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Old 06-05-2006, 09:24 AM   #1
jblaine
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Default Closed loop fuel and higher RPMs

I must be missing something.

Why is this so taboo?

- Phil recommends max RPM set to where you'll see decent boost.

- The maps I have seen all have the 'Closed Loop Limit' map dropping down to very high vacuum levels by 3500RPM or so.

What's the problem with CL working at 5000RPM and 350mmHg, for instance?
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Old 06-05-2006, 10:33 AM   #2
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Sorry, this is relating to the Hydra. I always forget this forum isn't JUST for Hydra.
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Old 06-05-2006, 12:55 PM   #3
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I've done this to tune the off boost area, or low boost areas. I've set it from 1500 to 7000 RPM after the car is warmed up and then auto-tuned and smoothed. In fact I consider it the only way to get data on even a fraction of those load sites.

I still don't auto-tune in the high boost areas, especially near peak boost for the turbo.

I did use auto-tune up to 17 psi for a 2.65L engine with a GT30R turbo because the whole base map was off due to the change in displacement. The peak boost on pump gas was 22 psi, so I never got near that with the auto-tune. I just worked my way up to 17 psi in 1-2 psi increments. You really have to know what sort of AFRs the motor can handle to do this without harm. I used EGT to set timing with at target of 850-900C.
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Old 06-05-2006, 02:54 PM   #4
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Where is/was your EGT sensor located? Mine is located at the collector, so is that 850-900C just before the turbo, or right at the exhaust port?
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Old 06-05-2006, 05:52 PM   #5
Element Tuning
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Quote:
Originally Posted by jblaine
I must be missing something.

Why is this so taboo?

- Phil recommends max RPM set to where you'll see decent boost.

- The maps I have seen all have the 'Closed Loop Limit' map dropping down to very high vacuum levels by 3500RPM or so.

What's the problem with CL working at 5000RPM and 350mmHg, for instance?
Most of the newer maps don’t have a “Closed Loop Limit” of less than 357 mm/hg until after 6400 rpm. The “Closed Loop Limit” map only applies when using “14.7 U/hego” or 14.7 WB U/hego” and only under vacuum. This means that until you get to >6500 rpm you will only have 14.7 feedback to 357 mm/hg and if it’s less than that 356 it will run in “open loop.”

Now if you are running “Wideband Target Table” the only limitations are RPM based (not vacuum and rpm). The reason for limiting “closed loop” feedback when not tuning is in case of an oxygen sensor failure and for no other reason. When tuning and monitoring there is no reason not to use “Autotune” for the entire boost and or RPM range but under daily driving situations when you are not monitoring you’ll want the EMS to switch to “open loop” fueling once peak boost is realized. If the oxygen sensor fails then incorrect fueling will not occur under peak boost situations potentially saving your engine.

The range used for “Wideband Target Table” will vary depending on the turbocharger so for instance a 35R car can run up to 4200 rpm under closed loop while a VF30 car should be limited to about 3500 rpm. This will deliver optimal fuel economy, consistency in spoolup, but also safety. When using “14.7 U/Hego” your RPM limits can be higher because they are defined and only utilized under vacuum and not also under boost such as when using “Wideband Target Table.”

Thanks,
Phil
http://www.elementtuning.com
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Old 06-05-2006, 06:33 PM   #6
jblaine
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Quote:
Originally Posted by Element Tuning
Most of the newer maps don’t have a “Closed Loop Limit” of less than 357 mm/hg until after 6400 rpm. The “Closed Loop Limit” map only applies when using “14.7 U/hego” or 14.7 WB U/hego” and only under vacuum. This means that until you get to >6500 rpm you will only have 14.7 feedback to 357 mm/hg and if it’s less than that 356 it will run in “open loop.”
Okay. My current CL limit map must still based off of your old very rough 420cc map then. It is 3mmHg from 0RPM to 2400RPM, then 765mmHg from there on out (essentially half worthless for my cruise RPMs).

Quote:
Now if you are running “Wideband Target Table” the only limitations are RPM based (not vacuum and rpm). The reason for limiting “closed loop” feedback when not tuning is in case of an oxygen sensor failure and for no other reason. When tuning and monitoring there is no reason not to use “Autotune” for the entire boost and or RPM range but under daily driving situations when you are not monitoring you’ll want the EMS to switch to “open loop” fueling once peak boost is realized. If the oxygen sensor fails then incorrect fueling will not occur under peak boost situations potentially saving your engine.
Gotcha.

Quote:
When using “14.7 U/Hego” your RPM limits can be higher because they are defined and only utilized under vacuum and not also under boost such as when using “Wideband Target Table.”
Exactly the info I was looking for.
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Old 06-05-2006, 08:20 PM   #7
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Glad I could help.

Thanks,
Phil
www.elementtuning.com
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