AVCS - Intake and Exhaust Timing

[solidONE]

Originally Posted by thambu19

You lost some torque below 3K? Anyway you can keep your old cam settings below 3K and get the best of both worlds?

Okay. I will try that. Although those 2 pulls in the first graph were using different headers along with cam timing. The lower output one was a Tomei El header. If you look at the red trace on the 2nd graph where I began the pull from lower RPM the torque is actually a bit higher. Unfortunately I never did do a pull from under 2000rpm with the tomei.

[thambu19]

@solidONE
Yes the AFR for best torque changes with engine to engine design and with engine speed to another speed. From experience it goes from leaner than 12.5 at lower speeds to richer at peak power. The 11.8 I suggested was to keep exh temp below 900C (some reasonable safe limit) IF you feel your header, exh valves etc can take hotter temp you can go leaner than that. On my stock FRS with a LIVE CAT no way I would go leaner than 11.5 anywhere just to be safe.

[thambu19]

Contrary to popular belief engine knocks slightly more with slight enrichment. This is because of slightly faster and hotter combustion. It's called water gas shift reaction

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[thambu19]

Originally Posted by thambu19

Contrary to popular belief engine knocks slightly more with slight enrichment. This is because Of slightly faster combustion. It's called wateR gas shift reaction

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As we move towards 12.5 though we can add more spark. This is because in the initial phase of slight enrichment the combustion speeds up and get hotter but as we add more fuel and approach 12.5 we cause some cooling effect due to evaporating fuel and the mixture itself slows down in burn rate and can take more spark advance.


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[KoolBRZ]

@solidONE, thanks for posting those tables. I'd lost the set of tables developed by someone else for the long tube header. Now I can start from those to develop a set for the Phantom ESC and long tube header owners.

[solidONE]

Originally Posted by thambu19

@solidONE
Yes the AFR for best torque changes with engine to engine design and with engine speed to another speed. From experience it goes from leaner than 12.5 at lower speeds to richer at peak power. The 11.8 I suggested was to keep exh temp below 900C (some reasonable safe limit) IF you feel your header, exh valves etc can take hotter temp you can go leaner than that. On my stock FRS with a LIVE CAT no way I would go leaner than 11.5 anywhere just to be safe.

Got ya!

Originally Posted by thambu19

Contrary to popular belief engine knocks slightly more with slight enrichment. This is because Of slightly faster and hotter combustion. It's called wateR gas shift reaction

Sent from my HTC One_M8 using Tapatalk

What about in low/mid-load situations? Does this still hold true? Specifically the areas when I have the fueling dialed slightly richer than stoich at 60.~70 loads, low to mid rpms. Or, does this only apply to peak loads going WOT or close to WOT?

[thambu19]

Originally Posted by solidONE

Got ya!



What about in low/mid-load situations? Does this still hold true? Specifically the areas when I have the fueling dialed slightly richer than stoich at 60.~70 loads, low to mid rpms. Or, does this only apply to peak loads going WOT or close to WOT?

It always holds true. If going richer the AFR should be richer than ~13.3 to really see benefits of knock resistance but operating slightly rich can improve combustion and you will feel a smoother engine but not good on emissions

[steve99]

Originally Posted by thambu19

@solidONE
Yes the AFR for best torque changes with engine to engine design and with engine speed to another speed. From experience it goes from leaner than 12.5 at lower speeds to richer at peak power. The 11.8 I suggested was to keep exh temp below 900C (some reasonable safe limit) IF you feel your header, exh valves etc can take hotter temp you can go leaner than that. On my stock FRS with a LIVE CAT no way I would go leaner than 11.5 anywhere just to be safe.

@solidONE

If you guys have tactrix you can monitor cat temp for B01C roms. ECU uses o2 sensor heater current to calculate temps

Ram_cat_temp FFF8DBD4


add this to your logcfg.txt file

paramname = CAT_Temp
paramid = 0xFFF8DBD4
isfloat = 1


else you can use Techstream to monitor

I'm not seeing much over 720C on E85 hot day hard uphill mountain run AFR target about 12.3 high rpm/load

probably be a good parameter for shiv to add to OFT logging

[solidONE]

Originally Posted by thambu19

It always holds true. If going richer the AFR should be richer than ~13.3 to really see benefits of knock resistance but operating slightly rich can improve combustion and you will feel a smoother engine but not good on emissions

If that's the case, I may consider reducing the fuel and ignition advance even further to try to get some better fuel economy, cause that range where you're very often in while cruising (it's also where this engine seems very prone to knocking). But I'd expect a noticeable reduction in part throttle power. decisions decisions...

About the cam timing, would you recommend changing the exhaust timing to reduce overlap on my current tables to being with? Or should I reduce intake cam advance? Or a bit of both? You mentioned reducing the overlap, are you talking about the 3200~4800 range, the 4800~6100rpm range, or just all of it? lol

http://datazap.me/u/solidone/plm3-ca...1628-1595-1658


@steve99 I've not had the chance to pick up a tacktrix yet, although I'd assume the secondary cat wouldn't be as susceptible to damage from overheating since most stage 2 setups (including mine) do not run a cat on the header. I've actually measured surface temps on the exhaust and it runs much much cooler after the over pipe. Not saying that it's in any way "cool," but it does not get nearly as hot as the header.

[thambu19]

Originally Posted by steve99

@solidONE

If you guys have tactrix you can monitor cat temp for B01C roms. ECU uses o2 sensor heater current to calculate temps

Ram_cat_temp FFF8DBD4


add this to your logcfg.txt file

paramname = CAT_Temp
paramid = 0xFFF8DBD4
isfloat = 1


else you can use Techstream to monitor

I'm not seeing much over 720C on E85 hot day hard uphill mountain run AFR target about 12.3 high rpm/load

probably be a good parameter for shiv to add to OFT logging

That would be modeled cat temp. I was talking about measured real temp. Once we start messing with stuff I am not sure if modeled temp holds true to measured.

