m20 2.5 tuning possibilities?

Fri Apr 13, 2012 2:02 pm

Hi was looking to out a m20 2.5 engine into my convertible, but was wondering what sort of bhp you can tune one to without doing anything too drastic, ie not fitting turbos/superchargers.

I believe they are 170 bhp standard when they left the factory, what sort of bhp would you get with a straight through exhaust, aftermarket highlift camshaft and induction kit.

If I put a 2.7 head with cam on would this make any difference?

cheers

Fri Apr 13, 2012 2:52 pm

An m20 325i will be a nice power hike from an m40 for a start. If you get a nice engine running as BMW intended it, this will be a better base for further modifications. Spend your time and money on getting the injectors cleaned, setting the valve clearances, giving the AFM and ICV a once over. Theres no point trying to tune an engine with any problem areas it makes things worse not better.

The 2.7 head? No the only 2.7 heads are 200 castings off the eta engine (eta means economy) you dont want that one, and ones off Alpinas and other such exotica and these are 885 casting same as a 2.5. If it makes any difference to you the later ones are stamped 2.5/2.7, as they where used in over seas engines with that capacity

Put a chip in the ECU, and get a lightened flywheel, bang for buck these are the two best mods IMO, they really transform the charcter of the engine. When you start getting into cams, heads start coming off and things get out of control, that is if you are trying to keep the cost down. Plus a cab is not for diffing around racing french turds, so keep the engine nice and tractable.

That will start you off, but then you'll want more..........

Just my 2p, but as the saying goes "speed is just a question of money, how fast do you want to go?"

Fri Apr 13, 2012 3:32 pm

I must admit I don't know that much about bmw engines I just wanted something to have a bit of fun, but nothing too drastic, I want something I can take up santa pod now to do the quarter miles just for abit of fun and something with enough power to use on the road for overtaking, going up hills etc. anything the upper side of 180 bhp will do, as you say though first I need to fit the 2.5, service it and get it all running ncey before doing this.

Just wanted to get a idea of what could be done without spending a fortune to get a little more power.

How much will chip and flywheel cost 300-500?

What differnce will that make better acceleration/torque and a little more bhp?

You don't have a full 2.5i conversion for sale do you?

I'm not looking to do it for a month or so really though.

Thanks again

Fri Apr 13, 2012 5:41 pm

The m20 is notoriously hard to get big gains out of, not impossible but it does require a little effort. The lightened fly helps the car rev up and down quicker which is good for gear changes heel/toeing ect, the effect can also be felt in the increased acceleration of the lower gears. It has no down sides, you may feel you need to rev the car a little harder to pull off but it is neglegable, any stuff you hear about it loseing torque are bull plop, a rumour started by the video game grand tourismo!

The chip I'm thinking of is a generic one, it would raise the limiter to 7000 (power wise a standard m20 is done by 6000), and optimise the ingnition timing, the chip BMW put in there has to cater for the countrys of the world whos petrol is of crap quality, luckily we dont have that problem (lets face it, it costs enough) and can tune cars to suit our higher octane juice. You will gain a couple of bhp, and the engine will seem much keener.

HTH

Sat Apr 14, 2012 8:29 am

I've got a chip and light steel flywheel on my 325 apart from exhaust it's standard. It's reasonably pokey but once you start you cant bloody stop. Tuning is addictive. Why not go do a power run on a dyno as your motor may only be doing 155-160 if 150k miles old anyway.
A lower cwp diff ratio will liven it up a bit.
By the time you spend x on a chip, few hundred on a steel flywheel plus the engine and exhaust system your prob better off just sticking a standard 328 24v motor in financially. That's my plan next as would love a btb exhaust etc as mine is rather battered from rallying but having an m52 and m50 manifold sitting in corner of garage it's almost silly to spend that kind of money.

Sat Apr 14, 2012 12:40 pm

Just save on pennies and get the car serviced properly then it will be well lively

Sun Apr 15, 2012 12:36 am

Does anyone know if i swap my E30 325 M20B25 ecu to E36 328 ecu?
Wat can i expect from that ?
Should i do it?
Thanks

Sun Apr 15, 2012 12:43 am

Nemiers wrote:Does anyone know if i swap my E30 325 M20B25 ecu to E36 328 ecu?
Wat can i expect from that ?
Should i do it?
Thanks

yea do it, actually why stop an the e36 328i ecu, fit an e36 m3 ecu as they are even more powerful

Sun Apr 15, 2012 11:22 am

Kos wrote:
Nemiers wrote:Does anyone know if i swap my E30 325 M20B25 ecu to E36 328 ecu?
Wat can i expect from that ?
Should i do it?
Thanks
yea do it, actually why stop an the e36 328i ecu, fit an e36 m3 ecu as they are even more powerful

kos you make me laugh

clueless come to mind

Sun Apr 15, 2012 12:18 pm

Here's the spec of my M20B25,

Full service + valve clearances set,

cat cams 274dg cam,

BBTB (big bore throttle body),

mild port,polish & gasflow to the head, also 3 angle valve seats.

speedtouch "wild" chip (generic alpina maps IIRC),

induction kit with cold air feed,

stripped, cleaned & rebuilt injectors,

(genuine) magnex 6 branch exhaust manifold (try finding one lol),

X-pipe just after the down pipes,

full stainless steel exhaust system (scorpion).

power?? Feck knows but it will be going on a local
Dyno soon enough & if that goes ok then it'll be time for a lightweight flywheel, (maybe a MAF conversion) & a proper remapping session.

