Engine Sizing Question

[VWCOOL]

oops double post

[VWCOOL]

[VWCOOL]

[Danwvw]

The way I look at it is with more stroke more mussel is even stronger and it also does not need to work as hard, less throttle.
I think the thing that determines what size an engine to build for a bus should be just how do you want it to drive. Want a zippy racy thing then limit the stroke want a tractor do the 78mm stroke or even the 82mm stroke. 76mm stroke X 92 Bore would be very nice. I have not gotten there yet, I would like to build a 74mm stroke X 92 bore myself. I think it could easily develop 125 hp with 40mm X 35.5mm ported heads etc... Do the short rods too probably stick with the Web cam 163.
_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[otis_bartleh]

[Brian71]

[VWCOOL]

Using the spanner analogy explains things nicely... however, in the context of engine operation, it overlooks the fact the piston cannot step sideways to make best use of the extra leverage. The piston's push is always on the centre-line of the 'nut' being loosened (analogous to the crank) whereas you and I can step sideways to square-up the pull on the spanner.

Compared to a stroker, a bigger bore motor fills its cylinders faster, earlier: for instance a 94mm bore moving 15mm down its stroke will pull in more air than a 90.5mm bore moving 15mm down its stroke. This not only fills the cylinder faster in the first part of the stroke but accelerates the air column in the intake tract faster, too, so cylinder fill after mid-stroke (when the piston is decelerating toward BDC) is often greater, thanks to the momentum of the intake charge.

So, more air earlier in the stroke, and a nice little sneak-in of extra air later in the stroke. Win-win!

A longer stroke, smaller-bore engine also places greater peak airflow demand on the intake port at mid-stroke. Said simply, this is the time during the intake stroke where airflow is at its maximum and hence where the port is at its most restrictive to airflow: a bigger-bore engine has less peak airflow demand. The cylinders 'see' less of a restriction imposed on it by the head/ports. Win!

Bcauuse it's been sucking-in more air already, and will continue to do so towards BDC, it offers a higher average air flow through its port. Win!

A bigger bore also provides less shrouding of the intake valve... something that Chrysler used to its tremendous advantage with the Hemi. With the wall of the cylinder further from the valve, more air can sneak in past the valve adjacent to the bore. Another win!

These are some immutable, simple, fundamentals of engine operation. They also provide some clues as to why some strokers run out of breath earlier in the rev range than a bigger-bore, shorter-stroke engine and may develop less actual peak torque for the same capacity.... cylinder fill and therefore peak cylinder pressure is less.

However, they deliver their torque earlier in the rev range which, seat-of-pants, on the street, feels like it's torquier.

Engine design... it's as easy as riding a bike!

[Brian71]

[ManFromNapa]

Thanks to everyone who has posted in here. I'm trying not to duplicate information/conversation/agruements that are in other posts... but it's hard. There are lots of them!

Let me shift the conversation slightly if I can. (It's my post )

Help me understand how to get the best fuel efficiency our of a big bore / big stroke combo. I've know a lot of guys with big engines, and they have spent a lot of $$ trying to achieve good MPG with no luck. I keep hearing promises of 20+ mpg, but don't know anyone who has achieved it. Regardless if I decide to buy the parts and build the engine myself, or if I choose to have someone else build it I need to make sure I'm making good choices. Any builder or parts dealer is going to have their opinion and try to effect my buying decision. I want to be prepared.

So let's assume that I've decided to go BIG, and let's pretend that money is no issue! 94mm bore and 82mm stroke to put into my 71 Bus. I've now got a 2275. What now? (Comments or links to threads that have the info I'm looking for is appreciated.)

To help with cooling I plan to full flow the case and install an external oil filter. Are there any other "extras" that I can install for extra cooling?

I also plan on using a SVDA, and biggest alternator I can find. (Not that the Alternator will help MPG, but this is a camper, I have a 2nd battery, and a lot of other "extras" do more amps is desirable.)

Heads? Ported? How Big?

Cam size?

Carbs? Size? Jets?

Exhaust? I plan on using heater boxes.

