Author Topic: Smoke (Read 4259 times)

Riverfurm · « **on:** November 02, 2008, 03:13:34 am »

Does black smoke under hard acceleration mean your making power or you have to much fuel or not enough air (boost). There is a fine line between black smoke and power, and with the mechanical IP it seems hard to find. Just trying to dial this engine in for best mileage and power.

jtanguay · « **Reply #1 on:** November 02, 2008, 04:30:14 am »

Quote from: "Riverfurm"

Does black smoke under hard acceleration mean your making power or you have to much fuel or not enough air (boost). There is a fine line between black smoke and power, and with the mechanical IP it seems hard to find. Just trying to dial this engine in for best mileage and power.

black smoke is just wasted fuel. you want to clean that up by increasing the boost. once you do that though you increase the chance for blowby and head gasket issues... but some run 20 psi no problem.

Riverfurm · « **Reply #2 on:** November 02, 2008, 01:50:04 pm »

At 20 psi now with some smoke, like the power. About 2000 miles on a new motor.

jtanguay · « **Reply #3 on:** November 02, 2008, 03:05:05 pm »

hmmmm i would take it a bit easy on that thing if its new then... run it with 10 psi until you get at least 5k miles on it...

at 20 psi your car shouldn't have ANY smoke. if you do, you will want to get an EGT gauge to make sure you don't cook the motor... would be a shame to ruin it!

did you get the 1.9 metal head gasket installed on it???

Riverfurm · « **Reply #4 on:** November 03, 2008, 02:02:16 am »

I put together allot of motors and ran them hard right from the get go. If it's going to have a problem let it happen in the beginning. Using cyl. head studs and an EGT gauge, temps run about 650 to 850 normal driving. Might see 1150-1200 on a long pull with 20 psi going up a hill. I can get rid of the smoke under hard accl. if I back off the smoke screw but there goes my power. I got an ideal for an intercooler that will be mounted under the hood with an electric fan. Don't have any room in front of the car due to AC condenser. Getting 38 MPG around town, might see 40 on the highway. I have the window sticker from when it was new for MPG, It states 38 MPG so I guess I am doing OK for mileage.

James8485 · « **Reply #5 on:** November 03, 2008, 09:28:56 am »

i dont have a smoke screw for say but i run 20 PSI on my aaz and i pour the black smoke, my EGT gauge will climb to about 1000 in city but its really pouring out there, and on highway if im doing 100 and just mat it it pours as well i am running high boost so why so much smoke?

jtanguay · « **Reply #6 on:** November 03, 2008, 09:43:48 am »

Quote from: "James8485"

i dont have a smoke screw for say but i run 20 PSI on my aaz and i pour the black smoke, my EGT gauge will climb to about 1000 in city but its really pouring out there, and on highway if im doing 100 and just mat it it pours as well i am running high boost so why so much smoke?

is the EGT gauge pre-turbo??? you should probably adjust the pump to reduce the black smoke...

James8485 · « **Reply #7 on:** November 03, 2008, 11:30:36 am »

problem with adjusting the pump is then i wont get as much fuel in my higher end speeds, its like i get way to much in normal / alittle heavy foot driving

but when i need it its there........kinda screwy if ya ask me!

Riverfurm · « **Reply #8 on:** November 03, 2008, 12:07:32 pm »

My EGT probe is pre turbo. It does not make smoke intill 15 psi and high rpm, so it must be set about right. Plus I like the smoke factor fo people who like to follow to close.

zukgod1 · « **Reply #9 on:** November 03, 2008, 12:30:58 pm »

Sounds like you have your answers then?

Riverfurm · « **Reply #10 on:** November 03, 2008, 03:50:12 pm »

But why do you see diesels that drag race or do tractor pulls, pour out all that black smoke? More black smoke=more power? Or are they just over fueled?

RabbitJockey · « **Reply #11 on:** November 03, 2008, 03:57:00 pm »

more black smoke is more power, more fuel is wasted, but at the same time more fuel is burned... black smoke is actually partially burned fuel too. when its white is when its just totally wasted.

Jet A · « **Reply #12 on:** November 03, 2008, 04:01:23 pm »

Quote from: "Riverfurm"

But why do you see diesels that drag race or do tractor pulls, pour out all that black smoke? More black smoke=more power? Or are they just over fueled?

Higher mass flow rate to spool the turbo. gets the temps up.

Gearhead · « **Reply #13 on:** November 04, 2008, 09:04:17 am »

I've read that optimum AFR for power is beyond the "smoke limit" for diesels similar to the way that optimum AFR for power is beyond stoich on gassers. I think I read that smoke becomes visible around 16:1 and power peaks around 14:1 or so. Obviously, this changes depending on application and conditions.

That said, I try to keep my smoke at a minimum. A light haze seems to give me decent power and mileage. I'm trying to give diesels a better reputation.

TurboJ · « **Reply #14 on:** November 04, 2008, 10:28:32 am »

There's also one thing about diesel smoke that's nearly always ignored:
un-even air flow to different cylinders.
Take the stock VW IDI inlet manifold for example: it's about as bad as it gets. The two middle cylinders get noticeably more air flow than the outer ones.

This is one reason why it's nearly impossible to make power without smoking with stock inlet manifolds, while twin-plenum manifolds allow almost no smoke even on 200 hp + applications.

And everybody knows also what effect uneven AFR has on reliability... :wink: