Thanks for the video Luke, I am a Subaru enthusiast and I try to do everything (when possible) by my self on my Subaru. I'm a Software Engineer and don't have any background related to cars/motorsport and almost everything that I learned came from YT. I'm so glad that people like you are sharing such a priceless content like this. Thanks for the amazing job!!!
I just ordered a reverse coolant mod and Koyo radiator to make my engine last. I also already installed an air oil separator. Thanks for your videos, they really helped me with my 2019 STI.
Great deep dive! Wonder if we can one day wrangle a ton of used heads for flow testing/cross-sectional area. The b25 and d25 heads are definitely ones I want to compare haha
Great series of vids on this topic that I was recently looking into since my final tune will happen on my hybrid build next week!! I NEED part 4 soon!!! 🤪
This you illustrated pretty well with an open deck block. Think about the different flow characteristics with a semi-closed ej257 or even a modified closed deck block like some aftermarket offerings. This would make the cooling problem a little worse.
Great thought provoking comment - thank you! I Love it. Yep, lots going on here and you are right about far more restrictions with a closed-deck block. Basically, with those additional restrictions, it will slow down the flow rate and the total volume moving through the heads. Is this a bad thing? If it leads to overheating, yes. But slowing down the flow will help with respect to that preferential flow around cyl #2. ie this would lead to better flow around cyl #4. Very interesting trade off and without real data, hard to know what the net impact is. I’ll be thinking about this and I’m considering some ways to test it and gather some actually analytical data. Cheers! Thanks!
Hm... I get you thougts. But I'm not so sure about that, since the passages in the head and the gasket are the main restrictions and most CDB conversions are not closed more than up to this degree. So, in theory, it should flow about the same?
i'm pretty sure if its overheating cylinder 4 then the coolant is simply to hot, the pump is pretty strong flowing especially at higher rpms... I find it hard to believe there is a low flowing area causing this, most likely the engines just tend to heat up more on that side and using a lower engine bay temp/ exhaust wrap and or lower temp thermostat or making sure its actually opening at the correct temp is more important, also can drill a hole in it so its a more steady transition, the fluid should be easy to measure with thermal imaging this problem of engine damage occurs when the coolant is more stagnate and not cycling as much when the thermostat is not open all the way.. very common for them to not function correct and should be replaced fairly often i have tested a few in boiling water and they don't open until its much hotter than it should be and some aftermarket ones don't have as large an opening and some have NO weeping hole, leaves and dirt and oxidization quickly reduce the radiators cooling compacity even pressure washing it will bend all the fins over, WOW WOW the factory thermostat is freaking 203c should probly be about 170C to 190C range pretty sad they engineer this stuff to fail like some weird experiment by aliens
But I thought there was no coolant flow in the middle of the cylinders as it's blocked by casting from top to bottom? Also people say about closed / semi closed decks, but these are only closed at the top, not all the way to the bottom.
I know this is an old video, hoping someone will help me out here. Water comes into the head from the manifold, then exits into the block as per video..(???) *This is correct??????????????????* I couldn't figure out where the water exited the head . Since the manifold carries water AND fuel, this is going to be tricky. (Mine is an EA82) Great video, thanks for sharing!!
Has there been an actual test like tapping a temp sensor into the block near cyl#4 to record temps before and after doing this mod? Just curious. It does make sense what you're showing here so I'd still consider one of the kits or make one.
IIRC, and I've been neglecting looking into this, but due to the turbo on that side and the coolant lines running to it, this is taken care of. On some twin turbo Subaru's, there's a Subaru part that allows coolant to flow from cylinder 4 to the turbo on the left side of the engine. This part is like $10. Buy your own coolant hose and you can DIY your own reverse coolant kit for a fraction of the cost.
You may get some benefit from it, but I'm not sure how much on an NA, if any at all. Because boosted cars tend to run higher cylinder temps, there would be a greater benefit on force induction than NA. As for thread, for some reason I couldn't find that info.
Thanks for the video Luke, I am a Subaru enthusiast and I try to do everything (when possible) by my self on my Subaru. I'm a Software Engineer and don't have any background related to cars/motorsport and almost everything that I learned came from YT. I'm so glad that people like you are sharing such a priceless content like this. Thanks for the amazing job!!!
Cool = go with the flow - thank you i did the number 4 by-pass - on my new virgin block - really noticed a change ! blessings !
