How do you know how much octane you need?

What does your knock sensor say?

Lets try this a different way. What octane were you running at what boost level (and which turbo again)? Even with good gas, timing is a thing, post your timing table.

If i have a turbo, i run the highest octane available.

And then tune for it.

What's the price difference between a tank of higher octane fuel and an engine?

Asking for a friend.

Roughly the price of engine minus a cheap spark plug

Yikes.

I run 95RON, wanted to tune for low octane for the power level it will allow - higher octane here is a problem.


- I suspect something is wrong with the base timing - I run MS3 Basic and offsset on the ecu came out -13deg I do not know if it is true TDC... Could be the marking on the ATI are not true TDC of the engine.\ (I read that sevington showed the center mark on the ATI does not match the timing gear)
- After a few hundred km running with no boost I started tuning for boost, I noticed the boost run very linear upto 20psi @ redline.

This is the ignition map that came with the ecu:

https://cimg8.ibsrv.net/gimg/www.mia...c7b47b2260.pngMS3 Basic base map
I run this ignition map thinking it is very low, less then 10deg @ 200kpa...

Well, I wanted to check why the boost is so linear so I did run upto 20psi~ (linear) at redline... a few times, the afr was 11.5-12 all the time, I did not have my knock sensor earphone on :\ - no audible knock from the driver sit.
After those runs the engine start showing blow by - I believe it was hurt,

Another small thing:
My ignition setting was:
Rising edge on 99-05 Spark mode, I understand from Dimitrious that it should be Falling edge ...( it run ... what does it effect ?)

Thanks for the input guys.
Elior

Leading edge versus trailing edge could be worth several degrees of timing. It would make it advanced.

My lesson is:
- Find TRUE TDC and true tdc offset - base timing.
- Correct timing settings
- start with low timing in boost
- low boost to start with
- tune with my expensive knock sensor on

95 RON is generally considered to be about 90 (R+M)/2, which is the American standard of measurement.

So does this stay true even if the base timing is set using Rising? I just looked at my tune, set up spark three years ago and it is also set on rising. wondering if I have been close to meltdown.

Base timing is very important. When I throw boost at a motor, I physically verify it with a dial indicator, if the motor allows it.

na, what I am asking is: if I am on rising edge and set base timing, is my ignition going to be more advanced in boost than if I do the same with Falling edge?

The head is dead the block is good.

Can I use a non VVT head on VVT block ?...

why not?

https://cimg2.ibsrv.net/gimg/www.mia...fc3198235.jpeg
https://cimg3.ibsrv.net/gimg/www.mia...3e938e1f8.jpeg
https://cimg5.ibsrv.net/gimg/www.mia...4d9a4b23b.jpeg
https://cimg6.ibsrv.net/gimg/www.mia...7e01707bb.jpeg
https://cimg8.ibsrv.net/gimg/www.mia...61c76d6c3.jpeg
https://cimg9.ibsrv.net/gimg/www.mia...114fbc580.jpeg
https://cimg0.ibsrv.net/gimg/www.mia...5df2dedbb.jpeg

Out of curiosity, do you have a log of when this happened? What were the specs for the block and head? Was it a stock vvt head? Any idea where in the range the vvt was?

Looks like this happened at 2 pistons, correct?

all 4, vvt was disabled...

wowww

So, what are the dimples on the valves? FOD maybe?

probably from when his pistons commited suicide

But aluminum putting marks like that on a valve face? I guess it it was moving fast enough.

And at that temperature

Jesus! Yeah post logs so we can see what was the true cause here

Head shop marking

I would assume these dots cause heat spots. Didn't they have edding markers?

Marking them for what? Those valves are rock hard - they'd have to really strike them to get those marks.

Marking them in order to know which goes where - I believe this is not the first head it been done to.

Could it be responsible for hot spots and the pre ignition that melted the pistons ?

Thanks
Elior

No. You are

Lol, fire your tuner.

