Turbo type-4 vs. Subaru swap

[Andy Somogyi]

Got a 76 Porsche 912, and I keep mulling over Subaru swap vs. type-4 turbo.

I'm 95% sure I'll be going with a Subaru, but there's one nightmare with that swap: the damned cooling system. So little room on the front of a 912 to make a stealth radiator install that's NOT in the trunk. Absolutely no way I'm sticking a radiator in the trunk, it'll be a 3 radiator setup with a chin and a pair of fender rads.

So, I go back to thinking about a type-4 turbo build because cooling is a pain.

A type-4 turbo build will cost at least double what a Subaru build will cost.

My concerns with a T4 turbo build is the fact that's in a fairly obscure engine that's getting harder and harder to find. And if anything goes wrong bottom end wise, it's going to be extremely expensive to fix.

In either case, I've got well equipped shop, milling machine, lathe, welders, benders, etc. so I can fabricate pretty much anything needed.

Worked out a spreadsheet here with price estimates. It's safe to say that a Porsche flat-6 build and swap is out of the question financially.

horsepower goals.jpg

[wreck]

I've got 173WHP with a NA 2.6 type4 that I've put 15000km on in the last 18 months , it runs cool and is reliable . I can even get 8.4lt/100km on the open road . If that is the ball park figure HP wise then just go for a well built NA type4 with matching components . A lot less complicated .
Something to put at the bottom of your spread sheet is how much you devalue the car by fitting the Subaru engine .
Something you can't put a price on is when you've just had a run from a set of lights against someone and they then find out it's just a NA VW engine . Even if they beat you they aren't going to go bragging to their friends they just whooped a NA VW engined Porsche . Where as if it's a Subaru or Porsche motor that gives them an excuse why the lost .
you are also comparing a reconditioned engine verses a 2nd hand Subaru engine . Maybe throw into the cost a possible head gasket replacement .

[cal 67]

With boost, why do you need an expensive bottom end? 71mm cranks and H-beam rods are common and inexpensive. Why so much headwork? You could get by with a lot less and still have gobs of power.

[H2OSB]

You're living on a whole different scale than me...for me it was EJ22 vs 2056cc T4. Also for me it's a '74 Super Beetle, but I simply cannot get past the idea of cutting up my car to install a radiator. There are clearly people who've got this worked out, but I can't do it(i.e. won't), so T4 it is for me

H2OSB

[twodollardoug]

I think they loose their soul when they are not aircooled.

[Andy Somogyi]

I think they loose their soul when they are not aircooled.

I suppose I could always LS swap it, it would sure have more soul then

Seriously, as the engine is right now, it’s about the most soulless gutless slug I’ve driven in 30 years. That smog chocked engine just absolutely kills what would be an epic car.

I’ve previously had a 71 911T, and that was such an absolute dream to drive, with how eager that flat-6 was to rev, and that sound it made when all six carb throats would open up. My 911T was about as diametrically opposite in terms of soul to this soulless gutless VW bus engine I’ve got in the car now.

But no, I’d never LS swap it, I just don’t like the sound or the feel of an LS, it’s just too heavy of an engine for the car IMO. I like small, high revving engines. The absolute best ‘feeling’ engines I’ve ever driven were a toss up between an Ferrari Dino, Lotus Europa, Lotus Esprit and early 911.


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[Andy Somogyi]

I've put together an updated price estimate for a type-4 turbo build. This included custom-building a flat Corvair style fan.

Let me know if you guys think these estimate for the T4 turbo are reasonable, this is based on a lot of used parts ebay prices.

horsepower_goals.jpg

[woodsbuggy1]

Andy, what not a Type 1 stroker? Also Type 4 motors can be had for cheap, I have scraped at least 5 of them in the last several years
Good Luck
Kenric

[Andy Somogyi]

Andy, what not a Type 1 stroker? Also Type 4 motors can be had for cheap, I have scraped at least 5 of them in the last several years
Good Luck
Kenric

I’m still on the fence. See, I track my cars, and whilst a T1 is great for drag racing, it doesn’t have the cooling surface area for extended runs at full power.

A T4 with A LOT of help, like dry sump oiling can dissipate heat for an extended duration.


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[Wally]

There's a lot of things I would do different on your engine combo for 'an easy turbo type 4' and price wise I think you use too many used parts for it for the reliability you seek.
You have an Original 912E motor in there now? If so, I'd use that as a base and keep it 2 liter with the original head opening, so with new 94mm pistons & cylinders and rebuild the heads properly.
It will cost a lot more then.
Sooo, if price is your main concern (which I gather from your opening post), don't rebuild the original 912E engine into a turbo'd one.

[Andy Somogyi]

There's a lot of things I would do different on your engine combo for 'an easy turbo type 4' and price wise I think you use too many used parts for it for the reliability you seek.
You have an Original 912E motor in there now? If so, I'd use that as a base and keep it 2 liter with the original head opening, so with new 94mm pistons & cylinders and rebuild the heads properly.
It will cost a lot more then.
Sooo, if price is your main concern (which I gather from your opening post), don't rebuild the original 912E engine into a turbo'd one.

I’d like to get about 175-200 hp to make the car enjoyable to drive.

To get a T4 to this level of tune reliably pretty much requires boost — for the same power levels, a turbo engine puts much less strain on the cooling system than an N/A engine.

The big cost items seems to be finding core, and the bottom end like fully counter weighted crank and biral cylinders. Then a different cooling system going to be expensive to make.

I’m a research engineer as my day job, I’ve got a nice shop at home with a mill, lathe, etc and at work we’ve got some huge machining equipment so I can handle all the design and fab myself.

