1.6lTD long-runner intake manifold

[fspGTD]

While I had a head off of the engine and a scrap head in the garage, I decided to see how a long-runner A2 gasser intake manifold and an upside-down flipped exhaust manifold and turbo would look bolted onto the head in the engine bay...

pics of the long-runner A2 gasser intake manifold:


... looks like there is tons of room!


And here is the turbo exhaust manifold flipped upside down.  There are some ribs cast into what is the upper surface below that would need to be ground off in order for the gasser intake manifold to fit, so here I have it pictured by itself in the car (without the intake manifold)...


shift linkage interferes with the turbo compressor housing, but looks like the shift lever if bent "flat" could be modified to work... also, the compressor housing would need to be clocked for more clearance:

... also the air intake system would need to be re-done as it's on the opposite side of the block.

The center section of the turbo would also need to be  clocked to put the oil supply at the top, and oil return at the bottom.  There looks to be enough room for the oil return.  The turbo downpipe would need to be re-done but it looks like there might be just comfortably enough room:


...all in all, seems like a pretty big job all for "just" a long-runner intake manifold.  You can see why if I'm considering all this, I'm seriously considering as an alternative a custom-fab'ed long-runner intake that would fit with the turbo in the stock location (which as you may know on transverse-engine mount application, is up high and very tight against the head, leaving very little room for the intake runners.)

Handling this turbocharger, I'm sort of amazed how heavy it is.  I've got to weight this thing... there could be a positive side effect to doing this which would be just getting the turbo mounted a few inches lower (lowered the center of gravity.)

By the way, the A2 gasser intake manifold has runners that are just about the same length as the naturally aspirated diesel intake manifold!  If I were to successfully relocate the turbo with the exhaust manifold flipped upside down, it might not be that hard to get the A1 gasser intake manifold to fit (which has comparably shorter runners vs the A2) and do a comparison.

[Dr. Diesel]

Jake, I don't know if you've had a close-up view of audi 5000 (turbo, i think) intake manifolds, but they've longer runners than the A2. You'd need to cut a runner off to convert 5 to 4 banger though. I believe they have a circular inlet hole as well, which would be easier to work with.

[web]

Looking good, but long runners on gassers are usually mostly for low end / midrange. For best top end power one needs relatively short fat runners, although not as short as the TD ones, if you can call them runners at all! If the ports match up nicely, this one you have pictured now looks VERY good but I wouldn't expect any gains from going even larger.

Also make sure you heat shield the manifold and the turbo properly ; such a large intake manifold may otherwise get cooked and heat the charge air!

[Dr. Diesel]

i'm guessing the whole point is to improve off-boost performance, in which case, somewhat longer should be better. If the wastegate measures boost from the intake manifold, rather than from the compressor scroll, it'll compensate for any flow restrictions at higher rpm. (not that I'd suspect many diesels of revving high enough to make a long runner intake become a restriction)

[VWRacer]

Jake, I bet an intake off an A1 GTI would work even better in a racing application. Stan

[vwmike]

A good ported A1 intake would be hard pressed to outflow a stock A2 intake manifold....so I'd vote for the A2 manifold.

[caddy]

do you think about a 2.4d intake manifold? from a 5 cyl......

[fspGTD]

Either way guys (A1 gasser, A2 Gasser, Hacked-off-runner Audi5kTD, or Digifant/G60 which has same runner length as A1 gasser but larger runner diameters)... these manifolds are pretty cheap at the wrecking yard and once the turbo is out of the way, could be swapped pretty easily (IE: intake manifold bolts are accessible without removing the turbo.)  The hardest thing about swapping from one gasser-style intake manifold to another would be hooking up the boost tube if it were on the opposite end.

The most difficult part of this job would be would be getting set up by relocating the turbo lower to create clearance above for a multitude of manifold options.

