Most Powerful N/A M20's

[digger]

Really interesting topic this guys, so we are saying that most of the power is to be found through a really good flowing head - not just valves but valve throat etc.

I'd also be keen to see any build sheets or documentation of the guys who are targeting the big power, do we think a roller cam is a definite for anything over say 300bhp?

Bottom end wise, do you think H-Beam rods, over 3.0 on the bottom are important for the big power, or the key is all in the head work, i guess its like all things, how far do you go!

Also think its mostly fair to compare power at the crank like we do here in europe as it removes some variables, Im not saying any two dynos will read exactly the same, but anything with decent calibration you think shouldn't be too far off at these power levels.

that engine above on 'Grootys' youtube channel looks like a trick bit of kit, knife edge crank, polished block etc, I'd be interested to see how far hes taken the head if hes chasing every horsepower with stuff like polishing the block!

Yeah it’s pointless using bigger valves without machining the throat to suit and also blending to the bowl and reprofiling the short side etc

you don’t need a roller rocker setup as the highest hp numbers were without one. You will likely end up needing slightly more duration though.

build sheets were on e30tech forum which died. There is Grooty’s YT channel. My build has some head stuff iirc but I’m not using a big camshaft but should easily do 300bhp but not 300whp

knightengines built the big ho e85 2.8 discussed here but only some snippets

https://www.speed-talk.com/forum/viewtopic.php?t=31132&sid=6093a3ea87a73288a26108ec758c7597&start=15

comparing power at the crank is a variable itself as every dyno does it differently and deducing it in some respects flawed as the drivetrain inertias are not known and the losses are not measured under load they are done under coastdown

[AntParker]

Really interesting topic this guys, so we are saying that most of the power is to be found through a really good flowing head - not just valves but valve throat etc.

I'd also be keen to see any build sheets or documentation of the guys who are targeting the big power, do we think a roller cam is a definite for anything over say 300bhp?

Bottom end wise, do you think H-Beam rods, over 3.0 on the bottom are important for the big power, or the key is all in the head work, i guess its like all things, how far do you go!

Also think its mostly fair to compare power at the crank like we do here in europe as it removes some variables, Im not saying any two dynos will read exactly the same, but anything with decent calibration you think shouldn't be too far off at these power levels.

that engine above on 'Grootys' youtube channel looks like a trick bit of kit, knife edge crank, polished block etc, I'd be interested to see how far hes taken the head if hes chasing every horsepower with stuff like polishing the block!

[digger]

I don't get how hub dyno adds any unknown to the measurement process. To my understanding it only removes the biggest bunch of uncertainity = tire (tyre deflection, compounds, pressure, temps, slippage).

But that was not the topic. I'd love to see any detailed documentation about how those +300whp engines are done. I can understand that major rework allowing 44-45mm intake valves is the key.

It adds unknowns when comparing against roller dyno that provide whp readings and roller dyno that measure whp and do a coastdown correction to bhp like done in most of Europe. You would think that they would read more power from less tyre losses but I’ve see where this isn’t the case due to brand A vs brand B doing the calculations differently so while it should be more repeatable it costs more to get it setup so not economical for quick power runs, better for tuning of high hp engines

yes the cylinder head normally have at least 44mm valve if not bigger and the most cross section area in critical area that can be achieved before ruining the casting by cutting into water or the spring seat. They usually end up flowing 210-220cfm at 0.500” lift or so . The port opening doesn’t change much as that’s not the restriction but the valve throat, bowl, SSR and roof near the guide change a lot. Unfortunately there are not many porters who know what they are doing to get both the shape and size right

[hasa]

I don't get how hub dyno adds any unknown to the measurement process. To my understanding it only removes the biggest bunch of uncertainity = tire (tyre deflection, compounds, pressure, temps, slippage).

But that was not the topic. I'd love to see any detailed documentation about how those +300whp engines are done. I can understand that major rework allowing 44-45mm intake valves is the key.

[digger]

In the advent of hub dynos, I don't see the whp/bhp as issue. If we think pure engineering theory, 120hp/litre (real engine power, no wheelhp, no parasitic-loss-translated) should be doable for 2v engine that is built on best components and head is reworked to support that. 100hp/litre should be no brainer for anyone capable to just plumb pieces together, maybe some touchup is required for head (like mine 288bhp/2820cc).

