Turbo M20 2.8L Stroker w/ 135mm rods

[SLEEPYDUB]

9.5:1 is not sweat, specially when you are using e85. The stock m20b25 is 8.8:1 and we saw 500+ at only 19psi - and it is the same turbo as yours, but ball bearing and t4 turbine (believe you said t3 for yours)?

Correct, T3. I have a T4 housing I can use, but was under the assumption that it would be too large for an M20, maybe I should try it out.

Im still stuck on deciding between gapless and conventional top ring. I've read that gapless has some drawbacks, and this will be a street car so I'd like to have some longevity out of it. Mayb I should just stick to total seal conventional rings. When I call Top End Performance today Ill see what they say, although I'm sure theyll try to sell me on them...

[SLEEPYDUB]

I've Emailed Top End Performance, I will await their reply

[SLEEPYDUB]

Also, i've read up on 2618 vs 4032. This is a long discussion.

Digger mentioned to stick with 4032, probably because I mentioned this will be a street car. This car will be drifted though, and will see rev limiter at 6500rpm daily. Now, on the limiter it will only see 15-20psi. It will not see limiter much when running higher then that.

My question about this is obviously which one suits my needs better?
2618 is stronger, but i dont like the chatter when cold, and my last set of 2618s ended up piston slapping to the point of ruining the engine, although that could have been my, at the time, my engine builders problem. I do intend to drive this car a few times a week, and on weekends to have fun. It will probably see 3 or 4 drift events a year where it will get completely thrashed on.

[digger]

Turbo engine better to get 2618 unless it's ultra conservative tune and mild boost. Also make sure you specify total seal convential otherwise you get Je

2618 from Je won't need as much clearance as some others plus if you got 4032 you open up clearances anyway compared to NA

[SLEEPYDUB]

Turbo engine better to get 2618 unless it's ultra conservative tune and mild boost. Also make sure you specify total seal convential otherwise you get Je

2618 from Je won't need as much clearance as some others plus if you got 4032 you open up clearances anyway compared to NA

Im just more concerned with the longevity of the engine, and the cold start blowby/noise in the engine. The 2618 seems like its not designed for a street car am I right?

[digger]

Im just more concerned with the longevity of the engine, and the cold start blowby/noise in the engine. The 2618 seems like its not designed for a street car am I right?

most OEM dont use 2618 forged but there would be some engines out there from the factory but they do much more R&D for the specific application than your average aftermarket supplier who's R&D comes from the customer ....alot of engines still on cast pistons taking a fair bit of boost but living closer to the edge so forged 4032 is a step up. also there are some ring groove treatments to help wear so its possible OEM are using those to make 2618 give them the longegevity

topend will recommend you 2618 no question. i have no doubt 4032 would work if the tune is good since you are using good fuel so if there is no knock then no issues.

i know it doesn't answer your question, nobody can tell you in uncertain terms as it comes down to the execution of it all

[SLEEPYDUB]

Steve Emailed me, here is what we have come up with for my setup, what do you guys think?

Base Piston Set:
Turbo Dish Style
85mm x 84mm x 8.8:1
$995
Options: Per Set, not per Piston.
$90 HD Pins
$138 Skirt Coat
$36 Contact Reduction
$228 Total-Seal Gapless Tops

I will be pulling the trigger by next week, had an emergency vet visit for my dog, took a chunk out of me.

[ForcedFirebird]

I am not sold on the gapless top ring for boosted 885-style m20 builds. As I mentioned earlier, I have not seen any data on gas porting, which should be done for gapless rings.

If anything, you will want a slight bit excessive ring gaps - if you go gapless there's no where for the extra trapped mass to go. They are actually a two-top-ring system that completely seals above it. If you read that link I posted about rings, you will see that it is imperative for the gasses to flow around the top ring, so it will exert force that pushed the ring out to the bore to promote sealing. There has been plenty of data using flat and dish-top pistons with gapless top rings and appropriate gas porting of the pistons.

[digger]

For an extra 230 hard to justify when there is no overall consenus.

What is turbo dish style ?

[SLEEPYDUB]

Steve said that he uses gapless top rings on every turbo M20 he has ever built and has had good success with it. I mentioned to him that Ill be running 30+psi and he said to use the dished pistons vs oem crown due to the way it combust under high boost?? Said OEM crown is good for lower hp levels, but when getting into the big power territory he suggest to go with dished style. I dont think he mentioned anything about gas porting with the gapless rings.

At this point, my mind is not made up on what I should order.
Based off of our conversations in this thread, and my conversation with him, I cannot come to a conclusion as to what I truly need. So, would you guys mind giving me some questions to ask him so that we can figure this out? He responds very quickly and has been easy to work with, i'm sure he wouldnt mind clearing some things up for me.

Thanks again guys

[ForcedFirebird]

Without a doubt match the piston shape to the head. If using 885 head and flat pistons, you eliminate the squish band. I have worked with flat pistons and 885 heads, but they always make less power and require more timing.

[SkiFree]

nobody can tell you in uncertain terms as it comes down to the execution of it all

At this point, my mind is not made up on what I should order.

Digger has a good point, there is no perfect solution for what you are after. You are going to start chasing your own tail. I say this with all due respect, have seen it happen often.

One point to add, not sure if it's been mentioned. Rather than focus on the side skirt coatings, consider ceramic coating the top. If you are looking to maximize longevity on a FI engine, while still having to run 2618, then it's a very nice touch.

[SLEEPYDUB]

Without a doubt match the piston shape to the head. If using 885 head and flat pistons, you eliminate the squish band. I have worked with flat pistons and 885 heads, but they always make less power and require more timing.

Even with the high amount of boost that will be thrown at it?

[SLEEPYDUB]

Digger has a good point, there is no perfect solution for what you are after. You are going to start chasing your own tail. I say this with all due respect, have seen it happen often.

One point to add, not sure if it's been mentioned. Rather than focus on the side skirt coatings, consider ceramic coating the top. If you are looking to maximize longevity on a FI engine, while still having to run 2618, then it's a very nice touch.

Steve mentioned the top coating not being a big deal because I will be running strictly E85, and the cooling benefits from that fuel negate the help from the coatings. But, I may as well just throw that on there too at this point.

I can understand that there is no perfect solution, but I just cant understand why one professional says to use the OEM crown, and one says to use the dished style. I dont know enough myself about the dynamics of it to make a decision, so this is really messing with me

[digger]

some of the guys in that thread work for a piston manufacturer

http://speedtalk.com/forum/viewtopic.php?f=1&t=50883