Motronic 323?

Post Sat Mar 21, 2009 7:52 am

Not sure this is the right section but anyway:

I'm thinking of stroking a spare M20B20 that I have with M20B23 crank and pistons. Due to lack of piston choice I don't think I'll be able to do eta or M21 crank. (15mm increase in stroke, even with the 323 pistons they'll stick up above the block 2mm)

The questions are:
1) Moving from 80mm 66mm bore and stroke, to 80mm 76.8mm, which cam should I use for low end torque and streetable power. Can I stick with the 320 cam?
2) Which chip is going to be best to use (325 or 320? I realise this is partly dependent on cam)

Has anyone ever motronic'd a 323 before?

Post Sat Mar 21, 2009 8:33 am

I was going to do this until I couldn't get 323i pistons.
My plan was to stick with the 320i cam, as mine was in good nick. It's slightly uncharted territory - which is precisely why I wanted to do it. As long as you have - or can find - a crank and a set of pistons, you'll be fine.

As I couldn't locate the pistons, I scrapped a good 323i crank and a good 320i Motronic block.

If it does all work out for you, I have a Motronic ECU all chipped-up ready for a 323i. Any good to you??

Best of luck with it. I'm still disappointed it didn't pan-out for me, even though I'm happy with my 2.7.

Post Sat Mar 21, 2009 8:46 am

I have found a possible source of 323 parts. Basically I started looking amongst the E21 community as 323's are more common with them. I'm hoping that these are the same but I'm aware that the early head was different so it's possible the piston heads are different too. (no valve cut-outs?)

My car is already a 320i and I have a spare B20 on a stand. So the only other part that I think I will need is the chip. It's possible though that I may need 325 injectors, FPR, a different cam, AFM? The stroke and capacity is closer to 325 than 320.

What are the details on your chip? Was it custom programmed?

Post Sat Mar 21, 2009 9:08 am

gudgeon wrote:I have found a possible source of 323 parts. Basically I started looking amongst the E21 community as 323's are more common with them. I'm hoping that these are the same but I'm aware that the early head was different so it's possible the piston heads are different too. (no valve cut-outs?)

My car is already a 320i and I have a spare B20 on a stand. So the only other part that I think I will need is the chip. It's possible though that I may need 325 injectors, FPR, a different cam, AFM? The stroke and capacity is closer to 325 than 320.

What are the details on your chip? Was it custom programmed?

I don't know any specific details of the chip, other than it's for a standard 323i. It was done by Ant for Ed325i and IIRC Ed didn't know anything specific about it either.
The 320i injectors are good for 200bhp, so as I see it, 325i ones won't be necessary for a 323i. The 323i cam is slightly milder than the Motronic 320i one but it shouldn't be different enough to make a different chip necessary.
I was hoping for about 160bhp and about the same torque (based on the L-jet 323i being 150/150)
Other than that, I can't be any more specific except to tell you my planned spec..... Everything standard 320i except for -
323i crank and pistons
323i Motronic ECU
325i FPR, TB and possibly (never got 'round to measuring to make sure they'd fit) 325i valves.

Hope this is some help to you.

Post Sat Mar 21, 2009 9:10 am

Forgot to say, I'll have a look at my Mahle information on pistons for you, but it won't be until later today.

Post Sat Mar 21, 2009 9:19 am

Very very interesting thanks.

Weren't all 323's L-Jet?
What is a 323i Motronic ECU? Do you mean the Motronic 1.3 with a chip change?

If Ant produced a chip, he must have had an injector setup and cam in mind.
Perhaps he remembers and will post a quick reply (hint

)

Post Sat Mar 21, 2009 9:23 am

StuBeeDoo wrote:Forgot to say, I'll have a look at my Mahle information on pistons for you, but it won't be until later today.

That would be great!

Post Sat Mar 21, 2009 11:29 am

gudgeon wrote:Weren't all 323's L-Jet?

Yes.

gudgeon wrote:What is a 323i Motronic ECU? Do you mean the Motronic 1.3 with a chip change?

Yes again.

gudgeon wrote:If Ant produced a chip, he must have had an injector setup and cam in mind.

AFAIK it was purely to convert a standard 323i to run on Motronic.

gudgeon wrote:Perhaps he remembers and will post a quick reply (hint )

Post Sat Mar 21, 2009 8:19 pm

So a standard e30 323i would have a 731 head and 320 injectors I think. What about the cam?

Post Sun Mar 22, 2009 8:42 am

gudgeon wrote:So a standard e30 323i would have a 731 head and 320 injectors I think. What about the cam?

OK. The E30 323i used a cam with 253deg duration, as did the L-jet 320i. The Motronic 320i had 260deg duration.

The E21 323i used pistons which gave 9.5:1 compression, but IIRC it also had the "200" 'head which may have had different chambers and/or valves (I've never seen one so I don't know for sure, I'm just guessing). I can't tell from the info I have if the 9.5:1 pistons are flat, dished or domed.
E30 323i pistons are definitely domed and with the 731 'head give 9.8:1 compression.

