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Discussion Starter · #1 ·
I've bought a cat bypass for my VVC but have since read that this will infact sap the BHP instead of gain... Any opinions would be welcome. I have a K&N and 52mm TH - any other budget (ish) suggestions to increase BHP ?
 

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scuzza said:
I've bought a cat bypass for my VVC but have since read that this will infact sap the BHP instead of gain... Any opinions would be welcome. I have a K&N and 52mm TH - any other budget (ish) suggestions to increase BHP ?
Without spending serious money, you've done pretty much all the reasonable mods, a cold air feed for the K&N mounted down the front of the spoiler will give another 2 or 3 hp, and that's about it. Stripping out any unwanted extra weight will help performance. Don't bother with the de-cat option, technically makes the car illegal as it can't pass an MoT test without one. Other thing to avoid is the miracle resistor chips on eBay, they will destroy your engine and/or ECU (whichever happens first).
 

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You could port your manifold and downpipe, diy job. Peformance exhaust and proper enclosed indcution kit will give some gains.
 

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Discussion Starter · #4 ·
thanks guys - what is "porting the manifold" - with regards an uprated exhaust, is that a lot of £'s for very little BHP gain. I do have 2 pipes from the bottom of the car feeding cold ait to K&N - is it also worth taking pipes from the side vents too - so for in total ?
 

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Porting the manifold is grinding out the inner welds to improve gas flow. If the welds on an MGF are typical Rover welds then they will be pants.
Do a search for manifold porting on this forum.

Your K&N will be robbing you of power no matter how many CAF's you get to it, especially on a rear engined MGF.
 

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Apparently on an F the K&N is a worthwhile mod, not so much on the TF as the air intake is better on the TF, and apparently crap on the F.
 

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Open cone filters are not a worthwhile mod on ANY road car as far as performance goes. They lose power and that's a proven fact.
An decent properly set up enclosed filter will net some gains however.
 

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Discussion Starter · #9 ·
i don't buy that - my car is absolutely 100% defininitely quicker since i've had the K&N fitted
 

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Discussion Starter · #11 ·
i've just googled it and can't find one set of test results that doesn't come to the conclusion that you get a significant BHP gain with a correctly fitted 57i
 

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a well positioned open filter will gain power, a badly posiitioned one will lose power, without seeing where the filter is noone can say for definate either way.

I'll accept that its gained power as you are the only person who has driven the car
 

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scuzza said:
when you say well positioned do you mean the pipework positioned correctly ?
Needs to be well positioned to draw in cold air, and if it is drawing in more cold air then it will improve the performance of the engine. If it's just drawing in more hot air from the engine bay then you'll see performance suffer. Air density and stochiometric stuff.

Ideally, in a perfect world*, you need 12.5 Oxygens for every 1 of Petrol and in one cubic foot of air at 22°C there will be less Oxygens then there is in one cubic foot of air at 18°C. Now your engine will draw x number of cubic feet of air per minute and if it's not receiving enough Oxygens in that cubic feet, not all of the petrol can combust as there's nothing for it to react with, as a result the engine reduces the amount of fuel entering the engine and you loose a little power. Increase the amount of Oxygen entering the engine and the ECU will increase the amount of fuel entering the engine also, so as a result, you'll get a few extra horsepower.
 

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Discussion Starter · #15 ·
by well positioned do you mean directly into the cone and out the bottom of the car slightly angles forward ?
 

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Mate it's a fact that open cones lose you low down power because of heat soak. As for these test results, find me an independent test of a road car that has gained anything significant from an open cone apart from the manufacturers testimony.

It is well known that open cones will suck in air from where there is the least resistance, I.E. the engine bay. A CAF is absolutely useless when the car is stationary or the car is travelling at low speeds.

An engine can suck in a hell of a lot of air even at low speeds and your CAF will not be able to provide this amount air it requires, so it will source it's supply from the area surrounding it, the hot engine bay air.

You may gain a little at higher speeds, but it would have to be a significant amount of air that is being pushed through the CAF for it to be of any benefit.
In fact most of the air that the cone relies on will still be from the engine bay, however at speed there will enough air flow into the engine bay for the filter to benefit from.


Enclosed systems work much better because they are somewhat isolated from the effects of heat soak due to the fact that a properly routed CAF will draw ALL of it's air from the cooler air outside of the engine.

This is fact unless you are going to tell me that your engine produces more power from hot engine bay air?;)
 

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scuzza said:
there are loads of indy reports when googling but can't be ar5ed to paste them !!
I said road car....!
I don't need to argue about this I've seen enough member posts who have rolling roaded to prove the fact.
Think what you will, but the facts are there....:slap:
 

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scuzza said:
ok - here's just one - they state that the VVC benefits most. There really is loads od test data if you google it - these are the facts i believe - can you post here a link to one survey which states they do not increase power ? I'd be interested to read it as i've not seen these negative "rolling orad facts"

http://ourworld.compuserve.com/homepages/robmidgleybell/conclusi.htm
These sites only state the benefits of a filter that is tested when the car is moving at speed and not from a launch situation.

Search on this site you will be enlightened.
 
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