Just my opinion

More power does not mean more fuel - a standard map producing a given power does not mean it is running effieicently. As other have mentioned, the generic map for mr. customer has to allow for many factors - poor fuel, poor driving, different climates and terrain etc etc so its fair to assume that a more specific map designed/produced to increase power can be more effiecient and just as safe given certain guidelines are followed - ie 99 ron fuel.

Like a fatboy would use more energy to walk upstairs than a fit athlete would running 60 yards, a well mapped car efficietly set up can porduce more power and use less fuel.

I await to be corrected from people whith more knowledge though...

Matt

Fuel Pump is pointless IMO ..... get a mapper to tell you what fuel requirements the re-map will need and judge accordingly - post the answer here, I'm intrigued (as I'm sure many are).

As if they are recommending a Walbro Fuel Pump - the re-map obviously needs much more fuel to work properly.

They cannot have it both ways, if the re-map improves fuel efficiency - then the standard pump will work well ..... if it isn't as fuel efficient as the standard map, then it's going to cost you big time in fuel costs!

Well i definitely got more MPG after my remaps, especially the initial one from standard to modified. What makes me laugh is my trip yesterday and today, Notts to Revolution in Gateshead, total trip i got 31.2 mpg. LOL, oh dear that is soo soo sad!
I obviously was driving like a Granddad on a Sunday :)
Mind you, that beats my posy 27 mpg in the week to work, etc.

the fuel pump is changed purely for safety. Lets say the original one was not up to the job, then you don't get enough fuel? Runs lean whilst you are up the revs and giving it some welly, say no more. Damage done and a big rebuild. I would far sooner buy the new pump and ensure a good flow than force the old one to "be ok".
And yes, i had my fuel pump replaced and i did get more mpg for a fact. Its more efficient.

Can't you see the contradiction in what you have just written?

It seems so clear to me .... you do realise that to improve the mpg you are using less fuel, yes?

And to use that less fuel you have bought and replaced the standard fuel pump for one which can provide more fuel?

My fuel pump is 10 years old and perfect for the job it has to do ..... your's needs less fuel than mine does!! :eek:

Can you see it, or am I wasting my breath? I'm being genuine here.

Lets put this in simple terms. To be more efficient your engine just needs to produce the power required to drive your regular routes more efficiently, for example, lets say your regular journey required you to accelerate to 70mph onto a motorway and then cruise on the motorway for 30 miles. To accelerate you maybe use around 70bhp (assuming a smooth 10 secs to reach 70mph).
At cruise you are maybe using around 30bhp.
As long as the map can produce this power more efficiently than the stock engine e.g. higher AFR for acceleration and more efficient timing tuned for the fuel that the user usually puts into the car. Then the car will be more efficient whether its maximum power is 200 or 400bhp.
When the car is thrashed using WOT and producing its maximum power then a 400bhp car WILL use more fuel than a 200bhp car (assuming something is not very wrong with the 200bhp car!). As the car will need to use more fuel during this fun time it will require an uprated fuel pump and larger injectors or it will run rather lean...

Other modifications such as removing CATs will also improve efficiency as the engine does not do the extra work forcing the exhaust gases through the catalyst.

When someone quotes a power figure, this is the maximum power reached at a certain rpm and is a very simplistic summary of how the car performs as a whole. In many cases we can drive our cars for weeks when commuting and not use this maximum number but rather the boring low load mid RPM cruise part of the map.

Hope this helps

Al

I would just like to add some further fuel to the fire, I had my previous Impreza - a Hawkeye 2.5 WRX remapped by Bob Rawle and it returned higher MPG figures. :)

I had the following modifications carried out to the car when it was mapped - RCM induction kit, 3 Port Boost Solenoid, Prodrive Uprated Fuel Pump, Prospeed 3" Exhaust System with a 100 Cell Sports Cat, STi Intercooler and hoses. :cool:

Before the mapping session the car was putting out in the region of 230bhp but after the mapping session it was 285bhp and considerably more torque. ;) It is a fact that the power delivery of the engine was changed by the mapping meaning that the MPG was increased. :D

The only reason that the fuel pump was changed was due to the fact that when accelerating hard then obviously more fuel is required and rather than have the standard pump struggle I changed it for a more suitable uprated item. :)

I did a MPG check on a mixed driving style drive from my house down to West Wales and back again. On the standard map it returned 25 MPG and after the mapping session it returned 26.4 MPG.

