Smoke no more, and no DPF either.

[gldgti]

alright guys, heres a little experiment i have done to demonstrate to you just fine the line is between smoke and power, and why if you want to DPF delete your new golf, then it shouldn't be a problem for your concience...

until now, i've been running stock boost on the mk3 - 12psi under constant load conditions.

i have also had fuelling set to produce what you might call a plume of black magic, a good amount to get rid of the annoying p-plater behind you, that sort of thing.

i just fabbed up my $4.00 boost controller from bunnings. 2 drip irrigation screw adjustable valves, tee'd into the waste-gate actuator line to bleed off air. works very nicely!

without touching fuelling (been the same for 3 months), i first increased full load constant boost to 13psi, then 14psi, and now sitting at 14.5psi.

at 13psi, i noticed i slight reduction in smoke at full load, but it was not hugely significant. up to 14psi, a further reduction in smoke was obvious, as well as power being slightly better. now at 14.5psi, i notice very little smoke at full load.

the car definately pulls harder now, though the real increase may be small, it is noticable (even the missus noticed the car was faster).

just goes to show however how a small increase in boost pressure can bring the smoke levels right down. i tried to "smoke" some guy in a lexus 4wd last night who was sitting less than a carlength behind me, at 110km/h in the rain, and i couldnt! i jsut pulled away instead ! now i have power instead of smoke..... ohhh the shame!

[gregozedobe]

No secrets there,

more boost = more air = more oxygen = more complete combustion = less soot

but watch out for the rest of the story ie

= more heat = melted pistons (and/or other problems).

Soot is simply a by-product of incomplete combustion processes. If you don't over-fuel your diesel you won't get much soot.

[Greg Roles]

Sweeeeet. Great observations, thanks dude!

I do hate smokey exhausts from any car, so I'm determined to stay as smoke free as possible.

seems I'll just have to melt pistons!

[gldgti]

ahhh theres another thing guys -

i accept the higher boost will produce more heat, definately. however, its actually WORSE if your producing black smoke. EGT's go way up under black smoke conditions. im not any more likely to melt pistons now than i was before.... well not much

[Jaymz]

Love that DIY stuff, excellent work.
For $4 you now have more power, more complete combustion equalling better economy. And now you definately got Boooooost!

Will be interesting to observe the benefits of better fuel economy now you have better combustion. Are you planning to do any comparisons? Or is this simply a power mod for you?

[gldgti]

i wont get better fuel economy now, it oughtn't change. the only time i actually get to that level of boost is when im accelerating hard. even going up the hills on the f3 between gosford and hornsby, at 110km/h, it doesnt break 11psi usually. its mainly when im really heavy on the foot that i'll get to that kind of high boost - around town, for very short stints.

the fuelling is in part controlled by the boost level - there is a boost actuated fuelling pin on the injector pump which increases fuelling as boost goes up. thus, when criusing and low throttle, there is little fuel, and as the engine loads up and boost increases, the fuelling also increases to give more power. now, that ratio air/fuel is more lean, meaning more complete combustion and gives a little more power - until i increase fuelling again for even more power, but black smoke again.


all thjis occurs right at the top of the "throttle" range, and so effects fuel economy very little, if at all.