m20b28 problem

[BobbySD]

Hello guys,
I have some problems with my b28 build so I want to ask if somebody can help me or get some advice.

My build consists of m52 crank, m20b20 rods, m20b25 8,8:1 pistons, 0,5mm of the block and ant chip. Problem is that engine isnt run very smooth and is loosing power in higher revs. Friend of mine which build a very very powerful m20 turbo thinks that I have high compression ratio and I have to lower it. His advice is to use M54b30 rods and pistons. Im bit confused because I dont know where is the problem if in compression ratio or in fact that I dont have sport cam atm or somewhere else...

Ill be very glad for any advice or opinion.
Here is block with pistons (think they are bit much out of it??)

[StuBeeDoo]

Doesn't look to me like there's anything wrong with the parts you've used. IIRC, Goosiegander has built an engine to the same spec. Your engine should run OK with the c/r you have, it probably isn't any more than 10:1.
IMO you need a remap.

[HairyScreech]

oops, just posted this here allong with my thoughts for him.

i got this earlier today,

hello Hairy Smile
let me introduce Im Bobby from Czech Republic and I done a 2.8 build m20 but I have some problems with it.
I read a lot about 2.8 here and you were everywhere so I decided to contact you and hope you dont mind. My problem is that my build isnt run very smoothly and loosing power in higher revs.
I have done everything exactly like is written here http://www.e30zone.net/e30zonewiki/inde ... ding_a_2.8
that means I use ant chip, m52 crank, m20b20 rods, m20b25 8,8:1 pistons and I shave block by 0.5mm.
I was spoken to some guys from here but only one have the same build and he thinks that I have too big compresion ratio. From that article i should have 9,75:1 but is it real if you look on my block here

Isnt is too much out of the block for 9:75?
Thank you for any advice Smile

now my suggestion has been this:
firsly a skimmed block will give the CR as follows:



so i dont think his CR is too high unless the chip is written for a 9.3:1.

the pistons dont protrude too much as the block has been skimmed, looks like fairly stock protrusion to me.

im thinking this is a mapping issue rather than a mechanical issue.

just a thought can anyone tell if there high or low comp pistons from that shot?

bobby do you have a top down and side on picture of the pistons?

did you have to take any off the skirt? if so how much?

[GeoffBob]

What MAF does this conversion use, and is it calibrated? It doesn't matter how good the chip is, if the MAF signal feeding the ECU is not an accurate representation of how much air is actually flowing into the engine then she'll likely run like crap. Ant's chip needs to know exactly how much air is flowing into the engine in the first place to be able to accurately inject the correct amount of fuel.

Barring that, check your fuel injectors (are they clean and/or the correct ones for the conversion), check your fuel pressure regulator, and check that your fuel pump can supply the required volume of fuel at the specified pressure while the engine is running under load. Many great conversions have been spoilt by keeping the original and possibly knackered fuel pump.

One other thing I noticed, your engine is upside down

[BobbySD]

One other thing I noticed, your engine is upside down

Engine is from 3/89 so it should be low comp.Ill try to find photos and post it here. And as i wrote above crank, rods, chip and 0,5 off the block are only mods which I do. I was following article on the wiki here about building a 2.8.

[BobbySD]

I write VIN to realoem.com and I found that I have mahle low comp. pistons 11251735755. unfortunately I didnt find any other photo

[goosiegander]

What MAF does this conversion use, and is it calibrated? It doesn't matter how good the chip is, if the MAF signal feeding the ECU is not an accurate representation of how much air is actually flowing into the engine then she'll likely run like crap. Ant's chip needs to know exactly how much air is flowing into the engine in the first place to be able to accurately inject the correct amount of fuel.

Barring that, check your fuel injectors (are they clean and/or the correct ones for the conversion), check your fuel pressure regulator, and check that your fuel pump can supply the required volume of fuel at the specified pressure while the engine is running under load. Many great conversions have been spoilt by keeping the original and possibly knackered fuel pump.

One other thing I noticed, your engine is upside down

Hi Geoff, i think the chap means he has the direct replacement motronic 1.3 chip with AFM as opposed to a MAF setup,

Very good advice though and in no way intended as critisism

[goosiegander]

BobbySD - Did you replace your blue temp sensor?

[goosiegander]

Doesn't look to me like there's anything wrong with the parts you've used. IIRC, Goosiegander has built an engine to the same spec. Your engine should run OK with the c/r you have, it probably isn't any more than 10:1.
IMO you need a remap.

Indeed so dude, although to my knowledge (which is limited) the conversion requires a cam to be effective, the OP has skimmed his block which should have retarded his cam timing, vernier needed me thinks.

