo tacho and a pressure gauge to measure the turbo compressor outlet pressure are also useful tools to assist in the setup of anti-lag.

Operating Modes

1. Throttle opening/bypass controlled anti-lag, using a mechanical or electro-mechanical throttle opener or bypass. ECU activation of the anti-lag function with dash mounted inhibit switch.

2. ECU controlled throttle opening/bypass using an electro-mechanical throttle opener or bypass valve. Dash mounted switch allows driver selection of and-lag function.

3. Fixed throttle opening with full automatic control by ECU with manual override or manual control of and-lag and cool-down function

Notes:- Modes 1 & 2 do not effectively use the fast cool-down function. Anti-lag action is terminated by excessive engine temperature (> 110 degC)
Mode 3 is the simplest mode to use, since it requires no additional engine mounted hardware (eg: throttle kickers or solenoid controlled by-pass valves). The cool-down mode is also most effective in this mode.

MODE 1.

MODE 2.

MODE 3.
Mode 3 use a fixed large throttle opening (typically 8 to 20%). This modes antilag function uses this large opening, high idle speed (typically 2500 to 400O RPM) and ignition retard to produce a considerable amount of hot high velocity exhaust gas that sustains high turbo-charger speed. The cool-down mode uses a different strategy to produce a much cooler exhaust gas temperature and simultaneously control idle engine speed with this large initial throttle opening, when anti-lag is not active.

Activation.
1. Manual:- Ground anti-lag I/P pin to switch from cool-down to anti-lag mode.
2. Automatic:- Anti-lag activated by engine RPM exceeding 500O RPM and remains active far 15 seconds after RPM falls below 5000RPM.
3. Auto/Manual:- As per automatic mode above but inhibited if Anti-lag I/P not grounded.

ANTI-LAG SETUP

Throttle opening, ignition retard and the resulting anti-lag no-load RPM must be chosen to produce the best compromise between excessive exhaust temperature and good anti-lag action. More throttle requires greater ignition retard to control no-load throttle closed RPM, and results in higher EGT. Anti-lag ignition timing for small capacity 4 valve central spark plug combustion chamber engines should be in range -20 to -30 deg. For large capacity 2 valve engines -2 to -2O deg should suffice. Ignition timing retard should be maintained up to a MAP value as high as possible but must be eliminated before 1 atmosphere is reached to ensure adequate off-boost performance. Below anti-lag RPM normal ignition timing should be restored so that engine torque increases with decreasing RPM in order to stabilize RPM. Additional fuel during and-lag is often required to help control EGT. A value between 10 and 20% extra is usually beneficial. The User defined PWM table functions as the anti-lag ignition offset table 1% = 1 deg retard.

eg:- Anti-lag idle @ 2600 RPM approx. User Define PWM output %(0 to 100)
Load/RPM Example TPS/RPM Example
RPM RPM
LOAD 2400 2600 4000 TPS 2400 2600 4000
97.0 0.0 40.0 50.0 12.0 0.0 40.0 50.0
98.0 0.0 0.0 0.0 15.0 0.0 0.0 0.0

Engine idles @ 2600 RPM with 88 to 92 kPa MAP below butterfly with 30 – 40 = -10 deg ignition. Gives 130 to 150 kPa MAP above butterfly.

!!!! IMPORTANT!!!!

1. Irrespective of the actual throttle opening used the ECU must be reset so that the selected open is seen by the ECU as 0% open. Throttle limit learning must be performed each time a new throttle stop setting is set.
2. Before attempting anti-lag set-up it is most important that correct fuel and ignition calibration be achieved for "normal" engine operation.

COOL-DOWN SETUP

The cooldown function produces a stable idle with an exhaust sound similar to that produced by engines fitted with long duration camshafts. This disappears as soon as the engine is laboured at low RPM or loaded at higher RPMs. Spark plugs normally remain clean even during extend periods of cool-down idling. Cooldown MIN RPM and MAX RPM settings are set to values above and below the Desired cooldown idle RPM. These values should be at least 800 RPM apart to prevent idle instability. The cool-down mode MAX THROTTLE setting is usually set to 5% for best drivability.
eg:- Cool-down idle @ 1700 RPM
COOLDOWN MIN RPM - 1400 RPM
COOLDOWN MAX RPM - 2400 RPM
COOLDOWN MAX THROTTLE = 5%



But forget why i got it liao... quite a few years back... i just copy it and put it into my documentation nia... hehhe :D

 

[MonkeyMagic]

or this?

