How to tune engine to drink less fuel?

[jtbo]

I know how I can get +200hp from my engine, but if we would aim to 130hp and ~170nm of torque at minimum how to build engine that drinks as little as possible?

I'm looking fuel economy of 45mpg (uk gallons) on highway and not worse than 35mpg on city.
That should be near Ford Focus level (when that f**d has a good day), bit better than Focus is actually what I would like to get but it is maybe not very possible, 16 valves, variable cam timing, FWD having few % less losses, coefficient of drag is 0.32 for focus when 300 has 0.38, but Focus weights 150-200kg more.

2ltr engine is perhaps out ruled from this as it really is not capable of running extreme lean mixtures too well and if smaller engine can run leaner while still producing 30hp with part throttle then it will be more economical than big engine.

So this means that there is 1.4 and 1.7 engines left.

Now as we know turbo engine is far superior in terms of efficiency when compared to NA engine of same power output, specially fuel consumption is much less because of how turbo works, you get basically several sized engines in one package.

Also as we know, modern engine management can do much better than carbs, because of ignition and injection can be adjusted based to temperature and load, quite well, also knock sensing allows us to try to get that last efficiency % out from engine.

I was thinking about small turbo, mostly because of quick spool up and less losses, no point to get that caterpillar's turbo for 130hp
Maybe something like in Fiat Uno Turbo should do the job.
Intercooler is a must of course.

Intake and exhaust manifolds + downpipe are needed to be made as custom work, I believe?

Engine management would be Megasquirt with possible COP ignition.

I'm sure many of you have read about VW's new 1,4l dual charged engine, it has CR of 10 and boost of 2.5 bars, which could sound impossible when first time heard, but it is quite possible.
Now this engine has direct injection, I think that is then reason why this is possible?
So with our limited resources, funding and skill it is perhaps not too realistic to get to that level, but aim could be to get less fuel consumption as possible while still getting better performance than stock GLT.

Now this is just theoretical planning, which is aimed to do so that if there would be funding it would be possible to be made, so I plan to make some budgeting and lot of calculations

First is needed to decide which model it is going to be where this is going to be built from.

I wish to get ideas and comments then and specially as I don't know too well these 1.4&1.7 340s engines so I may have some gaps there as well.

[Carl]

Well a 400 turbo engine has ~120bhp stock, but I'd reckon you'd struggle to get 35mpg in town. Even 45mpg on the motorway might be pushing it.

If you want GLT performance with decent economy, and don't mind a project, then I reckon your best bet is a TD conversion. An older style TD without an fancy electrics would be fairly easy to install in terms of wiring and would get you the performance/economy you're after. You'd have to manufacture a few more parts though (manifold, engine mounts, bellhousing adaptor etc).

As an example, a Peugeot 306 has a 1.9TD engine with ~90bhp. Spend around £500 with Allard and you'll have ~120bhp, but more importantly over 200lbft of torque. And it will still average over 40mpg. I think that would make quite an interesting car when put in a 360!

[Chris_C]

400 TD... thats 120bhp stock

[MJ]

Didn't someone a while back say that there was a Renault diesel that should fit fairly easy into a 340 as it's a diesel version or the 1.4 or 1.7?

One thing I was wondering about MegaSquirt, is, is there an optimum fuelling/ignition that gives both max economy and max performance due to good burning? Or would it have to be tuned differently for both?

If this is the case, is it possible with MegaSquirt to have a switch on the dash to change between different maps?

[Carl]

400 TD... thats 120bhp stock

Really? Are you sure? That's much higher than I would have expected!

Don't know much about them TBH, was the engine Renault based, and if so does it have the same engine-bellhousing bolt pattern as our 1.4/1.7s?

[jtbo]

Yes, diesel is of course easily getting to those numbers, however my plan is going to harder way at designing, using more science than simple traditional methods, perhaps easier with building, depends from person and point of view I think

When optimizing engine for leaner mixture it is crucial that near spark plug mixture is most rich, intake port, intake valve and top if combustion chamber are important areas, also piston too, I am in belief that shaping these would help greatly to achieve this goal.

I'm hoping to modernize old engine to today's level, I recall 400 series turbo engine has CR of 8 or something like that? That is bad for fuel economy and with engine management of 400 it will never be too good, it is old design with some limitations.

