Smoothness of the N52 engine compared to others?

[Obioban]

Originally Posted by Kgolf31

Interesting. Active Autowerke told me this:



and this




Seems like we need to get to the end of this.




With 0.7 compression difference, you're not talking about a huge HP swing here. Maybe 5-10 HP at most.

With that being said, I still think there are huge gains out there for a properly tuned N51. Just gotta find them (gotta talk to Evolve and see if they have tested a N51 yet)

I'm a huge Evolve proponent (on all my cars), but they may not be the best go to option in this case-- I don't believe they have the N51 in Europe, correct?

[Kgolf31]

Originally Posted by Obioban

I'm a huge Evolve proponent (on all my cars), but they may not be the best go to option in this case-- I don't believe they have the N51 in Europe, correct?

Correct. I've talked to them and they haven't worked on a N51

[chris82]

Originally Posted by Kgolf31

Interesting.

With 0.7 compression difference, you're not talking about a huge HP swing here. Maybe 5-10 HP at most.

can you provide a little more info as to why you say this?

[Obioban]

That strikes me as an underestimate to the effect of the compression difference. I'm planning to bump my s54 by .5 when i rebuild it and expect to get ~15-20 wheel from it.

[Suprgnat]

Great write up on the effects of compression here: http://www.popularhotrodding.com/tec...on_ratio_tech/

Expect <2.5% difference.

[Obioban]

Originally Posted by Suprgnat

Great write up on the effects of compression here: http://www.popularhotrodding.com/tec...on_ratio_tech/

Expect <2.5% difference.

Uh oh... My engine has likely already failed (11.5:1) and the s65 and s85 probably can't drive off the assembly line (12:1)!

Conclusions
So if you follow all the rules here what is the payback? With current 93-octane fuel, it is possible to run as much as 11.2:1, but the safety margin is small. At this level you can be slave to the weather. If it's hot and humid, the water content suppresses detonation to about the same degree as the increase in detonation from the temperature increase. If it's plain hot, such as a 118-degree day in Tucson, that 11.2:1 and 93 octane won't make it. The answer here is to back off the CR half a point (not good for night time racing) or utilize a knock sensing ignition retard such as the sophisticated J&S unit.

[Obioban]

That article does make me happy with my plan for my s54: cams, thermal coatings, head work, and compression bump. Sounds like they agree that they're complementary mods. Hoping for 40-50 whp more total

[Suprgnat]

Originally Posted by Obioban

Uh oh... My engine has likely already failed (11.5:1) and the s65 and s85 probably can't drive off the assembly line (12:1)!

Yes, you have a knock sensor that backs off the timing.

[Obioban]

Originally Posted by Suprgnat

Yes, you have a knock sensor that backs off the timing.

Indeed. My thought is that BMW designed it to be run at 11.5:1 on 91 octane so 12:1 should be well matched to the 93 octane that I dd. In the rare instance I get stuck with 91, the car can notice via knock sensors and retard timing (as the car can safely run 87 Octane stock in a pinch). What I should really be losing is the ability to run 87 safely in a pinch.

[Suprgnat]

Originally Posted by Obioban

Indeed. My thought is that BMW designed it to be run at 11.5:1 on 91 octane so 12:1 should be well matched to the 93 octane that I dd. In the rare instance I get stuck with 91, the car can notice via knock sensors and retard timing (as the car can safely run 87 Octane stock in a pinch). What I should really be losing is the ability to run 87 safely in a pinch.

I would also assume that it can utilize the full CR under optimum conditions. And certainly the combination of modern automotive computers and combustion chamber/valve design improves things (this is, after all, an article about old-school engines). My main reason for pointing out this article had to do strictly with the effects of compression, i.e. Otto cycle thermal efficiency vs. compression.

[jc5988]

i had ess tune on my n51 disa w very good result. dyno are very similar to n52 disa w tune, maybe just 4-5whp less w all identical add on.

apparently n51 w disa has been tuned down at factory to match smooth torque of 230hp n52. otherwise it will be and feel faster especially at lower rpm around 2750.

[Kgolf31]

Originally Posted by jc5988

i had ess tune on my n51 disa w very good result. dyno are very similar to n52 disa w tune, maybe just 4-5whp less w all identical add on.

apparently n51 w disa has been tuned down at factory to match smooth torque of 230hp n52. otherwise it will be and feel faster especially at lower rpm around 2750.

I never saw on their web shop a product for the 128i

Did you contact them directly? Any dyno of your tune?

[jc5988]

Originally Posted by Kgolf31

I never saw on their web shop a product for the 128i

Did you contact them directly? Any dyno of your tune?

i had post some review w dyno, just check my profile.

tune is really same with 128i, im the first N51 ESS had worked on, so the dyno i have its really early beta, we made many revision to the tune since then, but those guy really nailed most of it the very first time. revision smooth out the throttle and torque limiter setting a bit.