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 Post subject: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Tue Oct 24, 2017 12:27 pm 
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Vehicle: 2001 GT - Red Mica

Posts: 4
Location: CBR
I have searched high and low for a straight answer to this question and cannot find one. I will be eternally grateful to any of you fine humans that can give me the information I desire. Basically what I want to know is:

Is it possible to fix the throttle lag on subaru's fitted with dbw or eletronic throttle systems.

What I really want is a first hand account of someone who went from an old car with a physical throttle cable to a new car with electronic throttle control, who NOTICED there was a lag, and succeeded in correcting it with a tune.

What I am talking about is the ~1s lag between pressing the accelerator and the system deciding to do anything about it. this is most obvious if you are trying to rev match by blipping the throttle, or if you have stalled the car on a hill start or similar because of the delay to action. If you find that you have to mash the throttle really hard instead of blipping it, or anticipate rev requirements ahead of time, you may be suffering from this.

Every other thread I have come across with regard to this question just gets filled up with people who do not understand the issue nor recognise it in their own car.

- I am not talking about turbo lag.
- I have considered the option of "Just getting used to it" or "adjusting my driving style" and it is not desirable for many reasons.
- I am happy for you if you have not recognised this in your car, but it does not help me here.
- Throttle boosters will not solve this issue.
- This problem is far more noticeable if you are a driver who habitually rev matches their downshifts.

I have owned an Evo 6, and currently drive an '01 forester GT, both of which have perfect and immediate throttle response as they are fitted with a physical cable connected to the throttle. I want to replace my foz GT with an ~07 XT but won't do it if I don't know I can cure this issue, it really kills the fun of driving to me.

Seriously, Please help me. this question is driving me insane. Thank you all so much.


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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Tue Oct 24, 2017 1:27 pm 
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Last edited by Tobyo on Tue Oct 24, 2017 4:20 pm, edited 1 time in total.

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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Tue Oct 24, 2017 3:58 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

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Location: Spearwood Perth WA
Dunco wrote:
I have searched high and low for a straight answer to this question and cannot find one. I will be eternally grateful to any of you fine humans that can give me the information I desire. Basically what I want to know is:

Is it possible to fix the throttle lag on subaru's fitted with dbw or eletronic throttle systems.


What I really want is a first hand account of someone who went from an old car with a physical throttle cable to a new car with electronic throttle control, who NOTICED there was a lag, and succeeded in correcting it with a tune.

What I am talking about is the ~1s lag between pressing the accelerator and the system deciding to do anything about it. this is most obvious if you are trying to rev match by blipping the throttle, or if you have stalled the car on a hill start or similar because of the delay to action. If you find that you have to mash the throttle really hard instead of blipping it, or anticipate rev requirements ahead of time, you may be suffering from this.

Every other thread I have come across with regard to this question just gets filled up with people who do not understand the issue nor recognise it in their own car.

- I am not talking about turbo lag.
- I have considered the option of "Just getting used to it" or "adjusting my driving style" and it is not desirable for many reasons.
- I am happy for you if you have not recognised this in your car, but it does not help me here.
- Throttle boosters will not solve this issue.
- This problem is far more noticeable if you are a driver who habitually rev matches their downshifts.

I have owned an Evo 6, and currently drive an '01 forester GT, both of which have perfect and immediate throttle response as they are fitted with a physical cable connected to the throttle. I want to replace my foz GT with an ~07 XT but won't do it if I don't know I can cure this issue, it really kills the fun of driving to me.

Seriously, Please help me. this question is driving me insane. Thank you all so much.



There is no discernable lag with the electric throttle body (if working in good order, and properly tuned.) Atleast not 1s. Maybe somewhere in the vicinity of 100ths of a second. A human would certainly be unable to detect it. The ECU cycles many 1000s of times per second, and will near instantly determine a change in the 2 x APS values, put that through its requested torque table and output drive to the motor. Then cross refference that against its 2 x TPS sensors and adjust. The motor can drive the throttle open incredible fast, even against the heavy close spring. (So fast it audibly snaps open.)

Further more, there are many advantages to the electric system, both for a regular car, and a performance orientated car. Things like:
No IACV - Better idle control.
Built in throttle control - Allows for easy cruise control.
Closed loop system - Never needs adjusting. (But does occaisionally need cleaning)
Ability to run anti-lag systems without complication.
Throttle blip downshift.

