ShopTalk Forums | Aircooled VW Tech & Restoration Help

As the title says, I want to build a motor for my stock '68 type one that will get the absolute max MPG. Not worried about power or speed, other than the fact it must obviously be sensible in todays traffic (say 65-70mph), but not worried how long it takes to get there. I've heard of a motor built by Jon Karcey, the 'mileage motor', but not been able to find any details on it. I know the Hot VW's issue and page numbers, they're all early 80's (anyone got them to scan for me?).

Anyway, I know there are lots of variables to add together, but how about some basic starting points:

What cc engine? (Probably the most important question)
Carb or carbs, or even FI?
Standard heads, or work them up a bit?
Compression ratio
Standard cam, or a mild one?
Standard ignition and plugs?

Then there's all the other factors:
Gearbox, tyres, wheels, body mods(spoilers, etc).

I'm not worried about the engine looking stock, not scared to mod things or try something new. lets hear some ideas..........

small displacement, high cr (high efficiency), FIed engine would be where I would start. If you aren't game for FI, two small duals would be good too. I would build for lower rpms, since it seems that lower rpms, less air moving through the engine, thus less fuel consumption, so use a more mild cam, smaller valves, cleaned up heads to match the port.

take ideas from some of the high mpg engines out today. Although those engines do tend to spin at higher rpms, so perhaps my cam, valves and heads idea is bunk.

Just some thoughts.

if you aren't concerned about the engine looking stock, why don't you just put in one of the high efficiency engines of today? TDI would be pretty sweet, but your tranny would probably need to be regeared for it.

Would a 1300 do the trick?

A 1300 with sp heads, higher CR, mild cam, small valves and ports, and dual kads would probably be a mpg monster. And a torquey lil engine (but will certainly run out of steam early on)!

One "mileage motor" concept uses a small (77mm, from a 1300) bore and a mild stroke (76mm) for a displacement of 1416cc and higher-than-stock rotating weight (crank counterweights, 180mm flywheel, heavy crank pulley) to help it off the line and smooth it out a bit so you don't miss the displacement. If ultimate MPG is the only criteria and you don't care about fuel or construction costs, that's a pretty good formula. Running scary-high C.R. and adding water injection will squeeze out even more.
A pragmatic combination that can be built on a budget uses stock 1600 bore & stroke (thin-ring Jap pistons are a nice touch if you can find some) but the intake manifold and cylinder heads from a 1300SP. It feels bigger at low speeds due to crisper throttle response, but once you get to the suggested-shift-point marks on the speedo you may as well grab the next gear because it's almost done by then. My dad used to pull down over 40MPG overall on Regular with such a motor built to 7.5:1...at today's prices the cost-per-mile would probably be a little lower on Premium at 8.25:1 or so.
I've gotten some pretty impressive mileage out of stock D-Jetronic F.I. and have often mused about converting a Type I engine to use it (wouldn't take much, just never got around to it)

from what i understand(no experience with this) is the bigger stroker motors can get 30 to 35 mpg with a light right foot.

Please consider Bergmann Racing when you trade off options for your crankshafts. See www.bergmannracing.com for prices and sizes.
NO ADS, PLEASE - DOC
Keith

Good ideas guys. Sorry for the slow response, but I'm in the UK, so slightly out of synch with the USA.

Firstly, if I wanted a modern engine, I'd go with a modern car. I want to keep it VW and air cooled. Although the engine bay doesn't have to look stock.

I've got plenty of engines to choose from: 1200cc, 1300cc, 1600cc and a set of 1500cc piston and barrels. So I can make up pretty much any combo. I've also got lots of type three D-Jet bits, plus a type four D-Jet as well. Got standards carbs and a single webber 32/36 progressive (had good mileage from that before).

I like FI and its well known to be better than carbs. I could adapt the throttle body to the upright fan housing, but runners might be a problem. Anyone done a similar conversion?

I've got a CB cheater cam in my new type three engine, but not yet fired it up and run with it. This is supposidley a good cam for slightly more power, plus better breathing.

How about:
Cheater cam
long stroke 74/76mm crank
1300cc barrels & pistons
1300cc heads (have to be twin port for the FI runners)
Standard size valves with three angle job
Mild porting and polish to heads
Modified type three D-Jet system (perhaps smaller injectors)
Compression ratio? say 8 or 8.2:1?
Deck height at 0.04-0.05"?

Nice, but expensive options:
Knock sensor system from aircooled
CDI ignition
Air/fuel gauge

Other questions:
exhaust?
Gearbox ratios (currently got a 1500cc box with standard 165R15 tyres)

Anyone got any info on the Jon Karcey mileage motor?

I have a combo that gets 40MPG, very easily...

Is it a secret combo Jake? or can you give me a hint on stroke, barrels, cam, etc. Type four?

I was going to suggest a 3cyl Diesel, but if you want to stay VW then that's out.

I have to ask- are you just out to build a stock-ish motor that gets pretty good gas mileage, or are you REALLY trying for some SERIOUS mpg?





If you absolutely want tons of mileage, you could do what my father was going to try on the daily driver baja- Take the engine, convert it to a two-cylinder (as the aircraft guys do- except you probably wouldn't have to shorten the case, just leave off two pistons/cylinders/rods). Use a full-weight flywheel and a berg heavy pulley to smoothen things out. An early fan & housing can be used, modified for the missing cylinders of course. (this will save a few HP over the large doghouse fan). Power pulley would be OK.

Then, get a close ratio trans to make up for the lack of torque. If you find that the engine just "doesn't quite cut it", then add a small electric motor for some low-end grunt. (electric motors make their peak torque at STALL remember... zero rpm). A VW generator can be wired to "motor" for a few HP worth, but you may need a bit more than that.


Get some lightweight aluminum wheels, and some of the special tires with low rolling resistance. There's a couple to choose from now, since the hybrid cars are mass-market.



No, it won't win any drag races, and no, you won't be pulling trailers. But if economy is what you're after....

- David

I have a Type I version, its a 1600...

I have two Type IV versions, one is a 1700 and the other is a 2.0

Its all in cam/CR/and the combo in general.

I wasn't out to break any records, just wanted a fairly stockish engine (and car) to get really good gas mileage. I haven't drove my bug for a few years now since its been laid up awaiting a resto (after I finish my type three resto!). I think last time I drove my stock 1600cc with a progressive webber 32/36 (it came with a second hand engine before you say anything!) it got about 28-30mpg on average. I did one trip up to Scotland once, where I spent a lot of time creaping around narrow country lanes about 45-50mph; it did over 50mpg then!, I could never repeat it though during 'normal' driving.

I've been driving a naff Renault Clio diesel as my daily for a couple of years (not sure if you have them in the states - small compact car) and gotten used to 50mpg+. Just wanted my bug to get something like 30-40mpg without having to drive like a snail.

So really working around a stock type one engine (or perhaps type four), with minor mods to suit (cam, crank, stroke, compression, heads, ports, dizzi, FI, etc, etc)

Jake, stop teasing me with figures and give me some hints please . Any chance of a PM with some tips on? I'm an honest fellow and won't divulge your trade secrets to anyone else.

a renault clio? diesel?? what is that??

no we get all the BIG CRAPPY CARS here.