Board index

My Home Page

PilotOdyssey.com By hoser...


PilotOdyssey.com Chat Room

PilotOdyssey.com Photo Album

* Login   * Register * FAQ
http://www.pilotodyssey.com/PO/adm/images/imagemenu/smiley_cool.png PilotOdyssey.com Chat    http://www.pilotodyssey.com/PO/adm/images/imagemenu/find.png PilotOdyssey.com Google Search    http://www.pilotodyssey.com/PO/adm/images/imagemenu/emoticon_tongue.png FL400 Parts    http://www.pilotodyssey.com/PO/adm/images/imagemenu/emoticon_grin.png FL350 Parts    http://www.pilotodyssey.com/PO/adm/images/imagemenu/emoticon_evilgrin.png FL250 Parts    http://www.pilotodyssey.com/PO/adm/images/imagemenu/emoticon_unhappy.png Admin Email   
It is currently Thu Mar 28, 2024 3:10 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 37 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: FL250 PORT TIMING
PostPosted: Mon Oct 26, 2015 12:56 pm 
Offline

Joined: Wed Aug 26, 2015 6:40 am
Posts: 22
Ok so I see the shift you are talking about. So I guess my question still stands that this Engine in particular with the know mods where do I put the jug? What rpm will my power band be in? Thanks for all your knowledge!!


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Wed Oct 28, 2015 6:59 pm 
Offline

Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Fire LS1, I know you would like a simple put it here answer however it does not work that way. Please do not take this the wrong way If I answer you now it would not be what you are looking for. So I will answer with what I know.
Based on information posted your answer is a corrected volume at TDC (Top Dead Center) of 27.77 cc with a .050 head gasket.

See I do not have a crushed head gasket thickness or an ID, I do not have a volume for the Mean line of the ports. I do not have the piston dome cc. I do not have the head volume in cc's.

So what I did was take the stock numbers inter them in to a work sheet and came up with this number for .corrected volume at TDC (Top Dead Center) of 27.77 cc with a .050 head gasket. Now you will have to do the rest to determine the base gasket thickness. The best guess stock rpm is in the 6000 to 6500 range based off of duration numbers alone.

If I enter the plot #2 numbers into the work sheet using the base numbers I come up with 26.37 for corrected volume at TDC (Top Dead Center) This will up the rpm about 500.

So you can use the crappy answer or we can continue to work and get some real answers. Either way I glad to help.


Top
 Profile  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Thu Oct 29, 2015 10:06 am 
Offline

Joined: Wed Aug 26, 2015 6:40 am
Posts: 22
Ok will get you compressed volume and thickness of head gasket, cc of head and dome of piston. How do I measure volume of mean line of ports?


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Thu Oct 29, 2015 11:23 am 
Offline

Joined: Mon Oct 25, 2004 10:02 am
Posts: 2865
Location: East Peoria IL
I hate to be an ass, but isn't the idea to just repair your machine and ride? I thought Mr. Honda took care of all this when the Engine was designed. Hell I just want to ride the trails.

If I had an Engine that required this much work and thought, I would sell it and buy a stocker.

Just my honest opinion.

Please ignore me if you are into this kinda stuff. No harm intended.


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Thu Oct 29, 2015 2:39 pm 
Offline

Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
rmesser wrote:
I hate to be an ass, but isn't the idea to just repair your machine and ride? I thought Mr. Honda took care of all this when the Engine was designed. Hell I just want to ride the trails.

If I had an Engine that required this much work and thought, I would sell it and buy a stocker.

Just my honest opinion.

Please ignore me if you are into this kinda stuff. No harm intended.


I second this thought.
Hammer a spacer in it and call it good. Lets ride.
Please ignore me too.


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 7:28 am 
Offline

Joined: Wed Aug 26, 2015 6:40 am
Posts: 22
I am just trying to do the best job I can. You heard Adnoh I can use the crappy answer or get the real one. Things worth doing are worth overdoing. Isn't that how you learn?


