Worth Modifying?

[DrunkPanda]

So, I purchased an E30 a little while back. M20B25 engine.

The previous owner had a decent rebuild done on it.
Honed the block, New Ex valves, New rings, bearings, head gasket and seals,
Machined crank, New thermostat and plugs..

I would prefer not to build a stroker, just because then a lot of that previous work would be a waste.

According to several people and BMW workshops, the car does pull a fair bit harder than a standard M20B25. Pretty sure it has some sort of chip, but I haven't had a chance to pull out the ECU to check. Also has catback exhaust, but standard headers.
It may have a cam.. when the workshop did the rebuild they didn't measure the cam or do anything too it, and the previous owner has passed away.. so without pretty much pulling it out, i cant check the cam profile.

First step will be a set of headers.
I like the idea of ITBs, and i'd like to have a bit more response, specially down low, and a bit more power.. but ITBs are not exactly cheap, and if i did that i'd probably need a megasquirt or similar to make it worth it.

I guess i'm just trying to see if it is worth spending money on to make it a bit more fun or just leave it as a cruiser with a fresh engine.

No turboz :)

[roguetoaster]

Sounds like it would be better to leave it and build another engine to drop in. That way you have better control over the results amd aren't replicating or wasting work done before.

[zwill23]

I say take it in steps, enjoy it as is until you have the headers installed. If you keep itching for another healthy bump in power go for the ITB's as you will have paved the way for them with a decent set of headers.

ITB's typically net you about 30whp on a stockish M20, NA that's nothing to sneeze at but know that's going to be your power limit without tearing the M20 apart. ITB's will give you that sweet throttle response you're looking for and will sound bitchin' to boot. The other nice thing is that ITB's are easily reversible so you can get it back to stock if you decide to sell the car. A set of ITBs and a megasquirt would sell quickly on here too.

For a proper ITB setup you're realistically looking at $3k or so for the RHD ITBs, Megasquirt, and a tune.

[digger]

wont gain much in the way of bottom end without stroking it with higher compression etc.

if you want more top end then standalone and ITB will help.

[varg]

^Pretty much. If you want low end punch, bigger displacement, more compression, better breathing. However, cam, ITBs, header, tune, can make a significant difference and is worth a try though yes it is significantly expensive. Gearing makes a big difference too, 4.10LSD if you don't already have it.

Consider an M54B30 or S52 swap if you're not into building a stroker.

[DrunkPanda]

Thanks guys.. Yeah i already have a 4.10 LSD which helps a bit.. Not really into the idea of engine swaps considering my current engine is in such good condition. Maybe ill just get ITBs and drive around at 5-6000rpm all the time Sent from my SM-G935F using Tapatalk

[zaq123]

Thanks guys.. Yeah i already have a 4.10 LSD which helps a bit.. Not really into the idea of engine swaps considering my current engine is in such good condition. Maybe ill just get ITBs and drive around at 5-6000rpm all the time Sent from my SM-G935F using Tapatalk

you will need stand alone for ITBs and tuning, ITBs are no go with stock ECU.

build new engine on the side and swap is a solid advice. if you are planning to keep the car long-term, spare engine is a good thing to have. old engine is $400-500 and to pull/install it is nothing major, compared to the actual rebuilt/tuning/ITBs etc etc....pricewise and workwise.

If you are set on ITBs, get yourself a standalone first, install it and get familiar with how to tune it.....unless you will have a shop to do all the work...

[stanhayward]

you will need stand alone for ITBs and tuning, ITBs are no go with stock ECU.

build new engine on the side and swap is a solid advice. if you are planning to keep the car long-term, spare engine is a good thing to have. old engine is $400-500 and to pull/install it is nothing major, compared to the actual rebuilt/tuning/ITBs etc etc....pricewise and workwise.

If you are set on ITBs, get yourself a standalone first, install it and get familiar with how to tune it.....unless you will have a shop to do all the work...

