WTK About GDI

[nortel]

People I'm hearing about this GDI thing. Some people says that its bad and some saying it's good. Can someone give me an insight what it is all about?

[ronsin1]

if yuh don't know what you doing it can be ah pain


I have never had eny problem with mine one of the main reasons I ensure servicing is done on ah timely basis


check through the mitsubishi forum you will find alot of info on it

[nortel]

ok thanks. I'm looking at investing in a Mitsubishi Galant but I'm seeing different comments about the GDI aspect so i was wondering if having GDI is good or not but I'll love throught the Mitsubishi Forum and see what i can dig up. thanks.

[bushwakka]

GDI= Gasoline Direct Injection............it is one of the first Direct Injection systems to be employed in vehicles and it is a Mitsubishi Technology.......different manufacturers have their own injection technology like DI for mazda and FSi for Skoda, Volks and Audi

Direct Injection enhances the efficiency of an engine by directly injecting the fuel into the combustion chamber as opposed to Multi Point Injection where the fuel is pre-mixed with the air and then fed to the chambers

Direct Injection systems can be more problematic to maintain, but treat them well and they will serve u will in return.....

i hear it is also more difficult to perform mods on these types of engines, so beware

jus do a wikipedia search on the topic an u'll get lots more info

[ryansouthman]

http://mitsucrew.com/forum/viewtopic.php?f=3&t=656

Here is some useful information bout the GDI tech.

[thegtiman]

GDI= Gasoline Direct Injection............it is one of the first Direct Injection systems to be employed in vehicles and it is a Mitsubishi Technology.......different manufacturers have their own injection technology like DI for mazda and FSi for Skoda, Volks and Audi

Direct Injection enhances the efficiency of an engine by directly injecting the fuel into the combustion chamber as opposed to Multi Point Injection where the fuel is pre-mixed with the air and then fed to the chambers

Direct Injection systems can be more problematic to maintain, but treat them well and they will serve u will in return.....

i hear it is also more difficult to perform mods on these types of engines, so beware

jus do a wikipedia search on the topic an u'll get lots more info

Who needs wikipedia.
GDI, FSI, TFSI, SGDI, DISI are all acronmyms for the same type of technology.
Bosch was the first to implemennt direct injection. Mitsubushi was the first to implement it on a passenger car in the mid 90s (Carisma) with help from Bosch.
With emissions, increasing vehicle weight, customer and marketing expectations, DI(direct injection) is set to become main stream possibly giving diesel engines a good fight for fuel economy with the reviness of a petrol.
With DI petrol eengines you can run multiple injections and high injection pressure for cold starting which will reduce HCs CO, NOx and wall wettingbduring open loop fueling and catayst light off. In part load conditions there is the option to run the engine in stratifed mode where a lean injection is injected in the suction stroke and a second richer injection is performed, near TDC ( after when cold starting ) almost at the the time the spark plug arcs. The fuel is wall, air or spray guided so that the area right infront of the plug is at lambda 1 and leaner outside the fuel spray kernal. When the plug fires, the rich mixture combusts and consumes the leaner mixture previously injected on the suction stroke. The exhaust AFRs when in this mode can be as lean as 30AFR meaning a NOx trap is needed added cost to the unit( car). This is still being researched and not presently implemented by OEMs.
As you are injecting fuel at up to 150Bar in the compression stroke, this action cools down the chamber, thus increasing the det limit. You would also find that DI engines run high compression which helps in torque or response.
This concept is slighty different to PFI engines but can be modified if you understand the principle behind it and have a tunable engine module.
You would find that OEMs to day tend to run their engine at lambda 1 right up to 4000rpm then switch to open loop fuelling for Full load. ( 13-12.5 AFR). Rich mixture could potentially yeild more torque so this is an area to that can optimised to your car feel much more responsiver if you how to access the PCM.
However the GDI EC51A Galent was not a car designed for GT performance. It is a family cruiser similar to a Passat, Vectra, or 5series BMW. Yes I know it revs to 7000 rpm. But this has always been the Japanese philosiphy. Rev the torque hard!

[ryansouthman]

Mitsubishi is currently the leader of GDI (Gasoline Direct Injection) technology. It has already applied GDI in different engines, from 1.5-litre four to 4.5-litre V8. Now most of its production engines are GDI-equipped.
Mitsubishi claimed GDI consumes 20 to 35% less fuel, generates 20% less CO2 emission and 10% more power than conventional engines. How can it be so magical ? The following paragraphs will tell you its secret.

