gkzs
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« on: August 12, 2013, 05:54:06 AM »
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Hello guys.
I ve been reading this great forum for long time, and finally decided to register my self.
I own a skoda octavia vrm 1.8T 20V 2006MY with uprated rods, gt28r, 630cc injectors.
If acceptable for a new person in the forum, would like to answer something.
I installed 1.8 N/A intake camshaft recently and i am facing afr weird behaviour. Requested AFR dropped to 0.92 (13.5:1) on idle, travelling even when i dont press the gas pedal. Idle load is ~ 20-22%. On wot drops to 0.78, as specified. Car works fine though, ~-1 +1 % trims on both banks.
I guess camshaft cause this weird afr richness. Can you help me? What should i change?
Regards
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userpike
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« Reply #1 on: August 12, 2013, 02:15:28 PM »
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Hello guys.
I ve been reading this great forum for long time, and finally decided to register my self.
I own a skoda octavia vrm 1.8T 20V 2006MY with uprated rods, gt28r, 630cc injectors.
If acceptable for a new person in the forum, would like to answer something.
I installed 1.8 N/A intake camshaft recently and i am facing afr weird behaviour. Requested AFR dropped to 0.92 (13.5:1) on idle, travelling even when i dont press the gas pedal. Idle load is ~ 20-22%. On wot drops to 0.78, as specified. Car works fine though, ~-1 +1 % trims on both banks.
I guess camshaft cause this weird afr richness. Can you help me? What should i change?
Regards
why did you install a NA cam into a turbo motor? |
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« Last Edit: August 12, 2013, 02:20:16 PM by ddillenger »
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catbed
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« Reply #2 on: August 12, 2013, 02:38:44 PM »
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why did you install a NA cam into a turbo motor?
Maybe the same reason people install 2.8 cams into 2.7Ts? More aggressive profiles. I don't have any experience with N/A 1.8T cams though. |
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Aurélien
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« Reply #3 on: August 12, 2013, 02:43:47 PM »
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Change in overlap.
How is you before/after airflow at idle ?
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gkzs
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« Reply #4 on: August 12, 2013, 03:23:07 PM »
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why did you install a NA cam into a turbo motor?
Maybe the same reason people install 2.8 cams into 2.7Ts? More aggressive profiles. I don't have any experience with N/A 1.8T cams though.
Thanks for your answers. Yes thats the reason. Its common used in 1.8T 20V. Change in overlap.
How is you before/after airflow at idle ?
Its the same! The afr changed only. I havent read somewhere same problem and i am really looking for help! To be honest i didnt expect something to change, only better power curve on higher rpms. AFR issue was never crossed my mind. Can be explained by the camshaft replacement (was in great overall condition)? Forgot to add that cylinder head was machined for better flow and valve kit, springs, retainers were uprated too (only for safety reason, had over 200000km, dont intent to run it over 7500rpm). Thanks for your time. |
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userpike
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« Reply #5 on: August 12, 2013, 05:22:41 PM »
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Maybe the same reason people install 2.8 cams into 2.7Ts? More aggressive profiles. I don't have any experience with N/A 1.8T cams though.
generally NA cams allow for a lot of valve overlap to try to take advantage of an inertial supercharging effect. this isn't really needed for forced induction. (neither is ultra high valve lift and super long durations) you'd be better off replacing that NA cam with one suited for a turbo charged engine, with a powerband in the rpm range you want. I guess if cost is a factor though, finding a used cam is probably cheaper but really everything else that's been done cost high dollar on his build, why not spend also on the right cams.. just wonderin. my guess though is that the richer afr is happening because some of the new intake charge is escaping out the exhaust valves due to valve overlap. |
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nokiafix
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« Reply #6 on: August 13, 2013, 12:47:47 AM »
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stock cams are perfect for the GT28R use the vvt mapping to aid spooling. As far as I know no one has proven the 1.8 NA cam theory works well. If you want extra power from the stock turbo cams you might want to start looking into the sweet spot on the inlet cam. try and make the inlet adjustable and play and log.  |
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gkzs
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« Reply #7 on: August 13, 2013, 04:38:50 AM »
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generally NA cams allow for a lot of valve overlap to try to take advantage of an inertial supercharging effect. this isn't really needed for forced induction. (neither is ultra high valve lift and super long durations) you'd be better off replacing that NA cam with one suited for a turbo charged engine, with a powerband in the rpm range you want.