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 2:37 pm 
Offline

Joined: Tue Jan 17, 2012 3:19 am
Posts: 7698
Location: Hope, B.C Canada
FIRELS1 wrote:
I am just trying to do the best job I can. You heard Adnoh I can use the crappy answer or get the real one. Things worth doing are worth overdoing. Isn't that how you learn?


I stand corrected.
Never really cared about how stuff looks as long as I could drive the s++t out of it.


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 2:48 pm 
Offline

Joined: Mon Oct 25, 2004 10:02 am
Posts: 2865
Location: East Peoria IL
I have a stock 1977 fl250 odyssey. I rebuilt it many years ago. I have no idea what the volume of mean line of ports is, and I never will, tell you the truth I have never thought about it and hope I never do. I do know it is fun to ride. Don't take me the wrong way, I love working on it and maintaining it, but volume of mean line of ports - good god man!

What's your end game with this machine? you gonna race it or just ride mud and sand?


Top
 Profile E-mail  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 7:17 pm 
Offline

Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
I think rmesser is entitled to His opinion. It good to here all side as far and what the heck. He is correct as it will most likely not make a real big difference. As our k-nock brother stated space and go. The down side is you question will never be answered. I do believe the "H"'s boards main goal is to educate, learn and have fun doing so. There fore I will do what I can based on my experience level for some one who is willing to learn. I have said it many times and still will , I am no professional in any way. I just want to learn and share like ever one else. I had to learn the hard way as this board was not around when I was burning up Engine's aka MOTORS. So when someone really wants to learn I take interest. Plus I learn a few things along the way. There is no documented FL 250 stuff around that I know of so some one has to do the work so it will be there for future enthusiast. Every thing posted here can be used in other application to a given point.

Here is a quick case and point. look at the manual for the 250 it list port timing, does it do so for the pilot. Now ask your self why did they remove it for the manual. Just guessing I would bet its due to most like rmesser could care less. Now ask yourself why 6.6 CR for the fl 250 and 6.2 for the fl400 pilot. The 250 manual is for a points with a @5 degrees before TDC (Top Dead Center). Now throw a what IF out there. What if a CDI (Capacitor Discharge Ignition) is added at what advance/retard??? Why do most of use pilot guys run 6.8 as a limit for pump gas at 7800 rpm???? so what does the 9 kg/cm2 convert to in psi and why does the pilot set higher at 150+/- with a lower CR????

Well that is what we are finding out in way of port timing and port time values If any one cares. It's about a static setting in a dynamic application. And lets not forget this is a bottom feeder with no valve. So we must consider the pressure drop or it will be all squirrely at low rpm and jetting a night mare.

I know BLA BLA BLAAAAAA.


Top
 Profile  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 8:14 pm 
Offline

Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
Fire LS1, what is done is make a port map. You can find this done on this site as its easy to do. Then you convert this map into square mm graph and count. The purpose of the mean line is to determine the amount to count for the time area. Lets say for a wild and easy example we have a square port of 10 x 40 easy right. 10 x 40 = 400 With a mean line of 50% port area this would be 200 still easy right. Now we go and mess with the port timing. The line is moved up and down. Now to 45 % or 55 %. This area above the mean line has a given amount of flow for a given amount of time as time increases the less work the port can do based on area. There is defined time area for given ports. They all have to play well with each other. The other item to consider with this calculation and I do not widely talk about till now is port roof angle to port cord width at a given mean line area. The angle will play a part in the rpm and peak torque. However we are a long way from that. since you have your cylinder on your Engine just look exhaust port at BDC and go that's a big hole Now move it to a mean line for plot one or 135 degrees ATDC snap a pic of the port. Now go to a base line setting of plot 3 at 136.5 degrees ATDC. Snap a pic and then over lay the two. Depending on the cord width and angle to the top of the port you will loose a lot of area as it is not square. The only fixed number is from the top of the port to the max cord width. The max cord width may need to be changed to the correct port time open. Then and only then can the rest of the port be brought into line base on time area for a given rpm range. So do we go higher which alters the blow down or do we increase the angle with a wider roof width or both. We need to factor in blow down due to there is limits for given rpm. Yes this is where the pipe comes into play and what about that pressure drop of the case according to TO I had mentioned. So the BD has to factored in to any change prior to cutting. Oh ya we have to determine the Intake and scavenging as well before we consider a change to BD.