Mon Apr 16, 2012 6:21 pm

you can do the usual bolt on stuff which will give gains but the key to a great running engine is in the tuning.. or lack thereof in many cases. even an otherwise standard M20 can have a night and day feeling difference in power/torque with a good tune (chip) and asimilar difference if not more can be had when coupled with the usualy bolt ons (good intake setup, exhaust, etc).

there are no shortage of chips out there and of the many i have looked at personally the best (for standard to basic bolt ons BUT with standard cam) seem to be as follows:

Autothority (very good WOT maps but could be improved slightly in one area, best PT maps i have seen by far)
Mark D (very good increase both at WOT and PT maps)
Dinan (very good WOT maps but pulls timing/ramps up fuelling making power drop off well before the limiter, PT sucks and is as standard)
Active Autowerke (good increase both at WOT and PT maps)
Jim Conforti/Turner Motorsport (good increase both at WOT and PT maps)

NOTE:
WOT = wide open throttle
PT = part throttle (ie- off idle up to about 75% throttle/load)

assuming u went for an ebay chip and it was not a dupe of any of the above the ones i have looked at fall anywhere from about on par with Active Autowerke or Jim C/TMS or lower.

toss in a cam and for best results the ECU would need to be tuned in person, handful of people competent/capable but there are one or two out there. i have tuned a fair few as well as my own, nothing cammed yet mind but have done a turbo M20 on 8psi with 30lb volvo/bosch injectors

Nemiers wrote:Does anyone know if i swap my E30 325 M20B25 ecu to E36 328 ecu?
Wat can i expect from that ?
Should i do it?
Thanks

actually not quite as bad/as stupid of an idea as some may think. it would be too much hassle from a setting up/tuning perspective to use an ECU off a vanos engine, also i think 328i and M3 run Siemens ECU's and i have no experience nor do i know if they can be tuned as easily (so to speak) the Bosch units can be. the one to go for would be the M50 non-vanos ECU. you will need the engine loom, MAF, coils, injectors and some other stuff. you will have to modify an M50 TPS sensor to work on the M20 and will have to make up a cam trigger setup and install a cam position sensor and finally it will need to be tuned in the flesh and ideally on a dyno. i do know people have done the swap and reported the engine ran fairly well even on the standard M50B25 maps allbeit not ideal for an M20 ignition/fuelling wise.

gains from an M50 ECU conversion include:

higher resolution maps to tune
a MAF instead of the old flappy door AFM
sequential injection
coil on plug instead of old distributor
and probably a few other benefits

there is a big thread on it at e30tech.com but i cant find it quickly on google/searching the forum as the thread title eludes me but if you want to read more about it or even do the conversion i should be able to dig it up eventually.

EDIT: here we go, may not show to unregistered users tho?
http://www.e30tech.com/forum/showthread.php?t=63504

Tue Apr 17, 2012 8:59 am

just bought an '85 320 with an M20B25 swap... pull rather hard I must say.. most likely going to get a Miller, intake, exhaust and possible lightened flywheel. !!!

Tue Apr 17, 2012 10:40 am

Dmcl, thanks for the "shopping list" I know what I'll be looking for when I'm next at the scrappy.
just got to figure out how to do the engine loom (removal & refitting) as I ain't got a clue about that.

I'll read the thread in that link fully tonight.

Tue Apr 17, 2012 11:34 am

+ one i love a well set up M20.

Mine has the following;

*Cat Cam (think its a 274 but forget).
*Slight head skim
*BTB 3 manifold and crossover
*Fritz bits exhaust.
*Mild Chip from Speedtouch

Its a very different animal from standard, it has a 3.91 slipper diff which is a little bit much for motorway driving but if you jump on the noisey pedal too vigorously it will light up the rear wheels through 2nd and 3rd as it comes on cam and the noise is savage

Never been on the rollers but my arse dyno says somewhere around 185ish maybe closer to 190 as it is a lively little thing.

Tue Apr 17, 2012 11:59 am

TBH with you all In my ponion i would give the M20 B25 a lot more CR then cam it with either 272 or 274 depending on how aggressive you want it to be
Exhaust is questionable budget depending of course
Then its all about MAF or Alpha N on these engines
But its olny miller who have sorted a reasonable kit for sale to my knowledge.
But i have seen over 200bhp on a mildly tweaked 2.5 running mega squirt

so the potential is there for some good tuning option but for bang for buck its 24v route but it lacks soul in my personal opinion.

Tue Apr 17, 2012 5:38 pm

have heard stories of people fitting a 320i cam to the 325i.. its meant to have more lift if memmory serves. dont quote me on that one tho..

