 Janbros' 2stroke excel for ports, heads and pipes  

+7tibus Maurice Specken carlovitch1 fullgazlolo motori49 ReinanRacing JanBros 11 participants 
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JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Janbros' 2stroke excel for ports, heads and pipes Dim 12 Jan 2020  1:45  
 thought I'd better open a topic to keep track of updates/corrections. My 2stroke spreadsheet is ready (for now at least), so I'm throwing it on the net so everybody can use it. It contains pages for ports, the head and FOS pipe On the seperate ports pages (exhaust and transfer), it calculates the STA numbers (Specific Time.Area) of your ports and you can matcch them to the target's, determinned by the BMEP On the Head page, you can design your head and it calculates the MSV (Mean Squish Velocity) 100% accurtly with Blair On the FOSpipe page, it calculates a Frits Overmars FOS pipe, and you can ad a Wobblyduct , and you can add extra header/diffusor/baffle sections to the pipe. you are free to do with it what you want, as long as it is not for commercial use. If somebody has idea's to improve or add extra features, please share so we can all benefit. In the manual I've tried to explain how it works, please read it first before you ask questions. [Vous devez être inscrit et connecté pour voir cette image]a small error has come up : on the Data page , in cell Q14 both "exhaust new" should be "exhaust old" , so change it yourself or download it again. new download links to version 1.2 : excel : [Vous devez être inscrit et connecté pour voir ce lien]manual : [Vous devez être inscrit et connecté pour voir ce lien]
Dernière édition par JanBros le Lun 13 Jan 2020  20:43, édité 1 fois 

 
ReinanRacing
Nombre de messages : 54 Localisation : Japon Date d'inscription : 24/06/2018
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 12 Jan 2020  13:43  
 If you put your intellectual property on the net, I strongly recommend that you add a license; a license allows you to avoid the application of your work for purposes you do not endorse (such as, in your case, commercial use). One of the best options is one of the socalled "Creative Commons" licenses, which are specifically designed to license individual creative endeavours. There are several licenses available, check the website: [Vous devez être inscrit et connecté pour voir ce lien]You can choose a Creative Commons License, for example, in your case, you could choose "AttributionNon CommercialShare Alike International 4.0". The process of adding the license is easy, just type in the original Excel file: "This work is protected under the XXX license". If you go to the website of Creative Commons, they will give you a hyperlink to put into your work. As another point, I am involved with various "open software" developments and I know from experience that quality control is very important. I encourage you to write a document specifying specifically all of the equations you use in your work. It will make your own development easier, it will help other users to understand your work, and most of all, it will help others to find and solve any mistakes you may have made. 

 
motori49
Nombre de messages : 197 Age : 72 Localisation : Turin Italie Piemont Date d'inscription : 02/12/2015
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 12 Jan 2020  14:01  
 merci JanBros magnifique travaille 

 
fullgazlolo
Nombre de messages : 1805 Localisation : GECH Date d'inscription : 04/01/2016
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 12 Jan 2020  15:15  
 

 
carlovitch1
Nombre de messages : 753 Localisation : Pays Catalan Date d'inscription : 20/05/2018
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 12 Jan 2020  17:38  
 

 
Maurice Specken
Nombre de messages : 5 Localisation : Holland Date d'inscription : 10/05/2014
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Lun 13 Jan 2020  14:10  
 Congratulations Jan Bros,
As my son and I did something similar (only in a raw version and not that extended) we know how much work this must have been for You. Deep respect We will dive into it ( I hope to start this evening) to look for deviations between our calculations and yours just to verify and learn.
Regards Maurice 

 
tibus
Nombre de messages : 7 Localisation : France , panam Date d'inscription : 30/01/2013
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Lun 13 Jan 2020  20:22  
 good job Jan Bros thanks ! 

 
JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Lun 13 Jan 2020  20:35  
 some more corrections for "IF" errors in situations I hadn't tested yet, and added a page you can print and take into your shed to write down all the needed input data. 

 
MkRacing
Nombre de messages : 4 Localisation : Malaga Date d'inscription : 30/04/2020
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Ven 1 Mai 2020  22:02  
 Thank you very much for doing this great job and sharing it. 

 
hoolish
Nombre de messages : 66 Localisation : Lyon Date d'inscription : 11/04/2017
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 3 Mai 2020  13:21  
 Great work, that's impressive ! 

