Coolant Boost Pumps

[Mechie3]

I was talking with Bob tonight and he shared his thoughts on some of the engine failures. It was sort of discussed in someones build thread, but I can't find it now. The coolant has several ways to go when exiting the pump. All of those paths are essentially the same except for the path to and from the radiator. One of Bob's theories (and it made sense to me) was the with the addition of the corrugated tubing, the extended length, that additional bends, and the additional ups and downs of the 818 radiator system that flow through the radiator is likely severely reduced as flow is instead pushed through the other channels and the coolant has the chance to become steam and cause engine problems. A picture was posted of the FFR car using an inline booster pump.

I use an electric booster on my F500. The engine is from a snowmobile and uses a single radiator in stock config. The motor requires quite a bit of cooling as it is raced in 90F weather when it was designed to run in freezing temperatures. To combat this, we run two radiators in parallel. To help flow I use a small electric bosch water pump.

Is this required? I don't know. What we really need is the ability to datalog a car with sensors pre intercooler, post intercooler, and sensors in the block for coolant and in the line going to and form the radiator. Until someone does that I'm going to assume that an inline pump can't hurt. Does anyone have recommendations. I'm seeing everything from the standard AWIC pumps, to $400 mezier and steward pumps.

[Bob_n_Cincy]

Hey Craig,
Thanks for your hospitality tonight. It was great to share ideas.
Bob

[Harley818]

Hi Mechie and Bob ,

I agree that alot of us are worried about the potential cooling problems.
I am considering AWIC just because I don't know the problem, and AWIC will probably solve it... but its expensive.

Metalmaker and others have had problems.
Is it AWIC related? is it coolant flow and temp related? what is the problem? Doing a datalog of a completed car is important to the basic configuration we are all building. If we know there is a problem, we can design an build to suit. If we don't know what the problem is, we are all taking shots in the dark.

Once we know what the issue is, we can all add AWIC, or coolant pump or whatever...... We need to know what the problem is.
Is there someone who has basic 818 set up like FFR manual that is willing to document temps and other data?

[Mechie3]

Bob,
It's always good to chat and share ideas. The best ideas often come through collaboration.

Harley,
You are 100% correct that we don't fully know what the problem is. Lot's of theories regarding intake charge temps (though a few cars with AWIC have had issues) though without data, no one knows for sure. FFR had issues with cars puking coolant out the overflow which is indicative of a cooling problem.

My line of thought is that the most expensive boost pump I've seen was $400, lots in the $200 range. A factory shortblock is $1800, new oil cooler is $250, gasket are $300. Ooof. FFR has blown a few motors, Brando blew a motor, or two, metalmaker blew a motor, I thought someone else did too. I'd rather spend $200 I don't need to potentially save ~$2500 + lots of labor time. Now, I'm not ready to dump $3k in to a dry sump system just because, but $200 seems worth it.

Until someone has the ability to datalog and we actually find out I'd rather play it semi safe.

[RM1SepEx]

Good idea to data log, how hard can it be to add sensors to data log for water temp in and out of the motor and air inlet per and post IC? How many are already there?

[Mechie3]

There is 1 sensor located on the aluminum crossover pipe under the manifold. Adding sensors is easy enough with the hardline adpaters. You just need something to actually do the datalogging with.

[Santiago]

Good idea to data log, how hard can it be to add sensors to data log for water temp in and out of the motor and air inlet per and post IC? How many are already there?

Well, the most obvious answer is: FACTORY FIVE

C'mon, I know this is a kit car, and I know we're all "builders" but this seems like the sort of thing the manufacturer should be diligently working on. FFR has got far more resources, equipment, and experience than just about any of us. Their mules are already carrying data-logging capable dashes (on the R-cars), and they've already had engine woes, so I think it reasonable that they should be taking the lead on this inquiry.

This is a pretty serious matter that goes to the core of the car's reliability...and ultimately its fledgling reputation. One guy blowing an engine is nothing new. A few of the first guys to complete the kit doing it, that's another thing. FFR, please put somebody on this and let us know what is (or has been) found.