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[thambu19]

Originally Posted by steve99

@solidONE

If you guys have tactrix you can monitor cat temp for B01C roms. ECU uses o2 sensor heater current to calculate temps

Ram_cat_temp FFF8DBD4


add this to your logcfg.txt file

paramname = CAT_Temp
paramid = 0xFFF8DBD4
isfloat = 1


else you can use Techstream to monitor

I'm not seeing much over 720C on E85 hot day hard uphill mountain run AFR target about 12.3 high rpm/load

probably be a good parameter for shiv to add to OFT logging

Sorry I did not read the last part right. I thought something else where the ECU is monitoring Exh and CAT temp using some modeling technique. If it is using O2 sensor current it should be close to actual temperature.

The reason you are running colder (although 720C sounds pretty cold to me) is because of E85. E85 will cause colder exh temp due to the additional spark. The more spark added in the colder the exh and vice versa. Same with cams. The earlier its opened the hotter it is.

I am wondering if ECU ever uses this value to manipulate fueling. Like adding extra fuel on top of open loop fueling if the temps are too high. Will need those running headers to tell us what temps they are seeing for exh and cat.

[thambu19]

Originally Posted by solidONE

If that's the case, I may consider reducing the fuel and ignition advance even further to try to get some better fuel economy, cause that range where you're very often in while cruising (it's also where this engine seems very prone to knocking). But I'd expect a noticeable reduction in part throttle power. decisions decisions...

About the cam timing, would you recommend changing the exhaust timing to reduce overlap on my current tables to being with? Or should I reduce intake cam advance? Or a bit of both? You mentioned reducing the overlap, are you talking about the 3200~4800 range, the 4800~6100rpm range, or just all of it? lol

http://datazap.me/u/solidone/plm3-ca...1628-1595-1658


@steve99 I've not had the chance to pick up a tacktrix yet, although I'd assume the secondary cat wouldn't be as susceptible to damage from overheating since most stage 2 setups (including mine) do not run a cat on the header. I've actually measured surface temps on the exhaust and it runs much much cooler after the over pipe. Not saying that it's in any way "cool," but it does not get nearly as hot as the header.

You could be running a bit lean on the 2200rpm area. Id try to reduce a bit of overlap on both ends to see what happens. Drop intake from 40 to 36 and see what happens first... You are holding overlap all the way to 6K... Not sure if that is necessary. I mean I just don't know. I would assume with long tube headers your scavenging effect has ended around 4K already and from there on you may not really see any real scavenging. So id try (experimental here) start pulling the intake backward slowly from 4.5K onwards. For exhaust timing I don't know how far your timings are from stock timings. Generally you want to open the exhaust close to what the stock timings were not too earlier than that because you are running lower back pressure and so the blowdown will be quite strong. Opening exh too early you are just losing torque.

[steve99]

Originally Posted by thambu19

Sorry I did not read the last part right. I thought something else where the ECU is monitoring Exh and CAT temp using some modeling technique. If it is using O2 sensor current it should be close to actual temperature.

The reason you are running colder (although 720C sounds pretty cold to me) is because of E85. E85 will cause colder exh temp due to the additional spark. The more spark added in the colder the exh and vice versa. Same with cams. The earlier its opened the hotter it is.

I am wondering if ECU ever uses this value to manipulate fueling. Like adding extra fuel on top of open loop fueling if the temps are too high. Will need those running headers to tell us what temps they are seeing for exh and cat.

I assume its using front o2 sensor ,i have catless header but retain the stock secondary cat, so it probably going to run a bit cooler that stock with primary cat in header i would think, plus the E85.

I will try to plug my tactrix into someones car with stock header on petrol and see what the temps are

[solidONE]

Originally Posted by thambu19

You could be running a bit lean on the 2200rpm area. Id try to reduce a bit of overlap on both ends to see what happens. Drop intake from 40 to 36 and see what happens first... You are holding overlap all the way to 6K... Not sure if that is necessary. I mean I just don't know. I would assume with long tube headers your scavenging effect has ended around 4K already and from there on you may not really see any real scavenging. So id try (experimental here) start pulling the intake backward slowly from 4.5K onwards. For exhaust timing I don't know how far your timings are from stock timings. Generally you want to open the exhaust close to what the stock timings were not too earlier than that because you are running lower back pressure and so the blowdown will be quite strong. Opening exh too early you are just losing torque.

You know, I'm really not sure why in the log the intake cam stays that much advanced 37.5~40* to 6000rpm. On the intake advance table it's set to 40* from 2400~4600rpm, and from 4800~6000rpm it's set to 35* advance. Very strange... I'll need to log the cam timing some more just to double check.



The exhaust cam retard table is actually not hugely different than the stage 1 OTS tables designed for use with factory headers. Although the OTS stage 2 tables actually run even more exhaust retard than the stage 1. I'll have to see if I can find the stock rom see what they look like.

Difference compared to OTS STG1:


Difference to OTS STG2 EL:


Thanks again for all the pointers, BTW.

Edit: Yup the intake cam is staying advanced further than designated by the cam tables.

4th gear pull just now:
http://datazap.me/u/solidone/af-lear...zoom=2699-3008

3rd gear pull in the same log where it drops down to 37.5* at 4800 rpm. Still not at 35* when it was set to on the table:
http://datazap.me/u/solidone/af-lear...zoom=1595-1732

There's got to be something else effecting the cam timing that we don't yet know about.