High Compression Pistons

[Tom03es]

A high compression piston is taller than a standard piston, correct? If so, at what point does the engine transition into an "interference" engine? Right now, the Protege motor is non-interference in stock form (at least the US-spec motors). Not that anyone plans on breaking the timing belt, but it's good info to have.

Also, what's the compatability of the long reach NGK spark plugs and high compression pistons? Or what is the ideal spark plug to use with higher compression pistons?

 

[Maxx Mazda]

It's not nessicarily taller, just has a different bowl shape. I believe they're still non-interference.

 

[amair001]

What would be the ideal piston to use in an n/a build for the FS-DE

 

[Maxx Mazda]

What would be the ideal piston to use in an n/a build for the FS-DE

The JDM FS-ZE pistons, available at your dealer. Part numbers are in the FAQ.

 

[amair001]

could elaborate? I dont know much about the compression of an engine and why its better to have high comp pistons for N/A and low comp for forced induction

 

[Maxx Mazda]

Higher compression equals more power, but on a forced induction setup, you want more room to cram boost into and prevent detonation, so you lower the compression. I run 8.5:1 pistons and a WAY thicker headgasket to get the compression down that much more. When you do your pistons (they're actually fairly cheap) grab a cometic 0.27" thickness head gasket, and it'll bump your compression just a hair more too.

You'll need EMS though, stock or MP3 ECU won't cut it.

 

[amair001]

Ive got a microtech standalone, I should be able to account for the higher compression with that

 

[Maxx Mazda]

Yes, you'll need to pull timing to avoid pinging. Protege garage also offers a set of milder 9.7:1 pistons, but if you have the microtech, go with the ZE slap sticks all the way!

 

[FunkRider]

The 99-00 1.8 pistons when used in the 2.0 will give you 9.7:1 compression.

 

[LordWorm]

The JDM FS-ZE pistons, available at your dealer. Part numbers are in the FAQ.

sif the JDM pistons are the best pistons you could use...

the correct answer to the question is.... "the highest compression pistons you can get, thats safe to use on the fuel that you want to use" (its not uncommon for high boost race cars on methanol to be running 12:1 or higher compression pistons.....its fuel that makes that kind of compression safe). every single piston manufacturer who makes pistons for turbo'd FS applications could just as easilly build high comp NA pistons..... all you need do is ask....



Biggest advantage of high comp pistons on an NA Motor is that you can afford more overlap... by increasing the number of degrees both the intake and exhaust valves are open (thus effectively dropping your compression again), you can take greater advantage of scavenging, and reduce pumping losses in the engine.

Its all a question of dynamic compression. higher static compression means you can run more overlap, whilst maintaining the same or simillar dynamic compression that you had before with less overlap and less compression....

 

[niky]

If you're getting high comp, why stop at 9.7? Hell, if you want 9.7s, I'll sell you my stock 9.7 pistons, and I'll get myself a set of FSZE pistons.

Man, I've hit a rut... Finished P&P, have got an intake cam gear in (still studying how to build an exhaust cam gear without getting the timing issues twilight was talking about), but we're still hamstrung at under 140 whp. (possibly 130 whp on the Dynojet)... apparently, I've hit a wall in the system that I can't get around. Don't know if it's the stock ECU limiting it, the terrible local gas, the intake manifold (ported also) or something in my exhaust... it's irritating.

 

[LordWorm]

If you're getting high comp, why stop at 9.7? Hell, if you want 9.7s, I'll sell you my stock 9.7 pistons, and I'll get myself a set of FSZE pistons.

