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2004 Forester XT
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20 Posts
Discussion Starter #1
Alright, so please forgive me if this has already been discussed elsewhere, but I'm rather displeased with the throttle response on my '04 FXT. So far as I can tell, the slow response is a safety programming added into the Drive-by-wire system, so that under hard acceleration the throttle plate opens up a second or so after the gas pedal is pushed down. This of course makes for some pretty poor acceleration, even with a modified car.

I can't imagine I'm the only guy who hates this, so I'm hoping there's something we can do about it. If anyone has thoughts (The engineers, perhaps?), please toss them my way, as I'd love to get rid of this massive flaw. thanks.
 

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Smooshed FOTY 2011
2005 Lifted 2.5 XT 5-Speed MT Dual-Range
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5,732 Posts
To be honest, I have no idea what you are talking about (in regards to the system being sluggish). The only thing that's sluggish is my downshifts on the 4EAT, but other than that, this is the best drive-by-wire system I've ever had the pleasure of using. On my XT, if I put it into 2nd, and floor it, it's 100% immediate on the throttle response, no delay what so ever.

I would probably have your system checked to find out if there's a solenoid or servo not working to it's fullest.
 

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2004 Forester XT
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20 Posts
Discussion Starter #3
To be honest, I have no idea what you are talking about (in regards to the system being sluggish). The only thing that's sluggish is my downshifts on the 4EAT, but other than that, this is the best drive-by-wire system I've ever had the pleasure of using. On my XT, if I put it into 2nd, and floor it, it's 100% immediate on the throttle response, no delay what so ever.

I would probably have your system checked to find out if there's a solenoid or servo not working to it's fullest.
Thanks, but I am the guy who checks to see if the system works to its fullest ;) I've discussed the issue with a number of other professional Subie mechanics, including a performance guru. If you've ever driven one of the newer Nissan 350Zs, you'd know what I'm talking about -- their response is instant. Subaru's is actually quite slow =/
 

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Premium Member
2017 VW Golf SportWagen 5MT
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10,784 Posts
Agreed, throttle response isn't as crisp and linear as on other cars I've owned, like the Miata for example. Don't have too much experience with other turbo cars to compare to, my ex's Volvo S60 wasn't ideal either.

Stan
 

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2004 fxt A/T
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2,567 Posts
Thanks, but I am the guy who checks to see if the system works to its fullest ;) I've discussed the issue with a number of other professional Subie mechanics, including a performance guru. If you've ever driven one of the newer Nissan 350Zs, you'd know what I'm talking about -- their response is instant. Subaru's is actually quite slow =/
Are 350z's turbocharged? Do you have logs to show the delay in gas pedal and throttle plate opening? I thought the pedal was a bit aggressive in my opinion, basically past 2/3 pedal movement throttle position is at 100%. No I haven't driven a 350z.
 

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2016 Outback and WRX CVT
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2,551 Posts
Philosoforester -

To the best of "feelings" generated by my rather inaccurate (mostly due to rather cushy insulation: aka fat :redface:) butt-dyno, I've always felt that turbocharged vehicles were somewhat "sluggish" in terms of throttle response when off-boost. I actually don't know that "sluggish" is a good descriptor, but I'm at a loss as to how to better describe it: to me, it just feels that, off-boost, the throttle isn't nearly as responsive as that of a N/A vehicle.

I know that this is a feeling that's shared by many drivers/enthusiasts, and I wonder if perhaps this isn't what you're referring to, particularly as you're comparing the FXT with a rather nice N/A 6-cyl. sports car, with a powerplant that's known to be decently responsive and linear.

However, there's other concerns, too, which are purely technical.

And in this direction, I'd like to ask what, specifically, did you discuss with your local Scooby enthusiasts:

Are you referring to perhaps some of the "rough spots" (have a search for hesitation/"stuttering"/"studdering") that's typically seen at part-throttle, while at-cruise.

Or are you referring to the Drive-By-Wire (DBW) ECU mapping parameter known as "Requested Torque?"

