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Converting Carburetor Engine to Direct Injection

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Hello to all of you,

I`m an automotive student who will have a graduation project of converting a FIAT 131 Old carburetor Engine to

a Direct Injection engine with tuning also.

so my question here as i`m not experienced.

can i put fuel injectors to this cylinder head of the engine ? or should i start designing a new one ?

Thanks in advance

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Does it have to be a direct injection conversion - port would be much easier.

You may have some one responding who is more knowledgeable, maybe who has worked on this very thing.

Some thoughts, though.

You should be able to find a low power engine that uses direct injection - port injectors aren't designed for the job - and measure them up to make sleeves that can be brazed into the head, taking into account the need to avoid compromising the water jacket.

The distributor advance can be locked, and the point's (contact's) cam modified to send a signal for camshaft position, with a sender of your preference.

You should be able to have a front pulley machined with teeth for the crank position and fabricate a sensor mounting.

You will also need to look at the piston crown shape, as that is a critical part of the way the fuel is introduced to the cylinder and is mixe with the air there.

However, after the actual head modifications, and piston, the hardest part may be finding a high pressure fuel pump for the injectors that can be driven from the engine - maybe an external using a toothed belt?

With port injection, the head and piston work can be avoided, along with the high pressure pump, and it would still be an interesting project requiring original design and fabrication work - depending on the study level, that may be an acceptable alternative and I'd suggest taking to your tutor/professor.

A thought - if you have the option, a switch to an engine with a "bathtub" combustion chamber may work better, as the injector may possibly be fitted oposite the spark plug, so the fuel can be directed closer to the spark plug, which should make ignition more reliable?

Again, not something I've any experience of, so if those who've worked on DFI and know the potential problems would comment, it would certinly help this chap with the project.

First of all, Thank you so much for your replies and i am sorry for not replying as soon as possible.

both Port Injection & Direct Injection we will try to do, but as you say port is easier so the challenge here is DI which seems so hard according

to Engine Material and other Stuff so a lot of modifications i think will be done in DI than Port Injection.

Bathtub Combustion Chamber old engines seems very hard to get here.

Yes, DI was developed by manufactures with E£Billion dollar budgets, teams of engineers, and the ability to build and test many different configurations - and the computing data-crunchers to do the basics virtually.

Even at doctorate level, with all the knowledge and resources avaialable, it would be a huge task to just get the engine running reliably, let alone well - and I think you're at a student level?

If you're still thinking of going ahead with it, I'd suggest using a single cylinder engine for this project, preferably one that's cheap and readily available, like a lawn-mower or small motorcyles engine. It's a normal practice for early engine development to be made on single cylinder engines because only one set of parts are required, and it's a fraction of the expense.

Yes i am a student level. Our project will go through Port Injection first to know some basics and get more knowledge into tuning and engine management.

But i just want to get ready as much as i can that`s why i am here gaining more information and try to understand it to the maximum.

So that`s why Direct Injection challenge is very good as i will learn a lot from it and know the differences between it and port injection in tuning and management.

There's very little difference on the fuel injection side as far as tuning and management is concerned, but there is a BIG difference in the hardware - head, piston crown, injector, etc - and if you are looking at this as a tuning aid it REALLY isn't going to be worth a fraction of the time and money you're going to be spending on it. That time and money may be much better served playing around with manifold designs, placement of the injectors, and basic tuning things like the affect the timing of the injectors has on torque/emissions/economy, etc.

But it's up to you, and if you do that route, I wish you well.

Yes i Understood you well.

Thank you so much for your information and helping me .

I appreciate it.

What ECU are you planning on using to control the DI system? A large percentage of the aftermarket ECU's are not designed to run the DI injectors as they do not have the hardware on board to generate the higher voltages and currents used (up to 180V and 25A depending on injector type) as well as having the crank synchronous control of the DI Fuel pump.

When we do a DI Project, we run the engine on the OEM ECU so that we can get all of the required injector characteristics from the OEM configuration, this allows for the characteristics to be replicated into the replacement ECU, not having this information will result in an engine that doesn't run and quite likely damaged injectors and/or fuel pumps.

I would recommend getting and engine with all of the supporting hardware (Loom, ECU, Pumps, etc) that already runs DI and use it as reverse engineering project and then apply what has been learnt doing this into a different engine.

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