What can I do to rebuild my 1.7 for more HP and torque but keep the original d-jet.

piston and cylinders
crank
camshaft
heads
?

I know I can't change the cam too much but is there one that will do better and still work with d-jet.

I know there is modern FI but I'm not interested. No carbs. I'm not looking for all out HP or dropping 10K on an engine kit. I just want a nice bump in power, if possible, while keeping a stock looking engine.

Webcam #73
96mm KB's for 66mm crank and move up to 1800S heads. I'd guess 90hp max.
Headers would be a consideration, only true bolt on HP, but at your HP it won't be a huge improvement. Maybe 5%.

No replacement for displacement, consider stepping up to 2,0, but no idea how well it would work with 1.7 djet. L-jet works for sure and 2,0 djet.
I love the 2056 2.0 head Ljet combo.

I do have a set of nos mahle 94mm P&C's. Also have a 2.0 crank. I don't know if either of these will fit or work to improve power. I was hoping to see 100 but I realize the stock 1.7 d-jet has limitations.

Weight reduction (of the car) will also help to increase performance.

The big difference with Djets is ecu and injectors.

But for all that trouble might as well put it into that Suby....

Mark (E) I'm doing a similar build right now. 2056, webcam, Hoffman heads, and stock-djet. Not to contradict Mr. Henry (who has a world more experience than I will ever have), but I thought something like this was good for north of 110 hp. Maybe anything less than 200 to Mark (H) just looks like 100-ish

I guess we shall see.

I know a bump to a 1911 was always popular for 1.7s wanting more.. but the djet question is one I cant answer. I know 2.0/2056 with 100-110hp with djets were possible.. Are the 1.7 and 2.0 djets different?

FAT 440 MP camshaft is great with D-jet.

I think a good budget build would be 96mm pistons with 1.7 crank, lightened flywheel and FAT 440 MP cam. Send the MPS to Jeff Bowlsby for 1911 calibration. Have stock heads rebuilt.

Posted in the classifieds?, you amateur

I do kind of envy the built 1.7, they can be quick/high revving engines AND gas mileage! I like that.

Correct me if I am wrong, but the stock 1.7 made 88 hp in 70,71 according to brochure. They made it happen with domed pistons.

"Subscribing". My 2L street car is running nice with the stock D-Jet, but I heard that the system does not respond well to engine mods.

I also question how much more power you're going to get through that small single-port throttle body.

getting ready to build up my 73 1.7 next month.
This was perfect timing.
Thanks for the info

Just curious, has anyone built a motor with a 66mm crank and 100 or 101mm or larger pistons, like a short stroke 2.1. Is it possible? what would the characteristics of that set up be>?

i think that is incorrect. I believe my Stock early 1.7 was rated at 80hp. By 72 or maybe 73 they were down to approx 75hp.

Really might depend if you are looking at DIN, SAE, Gross or Net too as all were popular Brochure horsepower tools

Yea, my mistake.
@sirandy

My bad, I got on the wrong info line. 88 hp was for the 73 2.0. 76 hp is for the 1.7.

If your stick in with djet = stay bone stock

If you want to go above 60-70-80 hp

Then djet wont get you there

Stock 73 was/is rated at 80 HP.

I already have 94mm Mahle P&C's, 2.0 crank and a FI cam kit. I'm wondering if any of those things will make a difference if I rebuild the engine. If it's little to none, or not a combo that will work, I won't bother. If I could get another 15hp, well that's a 20% increase on that engine so It would be worth it to me.

I have a 250lb weight reduction planned (on paper) so a little boost with a much lighter car would make it fun.

I think you're right about looking at HP increases in percentage vs. looking at actual "big" numbers. When you are starting off with a relatively low HP number, I think it's unreasonable to look for high HP numbers with stock FI. I think 20% is a terrific goal and will be very noticeable.

The CA spec 73 1.7 was 72 HP, lower than the 1.8 believe it or not.

I wonder if you could build a 2.0 liter engine and use the 1.7 djet?

Leave it stock and keep the RPM's up. Those are sweet engines, bullet proof and often maligned. That HP bug is expensive once it bites you in the ass! You see where I ended up. Stay stock or get your billfold out.

No, I consider myself as a realist...I find hany HP claims to be exaggeration, or to be more PC let's say "overly optimistic".
1.7 djet FI cam with 96mm P&C's and headers, I very much doubt if you could break 100hp.



Mark the 2.0 piston have a different pin to deck height, by eyeball at least .200". You will find the 1.7/1.8 vs 2.0 rod length to be different a corresponding amount. Even 15% is a huge increase, factor in the weight reduction and it would make a fun 914.




It could be done , but at the dollar level this engine will cost to make good HP on a stock motor it wouldn't give enough reward for the bucks. Again there's no replacement for displacement.

Stock 1.7L at 8.2:1 compression ratio was 80HP (72 1.7 was 72HP)
Stock USA 2.0L at 7.6:1 compression ratio was 95HP
Stock Euro 2.0L at 8.0:1 compression ratio was 100HP

So stock 2.0 Euro spec is a 20% increase over a stock 1.7L 80HP engine.

Get rods to go with your 2.0 crank and pistons.

D-jet will have no problem with that size engine, many run D-jet on 2056 engines.

73 2.0L D-jet used the same ECU as 72-73 1.7 D-jet but has different injectors, head temp sensor and MPS.

Jim

That's beginning to sound like a plan. I do have 2.0 rods. If i only use premium grade fuel, can I move the compression to ~ 9.0.

No one told me no at the time, but said no after the fact when I had cooling issues. I expect your expertise would be greater than mine. Have to revisit my numbers, but I think I went 9:00 for the 2056 and have worried about head temps ever since. That led to rich A:F solutions. Would prefer stock.

