How not to get ripped of buying car tuning goodies!

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Kerbsidemotors! guide to not getting ripped of when trying to get your car to go faster by buying stuff on the cheap off eBay!

This guide is a bit long so if anyone wants to get a drink or anything go before you start reading!

We sell go faster parts for cars on eBay. We often hear horror stories about people who have bought something they believe may have improved their car only to find they have bought rubbish. So here is our guide to avoiding buying rubbish!

For a car to go faster or get better fuel consumption it needs 3 things to happen.

1. The air and fuel must get into the engine easier/faster/cooler. (I.E. an induction kit will place less restriction and keep the air cooler going into the engine)

2. The engine must burn more of the air/fuel when it burns it. (I.E. Better spark plugs will burn more of the mixture)

3. The exhaust gasses must leave with less resistance. (I.E. a fancy racing manifold will help the exhaust gasses out quickly)

These are the only things that will physically increase BHP. There are also things that will help you make better use of the power you have like electric fans or low drain alternators but they do not actually increase BHP.

Anything else that claims to increase BHP is probably rubbish. Here are a few examples...

Mod chips Vs Reprogrammed chips.

Both types are regularly available on eBay. 

Mod chips work by 'fooling' the ECU into using more fuel or advancing the ignition. A popular type is placed on the mass airflow sensor on the cars air intake. The Mod chip causes the sensor to tell the ECU it is freezing so the ECU thinks 'Ah, better pump more fuel in!'. Good idea you might think but the problem here is as the sensor is incorrect it means all the other sensors are incorrect too which leads to your cars catalytic convertor failing because too much fuel is being burned. A dodgy cat is an expensive MOT fail. The other type of mod chip fools the ECU into advancing the ignition. Short term this will not do too much damage but over a length of time or if you drive like Colin Macrae it will burn a hole in the centre of each of your cars pistons and render the engine useless. If you have a turbocharged car this will happen faster. My advice is to avoid fitting these 'chips'. I know they are temptingly cheap but they will do your car in big time!

Reprogrammed Chips. These work by replacing your cars RAM chip with one with a different program. The program will have slightly different fueling and timing settings. So like the chips above it will advance the timing and pump more fuel in. The difference is the chip does it the right way! It will not burn so much extra fuel or advance the timing so much that damage will occur. Many are from legitimate car tuners like 'Superchips' or are copies of them.(Which is fine providing the maker has copied it correctly!) As the whole program has changed all the other sensors will still work fine so the car will still be perfectly drivable. 2 types are available, the ones where you change the chip or the 'tuning box' type (mostly for diesels). I can say from personal experience both types (bought off ebay) work without damage.


A turbocharger or supercharger works by forcing more air and fuel into your engine. The more mixture in your engine the bigger the bang and the more power there is. Easy! However, scammers have got onto this too. If your car doesn't already have a turbo, you can buy a kit with a turbo, a different exhaust, an intercooler, a reprogrammed ECU and all the stuff to fit it but you will still need to take the engine apart and have a machine shop change the compression ratio.

But recently I have noticed people selling fan kits that fit into the air intake and blast air in. Sorry but they don't work! Turbos and superchargers will force mixture in at several BAR of pressure. A fan in a box doesn't have enough puff! Despite their claims, the motor in these units spins no faster than 3000rpm. A turbocharger is roughly the same size but to generate any sort of power increase it has to spin anything up to 10 times that. If the unit is not spinning as fast as the air going in usually goes it will restrict the flow and actually cost you BHP. To put it bluntly, if these worked so well why would people go through all the hassle of developing turbochargers and superchargers when they could just stick an electric motor on?

Induction kits and air filters.

An induction kit is a kit with a new air filter, a big intake pipe (Usually metal) and the clips etc. to fit it. It should replace the intake system right up to the fuel injection. An air filter kit is an air filter, sometimes with a fitting kit and sometimes some ducting. Don't buy one thinking it is the other. K&N do replacement element kits where you replace the cars air filter element with their one. I have seen these sold as induction kits. They are not. An induction kit will increase your cars power and noise more than just an air filter.

Sports exhausts.

Go faster exhausts do make your car faster. They make it sound better too. Sports back boxes will make your car sound sporty too but they will not necessarily make it faster. The fact the tailpipe is larger and it lets the gas out easier (that's what makes it louder) might increase the power but the extra big tailpipe its self robs the car of its backpressure that helps suck the new air and fuel into the cylinder (called pulse tuning) which costs power. Anyone who races motorbikes or go-karts will tell you how important pulse tuning is! 

Ecotek valves

They are about £50 each so not many people can afford to break one open to see how it works...

BUT I HAVE! The valve is placed usually in a breather or vacuum pipe (like the one going to the brake servo). I am not sure how they manage to get the power increases quoted in their adverts because all that is inside them is a bit of gauze and a small one way valve. They do not pump more fuel or cool air in, they do not cause the ignition to burn better and they do not help the exhaust gasses out. Either me, every tuning expert in the world ever, everyone who has studied physics and everyone who has smashed one up like me is lying or Ecotek are!

Dump valves.

If you have a turbo you can change various things by changing the dump valve. Fit the right one and you will have better throttle response and perhaps more power. Be very wary of those sold to '...make your car sound like a rally car!' Simply because when you hear a rally car on the telly making that noise from the turbo it isn't the dump valve! Rally cars do not have dump valves! The noise is the boost pressure being forced back through the turbo. Like farting wearing very tight trousers! This isn't good for the turbo but it is good for performance if you are trying to win the stage. But as we cannot afford to replace the turbo every few hundred miles, its best to leave your dump valve connected. Just don't pay extra to sound like a rally car!

Fuel and oil additives.

I am not saying if you use an additive you will not notice a difference because you might. Fuel cleaner additives can clean the fuel system and restore lost performance but they will not add more power than your car originally had. Octane boosters may increase the performance by making the fuel burn better but only if your engine has been set up to run with higher octane fuel. Otherwise nothing wil happen! Friction reducers (usually put into the oil) may decrease the friction inside the engine but only if all the additives already in the oil have broken down. They will only break down if you don't change the oil regularly. My advice is to use good quality oil (Catrol or similar) and change it regularly. This will keep your car running nicely and cost far less in the long run rather than relying on unproven additives. 

The basic rule with tuning is (like everything) if it sounds too good to be true it probably is!

Few hardened engine tuners woul notice the difference a 5bhp increase would make. Most drivers don't notice anything less than a 10bhp increase. So if your car feels faster because you gave it a bottle of STP or changed the dump valve for one that sounds like a rocket taking off I am afraid its all in your head! In my experience the only way to increase a cars performance is to change one of the 3 points I made to begin with. Sometimes it is cheaper to sell the car you have and just buy the sportier version than make what you have go faster. Sorry but I am afraid its all true!  

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