 
MkRacing
Nombre de messages : 4 Localisation : Malaga Date d'inscription : 30/04/2020
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 3 Mai 2020  19:33  
 Hello, I have some doubts with the JanBros Excel translation. I do not understand any concept to complete your data sheet. I upload a photo with my deduction on how to take the measures to correct me. Thank you [Vous devez être inscrit et connecté pour voir cette image] 

 
JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 3 Mai 2020  20:16  
 I measure crown height from top of piston to top of pistonpin bore, so you should deduct half of the pistonpin diameter from your crown height.
I already realised pistonpin is not mentionned in the spreadsheet, so I'm reworking it a bit and am seperating all the moving parts from the nonmoving parts between old and new, so that when somebody uses a bigger/smaller pistonpin, the difference will be counted for.
If anybody has requests for some changes, now is a good moment ;) 

 
MkRacing
Nombre de messages : 4 Localisation : Malaga Date d'inscription : 30/04/2020
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 3 Mai 2020  20:31  
  JanBros a écrit:
 I measure crown height from top of piston to top of pistonpin bore, so you should deduct half of the pistonpin diameter from your crown height.
I already realised pistonpin is not mentionned in the spreadsheet, so I'm reworking it a bit and am seperating all the moving parts from the nonmoving parts between old and new, so that when somebody uses a bigger/smaller pistonpin, the difference will be counted for.
If anybody has requests for some changes, now is a good moment ;) Thank you very much for your answer, I upload a new corrected image. Another question, Deckheight = Squish? [Vous devez être inscrit et connecté pour voir cette image] 

 
JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 3 Mai 2020  21:02  
 deck = top of the cylinder deckheight = distance from top of cylinder to pistonedge. so if the piston sit's lower than the deck, you enter the distance as a positive number. if the piston comes above the deck, you enter the distance as a negative number. squish = the outside area of the combustionchamber , between points 1 and 2 [Vous devez être inscrit et connecté pour voir cette image]squishheight = distance between top of cylinder and squish area of combustion chamber where the distance is lowest (in case of a tangent squish area, when squish is paralel, it should be the same between points 1 and 2). 

 
MkRacing
Nombre de messages : 4 Localisation : Malaga Date d'inscription : 30/04/2020
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 3 Mai 2020  21:26  
 Thank you very much for your answer, I understand it perfectly. My native language is Spanish, I don't know the technical concepts in English. 

 
rataraditya
Nombre de messages : 2 Localisation : netherlands Date d'inscription : 23/05/2020
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 7 Juin 2020  19:10  
 Hello Mr. Janbros,
I am trying to understand more about how to tune a 2 stroke by looking at your excel sheet and read the discussion which is managed by Jan Thiel and Frits Overmars. Therefore, I would like to ask some of question about your excel.
1. The whole idea of the excel, apart from the sheet Head and the FOS pipe is we strive for achieving the target Blow down and Transfer STA, right? Considering that these STA numbers for blow down (8.12) and Transfer (66.16) are achieved from RSA 125 which has >1 exhaust port, is it possible to get the same number for a singleexhaust port 2 stroke machine? Or do we have to adjust/tune the port of this single exhaust port cylinder as close as possible to that STA target?
2. I see that in cell AK28: AO45, there is a calculation for STA target. I am interested in the Blair formula for both BD and Transfer. For BD, it is written as (BMEP1.75)/0.8187/2. In his book, it is (BMEP1.75)/8187 (pg. 261, basic design 2 stroke, Blair). I assume that 8187 to 0.8187 is conversion from meter to millimeter, but what is the purpose of dividing it by 2? This also works for Transfer where you divided it by 4.
3. The width that we put in the port map data for both exhaust and transfer. What kind of width is that? How should we obtain the width?
4. What is the definition of cylinder height?
Thank you in advance for your help.


 
JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Dim 7 Juin 2020  20:20  
  rataraditya a écrit:
1. The whole idea of the excel, apart from the sheet Head and the FOS pipe is we strive for achieving the target Blow down and Transfer STA, right? Considering that these STA numbers for blow down (8.12) and Transfer (66.16) are achieved from RSA 125 which has >1 exhaust port, is it possible to get the same number for a singleexhaust port 2 stroke machine? Or do we have to adjust/tune the port of this single exhaust port cylinder as close as possible to that STA target?
2. I see that in cell AK28: AO45, there is a calculation for STA target. I am interested in the Blair formula for both BD and Transfer. For BD, it is written as (BMEP1.75)/0.8187/2. In his book, it is (BMEP1.75)/8187 (pg. 261, basic design 2 stroke, Blair). I assume that 8187 to 0.8187 is conversion from meter to millimeter, but what is the purpose of dividing it by 2? This also works for Transfer where you divided it by 4.
3. The width that we put in the port map data for both exhaust and transfer. What kind of width is that? How should we obtain the width?
4. What is the definition of cylinder height?
Hi, 1/ you'll never be able to have enough blowdowntime.area with a single exhaust port, or if you'd try you'd end up with rediculous exhaust timing. compare it with a fourstroke using only 1 exhaust valve vs 2 : it's impossible to exit the same amount of exhaust gas in the same time through a smaller hole. 2/ honestly, I can't remember. probably because it was the only way to make the numbers work with all the data Frits and Jan have given. if you don't devide them , the STA numbers ain't comparable. 3/ that's explained in the doccument youcan download. you enter the circumferential (is that english ?) width , the one you measure on the portmap, not the chordal width. 4/ it's the height drom the top of the cylinder to the flat part at the bottom that sits on the crankcase. but there is a problem with that, as if you give a different height for the new one, it's not specified where the difference is compared to the ports : below or above the ports. I'm reworking it, but it is not on my priority list at the moment. 

