Let’s clear the air on these noisy Subarus

Hi Baraza,
I have this weird obsession with tuned WRX /STi monsters but every time I praise them near my ‘ethical’ and ‘professional’ friends, they dismiss the cars as anti-social and ‘bad boy’ rides.

What’s even worse is that many of my friends deem the cars as the Number One killer on our roads, and that owning one is embarking on the pathway to your grave. What’s your take on these observations? Once you are done with that, please tell me:

What’s the difference between a Blow Off Valve and Anti-lag and N2O? What negative implications have they on the engine and a car’s life span?, and has NEMA raised (or likely is it likely to raise soon) any concerns about turbo loud exhausts?

Steven Maina.

When they say “anti-social” and “bad-boy”, are they actually talking about the car or do they really mean the owners/drivers? There’s nothing wrong with the WRX Subaru (this cannot be said for some owners of these cars though).

It is a mighty fine car, affordable performance in a compact, user-friendly package, but unfortunately it has attracted a client base that, the less talked about, the better. You would not believe the things a section of this “client base” said about me the day I declared that I enjoyed driving an Evolution more than I did an STi.

Those friends that allege the WRX is the No. 1 killer on our roads: ask them for proof. Where are they getting their figures from? And if this was true, then was I being insulted by ghosts a few weeks ago?

Logic demands that most of those WRX owners would have been a goner by now. Getting an STi is not a short-cut to an early grave, unless of course a person’s driving skills are worse than terrible, in which case any car will kill that person, not necessarily a Subaru.

The BOV is used to “dump” compressed air into the atmosphere (hence its other name — dump valve) when the throttle is closed. This prevents compressor surge, which could damage the turbo.

Compressor surge occurs like this: when the throttle butterfly valve is closed, this traps incoming air, which is under high pressure (it is coming from the turbo). Back pressure is created as the air tries to expand backwards into the turbocharger, and this can slow down the compressor wheel to undesirably low rpm, or even cause it to stall, creating a lot of stress in the turbo.

The disadvantage with having a BOV located after the MAF sensor in the air channel is that every time the BOV dumps air, the car will run rich since the compressed air has already been accounted for by the ECU (which receives instructions from the MAF sensor) and fuel dispensed accordingly.

Plug fouling and clogging of catalytic converters are the more immediate outcomes of this. A cure for this is placing the MAF between the intercooler (if so equipped) and the throttle body.

The anti-lag system is used to eliminate turbo lag, the instance where there is a flat spot before the turbo starts spooling. It does this by allowing an air-fuel mix to be in the exhaust manifold (when the throttle is closed) outside the engine block but before the turbo fan vanes.

The heat in the exhaust manifold ignites this charge and the resulting explosion forces air into the turbo, keeping it spinning even when the throttle is closed. When the throttle is opened, the turbo will still be spooling, so lag will have been eliminated.

The biggest disadvantage of ALS is shortened engine and turbo life because the force of the explosion in the exhaust duct is extremely large and places a lot of stress on nearby components.

To close it off: if NEMA enforces drive-by noise laws, all I can say is good luck to them as they try to catch the perps. I see them using DMAX pickups which, everybody will agree, is no match for an STi under full power, BOV hissing and ALS popping….

Dear Baraza,

Thank you for your advice and informative read. I own a Subaru Impreza 2004 GG2 a with manual transmission. I have a problem when it comes to taking steep inclines from stop.

I have changed the clutch and pressure plate (all original parts) as recommended by mechanics but the problem still persists. I have now been told that the problems is because the car uses a Cable Clutch System and not the Hydraulic System. Is there a solution to my problem? What is the difference between these two systems?


You do realise that you have not told me what this “problem” is. You just said you have a stick shift Scooby and you “have a problem” with hills. Describe the problem. The cable setup is used in mostly old school vehicles, and a cable is used to connect the clutch pedal and the release forks within the clutch mechanism.

With a hydraulic clutch, a fluid and lines (small-bore pipes) are used to transmit foot power to the release forks without losses, since the hydraulic fluid used cannot be compressed, so it does not absorb energy (hence the name hydraulic).

The cable setup is prone to cable snags (jamming) and snaps (breaking), while the hydraulic system is susceptible to leaks and air locks (air is compressible).

