Hi from Hungary
 

Hello everybody,

let me introduce myself:

I am a 27y old mechanical engineer,have an Audi A4 B5 with a 90Hp TDI engine.
Nowadays fuel prices went to the sky,so i got more and more interested in fuel saving methods and hipermiling.

The car does constantly around 5.1L/100km (46MPG US) on diesel,weight is around 1350Kg.

The overall economy is not bad at all with stock car,but i am looking to improve is more and more.

Previously it was fitted with a 1.8T gasoline engine,with pulse and glide i got it to 6,1L/100km also,so it could work also with the diesel engine as well.

Aerodinamics should be also improved.Stock one is 0.31,car is lowered with 40mm,wich improves it also a little bit. I decided to start with grill blocking,so i blocked the grills on the bumper and hood to see if there is any benefit.Testing should be done.

I read here also if the alternator is shut down,it also improves the fuel consumption by 5-10% wich would be amazing.I am looking for a solution to use some type of management for the alternator. For example charge only if voltage drops under 12 or 12.2V, Charge on overrun braking etc.
Maybe somebody did this before me.

Well big changes on the car are not allowed in our country (like boot tailing),but i hope with smaller modifications i still can improve it.

Thanks for reading!

Welcome to EcoModder, Radics:)

That's not too bad, but I'm sure you can do better: Your Audi has a smaller Cd than my Peugeot (0.31 vs. 0.33) and less frontal area (at least 10cm lower, even without the 40mm lowered suspension), so you should be able to hit 4.5 l/100km, or even below 4.0.

So you swapped a TDI into a gasser? Or did you switch cars?

There lots of threads on this, but I don't think that it has been successfully DIYed. Here is a great read:
Automatic alternator cut out/regen braking
There are a few things you need to take into account when doing this mod:

1. Your alternator has to have a field wire. Some alts are self-exciting, which would take a lot of work to deactivate the field.
2. You must reduce your car's electric needs to a minimum. For example, if you have to have your lights on during the day, then install LED daytime running lights (DRL), which should save 120-200W.
3. You need a large battery, deep cycle is best, otherwise it'll die pretty quickly and the replacement will cost you more than you saved in fuel.
4. Disabling the alternator's field saves some fuel, but not as much as taking it off the belt.
5. You should have a place to charge the battery when parked. Charging it only from the alternator won't save you nearly as much fuel.

Yes,i made a swap from the gasoline (around 350hp,built engine,custom management,big turbo,etc) to the TDI,including trans,exhaust,pedals,engine wiring,ecu,fuel tank,etc.

We need to use light in daytime if driving outside town.I usually use it everytime,everywhere.If i forgot to swith on,it can cost me some money if the cops see it.

Battery is a 74Ah one,brand new. I actually dont know how much energy is used to control the TDI,i assume much less than the gas (ignition,fuel pump),of course glow plugs take a lot,but TDIs usually ingore glow plug heating over 5 degrees.

I need to look for led bulbs,that is pretty much energy wich can be saved.Removing the belt is not an option,because serpentine belt is driving the servo pump,and from the servo a second belt is driving the water pump.

4L would be a great result i think.I also read,bigger nozzles could help also,because of short injection time at the right timing increases efficiency.

That gasser was a monster! I'm surprised you could get as low as 6 l/100km with it:thumbup:
Yes, I remember how on our trip to Romania, when crossing the Hungarian border the officer reached in through my open window and turned the headlights on. I already had my DRLs installed then, but apparently the officer didn't yet know they were a legal substitute for headlights in the EU. I'm sure that DRLs are perfectly legal in Hungary now, so you can look into fitting them on you car. Here is how you can get them wired up: How to wire DRLs.

Well,

the 6L/100km is reached with the unmodified engine and fuelling, when it was 150 hp.

With the mod i was around 8L on gas or between 10-12 with E85,but i was over 200km/h daily

Hi,

i was looking for improvements on the engine and drivetrain also.I realised,that the 110hp version has better fuel consumption datas.Read a lot,people states it is because it has bigger nozzles,so the required fuel (for same power) can be injected more quick,wich increases fuel efficiency.

Another difference is the final drive ratio in the gearbox: 3.889 (90hp) vs. 3.7 (110hp),wich equals to 5% longer gears.I have my 1.8T gearbox,where the final drive ratio is also 3.7,so it could be replaced.

Car became famous!

Somebody picked my cars pic to be the "cover" for the manual. :D

Is that your A4 with the 350hp gasser still it, right?

Re: larger injectors - if you only swap them without reprogramming the ECU, then they may inject more fuel. If you are getting larger flow them it should be for a shorter duration. Though I'm not sure whether the injector swap would save you enough fuel it be worth while.

My 1.6 HDi also comes in 90hp and 110hp versions, the weaker getting slightly lower fuel economy, one of the reasons may be that it doesn't have an intercooler (diesels like a warm engine and cold intake air both for FE and power). I once saw a test where just adding an IC raised the power from 90 to ~100hp, while the other 10hp came from reprogramming the ECU to account for cooler air.

But if you'd be fiddling with the ECU anyway then might as well do an eco-remap.

On the pic,it is with the gasser,yes,last summer,before engine swap.

TDIs respond well to changes like that,althrough the ECU can be also adapted to such changes via VAG-COM.

For me,the major diffences between 90 and 110HP version are bigger nozzles,VNT turbo with higher pressure.