In the meantime, I'm sure some other folks will start to look into it, but we would be better off if a couple folks could do it.

Best,
-j

[Mechie3]

^^ We had a very similar conversation last night. If the issue is oiling and the solution is a $3k dry sump, that's a huge market turn off. If the issue is an AWIC and it's $600 to build it yourself and $1400 to buy a kit, that's still an issue but depending on your fab resources is manageable, If the issue is coolant and it's a $200 pump? Meh, not a big deal. Problem is, until we figure out what it is it could be any, or all three, and then it starts to become an issue for the kit.

I just reread the UTCC thread from 2014. The red car had cooling issues at limerock (supposedly bypassed hoses), then had issues on the first timed session that was attributed to a bad radiator cap. They went out again and had the same issue with water from the front spraying and determined it was a headgasket. They then took the bluecar out and it had issues with the cap on the coolant tank and they attributed that to just a loose cap. I haven't seen that many issues with Subaru radiator caps going bad in my 8 years in the Subie world. At VIR they blew up both cars (one overboosted, another lost coolant through the banjo bolt and it lost compression). Issues with cooling seem to pop up often and it makes me wonder if there isn't something else to blame aside from the easy target of "we just had a loose cap, no problems here". I'm not road racing mine (not at first) so I'm not terribly concerned, but after having rebuilt many motors I don't have the desire or time to rebuild more. Still, I want the car reliable.

[RM1SepEx]

I dramatically changed my build schedule and philosophy due to the multiple booms... I've addressed the oiling issues with an sti pan etc and will run more oil, my side mount IC should fix the intake temp issues. If I was to road race a dry sump would be an excellent idea since the inherent design of a flat four is really an issue with high cornering loads. I would not road race a flat four w/o a dry sump. For short duration high lateral G forces in autocross and on the street we should be OK.

Cooling issues too? I don't see where we should have problems due to the design there. The long tubes are essentially more radiator, unless it just can't keep up with the engine heat. Smooth coolant tubes should decrease flow losses but it seems like FFR and others have extensive experience using these types of tubes in such an application. Coolant flow isn't high volume or pressure so losses shouldn't be significant.

[Mechie3]

I don't know if there are or aren't, but for $200, I don't see a reason not to put a pump in especially if FFR just did on their red car. Just wondering if anyone has experience with certain pumps vs others.

[Scargo]

I am worried about mass hysteria here. I and my friends have been tracking 350~400 WHP STis at the racetrack for years without too many failures. Some, with no failures for years! Heating was not an issue. Head gaskets were/stock pistons were. Overboost was.

As RM1SepEx said, the flex tubing just adds radiator. In my mind, as well. JeromeS13 has posted about pumps and gave links to testing of various water pumps, if you want to pursue that.

I think the Subaru motor is a sound platform. There are growing pains with this combo, no doubt. There are people rushing to get to the track with the 818 and little understanding of the motor and its idiosyncrasies. No... you don't have to have a dry sump.
Yes... you need a good bottom end and tight clearances for the oil pressure.
When you start pushing that old donor motor, all of these factors become more that a re-tread, 75K stock motor can take. Don't be silly.
My engine builder (a mechanical engineer that designs engines) said "Look up xxx and do some reading." I recommend that for those that wring their hands about the boxer motor.

[Wayne Presley]

We ran the prototypes for 4 solid days with no overheating issues, I've run 4 cars on the dyno for extended periods with no overheating. The last one was an 410 RWHP car that I could reach down and touch the coolant return line with my bare hand. All of them got to the thermostat temp and sat there.

[Jim Schenck]

Factory Five has never had any coolant system operation issues with our cars, that is why we haven't pursued any other avenues to try and change the cooling system. Of the three engine failures we had two of them already had an additional pump in the system, however the pump was never put there to help with keeping the car cool once its running, in both cars it was put in to speed up the air bleeding process if we have to do it at the track in a hurry. We ran the blue car and the red street car for many test sessions with no auxillary pump and nothing special at all with the cooling system and never once had an issue. At the 2013 UTCC it was over 105 degrees for the whole day and the blue car never once had a cooling issue and at the time it still had a completely stock system

The three engine failure we had were as follows:
Red race car engine number one: Blown head gasket due to pushing the limit of boost on a 175k mile engine. If you watch the video where that car blows coolant out of the rad cap the temp is just barely over 200 degrees, not enough to boil over but it blows the cap due to compression leaking past the gasket into the cooling system.

