Topic: Throttle mapping for '08 WRX

[Airboy]

I took a look at the Drive-By-Wire Throttle maps in the 08 WRX to see if how it differs from the '06 WRX.  The difference is rather drastic. The '06 throttle is fairly linear between the pedal and the throttle plate; 20% pedal will give ~20% throttle plate opening, 50% pedal gives ~50% throttle plate.


The '08 on the other hand, has a sharp rise from low pedal position (cruising at ~10%) to mid throttle, then flattens out and once you hit ~50-60% pedal, the throttle opens all the way. In the "flat spot" (1600-4000rpm, <50 pedal), the throttle is "sluggish", where pedal movements doesn't give much throttle plate opening. Push the pedal past 50-60% and you get full throttle.&nbsp; Hmm...this could be related to the "rubber banding" that was mentioned in another thread http://westernsubaruclub.com/smf/index.php?topic=3736.0



Of course, this is based on one set of maps. The overall transfer function would need to be checked with some data logging.

Update
collected some data logs of the throttle response at part throttle.  It does follow the strange map where the throttle will open more at higher RPM even if you hold the pedal at the same position.


Not sure what the purpose of this is, may be to improve volumetric efficiency?  Higher throttle opening to reduce pumping losses and at the same time, the Wastegate actuator is allowed to open (low WGDC limit) to reduce restriction in the exhaust path?

[darkrid3r]

Sunny,

I will be in Calgary for sure if you wana log my car. I tend to drive the bejeepers out of it so i don't notice the rubber band effect all that much. I tend to also sit at 4k RPMs a lot 

Its very weird there is a complete 100% crazy difference in both your maps. The 08 has like peeks and valley's where as the 07 is fairly linear.

I did "play" with an 07 WRX on the high way, un-tuned i suspect. In third i can eat him bad, In fourth he has more "go" than me, in 5th i have more "go" than him. Also i can top my car out at 265 Kms\hr, which is over the speedometer, where he cant make it much beyond 250 kms\hr (this is not condoned, nor is it EVER recommended)

I have been playing with the peddle as snackers mentioned that he has some weird peddle to the floor thing going on, which i can't reproduce.
So if i keep it under 2400 and shift before 2800 i get mega good gas mileage, like 8.2 per 100k. The funny thing is if i stay around the 4000 mark as shown in your graph i also get about 9.2-.6
If i am anywhere in-between those RPMs gas mileage is around 12.6-14.2 per 100km

Hope this helps.

[pitwipe]

A friend of mine with an 08 G35 complains of a similar non-linear throttle response. He says it makes it more difficult to judge how much 'peddle' input to give the car when accelerating out of corners and such.

[snackers]

The peddle play that I was mentioning, just so you know Sunny...
I'm not sure if this has any effect on anything.
From NO throttle (foot off the gas) to some throttle (any position where you notice RPMs change) is quite a large physical distance, I noticed.
I can push the pedal probably more than a full inch before I get any throttle reponse out of the engine.
I noticed this after you pulled the map from mine (I wasn't sure if your pull caused an ECU reset for some reason?), but it increased drastically. I almost stalled it several times in 1st, not expecting to have to push the pedal so far to actually get it going. It has since corrected itself (or perhaps I have gotten used to it?) which is why I suspected a reset occured.

As for mileage, as darkrid3r says, mine are similar.
In the city, I rarely boost unless I get on a straightaway and want to have some fun. (rather, I should say, I don't go over 2800rpm)
With regular city driving, it says I average 10.6l/100k. My actual logs (I keep a spreadsheet) says I get 25-26mpg.
When I push it hard, I get approx 14.5l/100k.

Thanks for the info Sunny. While I'm no ECU expert (even less than a novice), your post makes absolute sense to me.
Subaru obviously did something to make this much of a change (although their reasoning escapes me).

Perhaps one of the seasoned drivers will want to take me up on my offer and "test drive" my 08, and compare it to their WRX (or STI i guess).
Your graphs absolutely represent the "elastic" response that we are getting.

[Cyni]

Sunny, do you have the throttle logs of my car after the tune?  Any difference?

I remember us seeing full boost even at 50% throttle if I remember correctly.

[Airboy]

Sunny, do you have the throttle logs of my car after the tune?  Any difference?

I remember us seeing full boost even at 50% throttle if I remember correctly.

At that time I only logged one out of throttle related parameters but you are right, it was able to build full boost at ~1/2 throttle.  However, that is likely more related to boost and wastegate maps.  BTW, I think I know why your boost and wastegate duty cycle drops off so much at the high end.  Doesn't happen at sea level but will at 3500'

I'll have to do some data logging to check/verify the transfer function for the pedal to throttle.  The DBW system is very complex and the "exposed" tables that we have access to at this time may not cover the "full chain".

[darkrid3r]

I dont mind full boost, as a matter of fact, more would be better 

[Hurricane]

I think they are doing this to increase fuel economy while still making the car seem more powerful than it is. You have to apply a fair amount of pedal to get into boost (fuel economy), but at ~50% throttle the car takes off (ECU applying 100% throttle). Most people aren't aware of throttle by wire and so perceive that there is more power available than there is. This has been done in the past by manufacturers but in reverse, low throttle pedal application affecting large actual throttle application making a car seem more peppy and torquey.

Jeff

[darrenbt]

Perhaps one of the seasoned drivers will want to take me up on my offer and "test drive" my 08, and compare it to their WRX (or STI i guess).
Your graphs absolutely represent the "elastic" response that we are getting.

I may not be overly seasoned, but we could trade testdrives and you could see what my STI is like as a comparison...

[Airboy]

updated 1st post with logged data