Theory of GDi

Gasoline direct injection technology is one of the branches of "Lean Burn Technology". What it differs with Lean Burn is the adoption of directly fuel injection system.

Direct fuel injection has been used in diesel engines for many years, but not in petrol engine until recently. Inherently, direct injection has two advantages :


Since the fuel is injected under high pressure directly into the combustion chamber, just before ignition by the spark plug, this allows the precise control of charge stratification vital to ignite ultra-lean air / fuel mixtures.
Direct injection also dispenses with the need for a throttle, so eliminating the pumping loss associated with drawing air around a conventional engine's butterfly valve.
.
In conventional engines, fuel injectors, even in MPi (multi-point injection) designs, the injected fuel pulverise in the intake port (near intake valves) before entering the combustion chambers. Why not directly inject into the cylinder ? because it is impossible to spread the fuel uniformally in everywhere. On the contrary, inject into the main entrance (intake port) assures all air mix with fuel in the same rate.
How can Mitsubishi applied direct injection without such problem? Let us look at the following diagrams:



Unlike conventional engines, GDI uses upright straight intake port, accompany with a concave-section piston surface, swirl air flow will be generated during compression stroke. When fuel directly injects into the combustion chamber, the swirl helps mixing air with fuel.
The fuel injector is another new feature. It pumps out the fuel at higher pressure, enables better pulverisation and more uniformal spread.

Fuel injection takes place in two phases. During intake stroke, some amount of fuel is "pre-injected" into the combustion chamber, cools the incoming air thus improve volumetric efficiency, and ensuring an even fuel / air mixture in everywhere.



Main injection takes place as the piston approaches top dead centre on the compression stroke, shortly before ignition. As seen in the above pictures, the concave-section piston concentrates more fuel around the spark plug, this allows successful ignition without misfire even when the air / fuel mixture is very lean. This explain why GDI can operate under fuel / air ratio of 1 : 40 under light load, which is even leaner than Lean Burn Engines. As a result, more complete burning is achieved.
More Power

Mitsubishi GDI engine has an extraordinarily high compression ratio of 12.5 : 1, this is perhaps the highest record for production petrol engine. The result is higher power output.

How can it prevent combustion knock under such pressure ? The secret is the pre-injection process. During compression, the heated air is cooled by the fuel spray, thus knocking becomes less easy to occur.

NOx emission

One of the few drawbacks of GDI engine is the higher NOx pollutant level. Luckily, a newly developed catalytic convertor deal comfortably with it. Nevertheless, USA and many developing countries cannot be benefited by it because their high-sulphur petrol will damage the catalyst.

Taken from Auto Zine Techinical School

[ronsin1]

great info here Ryan where did you get it

[bushwakka]

ryan....ah not opposing yuh for opposing sake eh, but where u come up wit de conclusion dat GDI is de best fuel injection tech? i see u talk abt the mitsu tech, but didnt compare it to the others like Mazda DI, VolksAudi FSI....not to mention those of BMW and dozens of others.........

[ronsin1]

man never said it was the best they say that mitsu is the leader in GDI technology just visit autozine.com it is ah technical school with alot of reviews on engines and engine technology

Just remember that GDI cot a bad name in Trinidad for the mare fact of the gas we have down here

[bushwakka]

^^^ummm....saying someone is the leader in something basically is the same as saying they are the best!!

so as i was saying.....

and its not only GDI thats gotten a bad name, its all types of Direct Injection engines, as you said, its the gas

if i want to be really technical, i'll say ryan is completely right since GDI is Trademark of Mitsubishi....so who else can be the leader of it? Just like how Volkswagen is the leader in FSI technology ent?

[ryansouthman]

^^^^^^^correcto.................... ronsin wa you go do boy, have to help a bredda out.....

[ek4ever]

One of the things to note about DI is that to obtain the increase fuel efficiency claims you are restricted to a relaxed almost constant speed driving. If you drive aggressively or at high speeds in most cases the engine reverts to stoichiometric burn...14:1 air/fuel.