Man, I've hit a rut... Finished P&P, have got an intake cam gear in (still studying how to build an exhaust cam gear without getting the timing issues twilight was talking about), but we're still hamstrung at under 140 whp. (possibly 130 whp on the Dynojet)... apparently, I've hit a wall in the system that I can't get around. Don't know if it's the stock ECU limiting it, the terrible local gas, the intake manifold (ported also) or something in my exhaust... it's irritating.

why stop at FSZE pistons? I fail to see why *everyone* thinks the FSZE pistons are the be all and end all. Custom pistons. Custom compression ratio. Raised wrist pin.....more RPM, MORE POWER.... FSZE is only going to be marginally better than what most have...even more marginally if you have something like the AU version of the motor which already has higher compression....if you are going to rip the motor down to swap out the pistons, spend the extra money on doing rods and getting some decent high comp pistons .... that way you a) get a more reliable engine, and b) future proof yourself against having to tear the motor down again if you want more power later.

as for your brick wall...what cams you running? the JDM cams are garbage in reality...especially when compared to some custom grinds, or billet cams....

I noticed a big time bog down at about 6000 rpm prior to swapping to bigger cams...engine now just keeps on keeping on until 7k....

 

[Sleepy]

Do you think the wrist pins could be raised 6mm so I could use FS rods in my FP?

How do we work out the max safe compression ratio for a given octane eg 98RON? I wonder because I had to advance the ignition timing ALOT to get decent power with the new cams, up to 20degrees before any knock, if the emanage is to be believed(sometimes I don't believe it).

Not that I can afford a rebuild yet, but maybe one day I'll HAVE to.

 

[LordWorm]

Do you think the wrist pins could be raised 6mm so I could use FS rods in my FP?

How do we work out the max safe compression ratio for a given octane eg 98RON?

Not that I can afford a rebuild yet, but maybe one day I'll HAVE to.

not sure - would need to look into it....

Max safe on 98RON? timing is the key.... but my grand plan involves *trying* 12:1 compression......on the street it will probably have crap loads of timing pulled - but drop tank + race fuel on the track will make it worthwhile....

another alternative would be methanol injection..

 

[Sleepy]

See the edit above- I've put craploads of timing IN, so I hope taking it out again shouldn't be too much problem.

 

[twilightprotege]

6mm would be right on the edge of possible, and i'd lean to probably not. i've gone 3mm (woops, secret out of the bag there) and that's going in to the ring recesses

 

[Sleepy]

Interesting, maybe a thicker head gasket to make up the difference? But that sort of stuff is out of my league for a while yet. No idea what I'm doing and no money to do it with anyway!

 

[niky]

I think you could run ultra-high comps with methanol injection. I've been looking it up, and it helps eliminate knock problems on huge ignition advances on pump gas. Turbo guys love it. It's so effective that if they run out of alcohol mid-run, they blow up their engines.

There's a guy who's bringing the stuff in to Asia from the US... and his kits are downright cheap.

He's got an alcohol injection unit that'll sell for under $350 (US) here in the Philippines. Lots of diesel guys getting it. Proven 10-20 whp on the dyno on non-CRDi diesels... obviously won't be as big an effect on NA gas, but it might be a great way to get around low octane problems on a gonzo NA build like yours.

A friend looked at it, said the injector nozzle and fittings look good, and he's impressed by the difference on the dyno, so he's purchasing in bulk for his shop to offer as upgrades on his turbo kits.

 

[Captain KRM P5]

while it may be possible to order the j-spec pistons in canada, we are not able to purchase them through the us dealer network

 

[LordWorm]

He's got an alcohol injection unit that'll sell for under $350 (US) here in the Philippines. Lots of diesel guys getting it. Proven 10-20 whp on the dyno on non-CRDi diesels... obviously won't be as big an effect on NA gas, but it might be a great way to get around low octane problems on a gonzo NA build like yours.

compression wont be a problem....even at 12:1...regular pump fuel will deal with it, with suitably backed out timing. Problem with the fuel isn't octane on highly strung NA Motors normally...its usually piston velocities outrunning the flame front of the fuel (i.e. pump fuel doesn't burn nearly fast enough....)....so for track days, i'd look at C16 race fuel....not for the added octane (although this certainly helps), but because it will allow the redline to be stretched far beyond what garden variety premium unleaded pump fuel can support.

the meth injection = handy if you then decided to push nitrous into the thing at crazy high compression.... it helps cool the burn down, and assists in keeping cylinder pressures a little less ludicrous. But with semi decent fuel, and enough room to back timing out theres no reason why 12:1 can't be run on the street without much other work....