A question for engine geeks

[durbster]

When I was last looking for work, with things as they are I started looking at cars to be ready for the possibility of a long commute.

The engine in my MX-5 was designed in the mid-80s (?). It produced around 115bhp, 0-60 is around 9s, it can do 38mpg and it is incredibly reliable. When I started looking at boring, economical hatchbacks I was very surprised to see that a similar engine from about 5 or 6 years ago offered pretty much the same stats. Different sort of cars of course, but for similar performance, I honestly expected to see mpg well into 40s at least. I know cars have got heavier but I figured engines had developed accordingly.

With the environment being a critical selling point now, brand new cars seem to be moving engine technology on and that suggests to me that the 1.6 engine in the MX-5 is from the same generation of IC engines as those a few years ago, a period spanning at least 20-odd years.

So, the point of all this is a simple question: how many generations of IC engine would you say there has been since it's invention?

How many major steps forward (e.g. fuel injection) have there been and what were they?

[Dr Interceptor]

Carburetter to Fuel Injection
Single Point Injection to Multi-Point Injection
Forced Induction - supercharger/turbocharger
Various configurations - Straight engines, V-engines, W-engines, Rotary-engines (ring of cylinders used on planes) and Flat Engines
wankel Rotary Engine
Camshaft variations - SOHC, DOHC
Single spark, Twin Spark
Engine Management systems to constantly monitor timing etc

That's without going into various ancilliaries like Distributors, coils, gearboxes etc etc etc.

[Jayho]

durbster said:

When I was last looking for work, with things as they are I started looking at cars to be ready for the possibility of a long commute.

The engine in my MX-5 was designed in the mid-80s (?). It produced around 115bhp, 0-60 is around 9s, it can do 38mpg and it is incredibly reliable. When I started looking at boring, economical hatchbacks I was very surprised to see that a similar engine from about 5 or 6 years ago offered pretty much the same stats. Different sort of cars of course, but for similar performance, I honestly expected to see mpg well into 40s at least. I know cars have got heavier but I figured engines had developed accordingly.

With the environment being a critical selling point now, brand new cars seem to be moving engine technology on and that suggests to me that the 1.6 engine in the MX-5 is from the same generation of IC engines as those a few years ago, a period spanning at least 20-odd years.

So, the point of all this is a simple question: how many generations of IC engine would you say there has been since it's invention?

How many major steps forward (e.g. fuel injection) have there been and what were they?

From what I can gather most of the investments for more economical cars have been put on firstly the Turbo Diesels, and reducing the Turbo lag. Now the investment is in the low CC Supercharged and Turbocharged engines.

You've also got to remember that a lot of these more modern cars with similar stats are being used in run of the mill family cars, which 0-60 in under 10 seconds seems quite reasonably quick when previously they were probably around 12 seconds? (Which also gets me annoyed at the fact that its getting increasinly more difficult to overtake cars on back roads due to the acceleration which is now readily available.

[fourwheelsteer]

A lot of improvements in engine performance have come from 'hidden' factors. Synthetic lubricants, improved bearings, tighter tolerances and superior fuel.

[Dave Hedgehog]

Jayho said:

From what I can gather most of the investments for more economical cars have been put on firstly the Turbo Diesels, and reducing the Turbo lag. Now the investment is in the low CC Supercharged and Turbocharged engines.

You've also got to remember that a lot of these more modern cars with similar stats are being used in run of the mill family cars, which 0-60 in under 10 seconds seems quite reasonably quick when previously they were probably around 12 seconds? (Which also gets me annoyed at the fact that its getting increasinly more difficult to overtake cars on back roads due to the acceleration which is now readily available.

there's an awful lot of metal on the road now that can run mid 6s, most of the mid ranged german oil burners seam to

[durbster]

Jayho said:

You've also got to remember that a lot of these more modern cars with similar stats are being used in run of the mill family cars, which 0-60 in under 10 seconds seems quite reasonably quick when previously they were probably around 12 seconds? (Which also gets me annoyed at the fact that its getting increasinly more difficult to overtake cars on back roads due to the acceleration which is now readily available.

I was thinking more of a direct comparison, specifically the 1.6 engine in my MX-5 with a modern 1.6. I suppose a more sensible comparison would be a same-purpose car from one manufacturer.

