10.5:1 pistons

[2_fast_240]

Can anyone tell me if there are any modfications needed to put 10.5:1 CR pistons in a ka24de. Also does anyone know if you could run a turbo at very low boost (4 psi) on these pistons safely.

[ranisron]

I think the 10.5:1 pistons (i.e. JE) for the Ka24DE is specifically designed for high compression N/A, not for boosting use. Somebody corrects me if I am mistaken.

So, don't run any boost on it.

[i8yourfwd]

uh generally for boost.. you'll want lower compression.. lol

[SR20d2fourT]

Yeah, you can run them...not safely though. Get low compression pistons if you want boost. Guys that run on the KA w/high compression and boost generally dont have a nice time finding out that they have to buy a new one. Goodluck.

[!Zar!]

Running high compression pistions and boost is like drifting a honda civic. It's possible but still a stupid idea.

Answer, it's possible but it isn't safe.

[SoSideways]

It's safe if everything was built around it, and have a tune with a good EMS to back it up.

Precision is the key here.

[SpeedMonkeyInc]

It's safe if everything was built around it, and have a tune with a good EMS to back it up.

Precision is the key here.

That is true. However, you would still be stuck at low boost, even with race gas.
If your goals are low HP engine with a small and responsive turbo then it would be fine. But you can do that with the stock KA so whats the point?

[wootwoot]

If you're gonna be using methanol instead of petrol go for it
It is possible, but you're combining two things that dont generally go together very well. What are your reasons for wanting to do this? Goals?

[g2ic02]

the integra gsr has 10.5:1 compression ratio and they take to boost really well. With the increased compression ratio you can make more power at lower boost levels. Who just puts in high compression pistons. You don't, you build up the whole motor. With a good tune that would be a fine setup. I would say not to go above 7psi on that setup. At the same time if your building your motor up and want a turbo. You would make more power to build up a lower compression motor and throwing a gt28rs or t3/t4 running about 15-20 psi. I would rather do that personally.

[SoSideways]

^^^ exactly

I'd name another motor that'll blow all of you guys' minds, but I'm not even sure if I can say anything about it, but trust me, you guys will drop your jaws.

But yeah, think of the boosted S2000 engine. Those are like 11:1 CR stock (maybe even higher, I don't remember off the top of my head what the exact CR is for the F20C), and people have put 7psi or so on turbos and superchargers on them, and you don't see them blowing up like, immediately upon the first time it boosts.

It's all in the way you have built your motor and set it up for boost, and have a GOOD TUNE. Cannot stress enough on a GOOD TUNE.

eBay ROM tunes != good tune

An entire day at the dynos with a reputable EMS and someone like Enthalpy tuning it = good tune

[2_fast_240]

my reason for wanting to do this is i am rebuilding an engine to put in right now and need to get some new pistons. i would like to turbo it in the future but dont have enough money now. for this reason i dont want to have low comp. pistons in there while it isnt turbo because it will be very slow. so if possible, i was hoping to put high comp. pistons in it now and add low boost to it later.

[wootwoot]

Look into Cometic headgaskets and find what sizes they offer. You could switch that out relatively easy when/if you go turbo later on

[punxva]

whoo, i didnt think lowering the comp. ratio would really affect ur NA performance that much... Plus once u rebuild the engine will make more power no matter what pistons u use, than it did before so you wont notice a difference between the low comp and high comp, unless ur old engine was like brand new, or ran 100%

[gotta240]

punxva- your clueless buddy. I'm not trying to be a dick, but you should learn more about engines before trying to teach/explain anything.

WTF!- "once you rebuild your engine, you'll be making more power no matter what pistons you use" BULL.

Have you ever drove a car with an 8-1 compression ratio, WITHOUT boost? Not fun. Not powerfull.

A NEW ka24 with a 8-1 comp. ratio, will be slower than a 100k. mile STOCK ka. Think about it... The only reason an older motor is slow, is because there is a larger ring gap, between the rings and the cylinder walls. The blowby causes loss of power..

[SoSideways]

Dude you'll be alright with high compression and boost.

Just make sure when you go turbo, to save up for a good EMS and a good tuner (not a t00n3r) that knows what he/she is doing (not gonna be sexist, but ahem, we know better).

