Piston compression choice for turbo

[jakelandry]

I agree on the lower compression. Its easier to tune for those who don't have the tuning expierence or knowledge. Op, what are your power goals?

I have no tuning experence whatsoever and I aim for 225 on 8 psi with a 12:1 fmu hopefully but once I get used to a turbo car and get spare time I'm going megasquirt and I'm aiming for 300 then. I'm sure I'll eventually want to hit 400 however, but I won't go over 400 for sure.

 

[Slo2gen]

This is more dependant on the material used for the piston, rather than the fact that it is forged or not. Most forged pistons are hypoeutectic; low silicon content causes them to vary noticeably between cold and hot. 2618 pistons, such as those offered by JE and Wiseco, are very hypoeutectic. Wiseco's seem to slap less than the JE's, though.

4032 pistons, such as offered by Arias and Mahle, has much more silicon. These pistons are forged eutectic; typically not as strong as 2618 alloy pistons, but they expand less and are thus quieter.

The factory cast pistons are hypereutectic, and a different material than the block. It also suffers from expansion, but to a lesser degree than the others. These pistons could be forged for added strength, but the added benefits of forging are still limited by the alloy. Forging these is not very economical.



10.5:1 does require a bit more fine tuning, but it is very doable. Bullet made quite a bit of power on his boosted 10.5:1 420a. Zac's 10.5:1 turbo'd 420a made 400+whp recently. Both are (were) capable of much more, and I believe Zac is able to run pump gas.

Raising the CR of the pistons does the exact same thing increasing the boost does, except it does it all of the time. Less boost is required to make the same numbers, you spool faster, and make more power in vacuum, but the tuning window shortens.



He did say 117whp.

I didn't even have to go there, . Sheesh, anywho I could have made it to almost 400 on pump gas and been fine on 93 octane, could have went higher than that too but you would have to pull so much timing it would negate adding more boost. Most people don't realize how fast a 350 whp car is on the street, its very fast and lets face it, there are not many 2gnt's out there in the 350whp range. As I said earlier, in your situation get a set of JE "custom" standard compression pistons and you will be happy. Its a good compromise. I can't make people understand how much low compression sucks when out of boost or driving it without a turbo on it, but to each his own. And for the record Mark made over 520(I'm wanting to say 56X for some reason) on 10.5:1 although it was on race gas I think, and I was on E85 which imo is still pump gas

 

[Carter_95RS]

but E85 isn't at every station, I have found one station around here and that's in the next town over

 

[Slo2gen]

And...if you go with 9.6:1 you will be fine with 93.

 

[jakelandry]

And...if you go with 9.6:1 you will be fine with 93.

I'd be fine with 9:6:1 but I want the long rod kit for the extra rev, and it only
comes in 8:6:1 10 and 12... I'd love to run 9:6:1. Since the long rod kit is custom made you don't think I could call Howell and request 961 huh?

 

[Carter_95RS]

You can request them, might be a little bit more pricey since they are being made per order instead of mass produced.

 

[Slo2gen]

I say go with the 10:1 then if you must have a long rod. Its only .4 points of compression more, you'll be fine. As for turbo, if you are looking into 16g's I would go ahead and get a 20g. Are you going with a mitsu flanged turbo or are you going with a T3 flanged turbo? If your going for T3 then you might get a PM from me

 

[jakelandry]

I say go with the 10:1 then if you must have a long rod. Its only .4 points of compression more, you'll be fine. As for turbo, if you are looking into 16g's I would go ahead and get a 20g. Are you going with a mitsu flanged turbo or are you going with a T3 flanged turbo? If your going for T3 then you might get a PM from me

Lol man i know its hard for you 400 horse 420a guys to understand but some of us are on a budget . I have about 3800 to build the bottom end and turbo trying to save as much money as possible through the entire build cause theres always something else i want for my car. Id love to have a 20g, but i think it would be ignorant for me to run out and buy that big of a turbo when i have no turbo experience whatsoever. Provided its within my price range i plan to buy zatomz "evo3 16g ported hotside and clipped" when he is through trying to beat the hp record on it. Im not trying to have your setup i want to learn before i go drop that kind of money so i plan to just do a basic turbo setup with an evo 3 16g and the basics, but its all still overwhelming, its just like the more i read on here the more i get lost. Sometimes i sit here for hours reading when i have time, i cant wait to get boosted, but i have to decide on a CR before i get the exact numbers i can drop on the turbo part of the build.