Not necessarily true, but definitely optimal yes. Dbilas Dynamic in Germany makes (IMO) the prettiest ITB setup for M20s. They aren't cheap (~2000eu), but the OEM+ style of them really gets me. They have a plenum with a single inlet boot to attach to a stock AFM, and for an extra 300eu they offer a chip for the stock ECU to make a claimed 20hp. They also sell cams for M20s and chips for those, so I imagine it might be possible to get a chip capable of both? You could obviously go to a standalone further down the line and delete the AFM too.

ITBs:

https://dbilas-shop.com/en/intake-tract/throttle-body-kit/street-version/bmw/m20/3931/throttle-body-kit-for-bmw-e30/e34-2-0-2-7-12v-m20?c=11055

With MAF conversion:


With AFM:

[digger]

Not necessarily true, but definitely optimal yes. Dbilas Dynamic in Germany makes (IMO) the prettiest ITB setup for M20s. They aren't cheap (~2000eu), but the OEM+ style of them really gets me. They have a plenum with a single inlet boot to attach to a stock AFM, and for an extra 300eu they offer a chip for the stock ECU to make a claimed 20hp. They also sell cams for M20s and chips for those, so I imagine it might be possible to get a chip capable of both? You could obviously go to a standalone further down the line and delete the AFM too.

ITBs:
https://dbilas-shop.com/en/intake-tr...2v-m20?c=11055

With MAF conversion:


With AFM:

yeah have a mate that runs MAF with Miller WAR in conjunction with the RHD itbs seems to work ok. Can be done but there are several standalone plug and play options so it doesn't make much sense with anything else.

the dbilas ITB kit looks nice but performs horribly

[DrunkPanda]

That Dbilas ITB kit does look pretty :) :)

What is the pros/cons of running open trumpets vs plenum?
I guess, open trumpets don't really have any filters on them so more chance of shit in the engine, although I have see air filters for trumpets.
Plenum i am assuming is easier to control/measure air flow?
What else.. what am i missing..

[digger]

The plenum helps feed cooler air to the engine if ducted correctly where results in a higher charge density and more power.

Open trumpet does not get filtered nor does it provide the most reliable cool air which is a unsatisfactory approach in my mind when viewed with my first comment.

The filtration is easier to achieve as one large filter easily filters an entire engine as 2 cylinders are drawing air at any given time. Where as a single small filter per cylinder needs to be half the size of the large common filter to meet the peak demand of a single cylinder. that's part of why socks cost a fair bit of power.

Filters that attach to the trumpet can have a nasty habit of destroying the pressure waves and hurting VE as they intrude into the mouth area

depending on the volume this can create some constructive interference which helps cylinder fill at certain rpm but hurts at others. on an inline 6 this does nott seem to be that significant as there are too many cylinders connected to a single plenum. sometimes you see two plenums on some setups so only 3 are connected and essentially fully separated by 240* rather than 120* but i wouldn't bother with added complexity.

[stanhayward]

yeah have a mate that runs MAF with Miller WAR in conjunction with the RHD itbs seems to work ok. Can be done but there are several standalone plug and play options so it doesn't make much sense with anything else.

the dbilas ITB kit looks nice but performs horribly

Definitely not for chasing optimum performance... But if that's not the idea here (a stock compression M20 is hardly 'optimum performance'), maybe it's a cool compromise to gain a little sumthn sumthn. Not my money or my project though, all personal opinion. When it comes to experience and facts for N/A M20s, that's your domain Digger !

[digger]

Definitely not for chasing optimum performance... But if that's not the idea here (a stock compression M20 is hardly 'optimum performance'), maybe it's a cool compromise to gain a little sumthn sumthn. Not my money or my project though, all personal opinion. When it comes to experience and facts for N/A M20s, that's your domain Digger !

i look at like its a stock compression b25, so you need all the help you can and optimum air going into the engine is priority 101.