Hey datsik,
lets have that article about building the knock indicator.

Quote:For a NA, mild street engine, there will be no problem whatsoever, but for a blown engine in competition mode I would be taking a second [& third] look at it.
The reason for the exercise is to boost torque & if I am successful, it will allow me to operate at lower rpm's generally across the board & this should translate into less stress & heat. Initial target is to be able to cruise at 3,000 rpm @ 100 Kph in top gear. In a lightweight like a KB10, I think it should be achieveable.

Edit, per Tapprts request.
The reply was directed straight at A14Force & he is aware of the engine that I will be building for my coupe, but basicly its an overbored A13 short deck block with a stroker crank. To make it work I have a set of 'replacement' A15 pistons. These have the bowl centralised in the crown of the piston while the originals have an offset bowl. This offset gives a wider flat surface area on one side & this is cleverly placed under the squish area of the head to maximise this feature.
The pistons with the central bowl have less flat surface under the squish part of the head, however, with the stroker crank, it's necessary to machine a small amount from the top of the pistons to bring the crown down flush with the block as it stands proud at TDC even though they have a lower crown height than all other A series pistons. As you rightly concluded, any machining will result in the crown of the piston, that band around the bowl, becoming wider & presenting a greater surface to the underside of the head, & this goes some way towards reducing the difference between the original A15 pistons squish area, & that of the replacement pistons.

Additionally, the distance from the crown of the piston down to the top ring is not particularly great in these Datsun engines & removing too much material from the crown can weaken the top of the piston. It then doesn't take very much detonation to cause a failure of this part of the piston, & he was asking about that.

A14Force has been through much of this with me before & [hopefully] understood what I was writing about.
If you scroll backwards to my previous post you will see the pistons in question. This modification works just fine in a normally aspirated engine, but I suspect that it might be a bit risky in a blown engine.

i like boost

I think he is either gonna have the block decked, or his pistons already stick out too far.

A good aftermarket cam takes some of the restriction issues out and helps the boost arrive earlier with less required to make the same power as a stock cam.

The cam in mine is;

IN opens :30
IN closes :65
EX opens :70
EX closes :30
Lift @ cam .260"

the pulsar turbo pistons;

ACL duralite part no. 4MKRY8055-0.50

This setup is holding onto 14psi pretty easy however I have EFI and an intercooler to keep a lid on things a bit.

All of this is well and good but what does it have to do with finding rings to cope with 14 psi???

There's nothing wrong with his turbos, the reason he's rebuilding them is from other issues, like leaking filters etc

So get off his turbos
He can't CONTROL the 14 psi boost
He doesnt actually WANT to run it this hard all the time, its just that he wants a motor to be able to cope with that scenario if he cant get better control of it

Can the squish talk and get back on topic!!!

DGxx

how many more engines will it take before you realise that twin turbo setup is fundamentally flawed?

the fact it keeps blowing up indicates there is a problem with the setup/tune. trying to find rings that won't break is treating the symptom not the problem.

personally I wouldn't put a good bottom end under that setup until you have it sorted so that its not blowing engines up all the time. replace the one broken piston (or whatever the problem is this time) and have another go at sorting that setup and tune out properly. then build a good engine.

Dattogal, there clearly is something wrong if he can't CONTROl boost! Whether it's that the turbos are tired, they are outflowing their wastegates or the wastegate actuators are stuffed. The twin turbos have to go. There is absolutely no way that the turbos came with a 14PSI spring and diaphram from the factory so something needs attention. Maybe it is that he has just neglected the plumbing to the wategates and they are leaking?

ANd with the ring theory, you will be looking for ever if you think you are going to find a set of rings that will go straight into his motor and survive with the current set up. The rings are most likely going because of detonation because of too much boost and running turbos out of their efficiency range.

EDIT: beat me to it L18!

unfortunately i have no good advice to give on the topic..

but i would like to congratulate 1200rc on the success he has achieved so far with the twin turbo a series.

it may have its issues but its original and i have ridden in his old coupe and was very impressed with the power it makes..
and that was before it was efi...

keep up the good work mate


ps. just tryin to help keep you motivated

I think it would be wise to take alot of advice on here, heaps and heaps of experience talking on here, and as Rallycar said before he wanted advice from these experinced motor minded guys...

Good luck Rallycar keep the forced fed Aseries alive