But I don’t know, I keep going back and forth. Like it’s taken months to track down a buildable core, (that’s not $5000 like eBay sellers ask), and if I detonate that one, who knows how long it would take to find another. If I detonate a Subaru motor, who cares, I’m out $1000 for another low mile complete motor.

Just a pair of stock heads from AA cost what a complete Subaru motor costs. With a Subaru, you’ve got a 5 main bearing bottom end that’s proven reliable at upwards of 700 hp in rally form.

Basically the trade off is with a Subaru, I need to design and fab a cooling system. With a T4, I need to design and fab essentially a complete engine — bottom end, heads, turbo exhaust, intake, complete upright or flat fan, dry sump oiling, etc... I mean, I can do it, but it’s a huge amount of work.

I worked out the math, ran a bunch of thermo simulations in Solidworks, and there’s no way engine air cooling alone can sustain a 135 KW heat load, so need to go dry sump with a big front oil cooler. With an N/A engine, the heat load would be even higher, hence why turbo is much better for air cooled engines.

Without a dry sump, sure high hp air cooled VW engines are fine for the drag strip, but I track my cars a lot, so that’s continuous full load for extended periods. So cooling is super important.

Anyways, I’m still on the fence of T4 turbo vs Subaru. My concerns are reliably making about 200 hp, and what are the risks if I detonate a motor. And yeah, I’ve detonated my fair share of motors.


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[wreck]

Ghia 2018 Leon's .jpg

ac serpintine ..jpg

That is wheel HP on a happy dyno . NA type 4 true daily driver in tropical temperatures ,15000km in the last 18 months. I believe the 48 Dells are limiting the power a little due to only being able to run a 42mm vent . 10.5 to 1 comp with a 265 @ .050 degree cam on pump fuel . Runs cool as a cucumber .
In your calculations are you factoring in that these engines are oil cooled as well as air cooler . More oil can be sprayed on the heads with autocraft style spray bars to help cool the heads and valve springs .

My shopping list for +175hp would be a set of AA 98mm P&C
78mm crank with chev or type 1 big ends. (easier rod selection) AA or DPR
AA rods with good bolts
New AA 2lt 914 head castings with 46mm in 38mm ex valves (slightly ported not hogged out)
best Web 86C cam or cheaper Scat C55(what I'm running )
1700 rockers with 8mm adjusters and genuine Porsche elephants foot adjusters .
DTM cooling shroud kit
Turbo Thomas or CSP exhaust or if you can weld and have patience buy the Pipemax program and a bunch of
bends and flanges and make your own .(what I did) .
Either 48mm carbs or EFI . I'd go EFI .

In your case a dry sump is the way to go with the ease of fitting a 911 oil tank . whether you need it for a road car is debatable . A good friend builds Formula Vee engines/chassis . In Australia the specs are a mostly standard 1600 TP with a wet sump and they get away with it with a proper windage tray .you are not going to be cornering faster than an open wheeler in a tin top.

Gabbi underneath . .jpg

[Andy Somogyi]

Ghia 2018 Leon's .jpgac serpintine ..jpg

That is wheel HP on a happy dyno . NA type 4 true daily driver in tropical temperatures ,15000km in the last 18 months. I believe the 48 Dells are limiting the power a little due to only being able to run a 42mm vent . 10.5 to 1 comp with a 265 @ .050 degree cam on pump fuel . Runs cool as a cucumber .
In your calculations are you factoring in that these engines are oil cooled as well as air cooler . More oil can be sprayed on the heads with autocraft style spray bars to help cool the heads and valve springs .

That's some pretty impressive power numbers. Yup, I've totally factored in that they're partially oil cooled, oil cooling is absolutely critical for larger power levels. With the 911s, and certainly with the 2.7 and bigger, they're about as much if not more oil cooled as air-cooled.

If I were to go T4, I'd build a flat Corvair style fan, like what Wally built. IMO, the flat style fan is the best (in terms of volume, and uniform air flow) you can run on these. Plus, I think they look awesome. I've got a OK machine and fab shop at home (lathe, mill, welder, etc...), so anything that needs fabricating, I can do it.

So with your N/A engine, running at 10:1, no issues? Damn, you've got me seriously considering the T4 again...

905ac063-4193-4ba6-a584-734189825e7c_zpsbgdpekev.jpg

[wreck]

More like 10.5 to 1 . You have to match the compression to the cam .The only reason I don't increase it is because you can only flycut type 4 heads so far before you find the exhaust manifold studs poking though the combustion chamber . Also something I didn't mention was the pulley ratio I'm getting away with , it is less that a power pulley !

The heads on your engine may be fine to rebuild , you just need to check for cracks .

Have a look at some of the 1990's German Kafer Cup cars , or 914 racing in the States . the top cars would be pulling over 200hp out of type 4's in circuit racing tune not drag racing .

The horizontal shrouds are very nice .

[Andy Somogyi]

I've been working on other projects, haven't looked at this project in a while, and going to try to get back to this sometime soon.

I'm still on the fence WRT T4 vs. Subaru. I'm thinking price wise, if done with some resourcefulness are comparable. The issues that I keep coming back to with each approach are:

* What's the long term viability of a T4? Where can you buy a T4 builder at a sane price? Looked on ebay, and they're asking like $3000 for a builder, is that really what a builder T4 costs? What if a year or two down the road, it throws rod, are you at the mercy of these $3000 core motor ebay sellers?

* Running water lines, and setting up front radiators is an absolute nightmare on the 912 if you want to do it right.

If I were to go T4, by config would be :

* custom upright or horizontal fan shroud
* coil pack, knock sensor ignition, Speeduino based ECU, electronic controlled thermostat flaps in shroud.
* 96mm Biral cylinders, 78mm forged crank, rods from AA.
* real harmonic balancer.