"square" motors? good idea? 88X88 90X90.5? advantages?

[danimal]

>>>Try a 1915, with the stage 7 heads, and a 110 engle cam, 1.25 rockers. 1-3/4 headers, dual 45 DRLA with 38mm vents<<<

hmmm... seems kinda high to me:
[email protected] rpm
torque [email protected] rpm
bmep was [email protected] rpms(!), @ 8.5:1 c.r.
this motor might be detonating on the streets of so cal

why? because the cylinder pressure of a factory dual-port type 1 engine(7.3:1) is only about 123 psi... and yeah, i changed the cam timing on your 1915 by 10 degrees in both directions, and the bmep only differed by around 10 psi or so... when i put the c.r. at 7.3:1, the bmep was 178 psi, because the v.e. is still 85%.

you might be able to get away with it easier in north georgia, because of all the moisture in the air, and the better gasoline.

i put the carb @250 cfm per barrel, because i don't know what the flow is, and i did not factor in the ratio rockers, because i can't find an easy way to do it with this program... even w/225 cfm per barrel, there was only a 5 h.p. loss at the peak.

if i were you, i'd do a search on the clf for all the 1914 dyno stuff that has been run.


dan
oceanstreetvideo.com

[JohnConnolly]

too much head and not enough cam. Try the 121/125 or an 86b, and 9.5:1 and the thing will haul arse.
1915s are excellent if you do em' right.

John
Aircooled.Net Inc.

[JohnConnolly]

Obviously if the LS (long stroke) engine is at 4K, the air moving thru is is the same as a SS (short stroke) engine at 4K.

furthermore, calculate the swept displacement of 15 crank degrees.

You'll find that for any crank angle, the long stroke engine will move a longer distance, but since the bore is smaller it's exactly equal. We aren't talking about piston speed, we are talking about how much air is passing thru the engine.
.30(78X94X94X.0031416) (30% of the short stroke) = .30(84X90.5X90.5X.0031416) (30% of the long stroke engine).

so, flow thru the ports is the same on both engines, at all crank degrees (IF the rod ratio is =).

[JohnConnolly]

Cale,

yes I'm in Salt Lake (did my honeymoon in Moab), it's 3 1/2 hours from here, and Snowbird is 13 miles from my house.

[James2]

Thanks Dan. I'm looking for an adapter for a type 4 to John Deere tranny right now.

[Spyke]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ray greenwood:
SNIP...But remembering that velocity equals distance times speed (in an unpressurised world) this has the added factor of a fast moving piston behind it. <HR></BLOCKQUOTE>

For these purposes velocity is assumed to be volumetric flow (i.e. cubic feet per minute) divided by the area of the port. Distance times speed works out to something like... feet squared per minute?

In a classic sense, Velocity is speed and direction, but that's not really applicable here either...

I'd have to see the article you're talking about cuz I'm not understanding what you're saying. (In other words, I'll shut up now!)

-Craig
www.teamyikes.com

[jmillheiser]

oversquare and undersquare engines are two very different animals. the may have the same displacement but the drive different.

undersquare engines(ala aircooled VW, 5.0L ford v8, engines that have a bigger bore than stroke) tend to be fast reving and of course can take big valves easily. undersquare engines also work better with turbos than oversquare engines since they can spool up a turbo faster due to their fast reving nature.

oversquare engines (watercooled VW, audi, honda, engines with a smaller bore than stroke) tend to rev slowly(ever rev a honda motor they rev so slow its silly) but they make up for it with good torque at the bottom end(oversquare engines run fairly wild cams to provide top end power that would not otherwise exist - that tourque is why most of your inline 6 truck engines are oversquare).

one big advantage to oversquare engines is that the blocks can be thicker and they run cooler which is why oversquare engines tend to be very reliable and long running.

the engine configuration(boxer, inline, vee) tend to influence if they are under or oversquare. inline engines tend to be oversquare. boxer engines tend to be very undersquare, and vee type engines(v6, v8, etc) can go either way but tend to be pretty close to square(small block v8s tend to be undersquare and big block v8s tend to be oversquare)

[Spyke]

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by jmillheiser:
SNIP... undersquare engines(ala aircooled VW, 5.0L ford v8, engines that have a bigger bore than stroke) <HR></BLOCKQUOTE>

I understood Oversquare to mean the bore is larger than the stroke. That's the way I've always heard it stated, and the following site of engine terms seems to agree with me... http://www.connect.ab.ca/~barachj/car-d ... uareEngine
I didn't use just this site as a reference, search on "oversquare engine" and I think you'll find a number of sites that agree with this.

I usually see the specs stated as bore/stroke, so it would make sense that for it to be oversquare, the bore would be greater than the stroke, i.e. the ratio would be greater than 1.