The latest Mazda 3 1.6:
0-60 - 11.8
BHP - 103
MPG - 44

Source

Compared to the 1994 Mazda 323 1.5:
0-60 - 11.5
BHP - 90
MPG - 37Mpg

Source

Perhaps it's because I work in IT where things develop at a comical pace but I expected twenty years of engine development to have yielded quite a bit more of something, and when performance and power are not priorities in this particular model, you'd think mpg would have soared. Perhaps refinement and emissions have absorbed all development.

fourwheelsteer said:

A lot of improvements in engine performance have come from 'hidden' factors. Synthetic lubricants, improved bearings, tighter tolerances and superior fuel.

That's a good point, and it makes the above findings all the more baffling

[penryar]

Using the mazda example you stated, I think to get a clearer picture you need to factor in the relative weights of the cars.

Doing a quick search the 2011 Mazda 3 weighs a whopping 3064 lbs (sourced from a US site) whereas the 1994 323 weighs only 2238 lbs . Thats a vast difference that is going to have a big influence on 0-62 times and economy.

[hairykrishna]

durbster said:

Perhaps it's because I work in IT where things develop at a comical pace but I expected twenty years of engine development to have yielded quite a bit more of something, and when performance and power are not priorities in this particular model, you'd think mpg would have soared. Perhaps refinement and emissions have absorbed all development.

The truth is that the amount of efficiency improvement available for an Otto cycle engine which burns petrol and has a throttle is very limited. The theoretical maximum is about 35% and we're already >20 (depending on driving conditions/habits). Without fundamentally changing how we use the fuel mpg isn't going to soar!

[5lab]

you've got to remember that fuel consumption figures from 'back then' were the manufacturers own tests. I think they also tested at 'a constant 56mph, a constant 70mph' etc. These are always going to be worse than the current EU test

also, 37 to 44 is a 20% increase, which isn't too bad

[mcflurry]

Shortly after passing my test I had a 1.4 litre Ford, with about 60 bhp.
A modern day 1.4 has around 50% more horses (Clio = 80, Yaris = 90, Polo 16v = 100)

[MrKipling43]

5lab said:

also, 37 to 44 is a 20% increase, which isn't too bad

I reckon they've also probably doubled the service interval between those two motors. Further savings.

[mat205125]

MrKipling43 said:

I reckon they've also probably doubled the service interval between those two motors. Further savings.

We're not lapping valves every 60k miles, wearing cam lobes out by 80k, or losing all compression by 100k on its way to a scrap yard .... A well cared for engine will last for hundreds of thousands of miles with out unscrewing a head bolt.

[DrTre]

Tbh I've always considered the mx5 to have pretty woeful fuel consumption figures for its weight and power output, ie that 38 mpg is a bit ambitious

[penryar]

MrKipling43 said:

5lab said:

also, 37 to 44 is a 20% increase, which isn't too bad

I reckon they've also probably doubled the service interval between those two motors. Further savings.

Whilst also dragging around 33% more weight as well.

[durbster]

I'm not convinced modern engines are more reliable so I'm not sure they are cheaper to run. I've no doubt cars as a whole package are more reliable but the engine itself? I'm not convinced.

Regarding real world figures, another resource I spent a lot of time scanning was the PH MPG wiki, looking for cars that stood out as being significantly better on fuel than the MX-5 and there are very few cars offering mpg well into the 40s on there.

penryar said:

Using the mazda example you stated, I think to get a clearer picture you need to factor in the relative weights of the cars.

Doing a quick search the 2011 Mazda 3 weighs a whopping 3064 lbs (sourced from a US site) whereas the 1994 323 weighs only 2238 lbs . Thats a vast difference that is going to have a big influence on 0-62 times and economy.

I know cars (like humans) have got fat since the 80s but that's quite astonishing. It'd be interesting to drop the Mazda 3 engine into the old 323 to see how it fares

DrTre said:

Tbh I've always considered the mx5 to have pretty woeful fuel consumption figures for its weight and power output, ie that 38 mpg is a bit ambitious

I've had my MX-5 eight years and it always gets 37-38mpg on a long run (typically around 33mpg). I was looking for something more economical but I was surprised to find so few that would justify changing for economy alone, hence the thread.

[durbster]

penryar said:

MrKipling43 said:

5lab said:

also, 37 to 44 is a 20% increase, which isn't too bad

I reckon they've also probably doubled the service interval between those two motors. Further savings.

Whilst also dragging around 33% more weight as well.

Not impressed Im afraid.

My PC at home is something like 10,000% faster than the computer we had in 1990, and probably uses a similar amount of electricity

Edit: Sold myself short - computer processing power has actually moved on by 1.6 million percent!

Edited by durbster on Tuesday 20th December 17:30

[Decky_Q]

cars have moved on, manufacturing processes have moved on but engines have moved very little tbh.

