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  1. #1
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    Yamaha HPDI build/port work (let's talk port timing)

    Recently I picked up a 03' 225 vmax with a blow piston. I've finished tearing it down and intend on doing some engine work before it goes back together. I have talked to FORBESAUTO to pick his brain a bit after reading his HPDI rebuild thread. I have also talked to CHAZ a tiny bit about head work and will send my heads to him for some work once I get off my ass.
    I've more or less finished mapping out the current port layout. I chose to ignore the large chamfer that Yamaha put in the top of the exhaust ports when I took my measurements so my dimensions vary slightly from Forbes' measurements.
    Currently:
    Exhaust- 162⁰ duration, time area- .0001175, angle area 4.635
    Transfer - 122⁰ duration, time area- .0001070 angle area 3.856
    Boost - 126⁰
    Blowdown - 18⁰

    I did not calculate blowdown areas. And my transfer numbers aren't perfect but they are close enough to be workable I believe.

    As Forbes talks about in his thread, this motor is very choked down in the exhaust port and blowdown duration, transfers seem to be reasonably set up when compared to Jenning's numbers as well as numbers that are used in the old Macdizzy 2 stroke forums.

    I don't have a 300 sleeve to map but from what I have figured out the 300 sleeve has about 180⁰ of exhaust duration which equates to around 27⁰ blow down which seems more in line with numbers I've seen when dabbling in some older 2 stroke dirt bikes and ATV's (TRX250R)
    These are rough estimates based on measurements I've found on the internet and FORBES' thread.

    My initial thoughts on grinding ,before estimating the 300 exhaust port, was to leave the transfers alone and work the exhaust.
    Widen the exhaust port 1mm per side and raise the roof 2mm.
    This should give me
    166⁰ duration 0.0001368 TA and 4.936. AA with 22⁰ blowdown

    This still isn't a ton of blowdown but brings the exhaust into better shape. Generally speaking the idea with the atv's was to go wider before going up to keep decent BD numbers to retain some bottom end and a broader power delivery.
    However I'm now debating leaving the port width alone and moving up 170⁰ ish of exhaust duration instead. Motor is going on a Hydrostream so not pushing a ton of weight.

    I am by absolutely no means an expert (as any of the experts will realize by reading this) but I am hoping to start a reasonable discussion about port numbers and layouts that work for other guys and other motors. Not asking for anyone's championship winning engine parameters. But I also feel like a healthy dialog can be had regarding porting and engine setup for amateurs and guys that like to dabble. My reasoning for trying to avoid deck height measurements is because it makes it hard to compare different motors and different manufacturers.

    I will post some pictures once I take some that are worth posting.

  2. Thanks aj06bolt12r thanked for this post
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  3. #2
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    A few pictures of the blown piston. Crank, rods, bearings all look great after tear down. Which is a pleasant surprise.
    Click image for larger version. 

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    Can see a bit of damage to the exhaust port roof. Will see what it looks like after it's been ported a bit. Machine shop will have the final say on whether or not to re sleeve it.
    Last edited by canuckr; 02-13-2021 at 06:15 PM.

  4. #3
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    A few more boring pictures. Port map that was created by basically doing a pencil rub inside the cylinder to copy the ports. Some careful measurements are made, then transferred to graph paper. Crank shaft center and stroke radius are established. Port mean opening is found out and marked (based on crank duration not port height) port area was then manually counted using the graph paper. Some weird bu let easy math and you can establish time area and angle area to compare to Jenning's numbers. Makes it fairly easy to get an idea of what tune your engine is currently in and where to start looking for more power.
    There is a lot more to making an engine run than just grinding some ports. Transfer port passages, roof angles and direction play a lot into the characteristics of how an engine will behave and produce power.
    Click image for larger version. 

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    And a port map from a TRX250R cylinder I worked on years ago.
    Click image for larger version. 

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    Once again. Not a professional and I don't do this very often.

    Sorry for sideways pictures. Posting directly from phone will attempt to figure it out.
    Last edited by canuckr; 02-18-2021 at 07:53 PM.

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    Started to make chips. Exhaust ports are roughed in, have started to clean up the mismatch in the transfers and transfer feeds at the bottom of the cylinder. Reaching the bottom of the cylinders is easier said than done....
    Red line - is what the factory port opening is (according to dimensions from replacement sleeves)
    Green line - 3mm up (my cut to line)
    Blue line - factory 300hp dimension (based on dimensions from replacement sleeves)

    Click image for larger version. 

