Water pump impeller compatibility with other models

[Jerry Hall]

im not making a new head but if i were, it would be in a similar direction as the pic above.  i wouldnt waste my time with coolhead or any of its copycat variants (wont mention any company names). most oem heads ive seen are designed well but unsuspecting people get sucked into exagerated sales pitches by aftermarket companies, so the oem parts get tossed on the shelf or sold. i think very few of these aftermarket companies actually have real engineers employed

Anytime I am designing something new, I have to have a list of things that are wrong with the old design before I can target the problematic areas with possible solutions to the problems.  If there are not problems with the old design that need improving, then there is not any need to spend time and money developing a new mouse trap.

Most of the OEM heads have room for improvement in improving the combustion efficiency.  I do not know of any of the OEM heads that need the cooling ability improved.  I have not seen any of the billet heads with removable domes that address the real issues I am concerned with.

I have CNC equipment that could make billet heads but have not done so because I do not think that it would improve the power or the reliability on most cases.  If I build a part it has to have an advantage in power and or reliability over the OEM part.  I will let the guys that do not really understand engines continue to make all of the bling parts and spend a ton of money trying to market them to the customers that do not really understand engines.

[udontknowme]

if you want to see a perfect example go on ebay and look at aftermarket banshee heads. theres 4 or 5 different companies making them and basically all they did is take a coolhead finned dome then made their own proprietary outshell around it. so pretty much all the aftermarket heads use the same coolhead dome :disgust:

[rablack21]

No one is disputing the need for more airflow. I have said this from day one. I also said early on that almost every shroud I have seen for the 250R is ill designed and not actually helping with air flow. Since we can "manufacture" air flow, we only have two options when it comes to obtaining more of it. We can either use a fan,(which I don't want to discuss in this thread) or to design better shrouds (which I will design after I get done with the new impeller).
Yes, we also mentioned earlier in this thread that there are several areas of poorly designed bottlenecks and rough casting areas. Since this requires multiple parts to be modified that are that way from their manufacturer, I don't find this idea to be as beneficial. If you increase the flow in the system by the impeller, it will help the system regain some or all of the flow it lost because of the rough castings and imperfections.

[Jerry Hall]

No one is disputing the need for more airflow. I have said this from day one. I also said early on that almost every shroud I have seen for the 250R is ill designed and not actually helping with air flow. Since we can "manufacture" air flow, we only have two options when it comes to obtaining more of it. We can either use a fan,(which I don't want to discuss in this thread) or to design better shrouds (which I will design after I get done with the new impeller).
Yes, we also mentioned earlier in this thread that there are several areas of poorly designed bottlenecks and rough casting areas. Since this requires multiple parts to be modified that are that way from their manufacturer, I don't find this idea to be as beneficial. If you increase the flow in the system by the impeller, it will help the system regain some or all of the flow it lost because of the rough castings and imperfections.

If the deta T between the radiator inlet and outlet temp is more than 10 deg it is time to improve the coolant flow rate.  If the delta T is less than 10 deg it is time to improve the heat exchange between the radiator and the atmosphere.  

What is your delta T at 10 mph, 30 mph, 50 mph?  If you do these simple test, I think that you will find that you are wasting your time pursuing more coolant flow through the engine and radiator.

[rablack21]

If the deta T between the radiator inlet and outlet temp is more than 10 deg it is time to improve the coolant flow rate.  If the delta T is less than 10 deg it is time to improve the heat exchange between the radiator and the atmosphere.  

What is your delta T at 10 mph, 30 mph, 50 mph?  If you do these simple test, I think that you will find that you are wasting your time pursuing more coolant flow through the engine and radiator.

Every system design and requirements is different, so what technical information or background research do you base your magical 10° off of? Just for clarity are you speaking of 10°C or 10°F, because there is a very big difference. And when you say it needs to be more than 10° delta T in order to be beneficial, to what speed are you speaking of? 10mph? 30 mph? 50mph? or are you speaking of at any given time? I think that you will find that throwing out a blanket statement like that is a little presumptuous and ridiculous.

[rablack21]

A higher flow water pump will also slightly raise the pressure in the system which helps prevent "hot spots" and "steam pockets" caused by poor water jacket design and poorly designed passage ways.

[Jerry Hall]

Every system design and requirements is different, so what technical information or background research do you base your magical 10° off of? Just for clarity are you speaking of 10°C or 10°F, because there is a very big difference. And when you say it needs to be more than 10° delta T in order to be beneficial, to what speed are you speaking of? 10mph? 30 mph? 50mph? or are you speaking of at any given time? I think that you will find that throwing out a blanket statement like that is a little presumptuous and ridiculous.

10 deg is not a magical number but a ballpark number that is an observed trend seen over 40 years of designing and modifying two stroke engines.

I have made and studied the test results of around 150,000 dyno runs and field test.  I see a lot of trends that are common on engine cooling systems.    I am a mechanical engineer.   I use theory to guide my design work.  I use test results to guide changes and make refinements to the original design.  We are taught theory in the engineering colleges around the world and learn how to use it as we gain hands on experience as we apply our education and past experience to real world projects.  

The Deta T is in deg.F.

Heat transfer is proportional to the delta T.  The speed at which the delta T is measured allows one to match the cooling system to the application.

My goal on this forum is to share my experiences and failures with the members.  If I prevent them making expensive failures I have accomplished my goal.  

We can get into the engineering that this topic is centered and display equations, graphs and other test results, but is probably beyond the scope of the majority of the members.  I try to communicate in layman's terms on this forum.

I was just trying to save you some time and money going down a road that I have been down many times on different engine development projects.   If you think that is ridiculous then take that journey.  I hope you arrive at a different destination than the Honda engineers and myself arrived.

