Know anything about GDI jap-spec motors?

[MrBishi]

I'm looking at a couple of NA mitsu motors that are GDI (Gasoline Direct Injection). They look whacky, but seem to get good HP stock. The motors I am looking at are N/A stock and I'd like to add boost.

Can the injectors be upgraded? Does the fuel system need to be extra high pressure to overcome combustion chamber pressures?
Any ideas on where to get more info on them particularly modification-wise?

[jakobsladderz]

GDI injectors are high pressure (much higher than the 2-3 BAR run in port injection, maybe more like 20-30 bar). They are of very different design to port injectors and require much higher driving currents and different control algorithms. There are probably not that many types around but because they are designed to be able to inject late in the cycle they are mst likely a lot 'bigger' than would be run for port injection.
Adding boost should not in itself be a problem but the issue is after a small amount of boost (if the factory computer will not crack it with you) you'll run off the edge of the factory maps. I have not yet seen any aftermarket ECU's that work with GDI systems. Correct me if i'm wrong of course (I haven't done any research recently on it).
Tuning a GDI engine for homogenous mode (fuel injected in the intake/compression cycle to get stoich mixture) should be similar to tuning a port injection. tuning for stratified charge mode (inject during compression just before firing so there's only a small flame for economy purposes) is a whole other ball game, but probably not necessary unless you're aiming for absolute max economy..

In short, it would probably be easier to start with a port injection motor unless you were keeping the GDI engine mated with the factory computer or possibly using it with a multipoint port injection manifold and an aftermarket computer, thereby negating the point of having the GDI injectors at all....

[MrBishi]

Thanks.
I have a Motec M800 to drive it, but I really have not done any research so far on making it work or if the motec will run them.
I think I am probably better off with a traditional port injection setup.
For those wondering what we are on about see below. Note the inlet manifold that feeds in between the 2 cams on each bank. The injectors and coils are buried in the spaghetti somewhere.

[STARZILA]

Ive heard they arent the most reliable engine.Problems are mostly due to excessive carbon build ups.
Parts that are most likely to give problems on a gdi are
Injectors
Throttle bodys and manifolds carbon up and stuff them
GDI high pressure fuel pumps.
Some people even say GDI stands for guaranteed dealer income.
Be carefull. :P

[mrb1]

There are turbo GDI engines I think you should look out for one of those instead.
You need the high power injector drive box otherwise you cannot drive the injector properly. This is tiggered by the ECU and runs the injectors at approx 100V. YOU WILL NOT BE ABLE TO DRIVE THE INJECTORS WITHOUT THIS BOX.
I am not sure where this injector drive box is mounted in the car maybe on the firewall or inner guard anyhow they are never with the engines.

Also with "in-cylinder" injection you must control the injector timing correctly.
These engines have a radical inlet port design down through the top of the head which offer approx 10% better flow than the traditional setup. However I don't see any reason why you could not do a custom inlet manifold and convert to port injection. With a N/A engine you could have 4 trumpets straight up through the bonnet!!!

These GDI engines are all the later style 4G63 with the different oil drain passages in the head which will not fit our blocks.
These engines are setup for high flow EGR as well.

The GDI injector drive box looks like a big ignition module. With a bit of mucking around you should be able the get the Motec to trigger this box.
There is nothing stopping you running these engines with a normal tune (ie normal AFR) even though they are optomised for lean burn cruise.

All in all a very interesting engine. I have been waiting for a few to turn up in containers (I know the japs sometimes through in extras) so I could get one at the right price to play with. Because they are completely useless for anything here.

As I said at the start try and get a turbo version. They came out later than the N/A motor so I guess are less common at the moment.

[MrBishi]

There are turbo GDI engines I think you should look out for one of those instead.
You need the high power injector drive box otherwise you cannot drive the injector properly. This is tiggered by the ECU and runs the injectors at approx 100V. YOU WILL NOT BE ABLE TO DRIVE THE INJECTORS WITHOUT THIS BOX.
I am not sure where this injector drive box is mounted in the car maybe on the firewall or inner guard anyhow they are never with the engines.

