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Maximum tilt for an inline 4 cylinder

Maximum tilt for an inline 4 cylinder

(OP)
I am contemplating an engine swap into a 1974 VW super beetle. I want to avoid using an adapter plate or combining an engine and trans that did not come married from the factory.

The idea that I am considering the most is to take a transverse 4 cylinder and it's FWD transmission and tilting it toward the rear of the beetle. The two I like the most are the Honda d series and the Saturn 1.9 twin cam. Both have aluminum blocks with similar weight, are inexpensive and make about 125hp stock NA.

In each case, I would have to tilt the engine somewhere from about 40 degrees to 60 degrees from vertical to get it to fit the way I want. I am certain I would need to modify the oil pan and oil pump pick up. But do you think oil would sufficiently drain down to the sump with a tilt of this angle? To be clear,I would be 30 to 50 degrees from horizontal.

Tilted engines that come to mind in stock form are the Vanagon 1.6 diesel, which I believe is tilted at about 50 degrees from horizontal. I believe it only has a special sump and oil pickup to distinguish it from an upright diesel found in a Rabbit. Also, upright 1.8 gas turbo motors have been mounted in these vehicles with apparently no lubrication problems.

Another example is the Toyota Previa minivan. I believe it operates at 15 degrees from horizontal.

I think there have also been Offy 4 cylinders lying almost flat running at Indy, but I think the constant left hand turns helped with oil scavenging. I don't know if they were dry sump, but if this is necessary it will probably be a deal breaker.

for the manual trans, which will operate at the same angle from what was intended, I think it will be OK if I relocate the vent. Porsche 911 G50 gearboxes are routinely inverted to make them suitable for mid engine application. What are your thoughts? Following is a sketch that sort of outlines my idea.

RE: Maximum tilt for an inline 4 cylinder

I suspect that by the time you fit a transverse 4 into a Super Beetle, you'll have no structure left to support it.

How about a Subaru engine/transaxle?

Mike Halloran
Pembroke Pines, FL, USA

RE: Maximum tilt for an inline 4 cylinder

For starters, I'd be looking at where the oil drain holes are in the head and block. I'd want them on the "low" side.

RE: Maximum tilt for an inline 4 cylinder

In a transverse front-drive application, the crankshaft is ahead of the axle centerline. If transferred as-is to the rear, it puts the engine where the back seat used to be.

Mid-engine sports cars that use a front-drive-derived powertrain transferred to the rear (Toyota MR2, Fiat X1/9, Pontiac Fiero if you want to call that a sports car) don't have a back seat because that's where the engine is.

The smart fortwo has a transverse mid/rear-mounted powertrain with the crankshaft ahead of the axle centerline but with the engine tilted back about 45 degrees so that the cylinder head is behind the axle centerline, and packaged very tightly to minimize intrusion on the passenger compartment. The ones before 2016 used an engine that was specific to that application. The new one (2016-on) uses an adapted Renault engine that was originally designed for front drive sitting vertically.

The rear-engine cars that I'm aware of that had a transverse engine with the crankshaft actually behind the axle centerline - NSU Prinz, and a number of Japanese minicars of the 1960s and 1970s - had a transmission that was designed for that orientation.

I believe you will end up with a tube-chassis creation that might perhaps only carry the outer skin of a Beetle on the outside of it by the time you are done. In that case, you make the chassis fit over the powertrain.

The Subaru powertrain at least is of the same general shape and layout as the original one, although when spun around with the engine at the back the output will be spinning the wrong direction. A quick Google search reveals that it has been done, though ...

RE: Maximum tilt for an inline 4 cylinder

(OP)
No I won't end up with a tube frame. Lots of measuring shows that I would only need to cut the package tray behind the seat. I won't have to cut the pan or change the rear suspension (with the possible exception of clearancing the trailing arms.

I agree that the oil drains are an issue. I hope they are on the side of the head on the low side of the tilt. If not, this probably won't work or I'll have to see if I can drill new drains, but probably not possible.

By the way, I am using Porsche 944 front and rear brakes and 944 rear aluminum trailing arms and 18" 911 wheels.

RE: Maximum tilt for an inline 4 cylinder

(OP)
Thanks for the examples of the MC and airplane engines. Other examples include Subaru flat engines and the very engine that is in the car at the moment, a flat 4. I think it returns it's oil to the sump from the heads via the pushrod tubes.

RE: Maximum tilt for an inline 4 cylinder

What are you going to do about the orientation of the transmission? Crankshaft in front of the axle centerline (putting the engine in the back seat area) or behind (which requires flipping the transmission upside down)?

RE: Maximum tilt for an inline 4 cylinder

(OP)
Were you able to see the diagram in my first post? Imagine a transverse FWD drivetrain, in it's stock vehicle, with the engine in front of the axle centerline. Now rotate the entire drivetrain, without reclocking the orientation of the engine/trans, toward the rear of the car about the fixed point of the axle. Rotate it somewhere between 40 and 60 degrees. Now put that in the back of a Beetle. The crank centerline will be about 20-50 degrees forward of directly above the axle centerline.

RE: Maximum tilt for an inline 4 cylinder

(OP)
But what about my question? What is the difference in oil flow for an engine that is upright vs. one that lays 30-45 degrees above horizontal?

RE: Maximum tilt for an inline 4 cylinder

I saw the diagram, but it didn't make any sense.