Thank you for your informative column. I own a 2002 Toyota Fielder 4WD that I crashed months ago and since then I have been struggling to restore it to its pre-accident condition. So far I have solved a lot of the issues that developed after the accident but a few major ones still remain. They include:

1. The CHECK ENGINE light stays on throughout. One electrician once checked it and in fact it disappeared for a few days, but was back on when I next started the car.

I sought clarification and he sent me somewhere to do “re-programming” which worked, but with a similar result. Now they advise me to replace certain sensors which do not come cheap. Do you agree with this prognosis?

2. The AIRBAGS CHECK light stays on throughout. Is there a chance I’m driving a car without air bags or is it just a case of wrong fitting? (NB: The dashboard was changed after the crash).

3. The car is awful on the road. Occasionally it performs just well, but most times (especially in the morning) the car lacks power so much that even Vitz’s pass me.

This is worse when climbing a hill. I have tried to observe the car keenly and I realise that (a) The REV GAUGE on the dashboard is almost always beyond 3,000rpm. (b) The SPEEDOMETER CLOCK on the dashboard does not go beyond 80KPH.

(c) The car emits an unusually loud roar when running and even when idling (the windows rattle when it’s idling). (d) On the times when it emits the loudest roar when running, I realise that there is no shifting that takes place in the transmission. The rpm at such times also goes beyond 3,000 which I think is unusual.

Sir, what is wrong with my ride? Could it be the gear box, or do I just need a throttle service as one mech told me? (He claimed the problem is that the engine cannot pull in enough air, thus is underfed of oxygen). Please help. I am desperate.


1. First, find out what that Check Engine light is all about. Don’t cure the symptom, find the problem and solve it. I cannot “agree” or “disagree” on whether or not you need to buy “sensors” (which sensors are these anyway?) until I know what the engine is complaining about. Come back with a code, then we’ll take it from there (including the flush, or “reprogramming” as you call it).

2. Yes, there is a strong likelihood that the airbags may be dysfunctional, or missing, or simply were not connected when the new dash was installed.

All these will make your car tell you, via those tiny bright instrument lights, that your airbags need looking into.

3. See 1 above. I believe the two are connected somehow.

Hi Baraza,

Most people recommend Robs Magic spring coils and Monroe shock absorbers, but would you recommend the non-branded heavy duty Chinese coils and shocks, especially for the rough Kenyan roads? What advantage do the branded spring coils

involving steel. Also, of late the steering wheel of my car is stiff to turn when driving. I have had wheel alignment and balancing and the tire pressure is okay. Could this be connected to worn out shocks?


There is a lot more to coils than meets the eye. It may just be a foot-long bit of twisted metal, but the processes involved in “smithing” that metal is what makes the difference.

I remember an ad for the second generation Land Rover Discovery that alleged the metal in their coil springs underwent tensile stretching and compression 10,000 times, was alternately chilled and superheated for a week (or something) and finally blasted with millions of tiny little balls non-stop before being forged into a Discovery coil spring.

Obviously not everybody does that, and there must have been a reason for Land Rover to brag about doing it. So a coil spring is not always the same as the next coil spring, in spite of appearances. I will not dabble in brand names just yet, but yes, different brands have different qualities, the most important being brittleness, energy storage (spring rates and stroke room) and life-span.

The hard steering is not necessarily down to bad shocks. Maybe your power steering fluid has run low. Or there is a problem in the steering box, or the steering geometry is off…

Bwana Baraza,

Thanks for your good advice. I read you regularly. Most of the cars imported into this market years ago had manual gearboxes and were carburetor injected. However, with the advent of EFi and VVT-i

technology, these cars have been very hard to re-sell, with a lot of people preferring the EFi technology. What are the advantages of either technology over the other?


In this day and age, there is hardly any vehicle still being manufactured with a carb-fed engine. EFi is better than carburetor-injection for many reasons, chief among which are improved fuel economy and reduced emissions.

Carburetor engines are also much harder to tune (the carbs themselves actually, not the whole engine), more so when it comes to altitude compensation.

Then there is a tendency of carb-fed engines not to rev smoothly throughout the entire rev range (a common affliction in performance cars); more often than not there is a “dead” spot somewhere (usually in the mid-range or towards the top).



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