Anyone running an audi a4 1.8 120bhp on lpg?

[Gstyle17007]

Anyone running an audi a4 (B8) 1.8 120bhp on lpg?


Or anyone had any experience running this engine.

Its the same engine as the 170bhp but just the car has been remapped limiting the bhp.

Once remapped this car can get to 200-220bhp.

Is it a sensible option to convert one of them to lpg and have it remapped to increase the bhp?

Or will that impact the mpg in a bad way.

And in terms of car is it better to go for one with 50k miles or 130k or does it not make too much of a difference.

[scottyf]

You'll get less mpg if you use all 200 hp all the time. Physics dictates that...

[Gstyle17007]

You'll get less mpg if you use all 200 hp all the time. Physics dictates that...

Hi its 39 mpg at 118bhp on the 1.8 fsi

but 42 mpg at 208bhp on the 2.0 petrol engine

how is that

[LPGC]

I've converted a few Audi FSI's. Having a direct injection engine means it needs special LPG system electronics. These electronics are specific to the engine code, so before you buy the vehicle, check it's engine code and ask one of us if electronics are made for that engine code.

You'll get less mpg if you use all 200 hp all the time. Physics dictates that...

Hi its 39 mpg at 118bhp on the 1.8 fsi

but 42 mpg at 208bhp on the 2.0 petrol engine

how is that

Obviously it's true what Scotty said, you'd know anyway that if you boot a vehicle you're going to get less mpg.

Your question was probably more pointed towards the figures seeming to show the smaller engine gets less mpg (according to certain book figures) than the bigger engine though. I haven't asked where you've seen these figures or checked Audi's figures, but Wikipedia info shows the 2Tfsi with a 6 speed manual gearbox gets better mpg than any of the 1.8 options... That's if CO2 emissions are anything to go by anyway, and they should be. Maybe if true it's down to gearbox ratio and efficiency. They are a wide range of gearboxes fitted in these models.

Simon

[scottyf]

Correct.
At the end of the day two cars same weight and drag need "X" power to acheive a certain speed. Which means an engine needs to product that power to keep the car at a certain speed.

Now the only way to get better fuel effciency (Ie more mpg) is to change the gearing or maybe the engine at a certain speed is more fuel effceint.

Maybe the 1.8 @ 70mph is at 3500rpm. But the 2.0 is geared for 70mph @ 3000rpm. So although the larger engine is burning more air and fuel per stroke its rotating slower than the 1.8. But maybe at those revs the engine uses its fuel more effciency.


The Alfa i have comes in 1.6, 1.8 and 2.0 engine variants. Its the same engine. But each extra 200cc means the stroke is lengthen.
This means the 1.6 is rev happy (Short stroke low torque but fast response). The 2.0 has a long stroke (more torque slower revs).
The 2.0 have a longer ratios in the gear box.

All engines get similar mpg even though there is 400cc difference. In the same car.
However boot the 2.0 and you'll get less mpg than the 1.6.

Every day driving the same though.



its a minefield learning what adjustments do what but you can never beat the laws of physics.
You can only engineer and compromise what one does well and what it doesn't do well.

That is all.

[rossko]

To address the other part of the question;
As FSI equipment is engine-specific, you might well get into difficulty if you have a kit fitted to a 120bhp engine, but later change the engine to something else (by having it remapped).

Probably not so much a mapping issue, more likely LPG components being specified for 120bhp not being capable of delivering 200bhp.

[Gstyle17007]

To address the other part of the question;
As FSI equipment is engine-specific, you might well get into difficulty if you have a kit fitted to a 120bhp engine, but later change the engine to something else (by having it remapped).

Probably not so much a mapping issue, more likely LPG components being specified for 120bhp not being capable of delivering 200bhp.

What would be a better way around to go around the remapping.

Having it remapped to 200bhp first and then having the conversion carried out for example?

For the audi a4 does it make more sense just in general to have the wheel tank or to have it in the boot?

Also is it possible to have a tank in the boot and in the wheel space?

[LPGC]

As FSI equipment is engine-specific, you might well get into difficulty if you have a kit fitted to a 120bhp engine, but later change the engine to something else (by having it remapped).

Probably not so much a mapping issue, more likely LPG components being specified for 120bhp not being capable of delivering 200bhp.

Good points from Rosko.. Often the specific electronics are bundled with reducers, injectors, a firmware file, even a map file so the installer isn't supposed to need to do much in the way of calibration. It is mostly the reducer and injectors that might not be up to the job if engine power is increased.. But we don't have to fit bundled kits, we just just need the specific electronics and these are available separately. In any case, a pro installer should be happy enough buying such a bundle and shelving the bundled reducer and injectors to fit on something else at some later date. So, we can still pick and choose our own reducers and injectors and fit them with the specific electronics. This will of course mean that the supplied map probably will need tweeking but I have never found a supplied map that worked properly without some tweeking anyway. Also, bundled kits can be improved by fitting better injectors than those bundled in any case.. In this respect, I can't see the parts being a problem.

But there is still a question mark regarding big power increases... One aspect of direct injection engines is that they often inject multiple shots (injection pulses) of fuel per induction (even compression on a DI engine) cycle. One way in which the specific electronics are different from 'normal' LPG electronics is that they are designed to interpret the different combinations of these multiple petrol pulses into a single long pulse for the LPG injectors. This interpretation is done by the firmware that is specific to the vehicle model and LPG ECU combination, there are no adjustable settings to allow the installer to adjust how the pulse interpretation is done. With a big power increase, we cannot be absolutely sure that the specific electronics would still be able to properly interpret the petrol injector pulses. My guess is that the specific LPG ECU / firmware combination would be able to interpret longer duration pulses, but maybe not a greatly higher number of pulses per intake / compression cycle (frequency).