 

[Slo2gen]

Lol man i know its hard for you 400 horse 420a guys to understand but some of us are on a budget . I have about 3800 to build the bottom end and turbo trying to save as much money as possible through the entire build cause theres always something else i want for my car. Id love to have a 20g, but i think it would be ignorant for me to run out and buy that big of a turbo when i have no turbo experience whatsoever. Provided its within my price range i plan to buy zatomz "evo3 16g ported hotside and clipped" when he is through trying to beat the hp record on it. Im not trying to have your setup i want to learn before i go drop that kind of money so i plan to just do a basic turbo setup with an evo 3 16g and the basics, but its all still overwhelming, its just like the more i read on here the more i get lost. Sometimes i sit here for hours reading when i have time, i cant wait to get boosted, but i have to decide on a CR before i get the exact numbers i can drop on the turbo part of the build.

I understand completely, you have no idea . What manifold do you plan to run that supports a MHI flanged turbo? (a custom tubular or log mhi flange is your only option) I'm not trying to convince people to have a 400whp set up, I just dont want you to make the same mistakes that I/others have. I had a low compression motor and HATED IT. maybe it was just me, maybe it wasn't. Just like throwing that info out there, in the end its your car...do as you like. I completely understand doing your own thing, hell I drive a 420a powered car. And I also don't want you to spend a good bit of money on a turbo to turn around 2 months later and wish you would have gotten a bigger one. IMO the 20g is about the perfect street turbo, not much lag but still has potential to take you into so really good power.

 

[necrotopsy]

i like my t3/t04e 50 trim personally.. but I'm going to switch to a gt32 for faster spooling and being able to efficiently run more than 22 psi.... i run 26 for the track, but its pushing the limits.

i drive a lower compression 420a, and it seems fine to me. i also own another 420a and that ones stock so i have a good reference. i can only tell the difference from a stop. but if i just rev a little higher before releasing the clutch its just as good IMO.

 

[Carter_95RS]

Its going to be hard to get a cast log manifold that is MHI flanged, to my knowledge no one makes one for our cars anymore so you might have to use a manifold with mhi adapter

 

[jakelandry]

I understand completely, you have no idea . What manifold do you plan to run that supports a MHI flanged turbo? (a custom tubular or log mhi flange is your only option) I'm not trying to convince people to have a 400whp set up, I just dont want you to make the same mistakes that I/others have. I had a low compression motor and HATED IT. maybe it was just me, maybe it wasn't. Just like throwing that info out there, in the end its your car...do as you like. I completely understand doing your own thing, hell I drive a 420a powered car. And I also don't want you to spend a good bit of money on a turbo to turn around 2 months later and wish you would have gotten a bigger one. IMO the 20g is about the perfect street turbo, not much lag but still has potential to take you into so really good power.

Im going to fab my own log style if possible. Thats my game plan anyway although id prefer a tubular cause they look so damn cool. As for turbo choice i just want a evo 3 16g cause all i hear is good about them and they are cheap. And thanks everyone for all the good info here, theres way more than i ever epected to get and i do appreciate it.

 

[Carter_95RS]

Tubular would be much better, performance wise too. It has been proven that they out perform log style manifolds. They're just more expensive..... but you get whta you pay for.

 

[jakelandry]

Tubular would be much better, performance wise too. It has been proven that they out perform log style manifolds. They're just more expensive..... but you get whta you pay for.

Yea i know ive actually considered buying like an obx and cutting the t3 t4 flange off and putting the appropriate one on.

 

[Carter_95RS]

Do a search on here about the OBX ram horn manifold, i doubt that you will like the results you find. It comes way to close to hitting the thermostat housing, the wastegate location is less than desirable in relation to the turbo position and the turbo location isn't all that great either. From my understanding the runners don't line up with the flange very well either, to me it sounds like a poorly designed manifold that probably never got any type of R&D which is much needed on a part like that.