Making manifolds is not big problem, it just adds to costs quite a bit, making engine mounts is bigger issue, that would require some documents and it will cost several hundreds, nearly thousand so I rather like not to modify them.
For mot it is needed to prove that new mounts are safe (in case of accident) and as strong as originals, calculations and engineer's proof needed, also need to proof that work is done as engineer is planned and such things, it is not so easy. So this also limits choices of engines to original ones.

Of course everything is going to be just theoretical until I find necessarily funding, but planning is fun too and with perfect plans building something is going to be really easy

I write slow, many replies did came already while typing

With megasquirt you can have different maps, but in practice not much use as you can set map so that at lower throttle positions you have less fuel consumption and at WOT it gives max power.

[germ]

Theres the 1.6 dieel engine out of the renault 5 diesel and some 340's (not in uk) its basically the 1.7 but slitly smaller it has 60hp stock it might be interresting to turbo charge one of those although turbo charging diesels is never as effective as petrol (the 1.6 diesel does just over 60mpg)


Other than that 1.8 clio engine 45 mpg 110hp stock? possible? Turbo it ?
Will

[SteveP]

400 TD... thats 120bhp stock

Really? Are you sure? That's much higher than I would have expected!

That's because Chris is wrong... its more like 90bhp IIRC

[SoLaMaNdA]

I don't want to pee on your fire but surely it's not worth the effort? Petrol isn't the biggest cost of running a car, (just seems so as you buy it often). To get a worth while improvement in economy it would cost more than you could save in a couple years driving.

If you're just doing it for a challenge ignore the above

[Chris_C]

hmmm, Steve is indeed right, just looked it up on VADIS! Wonder what I was thinking of.

Anyway, that was lucky, I was gonna put one of them in Kar, instead of the B18FT, as it'd be nearly the same power and much better fuel economy . However, I would then have looked a tit, with a car that didn't go much faster than Fake!

[Carl]

Yes, diesel is of course easily getting to those numbers, however my plan is going to harder way at designing, using more science than simple traditional methods, perhaps easier with building, depends from person and point of view I think

Ah I see. Well that makes things a bit different. I guess the 1.7 engine would be a good starting point then.

You mention the VW dual charge engine, did you know that Nissan were doing this 15 years ago in the Micra (actually called the March ST). They took a little 900cc 8v engine and bolted on a supercharger and turbocharger. The supercharger provided boost at low revs then the turbo kicked in and diactivated the supercharger at higher revs. I think they got 110bhp out of it. And there are a few people round the UK with tuned versions giving much more. Might be worth investigating this technology and it won't be anywhere near as complex as the modern VW engines.

[jtbo]

Yes, this is completely and only a challenge of human mind and creativity, it is not so much about saving money, if I would like to save money I would sell Volvo and invest all money to stock market, some environmental thing would suit well, those will gain value quite well

I hear people say how old car can't be economical etc etc, I think they are wrong, it is possible to make old car to drink fuel less or same as new one, older cars are generally lighter than new ones for example.

I think that only engine options to consider are therefore 1.4 and 1.7, just would need to find out which one suits better, 1.4l is of course good as it is same size as VW's new engine.

Dual charging is not perhaps what I wan't as, imo it makes economy worse, but gives out more power, for VW Golf that extra power is needed, but I think for 300 1,4l engine can produce enough power at low throttle and turbo will come in quite fast when kept small enough. Of course lot of this is guessing and estimating now, please tell if you find it different from your experience.

[SoLaMaNdA]

I find the 360 is pretty frugal in it's standard form. I get over 30mpg (normal driving is cruising on motorways 80-90, passengers and a big draggy rack on the back). Funny when you compare to real world mpg of modern cars, they aren't far off.

[IvanS.]

I find the 360 is pretty frugal in it's standard form. I get over 30mpg (normal driving is cruising on motorways 80-90, passengers and a big draggy rack on the back). Funny when you compare to real world mpg of modern cars, they aren't far off.

Quite right.....some of old models like Citroen 2CV used to spend very low amount of fuel, but more and more now-day cars are economical ( not mentioning those running on electricity or hybrid ).

The problem with 300 series ( 1.4 especially but not 1.7 ) is that car is a bit too heavy and it's design for relaxing type of driving. Only problem is it has small amount of hp when you attempt an overtaking.

The fact is you can mount a cannon turret on Volvo, as it has superb security level even without any air-stuff round, and imitate a tank.

[jtbo]

Every design can be improved, no matter how well made it is. Even this new VW engine could be made to use less fuel or give more power.