Both routes were exactly the same, taken at the same time of the day, in the same conditions and both used V Power, so what do you have to say now SSU? :lol1:

Take the blinkers off, you never know you might just learn something...:wonder:

i can confirm this as my mpg improved dramatically when i had a remap and my wagon was taken from 240bhp standard to 330bhp and i get over 10 more miles per gallon and this has been monitored as i personally couldnt believe it

So as a hobbyist and a qualified Automotive Engineer I guess that puts me nicely on the fence? :D

As I, Fleetwood, Off Your Marks and several other have all explained its about burning fuel more efficiently.

What do I have to say?

Quite simple really - you did not, repeat did not, travel from your house to West Wales with everything EXACTLY the same ..... that is quite clearly, IMPOSSIBLE!

You will have encountred different hold ups, different temperatures, different stop/starts, and a million other things were different ...... now, if you were claiming an increase in mpg from 25 to something like 40, then yes, I would have to take notice.

But a 1.4mpg increase? Ha Ha Ha .... sorry, that is more than accounted for in the slightest change of temperature!!

I'm struggling to get the basic facts of science and physics across, I can see that - but, I shall continue to try to throw the blinkers off those who are just not able to comprehend, yet.

Where did you do your Automotive Degree?

Cranfield?

Safe 340ish with 1.1-1.3 bar (gawd knows what the torque is... but it's plenty :D)

25mpg

300 mile range

Bath. Although strangely my supervisor is now Head of Auto Engineering at Cranfield.

How much would that set me back with the fuel pump. Will the car be any louder? What sort of torque would I be looking at?

You should stick to posting on subjects you know about - like Maryland bridges:lol1::lol1::lol1:

My MPG dropped slightly after a remap and I was a bit disappointed, but I did also put new GSD3s on at the same time and have since found out that due to their greater grip, the rolling resistance is higher, hence the poorer MPG. The same happened to the wife's Golf GTI when it had new GY tyres.

As far as the need for the uprated fuel pump, I think Cannon Fodder is right:

In normal cruising, you are using slightly less fuel after a remap, so no uprated pump is needed. But, if you give it some beans and the engine is producing 300bhp, then the original pump would struggle and maybe run lean, hence the need for a better pump.
It's only needed rarely, but when it is, it could save your engine.

Oh lordy, i've done Automitive Engineering for 6 years including a HNC.
I've learnt about mapping cars, dyno running ect....

Trust me when I say this, a remapped engine WILL return a higher MPG when driven steadily BUT it will dramatically fall when driven hard!!

Sorry SSU you do not have blinkers you have tunnel vision - you will not listen to reason despite forum members with far more expertise than you or I have pointed out the reasons for the flaw in your argument. :confused:

I can assure you that the route I took was the same as were the conditions, both runs were made on a Saturday evening and the car was kept within the speed limit at all times to ensure accuracy. The weather conditions were the same although I did not ensure that the atmospheric pressure was exactly the same. :p

In closing it is a simple fact that fuel burnt more efficiently will allow better fuel economy. :rolleyes:

Free flowing exhaust, free flowing induction all contribute to a more efficient engine(VE). That coupled with a remap may improve mpg slightly.

A question for the mappers, how many of you concentrate on the CL, cruise areas of the oem map.

SSU - you just seem to understand about the need for a large fuel pump, so here's a very simplified explanation to help you.

A std car starts with a max. power of 240 bhp. Fuel pump size is matched to max. power demand plus operating fuel pressure ( and a little headroom for wear n tear).
Fuel demand will be IRO 105 lph, so pump size is about 130 lph to account for fuel pressure (3 bar).
A newage WRX fuel pump is sized as 185 lph open end or 140 lph at 3 bar?

A remap to 340 bhp requires a fuel demand of 150 lph, so the fuel pump has to be sized to IRO 190 lph min.

The std pump won't flow enough fuel at max. power,so the engine will run lean and Kaboom!

Market choice seems to be a Walbro 255 lph open end which will flow IRO 230 lph at 3 bar.


Simples?
It should be as it involves basic engineering flow/pressure principles.