Honda did a lot of research into this comparing DI to it's VTEC-E system and realised that it's VTEC-E gave better results than DI (less expensive and complex too). Honda did produce a DI engine....the K20B with iVTEC-I....it's an ultra lean burn @ 65:1 air/fuel but has discontinued DI in favour of VTEC.

There is great debate on whether DI contributes that much significantly to fuel economy. Much of it depends on adjusting driving habits too. DI found favour with diesel and 2 stroke engines where the technology improves the performance of these systems. With respect to gasoline engines the jury's still out.

As was stated in earlier posts...DI engines use different fuel supply systems (pumps, pressures, injectors, EGR valves, etc) so what you need to keep in mind is that parts and service may be more challenging and expensive

[bushwakka]

^^^indeed, it depends on ur driving habits, fuel economy aside, i still think there is a performance increase from DI engines...

and well, i thought it wud make sense to have a DI system coupled with some sort of VVT tech, be it VVL, VTEC, VANOS, MIVEC etc...

but if the guys from honda did the testing and concluded that VTEC alone is better than the both....well then there u have it

[ek4ever]

^^^indeed, it depends on ur driving habits, fuel economy aside, i still think there is a performance increase from DI engines...

and well, i thought it wud make sense to have a DI system coupled with some sort of VVT tech, be it VVL, VTEC, VANOS, MIVEC etc...

but if the guys from honda did the testing and concluded that VTEC alone is better than the both....well then there u have it

Yeah...maybe DI will be coupled to some other technology and produce the benefits it was being developed for. Manufacturers always have to look at the costs of introducing new technologies...what markets will support it, additional training, dealer servicing requirements, parts inventory, warranty support costs, etc....not a simple matter.

If you're interested take a look at this video

http://world.honda.com/HDTV/news/2003-4 ... index.html

[thegtiman]

DI engines that I am involved in developing, have independant variable cam control, most with Ti-VCT ( twin independant variable cam timing). You find most units now will have at least a variable inlet. Variable cams allow for internal egr and in cold starting are used as a emission control feature. At other engine conditions when up to temperature, they can be used for performance benefits or scavenging in the case of turbochagred applications. By controlling the cams to approach overlap during cold starting along with heavy spark retard and a lean mixutre of 1.05 lambda you can get heat into the cat to temps > 350º very quickly which start to absorb the pollutants. These procedures along with split injection reduce the feed gas pollutants to very low quantities give the cat less work and allowing for future and present emissions limits to be met. This task is something PFI engines currently struggle to do or cannot do in the case of multiple injection modes.
What you chaps have to realise is that the manufacturer claims fuel economy on a drive cycle. This is done on a a chassis rolls with simulateed road loads. The target FE is set based on the competition or selling point as well as how good the car performs in the drive cycle/development testing. It is not a real world thing as such.
The drive cycle differs depending on country which vaguely factors in local driving habits and target emission numbers of HC CO CO2 and NOx. If the car does not pass these targets set by legistration then you cannot sell the car. Its that simple. So Direct injection engines help to exceed these targets without compromising durabillty, OEM inuse requirements, and relative performance and economy.
Regarding closed loop lambda most OEMs today run around lambda 1 to near 4000rpm and full load. This provides the conversion window for efficient catalyser operation. Once outside this operating condition the engine tends to run open loop and component protection lambda around 0.9-0.85. As GDI motors run high compression, as explained in my last post, you get the benefit of extra torque vs a PFi engine of similar size and spec. This extra torque benefit means that a GDI engine can match the torque of a much larger engine giving further FE benefits needed to pass tests an market the product. Notice the EC5 Galant has a 1.8 DI motor vs a 2.0 PFI engine for regular models.

[bushwakka]

^^when u say YOU are interested in developing DI engines....u cudn't possibly mean u buildin one urself can u?

[thegtiman]

I never said "interested" in developing in them...
What was written above forms part of my day job.
Who knows soon you may be driving a Euro part-calibrated by me

[bushwakka]

^^oh yea, i forgot what u had said when i was posting......

well maybe if i get a euro car..

[ryansouthman]

[Alpha_2nr]

and its not only GDI thats gotten a bad name, its all types of Direct Injection engines, as you said, its the gas

if i want to be really technical, i'll say ryan is completely right since GDI is Trademark of Mitsubishi....so who else can be the leader of it? Just like how Volkswagen is the leader in FSI technology ent?