About 900x more interesting than anything Dom had posted about this very mod
That was great, especially the "3D" representation at the end.
I just ordered a reverse coolant mod and Koyo radiator to make my engine last. I also already installed an air oil separator. Thanks for your videos, they really helped me with my 2019 STI.
👍
Still got it? How’s she going?
Great deep dive! Wonder if we can one day wrangle a ton of used heads for flow testing/cross-sectional area. The b25 and d25 heads are definitely ones I want to compare haha
Great series of vids on this topic that I was recently looking into since my final tune will happen on my hybrid build next week!!
I NEED part 4 soon!!! 🤪
Wow thanks for all the effort. I watched all 3 videos and they were very well done!
Thanks! Labor of love deal for sure.
This you illustrated pretty well with an open deck block. Think about the different flow characteristics with a semi-closed ej257 or even a modified closed deck block like some aftermarket offerings. This would make the cooling problem a little worse.
Great thought provoking comment - thank you! I Love it. Yep, lots going on here and you are right about far more restrictions with a closed-deck block. Basically, with those additional restrictions, it will slow down the flow rate and the total volume moving through the heads. Is this a bad thing? If it leads to overheating, yes. But slowing down the flow will help with respect to that preferential flow around cyl #2. ie this would lead to better flow around cyl #4. Very interesting trade off and without real data, hard to know what the net impact is.
I’ll be thinking about this and I’m considering some ways to test it and gather some actually analytical data. Cheers! Thanks!
Hm... I get you thougts. But I'm not so sure about that, since the passages in the head and the gasket are the main restrictions and most CDB conversions are not closed more than up to this degree. So, in theory, it should flow about the same?
i'm pretty sure if its overheating cylinder 4 then the coolant is simply to hot, the pump is pretty strong flowing especially at higher rpms... I find it hard to believe there is a low flowing area causing this, most likely the engines just tend to heat up more on that side and using a lower engine bay temp/ exhaust wrap and or lower temp thermostat or making sure its actually opening at the correct temp is more important, also can drill a hole in it so its a more steady transition, the fluid should be easy to measure with thermal imaging this problem of engine damage occurs when the coolant is more stagnate and not cycling as much when the thermostat is not open all the way.. very common for them to not function correct and should be replaced fairly often i have tested a few in boiling water and they don't open until its much hotter than it should be and some aftermarket ones don't have as large an opening and some have NO weeping hole, leaves and dirt and oxidization quickly reduce the radiators cooling compacity even pressure washing it will bend all the fins over, WOW WOW the factory thermostat is freaking 203c should probly be about 170C to 190C range pretty sad they engineer this stuff to fail like some weird experiment by aliens
Your channel was the channel that I have been looking for! New sub from me 😁
But I thought there was no coolant flow in the middle of the cylinders as it's blocked by casting from top to bottom? Also people say about closed / semi closed decks, but these are only closed at the top, not all the way to the bottom.
no flow?
I know this is an old video, hoping someone will help me out here.
Water comes into the head from the manifold, then exits into the block as per video..(???)
*This is correct??????????????????*
I couldn't figure out where the water exited the head .
Since the manifold carries water AND fuel, this is going to be tricky. (Mine is an EA82)
Great video, thanks for sharing!!
Has there been an actual test like tapping a temp sensor into the block near cyl#4 to record temps before and after doing this mod? Just curious. It does make sense what you're showing here so I'd still consider one of the kits or make one.
So what about cylinder #3? Wouldn’t it have the same problem? How does the heater affect this mod?
IIRC, and I've been neglecting looking into this, but due to the turbo on that side and the coolant lines running to it, this is taken care of. On some twin turbo Subaru's, there's a Subaru part that allows coolant to flow from cylinder 4 to the turbo on the left side of the engine. This part is like $10. Buy your own coolant hose and you can DIY your own reverse coolant kit for a fraction of the cost.
I’m running an na ej25 in an 07 Forester, would this mod still benefit me?
What thread is the plug in the head?
You may get some benefit from it, but I'm not sure how much on an NA, if any at all. Because boosted cars tend to run higher cylinder temps, there would be a greater benefit on force induction than NA. As for thread, for some reason I couldn't find that info.
@@vipercrazy Do you know the part number of this part?
Are you going to mod the head gaskets and try it?
i just used factory STI head gaskets with ARP head studs !
@ronnieboucherthecrystalcraftsm been there done that, but that won't increase coolant flow. That's what I was talking about.