Why, pray, would you want a faster Subaru Legacy Turbo?

I want to squeeze some more juice from my 2011 Subaru Legacy engine and more boost from its turbo counterpart. PHOTO | COURTESY

What you need to know:

  • Think hard about it before diving right in because motor vehicle modification is exactly like a narcotic addiction: a slippery slope that is extremely difficult to wean oneself off of, and a bottomless money pit devoid of profit that may strain relationships with friends and family.

  • It also turns you into a caricature of your former self since what started as a recreational indulgence turns into an all-consuming obsession, and there will never be enough: you just want more … and more … and more.

Hi Baraza,

I enjoy reading your articles, continue with the good work. I have owned a 2011 Subaru Legacy Turbo for about six months now, and I am really surprised at how fast the car is — it is so fast, I have never been out-accelerated (I hope I never come across an Impreza STI or the Evo). Anyway, I want to squeeze some more juice from that engine and more boost from its turbo counterpart. Which basic and safest modes could I do at stages 1 and 2 and how much will they roughly cost me? I also want to instal a sunroof on it, a manual sunroof that I can lift and close manually, nothing major. Can it be done in Kenya? Looking forward for your reply.

Hello, Fellow Legacy Owner,

First off, as a fellow Legacy owner, you will allow me to dissuade you from participating in competitive driving on public roads with your high-powered and ultimately multitalented motor vehicle. We left those shenanigans to take our hot-blooded lead-footed antics to the track. Nobody, but nobody, is allowed to race on public roads, Impreza and Evos in the mirror notwithstanding.

So you want more juice out of the car? Why do you want more juice out of the car? Can you handle more juice out of the car? Do you need more juice out of the car? I think not. However, you asked, so I will tell.

Stage 1: Modifications are stand-alone adjustments and typically involve installation of a custom engine map, or tune, among other things. You do not need to change or upgrade that many components, though a racier suspension and bigger brakes will help you channel and corral that extra power more competently, but as I said, these mods are stand-alone, you can perform one and omit the other. You could instal a high-flow exhaust and a cold-air intake or cone air filter element. The engine map should handle the boost levels in the turbo, though I will not go into the details of mapping because it is a dedicated subject not easily condensed into a few dozen words. The cost implications heavily depend on who does the work, the brands and quality of components you buy and of course the extent of the modifications, so I don't have an exact number for you, but let's just say it starts at almost free (manually adjusting the ignition timing or mapping the car yourself) to very low five figures (or even high four figures) for things as mundane as a cheap induction kit to something in the low-to-mid six figures for upgrades that involve several systems covering everything I've listed.

Stage 2: As the name implies, turns things up a notch. It involves more extensive changes and is therefore a lot more expensive. The reason is that the modifications done are mutually dependent, i.e. for one change to work effectively, it needs another change to be performed elsewhere for the whole set-up to jell. This time you may need to change the heads, injectors, cams, clutch and fuel pump for bigger, beefier and more finely machined ones because you will have a more aggressive engine map and an aftermarket turbo. Just like Stage 1, the costs heavily rely on the scope of work, the quality and brand of components (turbos can get quite expensive) and whoever is doing the work, but the numbers you are looking at are in the high six figures once everything is factored in. Sometimes, this number creeps into seven figures.

So, again: do you really need more juice? Have you fully harnessed the current output and found it wanting or are you like many people I know whose primary priority is a sensation similar to a passenger jet at take-off every time they see a straight road and to Hades with everything else? Think hard about it before diving right in because motor vehicle modification is exactly like a narcotic addiction: a slippery slope that is extremely difficult to wean oneself off of, and a bottomless money pit devoid of profit that may strain relationships with friends and family. It also turns you into a caricature of your former self since what started as a recreational indulgence turns into an all-consuming obsession, and there will never be enough: you just want more … and more … and more.

As for the sunroof … well, it can be done. It has been done, but I don’t know who locally has the requisite competence to handle the task with appreciable aplomb. Try one of the more reputable body shops recommended by friends and forums.

What fuel octane rating is best for my vehicle in terms of safety and performance?

Hi Baraza,

Thanks a lot for the lots of help you have offered to the growing number of motorists and wannabes. I own a 2011 Subaru Legacy Turbo with a compression ratio of 8.5.1 — 9.5.1. With that in mind, what fuel octane rating is best for my vehicle in terms of safety and performance? I also need to know the exact octane ratings of our local fuels, such as the Total Excellium, Shell Fuel Save and Shell V-power.

Fred.

Hi Fred,

In terms of safety and (mostly) performance, of course the best octane rating is the highest you can find. After all, despite the normal-seeming compression ratio in your engine design, it is still turbocharged, isn't it?