Someone correct me if I`m wrong here,but isn`t the fuel pump argument completely invalid? A stock engine will need X amount of fuel injected at WOT on whatever the maximum load, The stock fuel pump will be able to provide enough fuel to keep the fuel rail supplied with the right pressure for this application. In allother driving situations the unused fuel will be returned to the tank.
If a more powerfull engine (past a certain level) requires more fuel at WOT and maximum load, the stock fuel pump would not be able to provide enough fuel to keep the rail pressuurised whilst the injectors are fireing as much as the ecu tells them to. So a higher flowing pump is required, the situation where more fuel is needed from the pump above standard is quite rare, but it does happen when the load is increased, giving the need to uprate the pump. In all other driving situations again, any excess fuel is returned to the tank, meaning the pump alone is needed for maximum load times, but in allother situations it has no effect on the amountof fuel used.
The fuel enconemy denbate is down to other factors which are being discussed here,nothing to do with the pump.

Butty - Thats what i was trying to say, it makes more sense your way. :thumb:

This may all be true, but it is not answering SSU's question.

You are saying that more power means more fuel flow is needed.

What SSU asks is: If less fuel is needed after a remap (i.e better mpg), why is a higher flow fuel pump required?

The answer I think is that 99% of the time (in normal driving) you are running at less than full power and more efficiently after a remap, but at full power you need more fuel than a std pump can supply.

Sorry, the route did NOT contain the same driving conditions ..... the only thing that was the same was that it was a saturday!! :lol1:

Could you tell us a few things ...

How many miles was this journey, each way?

What were the exact times of travel?

Don't worry yourself about the atmospheric pressure ... I'll handle that - wouldn't want to overload you. :D

It is answering his question - a fuel pump is sized to meet max. power demand.
At non max. power output, the spare fuel is just returned back to the fuel tank........

Good reply ... or it would be, if it wasn't full of holes ... lets take just one:-

A remap to 340 bhp requires a fuel demand of 150 lph, so the fuel pump has to be sized to IRO 190 lph min.

Where the hell has that 340 BHP = 150 lph come from? :wonder:

I have never seen anything like that statement before ... surely the fuel required has more to do with what changes have been made than a simple BHP figure? And, if I'm right, what you say is just made up :wonder:

I'm still struggling with the idea that the mapping Engineers at Subaru did not jump onto the fact that they can get their cars to higher mpg's ....

The fact is that they would have to sacrifice something to gain those mpg's - that would be a reduction in power - or a decrease in realibility ... none should be acceptable.

To my mind, Subaru know what they are doing - much more than hobbyists (with all due respect to those who tinker) - my car, at 10 years old and 98,000 miles without issue - shows that they get it right.

I refuse to change my Subaru reliability into something which would embarass a TVR ..... even if it meant I got to the back of the queue in front 0.002 seconds faster!

ahh, that's because you don't have the modding bug! We do. It's called a freedom of choice! You choose to spout undiluted push on here! That's ur choice. ;)

I think you lot are great .... you give me hours of challenging thought and debate, you go your own way and tinker with your pride and joys ..... and do what you believe in, I salute that.

But I do really struggle with the concept of buying a car you don't want (if it was what you wanted it, you wouldn't change it) .... I buy a car which does what I want it to do.

I don't buy a WRX and mod it to 330BHP ... I go out and buy a 330s.

SSU with all due respect to your obvious automotive engineering skills, which you are yet to establish what qualifies you to pass your opinions as fact? :Suspiciou

The route that I took was from my house in Llanelli, A476 to Cross Hands, A48 to Carmarthen, A40 towards Haverfordwest, at Haverforwest take the B4548 (I believe) over the Preseli mountains, A486 (i believe) to Cardigan, A484 to Carmarthen, A48 to Cross Hands, A476 to Llanelli, total route 130 miles. :)

Both runs I left at approx 6.30pm, obviously I did encounter some other traffic en route but it was light - I could not recreate those road conditions. :cuckoo:

Have you also yet grasped the fact that fuel used more efficiently equals better economy? :wonder:

Thats fair enough if you can afford to do that!! I have a hawk WRX and for the first 2 years it was standard!! After that I thought I would like a bit more torque and a nice burble from the exhaust!! So I bought a full milltek system,panel filter (yes I also went for an uprated fuel pump) and remap!! Total cost was about £1200 which is vastly cheaper than selling it and buying a 330S. I am delighted with the car after the remap but I do admit being a bit causious at the time and having someone tinker with the ECU. The whole issue with the fuel pump imo you are probably right but for piece of mind I changed mine and at £65 its hardly a big deal.