Okay to run original ETA pistons with 885 (i) head if I'm going to turbo?

[jc1000]

I’m currently using the eta pistons with 885 head. I live at high altitude so the deficiencies are more noticeable, especially with turbo. So I’m going to build a not-budget stroker, lol. And I wish I had used the “i” pistons from the start.

That said, I 100% agree with hasa in this case, and although I want a different setup now, that’s exactly why I went with that in the first place. I had to draw the line in project budget and scope to focus on other aspects, like engine management.

Hi there, following up about a year later lol. You said you wish you had used the i pistons. Is it as simple as swapping out the e ones for the i ones? Or is there more to it than that?

mikey.antonakakis

[jc1000]

By using the b25 pistons, eta rods/crank and shaving the block 2mm puts you around 180whp. So, that in itself should show you the importance of piston shape in the m20. The 2.7i (885 head on flat pistons) and budget stroker both displace the same, but the 2.7i will have about 8.3:1 compression, the budget stroker is closer to 9.3:1. By using the proper shaped pistons, that 1:1 compression bump gives you ~40whp more.

ForcedFirebird I am considering doing this. If I can source some pistons, is it as simple as asking the machine shop to take 2mm off the block? Anything else I would need to do?

[jc1000]

I'd add that the art is to make it streetable, waking up early but not fading out too early. Turbo selection is crucial here.

I see forums full of turbo shit that spools up @5000, puts out nice power but must hit limiter somewhere @6500. That kind of car is slower in traffic light races than average diesel cab. Lots of noise and wheelspin, but not much performance.

Thanks hasa. I am new to the turbo scene. Is there a "tried and true" option I can go with for the M20 setup? One that most agree is a solid choice?

[jc1000]

No, my suggestion isn't the "easiest", but it's not far.

In my experience, you will see anywhere from mid 250's to about 500whp depending on the turbo you select. A 58-60mm turbo will get you 300whp at 13psi, on a normal b25, personally done several of those (Turbonetics Super 60, or Garrett t04e etc). A 6266 at 19-ish psi will net you about 500whp (did one for a local, he made 518 @ 19psi). An HX35 at 15psi will get you about 340whp. Granted, these will all be VERY different spool rates. The 6266 won't see full boost until about 5000rpm, whereas a 56mm will be closer to 3500rpm.

If you want an idea of what yours will make, browse these forum builds. A lot of them are using flat pistons, and you will also get a feel for the turbo you would like.

Thanks, ForcedFirebird. Can you clarify what your suggestion would be? To use the B25 pistons if possible, right? What is the most straightforward way to do that with the ETA block? Maybe shaving the block is part of that suggestion, but I don't understand how.

[hasa]

I'd add that the art is to make it streetable, waking up early but not fading out too early. Turbo selection is crucial here.

I see forums full of turbo shit that spools up @5000, puts out nice power but must hit limiter somewhere @6500. That kind of car is slower in traffic light races than average diesel cab. Lots of noise and wheelspin, but not much performance.

[ForcedFirebird]

No, my suggestion isn't the "easiest", but it's not far.

In my experience, you will see anywhere from mid 250's to about 500whp depending on the turbo you select. A 58-60mm turbo will get you 300whp at 13psi, on a normal b25, personally done several of those (Turbonetics Super 60, or Garrett t04e etc). A 6266 at 19-ish psi will net you about 500whp (did one for a local, he made 518 @ 19psi). An HX35 at 15psi will get you about 340whp. Granted, these will all be VERY different spool rates. The 6266 won't see full boost until about 5000rpm, whereas a 56mm will be closer to 3500rpm.

If you want an idea of what yours will make, browse these forum builds. A lot of them are using flat pistons, and you will also get a feel for the turbo you would like.

[digger]

NA is 140-150whp so rough rule of thumb is 1bar boost will be 280-300whp and so on depends on turbo and what part of efficiency map you run etc. others will be able to recommend it’s not my thing

I might be wrong but DBO YouTube channel may have done a “stroker” turbo might have been slight different and based on SETA

[jc1000]

I second the keep it simple. Put the m20b25 head, topend gubbins and induction and boost it. Let sleeping dogs in the bottom end lie provided the comp test and leak down don’t show its munted. The 40whp gain FF refers to is along way from an apples to apples comparison. If this was a NA engine it would be a totally different approach.
also if building a stroker bottom end for boost a 2.7 with factory rods and slugs is not the best choice and savings are not enough to justify these budget items IMO

Thanks digger, this is very helpful. So if I am going to boost, you think I should just leave the 2.7 bottom end as is and add on the i top. Any idea on a ballpark HP going this route?

