Gabbing about 212 Hemi ports

[TheInspiredFool]

Ok, as far as how air flowing through the engines ports effects cooling the cylinder goes I suppose I wasn't explaining myself and the effects of it very well. All airflow matters especially cold outside air...relative to the hot engine.

So as you were saying about the engine heating up at idle as the airflow decreases we need to consider the combustion cycle has decreased and energy output of the engine has decreased as well, thereby decreasing heat output. Does it make a drastic impact on upper cylinder temperatures? Who knows. The fuel mixture really makes a difference though. You can make a little more power by running a bit lean at the cost of higher head temps and also you can run a little richer and drop your head temps at the cost of a minute amount of power. That's pretty much a proven fact.

Is it negligible with these small engines? Yeah, who cares I guess. I think you could measure the effect with the right equipment though.

Some engineer decided to implement a rear cylinder shutoff on Harley Davidson air cooled engines when outside air temp exceeds a certain temp. It just moves air through the cylinder in an effort to cool the entire engine when you're sitting at idle. Does it work? Yeah, it's annoying sitting on the vibrating thing...but whatever works.

Thanks for going into it more. I understand.

---------- Post added at 06:26 PM ---------- Previous post was at 05:44 PM ----------

They still apply. Be leery of the overly simplified formulas you might find in places like Hot Rod magazine or something. They often round-off numbers, shorten decimal places, make assumptions about the engine, and then condense it into some constant where all that monkey business is not visible. The more variables you have to plug in, the better.

If you can make the port smaller with the same or better flow, then the engine should make more power under the curve.



You probably won't get noticeably better throttle response without lighter parts and/or a pumper carb. Singles have the disadvantage of 720° firing. At low rpm, response to a throttle snap is delayed until the next intake stroke comes around. Then there's going to be a lean AFR spike as fuel starts moving and the port walls get wetted.

Incidentally, a throttle chop causes the AFR to rock bottom briefly as that fuel is pulled off the ports under low airflow. Fortunately it seldom affects driveability.



No, they're affected the same way. It's less noticeable the less power an engine makes. There again, most people trying to get more power out of these engines are also spinning them a lot higher.



If you're not after actual flow numbers, then a simple flow bench that provides only comparative results would be simpler and easier to build. Dynos can be done that way too, but the only real difference is the data collection. Might as well make it spit out real numbers.



That's to keep the hotter rear cylinder from overheating though(and by extension, the rider sitting over it); it doesn't cool the front one.

Thanks for the response and info ShelbyClone.

They still apply. Be leery of the overly simplified formulas you might find in places like Hot Rod magazine or something. They often round-off numbers, shorten decimal places, make assumptions about the engine, and then condense it into some constant where all that monkey business is not visible. The more variables you have to plug in, the better.

If you can make the port smaller with the same or better flow, then the engine should make more power under the curve.

That's what I figured. I was wondering why I have not seen others address this on near stock applications.

I agree. I am very leery of over simplified formulas. I long hand all of my own formulas out, go to the 4th decimal place and run various scenarios with various inputs for the variables that are specific to what my application could see. Then I take the best guessed scenarios and tune the average with all of the other corresponding formulas and build a chart with all of the differing variables to get the best picture of scenarios. Then I tune for the best average in consideration of the compromises involved. I don't do well just going with the short-cut formulas or "rule-of-thumb stuff. I get as exact and accurate as necessary.

You probably won't get noticeably better throttle response without lighter parts and/or a pumper carb. Singles have the disadvantage of 720° firing. At low rpm, response to a throttle snap is delayed until the next intake stroke comes around. Then there's going to be a lean AFR spike as fuel starts moving and the port walls get wetted.

Incidentally, a throttle chop causes the AFR to rock bottom briefly as that fuel is pulled off the ports under low airflow. Fortunately it seldom affects driveability.

I understand the long legged stumble with the 720 degree firing but I figure that the uptake in velocity, quicker ability for the de-pressurization to afftect up stream movement quicker and ability to fill the cylinder more effectively and efficiently would accompany the rider with better responsiveness, especially where efficiency on the low to mid valve lift events are more critical.

No, they're affected the same way. It's less noticeable the less power an engine makes. There again, most people trying to get more power out of these engines are also spinning them a lot higher.

That's what my thinking was as well but I am open to the fact that I can be wrong so I seconded guess myself and opened up to learn something new. I guess the few people that leave the internals mostely stock but work the ports without going to top rpm just either don't care or don't think it's worth the time and effort to try to dial them in. Or they just don't know.

