Vincentmiata

Not sure wich topic i should post this.

When i drive around there is not much a problem, atleast nothing i can smell or see. WOT and lifting the paddle nothing. But WOT to high RPM and when i let the RPM lower to 3000rpm there are alot of blue smoke coming off the exhaust.. Till about 2000rpm and then its over. WOT to high RPM and brake to low rpm there is nothing. When it starts to smoke and i press the paddle to accelerate its over.


Its only between 3000 and 2000rpm. At first there was smoke at idle and starting the car when its hot. But that seems to be over now.

Blowby is normal and oil consumption is almost nothing for the last 150km or so.


Ive done about 7k km on my newly build block. BP 1.8 NA block with BP4W head. It still got good power and everything.

Parts used are
-Wiseco forged pistons
-Forged rods
-BE engineering oil pump
-ARP bolts
-ACL Bearings
-Brand new TD04L core

Compression is 158/160/160/160

And since the problem begun, I welded some tubes on the valve cover to connect 2 AN-12 hoses on either side.

Is it still my crankcase pressure to high and i should drive more to evaporate the oil?

Sorry for the bad english

Vincentmiata

Oh and im so annoyed by this problem that i dont have fun anymore in this car and thinking about selling the car after 6 years and all the hard work if i dont find the problem within a few weeks.

Voltwings

Its blow by, happened when engine braking on my old built motor (non miata) too. Whats your full PCV set up currently? I see you said you welded up two tubes, but what are you using as a vacuum source, or are you VTA?

Also, how many miles on the motor (is it broken in?), and what weight oil are you using? Conventional or synthetic?

Vincentmiata

I have 2 AN-12 VTA. Ive done around 7k Kilometers. It makes good power. Im using Castrol 10w60 Fully synthetic

Compression is near perfect. When i unscrew the filler cap when the engine is running the oil cap just wobbles a little on top and not blowing off

Voltwings

Ok, mine was VTA when i was smoking as well. I would look to move back to having vacuum on the CC, the vacuum really allows the piston rings to seat properly and helps with that blow by.

There are ways to relatively easily have both VTA when WOT and a sealed system when DD if you chose, but for now see about getting some vacuum on that crankcase.

ThunderFox

I've seen that happen not due to blow-by, but due to worn valve stem seals. If you've done all the work, I would find it strange if you had any noticeable blow-by, unless the engine has not been ran in correctly.

Did you replace the stem seals?

Vincentmiata

Everything was rebuild including the BP4W head. How can i measure blowby?

I drove the first few kilometers easy, not high and not low RPM. And slowly more throttle. After 2000km i changed to oil.

Vincentmiata

Did a leakdown test and all cilinders where about 4-5%

Placed a new PCV valve between the inlet manifold and the valvecover and still alot of smoke, also my parents told me that between shifts at WOT there was also oil smoke from the exhaust. Those i didnt know.. but i recon these are always there but i hadnt noticed these.

Most of the smoke i see and smell are between 3000rpm and 2000rpm after WOT. And only when i let off the throttle and let it slow down by itself.. if ie slow down with the normal brakes i can not see smoke.

Schuyler

iTrader: (1)

<p>I experienced very similar symptoms when the seals in my turbo went out.</p>

Vincentmiata

Turbo only got 7000km on it. Brand new core. Its a TD04L

Vincentmiata

My turbospecialist still thinks its not the turbo itself, but he was thinking about the valve stem seals.

And maybe there were 2 problems, crankcase ventilation and the valve stem seals. And lets say the crankcase ventilation is solved by know.. the valve stem seals will still keep it smoking.

The car is now at a MX-5 specialist and they will look for any problems and i think i will let them replace the valve stem seals.