Blue smoke on a cold start. Forged pistons

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GreddyMR2
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Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

Hi,

I had my engine rebuilt with forged pistons.
Now, when I start it up in the morning, I see blue smoke comming out a coople of minutes.
Is that normal with forged pistons or during brake-in process?

Thanks
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Driftlimits Performance
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Re: Blue smoke on a cold start. Forged pistons

Post by Driftlimits Performance »

Get it run in! Won't take long.

Were the valve stem seals replaced?
GreddyMR2
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Re: Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

Sure, I am running it in :) Do you think ~1000km is enough?

All the engine was rebuilt. All the bearings, cylinders, head...
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Re: Blue smoke on a cold start. Forged pistons

Post by Driftlimits Performance »

You're not driving softly softly for 1k are you?

As soon as I know its running and ready, I bed the rings in. Avoid idling for too long. It can be done in an hour. The rest is just letting eveything else sat nice. So no, it shouldn't smoke.

Who built it and advised on run in?
GreddyMR2
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Re: Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

I am not very gently, sometimes 50% or more of throttle between 2.5 - 3.5k rpm, then shut the gass off etc... I know it's bad to run constant rpms and idle. I just avoid boost.

Engine was rebuilt by a local mechanic. He didn't advise about run in. I read a lot on the internet about it. For eg:
http://www.mototuneusa.com/break_in_secrets.htm
Or:
http://www.lovehorsepower.com/images/MR ... moval.html

When I first started it, I did as "lovehorspower" say - holded rpm at around 2k for a couple of minutes. Then made some runs of 50% throttle between 2-3k rpms (not 3-4k, as it seems a bit high for me).
GreddyMR2
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Re: Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

Today morning it was like a locomotive...
Lot's of blue smoke. But when it reached operating temp, it didn't smoke.

One thing. When I started it first time, there was no smoke. Then the coolant was not bled properly and when I drove, I noticed temperature getting higher. Then I stopped, waited untill it cools down, got back home, bleeded coolant and it was not overheating. Is iy possible that I damaged rings during short overheat?
Gullzter
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Re: Blue smoke on a cold start. Forged pistons

Post by Gullzter »

I think i would have words with the engine builder if i was you :?
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Re: Blue smoke on a cold start. Forged pistons

Post by Driftlimits Performance »

You need to give it some xxxx. Within 20mins I use full throttle to at least 5k. At least 0.5bar. If you run it in gently it won't last imo.

Make sure you don't have an overheating issue
jimGTS
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Re: Blue smoke on a cold start. Forged pistons

Post by jimGTS »

you need to build boost.

run actuator pressure, keep revs below 5k to be on safe side, but you should be on and off boost (engine braking) to help bed in rings.
GreddyMR2
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Re: Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

Ok, understood. I have done about 200miles already. I gave some boost (about 0.5 bar) with first runs, but I did not have full throttle and only up to 3.5k rpm. Also I don't stay off boost at all when driving now, I give about 0.2 or 0.3bar sometimes, but no crazy pressure.

I will heat it up today and will give some more pressure and rpms. Isn't it too late?

But then question, what is the purpose of going couple of thousand km to have an engine run in properly when you can start pushing it from the very begining?
Marf
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Re: Blue smoke on a cold start. Forged pistons

Post by Marf »

GreddyMR2 wrote:

But then question, what is the purpose of going couple of thousand km to have an engine run in properly when you can start pushing it from the very begining?


Can of worms..

Some people say beat its head in from dot, others say increase RPM and boost over 1000 miles.

FWIW the last engine I built I limited boost to 0.5 bar, max 4500rpm for 500 miles, changed oil/filter, increased rev limit to 6500, 200 more miles, changed oil/filter, increased rev limit to 9000, 200 more miles, changed oil and filter, increased boost to 2bar and thrashed the b0ll0cks off it for 60,000 miles until I sold it. Engine is still running strong today.

Either way, you *need* to bed the rings in and get boost in there as early as possible, so get it in 5th and go full throttle from 2-4k to get the engine loaded up.
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Smoke

Post by cosmos »

Were your engine bores glaze busted, or rebored?
Marf
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Re: Blue smoke on a cold start. Forged pistons

Post by Marf »

Me?
GreddyMR2
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Re: Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

Mine were rebored if I understand this word corectly.
In other words, 86.5mm pistons were placed instead of stock 86mm.

Thanks all for advises, I hope it's not too late and I still can brake in properly.
slipping clutch
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Re: Blue smoke on a cold start. Forged pistons

Post by slipping clutch »

Its just a guess from me but I think you may have a valve stem oil seal issue - its dropping oil into the bore when the motor is left overnight and your burning it off when you start up in the morning - again just a guess so I could be completely wrong.
slipping clutch
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Re: Blue smoke on a cold start. Forged pistons

Post by slipping clutch »

Sorry Luke - I see you have already mentioned valve stem oil seals - maybe I should read the whole thread before I open my mouth #-o
Marf
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Re: Blue smoke on a cold start. Forged pistons

Post by Marf »

Valve stem seals generally smoke on overrun when worn
slipping clutch
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Re: Blue smoke on a cold start. Forged pistons

Post by slipping clutch »

Marf wrote:Valve stem seals generally smoke on overrun when worn

How about if one was not seated properly in the rebuild as opposed to all of them being generally worn?
I agree with your comment though - I worked with a chap a few years back who had a citroen bx and you could predict what would happen as soon as he let off the throttle - it was like following the red arrows"smoke on" "smoke off" I replaced the stem seals on that and the smoke ( and sadly our main mickey taking point ) disappeared.
GreddyMR2
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Re: Blue smoke on a cold start. Forged pistons

Post by GreddyMR2 »

My full gasket kit is Cometic including valve stems. Maybe they are poor quality?
But hopefully it will stop making smoke after brake in.
ashley
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Re: Blue smoke on a cold start. Forged pistons

Post by ashley »

Ask your engine builder if he checked your piston ring gaps when he built the engine, and what they were.
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