Airflow/Horsepower limit for stock 2.0L intake system? Options

[greggearhead]

OK, I did search, and couldn't really find anything.

My basic question - when does the 914 2.0L intake become a restriction to power?

I have a built VW 412 -

2056 cc Type 4
* 9550 RAT cam
* LE-180 heads (914 2L combustion chamber, 42mm intake, 36mm exhaust)
* Mallory Unilite vacuum advance distributor, Mallory Promaster coil, Mallory Hyfire CDI
* Stock 412 heater boxes & Thunderbird exhaust
* 2L Bus plenum and throttle body
* 2L 914 runners
* Ford "Design II" F1TE-D9A (Bosch 0280150947) 24# injectors (modified)
* SDS programmable EFI
* Oil bath air cleaner housing modified to use large circular filter element


I have a pair of IDF manifolds, and some VFR throttle bodies. Roughly equivalent to Weber 40IDFs (maybe a bit better in terms of flow). Engine made 115hp at the wheels. I'm just wondering if the (improved) stock intake is a cork or not?


(IMG:http://www.914world.com/bbs2/uploads_offsite/i61.photobucket.com-12836-1576171976.1.jpg)

[johnhora]

Greg..please show us some pics of the 412....Thanks

[greggearhead]

I don't have any current ones, really, but I'll try to take some at the shop. The paint has faded since these and there is a parking lot bump in the left front corner, but you get the idea.

EVERYTHING in this 412 has been upgraded and built.

The trans was rebuilt, all the bushings were replaced with custom delrin, bronze steering bushings, BMW E30 M3 front springs, Audi 4000 front struts, double rear sway bar, Porsche 944 brakes all around, etc etc etc.

My plans are to install a Scheel drivers seat, better looking wheels (may require flares), fix the sheetmetal a bit, and drive it. May eventually sell, but it's a fun, unique little car.


(IMG:https://i61.photobucket.com/albums/h43/greggearhead/VW%20412/73%20412%20Coupe%204-speed_zpsqlqx1tap.jpg)

[914sgofast2]

Over on the Type 4 Forum I believe there was a discussion of which fi intake plenum was the best and it turned out that the best was the 2L bus intake and throttle body and the worse was the 2L Porsche 914 throttle body and plenum.

[greggearhead]

Yep, I think that's why he chose the components he did. It's not slow, just looking to make it faster and get that ITB intake roar.

If I do do that, I'll be selling this intake setup.

[GregAmy]

"Subscribing". I'm looking to EFI my street 2L 914 using stock intake but with stock engine internals; it's a test-project for maybe going limited-prep Production racing on the race car.

What the difference between the 914 and bus induction systems? Got a link somewhere? I can't find it with a cursory search.

[greggearhead]

https://shoptalkforums.com/viewtopic.php?t=143072

[Mark Henry]

If you had the room I'd make a plenum system based on the 996/997 intake.
Maybe up it to a 60mm TB.
If you made a removable center section, like the 996/7 you could experiment with different sized TB's.

[greggearhead]

That's a great idea, but this is a quick/no time type project. I've got lots of other projects to do cool stuff like that!

[rhodyguy]

Are the IDF manifolds tall or short ones? Same style engine cover as a T-3? Talls might be too tall with the bodies and filters added in. Nice sleeper. I think the carb drone could get old after a bit. The stock HEs might be a limiting factor but for a driver, mandatory. I would consider buying that car.

[greggearhead]

Absolutely nothing like a T3. At all.

Tall manifolds - only ones made for a Type 4 engine (same as 914 or late VW Bus basically).

I love the sound of open ITBs, carb or injection. Exhaust drone can get old. This exhaust is a bit loud, but very throaty.

[Mark Henry]

For the OP it's a tradeoff, the big limits for him is he doesn't have space for a much bigger plenum. Personally just smile and drive because that is what it is.
Everything is a tradeoff in building an engine... and intake and exhaust are part of that package.

I run 46mm gxsr bike TB's so a good machinist could cut the top off of existing T4 alunimum weber manifold and weld up a shorty base to adapt a bike TB or the CB performance TBs.It still won't be perfect, but it would work.

Nothing will beat ITB's for WOT, but plenum based systems pull better vacuum and are less likely to need to run in SDS's "TPS only" or MS "alphaN", both of which are basically the same thing.

AlphaN (TPS only) is great for the track and "shits and giggles" street roding, but gets old fast in stop and go traffic. With ITB's it has incredible pick up and engine braking, but you have hold the peddle real steady in slower traffic. Higher RPM's it has less of this effect but who wants to do stop and go at 4K+rpms.
A plenum system with a usable vacuum signal for the MAP sensor would dampen this effect.

[GregAmy]

https://shoptalkforums.com/viewtopic.php?t=143072

Thanks. Cliff's Notes: they prefer the 914 2L runners, the 914 2L TB is the biggest of the lot (not including Wasserboxer) and has TPS, but the flat-bottom 914 2L plenum causes a lot of air-mixing and moving around and turbulence and likely hurts power.

I bet that can be addressed with opening the plenum and welding in air deflectors.

[greggearhead]

Probably, but the setup on my car the PO put together is likely the best of factory components, except for the wasserboxer throttle body.

[Bleyseng]

If you are in search of hp I’d switch to bigger valves (44x38) and maybe LE200 heads

[greggearhead]

I'm not really in search of *building* more power, but freeing up some power (and cool sound) that's already there. The engine is solid, proven, and good enough for what it is.

It already is a stupid amount for build for a VW 412 - which is why I love it. Just trying to make it a little more me, and a little cooler.

[Mark Henry]

This is a 996 plenum.
So for a 914 this is what I would do except a bit smaller and 4 runners, to do this you would have to use most of the 914 bay and even remove the raintray to make it fit. It's the long match ported runners that are going make this work.
And then "you can't get it in, if you can't get it out", so something along the lines of a 1-7/8" tangerine header would be needed.

Hmmm... I have that header hanging on my wall.... (IMG:style_emoticons/default/idea.gif)

But as you can see the runners are quite long and wouldn't work for the 412.

(IMG:http://www.914world.com/bbs2/uploads_offsite/qsm.com.au-26-1576244074.1.jpg)

Then you could take it a step further with a plenum based ITB system, best of both worlds, a plenum based system with a usable vacuum signal and an ITB fuel injection system.

(IMG:http://www.914world.com/bbs2/uploads_offsite/impactbumpers.com-26-1576244075.2.jpg)



https://www.drivingline.com/articles/air-co...-intake-revamp/

[greggearhead]

I've done lots of research and flow bench work over the years - I know how different variable intake systems work. But as I mentioned, I'm not going to spend the time and money necessary to fabricate a one off intake like that for a mild 2056cc engine in a 412. Doesn't make any sense.

If I was going to go to that effort to extract more power, I would absolutely have to put in a more aggressive cam and heads. And then I could have just swapped in a Subaru and spent less money, and had something more powerful, more reliable and cheaper and easy to find if it blows up.

[greggearhead]

Can people still read the first post?

I'm asking about intake restriction or limit on the OEM type intake. Not about what I should do to change it, or how I should rebuild the engine to a higher spec.

[Mark Henry]

For the OP it's a tradeoff, the big limits for him is he doesn't have space for a much bigger plenum. Personally just smile and drive because that is what it is.

As you've been told, not much.
The bigger vanagon TB, bigger better exhaust, that's about it.
No magic wand we can wave over it.