Originally Posted by nick4592
I have seen a lot of crushed Pistons from over boosting and the mis-use of Nitrous...
Good stuff Nick, Stock motors I take it?
I’m kinda trying to separate “normal chamber pressure failures” and “detonation induced spikes of pressure”
Over boost - turbo goes momentary outa its efficiency, heats up the intake charge wicked, compounded with the ECU hitting some un-mapped lean cells - det det bang.
Nitrous is interesting though as the cooler charge, i woulda thought, should suppress the det a little. If the popped Nitrous motors are purely from too much natural cylinder pressure (read slow progressive flame propagation, not the super imposing of two fronts when detonating) then would be good to know more details of that failure.
- For those interested .. or bored… I try to distinguish det failures from normal ones because I find, with more and more people into cars (specially Japanese imports here in Aus) the % of misguided people making mistakes has gone up crazy. Trying to get good information is hard.
Fuel pump failure, a clogged injector, a worn out snapped cam belt are all scenarios that can mash a motor real quick if under load at the time. Though catastrophic, the cases are almost always completely irrelevant when trying to ascertain the strength of a given motor. The crystalline matrix of ferrous materials combined with the reciprocating / flat plane movement induced resonance in a motor means an item will generally withstand a greater maximum load if its progressively introduced, rather then a sharp spike, IE; combustion motor detonation
Id like to think, the precautions I take when modifying a car lower the chance of these simple failures to almost zero; hence the reason im looking for the power ppl are making in a properly setup stock EJ20G. There’s really no such thing as HP, or KW, it’s a resultant number, made from the twisting effect on the crank from a combustion event (the fact those combustion events occur more rapidly as the revs rise is ladi la) This is why I think about cylinder pressure, and perfecting each burn
I’m finding my mates Subaru interesting cus it’s a whole different motor, developed under completely different guidelines, budget restraints then the Nissans and Rotary’s that mates have.
Nissan and Toyota at the time, structurally over engineered many of its engines, (even those that would find resting place in cheap family hatch’s) in the late 80’s due to Japans intent of owning Motorsport at the time (To beat Europe’s finest). This allowed them to then dress the motor up in different guises to suit different cars. SR20DE in a hatch, SR20DET in Silvia’s, and course the quad throttle bodied, solid lifter version in the GTiR.The different versions of the RB are well known, from NA 2.0L family car, to 3.0L Australian sedan, from turbo RB25DET in a Cefiro to the RB26DETT in the GTR and Stagea 260RS. This inherent engineered strength changed things around drastically. I can still rem reading my cousins first car magazines, 15yo, ‘97 about various mid 80’s turbochargered cars, it seemed a lot of the focus when modifying was stopping the thing from spitting a head gasket, over heating or cracking a block liner. The head gasket of the day, was akin to Subaru purposely using soft clutch friction plates in their cars, so it would take the load and slip first, instead of shearing gearbox gear sets. New tech brought on multilayer metal head gaskets, better designed / cast waterjackets to prevent “hot spot” induced detonation, head quash zones that worked better to promote better charge turbulence and then stronger coil on plug ignition systems to produce in cylinder plasma spawn like never seen in the OEM world! Just like a breaking water encatchment, pistons would next take the brunt. RB26’s come to mind (haha whoops). If stock, well tuned and in good nick, when heavily loaded (large turbo, big boost, strong cylinder burn) they wont do a gasket, or a piston ring land, or a bearing, or even a rod; they actually reach the working load of the rod bolts. Rod missing a cap makes good work of a block ( not to say this was done on purpose) You lucky f_ckers had Toyata selling 2JZGTE clad Supra, so you know well about the strength of those motors when stock
The Japanese bigs were all able to develop this production car motor hardware on tracks, funded buy the 80’s insatiable thirst for automotive tarmac racing, I think Subaru missed the wave, and it took them a few more years to make the EJ20T a serious unit, capable of making the 250-300hp/Litre power needed. A workshop not far from me has the worlds most powerful EJ, 540kw at all fours or something crazy.
This is all moot really, a built EJ20T with pistons of a metallurgical and structural decency is on the cards anyway, its just always interesting to see how far you can take a setup, hence me looking around the net.
Apologies if the caffeine fuelled rambles been offensive