M70B54S or how to bring an ordinary 850i engine to CSi level

[wokke]

Wokke, Is all of this worth it?
I mean lighter rods, crankshaft and pistons is big $$ Not to mention Individual Throttle bodies.
Why not just supercharge or turbo the Fux&er?

IMO definitely NO.
Take the money and get a used E46///M3 or similar. Or if you have a bit more cash on the side get an E24///M635CSi.

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Mine is a lowly early M70 so I'm not avert to doing major surgery...

Question is whether 370ish is enough or do I really want 450+

It's not a question of need....

I guess the younger you are the more you "need" it. I admit that I meanwhile prefer driving my E38-750iL as a DD. Has more than enough power and is soooo much more comfortable.
My 850 is my toy and experimental car.
But even if you come to the conclusion that you need 450+HP:
you need a stronger gearbox
you need a stronger drive line incl. everything what comes after the guibo

And when it comes to FI I admit to have only driven two 850s with compressor engines and I haven't been impressed at all.
Might have been a poor setup, I don't know. But the low end torque I was expecting was definitely not there.

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I mean,, if you have both engines,, and instead of rebuilding everything and the M73B54 is in great shape,, just take the loom from M70 and change camshaft ((if that is the most simple way !))

if it just would be that simple
But it isn't. You need several M70 parts, even if you decide to keep the M73 heads.

[sleepy81]

Or if you have a bit more cash on the side get an E24///M635CSi.

+1
Just sold here at auction for A$48.5K. http://www.shannons.com.au/auctions/.../#.Vk2VkNIrK70

[wokke]

+1
Just sold here at auction for A$48.5K. http://www.shannons.com.au/auctions/.../#.Vk2VkNIrK70

WOW, maybe I should put mine up for sale

[Fatandre]

I think for 48k I would get myself a 911

[B10 BITURBO]

Interesting to read the comments,,, here

I agree with Wolf about High CR pistons,,, titan conrods etc etc cost,,, it is not worth it IMO,, the cheapest way to get great power out of M70 is TURBO,,,

but manual gearbox is a must,,,

i love the V12,,, is it wise to use that engine and do hefty N/A modifications ,, NO again ,, but wise is not always what we accept, and it is also a religion to use these engines,, internal is VERY STRONG,, it is not complexed at all,, but again there are other options and to those concerned,, the owner of each car will make his choice what he wants to do,,, more force,,, more $$$$$$$$$

[adwebinc]

I know this is an older thread, but I am finally able to get focused on this project. Wolf - I have reread all of your threads to get myself refreshed on the project. I also see there have been some direct swaps of M73s (including M73 heads). Given the progress made on this topic, what is the "best" path (I am aware best is relative)? Options are:

1) M73 bottom end with M70 heads. Upgrade options include Schrick cams and Wolf's chips. Benefits include using stock exhaust manifolds / downpipes. Performance with cams and chips ~370HP

2) M73 entire block. This will be challenging with the downpipe issue, but are there performance upgrade options / benefits? Looks like cams are more challenging to source?

I do have a clarification question regardless of Option 1 or 2. The M73N engine seems easier to come by around where I am located. If I change out the alternator bracket and the water pump to a non-M73N engine, are there any other issues in using the bottom end of the M73N block?

[dragon850]

I know this is an older thread, but I am finally able to get focused on this project. Wolf - I have reread all of your threads to get myself refreshed on the project. I also see there have been some direct swaps of M73s (including M73 heads). Given the progress made on this topic, what is the "best" path (I am aware best is relative)? Options are:

1) M73 bottom end with M70 heads. Upgrade options include Schrick cams and Wolf's chips. Benefits include using stock exhaust manifolds / downpipes. Performance with cams and chips ~370HP

2) M73 entire block. This will be challenging with the downpipe issue, but are there performance upgrade options / benefits? Looks like cams are more challenging to source?

I do have a clarification question regardless of Option 1 or 2. The M73N engine seems easier to come by around where I am located. If I change out the alternator bracket and the water pump to a non-M73N engine, are there any other issues in using the bottom end of the M73N block?

I would swap the entire M73 engine with custom software, in fact that is what I am doing. No need to mess around with the heads or cams. I can walk you through later, a little busy currently packing up your diff

[adwebinc]

I would swap the entire M73 engine with custom software, in fact that is what I am doing. No need to mess around with the heads or cams. I can walk you through later, a little busy currently packing up your diff

Sweeet! Yes, would love to hear more. Diff seal and oil has been ordered!

