Clarko's M20 Build - Has started...

[clarko74]

Afternoon all,

I thought I would start this thread as I've finally made a start on my M20 2.8 build. This could take a while but hopefully I'll get there in the not too distant future.

Here's the list of bits I have so far:

• M20B20 block, to be bored out to 84mm (thank you Trev)
  M20B20 130mm rods (again from Trevor)
  Ported 885 head with Schrick 284/272/110 cam (from Theo a long time ago)
  BTB3
  BBTB
  M20 injectors Newly refurbed

I still need to source some pistons and would appreciate any advice on whether to go for the high or low comp ones? Originally I was thinking of going for high comp ones but after reading the wiki I'm now not so sure as I don't really want to have to use super unleaded all the time.

Anyway, after picking the block up from Trev the other evening and it sitting in the boot of my E30 since then I thought I'd start by trying to get the crank bolt out. So in true council fashion myself and a collegue got the lump out in my work car park this lunch time and got to work on it. a few bits of wood, a 2ft breaker bar and a bit of scaffolding later and it's out. Wasn't as much of a nightmare as I thought it would be tbh.

Next job is to strip down the block and get it cleaned up prior to the rebore.

[clarko74]

Here's a pic of the exhaust side of the head I have compared to a standard 885 head:



They are a fair bit larger. I'll have to have a measure to find out by how much and also look at the inlet side to see I've they've been played with too.

[SteSE]

I was thinking of your car the other day bud. Nice to see you still got her, even better about its new heart. Good work!

[clarko74]

Good to hear from you Steve. Trev and I were talking about your car the other day as it happens, sounds like you've made a few tasty upgrades since we fitted that windscreen a few years ago.

[reggid]

if you plan to properly tune the engine you can run the high comp 9.7:1 piston with a bigger crank and dr284 on premium. im sure you would not go to all this effort to do this and not get a proper retune....if you want to run shite fuel then go lower comp

the higher comp and proper head to piston squish clearance will certainly be better but you may not be chasing 5hp

[clarko74]

Yes, a remap is definitely something I plan on doing and when you put it like that it seems to make sense to go for the high comp pistons.

[reggid]

Yes, a remap is definitely something I plan on doing and when you put it like that it seems to make sense to go for the high comp pistons.

i recommend a tune getting rid of the AFM if the budget can stretch

[clarko74]

Yes, getting rid of the AFM is definitely on my list. I'm a bit unsure of which direction to go though, I know there's the Miller MAF (but have no idea of the cost), there is goosiegander's MAF hat Ant did and looked very good, but none seems to know how this was done in detail apart from Ant, who's not involved with e30's any more (which is a shame as he was only a few miles down the road from me) and hairyscreech's motronic 3.1 upgrade looked promising but I'm not sure it that ever got fully resolved and working.

I think I need to do some more research.

[reggid]

Yes, getting rid of the AFM is definitely on my list. I'm a bit unsure of which direction to go though, I know there's the Miller MAF (but have no idea of the cost), there is goosiegander's MAF hat Ant did and looked very good, but none seems to know how this was done in detail apart from Ant, who's not involved with e30's any more (which is a shame as he was only a few miles down the road from me) and hairyscreech's motronic 3.1 upgrade looked promising but I'm not sure it that ever got fully resolved and working.

I think I need to do some more research.

maybe find a place that has tuned a few M20 and see what they recommend

[Ant]

always the same thing Dudes..... piggyback ecu lol !

@Clarko, Email replied to x 2

CR is the key to a nice 2.8 - most are a tad low 9.75:1 B25E1 piston crown shape FTW

[clarko74]

Thankyou for the emails Ant, very much appreciated. I am now frying my brain trying to get to grips with the ins and outs of motronic mapping! I have found the AFM formula and plotted a nice looking chart in excel using the 3 AFM maps (and the M30 as well just to see what it looked like) :



I was thinking of somehow fixing the MAF in series with the existing AFM then taking voltages of both at the same time, then I can adjust the map values so the curve fits the line of the MAF output.

