Turbo M20 2.8L Stroker w/ 135mm rods

[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.

[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.

[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]

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]

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]

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.

[SLEEPYDUB]

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

[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...

[ForcedFirebird]

psig is just a bragging number. A lot of people ignore pressure ratios. It takes very little effort to plumb a pressure reference port in your exhaust. If you have a 1.5:1 or more ext:int ratio, the system is inefficient, 2:1 it's defunct.

[digger]

Well if you would have read early, you would see that I mentioned this car will be strictly rsn on Ethanol only, as it is available at the pump here. I would like to stick with 9:1, though I dont think 9:5:1 would cause any problems.

As for boost limits, I'd like to know that as well, the stock engines have already seen 30psi and the car was a rocket, so I'd like to run 30-35psi on a 6266 when I need it. I am debating Oringing the block OR sticking with OE gasket and ARPs, just in case we have a problem with detonating during tuning. MLS has been brought up, which is an option. Power goal is ~600whp

there is a cutring option

[apostate]

I am enjoying all of yours. But there are special ones that I made a collection of.

[ForcedFirebird]

I am actually starting to enjoy Prostate's posts. Some entertainment between all these numbers and letter.

[ForcedFirebird]

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)?

[apostate]

Well if you would have read early, you would see that I mentioned this car will be strictly rsn on Ethanol only, as it is available at the pump here. I would like to stick with 9:1, though I dont think 9:5:1 would cause any problems.

As for boost limits, I'd like to know that as well, the stock engines have already seen 30psi and the car was a rocket, so I'd like to run 30-35psi on a 6266 when I need it. I am debating Oringing the block OR sticking with OE gasket and ARPs, just in case we have a problem with detonating during tuning. MLS has been brought up, which is an option. Power goal is ~600whp

Well, that's a quite of boost.
You may want to rethink the CR or face detonation issues.
If I were you, I would use 8.5-9:1 CR maximum even with Ethanol.

[apostate]

Euro engines are 9.4-9.7 preface and 8.8 facelift.
They use totally different engine management.
8.8 CR are commonly turboed in Europe but the preferred CR is around 8:1. on 100 octane fuel and 1.5-6 bar boost.