 

[Kopi]

i do find that when using oversized pipings, these poppings happen... when use smaller size, the pops gone, and the flow sounds much tighter than before... no more pops

 

[TitanRev]

Guys, my car is NA lah. My Q is still the same is backfire bad ?
If changed the plug will solve the problem ?

My car is not performing bad no sign of power lagging too. but my fuel consumption is a bit high. I'm not using those straight flow also.

I'm driving using sport mode all the time , can this be the reason but I switch off sport mode also like this.

If spark plug kong liao will this happen too ?

 

[madpilot]

Bam Bam Bam

Duhh...... Miss Fire ... Back Fire... wot ever... if im wrong then correct me then lah... Miss Fire also sounds BAm BAm BAM.. Back Fire also BAM BAM BAM.. 'System' is a looping procedure... not a gadget or device... kah kah kah

 

[TitanRev]

i do find that when using oversized pipings, these poppings happen... when use smaller size, the pops gone, and the flow sounds much tighter than before... no more pops

I have changed to bigger piping but not much bigger than the ori lah. Just 0.75 inch bigger only. The sympton happens when I 1st changed the center bullet while the piping remains the same size.

 

[MonkeyMagic]

Guys, my car is NA lah. My Q is still the same is backfire bad ?
If changed the plug will solve the problem ?

My car is not performing bad no sign of power lagging too. but my fuel consumption is a bit high. I'm not using those straight flow also.

I'm driving using sport mode all the time , can this be the reason but I switch off sport mode also like this.

If spark plug kong liao will this happen too ?

your car got backfire?a lot or just a lil?not everytime got right?

 

[madpilot]

Bam Bam Bam

My old 4AGE having this problems b4... due to plug kong liao... but it..sounds so kewl...

 

[TitanRev]

your car got backfire?a lot or just a lil?not everytime got right?

Not a lot of fire lah. The boom sound sometimes very loud sometimes very soft only. Not everytime happen lah.

 

[MonkeyMagic]

send your car to have a check.it cannot be for a NA 206.

 

[TitanRev]

Check already loh. No problem..

 

[si|verfish]

A fire set along the inner edge of a fireline to consume the fuel in the path of a wildfire and/or change the direction of force of the fire's convection column.
www.americanforests.org/global_releaf/wildfirereleaf/terms.php

1. a fire started to stop an advancing fire by creating a burned area in its path. 2. a firing pattern or fire ignition pattern for a prescribed fire, in which a fire is ignited across the leeward edge of an area and burns into the wind. Backfires can be ignited in parallel strips to protect an area from fire escapement.
www.pnl.gov/atmos_sciences/Cdw/Glossary.html

Retrogression of the flame into the blowpipe neck or body with rapid self extinction.
www.meg.co.uk/meg/weldglos.htm

Any prescribed burn against the wind for the purpose of reducing fuels, creating a blackline buffer, etc.
www.calforests.org/glossary.html

Fire set to push against the wind. Backfires move through the longleaf pine forest at about one foot per minute.
www.longleafalliance.org/teachers/teacherkit/glossary.htm

Explosion of prematurely ignited fuel or of unburned exhaust gases in an internal combustion engine
www.boat-ed.com/sc/course/glossary.htm

Malfunctioning of a torch, causing the flame to go out with a loud snap or pop.
www.autobodyexpert.com/cons_info/glossary/gen_auto_terms.htm

have an unexpected and undesired effect; "Your comments may backfire and cause you a lot of trouble"
a loud noise made by the explosion of fuel in the manifold or exhaust of an internal combustion engine
emit a loud noise as a result of undergoing a backfire; "My old car backfires all the time"
a miscalculation that recoils on its maker
set a controlled fire to halt an advancing forest to prairie fire
wordnet.princeton.edu/perl/webwn

Take your pick.