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?

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

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.

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.

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.

"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.

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

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.

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!

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.

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.

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.

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.

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

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

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.

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....

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



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.





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

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.

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.

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.

OMG - are you guys even reading my post?

I already have the largest throttle body, largest plenum and largest runners. I asked about if anyone knew the limit of the factory components because I am switching to ITBs. I'm not asking about making an intake manifold, or adapting varioram, or changing the plenum, etc.

I've used ITBs on lots and lots of different engines over the years, and throttle response, when tuned correctly, is usually noticeably much better. I'm not asking about those things.

No. No one knows. Everyone that cares about performance goes to Webers IDFs, or Dellorto DRLAs, or dual-choke intakes and EFI.

The stock intake was designed for 100hp. OF COURSE it won't be as good as individual 40mm chokes. Duh.

Install the ITBs and be happy.

Are you reading my posts?



No one makes a 411/412 shorty intake manifold, so either you do a hack job to your engine hatch and stick ITB's out of the holes or you do the above.

It's a 412! There is no engine hatch!

Again - did I ask anywhere about fitting ITBs?

No.

Did I ask about what ITBs to use?

No.

Did you see my post where I talked about having used ITBs (in fuel injection and carburetor form) many times over the years?

Apparently not.

Moderators - I'm fine with locking or deleting this thread. There is no good info coming out of it and no good discussion about the topic.

I think we're done here.

But while I have everyone else's attention...will the 2L 914 TB fit easily on the bus plenum? You may recall - if you read my friggin post! - that I'm developing a system to fit on my 2L 914 per SCCA Limited Prep regs, which requires use of the stock unmodified throttle body. Everything else is free. So if the 914 2L runners are good, maybe I can adapt that to a better plenum and run from there.

I suppose I could look into modifying anything, or fabricating from scratch. Would much prefer an "easy button".

As a related aside, my 914 does have a decklid over the engine, so no clearance concerns.

Thanks!

From what IIRC the 914 2.0L intake setup flows pretty well until about 130hp. The Bus 2.0L plenum with mods goes past that due to its better flow (sidedraft vs downdraft) according to tests Raby did years ago. Your pic shows the bus setup so you are set.

IIRC that was on a 2276cc engine.

http://www.sdsefi.com/air12.html

Nice...that's some clean work right there.

That does look very doable, doesn’t it?

Greg, I have an SDS ECU if you want a real simple processor for your race car.
I thought the HP rules were for a 1.8L engine, in which case the 2L TB isn't the one you need to use. If you are allowed to use the Bus plenum and 2L runners (requires 2L intake bolt pattern on the heads) I'm sure the 1.8L TB can be fitted to it and altered to include TPS.

Just used short T4 Weber pattern manifolds match ported to heads but don't believe they are made anymore,sometimes see these in the FS section.
Click to view attachment.
They have a PITA outside bolt hole setup that requires much longer manifold studs but are otherwise a good casting.
Click to view attachment
I think the only real "bottleneck" in this engine would be the exhaust ,dependant whats been done to the exhaust ports a tuned performance header and muffler would certainly help.
Is it true the Vanagon (T25) has an even larger plenum body but the runners are still the same size ?,if so why not use that with a bored out 2L bus TB with larger throttle plate.
By the way Greg "chill out" no need for comments like that

From my experience the stock set up 2.0 will easily handle the airflow you are talking about, even with larger valves.
If you build a higher reving motor you would have some issues top end, but with you can selection the 2056 would be just fine.

I think since you have the IBTs every one thinks you are going that direction.

January Fastrack just came out; they rejected my request to run the 2L engine in H Production Limited Prep, stating it has "too much displacement".

I'm not taking the 1.8L engine into HProd on Limited Prep regs; I just don't think it has a chance there, starting with 76hp versus the 2019 champ's 91hp OHC 3-valve, and the 914 has to weigh 200 pounds more on top of that. Juice ain't worth the squeeze.

I think the killer car in HP now is the 2015 Honda Fit, which start with 130 crank HP and only has to weigh 150# more than the 1.8L 914. And we're going to America's Dyno, Road America, for this years' Runoffs.

I want to develop something for my 2L street car that could be adapted to the 2L race car, ifn' they ever changed their mind about allowing the 2L into HP using Limited Prep regs; to do that requires the 2L TB.

In so many ways this is why I got out of racing . . . too many rules that make no sense. Too much politics in making the rules.

If I wan't politics I'll watch the clown shows on the boob tube!

I am reading your post, and you dont have the largest throttle body

The late vanagon 2.1 throttle body is larger ~50mm

back to your question though, I dont have the sources in front of me but I remember reading at one point that the 1.8 intake flows enough for ~140+ HP. With the bus 2.0 intake being of similar design I would imagine it would be similar flow as long as you have swapped for the larger 914 intake runners. Personally I prefer the 1.8 intake + 50mm Vanagon TB to the bus 2.0+runner swap, basically trade some plenum volume for cleaner intake runner path. Not sure it makes much difference, its just an easier install and I like how it looks.

With a 2056 and 9550 cam I doubt you are giving up anything power wise with that intake setup You would need more exhaust and cam before the intake becomes the limiting factor. Throttle response is another story, ITBs may help there though I found with a LOT of work on the tune my throttle response is pretty damn good. You may loose some low/mid torque along with precision in your throttle control with the ITBs swap so that is something to think about. With 40mm ITBs you will maybe get about 20-25% of your throttle motion in the lower RPM ranges before you are basically WOT. For autocross I prefer having more precise throttle control, but that is just personal preference.


Click to view attachment

OK, just an update now that this thread has cooled down, lol.

I've got the VFR ITBs mounted, linkage modified and mounted, and using IDF velocity stacks that bolt on with a little filing to the mounting holes and line up very well.

Was this car in WA? I recall a car that stopped in I swear was identical.

I think you will find that the intake runners are designed for low-end torque. The runners must be shorter in order for resonance to enhance power output at higher rpm.

A solution is to install an interim plenum between two runners, effectively shortening the runner and raising the resonance frequency, allowing for better breathing a higher rpm.

The downside is that you will lose torque on the bottom end.

Hope that helps.

Yes, it was!! He built it and drove it for a a few years. Went to Canada, etc. Put some miles on it. Super well built and developed, especially for a VW 412 - custom bushings, 944 brakes, built transmission, on and on. Cool car. Now just needs some cleaning and updating.

The general consensus seems to be that the exhaust will limit you before the intake does. Switching over to a good tuned exhaust (like the Tangerine Racing one) will give you a very significant bump in power.

--DD

I'll be dyno-testing that in the Spring with the new engine. First tune it with the stock heat exchangers (Microsquirt w/ stock DJet TB, plenum, and runners) then swap to a Tangerine header and re-tune/dyno.

I wonder how the 412 heater boxes compare to the 914 ones. They are definitely shorter...