VW conversion economics

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Vigilant1

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I know that this is off-topic, but would you be able to share a list of the books and DVD's about aircraft VW engines that you mentioned?
This thread has many useful references (recommended books, DVDs, blog, etc):
Steps to scratch build a VW

Posts 4, 11, 22, 28,, 37, and 40 seem most responsive to your request.

There's a lot of info out there. Some of the info on VWs for performance cars/racers is interesting, but aircraft use requires high reliability and good output at moderate RPMs (3400-3600 and below). That's different enough from street racing that it's a good idea to pay closest attention to sources (including people) that are focused on flying Type 1 VWs.
 

curious

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Definitely seems to have increased oil flow to the top end, which would carry some heat away, and help lubrication
"seems ... help lubrication"

let me quote from the blog: "Auditing the engine’s lubrication system we found that all of the oil for both heads came through a single 5mm drilling. In theory, a hole that size should have provided more than enough oil. And it did, but only for the left-hand head."

what does that mean? so we need another 5mm drilling to the right case half and hence the case drillings?
in a late model case that 5mm drilling is 6mm and the drillings to and from the oil cooler are 8mm.
oil flow pressure loss is related to the velocity through the drilling (darcy-weisbach). so 2 - 6mm drillings is like having a single 8.5mm drilling. comparable flow velocities. my "audit" of the oil system shows that in "theory" hoover is trying to put more oil to the heads than is actually available.
 

Martti Mattila

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My aviation buddy died and I salvaged (payd a real money) some of his stuff. Two Limbach converted case where I havent studied yet if something is done for routing lubrication and unused typ 4 case and opened heads for 103mm. cylinders. But why Im here is the VW conversion that someone dit a while ago. It was really narrow VW done by using shortened stroke camshaft. That time when I was reading it I tauhgt theres nothing for me, but now I have played with "what if idea" that coes like this. A wery short stroke crank, 1200 has 64mm. that can be reduced with 51mm. conrod journals to 61 mm. With some large diameter cylinders where we might have to use some heavier case. For example one that is made from modified Wasseboxer case, that takes in a big cans.
Next and most expensive thing would be the heads, might need to go to a Scat sigle unit heads, expensive. Now we would have a engine thats displacement would still be close two liters with short stroke and low piston speed. Is there a any sense to make sutch engine for aircraft use. Long ago in SA. magazine there was a comparison with engines and performance and they totally ignored displacement, they only count a piston tops area. Type 4 is there almost already and maybe cheaper to make, but heavy.
 

curious

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Seriously? Why the hell not?
asked and answered as i got an email from casler a few days ago. in a nutshell: not applicable to low rpm/compression motors.
i thought that was an interesting response. i figured it was liability but i was wrong. however, he avoids liability by not doing it. :)
 
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curious

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economics is the thread topic. how about making better use of the fuel being consumed?
let air and auto engine manufacturers show the way. some topics for you think about.

do any of you do anything with your cams, cam timing, cam gears? what sort of cams seem to work well? have you looked into dual pattern or asymmetric cam profiles? cams for use with high ratio rockers? methods for indexing? i have found next to nothing on cams in this forum. it's not all that expensive to have a custom cam made with modern features.

anyone using roller lifters? flat lifters are obsolete tech. from an economics point of view, it must be worth chucking them. look at all the ac manufacturer's that have abandoned flat lifters: jabiru, lycoming, epi are ones that i know of. as far as i can tell, they all use inexpensive chevy rollers. i plan on going roller on my next big $ vw build.

anyone install thin low tension rings? enquired about this one at thesamba. guy says thick ones conform better. NO! thins don't just free up power through friction reduction but they conform better to out of round cylinder bores so emissions and blowby are reduced. i want this one too but it may be pie in the sky. i know thin rings can be retrofitted but have no idea if the manufacturer will do it for a reasonable fee for a vw piston.

piston squirters anyone? anyone here do the type 4 rod notch modification?

anyone install install modern copper alloy valve seats? i know there are a few engine builders using these seats as i have seen pics of heads with them installed at thesamba. they aren't that much more expensive.
 

Vigilant1

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I can't speak for everyone, but in my VW aircraft engine my primary goal is high reliability. I'm not interested in packing more air/charge in because I've already reached the thermal limits of the engine (based on ability to remove heat using available airflow and pressure), and due to known limits of the magnesium case bearing supports. I'm not much interested in reducing fuel burn beyond the very acceptable BSFC we normally get (approx 0.40 lb/hr/HP) if it increases the chance of ending up in a cornfield. At this point, fuel expenses are a tiny part of total costs of owning and flying my small plane. I would most like to use parts, assembly procedures, and maintenance techniques that are known to work in aero VWs.
 
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Pops

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I can't speak for everyone, but in my VW aircraft engine my primary goal is high reliability. I'm not interested in packing more air/charge in because I've already reached the thermal limits of the engine (based on ability to remove heat using available airflow and pressure), and due to known limits of the magnesium case bearing supports. I'm not much interested in reducing fuel burn beyond the very acceptable BSFC we normally get (approx 0.40 lb/hr/HP) if it increases the chance of ending up in a cornfield. At this point, fuel expenses are a tiny part of total costs of owning and flying my small plane). I would most like to use parts, assembly procedures, and maintenance techniques that are known to work in aero VWs.
Well said.
 

