General EGR Block off.

Discussion in '6th Generation (1997-2002)' started by Fiskekutteren, Sunday 7th Feb, 2016.

  1. Fiskekutteren Club Member ★ ☆ ☆ ☆ ☆

    Denmark Roskilde

    Today i cleaned out the EGR passages and the EGR valve it self. They where clogged up alot, and i really mean alot :shock:.

    So i looked after a EGR Block off plate and found one at akr-performance, but before i brought one my self, i want to ask you guys, if any of you are running without the EGR valve engaged?

    Is it a good or bad thing to block it off.
  2. Zebster Guest

    The increased pollution produced is a bad thing!
  3. Fiskekutteren Club Member ★ ☆ ☆ ☆ ☆

    Denmark Roskilde
    Yes that is true, but can't be more than the Volkswagen cars out here :Grin:.

    I am more curios on if the Engine is going to take damage or behave differently.
    Chunkylover53 likes this.
  4. exec Club Veteran ★ ★ ★ ★ ★

    United Kingdom London
    I would be interested to know too, couldn't give a rats :thumbdown: about pollution, I bet my 16yo petrol car is less polluting or harmful to humans that the masses of diesel cars out there!
  5. Zebster Guest

    What a brilliant excuse. I'll just burn a stack of old tyres on a bonfire, or pour used engine oil down the gutter drain outside my house, as I'm fairly sure that Chinese coal-powered power stations are actually more harmful to the environment!
    stuscrv likes this.
  6. exec Club Veteran ★ ★ ★ ★ ★

    United Kingdom London
    Now now come on, those are all extreme actions, blocked off EGR probably will contribute just couple more grams more of co2, otherwise I would imagine it would fail MOT emissions.
    jimjams likes this.
  7. Zebster Guest

    EGR reduces nitrous oxides, not CO2! Not big on environmentalism, are you?

    Perhaps more seriously, I'd worry that modifying the EGR system on a petrol engine could seriously mess up the AFR.
  8. exec Club Veteran ★ ★ ★ ★ ★

    United Kingdom London
    Am no environmentalist, but I do my fair share of recycling, reusing and disposing things properly etc, but when it comes to cars i don't really care, cars are my passion and i wouldn't think twice about burning petrol and having fun.

    I thought EGR reduced co2, hence the carbon buildup you get on them. I think i've read about people successfully blocking off the EGR, although I wouldn't bother myself unless it gave some performance improvement.
    Chunkylover53 and jimjams like this.
  9. Zebster Guest

    No, EGR is a NOx control measure. EGR implemetation actually causes CO2 emission to increase.

    The carbon build-up is because exhaust gasses are being routed through the valve. All exhaust contains soot, even petrol.

    Diesel cars naturally produce lower levels of CO2 than petrol engines, but much more NOx.
    exec likes this.
  10. jimjams Guest

    As usual Ollie, you're talking bow-locks on this one.

    It's a 1999 Accord with an F20B6 petrol engine, the EGR is mainly there to increase efficiency and reduce knock.

    Your very own wiki link has a sub-section on SI engines that explains this

    ....and before you say this, yes wiki does mention NOx once in that sub-section, but NOx reduction is not the prime purpose for EGR on a 1999 petrol engine.

    To answer the OP's question ...
    If you blank off the EGR on a petrol engine you risk knock and/or damaging the valves unless you de-tune the engine by retarding the ignition.
    exec likes this.
  11. Zebster Guest

    No. It's primarily a NOx reduction technique, even on petrol engines. The benefits you claim are theoretical, not practical.
  12. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
    My understanding also matches @Zebster's :rasta:
    Zebster likes this.
  13. Zebster Guest

    I'm sure that Jim will be back soon, armed with stacks of controversial reference material.

    I can hardly wait!
  14. jimjams Guest

    No, i'm just going to quote the sub-section in @Zebster 's own link

    In a typical automotive spark-ignited (SI) engine, 5% to 15% of the exhaust gas is routed back to the intake as EGR. The maximum quantity is limited by the need of the mixture to sustain a continuous flame front during the combustion event; excessive EGR in poorly set up applications can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. The impact of EGR on engine efficiency largely depends on the specific engine design, and sometimes leads to a compromise between efficiency and NOx emissions. A properly operating EGR can theoretically increase the efficiency of gasoline engines via several mechanisms:
    • Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.
    • Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.
    • Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC (Top Dead-Center), rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is minor compared to the first two.

    Now back to my own words.

    EGR on a petrol engine is primarily there to keep combustion temperature down, which will prevent knock. Where an SI engine does not have an external EGR, it uses valve overlap (the K24 does not have external EGR) to draw some exhaust gas back into the cylinder to reduce the cylinder temperature, and SI engines have always done this well before NOx became an issue.

    Because SI engines run at Stoichiometry most of the time, as long as the cylinder temperature is kept from going too high (which will cause knock), there is not much opportunity for production of NOx. It is only if an SI engine has an ECU with a map that gives lean-burn areas, that external EGR may be required, but again on engines with a carburettor, there is no lean area, yet they still always had valve overlap. Even when an SI engine runs too hot or too lean, the amount of NOx production is miniscule in comparison with a diesel engine, which always runs on the lean side of Stoichiometry.

    So ...
    EGR on diesel engine is for NOx reduction and nothing else
    EGR on petrol engine is to enable advanced ignition timing with reduced knock and, if present, external EGR is there due to the fact that the engine was designed with reduced valve overlap
    Last edited by a moderator: Monday 8th Feb, 2016
  15. Zebster Guest

    Thanks for underlining the sentence with the word 'theoretically' in it!
  16. jimjams Guest

    that's wikipedia for you, but it still doesn't alter what is stated in your own reference

    and my bit isn't theoretical, it's fact LOL
  17. Zebster Guest


    At least we both agreed that the EGR shouldn't be blocked off. Which did at least answer the question.
  18. Ichiban Founder Staff Team

    England CJ Leeds
    Normal service has been resumed I thought all our opionated members had done one and simple question turn into mine bigger than your it
    PeteMM, Fiskekutteren, exec and 2 others like this.
  19. jimjams Guest

    I hope that the "Jim-Seb" (Stan-Ollie) duo doesn't scare anyone away :eek:

    It's really just entertainment, a bit like chess or maybe poker.

    tbh on this occasion the distiction between control of NOx and control of the burn in an SI engine, is the same as trying to make a distinction in the wave-particle duality. It really depends on the frame of reference.

    Shame really, because Ollie usually ends up like this or sometimes like this ...which is the same but in colour :shock:
    Ichiban and exec like this.
  20. Fiskekutteren Club Member ★ ☆ ☆ ☆ ☆

    Denmark Roskilde
    Thank you everyone for the replies :Smile:.

    Maybe next month i will buy the blanking plate and see what is going to happen.

    Will reply back if i get one. :Wink:
    exec and jimjams like this.