I tuned it and there were no abnormal signs while tuning, could be the few 20psi peaks did the kill.

I'll try better next time - in a week or two.

Those pistons are eroded, that doesnt just happen with a few spikes. You were consistently detonating. You need to make or get a set of detcans. There most deff was abnormal signs with the way your pistons look, you just didn't pick up on them.

Take pictures of that motor too.

I have heard of dimples on combustion chamber surfaces, to reduce detonation.

Just be sure to set your base timing at idle before you drive anywhere next time.

Never forget Singh Grooves.

Severe detonation can melt a piston nearly instantly. I've had pistons on a two-stroke go from new to totally melted down in less than a 1/2 lap of a track. Mild detonation can also slowly erode the softer metals. But that to me looks pretty catastrophic (instant).

On second look, those are clearly marks from the engine builder. 6 marks on intake/exhaust valve, 7 marks on another set. That is a stupid way to mark them, just use a marker pen. Yes, those could initiate detonation due to a point source of heat forming, but they aren't the cause. The cause is you thinking you can run 20psi without proper tuning and fuel.

-removed my rude comment, unnecessary-

As I said, fuel was 11.5-12 all the time (could be the sensor is off, it is my ls4.2 spartan running for 7 years now).
The timing map is @ less then 10deg from 180kpa and up (could be base timing is off I got -13deg for ecu offset).
I understand the rising edge vs falling can advance timing too.

I'll double check everything on the new build with a new digital WB and 4.9 sensor.

Thanks for the input guys :)

https://cimg3.ibsrv.net/gimg/www.mia...3ec67d3a8.jpeg


New engine to burn :)

I'm impressed, 2 weeks and you got the block re-bored and decked with new pistons? Or is that just new pistons only? No matter, I can barely change spark plugs in 2 weeks.

Same here! Always a honey do that takes precedence!

Isn't it good practice when installing new pistons/rings to get it honed, so the rings actually bed in and create a good seal?

Yes

OP makes a point of doing everything wrong and backwards. Don't question it, just enjoy the show

I missed seeing these types of posts Vlad. Thank you for making me laugh and reminding me of part of the reason im on mt.net

I mean... Did the old rings really have enough time to break in the cylinder walls?

Jokes aside, if OP was pressed for time, he coulda just dingle balled it.

Negative. Dingle balls and cromo rings are a no go. Look to the plateau for answers.

I thought that the plateau hone was just a finishing technique that could be achieved with a ball style hone. Would be hard to do yourself with a drill fitting hone, sure, but that's what my reading led me to believe before I got my motor built.

https://www.productionmachining.com/articles/for-plateau-honing-consider-ball-style

edit: unless the dingle ball hone doesn't fall into the category of ball style hones because it's on a drill instead of more purpose built tooling.

It is honed

Agreed Schroedinger, harsh.

Elior - we will learn more from our failures than we will ever learn from success. As a scientist/engineer - I never see papers discussing various attempts (which end in failure) in the literature. Unfortunately, that means all of that knowledge/experience is lost and we are all left to make attempts at dead ends. If more people would document their path/process and failures we would advance at a much quicker rate. In so many words I'm saying thank you for sharing.

Oh so logic wouldn't tell you that low oct and 20psi of boost would result in failure?

Oh this website I've learned that it is bad to leave rags in your engine. It is bad to have negative valve clearance. It is bad to have your friend balance your crank in his garage and it is bad to take advice from people who don't know anything. All of those pieces of information are valuable and you are foolish to believe otherwise.

Appreciated, thank you.

Elior

10:40

https://cimg3.ibsrv.net/gimg/www.mia...76ec3f497.jpeg
Current state - ready to start boosting !

looks pretty clean

I lost brain cells reading this. Bumping this up so others can enjoy a good laugh

Car’s running strong @ 1.5bar, about 400hp at the crank.

go look for your brain cells.