Anyway this is all off topic, My new block is still on the garage floor, I have an engine stand, but no bolts to get it on there yet. Anyone know what size bolts or threaded bar I need?

What are B25E1 pistons? are they the prefacelift ones?

[clarko74]

CR is the key to a nice 2.8 - most are a tad low 9.75:1 B25E1 piston crown shape FTW

What would you say is a good CR to aim for?

[reggid]

with the B25E pistons they will be about 10.7 which is really good if you fix the anomaly with the different stock height of M52 crank and eta rod vs b25 rod and piston

[Kedge]

My M20B28 uses the high comp pistons and has had to have 2mm taken out of the valve pockets as Dan was trying to max out the CR while keeping suitable clearances with the 272/272 cam.

Not sure what my CR is now but Dan measured it at 10.3 before the block was skimmed and the pistons worked.

[steve_k]

Watching this with interest, would it be possible to use the moates ostrich 2.0 piggyback to run it??

[Ant]

the Moates is not a piggyback, it emulates the Eprom but you can read/write to it in realtime Steve.

Good piece of kit, I have 2 and an old dataman S4 which is my favoured tool

E1 pistons, 0.5mm decking ( 205.5 crank CL to deck height ) should net a static CR of 10.5 ish ( very very rough calc )

I'd consider that the minimum CR to be worth the hassle, don't forget cam overlap/dynamics will reduce the CR , VE will have an effect here too.

[steve_k]

the Moates is not a piggyback, it emulates the Eprom but you can read/write to it in realtime Steve.

Good piece of kit, I have 2 and an old dataman S4 which is my favoured tool

E1 pistons, 0.5mm decking ( 205.5 crank CL to deck height ) should net a static CR of 10.5 ish ( very very rough calc )

I'd consider that the minimum CR to be worth the hassle, don't forget cam overlap/dynamics will reduce the CR , VE will have an effect here too.

I might be being thick but do you need to remap the moates ostrich?? Can someone explain how it works??

[Ant]

you need to upload the stock/modded map into the Ostrich, this has an "emulead" on the output side with a DIP28 pin Eprom header on it, this goes into the Eprom( Chip ) socket on the ECU

the car will run/start/drive like the eprom is in place whilst you manipulate the maps in realtime, once finished you blow the file to a fresh Eprom and fit that back in ECU

job jobbed

extra bits you'll need are an Eprom burner/reader and some s/ware for the actual mapping, then a descriptor/offset file so you can see what maps do what and why/when.

@ Clarko

your plan is a great starting point for sure , the MAF is more linear in output vs those plots ad reacts to a load change much much faster as there is no mechanical damping forces.

AFM's tend to open beyond the required load and then dampen back once the load/airflow is stable again so eg 1.5V load then 3V load may see the afm signal go to 3.6V then drop back to 3V - I call it the AFM shuffle .

I looked at the .dxf file you sent in your last email, has issues but will get ya there

[steve_k]

Sorry for the thread hijack.

Hi ant thanks for that just had a search on google & seen a few threads about leaving the ostrich in place & on while driving, is this possible??

Again sorry for the thread hijack.

[Ant]

Hi Steve

you can leave the Moates in place and use it as a flashable ECU in that form

HTH

[steve_k]

Hi Steve

you can leave the Moates in place and use it as a flashable ECU in that form

HTH

Cheers ant

[Jon_Bmw]

Hi Steve

you can leave the Moates in place and use it as a flashable ECU in that form

HTH

Cheers ant

I've done around 6 trackdays with an Ostrich in place as I was too lazy to burn an eprom. That was in a rattly old 205 with significantly more abuse put on it than you will on the road! It was fine. I only changed to an aftermarket ECU due to ITB's.

Tunerpro lets you work out which maps do what, to some degree. It is free shareware I seem to remember. I can't remember how well it works. Even without TunerPro my brother, who is a software engineer, could understand it all far more than I could!

[Ant]

Tunerpro is excellent and should be supported all the way.