Also with "in-cylinder" injection you must control the injector timing correctly.
These engines have a radical inlet port design down through the top of the head which offer approx 10% better flow than the traditional setup. However I don't see any reason why you could not do a custom inlet manifold and convert to port injection. With a N/A engine you could have 4 trumpets straight up through the bonnet!!!

These GDI engines are all the later style 4G63 with the different oil drain passages in the head which will not fit our blocks.
These engines are setup for high flow EGR as well.

The GDI injector drive box looks like a big ignition module. With a bit of mucking around you should be able the get the Motec to trigger this box.
There is nothing stopping you running these engines with a normal tune (ie normal AFR) even though they are optomised for lean burn cruise.

All in all a very interesting engine. I have been waiting for a few to turn up in containers (I know the japs sometimes through in extras) so I could get one at the right price to play with. Because they are completely useless for anything here.

As I said at the start try and get a turbo version. They came out later than the N/A motor so I guess are less common at the moment.

There is no turbo GDI V6 that I am aware of. You have my mind ticking over with some wild inlet manifold designs though.

[mrb1]

There is no turbo GDI V6 that I am aware of. You have my mind ticking over with some wild inlet manifold designs though.

Yes but there is a turbo 4G63 GDI :D
Yes you could make a totally radical looking intake with high mount normal injectors for sure :)

[STARZILA]

There is no turbo GDI V6 that I am aware of. You have my mind ticking over with some wild inlet manifold designs though.

Yes but there is a turbo 4G63 GDI :D
Yes you could make a totally radical looking intake with high mount normal injectors for sure :)

What does the 63 GDI turbo come out of?

We have a GDI V8 at work!!
Its in a mitsy debonair which is like an oversize daimante/magna! :P

[mrb1]

What does the 63 GDI turbo come out of?

As far as I know it's from a Galant.

[MrBishi]

We have a GDI V8 at work!!
Its in a mitsy debonair which is like an oversize daimante/magna! :P

That'd be the 8A80. Is it a bare engine or in a car? I'd love some pics if you can find time. If it's for sale PM me the price please.

[STARZILA]

Yeah I think thats the one. Its still in the car all complete. I'll ask if they'll sell it, but its been there for years-maybe its a keeper???
I'll take some pics 2morrow for you.

[Powerslave]

Hey Anthony , If you can find out the impeadence of those injectors , it's really easy to make an inline driver circuit that will allow the motec to drive those injectors. The biggest risk is assuming that the fuel system uses high pressure fuel , then the injector cycle will be very short (anyone heard about the new mercedes solid state (quartz crystal) injectors on diesel engines running at 2000psi ???) , so their impeadence will be very low. This can damage the final output transistors in the motec. If you need to find this out and check with motec if they can be driven, PM me for how to check the impeadence. Note: Measuring the resistance off load will not tell you the impeadence!!!

:beer :beer :beer

[MrBishi]

Hey Anthony , If you can find out the impeadence of those injectors , it's really easy to make an inline driver circuit that will allow the motec to drive those injectors. The biggest risk is assuming that the fuel system uses high pressure fuel , then the injector cycle will be very short (anyone heard about the new mercedes solid state (quartz crystal) injectors on diesel engines running at 2000psi ???) , so their impeadence will be very low. This can damage the final output transistors in the motec. If you need to find this out and check with motec if they can be driven, PM me for how to check the impeadence. Note: Measuring the resistance off load will not tell you the impeadence!!!

:beer :beer :beer

I'll chase you up when & if I get that far. I've only got so far that I think it will fit fit between the strut towers.

[mrb1]

Hey Anthony , If you can find out the impeadence of those injectors , it's really easy to make an inline driver circuit that will allow the motec to drive those injectors.
:beer :beer :beer

They use a 100V drive (external inverter injector drive box) with peak and then hold. NOT EASY my friend
You won't even open them with 12V when the rail has fuel pressure.

[STARZILA]

We have a GDI V8 at work!!
Its in a mitsy debonair which is like an oversize daimante/magna! :P

That'd be the 8A80. Is it a bare engine or in a car? I'd love some pics if you can find time. If it's for sale PM me the price please.

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Sorry dude.I asked about it and its not for sale as yet.