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  #1  
Unread 28th April 2019, 02:24 AM
Beachworm Beachworm is offline
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Default Making the best of new technology in post 2008 Subarus

I've read a lot in this forum about modifications to improve Subarus for whatever their owners desire them to be capable of. There has been lots of chat about suspensions, gearboxes, ancillary gear etc. but very little about modifying the car's ECU.

After I fitted a lift kit, bigger AT tyres, sump guard, diff breathers, roof racks and other bits and pieces, was there any way I could get my SH Forester to perform better off road before looking at expensive options such as locking diffs? Even a centre diff lock for an SH can cost upwards of $500 unless you are handy with electronics and a soldering iron. I began to research and discovered that almost every aspect of the engine and driveline is controlled to some extent by the ECU and it should be possible to rewrite the ECU programming to change critical aspects of the system.


The ECU controls how the engine delivers both power and torque, how the auto gearbox manages shifts, how the centre diff manages torque split front to rear and how the VDC manages wheel spin and delivery of torque to each wheel. As we know so well, Subaru builds a compromise vehicle, Not too bad on the bitumen and OK in the rough stuff. It stands to reason that the ECU will be programmed in the same way, not excelling at anything. If it was possible to break into the code in the ECU and rewrite it, it should be possible to get the system to behave more in a manner that suits the style of driving you want to do.


The good news is, it is possible, it has been done and the person who did it can do it for you. Even better is it doesn't cost an arm and a leg.


I have just had significant modifications made to my SH Forester that should make a real difference to its off road performance. They are:

Engine - the torque delivery curve has been shifted down the rev range giving me almost peak torque from 1200 rpm with an increase in peak torque overall. Power is also increased.

Auto box - with the increased torque at low revs, the upshifts now occur at lower revs when the selector is in drive. This gives smoother shifts and should result in better fuel economy for general driving. Response to kickdown has been improved.

Centre diff - torque delivery to the front wheels has been decreased by 15% and therefore the rear has increased by the same amount during normal driving. When front wheel slip is detected or the torque from the engine reaches a critical point, the centre diff will now direct a full 50% to the rear wheels and maintain this until grip is restored to all wheels. This is effectively a centre diff lock except that a diff lock controller provides the 50% distribution even when the vehicle is not moving. A centre diff lock is a better option but this will do for now.

VDC - As discussed in many posts on this forum, VDC on later models of Subarus is better than nothing but falls short of an LSD and certainly a locker. The response time is too slow and momentum is lost before the brakes are applied to the spinning wheels. My VDC has been tweaked to reduce the response time. I'm not sure how long the delay is and as soon as time permits I will test it and see how it goes.

All of these improvements were able to be made on my car within 30 minutes. The difference is very noticeable while driving on bitumen and it cost me no more than 3 or 4 tanks of fuel which I should save over a period of a couple of years if the 10% improvement in fuel economy is realised.

If you own a Subaru with an ECU that controls even some of the functions of your vehicle you can make it do much better for very little cost.

Contact Matt McLeod - Throttle Happy Tuning.
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  #2  
Unread 28th April 2019, 03:58 AM
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Kevin Kevin is offline
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Indeed - they can do wonders! My son's Foz S (turbo) has been "tuned" and it sizzles!
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  #3  
Unread 28th April 2019, 04:23 AM
Beachworm Beachworm is offline
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I wish 7 years ago when I bought my Forester new that I had the knowledge I have now. I would have bought an S edition.
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Unread 28th April 2019, 03:54 PM
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Interesting how the ECU can be modified.

What I would like to know is if the clutch pack (MPT) won't be worn sooner with a different front to rear bias ?
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Unread 28th April 2019, 04:53 PM
daklakfoto daklakfoto is offline
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Please pm info. I'm computer savvy but lives in states.

I've been looking toward this direction
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Unread 28th April 2019, 08:00 PM
Beachworm Beachworm is offline
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Quote:
Originally Posted by jf1sf5 View Post
Interesting how the ECU can be modified.

What I would like to know is if the clutch pack (MPT) won't be worn sooner with a different front to rear bias ?
From what I understand it should cause less wear as it now locks completely under heavy torque loads. I guess I'll find out as time goes on. My car has 170,000 Km on the clock so if there's to be a problem I guess it won't take too long to find out about it. I'll post any eventualities.
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Unread 28th April 2019, 08:56 PM
daklakfoto daklakfoto is offline
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Do you require to have cobb access or it just to plug into port and flash?
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  #8  
Unread 28th April 2019, 09:31 PM
Beachworm Beachworm is offline
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I'll explain the process as I saw it but keep in mind I'm no expert with either computers or cars.

I communicated to Matt how I was using my car off road. I also told him what I would like it to be able to do better. I asked for more low down grunt, locking of the centre diff if possible and a quicker reaction time from the VDC to avoid loss of momentum due to wheel spin.

Matt prepared some software ahead of time and met me last Sunday morning. He asked me to get into the driver's seat, he sat in the passenger's seat with his notebook computer on his lap and plugged into the OBD2 port.

He asked me to turn the ignition on and off a couple of times, start the engine and turn it off a couple of times. He then asked me to go for a drive. All the while he was doing things with the computer.

During the drive he asked me to stop and do a full throttle start and take it to the full-throttle change point from first to second gear. We drove around a bit more while he explained to me the changes he had made, not in terms of what he had done, but what the engine and transmission would now be able to do.

I hope this is of some help.
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  #9  
Unread 28th April 2019, 10:06 PM
daklakfoto daklakfoto is offline
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That sounds great. I hope he is closer or someone can do the same at where i live.
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  #10  
Unread 28th April 2019, 11:49 PM
ABFoz ABFoz is offline
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Did he use Subaru FreeSSM? I have been reading about it but haven't actually tried it on my vehicle. It can change shift points on D, as well as other Subaru things. Cheers.
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