What else am I missing?
_________________
North Bay Air Cooled - VW Club in Napa, CA
http://www.northbayaircooled.com/

Check out my band, Thru The Haze
http://www.thruthehazeband.com/

[vwracerdave]

If MPG is a major concern in a big heavy Bay Window Bus then don't build larger then a 2110 engine. If you insist on a 2276 then forget about MPG.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[[email protected]]

74x92TW FTW
_________________
It's just advice, do whatever you want with it!

Please do NOT send me Private Messages through the Samba PM System (I will not see them). Send me an e-mail to john at aircooled dot net

"Like" our Facebook page at
http://www.facebook.com/vwpartsaircoolednet
and get a 5% off code for use on one order for VW Parts ON OUR PARTS STORE WEBSITE, vwparts.aircooled.net

[modok]

If you get a good combo then it'll naturally get fair to good mileage without trying anything special.

#1 mistake is probably running heads or carbs too big. You build an engine that runs great 4-6K rpm then cruise at 3k and it won't be happy and won't get good MPG. Shoot for 3500 RPM peak torque. That's about 1800CC with stock size heads and carbs, bigger heads carbs then UP the CC';s in proportion.

Always run enough compression for the cam and make it tight deck.

The common short tube merged headers will often operate the the harmonic at 3-3.3k rpm causing it to run well there but overscavenge and hurt your MPG. Then nearer to 4k rpm it's in a bad spot and runs hotter. Not ideal. A lot of this can be fixed with careful choice of muffler, another option is to just use a minimum overlap cam (web 218 110 LC?) and a neutral acting exhaust like the vintage speed superflow.

[Danwvw]

_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[jpaull]

ManFromNapa,


2234

84 Stroke with chevy journals. Costs the same as any other stroker, and with chevy journals the clearancing is not bad. With the torque of the 84mm, You can run your engine at lower RPM's and get better mpg's then any of the smaller motors.

92mm Thick Wall
Coolest running and Strongest, I don't know why anyone would choose 90.5 or any other when 92 thick-walls have the thickest cylinder wall of all of them at 4.6mm)

MOFOCO 050
First reason cause we should not promote a communist country by purchasing CB Chinese castings, 501 castings, or any others that hail from over-seas slave labor. We have a choice, so choose Made In USA.
Cause they will cool better then the rest and flow perfect for a 2234 with the cam below. Cut for 94's, so you can run your 92 thickwalls.

Run the single springs the MOFOCO 050's come with, CB lightweight lifters, Engle W120, and 12lb 4340 Flywheel. This will have a Very efficient rotating mass engine that has torque to keep your bus moving without shifting down for those mountains EVER. Run 40-44 IDF's dialed in properly With a MSD 6A box and you will get your 23+mpg. This combo will give you the potential to get even better mileage depending on your gearing in fourth and careful carb tuning.

Jeff


Almost took out a water pumper in 2nd gear:
http://www.youtube.com/watch?v=5G_TLCJoRkk

[GTV]

I'll give my two cents worth...
Does your engine now really need a rebuild? If the end play is good, it has good oil pressure and compression checks out ok, just bolt on a few goodies to increase your performance (for now). I would use dual 36 Dellorto's, a proper 1 3/8" header with quiet muffler (do not use that 4 tip junk), and some 1.4:1 rockers with single HD valve springs and HD aluminium pushrods. You will get an easy 30%+ increase in power, and as long as you don't have a heavy right foot, some nice mileage gains as well. When the time does come for a rebuild, you can swap those parts over to a larger engine.
If you want to use factory heater boxes, that will limit you to a sub 2 liter engine and stock size valves (not a bad thing). I recommend the 1915 (with the parts mentioned above) as well, it's cheap, easy to build and is very reliable if built and maintained correctly.
_________________
EMPI Power Rules!

[VWCOOL]

mate you need to decide if you want a Prius or a usable Kombi for camping

[VWCOOL]

[Danwvw]

What about the 2231 Grind for millage?
It has stock lift but looks like really soft ramps, seems to have huge over lap though! Is it just a different version of a stock cam? I was thinking of using it for a (74mmX88mm) Stroke/Bore millage engine in a bus.

_________________
1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[modok]

[Danwvw]