How much engine can the stock D-jet handle?? I'm considering a 2.0 longblock in my 72, presently a stock 1.7.

D-Jet is used on 2.0 (although components, most notably MPS, ECU, injectors, and CHT are different than the 1.7 versions). So you would need to source a fair number of D-Jet pieces. From what I’ve seen, 2.0 D-Jet can easily tuned (MPS) to handle 2056. But not much beyond that.

I upgraded my ‘72 to 2056. It was worth it.

So what you're telling me is that the FI on my stock 1.7 won't work with a 300 cc increase in displacement???? I have to replace the brains???? Really??? That seems crazy. It's that sensitive-- that --narrow???

I think you can increase to a 2.0l using the 1.7L intake parts. You will need 2.0L injectors, tune a MPS and bore out the 1.7 heads to fit and increase the valve size. Might choke off the high rpms a bit due to the slightly smaller intake runners.

Remember the 1970's era FI on these systems is not digital. No micro-processor, no digital memory, nothing! There is no mass airflow sensing to actually know what volume of air is being delivered.

Basically, an analog circuit designed to deliver fuel based on known engine size and air flow rates as delivered at time of manufacture.

Things can be done to trick the system (re-calibration of Manifold Pressure Sensor, raising fuel pressure, changing cylinder head sensor, etc) but none are sure fire.

ok Thanks for the info.. I was hoping to just throw a 2.0 long block in and go down the road. It appears that is not the case. Rethink is in order.

I think there are options to make later L-jet systems work better. Check posts and/or others will chime in.

There is also looks to be a really nice aftermarket FI kit for Type 4 engines from the DubShop but it runs $3.5K and get you into the digital age but you have to install, and be willing to do your own calibration tuning. I'd love to try it but will likely go to a six cylinder before I send that kind of coin on 4 cylinder FI.

The problem with both D-Jet and L-Jet FI for the 914s is the era it was designed. D-Jet really has no tuning capabilities, other than larger injectors and an increase in fuel pressure. L-Jet can be tuned slightly by modding the Air Flow Meter or putting in larger injectors.

Both limit the amount of cam overlap. Betty's car runs great when warm, but it doesn't stay running cold. The Raby 9590 cam is the absolute limit with the stock injection.

If you want to swap in a stock 2.0 for a stock 1.7, that is doable. But the 1.7 throttle body is too small for the 2.0, and you need bigger injectors. Best bet for doing that is to get the 2.0 D-Jet setup and put it on the engine.


Lots of good info out there if you want to search for it. I suggest using Google to search this site. It seems to work better than the built in search engine.

Just type into google "Site:914World.com" and then what you are looking for.

Thanks for all the info.. My 1.7 runs fine, just has a slight rod knock from my stupidity. Cold start after sitting a couple years, too long with no oil pressure. I think I will get the crank turned and go down the road. It has been from WA to CA and back, then to AZ in the last 10 years, none of that under it's own power. I just want to drive it again. It's going down hill from just sitting!!!!

No, you don't have to replace the parts, it will run a 2056.

It just won't run it optimally and may not give you the improvement you're hoping for (or worse).

D jet is a Speed-Density system, if the system knows the engine speed and the inlet manifold air density (pressure & Temperature) then it knows exactly what the cylinders are CAPABLE of injesting.
The speed is known exactly from the trigger points in the distributor that fire the injectors behind closed valves on the intake cycle.
For instance if you have very small intake valves or a worn out cam the cylinders won't suck in as much air as inlet density predicts.
The system is factory tuned to actual intake efficiency for each engine model so the injector pulse width is affected by this calibration. Cams with huge overlaps fool the mainfold density as air is backing up into the manifold so don't work very well.

So in short, yes, you can put a 1.7L D-Jet system on a 2056 with a stock cam and it will run, albeit not as good as one would want it to run, which is what i said in my previous post.

Been there, done that, wouldn't do it again ...

Ah I love learning new things. So , in essence , trying to make a 1.7 anything other than a 1.7 is fruitless. It's dialed in as a package. In my position , that's good to know. Makes my decision easier to make. Thank you Gentlemen. Fix the crank. Vroom Vroom

If you are taking it apart anyways you could get a 96mm P&C kit (1.7 heads would need to be machined) and take it up to 1911 and add a d-jet compatible performance cam. You might be able to squeeze an extra 10hp or so out of it. You could probably tweak the 1.7 d-jet to handle that without issue though as stated previously 1.7 intake and throttle body will most likely be your limiting factor as they are really tiny. I have first hand experience with this as I did a Megasquirt build for someone where we wound up using a 1.7 intake on a stock 2.0 motor and the throttle response was noticeably impacted. The 1.8 intake is a much better starting point as the intake runners are the same diameter as a 2.0 and the throttle body is larger as well. Theoretically that intake should be able to handle ~140HP maybe more but it would also require a little fab work to mount of the d-jet sensors. Bottom line a stock 1.7 isnt the best place to start to add performance cheap.


