As a "rocket scientist" you know as well as I do that the catalyst is merely just that, a surface prepared for the efficient chemical conversion of partially burnt hydrocarbons.

So no fuel on them, as they have converted it !

dunx

I would be interested to know as well, is OE best or do you go for an aftermarket version? :wonder:

I think the cats require extra fuel/air in order to keep (more completely) burning.
I presume this is supplied by a degree of exhaust-intake valve opening overlap.
Can anyone in the know tell me if this is right?
I believe this is the source of the increased fuel consumption associated with cats.

And like you they spout a message no-one is interested in hearing..... ;)

dunx

P.S. I would invite you in for a cuppa tho'...... as you could explain how all that extra horsepower has caused my air-con pipework to fail ! :lol1:

I'd be suprised if he did, OE is best afterall........... not :lol1:

Show me a 550 BHP 30 mpg Impreza which has been tuned by Prodrive and offeres a decent warranty .....

pmsl

WTF?? :freak3:

Neat petrol on the Cat honeycomb will explode and shatter .... my question was - "Where is all this petrol that Subaru pump into the cylinder which isn't burnt?" .... because it isn't in my exhaust pipe!

My front pads lasted around 65,000 miles I seem to remember ... so, I replaced with Subaru Pads and Discs ... knowing at 130,000 miles they will be due for renewal again. Lesser Pads would not last as long ... so, not cost effective - it really is simple logic.

So, OEM every time is my moto .... why do anything else? Same as mapping, why turn your Subaru bullet-proof engine into a chocolate one? :wonder:

Pete - get an air fuel monitor on the exhaust while you are driving and you will see it show up in the figures that show the mixture of air/fuel that is coming out of the exhaust in the form of gas. Petrol isn't in a pure liquid form once it has gone through the engine and combustion process. I thought you would be able to comprehend that being an engineer and all that.

Or hook up the same monitor to the headers before it goes through the cats to see there.

Simple fact is that it is running very rich. This richness is costing power. So leaning it off slightly will generate more power for less fuel. The laws of physics that you seem to be quite keen to spout dictate that. (edit to say it may be chemistry for the pedants amongst us LOL)

Interesting that the re-mapped engines, returning 30 mpg, are doing what is the biggest enemy to these cars .... running LEAN!! :eek:

If Subaru run rich (as has been claimed here) to 'protect the engine' ... and a re-map removes that richness - then the re-map is running a leaner mixture - holy cr4p!! :eek:

I had my fuel pump fitted ready for my remap and i havent seen any icrease in mpg and im returning around 22mpg

And mappers have seen my afrs from my rr'd graph and its running quite rich so could do with leaning out about it so my off boost mpg will increase

What I have not heard yet ..... which (like the non-warranty issue) is clearly non palatable for some ......

I'll ask again .... What are the downsides of a re-map??

I'll give you one for free ...

1. The Warranty for your car is now null and void.

2. ?????????

Fill the rest of the list ...

Strange that .... a mapper saying that you could do with a re-map :lol: :lol:

You really are struggling to understand this whole concept or are you just trying to become famous for pretending to be the thickest person on here?

There is more than enough information and facts from everyone but you on here to enlighten you on this Pete.

Overly rich causes cylinder wall wear. Please explain to me what fuel ratio yours is running at and why that is best for it.

Still not answered have you?

What are the downsides of a re-map .... ??

It is a genuine question which everyone would dearly love to know the answer ....

Not really fella i was getting my afr's checked to make sure they were safe actually when i first brought it, who is also a friend so not just them trying to upsell a remap thankyou

A Freebie re-map then? Excellent :thumb:

lol i wish fella, i wanna go simtek so i can run maffless:)

If a car is past warranty then why worry?

Bob Rawle mapped my car, he always answers any question I have by phone or email, and recently checked my car over when I had a slight problem that turned out to be a boost leak, nothing to do with the map and sorted it for me, that is top class service as far as I'm concerned.

The only downside of having 550bhp and returning 30mpg is not using the 550ponies IMO :lol1:

suburu ran overly rich to be safe, for all fuels, and for the safety and reliability of the car. ANY ecu controlled engine can be specifically tailored to run more efficiently, or more power or both. Subaru along with all other manufacturers run a safety margin. I think people who remap for more power realise that it is harsher on the cars mechanicals, and drive accordingly, someone with 350-400bhp on a standard gearbox knows that hard launches will be harsh on the drivetrain, and in some cases cause failures. As for the claim that a remap for significantly more power will give better MPG cannot be true if it is based on an average MPG with an average style of driving, it can be true during certain driving conditions, say at a steady 60 before map, and the same after the map, as the remap has been finely tailored to the fuel and mods of that car, whereas previously it was a generic safe map running slightly rich. In my experience, my extra 60bhp has resulted in an average of 5mpg worse economy, i don't use my car to commute, and my tank of fuel is usually used with a mixture of spirited weekend driving and some shopping/taxi work for the missus. I daresay that a constant 60mph motorway cruise would make little difference and i would not be surprised if the MPG was an improvement over standard, neither would i be surprised if it were worse.

