poor 3k-8k run...

[ArthurPE]

stock car (???) I'll explain why I think it may not be...
3 guys in it
95 oct
85F

>17 sec in 3rd gear...(actually he let off at 7700, call it 18 sec)

a concerned owner wondered if there was an issue...he sent me his vagcom charts

seems terrible doesn't it?

timing was perfect close to 30 deg under high rpm/load
lambda, spot on 0.85 vs 0.85 at the high end

but mass airflow Q was way off....deposits!!!!!!!

my records from several cars ~152 g/sec at 7500 rpm
theoretical is 150
his...120
whoa.....80%, 20% too low...hmmmmm

then I noticed where he said he lived...at 5500' asl...
ratio of atm pressure http://www.engineeringtoolbox.com/air-a ... d_462.html
sl ~ 14.7
5500' ~12

12/14.7 ~ 80%

the mystery is solved
the car is fine, all is right in the world
deposits defeated again!!!!
the end

footnote: I think the car was modded because throttle is 100% <3000 rpm

btw, I live at 1100' asl...my car is always down by~5% or 20 HP
deposits add (subtract) another 20HP
over rating another 40 HP
my net crank HP 340, same as an S4 at seal level...

[RS4FTW]

stock car (???) I'll explain why I think it may not be...
3 guys in it
95 oct
85F

>17 sec in 3rd gear...(actually he let off at 7700, call it 18 sec)

a concerned owner wondered if there was an issue...he sent me his vagcom charts

seems terrible doesn't it?

timing was perfect close to 30 deg under high rpm/load
lambda, spot on 0.85 vs 0.85 at the high end

but mass airflow Q was way off....deposits!!!!!!!

my records from several cars ~152 g/sec at 7500 rpm
theoretical is 150
his...120
whoa.....80%, 20% too low...hmmmmm

then I noticed where he said he lived...at 5500' asl...
ratio of atm pressure http://www.engineeringtoolbox.com/air-a ... d_462.html
sl ~ 14.7
5500' ~12

12/14.7 ~ 80%

the mystery is solved
the car is fine, all is right in the world
deposits defeated again!!!!
the end

footnote: I think the car was modded because throttle is 100% <3000 rpm

btw, I live at 1100' asl...my car is always down by~5% or 20 HP
deposits add (subtract) another 20HP
over rating another 40 HP
my net crank HP 340, same as an S4 at seal level...

Wonder who's car that was

Car is definetely stock. Reason is that the throttle is open 100% @ 3000 is due to being at 5500ft ASL. Due tot he engine being 17 to 20% down on power the ECU can tell that and not need to close the throttle 50% to help with "torque dampening"

It dyno'd the same as other stock RS4's up here at 5500ft asl and the 8000 rpm rev limiter is still there.

Oh forgot to tell you aswell, that run was down on about a 30 degree incline.

My vagcom cable should be arriving shortly so will do a proper run then

[ArthurPE]

I wonder

good info about the throttle limit being overridden by torque demand...
thanks

the 30 deg incline is steep, that;s another large portion of power that is missing, it is used for lkifting against gravity as opposed to accelerating the mass...maybe 15%

Wonder who's car that was

Car is definetely stock. Reason is that the throttle is open 100% @ 3000 is due to being at 5500ft ASL. Due tot he engine being 17 to 20% down on power the ECU can tell that and not need to close the throttle 50% to help with "torque dampening"

It dyno'd the same as other stock RS4's up here at 5500ft asl and the 8000 rpm rev limiter is still there.

Oh forgot to tell you aswell, that run was down on about a 30 degree incline.

My vagcom cable should be arriving shortly so will do a proper run then