[SPLIC3D]

I'm beginning the final step towards completing my built motor, and now i am reaching the point where i need to decide on semi closed vs leaving the deck open. Ive got a Shuenk turbo, IPOS E85 kit, Forged pistons and rods, revised timing guide and some upgraded head studs. I am having trouble justifying sending my motor out for 2 months to get semi closed and also am worried about doing the drilling myself if i chose to do so. How much power could i reasonably push on the open deck motor alone? im aiming for ~350-400hp

[MaverickCruise]

I completed a closed deck N20 2 years ago and then a wet liner N20
I think the closed deck is good. I have processed at least 20 N20s like this, and the longest one has been running perfectly for more than 40,000 kilometers.

[SPLIC3D]

How much does custom work like this cost? And how much power could this handle compared to an open deck motor?

[MaverickCruise]

Originally Posted by SPLIC3D

How much does custom work like this cost? And how much power could this handle compared to an open deck motor?

close deck cost 1000USD

TTE400 turbo runing 30psi peak when 4000-5000rpm ,then 25psi to redline
If using a larger AR turbo,like G25 660, it can run at 35psi to redline

[sqwinny]

For all the off the shelf hybrid turbos in the market as of today, 4.25.24 you don’t need to close the deck. The turbos won’t generate enough power/boost to make it a need.

If you go custom and a drastically larger turbo which will require over 30psi and make over 400whp +/- it’s a different discussion.

You can technically buy and have your local machine shop install these, but flanged sleeves with install will cost around the same as sending your block out to close the deck with sleeves via CSS

OR

Send your block out to La sleeve with the pistons and having them make their custom sleeve solution. I went this route.

Navardi tuned sells a block which has Darton sleeves installed with a set of pistons. The 10mm head studs are also converted to 11mm for you as well.

Links For reference in order mentioned. Ultimate would be Darton sleeve solution:

Vac flanged sleeeves.
https://store.vacmotorsports.com/vac...n20-p5852.aspx

CSS
https://cylindersupportsystem.com/

La sleeve
Lasleeve.com

Navardi tuned block + Darton wet sleeves installed + pistons + head stud conversion

https://navardituned.com/en-us/produ...ine-block-only

[SPLIC3D]

so im looking to hover around the 360-375 hp area for now, would it be safe to say with the Shuenk i can keep the deck open and still be safe? the plan in the long run is to have CSS and also a custom big turbo setup. I just want this thing running again in all honesty lol

[sqwinny]

You can max out the shuenk turbo on the stock motor with all seriousness. Down the road just grab a spare block that is in good condition and have that sleeved + all the work done to it and swap over to it when you get to that point.

[SPLIC3D]

Oh sweet! I'm not looking for crazy numbers right now, I just want a reliable and fun daily that can keep up with my friends and their N55s. Is 400hp the limit where you see most N20s fail in the combustion chamber? And what's a reasonable horsepower to aim for with some forged internals and a bigger turbo?

[sqwinny]

The issue isn't horsepower so to speak, its that you need a decently sized turbo to make over 400whp. In order to spin that turbo and not feel as if you have no power until 3600 rpm or so, you need boost. Boost is technically a restriction on the exhaust side to make the turbo spin fast enough to get enough air compressed to make horsepower. when you actually start to tune your car with your sheunk turbo, you will miss the low end torque as the shuenk is single scroll however allows for more flow in the higher RPMs as its not twin scroll and takes a bit longer to spool (maybe 200-400rpm) in comparison vs stock or the TTE400.

Make sure you go turbo smart Compact vr9 upgrade and not the GFB as you'll have boost leaks. Save yourself the trouble and do it while the turbo is off the car.

rule of thumb is an ewg n555 can flow 600whp or so without issue, anything above that you should be looking into upgrading internals. n20 uses the same components, thus 400whp or so is the rule of thumb. if the rods and pistons are upgraded, you can make more power as you have stronger parts + bigger safety net, however the OEM open deck design is the next limitation due to cylinder walls showing they are distorted at around 31-33psi.

Some food for thought, the n55 stock turbo maxes out around 20 psi or so. in order for the n20 to have the same airflow, you need 31-33psi pushed through that turbo to have the same airflow and make the same power in the n55.

Engine size matters to generate exhaust gases to flow that turbo.

if you haven't looked, there is a lot of into in the bmwenginewiki.com and also on the "n20, n26 and b46, b46 car club" group on FB.

This was stock motor and the car is fine even today. I blew the turbo 3 years later on my own accord. 100% stock motor, stock internals. Hope this helps.

[SPLIC3D]

Oh wow i never knew all that, thank you! I feel a lot better now doing my build knowing the engine will remain on the safer size. Eventually I’ll go to a 2.5L, closed deck and go Max Effort. I really appreciate your insight on this matter. One final question, what turbo do you recommend? I know Shuenk, MHI, TTE400 and Pure are options. I’m looking for one that will give a bump in power but not break the bank entirely for now? Is this where Shuenk comes because of the 500 dollar tune rebate or is it better to look into a different turbo? The TTE400 is my end goal but i could grab it now if it shows to be the best option.

[sqwinny]

Honestly if you have the turbo already keep it. its not worth swapping for the price difference.

Shuenk turbo is around 360whp or so, tte400 has been repeated to 370-375whp or so. I was able to reach over 380whp due to installing bimmermilvs.

www.bimmermilvs.com
-email marty and ask for a set of 4 only.

Some side notes, both the TTE400 and the Shuenk have turbo internals which can technically on paper make 400whp. the issue is the various changes which limit this happening.

TTE400 has a turbo ar ratio of .41. thus is limited to around 36-37 lb min air flow as that’s how much exhaust air can flow 100% out the turbo. Anything more than 100% is a bottle neck and only creates backpressure and heat.


The Shuenk has a turbo ratio of around .44 or so (not confirmed). however due to the turbine wheel combo is limited to around 35-36 lb/min or so for air flow. But the ar ratio on paper allows for more air flow outside the exhaust side of the turbo.

The best of the best hybrid turbo at this moment would be to take the shuenk turbo manfold (single scroll with larger ar ratio exhaust housing to flow more exhaust air) and put the tte400 inside it(will need machining) thus allowing for a bit more air flow can get closer to a 38-40 lb/min turbo which would net you at nearly 400whp. cost to do so isn't really worth it however.

Either way you'll beat up your stock turbo f30 n55 friends and they will be upset losing to the "crappy n20/n26 motor" and try to throw you under the bus.

good luck.

[SPLIC3D]

Thanks a lot for your help! Definitely helped clear up a lot of questions I had. Hopefully I’ll be coming back next with some dyno sheets and 1/4 mile times.