The Truth About Cars » gdi The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. Tue, 22 Jul 2014 19:45:01 +0000 en-US hourly 1 The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars no The Truth About Cars (The Truth About Cars) 2006-2009 The Truth About Cars The Truth About Cars is dedicated to providing candid, unbiased automobile reviews and the latest in auto industry news. The Truth About Cars » gdi TUV Nord Testing Firm: Direct Injected Gasoline Engines Emit More Particulates Than Diesels Fri, 29 Nov 2013 11:00:14 +0000 particulate-filter-large

TUV Nord, a safety testing and certification agency, has issued a report commissioned by an environmental group that says that modern engines that use gasoline direct injection (GDI) of fuel emit more small particles in their exhausts than modern diesel engines. Particulates raise concerns over possibly causing cancer. GDI has proliferated as a means of increasing power, improving fuel efficiency and lowering CO2 emmissions but TUV Nord says that GDI engines put out 1,000 times more harmful particles than traditional gasoline engines and 10 times more than the latest diesels. The study is based on a sample size of three cars, a Ford Focus with a 1 liter EcoBoost engine, a Renault Megane with a 1.2 liter Energy TCe, and a Hyundai i40 with a 1.6 liter GDI engine.

“The cost of a filter to eliminate particle emissions from GDI cars is low (around EUR50 [~$68 US]), with no loss in fuel efficiency and a big societal benefit. Despite this, carmakers are delaying fitting filters on GDI cars,”  the Transport & Environment advocacy group based in Brussels said in a summary of the report.

Greg Archer, clean vehicles manager at Transport & Environment, said, “Cars are the largest source of air pollution in Europe’s cities and 90% of European citizens are already exposed to harmful levels of particle pollution. Carmakers’ reluctance to install cheap particle filters on GDI engines means that society as a whole has to pay the cost through more ill health.”

EU laws currently require particulate filters to be fitted to all new diesel cars but there is no requirement for gasoline powered cars. All of the cars tested by TUV Nord showed particulate emissions from GDI engines exceeding the 2017 European emissions limits, Euro 6. Fitting particulate filters reduced the number of particles in the exhaust by a factor of ~2,000, with results similar to those found in unpolluted air.

“More fuel-efficient, lower CO2 GDI engines would be a great innovation if they did not emit harmful particles. These particles can be eliminated for the price of a hands free kit. It’s time for carmakers to act responsibly and make petrol cars less polluting overall,” Archer said.

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Piston Slap: Hocus Pocus…Focus??? Tue, 29 Jan 2013 12:10:13 +0000  

Zack writes:

Hi Sajeev,

I’ve been following a series of discussion on a MK3 Ford Focus forum; in particular I’ve been following the technical discussion about how to squeeze more power from the MK3′s new 2.0 GDI motor. Of course, this involves talk of CAIs, Cat-deletes (inadvisable), and free flow exhaust. One of the more curious things to emerge is…

…the notion that re-gapping the spark plugs can account for +5whp. I’m dubious to say the least that something seemingly inconsequential could generate that much power. It’s almost seems akin to slapping turbo badges on the rear lid expecting some similar black magic. This being an internet car forum there is much breathless back and forth, but few actually explanations. I was hoping you might have heard of this “trick” and whether or not there’s any validity.

I think for questions like this we need a carforum, but then again we have you. Thanks in advance!

Sajeev answers:

You sir, have made my day.  Putting me on par with Snopes is a high honor indeed. That said, now I wonder if Snopes is as horribly inaccurate and clueless as yours truly on many, MANY occasions. (sad trombone sound)

Now about the spark plugs: I won’t say that a re-gap cannot possibly increase horsepower.  I will say that it isn’t very probable.  At all. Two things:

  1.  Spark plug gap can make a huge difference, especially in forced induction (turbo or supercharger) applications where adding extra boost is on the table.  But that low hanging fruit (i.e. extra power) is usually not there in factory setups: they normally hide the power in tame air/fuel/timing parameters in the engine computer’s tune.
  2. If it isn’t backed by a dyno sheet from a local tune shop, this is pure, un-stepped on, pharmaceutical grade bullshit.

Look, I’ve been messing with Ford products for a looooong time. And while not everything I do has been proven with dyno results, there’s always that low hanging fruit proven many times over with other’s dyno sheets: conservative factory computer tunes, intake boxes with inlet tubes significantly smaller than the engine’s throttle body and mediocre (i.e. quiet and restrictive) mufflers on inadequately shaped crush bend exhaust tubing (older models only).  The first is solved with an SCT tune, the second is free (remove something) or requires a trip to Home Depot for a slice of PVC pipe/glue/black paint,  and the latter is not a big deal with an exhaust shop and a muffler from a 2005-present Mustang GT.

But spark plug gap? The forums never show that as a credible performance modification.   Perhaps GDI motors are a game changer, but I doubt it.  That will be optomized to perfection by Ford’s engineers, the low hanging fruit will be the things mentioned in the previous paragraph.

Best and Brightest, you go right ahead and prove me wrong. Snopes ain’t got nothin’ on me. Or not.


Send your queries to Spare no details and ask for a speedy resolution if you’re in a hurry.

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Piston Slap: A Solution to our Coking Problem? Wed, 25 Jul 2012 10:53:00 +0000  


Kurt asks:

I’ve heard from maintenance shops and oil additive producers that DI engines, especially Audi and BMW, have severe problems with carbon buildup in their valve systems. Might be good to chat about this and also poll readers to see if other vehicles have the same issue. Thank you.

Sajeev answers:

Luckily a previous editorial in our “Ask an Engineer” series discussed this problem,  and it agrees with your assessment.  It also agrees with what I heard before GDI (Gasoline Direct Injection) motors were released in significant numbers here in the USA: my mechanic friend in the UK was the first to tell me about the walnut shell blasting method, discussed here. Using all his subtle British charm in describing his true feelings, you can say that he rather hates GDI engines.  And he’s probably not the only wrench to feel that way.

Which rather blows.  Because GDI (and Diesel DI) is a fantastic concept that makes perfect sense.  It is the next logical step in the evolution of the internal combustion engine. Hopefully we can find a way around engine coking, aside from the obvious answer: running at wide open throttle a lot of the time…that kinda defeats DI’s advantages over port-EFI, ya know.

I wonder if the latest GDI motors, especially the non-turbo versions in many a mainstream GM/Hyundai/Ford sedan, shall meet the same fate of the coke-happy BMW and Audi products you mentioned.

So my question to the B&B: how will technology overcome our coking problem?

Send your queries to Spare no details and ask for a speedy resolution if you’re in a hurry.

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Ask An Engineer: GDI Problems In A Nutshell Thu, 03 May 2012 13:00:11 +0000

“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.


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