Or are you referring to the CL/OL transition?

To examine each of these issues:

The first of these three concerns continues to baffle enthusiasts and tuners alike. So far, there's been much speculation, and a number of those affected have been able to achieve at least some level of resolution - but just as there lacks consensus in what's the root-cause(s) of the issue, there's also a lot of inconsistency in resolution.

As for the second, that's something that can be altered via the DWB vehicle's ECU. In my rather layman's :redface: understanding of the issue, Subaru's more recent "Si-Drive" is just such a trick. I found rtbrjason's post on LegacyGT.com particularly useful in describing how this is applied with "Si-Drive" - Subaru Legacy Forums - View Single Post - ? about Cobb AP and Si Drive , and also, NSFW's early posting (http://legacygt.com/forums/showthre...88377.html?t=88377&highlight=requested+torque) should provide some additional clarification, via its OP graphic. Additionally, there are now very affordable aftermarket products on-market which are designed to specifically alter this aspect of a DWB vehicle's behavior - the "NTD 3-Drive Throttle Controller" is just such a product. I've yet to see its use on a force-induced Subaru, but it's become popular in the N/A Subaru community, as you can see here: http://legacygt.com/forums/showthread.php/official-test-ntd-throttle-control-unit-123112.html

As for that latter "bump" that you often feel in terms of CL/OL, it can also be accounted for via the ECU.

And like I said above, I'm really not that well-versed when it comes to ECU trickery: I'm a traditional backyard greasemonkey DIY-wrench. :redface: So this is a question, in-turn, that I'm posing to those with more knowledge than me: does tip-in enrichment also contribute to this issue?
 

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05 FXT
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1,540 Posts
So it's not so much a safety item as it is an emission type of thing. Tip-in emissions account for a surprisingly high %, so one way to cure it, limit just how fast you can tip in.

I've dabbled with the tuning side, and although many claim it can be improved, I think it's as much pyschological as it being really fixed. I think you can make some small gains, but nothing too earth shattering.

I've actually found more means to prevent the condition from getting worse with other mods, ie going to bigger fuel injectors is a nasty one.
 

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2016 Outback and WRX CVT
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2,551 Posts
So it's not so much a safety item as it is an emission type of thing. Tip-in emissions account for a surprisingly high %, so one way to cure it, limit just how fast you can tip in.
Certainly.

Given how much attention is paid to emissions control these days, it seems like everything carries, at least in-part, that layer of concern.

I've dabbled with the tuning side, and although many claim it can be improved, I think it's as much pyschological as it being really fixed. I think you can make some small gains, but nothing too earth shattering.
Again, I agree.

I think that while this throttle-mapping behavior becomes more apparent the "farther" the maps are apart - i.e. in going from a lazy-response (i.e. "economy") map to a very, very sharp one (i.e. "Sport-Sharp" or the like), there's a lot of space covered in-between, and thus, there will be a noted transition - that with a vehicle which did not initially enjoy such distinct settings, the differences are going to be much harder to notice.

Many vehicles, from imports to domestics, from family-sedans to sports-cars, are now so-equipped, and I truly think that how noted the character-changes are, between any "settings," is heavily based on how wide-spread the gradients happens to be.

Back in '05, well-before the advent of Subaru's Si-Drive, a then-popular tuner offered custom AccessPORT maps which incorporated a noticeably more aggressive throttle mapping: those who sampled it and compared it against Open-Source remapping of the same reported results similar to that of a factory STi's throttle mapping of that vintage - if not outright even more aggressive. Indeed, quite a number of customers who initially sought out such mapping later reflashed to a less-aggressive throttle map, to better suit their commuting nature.

Truthfully, where I personally think that more linear/progressive throttle mapping and/or throttle-map tuning/tinkering (which, as seen in the reference posts, is more a subjective matter than it is objective) would be with those who heavily track or autocross the vehicle, where a finer degree of throttle control, per the end-user's physical preferences, may make a more apparent difference in terms of vehicle control.
 
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