Still want to hear any and all opinions as I make these decisions. I am still new to all of this. Thanks.

[digger]

I second the keep it simple. Put the m20b25 head, topend gubbins and induction and boost it. Let sleeping dogs in the bottom end lie provided the comp test and leak down don’t show its munted. The 40whp gain FF refers to is along way from an apples to apples comparison. If this was a NA engine it would be a totally different approach.
also if building a stroker bottom end for boost a 2.7 with factory rods and slugs is not the best choice and savings are not enough to justify these budget items IMO

[jc1000]

I’m currently using the eta pistons with 885 head. I live at high altitude so the deficiencies are more noticeable, especially with turbo. So I’m going to build a not-budget stroker, lol. And I wish I had used the “i” pistons from the start.

That said, I 100% agree with hasa in this case, and although I want a different setup now, that’s exactly why I went with that in the first place. I had to draw the line in project budget and scope to focus on other aspects, like engine management.

mikey.antonakakis If I am able to source some i pistons, what would be the most straightfoward setup for using them? You mention you wished you had used the i pistons from the start. I am also at altitude, and don't want to go through all the effort to build an engine just to find it falling short.

[mikey.antonakakis]

I’m currently using the eta pistons with 885 head. I live at high altitude so the deficiencies are more noticeable, especially with turbo. So I’m going to build a not-budget stroker, lol. And I wish I had used the “i” pistons from the start.

That said, I 100% agree with hasa in this case, and although I want a different setup now, that’s exactly why I went with that in the first place. I had to draw the line in project budget and scope to focus on other aspects, like engine management.

[hasa]

When considering that this is his first build, I'd minimise all risks and start from easy configuration.

99% of the success is made by selecting right turbo for the configuration, low boost, adequate fueling components (injectors & pump) and tune engine properly with good quality aftermarket ecu.

All the buzz about squish areas, piston shapes, piston brands, rod ratios etc is much less important and can developed later when you learn by doing. Otherwise you'll try way too complex setup and get lost in the details.

[jc1000]

If you are starting with an eta car, adding the 885 is an upgrade. If you are starting with a b25, then it's best to keep it like that. Only in 1988 SETA, the 325e uses the same dome shape as the b25 pistons (that fit the 885 head properly), except with 8.5:1 static compression (b25 is 8.8:1). Don't get confused between the two.

I have posted many dyno plots in the m20 dyno thread. When putting an 885 head on a eta bottom end, you get around 135-140whp. A healthy b25 makes 155, rebuilds are 160-ish.

By using the b25 pistons, eta rods/crank and shaving the block 2mm puts you around 180whp. So, that in itself should show you the importance of piston shape in the m20. The 2.7i (885 head on flat pistons) and budget stroker both displace the same, but the 2.7i will have about 8.3:1 compression, the budget stroker is closer to 9.3:1. By using the proper shaped pistons, that 1:1 compression bump gives you ~40whp more.

Can you clarify the budget stroker for me? Why shave the block 2mm? We are talking about the ETA block, right? I thought the B25 pistons on the ETA rods/crank already stick out too much? Sorry, I realize these are newbie questions.

[ForcedFirebird]

If you are starting with an eta car, adding the 885 is an upgrade. If you are starting with a b25, then it's best to keep it like that. Only in 1988 SETA, the 325e uses the same dome shape as the b25 pistons (that fit the 885 head properly), except with 8.5:1 static compression (b25 is 8.8:1). Don't get confused between the two.

I have posted many dyno plots in the m20 dyno thread. When putting an 885 head on a eta bottom end, you get around 135-140whp. A healthy b25 makes 155, rebuilds are 160-ish.

By using the b25 pistons, eta rods/crank and shaving the block 2mm puts you around 180whp. So, that in itself should show you the importance of piston shape in the m20. The 2.7i (885 head on flat pistons) and budget stroker both displace the same, but the 2.7i will have about 8.3:1 compression, the budget stroker is closer to 9.3:1. By using the proper shaped pistons, that 1:1 compression bump gives you ~40whp more.

[digger]

An eta with 1b is still only like 240hp lol