Actually Ferrari pioneered GDI technology like waaaayyyy back. But they kept it in use for their race cars only (read: Formula 1)

Also, as a point of interest, Nissan came out with GDI in their QG18DD engines around the same time, or a little after Mitsubishi started using them.

I have a daily driven Di car, and I have no complaints....gas quality or not. Regular maintenance is key, plus I don't use any of those bogus fuel additives.

From what meagre understanding I might have, problems with the Mitsu GDI's stemmed from the parts themselves (as opposed to the the technology)....flaws basically..... which were rectified in newer models.

As GDI motors run high compression, as explained in my last post, you get the benefit of extra torque vs a PFi engine of similar size and spec. This extra torque benefit means that a GDI engine can match the torque of a much larger engine giving further FE benefits needed to pass tests an market the product

Yup.

You would generally find that GDi cars tend to be a little more powerful, and have better torque bands than normal EFI counterparts.

E.g. The standard QG18DE puts out about 120 hp, and peaks torque at circa 4400 rpm (I'll try to find the link for these numbers).

The QG18DD (Di) engine puts out 130 hp, and peaks torque at 2500 rpm..with a relatively flat-ish band till 5k rpm or so.......

[thegtiman]

...The QG18DD (Di) engine puts out 130 hp, and peaks torque at 2500 rpm..with a relatively flat-ish band till 5k rpm or so....

This torque curve can be artificially created via calibration of pedel maps vs throttle angle as well as fine tuning of spark angle. This flat torque curve tends to be common among OEMs as marketing say this is what the general customer wants.
The Japanese all got assistance fron Bosch to have successful DI programs. They went in this direction as they emissions legistration (JULEV) was much stricter than Europe's Stage 3.

[bushwakka]

Knight1.....i'll repeat what i said.....GDI is the NAME for Direct Injection technology produced by Mitsubishi......if ferrari had a DI tech of their own, they didn't call it GDI or if they did it wasn't a trademark

[cjawahir]

Mitsubishi was the first to produce a car with direct injection .

Nissan second , now Audi and everyone else.

if you could find another before the lancer show me it .

cj

[Alpha_2nr]

Knight1.....i'll repeat what i said.....GDI is the NAME for Direct Injection technology produced by Mitsubishi......if ferrari had a DI tech of their own, they didn't call it GDI or if they did it wasn't a trademark

How can you repeat what you never said in the first place. you said:

GDI is Trademark of Mitsubishi....

Which can be interpreted as:

1) GDI - as in gasoline direct injection technology being a trademark/unique to mitsu cars

OR

2) GDI - as in "GDI" (marketing trademark).

You never specified that you were referring to the GDI MARKETING NAME> So please, understand what might be obvious to you...may not be to others.

This torque curve can be artificially created via calibration of pedel maps vs throttle angle as well as fine tuning of spark angle.

PedeL????

I assume that you're referring to an electronic throttle setup when you talk of "pedAl maps".

I also have no idea what the terminology "spark angle" refers to. Are you referring to Ignition timing, and advance?

[thegtiman]

My bad spelling lol!
Pedal maps work with ETBs and can be used to control the airflow through the engine which can be calibrated to limit torque per load speed point. You can also achieve similar results to a certain EGT threshold, with spark angle. The engine itself may be capable of more torque per rev with a different calibration, which will be validated by an engine performance and economy team of calibrators. The term spark angle or Zünden Winkel is the correct term on these engines as there are varying conditions, like split injection for cold starting and trailing throttle or part load where you can run both spark retard or spark advance.
I would advise to get hold of Gasoline Engine Mangement by Robert Bosch from 3rd edition and do some background reading on the evolution of engine fuel control then recheck what I said in this thread.

[ryansouthman]

[bushwakka]

knight, i won't continue to argue wit u.....there isn't a clearer way of explaining that GDI is mistu direct injection technology

this is like saying VTEC is not Honda trademark and everybody should be confused when i say VTEC is Honda Trademark Variable valve control technology....

[cjawahir]

Knight1, GDI is a trade mark of mitsubishi , you cant say a say a GDI nissan ,
what you can say is a direct injection nissan engine .

bushwakka, is correct .

cj

[ryansouthman]

precisely^^^^^^^^^