Going built engine

[shushikiary]

People also forget that with DI you don't have to suck the fuel past the valves, so you typically see a 12% increase in available air mass for combustion... aka a straight up 12% power adder just from going DI..... The cooling affect that E85 has with DI as well compared to port injection is also insane... you don't get the same 105 octane rating from PI as you do DI with E85. It's still poor mans race gas on PI, just not as effective. I've seen papers that show that the cooling effect from E85 is nearly 30% more affective in DI than it is in PI.

The only reason to drop DI is because aftermarket control solutions for the injectors used in the N54 is limited, but I don't think the advantages of going aftermarket ECU are enough to convince me to go PI only. There's also the option of a syvecs and still keep the DI, so if I absolutely had do do aftermarket ECU, that's the route I'd take over going PI only. Simply too many advantages.

Heck, I want to build a dart block 427 with a 4 liter super charger for a mid engine superlight weight (brand name) SL-C, and it's tempting to go to an LT5 based head just for the direct injection especially since Holley is now releasing DI control options for their dominator.

 

[ShocknAwe]

DI is specifically designed to be used with high and very high compression engines, especially the turboed ones for emissions as well as it allows the performance of a NA motor when not in boost due to the high CR but it mitigates against detonation as the fuel is only injected when needed, this is done just before TDC is reached and can only be done directly and with high pressure. If you delete it you will have to drop the CR in your motor which will be costly and nonsensical in my humble opinion. I am building my N55 now as well and I’ve decided to do DI ONLY there are now soo many upgrade paths available for DI that I think it would be dumb to eliminate it and go backwards.

Agreed. DI only.

 

[Hydra Performance]

Unpopular opinion here, but our piezo injectors are actually one of the best things about this platform, assuming they're working properly of course. At 2700cc/min @ 200bar they allow me the luxury of placing the injection window wherever I want, whereas with the solenoid injectors on the S55 etc you need to run very lean lambdas so as not to run out of injection window completely unless you add a lot of meth () or an auxiliary PI kit.

Definite 10% (at least) power loss from deleting DI... I haven't spoken about this much yet, but I'm running an 11.4:1 CR on my motor, which makes >100bhp/L naturally aspirated THROUGH TURBO MANIFOLDS. Try doing that on a DI-deleted N54, I dare you

 

[wheela]

Unpopular opinion here, but our piezo injectors are actually one of the best things about this platform, assuming they're working properly of course. At 2700cc/min @ 200bar they allow me the luxury of placing the injection window wherever I want, whereas with the solenoid injectors on the S55 etc you need to run very lean lambdas so as not to run out of injection window completely unless you add a lot of meth () or an auxiliary PI kit.

Definite 10% (at least) power loss from deleting DI... I haven't spoken about this much yet, but I'm running an 11.4:1 CR on my motor, which makes >100bhp/L naturally aspirated THROUGH TURBO MANIFOLDS. Try doing that on a DI-deleted N54, I dare you

I Agree with you

A clarification about s55 - Nostrum now offers a higher flow option they call their stage 3 injector that they claim flows 20.2g/sec @ 100 bar (1212g/min). For pump gas assuming a density of about 0.71g/cc that works out to about 1707cc/min @100 bar vs. 2700cc/min @200 bar for the n54 solenoid injectors. So there's now some really good potential and tuning flexibility with the s55 style solenoid injectors as well

BMW N55-S55 Stage 3 DI injectors

Nostrum provides high horsepower fueling solutions to the automotive

nostrum.mybigcommerce.com

 

[Hydra Performance]

I Agree with you

A clarification about s55 - Nostrum now offers a higher flow option they call their stage 3 injector that they claim flows 20.2g/sec @ 100 bar (1212g/min). For pump gas assuming a density of about 0.71g/cc that works out to about 1707cc/min @100 bar vs. 2700cc/min @200 bar for the n54 solenoid injectors. So there's now some really good potential and tuning flexibility with the s55 style solenoid injectors as well

BMW N55-S55 Stage 3 DI injectors

Nostrum provides high horsepower fueling solutions to the automotive

nostrum.mybigcommerce.com

Piezo injectors, by virtue of being solid-state construction & variable in lift by nature, will always have finer control (and a wider tuning envelope) than a solenoid injector. They are technically superior, and are also used on the most advanced turbocharged production motor currently in existence. (the AMG M139) These Nostrum Stage 3 injectors might as well be redrilled stock injectors for all I know, certainly nothing special at all.

 

[ShocknAwe]

I Agree with you

A clarification about s55 - Nostrum now offers a higher flow option they call their stage 3 injector that they claim flows 20.2g/sec @ 100 bar (1212g/min). For pump gas assuming a density of about 0.71g/cc that works out to about 1707cc/min @100 bar vs. 2700cc/min @200 bar for the n54 solenoid injectors. So there's now some really good potential and tuning flexibility with the s55 style solenoid injectors as well

BMW N55-S55 Stage 3 DI injectors

Nostrum provides high horsepower fueling solutions to the automotive

nostrum.mybigcommerce.com

Sure. Is this an argument to switch to S55 injectors? Even if it could be done, I prefer reproducible parts, and OEM is basically always best. What if nostrum goes belly up? I like knowing I can send in my two sets of index 12 piezo injectors for cleaning and get most of them back good as new and they will work as BMW intended. I in no way believe they downgraded the injectors because they were somehow better, it was because the piezo injectors on the N54 were too expensive to warranty.

Apologies if this was an incoherent rant.

 

[wheela]

Sure. Is this an argument to switch to S55 injectors? Even if it could be done, I prefer reproducible parts, and OEM is basically always best. What if nostrum goes belly up? I like knowing I can send in my two sets of index 12 piezo injectors for cleaning and get most of them back good as new and they will work as BMW intended. I in no way believe they downgraded the injectors because they were somehow better, it was because the piezo injectors on the N54 were too expensive to warranty.

Apologies if this was an incoherent rant.

No worries I probably wasn't clear, I wasn't suggesting converting an n54 to run solenoid injectors, just illustrating that platform also has DI injectors with similar flow capabilities as the n54 injectors, as I interpreted the comment I was replying to as suggesting s55 injection window tuning limitations were due to limited capacity of the injectors requiring a longer duration injection window

Edit: I agree with your sentiment of liking to stick with oem injectors. That's a big reason I'm not keen on adding PI or switching to PI-only.

 

[wheela]

Piezo injectors, by virtue of being solid-state construction & variable in lift by nature, will always have finer control (and a wider tuning envelope) than a solenoid injector. They are technically superior, and are also used on the most advanced turbocharged production motor currently in existence. (the AMG M139) These Nostrum Stage 3 injectors might as well be redrilled stock injectors for all I know, certainly nothing special at all.

Fair enough. I'm not in a position to argue which injector type is technically better, but I know s55 (and n55) guys seem to be getting good results DI-only using these injectors, so I thought it worth mentioning