E85/ Eflex and its affect on avcs

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Re: E85/ Eflex and its affect on avcs

Postby dr20t » Tue Mar 24, 2015 6:50 pm

So you're tuning all the 1mb ecu's real time now?
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Re: E85/ Eflex and its affect on avcs

Postby dr20t » Sun Mar 06, 2016 7:09 pm

Reviving this thread from the dead

I have some very interesting findings that I will share as soon as I get a chance

Keen to hear people's thoughts on avcs tuning / theory

Mick
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Re: E85/ Eflex and its affect on avcs

Postby vaccine » Mon Mar 07, 2016 2:42 pm

my last avcs (intake only) vehicle i tuned was more rudimentary and a good 10 years ago now. I ran say 5 degree's or timing, then 10, 15, 20 etc etc and looked at the AFR's going rich or lean and then selected the timing value that was just before it went changed the AFR to lean. Took ages and was annoying, but got there in the end. pretty sure there would be much easier ways to find the best VE using maths/spreadsheets but hey i had the time back then. Setup was a vf34/P20 in a bugSTi that had insane mid-range, ie 24psi by late 2000's.

was much easier tuning my 2litre/then forged 2.2 with non-avcs style LGT e-tune bigport heads. full boost with TD06/20g with a 71mm compressor was around 35-3200rpm and 28psi.. hehe
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Re: E85/ Eflex and its affect on avcs

Postby dr20t » Wed Mar 30, 2016 8:19 pm

Good input Dave.

Before sharing my findings i would like to put something out there. I've come to a conclusion and its a big call but I'm willing to back it - the majority of tuners out there have no idea when it comes to optimizing variable valve timing. I'm not just talking about Subaru avcs here, either. Either this is because they don't have the time to spend on each setup, or of greater concern, don't actually understand the full extent of what's going on.

Not saying I have all the answers to avcs, but I think i understand its impacts and application to a fair degree.

Anyway - enough venting. I'm willing to help anyone who has queries relating to avcs, but essentially, there is alot to consider with avcs. Think of it as a Volumetric Efficiency dial, which needs to work in harmony with the rest of the setup. Even a change as slight as different spark plug gap or heat range can change the avcs tuning requirements.

Long story short, I love avcs. Dual is better than single, as it allows complete control over both cam opening and closing points, with many possible outcomes.

My tip - go back to basics of what an engine's function is. Pump air in and out as efficiently as possible. The limitations imposed by physics will be a good guide depending on the setup.

There are two essential pieces of equipment to optimise avcs - a wideband 02 sensor is one. And an ability to measure egt or at least gauge when it goes over a certain threshold. I don't have an egt gauge, but was able to use a rom hack to flash my cel once egt reached a set temperature. This helped alot.

If we're talking Ideal world, a pre turbo exhaust back pressure measurement should be taken too. But in the absence of knowing the preturbo back pressure, it will become pretty clear pretty quickly if your inlet to exhaust pressure ratio is out of whack or exhaust pressure exceeds inlet pressure (absolute).

I believe I have optimized my avcs settings on my engine, after alot of time invested. I have also discovered in this process the flexibility of the dual avcs system in the grb 207. I'm reaching 28psi on my gtx3076 by 3800rpm when hot and 4000rpm cold. That gives me a pretty wide powerband with a 8500rpm redline.

To answer the original question I posted in this thread - e85 absolutely makes a difference to avcs' impact, however this does not preclude a good avcs setup with 98 ron fuel. The knock resistance of e85 makes a difference to the in cylinder pressures able to be reached, and in a turbo car, the ability to therefore spool a turbo more efficiently.

Happy to be critiqued or questioned on anything I've said here

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Re: E85/ Eflex and its affect on avcs

Postby bigBADbenny » Wed Mar 30, 2016 8:59 pm

How would you summarise Subarus intent as regards avcs utilisation versus the Dr20t intent?
Is it essentially an emissions vs spool question or can we (you) utilise the system to satisfy both outcomes?

Quad CHT gauges & logging on the ej207 info page on nasioc? :good:
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Re: E85/ Eflex and its affect on avcs

Postby dr20t » Wed Mar 30, 2016 9:20 pm

I believe Subaru's intent was for both low rpm torque maximization and emissions control.

