[Syztra]

Anyone know if the m340i has the same transmission. My transmission is starting to go and I know people usually go for the HP70, but nowadays they’re all too high of mileage and hard to locate so their not worth the swap. I know upgraded pure transmissions are an option but again, 7k more expensive than an M340i auto trans

[morritse]

Same torque rating

[J555]

M340i has 8HP51, while F 340i has 8HP50z. So not the same, but don't know, if you can directly swap or not.

[Skyhigh]

https://www.fcpeuro.com/blog/zf-8-sp...cs-maintenance

8HP50 (Gen 2) Gear Ratios:

1st gear 5.00
2nd gear 3.20
3rd gear 2.14
4th gear 1.72
5th gear 1.31
6th gear 1.00
7th gear 0.82
8th gear 0.64
Reverse 3.46

Fluid Capacity: Roughly 6 liters
Fluid Type: ZF LifeguardFluid 8 or equivalent
Torque Limit: 500 NM (369 lb-ft)

8HP51 (Gen 3) Gear Ratios:

1st gear 5.25
2nd gear 3.36
3rd gear 2.17
4th gear 1.72
5th gear 1.32
6th gear 1.00
7th gear 0.82
8th gear 0.64
Reverse 3.71

Fluid Capacity: Roughly 6 liters
Fluid Type: ZF LifeguardFluid 8 or equivalent
Torque Limit: 500 NM (369 lb-ft)

[co_440i]

369 lb-ft is the torque limit? That can’t be right. You’ll clear that on Stage 1 tune…

[Skyhigh]

The trans is designed and set up for stock vehicles, not for aftermarket tuning.

[morritse]

Originally Posted by co_440i

369 lb-ft is the torque limit? That can’t be right. You’ll clear that on Stage 1 tune…

That's like saying 320hp is the HP limit for the b58

[Skyhigh]

Almost correct, the stock limit for B58 Gen 1 is 360 PS and 500Nm.
Which is also why the transmission never needed more than 500Nm torque limit.

Anything beyond that is called “aftermarket tuning” and was never an official design requirement for either the engine or the trans, for the given application.

[co_440i]

Right. What I’m saying is that it’s clearly *actually* designed for far more than that given how much we all push through it without any trouble.

[Skyhigh]

Every mechanical part or device is designed and manufactured with a margin of safety (in aviation for example it is a min factor of 1,5). What tuning does is utilising that extra margin which in turn reduces the safety/reliability reserves.
So yes, they are “actually” designed for more, but there is no free lunch - that’s the safety net. Which is why the software torque limit is set where it needs to be for the intended application - 500 Nm.

In some cases parts are indeed also designed to be stronger for a different application (economy of scale).

[Oksamit78]

Originally Posted by Skyhigh

Every mechanical part or device is designed and manufactured with a margin of safety (in aviation for example it is a min factor of 1,5). What tuning does is utilizing that extra margin which in turn reduces the safety/reliability reserves.
So yes, they are “actually” designed for more, but there is no free lunch - that’s the safety net. Which is why the software torque limit is set where it needs to be for the intended application - 500 Nm.

In some cases parts are indeed also designed to be stronger for a different application (economy of scale).

Then, I wonder how Dinan Stage 1/2/3 engine tunes are honored, installed and warranted by BMW dealers...

[Skyhigh]

They are not. Prove me wrong - show me an evidence where BMW in writing commits to retaining the BMW factory warranty with a Dinan (or another third party) tuning.
(Why on earth would they?)
To the best of my knowledge Dinan offers their own warranty which would cover the cost if BMW refuse to (which they absolutely will, on a tuned engine or engine-related components all the way down to the drive-train. Why would they cover the risk and cost of someone else's business.

[Skyhigh]

Originally Posted by co_440i

369 lb-ft is the torque limit? That can’t be right. You’ll clear that on Stage 1 tune…

Originally Posted by morritse

That's like saying 320hp is the HP limit for the b58

Originally Posted by Oksamit78

Then, I wonder how Dinan Stage 1/2/3 engine tunes are honored, installed and warranted by BMW dealers...

Just for the sake of the argument, I remembered something - this comes straight from BMW's MPPSK technical specification / brochure. It clearly shows BMW's official position on the topic (which is no surprise at all, as they need to ensure reliability margins and no increase in maintenance or warranty cost):

[Oksamit78]

Originally Posted by Skyhigh

They are not. Prove me wrong - show me an evidence where BMW in writing commits to retaining the BMW factory warranty with a Dinan (or another third party) tuning.
(Why on earth would they?)
To the best of my knowledge Dinan offers their own warranty which would cover the cost if BMW refuse to (which they absolutely will, on a tuned engine or engine-related components all the way down to the drive-train. Why would they cover the risk and cost of someone else's business.

Yes, you are correct, it is Dinan waranty, not BMW (matching either BMW new car warranty or 2 years for cars no longer covered by oem new car warranty). That's in USA and Canada, not sure how it is in Europe.. I made an error in my statement, because in my area, the actual BMW dealer IS the Dinan Authorized installer (2-in-1).

[Skyhigh]

AC Schnitzer had something similar in Europe (Dinan is not very known here).
This as you understand is not the same as BMW warranting tuned vehicles It is just ACS/Dinan signing an agreement with the BMW-authorised workshops network (and paying a kick-back to BMW for enabling the non-conflict-of-interest synergy)