Makes sense. 9.0 is still pretty tame on a 911 engine but I guess the 4's are more sensitive. I'll let someone more knowledgeable than me figure it out.

The static CR doesn't say much without considering the cam as well.
The engine heats because of the dynamic CR that's influenced a lot by the cam profile.
A longer duration for exhaust helps keeping the heads cooler.

correct.

I think you are starting in the wrong place. the goals you have are somewhat incompatible with each other. No matter what you do to the motor the 1.7 intake and tiny throttle body are going to choke any significant improvements. The d-jet system itself can be adapted (though you are limited on cam choices) but the intake is still going to choke the motor. I experienced this first hand when I hacked a Megasquirt system together using spare 1.7 d-jet parts I had on to my buddies stock 2.0 motor. While it turned out noticeably better than the progressive single carb he had, the results were still obviously sub optimal. Throttle response was awful and power was choked.

If you are set on keeping the 1.7 intake you can pretty much forget about anything else. If you are tearing into the motor anyways than maybe do the cam, if not than just headers and a good tune are probably your best bet. Personally I wouldn't waste the time and money for such little gain, stock 1.7 d-jet motors are great for what they are.

The 1.8 intake is a whole different story, its what I am running with a 50mm 2.1 waterboxer throttle body on my 2056. I think the fact that the factory went significantly larger on the 1.8 intake components despite the motor being only ~100cc larger is a good indicator as well that the 1.7 parts didn't have any room to grow left in them. You could probably adapt the 1.8 plumbing to work with your 1.7 d-jet system but after that customization plus the motor upgrades you would probably just be better off starting with a stock 2.0, less hassle but probably comparable cost and power.

If you are stuck on keeping the d-jet ECU you have to play within the d-jet boundaries. If your primary goals are stock-ish appearance and more power you should seriously consider a modern ECU. If your goals are keeping 1.7 d-jet + more power you may want to reconsider your goals.

Ditch the d-jet and you could do something like this:
Looks like a stock small displacement motor on the outside, but pulls hard to 7k RPM with HP calculated from acceleration datalogs showing in the 130+ range.

Click to view attachment

I think you have a good point, it may be a combo that just doesn't work correctly. The other option is to build out a second engine and make it a 2 liter from the start. Put my 1.7 in a corner.

You could always turbo

very interested in the specs/performance of this motor - is there a build thread link you can share?

Scott

OK.. I have to say it....


"You can't turbo a 914!!!"

Source a 2.0L bus intake and that keeps the D-Jet it flows more evenly that the stock 2.0L Porsche stuff did according the Jake. Bigger injectors, and change fuel pressure and get it dialed in. Jake was getting 2056s to pull what?

I would build it to a 2.0L and eurospec or even a slightly higher bump in compression.

And if you feel like spending the coin, Tangerine makes a great header.
taking weight out of the car is a lot easier way to do it.

Now if you're going to take every part and replace it or remake it to be lighter I'll subscribe to that build thread. Did I hear Titanium

What year chassis are you using ?
Where will the -250 lb come from ?

A ‘71

Here are some of the things I came up with to remove 250-300 lbs. not all of the items are practical, reasonable or cost effective but it was just spitballing while waiting on a flight home. A 300lb / 15% weight reduction would make a pretty good difference in acceleration, braking and handling without changing the brakes, engine or suspension.

10 - Firewall pad
10 - floor tar
60 - lids
10 - engine lid
5 - rockers
20 - glass bumpers
20 - targa top
5 - carpet
15 - exhaust
10 - Backpad
20 - air control
5 - door hardware
185
10 - Seat sliders
5 - interior padding
20 - headlights
10 - steel crossbar
10 - Heat flappers & lever
30 - battery and
5 - battery tray
265
20- Headers

310

Additional items-
Pedal board
Targa latches
Vent window & trim
Shortened sub dash
Sun visors
Glove box & ashtray
Trunk locks F & R
Glove box lock
Windshield wipers
Windshield washer
Trunk heat shield ?
Brake caliper shields
Radio & speakers
Engine lid latch & cable
Front trunk latch & cable
Front carpet board
Spare tire
Center tunnel covers
Shift knob
Antenna

Yeah, that'll do it.

No, you can’t. No one can. Save those engineers in the mist.

Funny. I made a couple of pedal boards out of alu honeycomb. No one was interested. But they weigh like a feather. A cheap router bit and the honeycomb.

Trying to think about everything that doesn’t make it stop or go but easily reversible mods.

Mark,
Here is the link regarding the plenums.2270 plenum test

I don't know if there is a difference in the inner diameters on 1.7 & 1.8 runners. I would use what you have., or get the flanges from the dubshop and make your own.
I did cc a 1.8 plenum and a 2.1 waterboxer plenum. The difference was minimal. The bus plenum will fit a larger TB without mods. It does have to be modified to install on the engine, remove and relocate the mounting tab, because the TB is on the opposite end.

I wouldn't rebuild the rods. When you add in the cost of balancing, You can get H beam rods with 2.0 journals. Much lighter and I will bet they come out of the box less then .1 gram difference.

The case and heads will have to be opened up for the larger bore.
You may be better served sourcing a 1.8 motor.

Carlos

We need to come up with a version of that where each word links to a successful turbo build thread....

--DD

See the various builds linked in my sig. Very happy with the current 2056, but mine ended up a little wilder than it seems you are thinking of going. It run stock sized intake valves, with big exhaust valves and a fairly big cam. I think the cool running of the motor is due in part to the cam, and in part to the 75% intake/exhaust valve size ratio.