[rablack21]

10 deg is not a magical number but a ballpark number that is an observed trend seen over 40 years of designing and modifying two stroke engines.

I have made and studied the test results of around 150,000 dyno runs and field test.  I see a lot of trends that are common on engine cooling systems.    I am a mechanical engineer.   I use theory to guide my design work.  I use test results to guide changes and make refinements to the original design.  We are taught theory in the engineering colleges around the world and learn how to use it as we gain hands on experience as we apply our education and past experience to real world projects.  

The Deta T is in deg.F.

Heat transfer is proportional to the delta T.  The speed at which the delta T is measured allows one to match the cooling system to the application.

My goal on this forum is to share my experiences and failures with the members.  If I prevent them making expensive failures I have accomplished my goal.  

We can get into the engineering that this topic is centered and display equations, graphs and other test results, but is probably beyond the scope of the majority of the members.  I try to communicate in layman's terms on this forum.

I was just trying to save you some time and money going down a road that I have been down many times on different engine development projects.   If you think that is ridiculous then take that journey.  I hope you arrive at a different destination than the Honda engineers and myself arrived.

While I appreciate you putting things in layman's terms for us simple folk, but I happen to be a mechanical engineer as well that happens to study, design, and spec cooling systems for a living. I also use theory to guide my design work and use test results to guide changes and make refinements to original designs. I also was taught theory in the engineering college that I went to and have traveled around the world with my work due to the engineering experience and capacity that I have.

You are right about the heat transfer being proportional to the delta T at the rated rpm (not speed), at a given airflow, that the engine produces it's highest heat rejection requirement, and the cooling system is balanced to meet this heat rejection based on this value. So, something we agree on.

While I appreciate you trying to save me money and time with your 40 years of engineering experience and testing on this exact situation, I respectfully disagree with your theoretical outcome and will continue to pursue this and do some actual testing.  A destination that you and Honda arrived at? Again, quite presumptuous.  Honda spec'd this cooling system for a 246cc engine, not anything larger. So I'm reasonably sure (not completely sure, because I don't want to be presumptuous) that Honda didn't study this specific application.

[matt250r21]

One thing I noticed about every billet o ringed sealed head that I have scene is the coolant passages are all the same size. You would think this is a good design while actually the OE designed head gasket with the different sized passage ways that force more coolant to the front of the cylinder is best. The only o ringed head that has the OE design that I know of is the cast Pro-X ones.

I like the idea of trying to improve the cooling system as much as possible and just the fact that someone may re produce the 89 250R style water pump shaft is great. Honda still sells the 89 impeller but not the shaft, go figure. I don't think you can even get the 85-88 style water pump parts anymore.

[Uns]

While I appreciate you putting things in layman's terms for us simple folk, but I happen to be a mechanical engineer as well that happens to study, design, and spec cooling systems for a living. I also use theory to guide my design work and use test results to guide changes and make refinements to original designs. I also was taught theory in the engineering college that I went to and have traveled around the world with my work due to the engineering experience and capacity that I have.

You are right about the heat transfer being proportional to the delta T at the rated rpm (not speed), at a given airflow, that the engine produces it's highest heat rejection requirement, and the cooling system is balanced to meet this heat rejection based on this value. So, something we agree on.

While I appreciate you trying to save me money and time with your 40 years of engineering experience and testing on this exact situation, I respectfully disagree with your theoretical outcome and will continue to pursue this and do some actual testing.  A destination that you and Honda arrived at? Again, quite presumptuous.  Honda spec'd this cooling system for a 246cc engine, not anything larger. So I'm reasonably sure (not completely sure, because I don't want to be presumptuous) that Honda didn't study this specific application.

I'm no mechanical engineer, but it seems delta T is the difference in temperature between the radiator and the engine.  In a zero air movement environment, your delta T should be theoretically zero, no matter what speed above a trivially low rpm you run the engine at.  It is in the heat exchange provided by the radiator that delta T increases.

What Jerry is saying is the water velocity's impact on the engine temperature is proportional to the difference in temperature between the radiator and the engine.  The MPH-only situation might be overly simplistic, and there would be a major difference between say 10krpm 2nd gear at 30 and 2krpm 6th gear at 30, but the speed of air passing by the radiator is an important component.

At these different speeds, if the "delta T" is zero, then a new impeller is pretty pointless.  If your delta T is 50, then it's probably worth it.  10 sounds like a decent ballpark figure.

This data, at different speeds, is exactly what I'd think any engineer would do before designing a "better" component.

Unless you just want your mouse trap to have death spikes and some mouse poison just to make extra sure.

[etccb]

One thing I noticed about every billet o ringed sealed head that I have scene is the coolant passages are all the same size. You would think this is a good design while actually the OE designed head gasket with the different sized passage ways that force more coolant to the front of the cylinder is best. The only o ringed head that has the OE design that I know of is the cast Pro-X ones.

I like the idea of trying to improve the cooling system as much as possible and just the fact that someone may re produce the 89 250R style water pump shaft is great. Honda still sells the 89 impeller but not the shaft, go figure. I don't think you can even get the 85-88 style water pump parts anymore.

All esr billet heads have always had more flow to the ex side then the intake side. Look at all of the passageway cutouts in the shell and you will see it. It has changed over time but there has always been something in theirs, but not always in others like you said.

edit=without making another post v v v v v, thanks z.

[zcarlson12]

I don't mean to hijack your thread Ryan but since this came up I thought I'd post on it. Red=Old ESR Black=New ESR

[rablack21]

I got the shaft modeled up this morning. Am working on making the drawings. Going out for quotes pretty soon. I'm gonna get these made in 304 SS. I'm gonna start another thread to see if other are interested in the shafts or the impellers to see how many to get quotes for.

[rablack21]