[GeoffBob]

Hi Geoff, i think the chap means he has the direct replacement motronic 1.3 chip with AFM as opposed to a MAF setup,

Very good advice though and in no way intended as critisism

Oooops , sorry Goosie. As above then, but applied to the AFM, not MAF I am inclined to agree that the problem is not the compression ratio, but I would still check the fuel supply is up to scratch (pressure and flow under load) before blaming Ant's chip. I am not a big fan (personally) of generic chips, but if it is just a small problem (fuel in and out lines the right way around?) its worth finding before throwing the baby out with the bath water

[BobbySD]

goosie: y I was tryin to replace him

about cam timing... that was first think what comes to my mind... Im going to get new cam next month. I want to check all possibilities what can be wrong and fix it at one time...

thank you guys

[HairyScreech]

how badly if it running at top end?? just a bit flat or misfiring and back firing?
can you describe the bad running?

what revs dose it begin to run badly at?

what revs is it ok at?

hows the idle?

the 0.5mm skim will retard the cam but theres no reason it should be enough to cause trouble, 0.5mm is within factory spec for skiming the head after all, and skimming the block is the same deal.

im having brain trouble today, but wont retarding the cam a little result in the cam actually working better higher in the rev range, as the valve is shutting later at tdc, or am i thing arse about face?

with the size of the cam pully i dont thing 0.5mm will make a large difference, maybe a degree or two at most. ill work it out later, its only working out the circumference of the pully, then working out how many times 0.5mm fits into that, then using 360/that to get the angle turned for 0.5mm at the radius.

[BobbySD]

idle is relatively ok but I can hear that the engine is jerking from time to time nothing extreme but I hear it. When I pull the throlle from -3000 rpm I feel the power and think its ok 3000-4500 still ok but it feels that engine is loosing a bit but about 4000 there is a typical m20 kick-out, 4500-6500 rpm only goes higher there's no power. Sometimes... when pulling throlle on the floor it loose power for 2-3sec like there were no fuel and then its ok until rev limiter

few months ago I was tryin to record that jerking but its very hard to recognize...
when I go to other side of engine focus on cable from brown temp sensor it shakes from time to time and thats the jerking of whole engine. Its more obvious in real that video looks like engine is ok
http://www.autodily-bob.cz/b28.rar

and here are two video of driving... first is with 3,25 diff lolz thats why is so slow but you can se that at higher revs its not too much responsive... especially when I shift 4th.. second is with 4,27 and you can see in 0:20 throlle on the floor and few sec nothing happend... and those sounds at the end... it was reserve dif and I forgot to check oil in it

http://www.autodily-bob.cz/0000.3gp
http://www.autodily-bob.cz/noveb28.3gp

[CHR1S1990]

what exhaust manifolds are you using?

[BobbySD]

stock

[CHR1S1990]

they don't look like the stock m20 log manifold to me on the first video?

[StuBeeDoo]

they don't look like the stock m20 log manifold to me on the first video?

OP is in eastern Europe somewhere. They'll be the LHD ones. 2x3 with seperate downpipes.

[CHR1S1990]

thanks stu, didnt know they were different!

[StuBeeDoo]

thanks stu, didnt know they were different!

Mini-logs.

[Andyboy]

You will need a camshaft up to the job. A stock 325i cam will not be good enough and you will lose power at the top end. The 325i has a shorter stroke (thus slower piston speed) and the duration and overlap will be wrong.

[BobbySD]

You will need a camshaft up to the job. A stock 325i cam will not be good enough and you will lose power at the top end. The 325i has a shorter stroke (thus slower piston speed) and the duration and overlap will be wrong.

yea I will change the cam and will see... I only hope that the problem wont be in mapping cuz I dont know anyone around who can help me with this...

[Ant]

check the WOT switch is working correctly 1st common failure item and can cause all sorts of issues.

CR is fine, its low IMHO

If you provide some Rolling road data with AFR plots I'm happy to revise your mapping remotely should that be the issue

[BobbySD]

check the WOT switch is working correctly 1st common failure item and can cause all sorts of issues.

CR is fine, its low IMHO

If you provide some Rolling road data with AFR plots I'm happy to revise your mapping remotely should that be the issue

thnx m8 Ill check it. Ill write here some info after testing

[phelix]

Any news?

[BobbySD]

atm car is still sleeping in garage first I must save some money for new cam...

[BobbySD]

so after the winter I do some experiments on engine as my friend recommend me. I make new holder of crank sensor and move it by one sprocket. Also I set up bolt at AFM by 6 turns. Engine is now very calm, change sound a bit and idle is ok. But problem when I pull full throttle remains...options are bad cam timing or low pressure at fuel pressure regulator, nothing else comes on our minds...

[aceifty]

have you got it sorted.

i should be starting me m20b28 conversion soon, im going to replace all parts with new ones apart from the pistons.

[BobbySD]

yep problem is solved. I remap ecu properly and problem i gone. Now engine is runing very good and also power is satisfying