Engines can run on a range of octane ratings provided the lower limit of this range is not so low as to be classified as the no-longer-existent-for this market “Regular” fuel. That would be so explosive, I think it could light up just from exposure to bright sunlight — so exposing it to a modern turbocharged engine would have you sweeping up bent and twisted engine components from underneath your car after just five minutes of idling as the result of detonation and knock so bad, it would deserve its own series on Netflix. Fortunately, most fuel nowadays is not that tragic because nobody wants to stock regular fuel despite the proliferation of motorcycles … motorcycles and chainsaws are what would run this volatile brew safely, but again mixed into a foul soup called “two-stroke”, which is a whole other story, cars used to run on regular back before history was written, but as compression ratios went higher, so did the need for fuel with stronger anti-knocking characteristics and eventually regular became obsolete.

Now, what usually happens in a modern engine such as yours is that the engine adapts itself according to fuel standard. It starts off at the maximum setting, which should be the manufacturer’s default and then uses the knock sensor to start adjusting parameters such as ignition timing, boost pressure and injector pulses according to what is happening inside the engine. Let us say, for instance, you feed your car 98 RON fuel, which is good enough for any road vehicle. The ECU will run high timing, giving the car good performance and may not need to adjust anything. Let’s take another example where you fuelled with 95 RON or even 93 RON. The same engine will run high timing but at one point it will start detecting knock (detonation) upon which it immediately retards the ignition timing by a small degree. If it still detects knock, it will again retard the timing and keep this up until no more knock (or minimum knock) is detected, and that is the set-up that it will run on to keep itself safe. Retarding the timing may be accompanied by lowering of boost pressure or in some cases the turbo goes offline temporarily (happened to me recently). These adjustments happen so fast and so subtly you will not notice them unless moving from one extreme to another, and even then, most people may only notice a very slight flagging in performance. Knock detectable by human senses is usually a prelude to disaster if not taken care of urgently.

All this means the engine will run on a variety of octane ratings, but these ratings have both upper limits and lower limits for your engine. There is an octane rating below which there will be significant knock even when the timing has been retarded completely (“regular” fuel, haha), and this is what kills engines — then there is an octane rating above which nothing improves and you are just wasting money. Your engine should operate relatively safely between these two bookends, which is where most pump fuel lies.

Speaking of which, your second query on octane ratings of local fuels. There is a bit of disparity in results derived from my cursory research, but whatever stood out is the same thing I have been saying: Shell V-Power has a slightly higher octane rating compared to premium, or what you call “super”. I don’t know what exactly Shell FuelSave is made of and how much fuel it saves over ordinary premium, but I know it is not much different from premium … which probably explains why it costs exactly the same. This applies to Total Excellium as well, only that I know Excellium straddles the area between V-Power and FuelSave in that, like V-Power, it too contains detergents and extra cleaning agents to give your engine some much needed colonic irrigation, but like FuelSave, it costs exactly the same as premium because it offers no extra octane. Got it? Right, now the numbers.

There are public relations allegations and there are truth-seeking verification boffins with advanced Home Scientist chemistry play-sets and then there are about five million conspiracy theorists lurking within the confluence of the two groups’ Venn diagram. It is hard to tell who is who, but the general picture painted is this:

Shell V Power: 93 RON — 95 RON, depending on who you ask

Shell FuelSave: 91 RON — 93 RON

Total Excellium: 91 RON — 93 RON.

I give ranges rather than absolute figures because the spokesmen for the oil companies will say one thing, the guys with the titration burettes and Bunsen burners will say another, then a budding tuner will blow his engine when running too much boost and blame everyone for selling bilge water instead of petrol. But at the end of the day, if money is not a problem, go for V-Power. It’s the safest bet.

I want a fast Sub, how about the BR9 Wagon Legacy GT Turbo?

Hi Baraza,

Thanks a lot for your work, it never goes unnoticed. I have been trying to get your attention but it seems that it is really limited. I hope I will be lucky this time. My main purpose for writing is to enquire about the new BR9 Wagon Legacy GT Turb ((2009-2012 model) five-speed automatic. I plan on buying one soon but I’m not sure how it compares to the new Forester XT SH9 Turbo in terms of performance and acceleration. Is it a fast car or should I look elsewhere if I want a fast car. I really love fast cars. If you have driven one, please share the experience too. That said, the Legacy Turbo is mostly rated at 265hp, but recently, I discovered that Japanese models boast 281hp, while US models boast 265hp. With this in mind, what is the horsepower rating that we get from the new Legacies sold at our local car yards?

Fredrick.

Hi Frederick,

The BR9 Legacy GT is a fast car, but if in doubt about whether or not it outruns a SH9 Forester XT, you could allay those fears by going for another BR9: 2.0 GT DIT (direct injection turbo) from 2012. It is probable that engine won’t last, what with our fuel quality discussions above, but before it goes poof, no stock SH9 is going to keep up with your 300 factory donkey strengths. That thing must be really fast. I want one, with a six-speed manual.

I’m not sure what power our local-dealer Subarus put out, or if they even sell a turbo version, but if you are talking about car yards, then that means imports, which in turn means they are putting down whatever power the respective market they came from was allocated, that is, barring other factors that affect output, such as altitude, age, condition and, ahem, fuel quality. That means for a Japanese import, you get your 281 (really?) drays and for Australian you get 25 …. or 300 for the Japan-only DIT.