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    Example of the port mismatch on the bottom of the transfer inlets.
    Click image for larger version. 

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    Attached Thumbnails Attached Thumbnails 20210220_161506.jpg  
    Last edited by canuckr; 02-20-2021 at 08:57 PM.

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    I give up with the picture orientation.....

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    These are numbers for a 3600+ cc 3.0L merc.

    This program will do both G. Jennings and Dr. Blair's time area calc's .

    What percentage of bore to Ex. port width did you settle on. 70% is considered max , I generally go no more than 65 ..

    P.S.
    Chaz= I miss the old MacDizzy forum ...


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    An oldie but goodie ...

    http://www.amrca.com/tech/tuners.pdf

    Redundant , but a bit of Bell and Blair

    http://www.330.dk/

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    Chaz. I think I have that program. It can read port maps and figure out the numbers for you. I'm gonna try again to put my port maps through it and see how close it's numbers are to mine.
    The numbers for that merc motor. Factory port layout?
    Will probably shoot for the 65% exhaust port width as well. Need to reconfirm some measurements and keep grinding.

    Macdizzy was a great place to spend hours and hours reading

  10. #9
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    Quote Originally Posted by Chaz View Post
    An oldie but goodie ...

    http://www.amrca.com/tech/tuners.pdf

    Redundant , but a bit of Bell and Blair

    http://www.330.dk/
    Nice thread! Hard to improve on factory design. Best for an amateur just to clean and match things up, or maybe copy the specs of the higher HP like motor. Interesting and complex technology to say the least. The two stroke outboard designs have not evolved much since these books were written, compared to the motorcycle and sled- jetski industry. The most evolution has been the DFI area. This leads me to my thoughts and questions. How do DFI motors respond to port modifications? I would think they are much more dependent ECM tune, Injector pulse width, fuel pressure, compression ratio ect. I know for sure they live much closer to the razors edge. Really leaves us backyard tuners, at least that's what I am, with many questions. I am much more confidant messing with my EFI and carb motors.

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    Quote Originally Posted by cali kid View Post
    Nice thread! Hard to improve on factory design. Best for an amateur just to clean and match things up, or maybe copy the specs of the higher HP like motor. Interesting and complex technology to say the least. The two stroke outboard designs have not evolved much since these books were written, compared to the motorcycle and sled- jetski industry. The most evolution has been the DFI area. This leads me to my thoughts and questions. How do DFI motors respond to port modifications? I would think they are much more dependent ECM tune, Injector pulse width, fuel pressure, compression ratio ect. I know for sure they live much closer to the razors edge. Really leaves us backyard tuners, at least that's what I am, with many questions. I am much more confidant messing with my EFI and carb motors.
    After getting into this motor there are definitely places to make improvements even if it's just copying the higher HP motors. The DFI engines should behave almost exactly the same way to engine mods as their efi/carb'd predecessors. It still needs to push the air and exhaust through the same routes. It just gets the fuel added at a different time/location.

    Unlike the 4 strokes (Yamaha at least) where nizmo has been able to tune the 200's up to 332hp the same as the factory 300's.

    A friend of mine is into the Yamaha ECU already and we intend on doing some tuning work to see what we can do on that end. It's a personal project so the tuning work will probably be a little "broad brush" compared to having the power head off and on a dyno.

    Motor will get a pair of EGT probes to aid in the tuning.

    Chaz. The exhaust ports are currently at 61% of bore so they will get pushed out to the 65% ish mark like you mentioned in your previous post.

  12. #11
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    Quote Originally Posted by canuckr View Post
    After getting into this motor there are definitely places to make improvements even if it's just copying the higher HP motors. The DFI engines should behave almost exactly the same way to engine mods as their efi/carb'd predecessors. It still needs to push the air and exhaust through the same routes. It just gets the fuel added at a different time/location.

    Unlike the 4 strokes (Yamaha at least) where nizmo has been able to tune the 200's up to 332hp the same as the factory 300's.

    A friend of mine is into the Yamaha ECU already and we intend on doing some tuning work to see what we can do on that end. It's a personal project so the tuning work will probably be a little "broad brush" compared to having the power head off and on a dyno.

    Motor will get a pair of EGT probes to aid in the tuning.