To relocate the turbo lower here is a list of things I've already found that it would require (and surely there are things that would "spring up" I haven't yet discovered):
* clock turbo bearing section so oil feed is at top, drain at bottom (and hope that the old rusty bolts don't break!)
* fabricate, bend, or re-do oil supply and oil return lines.
* clock compressor outlet so that the outlet is pointing more towards back leaving adequate clearance for boost tube connection (also change lengths of wastegate supply hoses as needed.)
* re-do shift linkage so it doesn't interfere with compressor housing
* grind "ribs" off the top of the exhaust manifold so intake manifold fasteners are accessible.
* trim flanges of exhaust manifold with grinder to make room for the intake manifold flanges
* heat-shield between exhaust manifold and intake manifold (maybe use header-wrap, or custom-fab a sheetmetal one)
* adapt or fab new boost line for compressor outlet to intercooler inlet
* fab new 2.5" custom-shaped downpipe w/flex section from new turbine outlet location to existing exhaust system
* completely re-do the air intake system as it would need to be moved from the passenger's side to driver's.  Find a spot for the air filter and secure it (fab brackets as required.)  Add new hose or tubing between air filter and compressor inlet and from cold air location to air filter inlet.  May need to relocate wires, heater hoses, etc to make room for the new location of the air inlet tract.

As you can see, there is no walk in the park here!

PS - my goal is to gain a power boost in my usable power range and/or broader the usable power range.  I've read a lot about intake manifold design and studies up on it, but found that it's hard to very accurately predict what's going to happen and so at one point you've got to just try it on an actual engine and see!  That said, my current power band starts at about the point where the turbo kicks in (which really starts at about 3500RPM when the turbo is in full sing, although I can lug it down to 3000RPM if I really need to) and it ranges up until the governor starts limiting fuel (5500+ RPM.)

[fspGTD]

A good ported A1 intake would be hard pressed to outflow a stock A2 intake manifold....so I'd vote for the A2 manifold.

I don't think that's true, unless you are considering a digifant/G60 manifold.  The digifant/G60 manifold has larger diameter ports than the standard A1 manifold (but from the outside, it looks pretty much the same AFAIK, IE: has same runner lengths.)  The A2 gasser manifold that I've got and have shown in the pics above actually has runner diameters probably about the same diameter as the A1.  I would probably port-match whatever manifold I end up using and might be able to get back into the runners several inches.

Looking at the RPM plots of the 1.8l GTI motors in my race class that are using the digifant/G60 manifolds, the power peak RPM seems a little bit high for ideal to me - at about 5250RPM.  I'm thinking the longer runners of the A2 manifold might be useful if it added hp to my power curve a little bit lower than 5250RPM.  I mean 5250 RPM is in my usable power band, but I'd love to get as much beef as possible under 5000RPM.

[caddy]

what do you think about this?

[fspGTD]

Those are some looong runners on that 5-cyl manifold there.  Got a runner length measurement?

[fspGTD]

I've been around... I suppose mostly lurking.  

[caddy]

Those are some looong runners on that 5-cyl manifold there.  Got a runner length measurement?

no but i can check it.

[fatmobile]

Hey Jake,
 I don't think you mentioned a support for the turbo downpipe.
 Would you need an added support to take stress off the turbo/exhaust flange?
 Maybe something like the NA diesel, dual downpipe support would work.
 I was looking at an A2 NA diesel intake and the runners look like they could be longer than the gasser runners.

[fspGTD]

Are the A2 NA diesel runners the same length as the A1s?  I would assume VW left this design feature the same given the identical hp and torque specs of the A1 NA Diesel and A2 NA Diesel engines, however I have not confirmed this before by actually measuring and compating the runner lengths.  I know they went to a plastic plenum / aluminum runner design on the A2 NA diesel manifold, while the A1 NA manifold is all one piece in aluminum up to the air filter.

I probably won't be taking on the turbo relocation project, at least not before next race season (which is, when the weather gets better and when I have more time.)  I may reconsider a custom intake manifold fabrication project however instead.  My brother may be on a track to becoming a professional welder (He is in army reserves training over the next 2.5 months, learning how to weld anyhow.)  If he were to invest in a TIG setup after completing his training, he might be able to help me tackle such a custom fabrication project (tubular aluminum intake manifold) with ease.  Although it would be sweet to get the turbo out of the way, it's just so much work, and the exhaust system has got to be pretty cloe to optimized already with the turbo in the stock location.