I guess if cost is a factor though, finding a used cam is probably cheaper but really everything else that's been done cost high dollar on his build, why not spend also on the right cams.. just wonderin.
my guess though is that the richer afr is happening because some of the new intake charge is escaping out the exhaust valves due to valve overlap.
I respect your opinion. Only left is to see if this camshaft provokes afr richness or not. Otherwise it looks to be fairly aggressive on high rpms. stock cams are perfect for the GT28R use the vvt mapping to aid spooling. As far as I know no one has proven the 1.8 NA cam theory works well. If you want extra power from the stock turbo cams you might want to start looking into the sweet spot on the inlet cam. try and make the inlet adjustable and play and log. nokiafix to you think tha afr richness caused by the camshaft or not? If anyone have experienced something similar, please share his opinion. Can N/A camshaft cause this weird behaviour? Havent read it so far anywhere. Thanks for your time. |
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phila_dot
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« Reply #8 on: August 13, 2013, 07:23:42 AM »
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You need to log to see why target AFR changed.
Look at LAMKO.
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userpike
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« Reply #9 on: August 13, 2013, 11:10:47 AM »
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stock cams are perfect for the GT28R use the vvt mapping to aid spooling. As far as I know no one has proven the 1.8 NA cam theory works well. If you want extra power from the stock turbo cams you might want to start looking into the sweet spot on the inlet cam. try and make the inlet adjustable and play and log. Nokiafix is correct about the stock 1.8t cams. between 3000 and 5500 rpm they have the flattest torque curve of just about any OEM camshaft ever! To use them at higher rpm you can adjust the cam center lines. but you will lose some lower rpm torque, here's how to do it properly: http://blog.intengineering.com/adjusting-camshaft-center-lines-on-a-big-turbo-audi/ |
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littco
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« Reply #10 on: August 13, 2013, 03:18:38 PM »
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Does requested lambda remain @.92 all the time at idle or does it go back to normal once engine up to temp?
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gkzs
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« Reply #11 on: August 19, 2013, 04:17:11 AM »
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You need to log to see why target AFR changed.
Look at LAMKO.
Does requested lambda remain @.92 all the time at idle or does it go back to normal once engine up to temp?
Hello and thanks for your answers. Back from short vacations. I did changed second lambda and afr now its better, but not spot on. It stays around 14.5:1 on idle and after short trips stays at 13.4:1 and slows goes back to 14.5:1. Engine off, engine on -> goes 14.5-14.7:1. Also needle on idle is not 100% stable, has slight variations and exhaust sounds to spit gas some times. Load is ok ~17-19%, no CF or timing retard. I think i have to touch the KFBAKL / KFVAKL maps now. Any hint for 630 dekas? It confuse me cause this factor i dk where it is added and since audi tt225 (bigger injectors than vrs stock) has way different values than mine, i cant figure out what should i do. Should i multiply these maps by 1.3 and then trimming or i am thinking the practical wrong way? (krkte 0.05, temin/a 0.5, tvub ~0.69@12v, slight fkkvs trimming, kvb are the only i have touched so far with ltft/stfts ~-1%) Thank you. |
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« Last Edit: August 19, 2013, 04:18:44 AM by gkzs »
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julex
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« Reply #12 on: August 21, 2013, 12:45:57 PM »
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from my experience dekas are utter crap and tons of cars never idle on them right. I am not surprised your AFR at idle is all over the place. It is what it is.
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aef
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« Reply #13 on: September 01, 2013, 11:22:32 PM »
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userpike
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« Reply #14 on: September 02, 2013, 12:49:04 PM »
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One thing I noticed was incorrect in this thread was someone claimed that all 1.8t cams are the same, which is untrue. Comparisons with the AEB 1.8t engine and AWP, the AWP intake cam has more lift than the AEB, but from what I can tell (by visually inspecting), that is the only difference. The exhaust cams look identical and have the same lift.(both sets of cams, intake/exhaust checked with a digital caliper for lift, no I didn't record the difference.. I didn't think I would be sharing the info nor made it a point to remember) Although there are differences in the heads, the AEB being a large port head and the AWP being a small port head is the main difference and probably their reasoning behind the cam differences but all ultimately because of emissions. |
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