Alfa romeo for example- The 2.0TS engine in my 2003 track car was developed in the 70's, its gone through a few revisions cf1,2,3 but that was adding catalytic converters, fuel injection, improving casting techniques etc really it is still the same engine.
Now Alfa have the 'ti' engine range, which is a TS with one of the spark plug holes filled in during casting so it now runs single spark plugs, but its touted as a 'new' engine.

Some of the engines you are looking at have been designed in the 60/70s and then revised over and over making small changes to meet legislation, like adding EGR, or head revisions etc and then released as a new design.

This is not true for other engines out there, as some manufacturers have started clean sheet designs, but its not the norm.

[Otispunkmeyer]

durbster said:

When I was last looking for work, with things as they are I started looking at cars to be ready for the possibility of a long commute.

The engine in my MX-5 was designed in the mid-80s (?). It produced around 115bhp, 0-60 is around 9s, it can do 38mpg and it is incredibly reliable. When I started looking at boring, economical hatchbacks I was very surprised to see that a similar engine from about 5 or 6 years ago offered pretty much the same stats. Different sort of cars of course, but for similar performance, I honestly expected to see mpg well into 40s at least. I know cars have got heavier but I figured engines had developed accordingly.

With the environment being a critical selling point now, brand new cars seem to be moving engine technology on and that suggests to me that the 1.6 engine in the MX-5 is from the same generation of IC engines as those a few years ago, a period spanning at least 20-odd years.

So, the point of all this is a simple question: how many generations of IC engine would you say there has been since it's invention?

How many major steps forward (e.g. fuel injection) have there been and what were they?

Since that first MX-5 I think a lot of effort turned to the engines that burn the devils fuel/Diesel. Petrol engines at that point were pretty well developed from a combustion standpoint anyway (premixed air-fuel in a plenum and throttle it into the engine) and thus they haven't made massive amounts of progress since. Of course there has been Direct Injection for petrols but I think its a lot harder to perfect than diesels which have been DI for ages due to how they work... I mean you don't need to throttle the mixture and you don't need to keep to a particular AFR or worry about engine knock with a diesel, where as you do have to worry about those things with a petrol engine. Don't forget as well, the petrol engine has been used in the car for a lot longer than the diesel engine.

Add to that, any improvements made (i.e. variable valve timing to help reduce throttle losses, or friction reduction methods) have probably been eroded again by all the added weight modern cars carry. Weight kills acceleration and kills your fuel economy.

Having said that, I think the swing is now coming back to petrols.... they're getting DI and there is a supposed part load running mode known as HCCI, or Homogeneous-Charge Compression Ignition. Its a method of making sure the air and fuel is mixed homogeneously (i.e. the same everywhere) and then it can be compressed to combustion like a diesel because the flame will develop evenly across the cylinder. This should give petrols - diesel like efficiencies. Included with that theres been laser induced ignition systems to help with this and lately, plasma/corona ignition systems which help initiate and control the fuel burn better (this is a BMW thing and they have yet to release a paper on it, though I have seen said paper).

So petrol, is coming back IMO.... but we risk ending up with a similar situation to diesels in that the engines have complex air handling systems, high pressure direct fuel injection (though an order of magnitude down on diesel) and a whole raft of exhaust after treatment technologies. I mean with the future EU emissions regs, they plan on regulating particulates based on number, not mass, as in counting each individual particle!! (because the ultra fines are so small you can't weigh them). So petrols may also end up with the bane of the particulate trap. Thankfully it won't fill up anywhere near as quickly as a diesel!

[Otispunkmeyer]

durbster said:

penryar said:

MrKipling43 said:

5lab said:

also, 37 to 44 is a 20% increase, which isn't too bad

I reckon they've also probably doubled the service interval between those two motors. Further savings.

Whilst also dragging around 33% more weight as well.

Not impressed Im afraid.

My PC at home is something like 10,000% faster than the computer we had in 1990, and probably uses a similar amount of electricity

Yes but computers have Moores law (and its related laws) to help that along. Exponential increases in transistor counts leading to similar increases in capability and performance for same or cheaper costs. We don't have that for the good old IC engine.

[J4CKO]

Petrol engines have got more effecient but the gains have been used in providing more power to move heavier cars, not that most cars were that bad anyway, carbs were a bit limiting but well set up they did the job well, but never as well as a fully metered fuel injection system can, thing is though that physics play a big part and whatever you do it will always take a given amount of energy to accelerate a car of a certain weight to a speed, the gains like stop/start are basically just the manufacturers realising there is no big bang to fuel economy now, its all small, incremental improvements to get 1 or 2 mpg, all the low hanging fruit has gone.