Seing double?, Now tested double D-jet performance! Options

[larss]

At last, after running in my new 1911 Engine I have now tested the performance of the double D-jet arrangement VS single stock D-jet:

Acceleration on plain road from 37 to 68mph in 4th gear was one second faster with the double arrangement (10 VS 11 seconds).

Tested several times on the same road with both systems, no wind etc.
My double system has an extra fuel enrichment at 3/4 throttle (by fooling the cylinder head temp sensor), my stock not.

Looks like Im removing the double arrangement due to the minor advance... (IMG:style_emoticons/default/sad.gif) also it is blocking access to #3 spark plug...

/Lars S

(IMG:http://www.914world.com/bbs2/uploads_offsite/www.lsmteknik.se-10787-1389339349.1.jpg)

[Chris Pincetich]

Cool! Thanks for sharing (IMG:style_emoticons/default/beerchug.gif)
I'll add this to my list of "potential ways my 1.7 can go faster" (right behind McMark's turbo). (IMG:style_emoticons/default/aktion035.gif)

[Dr Evil]

This is fricken cool (IMG:style_emoticons/default/smile.gif) Good on you for trying things and reporting them here.

The volume of your plenum can cause you some issues, too. I do not know how much and at what volume, but a larger plenum would be like a big room. If you open a door to a large room you feel nothing. If you open a door to a small room, you feel it more (if that makes sense).

Another thing is runner length. Longer runners make for more torque. How long and such depends on your displacement and other things.

When I was designing and building my intake system for the bus I had to take all of this into consideration. It helped that someone else had tried similar and their plenum was visually way too small and yielded crappy results.

[larss]

This is fricken cool (IMG:style_emoticons/default/smile.gif) ....

The volume of your plenum can cause you some issues, too. I do not know how much and at what volume, but a larger plenum would be like a big room. If you open a door to a large room you feel nothing. If you open a door to a small room, you feel it more (if that makes sense).

....

Thanks!

I had serious ocillating idle problems with my double system...may have to do with the plenum wolume, I cured i by making the idle-mixture (over)rich, lets see how it reacts when going back to single D-jet.


/Lars S

[Olympic 914]

What about just using the 2.0 plenum? it is larger, then just add the 2.0 throttle body. I don't know the size difference between the 1.7 and 2.0 throttle bodies.

[larss]

What about just using the 2.0 plenum? it is larger, then just add the 2.0 throttle body. I don't know the size difference between the 1.7 and 2.0 throttle bodies.

Yes thats a good idea, I think many have done that on 1911cc's. Best would be to use the larger 2.0 intake pipes also (and heads of course).
I just happened to have another 1.7 d-jet plenum and throttle body and wanted to make a test.

/Lars S

[JamesM]

What about just using the 2.0 plenum? it is larger, then just add the 2.0 throttle body. I don't know the size difference between the 1.7 and 2.0 throttle bodies.

Yes thats a good idea, I think many have done that on 1911cc's. Best would be to use the larger 2.0 intake pipes also (and heads of course).
I just happened to have another 1.7 d-jet plenum and throttle body and wanted to make a test.

/Lars S

Neat to see that you actually got a power increase from the larger TB area. I increased the size of the TB on my latest build as well but was not sure if it made any difference. I have run a 1.7 plenum/TB/Runners on a 2.0 before and it definitely restricts the power. From what I recall (and don't quote me on this)

1.7 TB ~37mm (also smaller runners and much smaller plenum)
1.8 TB ~45mm (same size runners as 2.0)
2.0TB ~46mm (largest stock TB, same size runners as a 1.8 but intake layout causes turbulence. Also 3 bolt runners vs 1.7 and 1.8 4 bolt)


The 2.0 intake requires a bit of hacking to fit on a 1.7, and still has its problems.

My solution, still looks stock and gets you a total throttle plate area pretty close to what you get with dual 1.7s, and also you keep equal length runners with the larger diameter.



1.8 plenum with the TB opening stretched to 52MM, + modified 50MM vanagon TB:
total throttle plate area 1962mm^2

on top of a 2056, does not seem to be lacking for air on the top end at all

[larss]

Good ideas JamesM!

How do you match the vanagon TB to the D-jet TPS?


/Lars S

[JamesM]

Good ideas JamesM!

How do you match the vanagon TB to the D-jet TPS?


/Lars S

You install megasquirt!!! (IMG:style_emoticons/default/smile.gif)

The throttle shaft size and shape are the same, though the vanagon TB the TPS side of the shaft does not extend as far out, looks like there would be enough to engage the d-jet TPS though. You need a plate under the TPS to be able to mount/set the angle correctly (same thing I had to do with the TPS I used on my Megasquirt setup). The Vanagon TB pulls in a different direction, so you need the throttle cable arm off of a 1.8 TB as well, basically just undo the nut holding the spring and arm on the 1.8TB and it all just bolts directly the Vanagon 2.1 TB. Got to love how interchangeable VW stuff is!

[larss]

Thanks JamesM!

Are we talking about a TB type 025133067A ...?

/Lars S

[JamesM]

Thanks JamesM!

Are we talking about a TB type 025133067A ...?

/Lars S

Let me see if I can dig up the part number again. It is the one from the very last vanagons, 2.1L watercooled

[JamesM]

Thanks JamesM!

Are we talking about a TB type 025133067A ...?

/Lars S

Let me see if I can dig up the part number again. It is the one from the very last vanagons, 2.1L watercooled

Yup, that's the one!

Gowesty sells ones that have been rebuilt to a 52MM bore as well, but then you lose the cool stock wedge throttle plate.

[larss]

Thanks JamesM!


/Lars S