Hi all. I’m in the process of converting my stock 1.7 to a big bore 1.9 and was looking to keep the stock fuel injection system if I can. I would just like to know if this is possible and how the original FI is tweaked, do I need to fit bigger injectors and mess with the throttle position etc etc. I’ve been told it’s possible but would like more detail so that I can continue. There must be quite a few out there that have done the big bore so hopefully someone will jump in. Thanks.

Oh yes, very possible.

Zach, thanks for the reply but I would really appreciate a bit more detail.

Damo,

I don't know the answer exactly for a 1.7

when folks put the 96mm bore pistons into a 2.0, they use the stock injectors but change the mixture through tuning of the MPS

to appropriately tune it... you need either the old, rare, and expensive device bosche used... wavetech, I think... but then the settings for that device would be appropriate to stock and stock means 1970 fuel additives and fuel that was sold then

today the fuel has changed. So I would argue that you need the 2nd method to tune to todays fuel. That would be a wide band o2 sensor to essentially read the fuel mixture under load, while driving the car and adjust the MPS settings to bring the AF ratio into spec for todays fuels.

I can't weigh in with any experience on if you should use the stock yellow 1.7 injectors or switch over to the 2.0 ones...

the 2.0 MPS also has an extension ring inside of it that allows the diaphragm slightly more range of movement to meet the 2.0 needs...

I'm not sure if you will need to fully open the 1.7mps and add that spacer or not?

hopefully this bump will bring you that answer about the MPS and about which injectors to use

brant

It's mostly dependent on the cam, you have to use a FI compatible cam, stock, WEB 73 and there's a flavor from T4store.

congrats to zach for the most useless post of the day.....

I think Zach knows from experience. So, well, let's see if he has more to say?

Yellow injectors will work, but many people swap out to the 2L ones.
gotta keep the stock cam, compression, etc.
When you do the heads, have your machinist use 2L valves. Or buy new heads from Len. Either way, of your entire build, almost all of the money should be going into your heads.
There are a couple guides on 914 World about how to set the MPS.

Do a search for +1911 +mps and you will likely find one of the threads that tells you how to adjust to get djet to be happy.

@racerchris also (I think) sells them pre-adjusted.

Zach

Time it.s all said and done for a 1911...might as well go to 2056.

Just saying.

I disagree, unless you have to spit your case for some other reason.

If you suspect your bottom end to need work, then yes go get the 2L crank. If your bottom end is suspected to be good, don't split the case... don't touch it!

That will open a larger can of worms that will add a few grand to the overall build price when you consider the new bearings, new cam, 2L crank, machine work, etc.

Zach

I drove a 1.7 with npr kit for 30 years. Didn't tweak anything. Ran great, and got 30+mpg

the fuel injection works perfectly with the big bore kit no reason to change anything, maybe a 270 ohm resistor between the head temp sensor and the wiring harness if you are putting your foot into it

I.f your gonna do a 1911 I.d ditch the D.jet and use L.jet with rebuilt 1.8 heads.

To try and make the 1.7 set up work is.nt worth it BTDT.

You can make it work....yes.

But the gains using the 1.7 D jet setup isn.t.

Quite a few mixed opinions on the stock set up but addition of big bore then ? I value all of the comments made and I’ll look into the set up further, that said this car will only be driven occasionally but would like to know that it responds well when needed ( for the grin factor ) I’ll keep it all stock including the heads and post on here in the near future how it pans out.

I drove a 1911 for a while - I now have a 2056.

the 1911 had a carb conversion..... and you know what? I LOVED that motor!

FI is great..... but don't discount the carbs. they worked well and looked great.

Just a thought.

Good luck!