Intake plenum size 2.0 vs 1.7?, What is the diference? Options

[Joe Owensby]

I have a 2056, that I am planning to go back to FI from carbs. I have looked at several of the after market complete systems, but I think I would like to maybe have a stock type air plenum and intake runners. This would be with a new throttle switch, pressure and temp sensors, etc. , and then either a SDS or microsquirt controller. I am thinking more of overall day to day drivability, summer and winter, as well as fuel economy. I am thinking that the single plenum arrangement will be simpler to adjust and maintain than the dual throttle bodies. I am also thinking that it will be a little quiter. I now have the dual carb set up, and it sounds good if I am tooling around on country roads, but is annoying if I am cruising down the highway wanting to listen to the radio. I guess I am gettinng old.

If so, would I need to upgrade from a 1.7 D jet system to a 2.0 system? I have the old 1.7 system components from my engine. I was thinking that I should get a 2.0 plenum and intake runer system, then add new throtle switch, and other sensors, including 02, etc. I noticed the recent post on the microsquirt system which looked interesting. I am also not trying to start a debate on the merits of the different controllers now, just asking about the air management system. Are the filters, etc. for these still available? Thanks for any advice. JoeO

[type47]

i don't have experience in your plans but i would think you would need a 2L d-jet intake and filters for the 2.0L intake are readily available. also would think finding used would be easy. now, instead of getting a new MPS, why not go SDS or microsquirt now instead of later. do you now have 2L heads (3 bolt) on the motor?

[Dave_Darling]

A bunch of differences. The 2.0 intake runner pipes are shorter and wider diameter than the 1.7 ones. The 2.0 plenum is wider (that's why the 2.0 pipes are shorter), has a larger volume, and has the throttle body sitting on top of it instead of sitting on the side. The 2.0 TB is larger than the 1.7 one as well.

--DD

[sean_v8_914]

XCGV

[sean_v8_914]

...AND THE 1.7.

[Bleyseng]

2.0L set up for a 2056.

[Joe Owensby]

thanks for all the detailed info and photos. Yes, I am thinking of using either SDS, or Microsquirt, with a new throttle switch, pressure sensor, etc. The heads I have are from one of Jake's kits. They have the 4 bolts. I assume one can just drill the center hole and use a 2.0 intake on these? If so, I will post on the classified ad secton for the intake, air cleaner box, and hardware. Is there anything else I should get?

thanks again, JoeO

[Bleyseng]

Have Jake order them with the 3 bolt option as its welded in and then drilled.

Are you going to order them with the relocated sparkplug location? Adds about 5-10 hp.

[davep]

I recall someone saying that the 1.7 plenum flows better than the 2.0 due to its shape. Unless you are going for extreme HP (if you did, you probably don't want a plenum) then the flow characteristics of the runners would likely make no difference. Considering that, I'd be inclined to stay with the 1.7 parts you already have.

[Bleyseng]

Jake Raby has said the BUS plenum with 914 2.0L runners flows better than the 914 2.0L plenum setup on a dyno. Ok, maybe so but its gonna take some work to make it work so the stock 2.0L 914 setup is the easy way to set up FI.

now if you are going with MS, SDS or ? then maybe its just as easy to set it up like Jake. No way is the 1.7L setup as good as the 2.0l stuff as its much smaller reducing air flow.

[james2]

XCGV

The motor in the bottom picture, I have a EFI set up like the one installed, what is that system orginally for?

Thanks

[Jake Raby]

What the 914 2.0 plenum gains in size, it loses in design. This is when tested on my engine combinations, so it can't be generally applied as a blanket statement for all engines/cams/heads.

Joe's engine would benefit from a 2.0 Bus Spec plenum since that combo likes velocity more than gross flow.

The 2.0 Bus is the largest horizontal charged plenum and it's internals make for much better interal air delivery to all 4 cylinders. The 2.0/914 plenum favors the #2 and #4 cylinders more than 1&3 and this is notable with EGT data logging and head temps as well.

As always- Design trumps size. Smarter. Not Larger.

That always defys conventional wisdom concerning "Hot-rodding" and confuses lots of people.

I have used a 2.0 Bus plenum on an engine of 2615cc making north of 200HP at only 5,500 RPM.

[type47]

i would wonder how similar the "bus plenum" and the 914 L-jet plenum are...... buses were L-jet.

[james2]

Jake, I have a EFI system looks like the one installed in this picture, air filter mounts on top , not over to the side. side draft throttle body? What is it off of? picture hotlinked from above.


(IMG:http://www.914world.com/bbs2/uploads/post-3541-1218211493.jpg)

[Jake Raby]

James,
The plenum on the left is a 2.0/914. Its the only unit that has a vertical throttle body placement.

The other plenum is cluttered too much to absiolutely ID it, but it does look a 1.8/ 914 or 2.0 Bus unit based on what I can see in the pic.

[james2]

Thanks. (IMG:style_emoticons/default/biggrin.gif)

James,
The plenum on the left is a 2.0/914. Its the only unit that has a vertical throttle body placement.

The other plenum is cluttered too much to absiolutely ID it, but it does look a 1.8/ 914 or 2.0 Bus unit based on what I can see in the pic.

[Jake Raby]

Hey James, if you want to make a trip to the mountains I could use a hand in the new shop.... I added another 3,500 square feet and it's two stories high :-) (and we now have a chassis dyno!)

[james2]

Wow, it would be nice, call me Monday.