-Craig
www.teamyikes.com

[ray greenwood]

Craig I have read the same understanding of oversquare and undersquare...I think!. The simplest explanation I can make of long to short stroke/gas velocity issue...more distance to the valve for gasses to exit...valve is probably already closing ...depending on duration...piston is moving upward...if the gas can't exit fast enough (valve not large enough ..or not enough valves for exhaust...depending on your concept) then the piston will COMPRESS the exhaust gas out the port. While good for maintaining flow speed in the exhaust manifold...it is still resistance on the piston. It also causes heat. The answer ? a larger valve?...maybe. The bigger the diameter the head...the larger the obstruction to the port that exhaust gas will have to move around in the limited time it has before top of stroke...and closing of valve. Thats why when valves get too big...they reduce cylinder scavenging effect (because of the time required to skirt the valve head..) and they reduce the exhaust gas velocity because there be may no compression of the exhaust gas at all. The same effect can happen by using exhaust manifolds, pipes, catalysts and mufflers that are too small or too large. In the article I read on (undersquare?) audi engines...they found using the multiple smaller valves kept their port/exhaust gas velocity up...without restricting or over-scavenging the exhaust. I know I"m repeating much...but actually...this is not just from that article in European car....This is very old technology. The first four valve engine I ever saw was from a 1956 Jaguar engine...done for the same reasons...but not tuned to the same degree as multiple valves today. The most important performance decisions you can make are concerning the valve size and cam lift and duration. The stroke and bore mean nothing if they can't be fed or exhausted. The final gist was that Audi and Vw..at least believe in the long stroke undersquare? engine but only with highly tuned or variable valve technology to keep it properly fed and exhausted. Ray

[jmillheiser]

i think some of the earlier messages on this thread got this backwards trend started*L*

[MASSIVE TYPE IV]

I have built some unlimited class off roiad engines with 88x88 sizes, great torque, but limited powerband...Worked gteat to 6,000...

[46stang]

one more oppinion the smaller bore motors really limit valve size which will limit your overall power output. the motors that do have small bores tend to have mutivalves per. cyl.(4 valves)to make any kind of hp. vw's only have 2 valves per. cyl. so you may limit your hp. potential jmho.

------------------
2010cc, 78mm cb forged crank, 90.5 pistons, rimco rods, 44idf webers w/berg link., performance technoligies v5 heads w/chevy springs, berg sump,berg oil pump&filter system,engle FK-10 cam,scat lightened lifters,berg 1.45 rockers, berg pushrods, berg power pulley, berg 1 5/8 header w/flowmaster muff.,rancho built trans.

[JohnConnolly]

Ray, it occurred to me what you meant. The problem is comparing engines (LS and SS) at equal piston speeds isn't correct, since the two engines would have to be at different RPMs to do this (SS engines have a lower piston speed)!

So, to clarify, the SS and LS engines sweep the same displacement thru any # of crank degrees, which means the same displacement/time. This means speed thru the port is the same too, right?

The difference is that SS engines (of the same displacement) have a larger bore, and more room for valve unshrouding and larger valves.

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by ray greenwood:
Steve..it sounds almost like you read that exact article...I would swear that was the header on the add. Audi/VW water cooled equipment has almost always been long stroke small bore. They were doing research over the last decade to see if they wanted to move away from that configuration...as they were designing so many new blocks anyway...now would be the time. The gist of the article wasn't wether square or non-square was better....the gist was that the five valves were not necessary on their engines if they had been more square in displacement configuration. i.e...their testing on the same engines...2.0's, 1.8's and Vr6's...showed much better flow and horsepower on the long stroke motor with five valves compared to two three or four valves. Same volume, same exhaust port total area...less time to actually fill and exhaust the cylinders through five smaller valves than two large valves. John...you are correct that a 2.2 is a 2.2 and has the same volume wither the cylinder is wide or long. But...if the pistons in the two engines are moving the same speed....remember that the exit is at the end of the cylinder...there is going to be more time involved to empty the long cylinder than the short. Since the piston doesn't slow down for anything...there will be more presuraisation of the exhaust charge in the long stroke at the same piston speed. In most cases that would be a good thing. If it happens to be one large exhaust valve...the exhaust has to skirt that valve to exit. They flow research that VW audi was doing seemed to suggest that smaller valves offered lower resistance in both direction in filling an overly long stroke. God knows its hard to argue with the figures they get out of the dinky little stock motors they are using...itseems to work. What they also alluded to was that the magic itself was not done really by that valve function itself, but in the more elaborate tuning it offered them in their valve timing and exhaust manifolding. The lessons of too large of a valve in short stroke motors was learned long ago as well in v-8's. Mostly before head porting became a flow bench art on an everyday basis. Ray<HR></BLOCKQUOTE>