I also believe we can achieve a good balance with a modified tune. Obviously e85 helps with emissions and therefore less emphasis on emission control in the avcs tuning.
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Re: E85/ Eflex and its affect on avcs

Postby bigBADbenny » Thu Mar 31, 2016 11:59 am

Iirc from reading crystalimprezav's posts, exhaust gas back pressure is another key area for optimising this type of tuning.
I'm planning 4 channel CHT, TIT, EGT and EGBP for my built engine when it happens. :P
I recently met a jeweler who has the tiny lpg/oxy torch suitable for silver soldering temp sensor thermocouples to spark plug washers to allow for CHT trend logging...
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Re: E85/ Eflex and its affect on avcs

Postby dr20t » Thu Mar 31, 2016 12:50 pm

All those things are absolutely going to help Optimise the tune (and not just for avcs)

Ebp is the most critical consideration for avcs tuning.
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Re: E85/ Eflex and its affect on avcs

Postby bigBADbenny » Thu Mar 31, 2016 4:57 pm

I'll have to research how to implement it, as soon I'll be able to weld it in ;)

As regards sensors and logging, 4 channel logging eg per cyl is great, but is hardly practical esp as regards AFR on each of the headers, too sensitive to placement, too big, short life, too costly. So the next best approach is possibly the aforementioned CHT trending via the base seal of the spark plugs, then EGT on each header runner. Then dealing with all the data is a headache. I have some potential solutions of course...

Has the exhaust scavenge effect of exh avcs been useful in practice?
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Re: E85/ Eflex and its affect on avcs

Postby KiDo_Tuning » Sat Apr 02, 2016 3:34 pm

dr20t wrote:There are two essential pieces of equipment to optimise avcs - a wideband 02 sensor is one. And an ability to measure egt or at least gauge when it goes over a certain threshold. I don't have an egt gauge, but was able to use a rom hack to flash my cel once egt reached a set temperature. This helped alot.

If we're talking Ideal world, a pre turbo exhaust back pressure measurement should be taken too. But in the absence of knowing the preturbo back pressure, it will become pretty clear pretty quickly if your inlet to exhaust pressure ratio is out of whack or exhaust pressure exceeds inlet pressure (absolute).

Mick


EGT in yours is actually off the O2 heater element resistance. No EGT sensor but the EGT can be summised from the O2 sensor resistance.

Cat position affects the AVCS as well. You can also use AVCS to reduce engine load above a set cam timing load as a safety feature as well
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Re: E85/ Eflex and its affect on avcs

Postby andy_mac » Mon Apr 04, 2016 6:09 pm

Hey Benny, have you done any research into whether a 4-channel logger can be linked up to run with romraider? Still haven't sorted out a usefull way to log my EGBP readings other than maybe doing the TGV delete and using that.

Also, for AVCS optimisation, how critical would it be to have readings for both paths with a twinscroll or would having one be good enough to get things pretty close to bang on? Only measuring off one path at this point as I only had one boost gauge to connect to

EDIT: think using one of the phidget boards will be the way to go for logging the extra inputs
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Re: E85/ Eflex and its affect on avcs

Postby bigBADbenny » Tue Apr 05, 2016 6:44 am

My plan is to make a circuit that switches sequentially between each of the 4 sensors for a selectable duration, meaning the 4 channels of data can be logged over one sensor input, be it TGV/rearO2 ECU inputs or phidgets I/O for RomRaider PC logging.
Ultimately it simply allows for per cylinder fueling optimisation, the ultimate luxury for your tune. ;)
Talking advantage of BtSsm's flexibility with custom parameters, a switchbox could be setup for those spare ECU inputs to broaden the scope for logging different external sensors.
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Re: E85/ Eflex and its affect on avcs

Postby KiDo_Tuning » Sat Apr 09, 2016 9:59 am

andy_mac wrote:Hey Benny, have you done any research into whether a 4-channel logger can be linked up to run with romraider? Still haven't sorted out a usefull way to log my EGBP readings other than maybe doing the TGV delete and using that.

Also, for AVCS optimisation, how critical would it be to have readings for both paths with a twinscroll or would having one be good enough to get things pretty close to bang on? Only measuring off one path at this point as I only had one boost gauge to connect to

EDIT: think using one of the phidget boards will be the way to go for logging the extra inputs


Could have the inputs wired up to the 2.5mm socket using the wideband logger script but just asking for voltage and extrapolating data from there
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Re: E85/ Eflex and its affect on avcs

Postby bigBADbenny » Sat Apr 09, 2016 12:51 pm

Matt, is the 2.5mm just for SD logging or does it log to PC as well?
Eg same as pin8...
It's been a while lol.
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Re: E85/ Eflex and its affect on avcs

Postby andy_mac » Sat Apr 09, 2016 4:47 pm

Can't use the 2.5mm for PC logging, only to SD. Had been looking into using that for the wideband but according to someone over on the Romraider forum its a no go. The pin 8 option seems workable though, sounds like its easy enough to intersect if you have an OBD extension cable.
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