Alfa Romeo Giulia Forum banner
41 - 60 of 64 Posts

·
Registered
2019 Stelvio Sport with trailer hitch
Joined
·
3,263 Posts
Admittingly, I am not an expert on the Alfa's ECU but that would vary from most all other modern ECU behavior that I am familiar with.
Open loop is used for medium to hard throttle acceleration, cold idle and deceleration. Closed loop for cruising, low throttle positions and other low-load scenarios where fuel efficiency is paramount.

That's why cars run a richer AFR than stoich (which 14.7:1 on gas) when you see them on the dyno. NA cars like 12ish and boosted cars may go richer at say 11-11.5:1 They don't use the O2's to correct fueling to get back to stoich. They run open loop and look up the fueling in a table. At this point, the O2's are just reporting the news, not actually feeding info back to the ECU to adjust fueling.

This is why you have to retune for mods because 1. when running in closed loop, the short term and long term fuel trims will be out (if you are familiar with tuning software, you can view the fueling in various "cells" which show where it is lean or rich) and 2. the pre-determined tables used for wide open throttle may no longer have proper values due to changes in airflow ie. new exhaust. Additionally, for turbo cars, boost pressure can be affected by hardware changes. If the table values are too far out, a rich or lean condition can occur which the ECU wont correct for, causing issues.

Again, not saying there are ANY issues with the Fabspeed parts or anything wrong with OP's car. Just some thoughts...
That's not accurate

The only semi modern ecu ive seen run open loop under load are some honda from 2000.

Bosch, simos, mm etc etc have been running closed loop under any load situation (only open loop during cold starts) since the early 2000s. All Audi, all BMW, all VAG, all MB, etc etc etc.

These cars run 11:1 or richer under wot simply because of enrichment tables from cat temperature correction.

They otherwise target 14.7:1 for the most part with DI for the past 15 years or so and nowadays will target even 15:1 or leaner. Thats part throttle off boost though because as soon as the cats pass various temp thresholds which they always will under WOT the ECU goes to EGT enrichment tables.

o2 sensors are providing feedback to make sure it happens.

That's why you can run a piggyback under WOT and still see 11:1 AFR. If it was open loop you'd be out of luck.

Here's the car running 5lbs more boost down low, 2 up top and no change to fueling programming but still maintains identical afr as stock curve because of closed loop. Been that way going back to bosch MED in 2000

110218
 

·
Registered
Joined
·
154 Posts
Late model GM's run open loop under WOT and switch as I described. They also have PE (power enrichment) tables for WOT but the O2's are narrowband and don't work well when not at 1 Lambda. So, they basically shut off at WOT, entering open loop and use the fuel tables along with PE to get the engine to .85 Lambda or whatever the target is.

Maybe euro cars have wideband O2's so they could theoretically work as you describe, since the O2's would then be much more accurate at differing AFR\lambdas and could correct fueling\fuel trims. Hence my initial statement, I don't know about the specifics of the Alfa ECU, more basing my opinion on domestic experience.

I am not sure I understand your comment on the piggyback. Isn't the idea that the box manipulates the sensor data to trick the ECU into changing fueling? I assumed it just messes with MAP sensor inputs. Not sure why that means it cant be open loop...
 

·
Registered
2019 Stelvio Sport with trailer hitch
Joined
·
3,263 Posts
Late model GM's run open loop under WOT and switch as I described. They also have PE (power enrichment) tables for WOT but the O2's are narrowband and don't work well when not at 1 Lambda. So, they basically shut off at WOT, entering open loop and use the fuel tables along with PE to get the engine to .85 Lambda or whatever the target is.

Maybe euro cars have wideband O2's so they could theoretically work as you describe, since the O2's would then be much more accurate at differing AFR\lambdas and could correct fueling\fuel trims. Hence my initial statement, I don't know about the specifics of the Alfa ECU, more basing my opinion on domestic experience.

I am not sure I understand your comment on the piggyback. Isn't the idea that the box manipulates the sensor data to trick the ECU into changing fueling? I assumed it just messes with MAP sensor inputs. Not sure why that means it cant be open loop...
GM is a different story. Yes i had to add wideband and change tuning strategy on mine when i added tvs1900.

But euro cars have been using closed loop with wideband for 20 years.

For piggyback all it tricks is map sensor into making more boost. The ecu actually sees less boost due to the signal spoofing....so it tries to make more.

If you added 50tq and 30hp via boost on open loop you'd be in trouble. You wouldn't maintain afr.

but since our cars run closed loop pretty much 100 percent of time (just not cold start) you can add boost and the factory wideband and closed loop keeps that same 11:1 afr happening as you can see.
 

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #44 ·
So I got to measure dB today. I'll have the video posted in a few days, but I measured at exhaust height, 20 inches away and hit a peak of 118dB
Here's the video. It really does sound so good.

Apologies for my poor editing skills

For reference, the gt350 next to me hit 124 dBs

 

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #46 ·
  • Like
Reactions: Fabspeed Motorsport

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #48 ·
My heart stopped for a second when he revved the cold engine past 7k rpm in the video...
All in the name of a good sound clip lol

When I'm stuck in doors, a few repeats of these clips and I'm content enough
 
  • Like
Reactions: Fabspeed Motorsport

·
Registered
Giulia Quadrifoglio MY18
Joined
·
241 Posts
I'd love to hear HJS 200 cell downpipes (Redstar or HFC) with completely stock exhaust in person to make a conclusion if this mod is for me or not... But probably never will find anyone, especially where I live.
 

