So im doing the 2.4 edz swap with the 420a head. I was thinking about using the srt4 piston/rod combo but my car is going to remain n/a for about the next year. So wouldnt the CR be too low? Is there a preferred CR that would work for n/a as well as boost?.. And since im planning to boost it in a year will the stg 2 crower cams (turbo/non turbo) work for both setups...?

You can use the srt4 pistons and rods but it will be really sluggish due to the low compression. You can still drive it but it will not be a happy drive (im at a loss of words). I had the crower 2s and they were very nice for my n/a and will work with the turbo very nice read up on the cam discussion thread so much good info it will make you sick but in a good way.

Well thats what I dont want... I dont want it to be sluggish... Do u think the stock pistons would be able to put up with the boost?

It's really not about whether they can "handle the boost," but about whether they can handle the power. Every turbocharger produces a different increase in horsepower per psi of boost, so boost cannot be used as a measurement of power, or in the rating of parts.

Anyway, without knowing what you're goals and resources are, it's really not feasible to say what compression ratio you should run or what pistons to use.

I've been seeing questions like this a lot, and I've been asking myself a lot of them too, so I'm going to offer some of my own thoughts on the subject.

What I'm finding while researching my own 2.4 build is that every major decision you make about your engine should be preceded by at least six questions:

1) How much Horse Power do I intend to make?
2) In what RPM range do I intend to make the majority of that power?
3) How much fuel will I need?
4) What are my tuning abilities?
5) How often do I want to be fixing this thing?
6) How deep are my pockets?

Answering these questions will help you pick a fuel system, turbocharger, compression ratio, and pretty much anything else.

You're ability to tune largely affects what compression ratio you will want to go with. If you are an experienced tuner or have the resources to pay one, you can go higher compression and go after more power. If not, you can "play it safe" with lower compression. High compression builds are becoming more popular and what is considered "safe" is being debated more and more as a result.

Fuel is self explanatory, if you don't know for sure that you have enough, it doesn't matter what piston/rod combination you go with, it will blow. There are lots of articles in the wiki to help with that, but it's not directly related to your questions, so I'm going to skip over it for now.

How much power you make and where you want to make it are the big two for your questions.

Where/when you want your power made is largely a factor of what you want to do with the car and can also affect what compression ratio you would like to run. If you intend to have a quick car to drive around town, I would say build a car for the low-mid range rpms. The reason I say this is because you would likely be more concerned with throttle response than with overall power. You want to hit the gas and immediately start to make power. If you were building a drag car, I would personally say build for higher rpm power. That would probably allow you to make more power overall, but in a range you wouldn't hit very often driving on everyday roads.

With a high rpm build, you might select a larger turbo charger, and run as much boost as possible. For that type of build, a lower compression build would let them go higher boost with less tuning ability and may be preferable. I should note that higher compression adds power at any rpm range, but the ability to add more boost for higher rpm builds offsets some of the performance cost of low compression. A few guys are beginning to challenge the notion that high boost necessitates low compression, but these are mostly experienced builders who know how to tune.

With a low-mid rpm build, you would either want to make more power before the turbo kicked in by building the engine itself (one way is with higher compression), or add a smaller turbo, which would kick in sooner. Ideally, you would do some variation of both. Of course, guys building top end drag cars try to build power outside of boost too, but higher boost has a larger effect for them.


Now lets take a look at where those questions line up with piston selection.

Let's say your goal is a 500hp monster... forget the srt pistons, they are only rated at 400 hp and definitely forget the stockers. Lets say your goal is just a 200 hp daily. Pretty much anything would work, just depends on how much money you want to spend, how reliable you want it to be in the long run, and of course how soon you want to make power. Now, lets say your goal is somewhere between the two, a 250-300 hp street build (what I'm personally shooting for in the long run). SRT pistons can take the abuse, but without knowing the rating of the stockers, I doubt they could (I'm assuming they are rated somewhere around where the stock 2.0 ones are). With the SRT pistons, you're at a pretty low compression ratio, so it might be a little sluggish on the low end. It's probably a better setup for a mild drag car, but with the higher torque of a 2.4, it should be a reasonably fun street car too.

Of course, forged pistons and rods could easily handle that level of power, and would give you the option of higher compression. The deciding factors between the two there would be your tuning ability, and how much you can afford to pay. If you have the cash for forged pistons and rods and can tune for higher compression, it's probably the better build.