TFF

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The problem with any hot rod stuff is our engines are at idle compared to what the performance stuff is. For the average airplane builder, just getting an engine is a big accomplishment. Because there is the whole airplane that also has to be built, a little more efficiency is usually back burner. It’s not that everyone wouldn’t want a roller cam, they were first used on airplane engines you know. It’s that someone has to do all the leg work, and not to many will spec out two or three cams to test, if one is serious. While roller cams definitely take less horsepower to spin adding to efficiency, the real flat tappet issue is oil. Getting rid of zink in most oils is an epa solution and manufactures had to compensate. Airplane oil has a different additive instead of zink which is the ashless part.

Most of the issue is getting rid of the heat with the engines, not making more power. Things like low tension rings, would be great. With air cooled engines, running the light weight oil that they thrive on does not help, because the oil is a big part of the cooling. Oil squirters are used in in the higher horsepower airplane engines, still it’s the iterations needed to get to where it’s solid.

It’s not the speculation of all the ideas, it’s the doing
 

Martti Mattila

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I know that doing is the essence and not speculating but isint these forums just for that. And theres so many options trown to my way and I let my mind to wonder. It was so much easier when I was in my thirties with low budged and only one way to go, a basic VW.1600. Fuel price is les important and avoiding a cornfield is numero uno.
 

curious

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Most of the issue is getting rid of the heat with the engines, not making more power.

It’s not the speculation of all the ideas, it’s the doing
getting rid of heat? you need 50hp? make it with 45hp worth of fuel and realize lower operating temps through the use of modern technology. the bronze seats are better at draining heat from a valve and are less prone to galling since they aren't an iron alloy. only about $10 a seat more than the old stuff. modern asymmetric cam profiles are used to eliminate valve bounce. the type 4 rod notch mod makes use of spent oil coming through the rod bearings to cool the pistons. cheap and effective.
 

challenger_II

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Fuel price is les important and avoiding a cornfield is numero uno.

I do not have any cornfields... I gots mesquite thickets. I have a vested interest in my little Dub to keep happily humming along! :)

Regarding heat dissipation/avoidance I will toss this concept in the mix, and see if my tail feathers get singed:
For an application that is happy with the 1835cc, propped to turn 3100rpm, what if One were to build a 1915cc or a 2180cc, use the prop from the 1835 and turn the engine at 3100revs? Yes, the engine would be underloaded, as compared to the 1835. Would this not reduce the workload on the engine and reduce the heat generated at the heads?
 

Marc W

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If you are making the same HP you are burning the same amount of fuel and generating the same amount of heat. Cylinder pressures will be lower but the loads on the engine parts are the essentially the same.
 

Vigilant1

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I do not have any cornfields... I gots mesquite thickets. I have a vested interest in my little Dub to keep happily humming along! :)

Regarding heat dissipation/avoidance I will toss this concept in the mix, and see if my tail feathers get singed:
For an application that is happy with the 1835cc, propped to turn 3100rpm, what if One were to build a 1915cc or a 2180cc, use the prop from the 1835 and turn the engine at 3100revs? Yes, the engine would be underloaded, as compared to the 1835. Would this not reduce the workload on the engine and reduce the heat generated at the heads?
Well, if you turn the same 3100 RPM, your new larger engine will be capable of producing slightly more power (since more air and fuel will be moving through it) and you'll also have slightly higher CHTs (assuming everything else remains unchanged: compression ratio, etcl). BUT, since you say you'll use the same prop, and assuming nothing else changes (same airplane, same weight/induced drag, altitude,etc), then the only way that bigger engine will turn the same RPMs is with less than full throttle. In theory, the slightly bigger engine pulling air through a more fully closed throttle might have slightly higher pumping losses than the smaller engine.
If you bought a slightly longer prop for the bigger engine and turned it slightly slower to make the same thrust as the smaller one, you might reduce CHTs and also burn a little less fuel (all due to the slightly more efficient propeller).
Things would be different if the bigger engine also had a larger head with more fins, etc. Then it would stay cooler if it burned the same amount of fuel. But, it doesnt work like that, it's usually just the same fins regardless of bore size.

The bigger engine would give you more available power for takeoff, etc which might be handy.

Mark

ETA: Oops, cross posted with Marc W.
 
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Vigilant1

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It takes a certain HP to turn that particular prop at 3100 RPM. Whether we make that HP with an 1835cc engine or a 2180cc engine we'll burn approx the same amount of fuel and put the same amount of heat into the cylinder head. If it has the same "finnage", oil flow, etc we should expect the head to reach the same temp.

IOW, both engines are "laboring" just as hard. The bigger engine is laboring at a lower percentage of its max, but that's not relevant to the situation.
 

TFF

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You have to pick what you are testing. You can’t float all sides. Are you locking RPM, horsepower, temperature, manifold pressure, or displacement? You can’t let them all float for a comparison.
 

Pops

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My 1835 cc VW engine is cruising at about 33 HP @ 2650 rpm in the SSSC. Not so hard to cool. The first 32 hours I used a 1200 cc, 40 hp VW engine. Turned 3600 rpm in the WOT climb and cruised at 3200 rpm. Took it out because I didn't want to run it that hard for long life and wanted a better ROC in the short fields that I use.
 
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