If we need more Transfer TA ( time area) do we raise of widen or both. again need to factor in cord width of the transfer ports. If we need to taller to get more TA does this not change BD.

Now you see why the basic plot are important for each. If you did your BD for each plot you should have came up with
#1- 29.5, #2- 28.5, #3- 27
#1 plot shows a retard in timing does it not. So why do we need so much BD for a lower RPM. The ramming effect of the transfer at Pressure release will be late. What if the pipe is fast from the heat at an advanced EO. I would say rut ru. Now if was times correctly than we would have a vacuum in place of no or positive pressure at TO. I would say we need a larger head pipe or smaller stinger or longer LT.

Man that a big assumption just from a plot. however accurate.

So where does the 5 degrees of ignition timing lay into this. Simply put later the fire more heat at EO. oops the EO is earlier now and BD is greater. Now look at EC what did we gain in plot #1, 1 degree woopy do compared to the volume at TDC (Top Dead Center) with the piston above deck .055. Your CR was highly increased way above 6.8. remind me what happens when the pressure rises. Would this be higher heat load not only from combustion but also compression heating. As our K- nock brother say run race gas my man. Oops again, dam port open too soon and the pipe just got quicker. Kiss your intake charge good buy and weak. Would that lead to pre ignition and detonation. Did I also mention the ports mean TA being to small and it continues to lean out at the rpm increases. Yes say hello to mister hole in the piston or four corner or all out right failure.

Agin I went BLB BLA BLA, Sorry just trying to simplify thing a touch as we go and there possible effect.

Now for the good news, Kinda our intake duration went up the down side to this is back wash at low rpm( no valve) why?
we need to look at TO or IC to TO degrees for a given case CR.

Now for a what if on plot #1 we find the time area and area angle for the transfer and work from there. The transfers are usually pretty square and flat at port entry. IF, big IF here, we raise the transfer port 2 degrees we soften the blow back to Case CR problem. We also increase TA for the transfers. We now reduce the BD to 27.5. Now with that in check as long as the exhaust ort TA is in check we can factor in CCR ( corrected compression ratio) and wata bing wanta bang we have a new base line for a power pipe. Now what if its a touch pipey. We simple go in and change port roof angles on transfer and exhaust. This will flatten out the power curve and increase rpm.


Top
 Profile  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 8:28 pm 
Offline

Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
here is a couple of pics
the fl 250 base line is a work sheet in your work book that I use to build of and track changes.
The fl400 is accual angle area calcs for my pilot. Yes the ride data supports the calculation. I had to change other setting to operate at what I feel is peak capacity for that Engine. It will give you some kind of an idea of what were going to do and find.

You will need to down load or enlarge the fl400 to get see full data.

Thank you for our time and interest. Adnoh


Attachments:
base line numbers fl 250.jpg
base line numbers fl 250.jpg [ 62.43 KiB | Viewed 1122 times ]
fl400 dcp.jpg
fl400 dcp.jpg [ 31.25 KiB | Viewed 1122 times ]
Top
 Profile  
 
 Post subject: Re: FL250 PORT TIMING
PostPosted: Fri Oct 30, 2015 8:36 pm 
Offline

Joined: Fri Jan 12, 2007 2:17 pm
Posts: 3620
Location: Wichita ks
here is a pic of the angle area chart were working with.


Attachments:
angle area charts.jpg
angle area charts.jpg [ 57.68 KiB | Viewed 1121 times ]
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 37 posts ]  Go to page Previous  1, 2

All times are UTC - 5 hours [ DST ]


Who is online

Registered users: Bing [Bot], Google [Bot], Lanix


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group