Really scratching my head on the lack of M73 engines around here, but several M73Ns available.


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[dragon850]

M73Ns will not work, water cooled alternator housing gets in the way.

[mikae31]

Sweeet! Yes, would love to hear more. Diff seal and oil has been ordered!

Really scratching my head on the lack of M73 engines around here, but several M73Ns available.


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what diff did you get and what do you currently have?

[adwebinc]

what diff did you get and what do you currently have?

Ordered a rebuilt 3.91 LSD from dragon to replace my stock 3.64 non LSD. I have a ‘91 4 sp 850.


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[mikae31]

Ordered a rebuilt 3.91 LSD from dragon to replace my stock 3.64 non LSD. I have a ‘91 4 sp 850.


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You are expecting a slight improvement in acceleration with slightly increased fuel consumption. Rpm will be about 2400-2500 when doing 100kmh (62mph). In my book a bit too much for the M70. Car will still be slow off the line.

this is my car with 3,91 and wokke V2 chips
https://youtu.be/RLj1qB4vyo0

[adwebinc]

You are expecting a slight improvement in acceleration with slightly increased fuel consumption. Rpm will be about 2400-2500 when doing 100kmh (62mph). In my book a bit too much for the M70. Car will still be slow off the line.

this is my car with 3,91 and wokke V2 chips
https://youtu.be/RLj1qB4vyo0

We are a bit off topic here, but I'm interested in your perspective because as I see it from your video:

1) you hit the gas at 3 seconds
2) you hit 60 MPH at 9 seconds
3) That's 0 - 60 with a VERY heavy GT car in ~6 seconds with loss of traction at launch

Seems pretty decent to me for just a diff swap (I already have Wokke's chips too). Maybe you want to swap out your 3.91 for my stock 3.64? Even trade?

[adwebinc]

Maybe I'm off base, but would using the down pipes from the M73 850 solve the exhaust issue when using the M73 heads? Not a cheap option by any means, but just curious if that's the easiest bolt on option:

M73 Project - Exhaust.jpeg

[mikae31]

We are a bit off topic here, but I'm interested in your perspective because as I see it from your video:

1) you hit the gas at 3 seconds
2) you hit 60 MPH at 9 seconds
3) That's 0 - 60 with a VERY heavy GT car in ~6 seconds with loss of traction at launch

Seems pretty decent to me for just a diff swap (I already have Wokke's chips too). Maybe you want to swap out your 3.91 for my stock 3.64? Even trade?

If you take the time from my video it is about 6,8s.

Then if you look at the next two different videos from stock cars with 3,15 diff it takes about 6,3s.

https://youtu.be/dp0rSpXYn4Y
https://youtu.be/CT3DyuQ1BZM

I actually measured those acceleration times several times. Measure yourself if you don't believe me.
Someone explain that please.

sorry for off topic

[mikae31]

I still have to say. I found two videos from youtube of cars with 3,91. I measured their acceleration and it is true that there is definitely something wrong in my car because i measured about one second better times than mine.

[adwebinc]

Maybe I'm off base, but would using the down pipes from the M73 850 solve the exhaust issue when using the M73 heads? Not a cheap option by any means, but just curious if that's the easiest bolt on option:

M73 Project - Exhaust.jpeg

Picking up an M73 for my swap at the end of this month. Anyone try this option for the exhaust downpipe solution for the swap?

[peake]

When doing an acceleration test, is it not a good idea to turn off the ASC or ASC+T. In my car it makes a difference?

[adwebinc]

I would swap the entire M73 engine with custom software, in fact that is what I am doing. No need to mess around with the heads or cams. I can walk you through later, a little busy currently packing up your diff

Got my M73 ordered. Still have't installed the diff as I plan to do the whole drive line at the same time.

Have you made any progress on your M73 swap? Would love to compare notes. How re you addressing the downpipes? What software are you running, etc.

Engine should be here within the next 5 business days. Need to get my engine stand built!

[merlin840]

I may be committing sacrilege by suggesting this and whilst i am not considering my csi for this this idea is starting to look promising especially since the whole car for this is now fairly cheap

Fit a Toyota century 5.0 V12 with vvti and 6spd auto. The 1GZ-FE produces over 400Nm at 1200 rpm, this could be what bmw should have done when they refreshed the M70 to the M73 or perhaps the S70 i think