would a sharpe edge/point on a piston crown bring on Det ?
i checked the data logger and there was no afr/charge temp issues
and timing was mega safe, the piston valve cutouts had been remodelled due to a earlier valve / piston collison which mashed the pistons, now i have a dead head gasket which looks like det damage, and on that cylinder/piston there was a sharpe edge/overhang from where the cutouts had been dremmelled is that the possible cause for det?

 

Yes. Could be creating a hot spot leading to det.

 

How do you know the timing was safe?

Mark

 

it was mapped by a reputable tuner including det cans and had a small amount of advance reduced from optimum whilst i was still running in this engine ?

 

Mark[/quote]
it was mapped by a reputable tuner including det cans and had a small amount of advance reduced from optimum whilst i was still running in this engine ?[/quote]

Was the engine mapped at boost before running in,
The way I read it was it was then you ran it in this is the bit I am unsure about as I dont understand the way you worded it.

Mark

 

Mark, they mapped it on a low boost setting, and it was still on that low boost setting during running in IIRC

 

So the engine was run at max load at max rpm but running low boost.

Mark

 

yes

 

So if it was run that hard why did you need to run it in

Mark

 

it was freshly built, then mapped , i wanted / preferred to run it in on low boost which the mapper seemed to agree with, then return after 500 - 1000 miles or so to make sure there was no problems then full planned boost mapping ?

 

So it failed before the return trip for mapping, What restrictions where placed on the running in, and what fuel was used for mapping and when the gasket failed.

Mark

 

mapped on regular unleaded and run exclusively on unleaded, restrictions ? none as such, apart from that i am a firm believer in not altering anything i have paid for to be setup, i.e not running any more boost than it was mapped for. etc etc ?????

 

 

What was you doing when it failed,
Also did you drive the car while mapping.

Mark

 

More picts of pistons and head would be good

Mark

 

piston has 6-7 very small det marks at the exhaust side, so has the head on cylinder No2
was driving on boost , probably very near full throttle , approx 4000rpm 4th gear had accelerated at this level for merely 4-5secs at the time of failure, all upto to normal running temps etc !

 

A possibility....

Looks like to me, the headgasket has been squashed due to incorrect
head torque procedure causing a sharp edge leading to eventual gasket
failure. Det may be there but I suspect this is only a result of the failure
and not the original cause.

Just my 2 cents worth, still bad shame

 

Any other marks on other cyl,
Have you checked the head and block to make sure its straight, You can damage a engine also if the gasket has blow,
Has it been using oil or water since rebiuld.

Mark

 

no oil / water usage, the head was checked and skimmed cus it was not perfect before fitting , i had a tick when on boost for a week or so, which i could not put my finger on ( like a exhaust gasket tick ) but sounded like a fooked cv too ! i returned the car to my mapper, he ran it listening for the tick but he could not here it, he road tested the car too, but he did not find a fault , he decided to do some more mapping while i was there and increase the boost to 1 bar as the engine had done some more miles since, but still not run my planned full boost figure! on the way home the tick was still evident however he had run full load,full rpm runs without incident so i attributed the tick to a drivetrain problem that i would investigate or would fail then i could repair it, but it would appear it was the head gasket ?
first mapping.

 

So how was the 1 bar boost map done,
What you will need to do is fix then chack for any other faults then return to the mapper, Then biuld boost up slowly and check the mapping to be safe,
Then do the same as when it went wrong again with mapper carefully check for safety.

Mark

 

i don't know mapping ,he had the car for approx 1 hour then returned with him saying its now been mapped at 1 bar !, are you saying that not all load points may have been covered ?

 

1 hour for a map even a partial one isnt long enough IMO

Dont discount the headgasket suggestion though

 

For me on Autronic with a car thats already been mapped is plenty of time to cover all the mapping points needed,
Its a pity you didnt drive the car while being mapped then you could tell me what had been done and I could have helped,
Based on the map being said to be very good with what you have said then all you can do is fix then go back and check to see if there is a problem,
There may be another fault some where so be carefull.

Mark

 

what are your comments on the spikey piston ? but the others where not ?
and that was the failed cylinder ?

 

no he had mapped it previously, it was a alteration to map going from .6 to 1 bar !

 

Simon he would of only needed to map prob 6 rpm points and 2 extra load table, And would have only prob needed 5 to 10 presses to do this,
1 Hour is easy long enough for a person who know the Ecu and how to map.

Mark

 

i thought nobles only mapped on the rollers? i could be wrong of course.
do you know if it was mapped on the rollers lee or was it done on the road?
bryan

 

HI,

What do the spark plug's look like (colour etc )

DAVE R.

 

perfect

 

But is that std head gasket you are running ?

 

That was a standard gasket yes.

Should be fine at those boost levels though, ive run them with more cylinder pressure than that without failure in the past.

I think simon@SECS may possibly be onto something with the overtorqued theory, ive seen them fail because of that before.

 

i was under the assumpition standard gaskets where to be used with stretch bolts and steel gasketswith studs??

 

was not std gasket chip " Spesso " 1.9mm

 

I used to run the swindon one on mine as the std composite one used to always blow.

 

Spesso was quoted to me as good but lets not blame the gasket me thinks something else to blame

 

I think you have the same problme i had back in 1997 not much info on Turbo LET/EX Engines unlike the Cosworth YB engine. I bult a very strong LET with a T3 on it and the guy who mapped it melted it on the rollers, I just dont think a set up on the rolling road is the right way to try and map any turbo car.

 

my opinion was, if mapped on rollers then it will be safer on the road ? becus in the dyno the load can be greater than that on the road , and the airflow in the cell is less than on the road , therefor more cooling to the intercooler, but i just thought that, what about air pressure to the airfilter, if in the cell there could be less ambient air pressure for intake system to inhale but on the open road plenty making a weak afr ? ? ?

 

I wasnt blaming the gasket, more the installation.

Looks like the cylinder ring has been over clamped on the side where
the damage has been caused to me.
This could have been cause by wrong tightening sequence, block
and/or head warped.

 

In some ways you are correct but not in the most important heat and cyl temp,
The harder the car is ran up through the gears the higher cyl temp there is, You cannont duplicat this buy just doing power runs on the rollers.

Mark

 

if you look at 2mins & 37secs in ( 2:37.2 ) ,is the moment i knew something was wrong, its like a recurring bad dream lmao . not at any point did i have more than 79% throttle. but what does concern me is the extremely consistent 27deg of air intake temp ! ?
you can see the gearchanges and boost as i drove before

http://www.migweb.co.uk/forums/showthread.php?t=244296