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  View original topic: Type 3 heater/exhaust differences?
nf6x Sun Jun 25, 2006 1:25 am

I hope this isn't a FAQ, but I searched and could not find the answer.

Exactly how are the heater and exhaust system parts on the Type 3 different from those on the other ACVWs?

I ask because I've noticed that the places I've found that sell new heater boxes and so forth don't seem to carry anything for the Type 3, and I've seen a few references here saying that the heaters and exhaust are different. I'm wondering whether it would be possible/practical etc. to adapt Type 1 heater boxes and other exhaust parts, in particular if I decided to build up a new semi-custom engine with higher performance (i.e., I assume that the stock exhaust wouldn't bolt right on with a stroker setup), but still wanted to retain the heater function. It doesn't really get so cold here that I need cabin heat for comfort, but I do like to have working defoggers.

My 1969 Fastback is my first VW, so I'm not familiar with what the exhaust and heater boxes are like on the Type 1.

My exhaust has a leak or two at joints and is pretty rusty, but I'm going to try to fix the leaks with new gaskets, sandblast the rust off, try to fix any pinholes that I might find afterwards, and paint the stuff with high-temp paint to prevent future rust. I figure I'll use a light-colored paint so that I can see the carbon buildup around any future leaks. Hopefully, I will be able to re-use all of my metal parts. I do need to locate (or fabricate) the rubber couplings that go on one end of each of the "U" pipes with the smaller third leg. I have the engine out for a rebuild, and the exhaust and heater boxes are piled up next to my blast cabinet waiting until I get around to working on them.

KTPhil Sun Jun 25, 2006 10:00 am

The overall layout is similar but the parts are very different. The T3 fan housing location at the back of the block means the exhaust system must be located further rearward. There are removable (maybe) REAR heater boxes between the heads and muffler itself. There is the different heater air routing, as you posted.

nf6x Sun Jun 25, 2006 2:43 pm

I don't suppose that any of y'all know of a picture of Type 1 and Type 3 heater boxes side-by-side out there?

nf6x Sun Jun 25, 2006 2:47 pm

[Regarding a PM offering me some take-off (?) replacement heater boxes:]

I don't think I need replacements right now; so far I haven't seen any signs that my old ones won't be usable after I clean them up. I'd like to learn how they're different from type 1 style boxes, though, because I'm considering that if build a new higher-displacement engine with aftermarket closed-loop EFI and distributorless ignition for my car in the future, I'd like to use all-new components, build/test/tune it as much as possible off the car (so I don't have to take my car off the road for the months of building and fiddling!), then swap out the complete unit. I could then either keep my old stock engine as a spare, or sell it as a running complete drop-in unit to somebody else who's fixing up their stock Type 3. For now, I'm rebuilding my engine in stock configuration for use as a daily-driver.

Not only have I not found a source for new Type 3 heater boxes and exhaust parts, but I also figure that I'd need to do some customizing anyway to fit parts to a wider-than-stock engine. I'm also wondering if there would be any way I could adapt any of the "performance" heater boxes and exhaust components out there. I think I wouldn't want to run J-tubes, both because of the engine cooling issues and because I don't want to lose the windshield defogger.

While I'm on the subject, what I'm thinking of for the (distant?) future is an engine with a modest performance improvement without greatly compromising the longevity or reliability.

I'd definitely want EFI instead of carbs, but I'd prefer a closed-loop system with distributorless ignition. It could either be an off-the-shelf aftermarket system, or I also have some crazy ideas about rolling my own and putting the throttle plate(s) under computer control, thus eliminating the mechanical gas pedal to throttle linkage, allowing closed-loop idle speed control, and getting rid of extra stuff like the air bypass valve that would no longer be necessary if the computer could directly control the throttle.

I figure that a 90.5 P&C set seems like a good option for more displacement without sacrificing reliability based on what I've read here, along with moderate stroking (maybe 78 mm?). I'd stay away from things like a turbo because I get the impression that the (large) performance gains come at the price of much shorter engine life. I also figure I'd stay away from a high-revving engine for the same reason.

I don't see how better intake and exhaust breathing would hurt reliability, but I'd probably still stay away from J-tubes because I've read that they increase engine temperature, and I also want to keep my windshield defogger.

The folks who seem to know what they're talking about here say that the cam is about the last thing I should choose after I've figured out what everything else will look like; one way or another, I figure the cam would be fairly mild.

My goal for designing/mapping the engine control would be for fuel economy towards the lower end of the accelerator pedal, performance towards the upper end, a fairly gradual transition between those regions, and the transition region located to keep regular freeway cruising within the "economy" range. I don't know if that's really possible yet, but it would be my ideal goal. I'm wondering if having closed-loop throttle control at idle would let me drop the idle speed in order to burn less fuel at stop lights.

Since my engine is missing its thermostat, air flaps and linkages anyway, maybe I'd fabricate a new set of flaps, and then let the computer control them with a servo motor or solenoid. It's not cold enough here in Riverside to need the flaps to get the engine running in cold weather, but I think they should still be there to get up to operating temperature reasonably quickly... I don't see why I should second-guess the VW engineers too much without a heckuva lot of careful study!

I'm an electrical engineer, so the thought of designing and building my own engine control computer doesn't scare me, but I'm a complete newbie when it comes to engine building! How good/bad/stupid/etc. does my idea for an engine design sound? 8-[

KTPhil Sun Jun 25, 2006 3:07 pm

Actually, the stock EFI works well even with larger displacements. Just don't go to a wild cam. The MPS can be separately adjusted for low speed, high speed, full throttle mixtures with the right equipment or a good spark plug interpreter (a spark plug whisperer?).

nf6x Sun Jun 25, 2006 3:22 pm

I got the impression here that the stock EFI can deal with up to about 1776 cc pretty well with appropriate adjustments, but I was thinking of going for around 2 liters (90.5x78). I don't have anything against the stock EFI... I plan to keep it on my stock engine for the forseeable future, and I have no desire to go with carbs. Still, I'd like to replace it with a closed-loop system (that is, with an O2 sensor to measure the mixture) someday, whether it's an off-the-shelf unit or something that I design myself. I think that the D-Jetronic (when properly working and adjusted) should be able to run rings around a carb any day, but a modern closed-loop system with a computer in it can do fancier stuff that just wasn't an option back in the 1960's.

My stock EFI doesn't seem to be running as well as it should right now, but it does make the engine spin and I haven't seen any signs so far that suggest that anything is majorly screwed up. I expect to tweek it into top shape and continue using it until I have a lot more time and money to spend on an improved EFI/ignition system (which probably wouldn't end up on my stock engine anyway unless a particularly expensive or rare part of my stock EFI died).



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