I run with it in my race car and have never had problems. Modena gearbox company actually specifically recomends having it fitted to old model vehicles when fitting one of thier sequential kits so that throttle blip down shift be utelised. Sequential gearboxs are almost exclusively used in motorsports vehicles, where every micro-second counts.

I am actually retro-fitting a no expense spared tarmac STi from cable to DBW this weekend. FYI - Car has a Willall billet EJ with full RCM catalouge thrown at it. Modena sequential w/ all upgrade diffs. Motec management, 8 piston brembo monoblocks, titanium pipework, carbon body etc. As you can see, the owner wants the best of the best, and has the cash to make it happen. And even on such a high end car, he wants electric throttle as the multiple benefits far outwiegh any delay issues.

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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Tue Oct 24, 2017 5:30 pm 
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Vehicle: JDM SF STi Pure White

Posts: 153
Location: Germany
TL;DR: There is no humanly detectable throttle lag on DBW systems.
Whatever car you were experiencing this with probably had a completely different issue.

Used to have an '06 Impreza, those already had electronic throttle. It was freaking fast. The throttle, of course, not the car, it was just a 2.0R.


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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Tue Oct 24, 2017 5:46 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

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Dunco - With regards to the "rev match" comment.

I challenge you to throttle blip downshift a sequential as fast as a sequential can shift using actual throttle (cable or DBW). Either heel/toe or left foot brake clutchless flatshift. There is a reason why the manufactures of sequential gearboxs specifically recommend an ECU controlled DBW throttle blip. It is becuase the DBW is simply gonna be faster and smoother than a human can achieve.

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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Tue Oct 24, 2017 11:51 pm 
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Vehicle: 2001 GT - Red Mica

Posts: 4
Location: CBR
Thanks everyone who took the time to reply, much appreciated.

I don't think this is a limitation with the technology itself, but rather the implementation by Subaru (and many other manufacturers). I understand that the technology itself is superior and I have driven newer vehichles (BMW ~2016) that have dbw systems that I found perfectly responsive. It seems to be a common complaint for drivers of vehicles from when dbw just started going in to large numbers of cars (2000?), to somewhere around 2010-2015 at which time there seem to be more reports from people saying newer cars didn't have the problem anymore.

I noticed it in my girlfriends '09 impreza and I have read of others with WRXs and Forester XTs who have noticed the same thing. Most people attribute it to "emissions standards" but do not back that up with any more information and the only reference to a source was some long forgotten magazine article a poster read once.

MOOG from Mighty Car Mods also complains about a very similar issue in his forester XT

It looks like a choice made by Subaru to either improve emissions, reduce wear, or smooth out bumpy driving, rather than a limitation or failure of DBW technology. All the same I really would love to know if the issue I describe can be fixed where it exists.


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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Wed Oct 25, 2017 12:33 am 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17776
Location: Spearwood Perth WA
Have a play with the DBW/requested torque tables in the ECU. Throttle angle VS accelerator pedal angle ARE NOT directly proportional in the tune. You can alter the table that controls this to alter the throttle behavior. I believe as standard it is a 3d table that references APS vs TPS vs RPM. And you can change the interaction between APS to TPS, at various RPM.

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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Wed Oct 25, 2017 6:28 am 
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Vehicle: MY07 XT - Urban Grey / MY99 GT

Posts: 2
Location: Sweden
I have a Forester XT 2010 and got it fixed with help from my e-tuner "Patrick P931"

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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Thu Oct 26, 2017 8:29 am 
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Vehicle: 2001 GT - Red Mica

Posts: 4
Location: CBR
Thanks Pubbe! i might get in touch with Patrick when the time comes. Woukd you say you eliminated it 100% or just made a significant improvement?

Cheers mate!


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 Post subject: Re: Drive by Wire (DBW) throttle Lag - confirmed fix?
PostPosted: Thu Oct 26, 2017 1:28 pm 
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Vehicle: MY06 XT - Black

Posts: 2202
Location: Canberra
I messed around with the throttle mapping a little in my 06 XT, and I habitually blip on downshift. I ended up going back to the stock DBW map, and like it best. No noticeable lag.

Perhaps your issue is with the drivetrain itself? Heavy stock flywheel maybe. Do you have a light flywheel in your Evo or GT? I have a light flywheel in mine and it's certainly possible it makes a difference in the perception of throttle response.

My next step is a 6 speed with a stock clutch and flywheel. I'll be paying attention to this thanks to this thread, just for interests sake.

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