Timing is retarding at high rpm,spark hardware latency set.

[radics1]

Hi,

i had troubles with a VW Golf using stock distributor hall trigger (4 vane).

Car went well,no sync loss or errors,but it felt really weak above 6000 rpm.
Checked timing with a light,was spot on at idle to 3000 rpm,then it started to retard.

I set the spark hardware latency to 200us to solve the issue,now it feels great,but i also read here,it is way too much for that setting.
Why do i have so big retard? Coil is quite old,but worked absolutely without issues on stock management.

Also,there is nothing in the MS2 manual about this option.

[HidRo]

Stock 16V dist will retard with vacum. Not sure how you have it setup, but might be something like that.

[radics1]

Hi,

where is a vacuum line on a 16V distro?

Check it again,please,Hidro!

[HidRo]

d***...
16V was so many years ago I remebered now that the vacuum to the ECU was what made the timing changes, if I'm not mistaken
So, that might not be the issue
Sorry for the miss info.

[radics1]

Bump for info!

I dont want to kill the engine with some miss-configuration,so please confirm,if 200us is within an acceptable limit.

Today i will check it again,if it doesnt drift with lower setting at high rpm.

[Matt Cramer]

We've found some Mazdas that needed a latency setting that high. It is a bit of an odd value, but it's sometimes needed.

[radics1]

Thank you Matt,

until now i did not use this setting,but this is my first Hall/cam sensor setup,until now only crank VR sensors were used on previous projects.

Car is under testing,we will see how it works out!

[m3ltd0wn]

hi radics, our engine gave up on us, all pistons were melted just above the compression ring and near the marks for the intake valves, they were audi s2 pistons. we don't know exactly the cause of failure but we suspect that the piston rings were bad and didn't dissipate enough heat. the intake air temperature wasn't higher than 37 deg, water stayed at a steady 90degrees celsius, and afr was 11.1 in full boost.

[radics1]

Hi,

now i know why you have this name

By the way, i dont think,that worn piston rings can cause piston meltdown.We use the same pistons,but with E85,so we can have possibly the same failure. I made several MS project,most of them were turbocharged,but never had a melted piston. The worse thing i had were broken ring lands on my Uno turbo with 1.6 Tipo N/A to turbo conversion,but this was at an early stage,did not know much about detonation. The other failure was bent connecting rods in my 1.8T Audi,but this was due to overstressing them with small turbo,big boost,high torque at low rpms.

What was the full boost for you? HP numbers? I hear the S2 pistons can take only 80hp each.
Maybe you can post a pic or mail me!

radics1@freemail.hu

[m3ltd0wn]

i will post a picture, strange thing is that they were burnt near the intake valve marks, and the burn is strange, i've seen detonation burns and they don't look like this, and one more thing it didn't occur in just one run, they burned in time, it is strange

now, we don't know the hp numbers, but the turbo was a k26 from a porsche, s2 exhaust manifold, s2 pistons and rods, kr crank, iridium sparkplugs, the overboost protection was set at 250 kpa, and the highest boost spike was 245kpa, it was keeping a steady 240kpa.

I'm not at the first turbo project either, and this one is the second motor to give up on us after a turbo G60 which was melted because of the driver (he didn't wait for a proper tuning and went driving at 1.2 bar with an untuned car, detonation occured and he melted 2 pistons because he kept the throttle down even if the motor was pinging as hell)
well i've seen those pistons from the G60 and d*** they were nuked bad... but the s2 ones ... it is another story, the burns are identical on all of them, and in the same spot... you'll see them in the pictures.

we have two boosted abf engines, one is with stock pistons and a 2E forged crank and rods, 0.9 bar boost on a mk1 golf gti, turbonetics t3 super 60 turbo, turbosmart wg and hks blow off valve, and that car is a blast to drive, no problems what so ever, and another one is on a mk2 golf, 1.2 bar, je pistons, and other funky stuff, and no problems with this one either.

back on topic, the abf with melted s2 pistons had the same problem as you described with distributor based spark, we checked the timing with the strobe lamp and it was ok, the only strange setting was the trigger angle which was 72.