If you're not after actual flow numbers, then a simple flow bench that provides only comparative results would be simpler and easier to build. Dynos can be done that way too, but the only real difference is the data collection. Might as well make it spit out real numbers.

Very true and I am on the verge of deciding to build a Flow comparison bench. I have already asked my wife to pick her favorite vaccum (since we have 4 or 5) in case I end up using 2 or 3 of the motors to build a flow bench. Lol The thing is that I have a couple of Arduino's and a RaspberryPI with a nice assortment of sensors laying around that I am always tempted into putting to good use and making my initial simple build into a much better but more complicated and time comsuming build. The same goes for the dyno. I could build a whole friggin performance tunning shop with those things! I just get too involved and can't help but build accuracy and testing variable number producing nerd machines once I try to build something simple. Lol Numbers, accuracy, testing, efficiency! I can't stop myself!

 

[BigWes]

That's to keep the hotter rear cylinder from overheating though(and by extension, the rider sitting over it); it doesn't cool the front one.

Just so happens I've sat on mine long enough in beach traffic with the thing idling like that to watch the entire crankcase temp drop over time. Not the other cylinder head. Had you read what I wrote that's not quite what I said..I said entire engine...but thanks for taking what I said out of context. No matter. It's not instant by any means but it happens. You can call me a liar if you want. Creeping along in parade mode. I don't sit there and burp the throttle either. I know why it's there. To prevent early wear on the rear cylinder thanks to California emissions restrictions and the overly lean fuel mix required to pass it. Which is death to an air cooled engine. Aye, she needs more fuel Cap'n!!! And it really doesn't help the rider...at some point I get too hot and shut the thing down. Anyway, back to the topic at hand.

I wanna see this home made flow bench. And this home made dyno.

I wanna learn how to make one.

 

[TheInspiredFool]

About the flow bench and dyno... I'm not sure if I am going to pull the trigger on those just yet. I would be more likely to put together a flow bench at this point and my wife has noticed me staring at the vaccums enough to know that some may come up missing very soon. I have other work to tend to that keeps me from just jumping into too many projects at once. I have too many as it is. Just like the gokart project. I could of left it as it was but now I'm porting, polishing and screwing around with it way more than necessary. The same would go for the flow bench and dyno. Lol I will see. Maybe.

 

[Flyinhillbilly]

I made my own sumo, used it for years, wore it out, and turned it into a welding cart.
I e been playing with the idea of building a chassis sumo for karts that I can that to the track.

 

[TheInspiredFool]

What is a sumo? I'm guessing a type of dyno?

 

[Flyinhillbilly]

What is a sumo? I'm guessing a type of dyno?

I meant dyno. Autocorrect strikes again.

 

[TheInspiredFool]

Ok. I thought it was dyno but I second guessed myself since spell check got you twice lol Very cool. I will check out your thread on it. I thought of doing a hydraulic dyno and a electric motor dyno driving a semi alternator. The alternator could be adjusted for torque using an adjustable resistor and you could run several different dummy loads and monitor output amps in an algorithm to determine tq and hp. A SBC (single board computer) could be installed to run variables and read the data plus spit it out to a computer for live as well as data collection and print functions.

I originally wanted just a break-in dyno, then a simple comparative dyno.. Which lead to a full on top-notch accurate sensor rich, data collecting beast of a dyno. Lol

 

[mckutzy]

I mentioned that earlier about the Hillbilly Dyno...
Cool piece of kit, on the home brew

 

[TheInspiredFool]

I mentioned that earlier about the Hillbilly Dyno...
Cool piece of kit, on the home brew

Yes you did, I remember. I looked at it quite some time ago when I was thinking of building one a while ago. It was nice. My plans then were more elaborate and involved being able to run my ZX6R on it with a turbo and high velocity ports (now THAT engine has some over porting issues in stock trim!) so I didn't take many mental notes. I will have to go back and check it out if I decide to pull the trigger on building one similar. I already should have done a base run with this engine for later comparison so it's a little late now that I have started. A flow bench might still be in the works though.

 

[BigWes]

It still concerns me that FHB wore out a sumo...if that doesn't give you nightmares...lol

 

[TheInspiredFool]

It still concerns me that FHB wore out a sumo...if that doesn't give you nightmares...lol

Lmao yeah, no kidding.

Thanks for that. Now all I can imagine is a sore, worn out, depressed sumo folling FHB around holding a Hobart welder trying not to get flash burn....