Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) A view on GDI engines

If only Ford could do a nanny engine and also a cossie engine as in the old fashioned sierra cosworth , power outputs of 500bhp from a 4cyl , for folk that want to drive ...

Like Bob I am. Thinking of a change to GDi and have found this thread informative thanks so contacted the head of service dept at the factory. I am amazed at the response ! He had not heard of any problems with these engines. Now I would have thought the technical dept might have done some research into these engines having to install them. in preparation for any issues arising from them later. This 'if at ain't broke don't fix it attitude worries me!
RogT 4/4 sand

I rather suspect that all staff are told to deny there is a problem with anything, as a matter of course, probably down to legal liability In this day and age.

Look at the Three Wheeler debacle over the last few years, for an example of this.

When I was looking for my MOG I had initially thought of going for new, and enjoyed two test drives in GDI engined plus 4s. However, I was concerned about reports of potential valve burn-out on GDI type engines and so tried out an older Plus 4. I could not notice a difference in performance, and so opted for the proven engine. From reading all of the above, it seems to have been a good move.

Direct petrol injections have long been troublesome. Ford, Mitsubishi and Vauxhall all abandoned their first forays into this market due to technical issues.

I was hoping that Ford had cracked the problems on their second attempt, but only time will tell.

As you might expect, Googling GDI problems brings up a lot of hits, but this one summarises the issues........

“Ask an Engineer” is hosted by Andrew Bell, a mechanical engineer and car enthusiast. Andrew has his MASc in Mechanical Engineering from the University of Toronto, and has worked on Formula SAE teams, as well as alternative fuel technologies in Denmark and Canada. Andrew’s column will explore engineering topics in the most accessible manner possible.

Even though every other car nowadays seems to offer gasoline direct injection (GDI), Mercedes-Benz was the first to exploit this technology in the 1955 300SL. But it wasn’t until the mid-1990’s that other automakers started to use GDI in mass produced vehicles. GDI promises marginal increases in fuel economy (3% reduction in BSFC ) but its real benefits include reduced cold start/low load emissions and higher power outputs. While the technology offers engineers incredible flexibility from an engine design perspective, it is not without faults. As with any new technology it is important to understand both the positives and negatives before you choose, say a compact car with GDI or one regular fuel injection. If you want to keep your car for a long period of time, the long-term reliability of a GDI engine is an important factor.

The effect of increased percentages of ethanol on injector longevity.

The percentage of ethanol in gasoline at the pumps is steadily increasing. Ethanol has a tendency to increase the corrosion rate of the various metals used in an engine. Add this to the elevated fuel pressure and the fact the injector is directly exposed to in-cylinder combustion events, and you have a recipe for a recall. Furthermore, these injectors are very sensitive to fuel quality due to outrageously tight tolerances. It is very important to use high quality fuels and keep the filters clean.

Higher pressures in general.

GDI requires significantly higher fuel inlet pressures than port injection. This puts a great deal of strain on every piece of the fuel delivery chain. This is not a problem on a new engine. 50,000 miles down the road, and it may be. Manufacturers have been relatively proactive in this department by specifying robust, stainless steel fuel lines and connections. That hasn’t stopped fuel pump recalls from already occurring

Carbon buildup on intake valves.

This is the big problem with most current GDI engines. Due to modern unburned hydrocarbon (UHC) regulations, vapors from the crankcase are usually vented into the intake stream in order to prevent oil droplets from escaping through the exhaust. In a port injection engine, these droplets are ‘washed off’ the neck of the intake valve by a relatively constant stream of gasoline droplets. In a GDI engine, the gasoline doesn’t touch intake side of the valve. As a result, the droplets have a tendency to bake onto the valve and significantly reduce performance. To add to this effect, many advanced GDI engines also include exhaust gas recirculation in order to lean out the combustion mixture and reduce in-cylinder temperatures for certain combustion modes (reducing NOx emissions). Since GDI combustion has the ability to produce far more soot than premixed combustion (port injection), the problem is magnified.

Even more alarming is that these deposits can dislodge and damage other downstream components (turbochargers, catalytic converters, etc.). Manufacturers have added systems to capture these oil droplets and particulates, but no system is 100% effective. As a result, there are many disappointed early adopters with large repair bills. Even diesel engines haven’t been immune to these issues.

The reason these issues have slipped through to production is that they won’t show up in a 500,000 mile torture test. These types of issues will appear after years of short trips (preventing the engine from reaching operating temperature), bad batches of fuel, etc. As we approach the efficiency limits of the internal combustion engine, the engines themselves (and associated support systems) have become more complex. As with the transition from carburetors to electronic fuel injection, there will be some overlap between relatively bombproof port injected engines and the unproven, first-generation GDI engines.

Thank you for sharing Dave,

I'm wondering why I have not found this section in the Mercedes prospect when I bought an E250T GDI three years ago...To be fair she still runs quite good with 70000 km on the clock and maintanace only. How much more, no one knows...

Dave,

I know GDI motors are relatively recent, at least in mainstream production, but all diesels are direct injection, so DDI.

The crankcase ventilation requirements have been about for at least 10, possibly 15 years. So all this time diesels have been dealing with oil vapour passing the inlet valves, without any fuel to keep them clean. We don't hear about the inlet valves caking up.

So why should GDI engines be any different? Doesn't make sense to me.

Peter, I should imagine it has something to do with the much greater lubricity of diesel - it is kinder to high pressure fuel pumps and injectors. Petrol by contrast has no lubricity which is why it needs detergents and other 'premium grade' additives to work well in GDI engines (and even then the long-term wear characteristics are unproven)

For anyone contemplating a future upgrade path on a petrol engine, they might want to bear in mind that in-cylinder high pressure injectors can't be re-sited in throttle bodies - that would be enough to put me off!

Lots of problems with modern VW Turbo diesels caking up the undersides of intake valves at low mileages.

One of the reasons for very high spec oils being demanded by VW.

eddie