[HidRo]

Trigger angle on factory VW 60-2, is usually 78, correct?
Why have you set it to 72?

[m3ltd0wn]

it was distributor based ignition, not trigger wheel, but yes, on a 60-2 trigger wheel the Tooth #1 Angle setting is 78 on a VW engine.
on distributor based spark the trigger angle setting should be 60-65 deg if i remember.

[radics1]

Usually for the Hall distributor,you need to have around 60 deg. I think,there could be some problems with the setup,having the other edge as trigger.

I mean at 60 deg the tooth start is just at the sensor,if you trigger the mechanical falling edge from previous tooth,this could be a problem.
I dont know how big is the notch,but i think it could be around 30 deg long. If you have the distro rotated also a bit,this could be an issue.

At the first setting in megasquirt (meaning the wiring inside,pullup,etc),i got it running,but with an odd number,like 15 deg,but engine did not run well at idle.Setting it to 60 deg,was more worse,so i realised,that there are some wiring problems.

Looking forward for the pics!

[m3ltd0wn]

radics here are the pictures with the pistons:



all 4 of them look like this, the car wasn't pinging when it went, and it looks like this happened in time not in an instant, the compression ring was stuck on all of the pistons, so there was lots of heat.

[pigga]

Hi.
The Cavitation on the pistons' surface ist typical for pinging. Detonation at WOT cannot been detected very easily. At least without a special knock detection system...

[radics1]

Post here please the timing map and fuel type.

I dont see the pics now,its banned for corporate PC,but will check at home.

I have read,triggering from other edge with this distro hall can cause ignition advance,dont know if its true.

[m3ltd0wn]

don't know what to say about detonation.. maybe it was preignition , the other friend of mine went full throttle on his turboed PG (g60), and at 1.2 bar pressure there were lots of pings, he ignored them (even if we told him to let go of the throttle when the engine starts to ping) and melted 2 pistons, and that was in an instant, when we opened the engine, you could see melted piston material on the cylinder wall .

[radics1]

That pistons looks really ugly. I think it was pre-ignition,but with that you should have some power loss.

Spark plug heat range? Intake valve seating? Overheated valves could induce pre-ignition,so does carbon deposits as well.

[pigga]

Hi.
Isn't "detonation" a common term for "pinging" combustion? At least that's what I wanted to say: "Pinging" causes this typical cavitation on the piston surface. It can also crack the top piston ring or melt the piston.
So in this case I would guess either too much ignition, not enough fuel or a combination of both of it.
At your initial post you described a major "hardware latency". Are you using "fixed Dwell" in combination with the stock Bosch TSZ-H system?
You said, you are using the stock distributor with its 4-vane-rotor: If you use the stock Ignition stuff, keep in mind that the Bosch TSZ-H Module or the newer "cubic" ignition coil controls dwell. If you are triggering the wrong edge, you make the MS triggering the point when voltage returns to the primary coil. As this point varies (due to the fact that the Bosch module controls dwell) you will notice some kind of "Spark latency" for no obvious reason. As simple way to double check this is to set to fixed ignition angle and vary the %age of (fixed) dwell duty. The module can handle a wide range of dwell%age. If you see a continuous ignition being spot on you have dialed in the right values into your MS.
P.S.: As Radics1 said, too "hot" spark plugs could cause this as well. But then they would have melted down most likely.
Thomas

[m3ltd0wn]

@pigga, dwell was set at fixed duty 50% as per manual and yes the distro is a 4 vane type.

@radics - the sparkplugs are ngk iridium 7, and yes the car had a loss of power over 4500 rpms.

and now some pictures with the PG engine block and pistons after heavy detonation at 1.2 bar... drivers fault for pushing the car hard on an unfinished tune and not listening when he was told to let off the throttle when he hears the engine pinging:


in this case only two pistons were melted... and were melted bad, not like those in the above post.