Red race car number two: Over boost, thrown rod. This car never got above 180 degrees even on the dyno.

Blue race car: Cooling hose to the turbo came undone at the banjo fitting and drained the entire system of coolant. Engine seized after running dry for about half a lap or maybe more. (I realize this is part of the cooling system but this is a preparation issue not an issue with the design)

Both the blue car and the sliver car (previously red) have an auxillary water pump to help bleed the system. In my opinion these are not worth carrying around the extra weight unless you will always be rushed during the coolant filling process.

[Mechie3]

I'm not doubting the the soundness of the boxer platform (I've driven them for years and rather like them)
Not trying to incite hysteria, just promote discussion as there have been several failures with very quick root cause analysis that were fast to dismiss any deeper problems such as "oh, it was just this" but then the failures continue after that was fixed. It makes me wonder if we aren't fixing symptoms and not true root cause. I'm just asking the 5 why's and wondering if there isn't a different issue potentially) such as the heads lifting and pushing coolant out http://www.iwsti.com/forums/2-5-lite...d-gaskets.html Edit: Jim just alluded to this on one of their cars

The flex tubing adds radiator, yes, but also adds turbulence, length, flow restriction. Have people with freshly rebuilt motors blown them up? Yes,. think everyone (including FFR) rushed to get to the track (it seems every high profile event they attend they blow up a car, or two, always in a different manner). The concern (rather I should say, area of interest, as the word concern seems to incite riot and not promote discussion) is the difference between the factory setup that has been road raced (like Scargo has) vs the setup in the 818. The very fact that many Subaru's have been raced without failures in general make me wonder why the 818 platform is experiencing trouble.

The system was designed to balance flow to all areas with the radiator being 6" from the pump/motor. In the 818 setup there are several more bends, ID changes, elevation changes, and length increase to the radiator circuit only. The factory pressure cap is rated for ~16psi. Simple online calculators with the assumptions of a 1.5" diameter coolant line, 16 ft of line, 100gpm, and assuming aluminum piping gives a pressure loss of ~5psi (meaning to flow the same as a stock Subaru arrangement, the system needs to provide 5psi more, or 1/3 more pressure). Add in the sudden expansion and contraction losses (FFR doesn't provide any smooth transition couplers) and the flow to the radiator is reduced even more while flow to other sections of the motor (ie, heater core circuit) are increased. Does the flex add radiator? Sure. But if it doesn't flow enough, it doesn't matter. Cooling capacity and the capability of the system to utilize the capacity are different.

Lets say all of that is moot. Fair enough. But I'd rather discuss it and then rule it out rather than ignore it preemptively. Without a running car or datalogging I can't really test the theory and can only rely on anecdotal evidence until someone that has datalogged or FFR chimes in.

Edit: Jim, where are you measuring coolant temperatures from? Also, now that we have input from FFR as to why they added the aux pump there's less reason to believe it is a problem, though I'll wait and let others be the guinea pigs for a while.

[Jim Schenck]

I don't agree at all that issues were quickly dismissed, in every failure we dissassembled the engine looking for any signs of additional failures or any possible causes. We also poured over the data from the Racepak comparing it with exact on track locations, trackside observations, driver feedback, and even in one case we called another driver on the track after the fact looking for info about what the car was doing when it passed him 30 seconds earlier.

In every case there was a clear explanation, and none of the three had any common symptoms or failures, and I can't state this enough times, none of them ever ran hot before the failure occured.

Bottom line is we pushed the limits of preparation time over the summer trying to get as much in as we could, and at the same time trying to push what has been done with the platform. Pushing the platform is something I still think benefits everyone, however doing it in private testing and not high profile events is certainly a better way to go.