You need to make sure you use the Motronic injectors, the L-jet ones from the 323i are different and I'm told they will fry the Motronic ECU.

Hope this is of some help.

Post Sun Mar 22, 2009 9:06 am

Very useful information thanks.

I don't expect that either the 320 cam or slight difference in compression will make much difference (unless un-domed pistons (e21) and a larger head combustion chamber (731) make a huge compression difference).

[The 200 head definitely had smaller valves, which is why I'm a little worried that the 323 pistons may have no valve cut-out. I suppose I should be able to get one machined in, especially with a spare 320i piston for reference. It all adds to the cost though.

EDIT: THE ABOVE IS INCORRECT. My false assumption has just been exposed on another thread, which is very good news as the pistons should work fine.]

I've got a crank lined up, and a guy who thinks he may have some 323 pistons at his folks' house.
How much would you sell your chip for?

Also going to need:
Block re-bore of a couple of thou'. (What are the limits for piston clearance?)
Bearings and possibly a crank re-grind.
Small end pins and rings.
Engine seals and gaskets.
Head valve seats and valves.
Differential!

Post Sun Mar 22, 2009 9:17 am

gudgeon wrote:I don't expect that either the 320 cam or slight difference in compression will make much difference.

If you're wanting as much mid-range as possible, I suspect the 320i cam to be the weapon of choice. It's what I would have used, and mid-range was what I would have been after.

gudgeon wrote:How much would you sell your chip for?

Yours for £40 including the postage sir! (That's what I paid for it.) PayPal accepted. IIRC, Ant quoted me £65 to do one a year ago.

Post Sun Mar 22, 2009 9:22 am

Great thanks. Yes, I think the 320i Cam will be fine.
I'm holding off for a while until I know the availability of all the parts.

Post Sun Mar 22, 2009 11:04 am

gudgeon wrote:Great thanks. Yes, I think the 320i Cam will be fine.
I'm holding off for a while until I know the availability of all the parts.

Sensible! I found out the day after the ECU arrived from Ed that the pistons I had were no good.
I doubt the ECU will be going anywhere, just let me know if you want it.

Post Mon Mar 23, 2009 10:08 pm

Gudgeon,

One thing I also have is a set of 9:1 Mahle ETA pistons in the garage. No eta crank anymore as that went in my E30.
These would work with an Eta/td crank and 200/731 head to produce a 2.7.

These where bought new in about 1986 when my dad build a 2.7 in his E21 with ported 200 head. Would probably require new rings.

Duracel79

Post Tue Mar 24, 2009 6:24 am

Aren't the ETA pistons 84mm bore?

I want to use the 320 block. (and I'd rather not re-bore other than the bare minimum required to stroke it (a couple of thou)).

If it came down to it can the 320 block be bored to 84mm or is this too much?

Post Tue Mar 24, 2009 9:50 am

gudgeon wrote:If it came down to it can the 320 block be bored to 84mm or is this too much?

Yes it can.

Post Thu Mar 26, 2009 7:05 pm

To use that ecu on a 323 you have to use 2.5 injectors / airflow meter and would be a good idea to use the 2.5 inlet manifold to.

Post Fri Mar 27, 2009 11:02 am

When you have finished sticking pins in your eyes and standing on burning coals you can come and give me £350 for a sweet running 171 BHP 325 engine complete with loom, ecu and all ancillaries

Post Fri Mar 27, 2009 11:56 am

"To use that ecu on a 323 you have to use 2.5 injectors / airflow meter and would be a good idea to use the 2.5 inlet manifold to."

Interesting. If I do all that then it also settles the 'which cam' question too. Thanks very much for the info. Were you planning on doing something similar when you bought the chip from Ant?

"When you have finished sticking pins in your eyes and standing on burning coals you can come and give me £350 for a sweet running 171 BHP 325 engine complete with loom, ecu and all ancillaries"

Yes I know it's masochistic, but believe it or not I'll get more satisfaction this way. If I just wanted a fast car I'd go out and buy one.

Post Fri Mar 27, 2009 1:53 pm

Can anyone tell me how much bigger a 325 AFM is over a 320 AFM? (bore diameter?)

I understand that the AFM must match the ECU, but I'm curious if a 320 AFM would work at greater capacity with a custom chip.
Which one did the ETA use?

Post Fri Mar 27, 2009 1:58 pm

ETA AFM is oddball as shes a moronic 1.1 car.

Post Fri Mar 27, 2009 2:14 pm

Ah! Thanks for that.

One of my aims with what I'm trying to do is to keep my engine bay looking as stock 320 as possible.

It occurs to me that with 325 AFM, Injectors, Cam, FPR, a 76.8 stroke and 2316 capacity the stock 325 ECU is not going to be far off working. Would be more worth my while leaving most stuff stock and then getting a custom remap on a dynamometer. I'm pretty sure the injectors are up to it, I'd probably change the cam for the hell of it, the AFM I'm unsure of.