HC pistons from corksport

[Installshield 2]

HC pistons cause a somewhat exponential gain...meaning a bump from 9:1 to 10:1 may come to be around 10whp when properly tuned, everything else being equal...But a bump from 9:1 to 11:1, will be over 20whp...and 12:1 is even more than 30whp...

I don't want to bring this one up too too much, because it is still very early in the build...But I have an FS with aluminum rods and pistons (with right around 12:1 static CR currently) making around 185bhp...only other mod being the J-spec cam set, and tuned off of a Motec...Remember though hp is a funtion of revs...and that output was created at 7500rpm...something I would not recommend with just a set 12:1 pistons...so If I only installed the cams and pistons, i would not have been able to rev as high reliably, thus most likely not reaching that peak...

But any HC upgrades are pretty much worthless when you can't change the engine controller...You will just make a few whp possibly, making it not worth the investment at all...and you could potentially create some large detonation problems...

The octane rating of the gas used is also directly related to tuning...If it is properly tuned you could approach 13:1 CR with 93-94 street gas...but if it is poorly tuned, you could run 104 leaded race gas all day, and still have a grenade...

 

[Gen1GT]

If miatas have 10:1 pistons factory (what's the overall ratio?), what type of fuel does mazda recommend?

Yep, 2001+ Miatas need premium. You could run regular of course, but the engine would pull timing, and you'd be down on power.

If you're worried about the affect of using high compression pistons, and can't afford the high-octane fuel, I suggest you find a new hobby (drinks)

 

[iluvmacs]

Kyle, why did you have ping problems at stock compression on 91 or worse?

Iluvmacs, Actually, I get better mileage out of 93 octane on the highway.

You should, but you have to pay more for the gas. For the same money you could get more cheap gas. That's all I was saying, which really doesn't matter to this post.

sorry

 

[Gen1GT]

Ya, compression doesn't give you the gains people think it does. Going from 9:1 to 10:1 isn't a big difference. You have to go from 9:1 to say 13:1 to get great power gains, like Install said....and like Twilight says, you'd big cams to keep dynamic compression to a minimum. Sure, you can run 13:1 on the street, as long as you have 300 duration cams.....

Here's yet another good calculator everyone should add to their favorites...

http://www.bgsoflex.com/crchange.html

Just from me going from my 8.8:1 compression to 10:1, will add a lowly 4hp to my 117. Considering the .5mm overbore, and it may be 6 or 7hp from changing the pistons. Every little bit helps though......

 

[mp3moose]

^^I like that little tool.

 

[akhilleus]

wow!! thats not much at all. i did stock 9.1 to 10.7 and there was only a 5hp gain...I would have expected much more.

 

[Gen1GT]

The advantage of higher compression is the ability to use more agressive cams. Compression in itself is kind of overrated in it's ability to give you more power. Increasing Volumetric Efficiency is the key...

 

[mp3moose]

Damn, it must be cam time for me.

 

[shinzen]

As we all should realize by now- your mods should be carefully chosen to work well with the other mods- else you will lose hp not gain it- on the flip side of what gen1 said, the reverse is true as well- more agressive cams without the high compression to back it up will yield less results.... Now that I think about it, I wonder if that's part of the problems that andrew is having with his dyno's.... Bears looking into

 

[Gen1GT]

As we all should realize by now- your mods should be carefully chosen to work well with the other mods- else you will lose hp not gain it- on the flip side of what gen1 said, the reverse is true as well- more agressive cams without the high compression to back it up will yield less results.... Now that I think about it, I wonder if that's part of the problems that andrew is having with his dyno's.... Bears looking into

You're SOOO right, and this can't be stressed enough...all of your parts have to work in conjunction with each other. You can't have one component trying to open up your powerband above 6000RPM, when you've got another mod helping your low-RPM velocity...you could be down on power all around...

 

[Glowspeedp5]

Since you have 10.7 to 1 deck the head and raise the com pression. Also I recommend the ES and Protege5 with the 2.0 to get an MP3 reflash...

 

[twilightprotege]

a reflash isnt that easy to come across unfortunately...

 

[flat_black]

Yeah, I was gonna say; If you can get me a reflash, awesome! Otherwise, I'm still saving up for the MPi Tuner. =) Hehee.

 

[shinzen]

A free reflash would be nice, but with a perfect power(hopefully) or the mpi tuner, you could control the A/F and timing, and accomplish the same thing, only specifically for your application, which could change depending on the mods- Basically the mp3 'puter leans out the A/F mix and advances the timing by 10 degrees- which may or may not be suitable for your modifications. it will take some messing with to get the right results, but I think we are on the right track here.

 

[akhilleus]

I keep hearing about mp3 reflashs.....when i looked into this at the dealer they had no idea how to do it...if it was even possible... but apparently it is... damn i wish i could find a dealer and an mp3 that could help me out.

 

[Installshield 2]

If you are going for large compression increases...You can't go with a reflash, and I wouldn't even recommend any type of piggy back...basically a full accurate standalone is the only way to squeeze a lot more power...

Josh...I don't know about that power calculator...It leaves out so many variables on making power...It does help to point out that compression increases are not all that is needed...But it does not allow for the tuning changes needed for compression increases (the reason a standalone is needed)...

It even mentions on the top that the webmaster has no idea of its accuracy, but that it was simply a formula found in some magazines...

But if it is truely showing compression increase numbers, with everything else held constant...it illustrates that you have to be able to tune it, and adjust cam specs/timing plus a slew of everything else to get the big numbers...It is showing a bump from 9:1 to 13:1 netting 13hp...that is not true if you held everything else constant on an FS...You would simply be down on power everywhere, mostly due to ignition timing and fuel parameters...I don't know, just ranting I guess...

 

[akhilleus]

yeah but not many people will be doing over 11:1...

 

[shinzen]

Well something to think about here guys- the FS-ZE motor puts down 170hp at the crank, a whoppin 40 more than we do. Part of it has got to be the pistons- then the IM, cams and ECU- kill one cat for overseas and there should be a pretty serious increase. That is also an unmodified ZE motor, so with proper tuning, intake, exhaust, and piggyback there should be no reason we couldn't make some serious hp with those pistons- if done right
I guess the moral here is still do the rest of it and see where it goes... If the MP3 reflash could be done for free by a local dealer- go for it, but don't rely on it for big gains

 

[igdrasil]

Changing pistons???

Well...its not an easy task:

1. You WILL NEED TO REMOVE THE HEAD!!!! to pull the piston/con rod assy.
2. You will need to remove the crank assembly to remove the rod bolts.
3. You will need to move the transmission off the block a few inches to reach some bolts that attachs the crank to the block.


Some advice...DONT PAY that amount of money for those HC pistons...just get the 1995 protege 1.8L pistons...they are high compression on our engines!!!!...

They are the same that corksport sells. But I can get them for MUCH less...($20 ea. sounds good?) of course....used!

If you want some pictures of both pistons, let me know. We are already doing this..

 

[p5sundevil]

yes post pictures of course! jeez like we NA addicts here wouldnt want to see if that is possible. would be very nice.