You'll have less of a margin of error to keep your motor together at 10.5:1 CR ratio, but it's do-able with a good EMS and good tuner.

[2_fast_240]

Alright, i think these are my last questions. what kind of gas do i need to run with the 10.5:1 CR pistons. will i be able to just run the highest octane pump gas? Also, if i get some performance cams will i have to worry about the valves hitting the piston?

[gotta240]

Just dont do it if your going to boost. Its fucking retarded, pointless, and a waste of energy/money.

ITS DUMB.

Either go all motor(with at LEAST 11 or 11.5-1 ratio) or build for boost with 8 or 8.5-1 ratio..... Stop bullshitting around it, and stop trying to go both ways.....

[2_fast_240]

hey GOTTA240. If you had read what i said earlier in the post you would know why i am trying to do this. because right now ur just telling me what i already have considered and cant or dont want to do. so either answer my question or dont even write anything and make me waste time reading it. im not asking for you to tell me what to do with my car, im asking for information on what i am doing with my car.

[gotta240]

Then dont waste the time with RETARDED threads. Everyone on here has answered your question the same way i did...i'm just being more honest/upfront about it.

Besides...i wasted MY TIME trying to help save YOU TIME and MONEY.

soooo.

Go read some engine building books, or research it on the internet. Do you even know WHAT TYPE of 10.5 pistons your going to use? And no..you shouldn't have clearance issues......Its not like your running 13-1 comp. ratio with domed or prolly even flat top pistons....

ALSO- WHY THE FUCK would anyone go through the time, the hassle, and the waste of money to throw a turbo on a car and ONLY boost 4 psi? Have you ever owned an AFTERMARKET turbo car? They are a lot harder to keep running, and require a larger knowledge of engines than you apparently have.

THERE. im done wasting my time on your noob ass

[wootwoot]

Man quit being a tool...

What would be your best option in my oppinon is to stick with stock compression, 9.5-1
You can still boost moderately onn this and obviously will not hurt your performance at all.

[krustindumm]

boost is like free compression. Heat causes detonation, compression causes heat, so if you can compress it then cool it (intercooler) then compress it again it's almost free. So why not compress it alot more before you cool it, and a little bit after you cool it and keep things safe instead of trying to *forge a new path* that no one uses because physics already proved it was a bad idea.

Alot of boost on low compression will be safer than little boost on high compression.

[2_fast_240]

Alright GOOTA240 is pissin me off. What im tryin to get through to you thick headed fucks is that im not trying to build an engine the conventinal way. im just tryin to get wat i want out of the car when i want it. im not trying to be a proffesional fuckin engine builder here. im just tryin to satisfy my needs and was asking some simple questions about what im going to do with my little stupid pointless project. all i wanted was some technical advice on wat will and wont work when im puttin this thing together. now i think ive got all the answers so i aint botherin anybody anymore about my dumb engine build. even tho it took a bunch of slandering and shit to them

[wootwoot]

Just dont do it if your going to boost. Its fucking retarded, pointless, and a waste of energy/money.

ITS DUMB.

Either go all motor(with at LEAST 11 or 11.5-1 ratio) or build for boost with 8 or 8.5-1 ratio..... Stop bullshitting around it, and stop trying to go both ways.....

8-1 is stupid fucking low for boost on a sr20 or ka24 motor, most people like to use 9-1.
Do you know what you are talking about?

[gotta240]

First off... I'm not an engine builder.....BUT i've been around cars and engines long enough to know that 10.5 to 1 is plain fucking stupid for a turbo motor.

And yes... i basically do know what i'm talking about.... First i said 8 to 8.5. Wow...thats A LOT different than 9-1....right?

Stop trying to be a technical jackass.... No one specified HOW much boost was going to be run, or WHAT SIZE turbo..... I'd take an 8.5 (or even 8-1) comp. ration turbo motor, over a 10.5-1 turbo motor ANY DAY. Thats all i was saying....and hopefully he got the point....

[atom]

Just save your money and do it all at once. You're just half assing it if you do it piece meal like you want. 10.5:1 isn't ideal for turbo, period. And don't compare it to hondas or whatever cuz the engine design is different, detonation threshold is different, blah blah. Rebuild it with stock compression and turbo from there............