[Mechie3]

Jim, I don't mean yours. There have been several failures of customer built cars. I'm not trying to PKI t fingers just starting a conversation where we can talk about potential weak points and how to address them. Its what any engineering firm does when they do a dfmea. They aren't pointing blame but are looking at potential failure modes, causes, effects, and then measuring the probability of those failures to see where to focus efforts.

[metalmaker12]

Hi Mechie and Bob ,

I agree that alot of us are worried about the potential cooling problems.
I am considering AWIC just because I don't know the problem, and AWIC will probably solve it... but its expensive.

Metalmaker and others have had problems.
Is it AWIC related? is it coolant flow and temp related? what is the problem? Doing a datalog of a completed car is important to the basic configuration we are all building. If we know there is a problem, we can design an build to suit. If we don't know what the problem is, we are all taking shots in the dark.

Once we know what the issue is, we can all add AWIC, or coolant pump or whatever...... We need to know what the problem is.
Is there someone who has basic 818 set up like FFR manual that is willing to document temps and other data?

In stock tmic and the 818s with windshield it has been proven you will need to run an awic to get safe intake air temps. The air to air can work, but major modifications to the body and ducting will be needed along with most likely losing the full winshield. The hardtop might fix this.


As far as the cooling system, I am really unsure if there is any real problem with it. My car experienced a coolant leak because the lower radiator hose made contact with steering rack boot and it created a leak. I was loosing coolant and sucking in air through serveral continuous runs and also my iats got way out of control. My coolant temp never got to the over heated state. But both head gaskets went and #4 piston ringlands has some failure. It is something that can happen on any car. I since moved to solid coolant lines, which move the line away from the rack more, and I also put larger spacers under the radiator for even better clearance. Once up and running I am going to log it often and check multiple spots of the charged air and coolant systems temps.There might be something that has been missed, but it could just be that the cars were put together quickly and simple stuff was missed.

I drove my 818 all around pushing it pretty good for 1,000 miles prior to autocross. So the problem is when you push it hard for sure. This spring I will be testing it out. I will keep you updated.

[D Clary]

I do not have a lot of Subaru experience, that been said I do have quite a bit of experience with racing and engines. The Subie engine is very sound with the possible exception of the "G" forces on the oiling system which is yet to be determined. Looking at the cooling system in my 818 I see absolutely no reason for any concern about heating. The main issue is greed and the ease of horsepower through the turbo. My policy is build a 400 horsepower motor and dial it back to 350. Les boost, less timing and richer mixture. My 4 cyl Mustang turbo runs 18 psi boost on pump gas. I have been running this way for three years of auto cross and track days. I use the megasquirt ecu. It has great timing and mixture control. I expect to have the same result with Waynes ECU and the Subie motor.

[Scargo]

A lot of this goes to what I was saying. We're building a kit car. There are lots of miss-steps, variables and little is proven other that we are wild and crazy guys who like to take the path less traveled.
Almost everything is anecdotal and there's not a common link, as I see it, other than many do not know the needs of a Subaru motor and start off with a tired, stock motor, push it hard and expect it to perform like a Porsche race motor.

Lifting of heads is classic and well documented. You need good gaskets and ARP studs. You need forged pistons. You need an 11mm oil pump. You need an oil cooler, a good intercooler and possibly water spray or AWIC. Some factory Subaru cars came with water mist for the intercooler and heat-soak is a well known problem. IMHO, having the AWIC anywhere over the hot engine is a bad idea.

[RM1SepEx]

increased boosting a used engine with unknown history is a crapshoot, higher g forces will cause oil to slosh around, very common issue for all motors, esp a boxer where the oil goes to the heads, easy to resolve. No one should do any racing (even autox) with a stock 02-05 wrx oil pan. Extra oil won't hurt. I'm crossing my fingers and hoping my luck is good with a 70,000 mile donor but if it blows in a week... I'll just have to accept it, smile and review options! JDM???

Flow rates are not enough to be a real issue in the water cooling, just be sure to burp well. It's easy to miss something building your own car... expensive OOPS will happen.

FFR's cars were raced, seriously stretched. When racing, **** happens!