 
rataraditya
Nombre de messages : 2 Localisation : netherlands Date d'inscription : 23/05/2020
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Lun 8 Juin 2020  6:37  
 Dear Mr. Janbros, Thank you for answering my question . Here's my comment: 1. So basically, maybe what I can do now is taking the recommended exhaust and transfer duration by Frits, 190 deg and 130 respectively, and adjust the ports width up to mechanically accepted value. And compare it to the STA values. What do you think? 2. Okay, I will follow that formula then. 3. Yes, after I check your excel cell again, I see that there is a formula to convert the width that we enter in the port map cell into chordal width. Moreover, it is written in the manual. Sorry for not reading that 4. I see. I try to change it and it doesn't affect the STA, Power or duration. It only change the values under the Port Data in Data Sheet. So the best way to put the correct number of this cylinder height is by entering any number of cylinder height so that the value under the Port Data has the same value with real distances of the ports ( example: DeckMain Bottom in Port Data = DeckMain Bottom in real measurement). What do you think? Thanks for your help. 

 
JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Lun 8 Juin 2020  22:06  
  rataraditya a écrit:
 Dear Mr. Janbros,
Thank you for answering my question . Here's my comment:
1. So basically, maybe what I can do now is taking the recommended exhaust and transfer duration by Frits, 190 deg and 130 respectively, and adjust the ports width up to mechanically accepted value. And compare it to the STA values. What do you think?
2. Okay, I will follow that formula then.
3. Yes, after I check your excel cell again, I see that there is a formula to convert the width that we enter in the port map cell into chordal width. Moreover, it is written in the manual. Sorry for not reading that
4. I see. I try to change it and it doesn't affect the STA, Power or duration. It only change the values under the Port Data in Data Sheet. So the best way to put the correct number of this cylinder height is by entering any number of cylinder height so that the value under the Port Data has the same value with real distances of the ports ( example: DeckMain Bottom in Port Data = DeckMain Bottom in real measurement). What do you think?
Thanks for your help.
1/ you can not expect your engine to get the same BMEP as an RSA. enter the BMEP you think you'l be able to distract from it, and than try to match the numbers. if you can't lower BMEP. 4/ as it is now, the height difference is always at the top, so if you enter a higher height for the new cylinder, it only changes the distance deckports. that change has no effect on the ports themselfs. 

 
Frank S.
Nombre de messages : 2 Age : 55 Localisation : Allemange Date d'inscription : 04/10/2018
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Ven 26 Mar 2021  19:11  
 Hi Janbros, first of all: Great Job There is a thing I would like to know about this "out of breath". Is it the rpm where the torque (or power) curve is not raising any more and drops? Or is it the rpm where the engine doesn´t rev higher? I have read the RSA topic but couldn´t find an answer. Thanks in advance Frank S. 

 
JanBros
Nombre de messages : 295 Localisation : Belgique Date d'inscription : 05/12/2011
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Sam 27 Mar 2021  9:46  
 Frits explained it acouple of times, but it is the rpm after which torque lowers again, because the engine can't get more mixture in the cylinder to raise torque further. for example : if your goal was to get max torque at 10000 and "out of breath" only says 9000, you either aimed too high or you have to enlarge the corresponding angle.area. 

 
Frank S.
Nombre de messages : 2 Age : 55 Localisation : Allemange Date d'inscription : 04/10/2018
 Sujet: Re: Janbros' 2stroke excel for ports, heads and pipes Sam 27 Mar 2021  11:03  
 Merci beaucoup, I thought so, but I was confused because my Inputs gave the exakt RPM, where my engine stalls. Strange coincidence 🤪 Now it is clear and I habe readjusted my inputs. Greets Frank 

 
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 Janbros' 2stroke excel for ports, heads and pipes  