Another point .... say your car goes into Subaru for a Service/work to be done .... they may wish to interrogate the ECU - will they not spot that the map is all about face and messed up?

Also, if it gets an 'update' by Subaru on the ECU - will that not overwrite any re-map?

I'm thinking of a scenario where a mapped car is sold, the new owner takes it to a Main Dealer for some work and the new proud owner is told it has been fooked about with - the new owner may not be very happy at all ... now he has a modified car which may be so unreliable that he may as well have bought a TVR or Alfa!! :eek:

i don't think a remap will turn it all italian electrics-wise, or cause bits to fall off a-la-"made in great britain". lower reliability will be purely down to the mechanical sympathy offered by the driver, and the same driver could also shorten the life of a standard car. It's all about how much you care for your car. but yes, a dealer could spot or alter the map.

What are you saying Pete? That re-maps are the metaphorical equivalents of The Emperor's New Clothes!

Only downside I can see is being a bit lighter in the pocket but offset that against the improved driveability and I think it is pretty good value.

Obviously if you start making huge modifications to the car and taking them way outside of the original intended power then the life expectancy of some components can reduce - it doesn't take a rocket scientist to work that one out and anyone that modifies their car accepts that. But most here make some modification to the car to make it unique to them, some buy the factory dealer fit parts or some save a substantial amount of money getting aftermarket parts.

Just because someone has remapped their car does not make it any less reliable (unless done badly). IMO it will make it safer like comparing a tailor made suit to an off the peg suit. One fits better.

Having a car with power available doesn't mean you have to use it all as you well know and anyone that canes their car everywhere would be foolish to expect full reliability - that would be the same for someone with a 100% std car or someone that has modified it. Same goes with track or competition cars - there are being driven to the extreme in a lot of cases.

This is where the difficulty comes in, you see.

If there are no downsides whatsoever to producing a map which, gives 550 BHP when you want it to, and 30 mpg when you don't, then I'm a monkies uncle!!

Clearly, there are some downsides ... or Subaru WOULD do it - make no mistake!! Why produce a car which has, say, 270 BHP and returns 22 mpg when there is a hobbyist who can transform that into 550 BHP and 30 mpg?

Nah, there's something really fishy here .....

I suspect that a re-mapped car is going to go bang/wrong much sooner than a standard mapped car .... of, course, that may be a price worth paying by some (I wouldn't imagine by many though?).

The extra strain on the gearbox, diffs, bearings, pistons, etc. must shorten their life .... I guess this is why buyers don't want a re-mapped modified car and they have to be sold very cheaply to 'get them away'?

My 2003 wrx was remapped my Duncan, it had prodrive pack when it was put on a rolling road the results were poor and the car was running very rich, after a few carefull choosen mods and I remap the car now feels smoother through the rev range, I will also add my mpg is so much better than running the Prodrive pack, this was the same in my mk4 gfi I hade a revo installed and once again the car was alot smoother and once again returned alot better mpg. So to be honest the only downside I can see to haveing a remap was my wallet lol, and the commen about having to sell the car cheaper with an after Market remap what a load of ****,

Hey Pete.

You still haven't actually answered anything that has been asked of you regarding power and AFR/Lambda.

It appears the insight you're missing is how can more fuel result in less power, especially given there is a higher calorific value of fuel going into the cylinder. I can understand why you're not picking up the big picture on this one.

You asked about what happens to the extra fuel. Some of the fuel will NOT BURN and be released as hydocarbon gas into the atmosphere, some will do a partian burn, split and recombine with other constituents that are not involved or are by products of the main combustion. However one problem is that you don't always know how things are going to work out, and a theoretical mass balance doesn't always work. You'll have to forgive me for being so vague, it's been 15 years since I studied engine combustion.

Taken to extreme you will get enough unburnt fuel through the exhaust to be able to recondense and drip out as a liquid, it doesn't burn because there is no free oxygen left to burn it with.

Any lambda below 1 means there is excess fuel in the exhaust stream, so you've already posted about situations where excess fuel is present in the combustion process.

well.!!!!??!! depends but normal day to day driving should see abit of improvement on MPG. BUT you also need to consider of the reason why remap cars needs an uprated fuel pump tho..