The comprehensive 731 head + eta block Thread

[Stephen]

I've been doing some searching and while there seems to be some knowledgable people on here, there isnt a thread focused on it.. so here goes

From what i've read, it can be as simple as bolting in the 731 head and running a chip.

Others have suggested using the i harness [ but then do you have to swap other things?]

^this is what i've learned so far but the point of this thread is to get some conclusive info. So if i'm wrong, please correct me. Feel free to elaborate on other setups, like using l-jetronic.


I'm not too likely to run this setup unless i can find a nice head thats nott much money

[eta]

Well my 525e UK spec is getting this treatment.

M20B27 bottom end and block
731 cylinder head
M20B25 inlet manifold and injectors
3.0 bar FPR
M20B25 AFM and ICV
Motronic 1.3 with chip by A-tech in UK.
5-speed close ratio g/b
3.46:1 final drive (medium case)

Problems so far. Some of the front pullies on the eta don't work with the front trigger wheel from motronic 1.3 system.

Head bolts striaght on. Inlet ports need reshaping using a inlet manifold gasket from the 2.5 as a template. As I am using the 2.5 injectors a 173 ECU has to be used. The 164 ECU will work apparantly as well but I was warned against using one due to reliability issues. The chip maker has furnished me with a 173 ECU at no extra cost.

2.7 Chip by A-tech in the UK £65.

Wiring should be OK but I will update. One issue the motronic 1.3 has an extra wire for the starter, thats odd where does it go.

Gearbox bolts straight up and a M20B20 clutch fits.

A nice little widget from www.seattlecircuit.com to correct the OBC for the larger injectors has arrived.

Otherwise all is good in M20 land.

I do have a spare 731 head going with a 2.0 inlet manifold. The head has a tappet issue so ay need a rebuild but is other wise sound, although I have stripped it down.

[jlevie]

One issue the motronic 1.3 has an extra wire for the starter, thats odd where does it go.

That wire goes to C101 and is used to operate the unloader relay. Your car won't have that on the body side of C101, so you can leave the wire disconnected.

[Arems87e]

Just few months ago, i did this set up....

-731 Head+eta block
-I manifold and I throttle body
-complete I exhaust with headers
-chip

However, am still yet to swap to motronic 1.3 so for now everything else is stock. Am prob just gonna get the the MarkD 327i for my DME so i wouldn't have to do the swap. But without all that, the difference is incredible, compare to stock.

Like the previous guy said, "It bolts straight on"

[kronus]

Just few months ago, i did this set up....

-731 Head+eta block
-I manifold and I throttle body
-complete I exhaust with headers
-chip

However, am still yet to swap to motronic 1.3 so for now everything else is stock. Am prob just gonna get the the MarkD 327i for my DME so i wouldn't have to do the swap. But without all that, the difference is incredible, compare to stock.

Like the previous guy said, "It bolts straight on"

Which chip did you use? What Motronic version did you start with?

[Arems87e]

Which chip did you use? What Motronic version did you start with?

I'm still running my stock ecu (027) and in it is the regular performance chip that i bought a while back before tha head swap.

[kronus]

OK, what intake boot did you use? You'd need to use an e AFM, and as far as I know, there is no boot that goes from e AFM to i throttle body...

[kenika65]

Click on this link!

http://www.r3vlimited.com/board/showthread.php?t=100939

[Arems87e]

Of course the e boot WON'T fit. thats why i'm using the I boot. But click on that link above, by Kenika65 It's got tons of info....If u r planning on doing this swap, i'll advice u to swap to the I motronic at the same time. i wish i had done it when i did mine, now am reluctant to do it, cause i'm sick wrking on the car....lol But now that i bought a 325is parts car, i would def be doin it.

[E30 Wagen]

I'm curious to know what kind of fuel mileage you're getting, Arems87e?

[SpecM]

OK, what intake boot did you use? You'd need to use an e AFM, and as far as I know, there is no boot that goes from e AFM to i throttle body...

all m20 AFMs are the same size diameter

[E30 Wagen]

what would the rev limit be with a b25 cam? I've got motronic 1.1, but ironically i don't have a standard 325i instrument cluster. I still have my eta cluster, though. Could I use my eta cluster with 1.1? I feel like i should know this but i'm going to ask anyway instead of searching. because i'm awesome.

But it would be nice if i could because it has the mileage of the eta block i'm gonna use.

[acefreely02]

what kinda power does this render?.. cus it will keep the stock 9.0 to 1 c.r.... but will allow the engine to rev a bit higheri if using the 325i cam or the 323 cam..

also for the power in the higher end the head should be ported to amtch the 2.5 manifolds.. if its not it will choke itself due to the smaller ports and not getting enough air at the top end of the rev range..

the engine in theory might run a bit hotter, or at least the head will due to the higher revs, more gas , and more air.. thats one very good advantage the 885 head has over the eta head and the 731 head... ive read that getting a thermostat that opens at a lower temp is a good investment...

you can you I electronics but there is thje mark d e to i chip. or 327i chip by jim conferti...

as far as mileage goes it should be quite good if everything is running right.. theres no drop in c.r so factoy eta milage should still be capable.. and with the ported head and bigger intake manifold and Tb of the "I" a 2-4 mpg increase can be an expected..

ive also read that if you run the 731 head and 2.5 top end bla bla bla without the chip or changing over to the "i" electronics the idle will be a bit ruff...


thats as much as i can think of right now.. if i remeber anytihng else ill post it.. not really on r3v that much. i kinda stick over at e30tech

seen a vid of a eta with 731 head and e to i chip. and in a straight line it walked all over a stock 88 325i with dinan chip..

[g323]

as far as mileage goes it should be quite good if everything is running right.. theres no drop in c.r so factory eta mileage should still be capable.. and with the ported head and bigger intake manifold and Tb of the "I" a 2-4 mpg increase can be an expected..

Lowering C.R Decreases Mileage? So going from a 323i Stock to a 327 stroker with the 731 head will lower my compression ration from 9:8 to 9:1? Bringing my mileage down with me?

[E30 Wagen]

what kinda power does this render?.. cus it will keep the stock 9.0 to 1 c.r.... but will allow the engine to rev a bit higheri if using the 325i cam or the 323 cam..

also for the power in the higher end the head should be ported to amtch the 2.5 manifolds.. if its not it will choke itself due to the smaller ports and not getting enough air at the top end of the rev range..

the engine in theory might run a bit hotter, or at least the head will due to the higher revs, more gas , and more air.. thats one very good advantage the 885 head has over the eta head and the 731 head... ive read that getting a thermostat that opens at a lower temp is a good investment...

you can you I electronics but there is thje mark d e to i chip. or 327i chip by jim conferti...

as far as mileage goes it should be quite good if everything is running right.. theres no drop in c.r so factoy eta milage should still be capable.. and with the ported head and bigger intake manifold and Tb of the "I" a 2-4 mpg increase can be an expected..

ive also read that if you run the 731 head and 2.5 top end bla bla bla without the chip or changing over to the "i" electronics the idle will be a bit ruff...


thats as much as i can think of right now.. if i remeber anytihng else ill post it.. not really on r3v that much. i kinda stick over at e30tech

seen a vid of a eta with 731 head and e to i chip. and in a straight line it walked all over a stock 88 325i with dinan chip..

Thanks for the post! I am going to look into getting the inlet ports enlarged to match a 325i intake manifold. I hope that isn't crazy expensive.

Edit: But, can I use my eta cluster with motronic 1.1?