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #51 · (Edited)
Sounds perfect!!! How much louder vs stock is it on N mode? And at cold start up?
I'm not sure about N but I run with valves always open. But with valves closed, it's much quieter.

I'd love to hear HJS 200 cell downpipes (Redstar or HFC) with completely stock exhaust in person to make a conclusion if this mod is for me or not... But probably never will find anyone, especially where I live.
I'm stock axel back only. But all I can say is that if you're looking for more sound; HFC is the way to go. You won't regret it
 
  • Like
Reactions: qvfan

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #53 ·

·
Registered
Joined
·
127 Posts
I'm not sure about N but I run with valves always open. But with valves closed, it's much quieter.
Thank you for responding. Valves closed is what I meant, be it A/N/ or Dynamic pre 2020 iirc. I'm looking for some extra sound, but nothing obnoxious like the hemi/hellcat guys. How is the loudness at coldstart vs stock?
 

·
Registered
2019 QV Rosso Comp
Joined
·
1,182 Posts
I'm not sure about N but I run with valves always open. But with valves closed, it's much quieter.


I'm stock axel back only. But all I can say is that if you're looking for more sound; HFC is the way to go. You won't regret it
I feel like this would be a great mod. Is there a "good but bargain" option? Like, if i want a little more flow and a little more sound, which pipe set should I grab?
 

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #56 ·
Thank you for responding. Valves closed is what I meant, be it A/N/ or Dynamic pre 2020 iirc. I'm looking for some extra sound, but nothing obnoxious like the hemi/hellcat guys. How is the loudness at coldstart vs stock?
Cold start is LOUD! But after 30 seconds it dies down.
This can be obnoxious but it depends how you drive. Put it in A/N and auto, never go past 25% throttle and it'll be quiet even with valves open. Put it in d/r, or really any mode with manual, and give it the beans and if you time the upshift or downshift right, and you have the right acoustics then watch out lol


I feel like this would be a great mod. Is there a "good but bargain" option? Like, if i want a little more flow and a little more sound, which pipe set should I grab?
You mean if you want HFC but not fabspeed because of the $$$$? Well you can get other HFCs that are cheaper and/or more cels meaning more restriction but some of those require a tune. Fabspeed's don't which was a huge plus for me, and their proximity to me. Ideal race has cheaper gesi ones but I know of a forum member who installed them and got cels bc he wasn't tuned. Alfissimo offered Redstar hfc but that's on hold due to the war, but he does have supersprint HFC, although I believe they are the same price as fabspeed. If you want a little more sound for not much money however, then for under 1k installed, you could do a resonator delete to either an X or straight pipe.
 
  • Like
Reactions: qvfan and migliori

·
Registered
Joined
·
127 Posts
Cold start is LOUD! But after 30 seconds it dies down.
This can be obnoxious but it depends how you drive. Put it in A/N and auto, never go past 25% throttle and it'll be quiet even with valves open. Put it in d/r, or really any mode with manual, and give it the beans and if you time the upshift or downshift right, and you have the right acoustics then watch out lol
I wonder how much the loudness at cold start can be attributed to your HFC vs the x-pipe you have? I managed to get my hands on a Redstar 200 cell HJS heat shielded. I just plan to run the HFC + everything else stock. Cant wait to get it installed, for the meantime, I just watch your videos on loop.
 

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #58 ·
I wonder how much the loudness at cold start can be attributed to your HFC vs the x-pipe you have? I managed to get my hands on a Redstar 200 cell HJS heat shielded. I just plan to run the HFC + everything else stock. Cant wait to get it installed, for the meantime, I just watch your videos on loop.
A part of me always wondered if the x pipe made it louder or quieter. I think from a dB perspective it did, but as it made it slightly deeper; I think it subjectively sounds quieter

You can see my comparison here QV X-Pipe Exhuast Comparison Video

Once you have yours installed; if you take a dB reading; I can try and take a similar measure to compare with and without X/filter although I doubt filter adds sound
 
  • Like
Reactions: qvfan

·
Registered
Joined
·
127 Posts
A part of me always wondered if the x pipe made it louder or quieter. I think from a dB perspective it did, but as it made it slightly deeper; I think it subjectively sounds quieter

You can see my comparison here QV X-Pipe Exhuast Comparison Video

Once you have yours installed; if you take a dB reading; I can try and take a similar measure to compare with and without X/filter although I doubt filter adds sound
Thanks! Just saw both videos stock vs x-pipe. X-pipe sounds about the same in volume as stock. However much lower deep tone. Could be louder, just the pitch of the tone may not make it seem as loud versus say another exhaust with a high pitch raspiness.
 

·
Registered
2018 Vulcano Black Giulia Quadrifoglio
Joined
·
6,083 Posts
Discussion Starter · #60 ·
Thanks! Just saw both videos stock vs x-pipe. X-pipe sounds about the same in volume as stock. However much lower deep tone. Could be louder, just the pitch of the tone may not make it seem as loud versus say another exhaust with a high pitch raspiness.
That's exactly what joecab said!
 
  • Like
Reactions: qvfan
41 - 60 of 64 Posts
Top