I’ve been doing quite a bit of research into the two different versions of b58 that the x3m40i got, and the alleged difference in power potential. It seems to be that the general understanding is that the b58tu for 2020+ not only has more power out the box, but also has more potential due to hardware changes.

However, all of my reading seems to indicate that the only hardware changes which would have an affect on power are fueling (hpfp and injectors), and a slightly lighter crank. All the other changes seem to be strictly emissions or cost related (revised cooling circuit, single timing chain vs two).

I haven’t found any documentation or proof as to anything else eg different turbo, camshaft, compression, whatever.

So out of the box the 2020+ x3m40i is quicker, but that appears simply because of more fuel and boost. Does anyone have concrete evidence of mechanical changes that give the b58tu a definite advantage power-wise?

Ps I have seen some talk that the 2021 Supra b58tu uses different pistons and slightly lower compression, but those changes are Toyota-specific. I’m also aware that some BMW models got the lower output version of the B58tu which used a turbo manifold that is integrated into the cylinder head, the benefit being cost and emissions related.

The B58TU engine has a lot of changes compared to the B58 that may lead to a higher potential. You have already pointed out most of the changes but here are some that I feel are important for B58TU's potential.

1. Different cylinder bore honing process
2. From 2-part timing chain to 1-part timing chain so the intermediate shaft is no longer needed. I suspect there will be less power loss in the 1-part timing chain setup.
3. Split cooling
4. 350 bar direct injectors with better spraying pattern
5. Lighter crankshaft which increases performance by 13 hp and 36 lb-ft

The technical document covers the changes in detail.

mattsheng wrote

The B58TU engine has a lot of changes compared to the B58 that may lead to a higher potential. You have already pointed out most of the changes but here are some that I feel are important for B58TU's potential.

1. Different cylinder bore honing process
2. From 2-part timing chain to 1-part timing chain so the intermediate shaft is no longer needed. I suspect there will be less power loss in the 1-part timing chain setup.
3. Split cooling
4. 350 bar direct injectors with better spraying pattern
5. Lighter crankshaft which increases performance by 13 hp and 36 lb-ft

The technical document covers the changes in detail.

Good summary of the changes. I’ve seen that document, and I notice it doesn’t mention any specific lightening of the crankshaft itself. Where did you get that info and the power figures?

335is-dct wrote

Good summary of the changes. I’ve seen that document, and I notice it doesn’t mention any specific lightening of the crankshaft itself. Where did you get that info and the power figures?

I quoted the performance increase from page 8 of the technical document. It didn't specify the amount of weight saving though... I compared the mid-output variant of B58 (B58B30M0) and B58TU (B58B30M1) and found that they have identical bore/stroke (82/94.6) and compression ratio (11:1).

I also checked the part catalog and found that the connecting rods are identical for the B58 and B58TU but the pistons have different part numbers. But since the part number includes 1) piston, 2) roll pin, and 3) piston rings, who knows what has been changed...

Part diagram for 2019 M40i: https://parts.bmwnorthwest.com/a/BMW_2019_X3-M40iX/_51507_6704751/Crankshaft-connectrod-with-pistons/11_6363.html

Part diagram for 2020 M40i:
https://parts.bmwnorthwest.com/a/BMW_2020_X3-M40iX/_51507_8231941/Crankshaft-connectrod-with-pistons/11_7974.html

mattsheng wrote

I quoted the performance increase from page 8 of the technical document. It didn't specify the amount of weight saving though... I compared the mid-output variant of B58 (B58B30M0) and B58TU (B58B30M1) and found that they have identical bore/stroke (82/94.6) and compression ratio (11:1).

I also checked the part catalog and found that the connecting rods are identical for the B58 and B58TU but the pistons have different part numbers. But since the part number includes 1) piston, 2) roll pin, and 3) piston rings, who knows what has been changed...

Part diagram for 2019 M40i: https://parts.bmwnorthwest.com/a/BMW_2019_X3-M40iX/_51507_6704751/Crankshaft-connectrod-with-pistons/11_6363.html

Part diagram for 2020 M40i:
https://parts.bmwnorthwest.com/a/BMW_2020_X3-M40iX/_51507_8231941/Crankshaft-connectrod-with-pistons/11_7974.html

Great catch. Compression has remained the same so I wonder what, if anything was changed to the piston assembly. Maybe it was revised to match the new cylinder hone?

335is-dct wrote

Great catch. Compression has remained the same so I wonder what, if anything was changed to the piston assembly. Maybe it was revised to match the new cylinder hone?

I would think so but no evidence to back it up hahaa

The air intake pipe and paper filter size is different.
Its a regular tube right but then why was it changed? Because something was upgraded.
The B58TU is also 6 port on the manifold vs 2. Thats a difference there also.

This is my personal direct quote. Performance wise a tuned B58 finishes where a stock B58TU starts in performance #s.

suby01 wrote

The air intake pipe and paper filter size is different.
Its a regular tube right but then why was it changed? Because something was upgraded.
The B58TU is also 6 port on the manifold vs 2. Thats a difference there also.

This is my personal direct quote. Performance wise a tuned B58 finishes where a stock B58TU starts in performance #s.

You are incorrect about 6 exhaust ports vs 2. The b58 uses 6. A low output version of the b58tu features the integrated manifold with two ports.

The b58tu definitely starts out ahead but other than a few minor updates that have been discussed, I don’t see anything that would put it significantly ahead once mods begin.

Same turbo, same manifold, same compression, same camshafts, same intake manifold. Different hpfp and injectors, lighter timing chain assembly, different cylinder hone technique that may reduce friction?… that seems to be it in terms of non-emissions related changes.

7 out of the 10 fastest x3m40’s on dragy in the 0-60 are gen 1 b58 cars:confused2

335is-dct wrote

7 out of the 10 fastest x3m40’s on dragy in the 0-60 are gen 1 b58 cars:confused2

What is the fastest time for 0-60 or 1/4 for a gen 1 X3 M40i?

suby01 wrote

What is the fastest time for 0-60 or 1/4 for a gen 1 X3 M40i?

I mean, 8 out of 10 of the fastest 1/4 mile cars on there are gen 1. That’s really anecdotal more than anything though. I’m more interested in fact based discussed on physical differences between the motors.