[Mechie3]

My donor had 70k miles. It the motor had 20k since i last rebuilt it. It ran 21psi and ran well in the WRX. I just don't feel like rebuilding it for a fourth time.

[Santiago]

Thanks all for input on the discussion so far. If nothing else it reinforces the need to be very careful with the initial prep (no rushing) and to go over the car very thoroughly after several of the initial runs. Looks like developing a very thorough pre/post-run checklist is in order.

Best,
-j

[Turboguy]

In every case there was a clear explanation, and none of the three had any common symptoms or failures, and I can't state this enough times, none of them ever ran hot before the failure occured.

Out of curiosity, where in the system is coolant temperature sensor(s) located?

[JeromeS13]

Out of curiosity, where in the system is coolant temperature sensor(s) located?

It's in the upper crossover pipe, just before the coolant exits the engine and enters the upper radiator hose going to the radiator. This is when the coolant is at its hottest.

[metalmaker12]

Like a said up above I am going through the car with a detailed punch list and documented data before I ever really boost it.

My current punch list:
Psi check awic core again to 50psi
Go over all vacum lines again
Check all sensors and plugs are tighten to spec
Go over Aos routing and check for any problems
Check all torque specs on intake/ exhaust manifold, etc
Make sure oil press is up to 15-30psi to start.
Burp coolant system and once running check for hot/cold spots
Install awic and Run/bleed coolant
Install motul gearbox fluid
Check over all inlet, intake and IC tubing to check it's all tight and secure
Tune for larger injectors and mbc
Eliminate factory fuel pump controller for better amp control of aero 340 pump
Run a safe break in tune for like 1,000 miles, with break in oil for 50-80 miles than Rotella T6
Etc etc etc
I am missng something, but you get the idea.
Did I mention I am pretty much done, lol for all of you building, but this all does not take too long

[BrandonDrums]

Not owning one of these cars (but wanting to) I hope we get some stuff nailed down. I'm counting on you guys!

I would certainly say a booster water pump would make sense. That's a lot of piping to push a pull water through when the OEM water pump is designed for a setup where the radiator inlets and outlets are literally inches away from the engine.

Datalogging is one thing but just having some analog gauges would be better than nothing for getting water and intake temps at different locations. It would be like an aircraft where you just have tons of data on the dash. Could look cool and it most likely would be less expensive than getting a full computerized data logging setup that could compile that data alongside the ECU's logs. Air temp is hard to find but water temp ones can be had for $30 each.

[wildhorsesracing]

Having raced 600+ hp Mustangs and assorted BMWs over the years I had to deal with cooling issues often. One thing I did was to remove the center of the thermostat and simply put the "washer" that is left back in. It has always worked well to improve flow and cooling, has anyone done this with their 818?

[Jim Schenck]

Jerome is correct for our coolant temp sensor, some were in the crossover and others were in a tee coming off the line coming out of the crossover, where the coolant should be about as hot as it will get.

We also have checked the coolant temps at different spots with a gun while the car was on the dyno, just looking for hot or cold spots etc.. Not something you can do on the street but if you have an extra guy at a dyno session it is pretty easy.

Some of our cars have run with the thermostat gutted but the washer left in as a restriction, that is why the red car temps ran below 180 at the last event and on the dyno. Doing this was something we thought would help burp the air out of the system but it really didn't make much difference.

[Mechie3]

Thanks for the input Jim.

[Zach34]

One of Bob's theories (and it made sense to me) was the with the addition of the corrugated tubing, the extended length, that additional bends, and the additional ups and downs of the 818 radiator system that flow through the radiator is likely severely reduced as flow is instead pushed through the other channels and the coolant has the chance to become steam and cause engine problems.

I would certainly say a booster water pump would make sense. That's a lot of piping to push a pull water through when the OEM water pump is designed for a setup where the radiator inlets and outlets are literally inches away from the engine.