[2_fast_240]

First off... I'm not an engine builder.....BUT i've been around cars and engines long enough to know that 10.5 to 1 is plain fucking stupid for a turbo motor.

And yes... i basically do know what i'm talking about.... First i said 8 to 8.5. Wow...thats A LOT different than 9-1....right?

Stop trying to be a technical jackass.... No one specified HOW much boost was going to be run, or WHAT SIZE turbo..... I'd take an 8.5 (or even 8-1) comp. ration turbo motor, over a 10.5-1 turbo motor ANY DAY. Thats all i was saying....and hopefully he got the point....

thats cool that was all you were trying to say, but i didnt put up a post asking what kind of motor you would prefer if you were building one. and i did say i was planning on around 4 psi if i did do it. obviously im not getting a big turbo for that. all im trying to do is get some decent power out of it right now, and down the road i might want to consider getting a little more out of it. i just want to kno if it was possible. its not like im tryin to build a 300 hp motor here. so in conclusion, i dont see why you are going to come in here and be a dick telling me things i dont want to kno. if you think its a stupid idea then dont even bother discussing it with me.

[S14DB]

First off... I'm not an engine builder.....BUT i've been around cars and engines long enough to know that 10.5 to 1 is plain fucking stupid for a turbo motor.

And yes... i basically do know what i'm talking about.... First i said 8 to 8.5. Wow...thats A LOT different than 9-1....right?

Stop trying to be a technical jackass.... No one specified HOW much boost was going to be run, or WHAT SIZE turbo..... I'd take an 8.5 (or even 8-1) comp. ration turbo motor, over a 10.5-1 turbo motor ANY DAY. Thats all i was saying....and hopefully he got the point....
So, Basically you have no real knowledge. You're just stating and restating your opinion over and over again till hopefully someone takes it as fact?

[RBS14]

If you have the engine management and a good tuner, higher compression in a boosted engine will actually produce some great results. Like stated above it will make more power at lower boost pressures. It will also spool up the turbo sooner. And in addition to that it will start making good torque before the turbo spools because of the compression. As long as you aren't intending to run like 2 bar of boost, you'll be ok. But remember, DON'T try this without a standalone and a really good tuner.

[wootwoot]

People never run turbo kits on stock motor 350z's, s2000's, Civic SI's, RSX's, SVT Focus, etc because their compression is to high (all of those are above 11:1 I believe). Oh wait a minute, yeah they do. You just have way less of a margin of safety so if you're tuning is a little bit out you can fail much more easily. You also reach the stress failure point of the parts faster/more easily. Stick with stock compression ratio though it just makes more sense!!

[SpeedMonkeyInc]

I am wondering if an aspect of all those high compression engines mentioned is that they are all designed from the factory to run like that. Surely newer technology in combustion chamber design helps? All those engines need to be ready for Joe Schmo to put 87 octaine in and still drive full throttle everywhere right?
I don't know, just wondering. The KA combustion chamber design is pretty old now.

[S14DB]

Don't forget the 2ZZ Celica.

It really has to do with your Effective C:R. Actual C:R+ Forced Induction. Most modern motors start failing around 18:1. So, a C:R +1 or 2 isn't as major as one thinks.

Also, Pentroof and cyl design has changed radically since even our motors were designed. A lot of the 8.5:1 fokelor comes from OHV V8's that have horrible quench areas and are comparatively prone to pre-ignition. 10:1 and 11:1 are race gas only territory. Has anyone seen the piston on a SRT4? Looks like it's from a High C:R NA Race motor. Not a turbo street car.

What I'm trying to say is that people here are arguing Apples and Oranges. Our KA's are more modern than SBC's but not as radical as 305z, K-Series, 2ZZ's. They run great to 400ft/lbs @ 9:1. When the thin ass ring lands give way. Certainly can handle more power with better piston design.

On the subject of Piston Design. Most 8.5:1 pistons dish out. Keeping the flame front away from the ring lands. At the cost of some of the quench characteristics of the head. How do the 10.5:1 raise the C:R? Do they just make the stock piston taller? You can do that by decking the block. Or do they raise the center of the piston to match the shape of the head?

My point is that there are lots of things to consider when changing the C:R of a motor. The Head and piston design are more important than any general rules.

[gotta240]

Well, well put