Tue Apr 17, 2012 7:08 pm

DmcL wrote:have heard stories of people fitting a 320i cam to the 325i.. its meant to have more lift if memmory serves. dont quote me on that one tho..

never heard that one before lol.
but IIRC diamlerman (malc) used the cam from a 323i in his 2.7 build & he claimed that cam was a bit more lairy.

Tue Apr 17, 2012 7:15 pm

Anyone know where a Jim Conforti chip can be bought?

I hear Halfrauds sell power bands.

Tue Apr 17, 2012 9:33 pm

steve_k wrote:Dmcl, thanks for the "shopping list" I know what I'll be looking for when I'm next at the scrappy.
just got to figure out how to do the engine loom (removal & refitting) as I ain't got a clue about that.

I'll read the thread in that link fully tonight.

I currently have the diagrams for this sat at the side of the bed.

From what i can gather a single vanos ecu should work as well with either the vanos just disconnected or a vanos delete chip. (if the vanos is open circuit then i have been informed that it will just run on the vanos retarded map and wont switch the vanos, if a vanos delete chip is used then both maps are set to the same as the vanos advanced map in the chip.)
Either way it should make no real odds when it comes to tuning, as both maps could be set to the same m20 map right?
It would just be a vanos delete chip with an m20 map.

I can see a couple of benefits to running the single vanos m3.3.1 rather than the non vanos m3.1
- knock sensing
- option to have an immobilizer that actually works on the e30
- Hot film rather than hot wire MAF, This allows a wider choice of larger MAFs as the m3.1 will only work with the m50nv MAF.
The M3.3.1 should be able to use any of the later hot film MAFs.

In terms of wiring i have been looking at it using a slight modification to the e30 loom with an extra bit added on to cover the extra functions of the m3.3.1 ecu.
This would then be adapted to the ecu pin configuration by a plug and play adapter allowing either ecu to be used without a full rewire.

Everything required to do the swap has been done in part before, its just going to be a case of combining the MAF conversion wiring, The m50 swap wiring and a few bits people do from the megasquirt conversions.

I made a thread in m50/52 chat to ask a few questioned that just turned into me and dan brainstorming.
Ill start a new thread in the m20 section to discuss what i have already worked out.

Wed Apr 18, 2012 8:06 am

yea it should be possible to use a single vanos setup as u say.. never really thought about it as the non-vanos setup has been done a few times with decent results.

didnt know the MAF's were different.. regarding the MAF's, i havent looked into it but i would imagine it should be possible to basically copy the map data from a single vanos AFM/MAF map or map set and paste it into the same map set in the non-vanos ECU/tune.

may not be quite as straight forward as that in terms of getting it running as it would with the ECU it was originally used with.. may require some further adjustment or worst case tuning from scratch but if both MAF's are 12v in/0-5v out or 5v in/0-5v out and have the same number of pins on the connection to the loom then it should be possible to run either MAF with either M50 ECU.

FWIW i have got the original M20's motronic 1.3 running on a bosch 4 pin 12v in/0-5v out MAF. last setup i played around with used a volvo T5 MAF sensor but in a larger 3 inch housing from a a dud bosch MAF i found in the scrapyard.

Wed Apr 18, 2012 5:55 pm

Its what image eventually thinking of running on mine for economy benefits and better sequential lpg.
As i say ill make a new thread for this one as a few people seem really keen on it.
Atm image just working out what i need and gathering bits as i will have to change my insurance about before i can do the deed regardless if having the time to do it.

What do you think with regard to the knock sensors if the m3.3.1?
I know they will be of huge benefit in theory but do you think recon that the m20 should have similar knock resonance to the m50?
With both being iron block, alu head 6 pot engines with very similar blocks....

Fri May 04, 2012 8:44 pm

Right then, can some one post an exact list of the parts needed? So as I know what I'm looking for when I next go down the breakers.

also does anyone one know the rough cost of this set up/conversion??

Sun Jun 24, 2012 10:44 am

To the OP.

my 1st post on this thread was the spec of my current lump.

the new lump about to go in is much the same but with the following.

0.5mm overbore.

sump baffle to try & prevent oil starvation if I decide to take the car on the track.

& also maybe a crank scraper to try & get rid of the parasitic drag on the crank caused by the oil mist in the bottom end.

should make for a (hopefully) "hot" B25 when it's all done & set up correctly after the remap.

Sun Jun 24, 2012 1:38 pm

Just figured you might find this of interest?

This was the initial dyno print-out of my 2.5 m20, at Surrey Rolling Road.

Had the car on the Surrey Rolling Road dyno again a week or o ago, so I can see if the 6 branch made a real difference.....or not.

Well, it made 170 and as you can see, there is a slight improvement right across the rev range. The mixture leans off at the top though and I probably lose a couple of brake as a result.

This is after a service & running a 'Speedtouch' wild chip. The 6 branch is of unconfirmed origin but is a nice bit of kit - unlike some I have seen.

I could go the route of hot cam, standalone ignition etc but the bang for buck just isn't enough when I can slot in an M52 & M50 inlet to gain another 50bhp. (just my opinion and not a slur on anyone sticking with their m20)

My M52 in the e21