I'm not sure this is a correct line of thought. The whole flow restriction principle sounds like a compressible gas phenomenon - exhaust for example. We're all used to the concepts of flow restriction with exhaust systems - you want smooth bends, few of them, and a short-length system overall. That's because gas is compressible and we're trying to avoid pressure differentials throughout the exhaust tube. Water is not compressible. The coolant system is hydraulic. As long as there are no leaks, you get the same pressure at the end of a tube as you have at the beginning. In a closed-loop system, elevation changes don't matter because any hill that is climbed is also descended on the way back to the origin. There's probably some friction involved with the long corrugated tubes, but we're talking about water here - couldn't be THAT much friction.

I'm not an engineer, and I could be wrong, but I doubt the long corrugated tubes are affecting flow much.

[DodgyTim]

As long as there are no leaks, you get the same pressure at the end of a tube as you have at the beginning. In a closed-loop system, elevation changes don't matter because any hill that is climbed is also descended on the way back to the origin. There's probably some friction involved with the long corrugated tubes, but we're talking about water here - couldn't be THAT much friction.

Thats only true when the water is not flowing. Once it starts to flow there is a pressure difference from one end to the other. Diameter is the main factor. Simplistically friction loss in a length of pipe is

= (friction factor x length x velocity squared) / (2 x g x diameter)

when you make the pipe small,for a set flow rate the velocity goes up, and the friction loss goes way up.

The corrugated tube raises the friction factor. When you get into the maths of flow in corrugated pipes, it gets really complicated and theoretical really quickly

My gut feel is the thermostat opening would make a bigger difference than the corrugated tubing

[Junty]

Hey guys, My 818s has just returned from a week at the Dyno. It required a little more to get things going, as I started with a base MAP in the M800 Motec - which really has no targets. So the 818 off and on spent about 8hours running during the past 10 days, lots of stop starts and overnight cold starts to get everything just as it should be. Engine temperature is certainly the least of our problems down south with a 2.5L JDM engine. My donor engine is however near new only 14K miles before being moved to 818. The only modification to this engine was adding new fuel rails to get ride of all the aluminium spaghetti that these 2012 stock engines come with, and completely removing all the TGV valve assemble (allowing more inlet flow). Running at a very conservative 13PSI I've ended up with a tune that quickly pulled to 345 WHP and 460ft pb torque.
Feedback from the tuner:- Engine temperature and cooling system is perfect, engine gets up t temp, thermostat opens and remains at constant perfect temperature. From my limited experience fans on a dyno can contribute to slightly less airflow than open air driving. So I'm very confident with cooling system.
The tuners did try running a little higher boost - however the inlet air-temp (top mount IC) did climb and with increased boost lead to early (slight) engine detination.
As we should all appreciate - air temperature as it increases, and you increase boost = a whole lot less O2 getting into engine and detination (big contributor to engine failure) starts.
I have some excellent numbers, with very conservative boost on standard pump gas. I'm going to run it this way for a long while before eventually adding AWIC before any more boost.
This entire discussion leads me towards wanting to know all the differences between USA and JDM Subarus? Why does a JDM engine go so well?

[Scargo]

Water pump, Subaru PN 21111AA026 is closed vs the typical open pinwheel looking one. It is supposed to be better. There are expensive, supposedly tweaked "high performance versions of it, too.
sub_21111aa026_6_sd.jpgbetter VS OK? middle_1.JPG

While I'm at it, I have done passage matching on my EJ 257, though I cant report what, if any, effect it has had. I haven't run it yet. Let's just say that if you line up the head gasket on the head and also on the case you will see that there is room for improvement, enlarging and smoothing (at least on mine).

[metalmaker12]

And the heads are way better stock, bigger ports, better parts. Did I mention the engines are pretty much blueprinted and the tolerances are just spot on compaired to the US stuff. Guess they want the best for themselves. Kinda why I used one.