 

[jakelandry]

Do a search on here about the OBX ram horn manifold, i doubt that you will like the results you find. It comes way to close to hitting the thermostat housing, the wastegate location is less than desirable in relation to the turbo position and the turbo location isn't all that great either. From my understanding the runners don't line up with the flange very well either, to me it sounds like a poorly designed manifold that probably never got any type of R&D which is much needed on a part like that.

Well id be more than happy to fab my own if i knew where to get that kind of piping.. oh while were at it i have another question, im planning on getting a HUGE fmic and i mean huge to fill my stupid front bumpers huge hole in the center, is it possible to be so big it kills off boost?

 

[Carter_95RS]

Well id be more than happy to fab my own if i knew where to get that kind of piping..

Yes, you can make you're own manifold. There are a few places who sell raw materials such as pipe, collectors, mandrel bends and such. I'll see if i can find you a link.

is it possible to be so big it kills off boost?

Yes, an intercooler that is to big will create additional lag. There are plenty of fmic's that will fill the bumper, and be big enough not to heat soak on your set up with your power goals.

 

[jakelandry]

Yes, you can make you're own manifold. There are a few places who sell raw materials such as pipe, collectors, mandrel bends and such. I'll see if i can find you a link.



Yes, an intercooler that is to big will create additional lag. There are plenty of fmic's that will fill the bumper, and be big enough not to heat soak on your set up with your power goals.

Well it Would have to be like 32x10x?, which running 8 psi I don't think that would work well...

 

[necrotopsy]

i recommend the HAHN racecraft big core fmic. that's what i have.

and listen. you want 8 psi now. after a week or so of driving it like that, the boost bug will have bitten you and 8 will NOT be enough anymore. shit i run 26 and i dont think that's enough. so build your set-up so you don't have to keep buying more and more parts to keep up with the build.

a bigger fmic now will save you from having to buy a bigger one later.

 

[Carter_95RS]

That may be a bit excessive for 8lbs of boost. Here are my intercooler specs, i believe these are right.

Full Size: 27.5''x7.0''x2.5'', 2.5'' Inlet/Outlet.
Core Size: 21.0''x7.0''x2.5''.

(i'll post a picture when i can. The internet here is craptastic and wont let me load attachments)

I see 7lbs of boost usually by right around 3000 rpms on my t04e 50 trim. It doesn't quite fill the bumper up, but with my car being as low as it is, you cant really tell. I just put some gutter guard infront of it anyway so you cant see any of my intercooler or piping unless you know its there, i like having a little surprise for unsuspecting victims.

 

[jakelandry]

i recommend the HAHN racecraft big core fmic. that's what i have.

and listen. you want 8 psi now. after a week or so of driving it like that, the boost bug will have bitten you and 8 will NOT be enough anymore. shit i run 26 and i dont think that's enough. so build your set-up so you don't have to keep buying more and more parts to keep up with the build.

a bigger fmic now will save you from having to buy a bigger one later.

Yea your right, but im not on that kind of budget, i have to quit my job next quarter from school so im dead set on my $3800 and i have no clue how much all the machine work will run me for my bottom end. Ill have to think up something for the fmic though cause i dont want it to all look ghetto since i just painted and as of now the front bumper area is my weak point on appearance.

 

[Carter_95RS]

Holy hell batman! Those are expenisve.you can get an ebay fmic for ~150 bucks and holds pressure just fine

 

[necrotopsy]

yeah... the core is --24X9X3.5-- and it supports 700 HP. $630 i guess that is a bit much for his price range...

 

[jakelandry]

Well, as much as I dont want to do it it's beginning to look like I may be better off not
getting the long rod kit and just peicing my own kit together so I can get 9 compression and save a few bucks I can spend elsewhere, though I bet being able to rev past 7500 rpm would be amazing...

 

[Carter_95RS]

You don't need a fmic that big, anything thing that is much higher than 400hp. Anything over 350-400hp is a lot for a fwd street car.