    Chaz. The exhaust ports are currently at 61% of bore so they will get pushed out to the 65% ish mark like you mentioned in your previous post.
    Yea, Just figure out how to richen up the fueling. Good luck.

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    Minor changes , port clean up like that transfer which appears that the aluminum is 10~20% smaller than the steel sleeve ... will always run better if matched up.

    I would only widen the first 30* of ex port opening and then blend it into the stock port width. Even if the blow down degrees are less than 30* , it will still help. Once the transfers open , a wide lower two thirds of the port will only make it easier to short circuit .

    Cali ... didn't you do the conversions back to older model EFI parts .. ??
    If I was to do a Yamaha, that's the way I would want to go ..

    Don't the Yamaha's use something like 800 psi of fuel / air pressure .. ? Or the pumps will make that and are regulated down from there .. ?
    If so, thats a lot of wiggle room , to get fuel into the chamber.

    The poor 300xs pumps 105 on a gauge , and the air side of the fuel system puts out 110 psi at best. Clip the heads on one of those , and it will push the fuel back into the tank. Same thing when the air pump gets weak or rips the tracker valve diagram .. lean city / squeak ..


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    Cali.
    I think I read about you swapping OX66 stuff into an HPDI. I would also like to hear more about that.
    My friend that's going to help me tune is quite involved in the SXS and snowmobile markets. Helping some other aftermarket companies hack and tune ECU's. So I'm hopeful we can do more than just add some fuel.

    Chaz
    I started to widen the exhaust ports today. The Yamaha chamfers are generous and moving the ports to 65% barely just removed the chamfers on the sides of the ports. About 1mm on each side.

    The exhaust port work still hasn't quite matched up to the casting in the aluminum at the port roof. However it was enough to clean up the damage on the exhaust port in the blown cylinder.
    So hopefully it won't need a sleeve.

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    Quote Originally Posted by canuckr View Post
    Cali.
    I think I read about you swapping OX66 stuff into an HPDI. I would also like to hear more about that.
    My friend that's going to help me tune is quite involved in the SXS and snowmobile markets. Helping some other aftermarket companies hack and tune ECU's. So I'm hopeful we can do more than just add some fuel.

    Chaz
    I started to widen the exhaust ports today. The Yamaha chamfers are generous and moving the ports to 65% barely just removed the chamfers on the sides of the ports. About 1mm on each side.

    The exhaust port work still hasn't quite matched up to the casting in the aluminum at the port roof. However it was enough to clean up the damage on the exhaust port in the blown cylinder.
    So hopefully it won't need a sleeve.
    Chaz, & canuckr, You guys have good memories. I had a bunch of warranty 3.3 Yamaha powerheads laying around, as well as some toasted OX66 stuff. It was pretty easy to put the two together. Cost almost nothing. The motor is on the back of a 25 Parker and still running strong. I am scared of the HPDI operating system. It did fine on the 2.6 motor, not so good on the 3.3. Yamaha couldn't even get it rite. I am a huge fan of the 3 liter Merc for modification. Follow most of Chaz's posts.

  16. #15
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    Quote Originally Posted by Chaz View Post
    Minor changes , port clean up like that transfer which appears that the aluminum is 10~20% smaller than the steel sleeve ... will always run better if matched up.

    I would only widen the first 30* of ex port opening and then blend it into the stock port width. Even if the blow down degrees are less than 30* , it will still help. Once the transfers open , a wide lower two thirds of the port will only make it easier to short circuit .

    Cali ... didn't you do the conversions back to older model EFI parts .. ??
    If I was to do a Yamaha, that's the way I would want to go ..

    Don't the Yamaha's use something like 800 psi of fuel / air pressure .. ? Or the pumps will make that and are regulated down from there .. ?
    If so, thats a lot of wiggle room , to get fuel into the chamber.

    The poor 300xs pumps 105 on a gauge , and the air side of the fuel system puts out 110 psi at best. Clip the heads on one of those , and it will push the fuel back into the tank. Same thing when the air pump gets weak or rips the tracker valve diagram .. lean city / squeak ..

    The 3.3 liter Yamaha HPDI's utilize 2 low pressure fuel pumps, 1 50 psi pump in the vst. and a 1,000+ psi belt driven hp pump with 2 heads to feed the injectors. No air pressure. The injectors are driven by high voltage to handle the fuel pressure.

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