[metalmaker12]

Hey guys, My 818s has just returned from a week at the Dyno. It required a little more to get things going, as I started with a base MAP in the M800 Motec - which really has no targets. So the 818 off and on spent about 8hours running during the past 10 days, lots of stop starts and overnight cold starts to get everything just as it should be. Engine temperature is certainly the least of our problems down south with a 2.5L JDM engine. My donor engine is however near new only 14K miles before being moved to 818. The only modification to this engine was adding new fuel rails to get ride of all the aluminium spaghetti that these 2012 stock engines come with, and completely removing all the TGV valve assemble (allowing more inlet flow). Running at a very conservative 13PSI I've ended up with a tune that quickly pulled to 345 WHP and 460ft pb torque.
Feedback from the tuner:- Engine temperature and cooling system is perfect, engine gets up t temp, thermostat opens and remains at constant perfect temperature. From my limited experience fans on a dyno can contribute to slightly less airflow than open air driving. So I'm very confident with cooling system.
The tuners did try running a little higher boost - however the inlet air-temp (top mount IC) did climb and with increased boost lead to early (slight) engine detination.
As we should all appreciate - air temperature as it increases, and you increase boost = a whole lot less O2 getting into engine and detination (big contributor to engine failure) starts.
I have some excellent numbers, with very conservative boost on standard pump gas. I'm going to run it this way for a long while before eventually adding AWIC before any more boost.
This entire discussion leads me towards wanting to know all the differences between USA and JDM Subarus? Why does a JDM engine go so well?

460 wheel torque @ 13 psi??? I am a bit shaky on that. Show sheets!!
What's your setup, turbo injectors etc

[Hindsight]

Agree.... Even on ethanol that seems quite high. Would be very interested to hear more about the setup.

[Jaime]

345/460 means that the torque peak is well below 5250rpm. That sounds like either an undersized turbo or a very long stroke. Neither sounds EJ20-ish.

[Wayne Presley]

Sounds like he's running more boost down low and then tapering it down at higher RPM.

[C.Plavan]

I'm not too concerned with the cooling system. I was worried about the other things (TMIC, Dry Sump). I'll know in less than 2 weeks when I test the 818R on the track. It's sad when my buddies and I are already joking about blowing a motor. So hopefully, none of that will happen and I will have good things to report after some hard driving.

[BrandonDrums]

I'm not sure this is a correct line of thought. The whole flow restriction principle sounds like a compressible gas phenomenon - exhaust for example. We're all used to the concepts of flow restriction with exhaust systems - you want smooth bends, few of them, and a short-length system overall. That's because gas is compressible and we're trying to avoid pressure differentials throughout the exhaust tube. Water is not compressible. The coolant system is hydraulic. As long as there are no leaks, you get the same pressure at the end of a tube as you have at the beginning. In a closed-loop system, elevation changes don't matter because any hill that is climbed is also descended on the way back to the origin. There's probably some friction involved with the long corrugated tubes, but we're talking about water here - couldn't be THAT much friction.

I'm not an engineer, and I could be wrong, but I doubt the long corrugated tubes are affecting flow much.

Thats only true when the water is not flowing. Once it starts to flow there is a pressure difference from one end to the other. Diameter is the main factor. Simplistically friction loss in a length of pipe is

= (friction factor x length x velocity squared) / (2 x g x diameter)

when you make the pipe small,for a set flow rate the velocity goes up, and the friction loss goes way up.

The corrugated tube raises the friction factor. When you get into the maths of flow in corrugated pipes, it gets really complicated and theoretical really quickly

My gut feel is the thermostat opening would make a bigger difference than the corrugated tubing

Also, heat differentials can cause small pressure changes in a fluid. Fluids aren't easily compressed but that's not to say that they don't expand under heat like everything else. Not to mention that corrugated piping laid parallel to the ground leaves a LOT of places for bubbles to get trapped. It seems you'd have to burp the system with the corrugated pipes standing vertically to ensure everything is worked through when standing still.

Perhaps it makes sense to add a small but tall coolant reservoir in front of the engine with a vented cap. Not unlike the turbo coolant reservoir. Just having a high point at the end of the tract before entering the engine could solve a lot of vapor issues as well as act as a coolant 'surge tank' of sorts to ensure coolant flow if g-forces or changes in pressure interrupt flow for any reason. It would have to be either baffled or have staggered inlet/outlet points of course to allow the bubbles to rise under high flow but that doesn't seem to complicated.

Not that flow would be interrupted but seems like a simple stop gap measure to deal with one or two potential issues.