Then of course, there's question five and six. No one likes to talk about cost, but builds aren't cheap. Likewise, no one likes to breakdown, but it does happen. Forged pistons and rods are the most expensive options. They are also rated for the highest amount of power, making them largely more reliable. SRT pistons/rods are better than stockers, but not as good as forged. I would imagine the stockers are close to worthless in a high horsepower build. The classic contractor's triangle plays in here. Fast, cheap, reliable. Pick two. If this is a daily driver car, you're probably better off saving up longer and going with the most reliable option. If not, you can take more risks, but it may cost more in the long run too. Be prepared to pay to play.

That was a long rant, but hopefully you found it helpful. Sorry if it wasn't very clear, it's at least the fourth time I've retyped it. My cat has managed to close the window on me at least 3 times.

To quickly respond to OP's question. Why not build for boost and just accept the sluggish motor. An srt with no turbo would be the same way. Its sluggish b/c of the Low CR (8.0) iirc. Theres no reason to build for a happy meduim, when the end goal is boost. I also run the Crower NA stage 2s, they seem to perform very nice with boost. Honestly, unless your able to tune very accurately, theres no "happy medium" ita sll a balance, to give somewhere, you have to take from another area. Im running 9.0 CR, so my 2.4 feels about normal when no boost. Im also running MS standalone, so I can tune a more accuratly. I could have ran a 10.x CR and had better motor responce, but its wouldnt nessacerily give me the gains i wanted out of the turbo.. That balance thing again. Focus on your end goal. If its to be boosted, then build for it an accept the "slowness" in the mean time.

You can have cake and eat it to ( otherwise whats the point of cake?), but you cant hold a beverage, have cake and eat it.. lol

Questions 1-6 are pretty much what I ask customers.. Except 5 is more of a product of 1, and 1 is really whats your goal? That will drive the question of Reliability, which will define how much it will cost ( cheap/fast/reliable). The rest are more build detailed.. you already know youll be speinding money based on question 1 (goal) and question 2 (Reliability).

Well here are my goals and what im planning to get done:
Head blueprinting
Stg 2 crower (non turbo) cams, they should hold up fine with the turbo, right?
Adj. Cam gears
Port matching n polish
3 angle valve job
New 4g63 springs
New retainers
Crank scraper
Srt-4 oil and fuel pump
Undecided on injectors but most likely 2.4/srt-4 injectors.
Block blueprinting
And im now leaning towards the 9.0 CR. (need to research pistons)
Im pushing for at least 350 hp. But I wanna overbuild for about 450-500 hp in case I want to try something new.
I want the car to be reliable and just enough to beat some locals with their sr20's and b20 v's lol. and eventually in about a year ill boost the car. So there it is... Whats ur guys's opinion...

Read this: http://www.2gnt.com/?d=How_to_Choose_Fuel_Injectors
And then use this: http://www.rceng.com/technical.aspx

That much power is going to need a large injector unless you want to run high fuel pressure, which breaks shit.

If you are even thinking you might want over 400 HP, drop the SRT Pistons and plan for forged. At that point, super low compression is kind of a waste. The reason the stock 2.4's ran such low compression is because the engineers that designed it wanted to be able to handle 400 HP with cast pistons and rods. If you're not running cast pistons/rods, there's not much point in staying that low. My personal opinion is that you're on the right track with a 9.0 compression ratio. To meet those goals, you will definitely need MS, so you should be able to tune for pretty much any compression ratio available.

I think that's what I would do if my goals were that high. Personally, I just want a fun car to drive around, so I think 250-300 is a good range to be in. I want something fast, but still streetable. That kind of puts me on the fence between an srt setup and a forged setup. I can cheap out and still reliably meet my goals, but I'll lose some power when I'm not under boost, or I can pinch my pennies a while longer and bump my compression ratio up to 9 or maybe 10.5 assuming I can afford some dyno time and hit my goals pretty easily.

Thanks for the links. But I thought I only needed the MS if I was going to boost it. So can I run/buy the MS once I boost it...? as for tuning, road race is literally 2 blocks away from my house so ill be going to them for fine tuning. If I feel like it might be too much then I might settle for the 300hp mark. But for now the piston search continues. Thanks for all ur guys help...ill keep u guys posted.

1.
New 4g63 springs
New retainers

No. Get Crower springs and Retainers.

2
Crank scraper is good, but get the Windage tray and baffles as well, Esp if doing auto cross. Its cheap insurance you have oil control. Also look into the Oil restrictor.