Max reasonable engine displacement for M20 is perhaps 3.0 litre?

Hub dynos just add another unkown variable and are a waste of time on a NA m20 as there are no traction issues on the roller therefore the extra labour cost is a mostly a waste IMO

Theory says the inlet valve flow dictates the power capability, therefore the limit is irrespective of the engine cubic capacity and the capacity just dictates the rpm where the peak is made. to make the most hp/L you just make the displacement smaller and rev it up high

The issue is an unless you have access to a good head porter you're going to top out at somewhere around 260-270bhp and why you see 230whp rarely exceeded as most have little more than a stock head.

If you take one of these big hp m20 290-350rwhp and inbetween and run with a streetable cam which would be 29x duration with itb youre still going to make really good power because the head work is where it is at more so than the cam

[hasa]

In the advent of hub dynos, I don't see the whp/bhp as issue. If we think pure engineering theory, 120hp/litre (real engine power, no wheelhp, no parasitic-loss-translated) should be doable for 2v engine that is built on best components and head is reworked to support that. 100hp/litre should be no brainer for anyone capable to just plumb pieces together, maybe some touchup is required for head (like mine 288bhp/2820cc).

Max reasonable engine displacement for M20 is perhaps 3.0 litre?

[digger]

I know, it varies, but that's going to translate to what? Maybe 270-280whp? I'm sure the number of M20 builds that have been on engine dynos for an honest bhp figure is much smaller than those which have been on chassis dynos. Honestly, I haven't even seen any documented NA builds that make even 270whp... Even when I was looking and considering building a high compression NA M20 for my E30 this year or next.

300bhp is probably 350rwhp depending on dyno in question.

Are you referring to a streetable m20 engine or m20 in general? For radical valve train I’m referring to cam duration. The roller cams are more for durability than peak power though there is likely an area under the curve advantage

[varg]

300bhp is easily doable it’s just the head work is expensive but can be done streetable. Can be done with not so radical valve train to.

I know, it varies, but that's going to translate to what? Maybe 270-280whp? I'm sure the number of M20 builds that have been on engine dynos for an honest bhp figure is much smaller than those which have been on chassis dynos. Honestly, I haven't even seen any documented NA builds that make even 270whp... Even when I was looking and considering building a high compression NA M20 for my E30 this year or next.

[digger]

I'm sure this is a conversation which has been had here many times before but probably not recently,

Question is who/ what is the 'most powerful' N/A M20 - Appreciate this is massively subjective due to different Dynos, Setups etc.

What's the most extreme built M20 that is currently in existence, does anyone know, are there many/ any which have broken that 300bhp barrier.

Interested to hear your thoughts or details of those extreme, i'd guess always stroker builds.

Just as a topic of conversation, but what do we think would be needed to break that 300bhp mark, is it even possible with a 12V Head?

Yes i know its much cheaper/ easier to swap in a later engine, but that's not the point!

300bhp is easily doable it’s just the head work is expensive but can be done streetable. Can be done with not so radical valve train to.

300whp which is the unit of measure most rely on as bhp is a bit bogus has been done a couple of times but not going to be what most would call streetable and fairly radical valve train

[MrBurgundy]

That's wild power, jeez.

[AWDBOB]

This topic has kinda been beaten to death. Tons of high end head work, ITBs, roller cam, etc

A good YT channel to follow for M20 goodness is:

https://www.youtube.com/@Grooty79

The most famously quoted "highest HP" N/A M20 is this car:

https://www.youtube.com/watch?v=sAHlvU6VSy0

[AntParker]

I'm sure this is a conversation which has been had here many times before but probably not recently,

Question is who/ what is the 'most powerful' N/A M20 - Appreciate this is massively subjective due to different Dynos, Setups etc.

What's the most extreme built M20 that is currently in existence, does anyone know, are there many/ any which have broken that 300bhp barrier.

Interested to hear your thoughts or details of those extreme, i'd guess always stroker builds.

Just as a topic of conversation, but what do we think would be needed to break that 300bhp mark, is it even possible with a 12V Head?

Yes i know its much cheaper/ easier to swap in a later engine, but that's not the point!