Due to the above, my advice would be - If you would be happy running the vehicle at standard power (even though we know you would ideally like the power upgrade), then buy the car, have it converted to LPG using the specific electronics but inform the LPG installer of your power increase intention and he should understand that he should fit a reducer and injectors capable for the power increase. Then have the power increase done - maybe negotiate a deal with the power increase person where if you can't get the thing running well on LPG after the power increase they will reverse the process for lower cost. Then obviously revisit the LPG installer to see if the LPG system can be set up to work properly with the power increase - if it didn't work out, you would need to have the power increase reversed! I don't think there would be much of a problem - I doubt the tune would be sophisticated enough to greatly change the number of pulses (particularly if it's a none dealer aftermarket tune), I think such a tune will simply increase the duration of the pulses, meaning the LPG electronics won't have a problem interpreting them. The paragraph below relates to my thinking on this.

The biggest advantages for DI technology are achieved at part throttle operation - The idea being that during part throttle a localised correct mixture can be made inside the combustion chamber, where if the same quantity of fuel (that gives the localised lean burn) were averaged out across the combustion chamber (as it is with port injection) the mixture would be too lean.. In effect, the localised mixture regains some of the fuel economy advantage of having a smaller engine. So, away from light throttle, the advantage of DI is diminished as the DI injectors are no longer just trying to create a localised correct mixture but now to fill the whole cylinder with a correct mixture to make use of the cylinder volume and produce torque. No longer just a couple of short precisely timed pulses, these still occur, but now the emphasis is on making power, which requires filling the whole cylinder with a correct air/fuel mixture.

For the audi a4 does it make more sense just in general to have the wheel tank or to have it in the boot?
Also is it possible to have a tank in the boot and in the wheel space?

Most would go with the wheel tank, and yes you can have both at the same time. Depends on your requirements - these days a lower proportion of people would mind losing the spare wheel, most don't need the increased range of 2 tanks, most don't want a cylinder taking up boot space. Obviously 2 tanks would add to the cost of the conversion.

This would be an interesting conversion!

Simon

[Gilbertd]

But there is still a question mark regarding big power increases... One aspect of direct injection engines is that they often inject multiple shots (injection pulses) of fuel per induction (even compression on a DI engine) cycle. One way in which the specific electronics are different from 'normal' LPG electronics is that they are designed to interpret the different combinations of these multiple petrol pulses into a single long pulse for the LPG injectors. This interpretation is done by the firmware that is specific to the vehicle model and LPG ECU combination, there are no adjustable settings to allow the installer to adjust how the pulse interpretation is done. With a big power increase, we cannot be absolutely sure that the specific electronics would still be able to properly interpret the petrol injector pulses. My guess is that the specific LPG ECU / firmware combination would be able to interpret longer duration pulses, but maybe not a greatly higher number of pulses per intake / compression cycle (frequency).

Seems to be an awful lot of question marks. Why not just get the 170 bp version in the first place? Or the 120 bhp version and then slot in a 2.0 litre 200 bhp lump?

[Gstyle17007]

The 120bhp insurance is good because i have a young driver as additional driver on the policy, the others 170bhp and the 2.0 knock the insurance up.

But 120bhp with lpg is a good price on the insurance.

What sort of price would seem reasonable for a prins or brc gas kit with a remap for 200-220 bhp on the audi a4 120bhp.

and what sort of mileage one is good for this sort of project.

Because in terms of re-sale i wouldn't get much back if anything for the extras i'm assuming.(lpg +remap)

Though a high mileage 100,000+ may not be good for these changes due to the high mileage.

[Gilbertd]

I would have thought a declared remap to up the power would increase the insurance considerably more than buying the more powerful car in the first place. Young drivers and modifications are the sort of thing that insurers go ape about.

As the FSI engine is Direct Injection do either Prins or BRC do a kit for it? As Simon mentioned, you need a specific kit for an engine which is why the modifications make things much more difficult.

[LPGC]

Seems to be an awful lot of question marks. Why not just get the 170 bp version in the first place? Or the 120 bhp version and then slot in a 2.0 litre 200 bhp lump?

Yes, with one big question mark, the pulse interpretation..

Both Prins and BRC make a few types of system that can be classified as liquid injection: 1. Type to convert DI engines, using LPG vapour injectors, reducer, slave type ECU (same methodology as AEB really). 2. The type that use existing petrol DI injectors and use a valving arrangement to switch fuels to the DI injectors. 3. Liquid port injection systems for none DI engines (like some factory fitted liquid port injection LPG systems, Fords Transit Connect etc. 4. I don't know if exists a combination of 1 and 3.

Would advise anyone who intends tuning a DI engine not to fit a Prins or BRC type 1, 3 or 4 as I've numbered above... I doubt the installer would have much of a chance of getting it to work on a none standard engine. Which leaves type 2, and there doesn't seem to be a great deal of info about these yet... Never seen one in the flesh, but I like the idea.

I would have thought a declared remap

Only if he does declare mate, but reading between the lines...

Simon