If I were you I would consider the following options:

#1 Cheapest - Tear down your 1.7, fix/replace the crank, add a d-jet performance cam, use your existing d-jet and be on your merry way.

#2 BUT Given you are looking at a rebuild anyways, 1.8 cores are a dime a dozen (ive seen people give them away) and are a better starting point for a 1911 build. The heads have larger valves, no machine work needed to accept 96mm P&Cs and the 1.7 intake is bolt on (2.0 heads have a different bolt pattern) Find a good 1.8, add 96mm P&Cs and a cam if you feel like splitting the case, run it with your d-jet setup, or even better find one with the 1.8 intake included and adapt that. May not even cost much more given the damage in your 1.7 is currently unknown.

#3 Get the 2.0 and source an appropriate intake and injection setup ($$$ and will only net you maybe ~15hp over the 1.7)

#4 Commit, and just build a 2256 with Megasquirt

I dont know what your overall goals/priorities are but after 20 years and 10+ 914s at this point if I was looking at tearing into a motor I would just go option #4. D-jet is a great system but you open up whole new worlds once you get into fully programmable fueling.

On the plus side, a 10-15hp increase on a 1.7 is also a 15-20% increase in power. Find some ways to drop some car weight and the butt dyno should feel the difference.

You want more performance....for least amount of $ spent
Tear down+ p/c + carb cam and carbs ....
( does have a distinct ) smells like gas




You want a tiny bit more performance for alot more $
Stick with f.i

Joe Sayere's 1.8 got rebuilt into 2056 running DJET that made 130 at the crank. it can be done and tuned if you have a person that know how to tune for it.

BUT...

My 2056 running MS2 EFI is making 150 at the crank (estimated, 127 at the wheels on the dyno). It was made from a 1.7 case and retained the 1.7 spark plug location.

If you stay with DJET, you will not have the best tuned engine once you start modding it. EFI will get more power out of your engine.

One last note - a big power 2L engine people won't last forever. If its a fun day car, it may last the rest of your life. If its a daily, it may last a few years.

Zach

I watched a member fight with a tricked 2270 trying to run with the stock 2.0 FI components, megasquirt and a larger throttle body. Repeatedly. In the end it was SDS and dual FI throttle bodies and all that went with them. You need an exhaust system to support the displacement too, $$$. Bring cash....a BIG pile of it.

How"s it goin? We met a bunch of years ago. I got a windshield from you I believe. I used to live on Whidbey. At this point I just want to drive it. Cheaply. Not worried about or interested in performance with this motor. Just forward motion. There's a guy in Mt Vernon, perhaps you've seen his 914, with a aluminum Olds or Buick v6 in it. If I wanted performance, I'd investigate that route. I've put a lot of work into it about 5 yrs ago , major hellhole repair, new rear floor pan, new shocks, new stainless fuel lines, Trans repair. Then life had some issues and it sat. I just want to drive it again. Ran fine till I cold started it and ran it too long with no oil pressure. Still runs , just a little knock.

How many times did Joe rebuild his engine?

Why not just drop in a complete 2.0?

Cause I'm cheap My 1.7 runs fine. It just has crank issues. I was thinking 2.0 long block, quick and easy. NOT the case. Gonna fix the crank and drive on.

1973 1.7 and 2.0 d- jet engines both used the same FI Control Unit.
Different MPS and Head temp sensor and injectors.

Check out pbanders djet site:
Pbanders Djet wealth of knowledge

Jim

Not quite the same. The D-Jet FI is very primitive, and the FI control unit is calibrated to the engine displacement. You need the right D-Jet control unit to match the motor.

Clay

Actually my point was that in 1973 they used the same control unit for the 2.0L D-jet cars as they had been using for the 1972 & 1973 1.7L D-jet cars. The same part number, same control unit.

For the 2.0L the control unit is paired with different head temp sensor and MPS, which I assume is to compensate fpr the engine displacement.

Jim

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