There are a number of considerations to make. The specifics of each one will vary from one engine to another, and you haven't told us what you want to use.

Oil has to drain back from the cylinder head to the oil pan by gravity.
The process of oil draining back to the oil pan must not interfere with crankcase ventilation.
Speaking of which, the crankcase ventilation connection has to be in an appropriate place that doesn't get submerged in liquid oil.
The oil pump pick-up inside the oil pan has to remain submerged in liquid oil and it must not suck air regardless of foreseeable acceleration or braking.
The cooling system has to be oriented such that any gas bubbles in the cooling system can escape uphill all the way to the radiator cap and vent/overflow connection. This means coolant has to come in at the bottom and come out at the (new) top, and the orientation of the cylinder head must not trap gas bubbles above this. Mid and rear engine vehicles with liquid cooling and front mounted radiators can have troublesome cooling systems because of this! The ordinary location of the radiator cap at the radiator (at the front of the car) doesn't properly let gas bubbles escape from the engine ... the coolant pipes between front and rear are invariably below the floor.

And ... the biggie in your situation ... the liquid oil level inside the transmission must not starve any of the internal bearings and gears of oil. If manual, there's no oil pump, it's all splash lubrication.

RE: Maximum tilt for an inline 4 cylinder

Other considerations.

Oil filter orientation. What happens to an air pocket inside it ... does it stay trapped, or get purged out? What happens to oil that is sitting in the filter when the oil filter is removed? Does it (A) stay in the filter (ideal), (B) make a mess on the floor, (C) land on the exhaust manifold (and potentially subsequently start a fire, or at a minimum make a big smoky stink)?

Center of gravity height. It appears that your layout would put the engine up high in the chassis. In a rear engine car with already dubious handling characteristics ... that's sub-optimal.

Thermal considerations. Where's the exhaust manifold? Would a foreseeable oil or fuel leak cause a problem? Is it on top of the engine where something could land on it, or is it protected in some way?

RE: Maximum tilt for an inline 4 cylinder

(OP)
Some great points and you've done a good job of naming many of the questions.

you haven't told us what you want to use.

This is from my first post: The two I like the most are the Honda d series and the Saturn 1.9 twin cam

Again I ask, what is different about a VW 1.6 diesel in the back of a vanagon laying at a 50 degree angle with only an oil pan change? I don't think they do anything different with the water pump.

Amother engine that is operated upright and horizontally is a Cummins diesel mounted midship in some school busses. I think it is the L10.

I have seen stock oil filters at every angle from upside down to right side up. I don't know if there are internal engine differences to accomodate them.

Brian, I get that you don't think I should do it. Thanks for your concern. I believe most of those issues you raise has been solved by VW and Cummins, with the obvious exception of the transverse transmission lubrication issue.

And by the way, I think gearbox lubrication and oil drainback from the head are the two biggest concerns. As for center of gravity, yes it is important. But these are both lightweight engines (210 lbs dry) and rotating them as I'm doing won't raise their CG much. I'd say 2 inches max. Will the CG be higher than a stock bug? For sure, but I am widening the track by 4 inches and running 265's in the rear, so I think I'll be able to offset much of that.


RE: Maximum tilt for an inline 4 cylinder

The VW inline four is inclined in most applications (every one I've seen, and I've owned a couple). The usual front-drive orientation has it (IIRC) 15 degrees leaning back. It's at the same angle in the longitudinal front-drive applications. So, it's already designed with the coolant coming out the front/top of the head, and the crankcase venting stuff is on the front of the engine (the "high" side), and the oil filter is on the front of the engine (the "high" side), and the exhaust manifold is on the back (the "low" side and on the other side of the engine from potential oil leaks or spillage at the oil filter). Tilting it over even more (and modifying the oil pan and oil pickup screen so that it works right, which is no big deal) doesn't really change any of this because it's designed to be a slightly-leaning-over engine anyhow.

I have absolutely NO idea whether the Honda and Saturn engines are appropriately designed for being leaned over!

RE: Maximum tilt for an inline 4 cylinder

(OP)
Cool.

Good news. It looks like both the Honda d and the Saturn 1.9 have most of their oil drain holes on the intake side of the head, which is the direction I want to lean the engine.

Looking at pictures of the innards of both transverse manual gearboxes, I would say the news is not as good. I think in order to lubricate the main gearset, the differential would have to be completely submersed in oil. I would assume there aren't too many differentials that run like that (although I'm not asserting that as fact). I would assume that differentials generally are submersed around half way in oil. I doubt that this would make them not work, but I think it would definitely produce a lot of fluid friction, resulting in heating the fluid and perhaps some increased oil frothing. Perhaps it would also produce internal pressure in the gearbox that would need a more advanced venting system (although I knew the stock vent would have to be relocated anyhow).

RE: Maximum tilt for an inline 4 cylinder


If you keep the engine and trans in (the donor's) factory configuration, and rotate the whole thing around the drive axles to get the desired tilt - will that raise the entire engine higher in the car?
That wouldn't be great for CG/handling.
It is also fair to add external drains from the head to the sump.
Being a transverse, you won't have a hypoid gearset. the gears and chains you have will probably be happy with a reasonable splash/spray.
It is certainly possible to provide a pump in the trans to spray oil as needed.
The project will certainly exercise your problem-solving abilities, and your fabrication skills.
I'd like to see what you end up with.
cheers
Jay

Jay Maechtlen
http://www.laserpubs.com/techcomm

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