3. 9.0 CR pistons are custom, they will not be an off the shelf item.

4.Yes MS is going to be important for you when you boost.

Over building isnt possible, i call it, buidling in headroom/insurance.. Im only running 9 psi on my Built motor and Head.. The only thing holding me back, is turning up the boost.

And traction lol runing low 9's in the 1/8th with .4 reaction times and no traction in 1st lol. Launch needs work , but still trapping 83+Mph. Not bad for shit launch and 9 psi.. With that trap speed i should be into the high 8's if i can hook and launch..

With that goal, id get some 700 range cc injectors, that way you have a good anmount of head room. But dont get them till you figure out your MS config. Might as well do forged pistons and rods... Build it right up front so when you do want to try something else.. your ready, you dont have to re invest in machine work etc..

You need MS if you want to get the most out of your build NA or boosted. Look at all the NA guys and see what they are running. Almost all of them are on MS or they are running some other tunable ecu like the afx. You can build a 2.4 using the stock fuel maps if you want, but you won't get as much out of it. To make the 300-400 HP you're looking for though, MS is pretty much a requirement. Stock fuel maps won't get you anywhere near there. You might be able to get there with an sfmu and a safc, but it won't be much cheaper and won't be able to tune as finely.

The combination I'm looking at going for is a 1:1 afpr, MS1, a Walbro 255 and larger injectors. That setup will work whether you are NA or Turbo, depending on the injector size. You just set the 1:1 and the fuel tables in MS differently since you won't make as much power NA.

Good luck with your piston/rod search. Take your time, plan everything out and I'm sure you'll do fine.

MS1 is dead.. At the least get MS2 v3.0.. or go with a MS3.

For na, i wouldnt bother tuning it.. IMO, save for a Nice MS and turbo setu, theres no reason to "tune" your built for boost N/A.. you will just be disapointed.

Like said above if your going to boost, MS is what you should use.
MS1 cannont do seqential injection. Its very helpful / more efficent, esp when using larger injectors (880cc+). Not to meantion feature differnce..

I run MSnS, full standalone with 1000cc.

My build can be found here.
http://forums.2gnt.com/dcboard.php?az=show_topic&forum=5&topic_id=134149&mesg_id=134149&page=

Good to know, thanks. I've read through your build a couple times, very clean.

Yea I plan on getting the MS once I boost it. But I will probably run the setup with the stock ecu until then. I hope to get it back up n running in the next 2 months or so. N at least I know that when I boost it n go MS I will be beasting... If I can get traction lol...

Tuning it is a whole nother beast.. Atuo tune is awsome, for me the Hardest part is setting Accell enrichments.. and IAC stuff. Getting the idle and Start up perfect i think it sthe biggest pain.

I found this on modernperformance.com it should help out a lot of people doing the 2.4 swap. http://www.modernperformance.com/category/s?keyword=Swap

im lost.. whats there that helps with the swap that already inst common knowlege? The forged pistons and rods are pretty common, and i dont see anything else there that helps with a Eclipse swap..

so heres a new question for the books. i'm working on my head at the moment and while making my parts list i was debating on whether i should go with stock sized valves or +1 mm oversized valves... do the oversized valves really make a big difference or am I ok with just buying oem replacements...? thanks

either will work. If going Turbo, id do OS valves.

i am eventually going to install a turbo but will that +1mm make a noticable difference..?

I wouldnt say yes in regards to the butt dyno. But it will help sppol quicker, also depending on cam, etc. It will give you an increase via effiancy. If your going turbo.. i see no reason not to. You should.

Whats your goal? To me, if your building a head.. u should. If your just running low boost and not going to push the setup, then its not really something id spend money on.

With the low comp 8.0:1 iirc the srt pistons are.. id say do it. Your turbo will be working hard. The os will make it more efficient at its job. Also upgrade the valve train for you cam u plan to use

i was going to do the 8.0cr build. but since then i have moved to a 9.0 cr build with +2 pistons

thats a little lower then what i run. i think youll enjoy it. whos making the pistons? since thats not an off the shelf CR.

the pistons are by CP. There is a local tuner company here who has a direct account with them and they gave me a good price. $500 for the 9.0 CR and +2 over. if your interested i can refer you to them and maybe you guys can work something out as well. ive been getting all of my parts from these guys and they have some pretty good prices.

That just for the pistons? not to bad for a custom grind. We may hit you up in the future if we need a custom CR piston. thx!