Piston machining

[Chimp]

Common practice it seems, especially with cossies to lower the compression. Since im hoping to get my engine out, I am hoping to get the pistons machined to drop the compression a bit. (at £20 a piston its cheaper than 600 for forged jobbies) and chuck a set of rings in. Anyone done this before on a 200? if so how much needs to be shaved off?

[Jez]

Im not expert in this at all but I thought the reason you'd want forged pistons is mainly because they are a lot stronger and resistant to high temperatures.

They tend to be manufactured to provide less compression on a turbo'd car so you can run a higher boost and hence more power without detonation.

Maybe some std pistons are stong enough to take the extra boost and have some material removed but I wouldn't have thought it'd be very safe.

Maybe you should wait till someone know what they're on about answers you question - these are just my thoughts.

[Chimp]

aye, Im seeing a bloke tonight about the stuff. If I get any handy info I will post it. From what I understand though, reducing the compression via having the pistons machined is as idjit proof as having a set of forged ones put in, the chances are equal to kill both. If boost temperatures are kept down then it will be fine. Quite an exact science in determining the "dish" of the pistons though I believe. Im certain its common practice on fords but im unsure about Nissan.

[Chimp]

let this thread serve as a warning, I just spent 2 hours talking to this bloke about compression and stuff in the pub. I nodded off twice. Complicated business, think I will just go for a new set of rings. I understand the concept, I just dont envisage me needing to run a t4 on full chat.

qoute of the night:
clever man:"the last nissan i upgraded blew up"
me: I see, anyway i better be going...

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Dan
Red S13
Actuator/chip/filter/Mong00se
http://animatedgif.net/animals/otheranimals/ape_e0.gif

[This message has been edited by Chimp (edited 19-06-2001).]

[Matt_S]

Why not use an uprated head gasket - All the Jap companies do them. They start at about the £100 mark + vat. Or (although I dont think I'd do this myself) double up on the OE nissan jobby.
Either way, you'll drop the comp. ratio enough to run higher boost without as much detonation risks.

Matt

[Chimp]

yep, I will prolly stick a chunky head gasket on during the rebuild, although depending on the condition of it when i take it off, I might have it skimmed. So its swings and roundabouts innit. My head hurts thinking about stuff, wish id bought one off you lot thats already done http://300zx.co.uk/200sx/ubb/tongue.gif

[olly200sx]

All those ways will lower the compression ratio, the reason for lowering it is to run more boost, the best way to do this is to fit forged pistons for the very reason that they are much tougher and can be made for the correct size to lower the compression helping to ward of detonation !!!

Why not get some oversize, lower compression forged pistons and have the capacity increased slightly, giving more torque off boost and get it wire ringed at the same time to help the head gasket.

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S13 - Lots of Mods

[Chimp]

because forged pistons cost alot. http://300zx.co.uk/200sx/ubb/tongue.gif

[SteveSadler]

I say if ya gonna do the job, then do it properly, especially when your talkingabout YOUR engine.

The last thing u'd wanna do is cut costs and ended up having to do the whole thing again!

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Bayside Blue S13.
Janspeed&D-Cat Pipe/Pace FMIC/BMC F1 Filter/Standard T25 @ 15psi
15.4 @ 98mph - North Wield Air Strip
Flywheel Figure 213bhp/209Ib ft @ 5375RPM
Power at the Wheels 166bhp
(as of 15/6/01 @ Power & Engineering)

[A8-RICK]

wont getting the head skimmed raise the compression ratio?

would skimming the head be a bad thing in this respect, youve got me thinking now coz when i got my head reconditioned, it was skimmed and it has the standard thickness head gasket on it.

would this limit the boost i can run, in comparrison to before

[Chimp]

it would increase compression, yes. By how much i dont know, depends if the head has been skimmed before I guess. Just keep running it on super unleaded! Unless its pinking then i wouldnt let it annoy you.

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Dan
Red S13
Actuator/chip/filter/Mong00se
http://animatedgif.net/animals/otheranimals/ape_e0.gif

[JCD]

The thicker MHG's seem to work fine with our engines but they shure decrease the effect of the squish band.
In that the lower compression pistons (forged or not) are better. They can preserve the same squish clearance.
Anyone tried to machine the stock pistons for lower compression?

[Vipers]

u'll prolly be better off getting some of the wiseco forgies that brens aranging a group buy on for £375. includes rings etc. so in effect u'll be paying £300 for the forgiesm cuz u would have been buying the rings anyway.:Plug:

[Jezz_S13]

my god where did u dig this up from??

Yes someone did this, taff was is name and I think Steve Sadler bought his engine.

[Pete C]

The 205 GTi Turbo Technics conversion uses the original XU N/A pistons machined to lower the compression ratio, which I would have thought is dodgy to say the least! :eek:

But then they do only run 10psi boost max.

[JCD]

u'll prolly be better off getting some of the wiseco forgies that brens aranging a group buy on for £375.
Wiseco has a very good reputation, so does Bren:thumbs:
I was just looking what the alternatives are.
Anyone knows what the brown coating is for on the stock pistons?

[bren]

Cossy run forged pistons, s13s dont so you cant compare Cossy tuning to stock S13 internals ;)

[Yak]

Originally posted by bren
Cossy run forged pistons, s13s dont so you cant compare Cossy tuning to stock S13 internals ;)

That's what I thought. So cossy pistons would be stronger to begin with.

[Vetal]

I think pistons for CA18DET can be custom made for around 280-320GBP. Don't remember if it's with rings though...