Head cooling on cylinder #5 - solutions?

[TimZ]

5) Non-aqueous coolant helps preventchanges when nucleate boiling occurs, and generally results in much higher operating temperatures across the board which may have other detrimental under-hood effects.

 

6) Water wetter seems to help in somemost cases,through decreasing surface tension of the coolant, very similar to a higher pressure radiator cap not so much in others.

 

No issues with the rest of this, but I'm thinking that these two might be a bit overstated. I've been using NPG-R coolant for some time now (essentially just after this thread was started), and I have not observed higher temperatures at all. As you are alluding to, the heat transfer is less efficient, but for me the combination of the diesel water pump and stock mechanical fan appear to be more than enough to keep the coolant temps at 195 (my t-stat's setpoint). I saw it creep up to maybe 215 stuck in traffic in the Woodward Dream Cruise, but that went away as soon as I got out of traffic.

 

Also, NPG-R boils at 400degF at 7psi system pressure so I would think this would change when nucleate boiling occurs by a LOT.

 

Finally, I'm one of the others that got struck through . I've never been as impressed as I thought I should be by Water Wetter. When I was having cooling problems, adding Water Wetter made no discernible difference in the performance of my cooling system. Not saying it doesn't do anything, but it's not a panacea.

Edited May 27, 2011 by TimZ

[cygnusx1]

Before everyone goes out to buy NPG have a read here too. I like to here both sides of a story. Not saying NPG is good or not. Just duing my due diligence.

 

http://www.rx7club.com/showthread.php?t=945513

 

 

 

 

 

[Zmanco]

I'm looking for the Maxima diesel water pump and part number 21010-17SY7 is coming up NLA. I think some of the car part chains are substituting the gas version which is of no interest to me as that's what I already have. 2 Questions:

 

1) Anyone know a source for the diesel pump?

 

2) What are the visual clues to the diesel pump to identify it as different from the gas? Anyone have pictures?

 

[Zmanco]

Looks like the diesel pumps are NLA... but I have another question.

 

I've done the mod to route coolant from cylinder 5 and 6 to the thermostat housing already. As I currently have the head off, I was thinking about plugging the internal coolant bypass as discussed here

 

Looking at Rossman's diagram, I was thinking that it might make sense to enlarge the bypass hole in the t-stat to avoid water pump cavitation before the t-stat opens. Seems like the downside would be that it would take longer for the engine to warm up.

 

 

I'm wondering how much of an improvement in cooling I could expect on the track as that's the only time I have any issues with cooling the engine. I realize there's probably no quantitative way to answer (unless someone did a before/after test), but I'm curious roughly how much coolant goes through the bypass vs. the radiator at higher revs (4-7k) that's typical on the track? If it's 10%, then I'd guess it's worthwhile. If it's 1-2%, then probably isn't worth the tradeoffs.

 

Curious to read thoughts on the pros and cons.

[Tony D]

The Bypass Loops (two 8~10 mm holes at the front of the head) provide enough bypass for the engine to properly recirculate at fast idle.

 

For a 'track use car' that should be more than enough to warm the engine in the pits before going on the track.

 

Frankly, most block those bypasses!

 

A way to get maximum cooling and still allow decent circulation from a fast pump is to take the heater connection at the back of the head, run it to the heater valve, and back to the inlet of the pump. Wide open during startup will let the engine war quickly to operating temperature, and provide PLENTY of flow recirculation (15mm hose!) for higher speed operation.

 

Once the engine warms, you simply slide the valve closed forcing ALL available pump output THROUGH the engine, instead of shunting it from the back of the engine back to the inlet of the pump.

 

This is why you don't want to 'loop' the heater core line when you remove the heater core! Sets up a terrible overheating potential!

[PMC raceengines]

Some pics of my new water system hope you like

[PR280z]

Looks promising!Let us know how it preforms.

[B. Whisky]

I like it. What about those holes adjacent to the manifold bolts?

Edited July 27, 2012 by B. Whisky

[TimZ]

I like it. What about those holes adjacent to the manifold bolts?

Alternate mounting bolt holes for the FI manifold.

 

That is some gorgeous work! You could just about market those if there was a sure-fire way to specify where the new holes in the head need to be drilled and tapped...

 

Am I hallucinating, or is the water passage bore size larger at the rear of the head?

Edited July 27, 2012 by TimZ

[PMC raceengines]

NO there all the same size , as for selling them id have to do the hole head as there is lots of welding and other work ,the hole side of the head is flat. And i drilled all the flashing between the ports, theres lots of work in it but it works we are well over 370hp now at 6000 , this engine also has new valve position canted and moved 2mm away from the bore , she ant no normal p90 hahah

[RB26powered74zcar]

Amazing workmanship PMC!

[New 2 z]

I read through the whole thread! wow amazing work guys. I dont have a L28 yet, I am a VG owner, and as a VG30 owner we have quite a bit different water pumps that can change flow how much flow etc etc.

 

I did some research on the L28 pumps and found some interesting stuff.

 

 

 

 

Thats all i could really get but for the VG there is like 4 or 5 different pumps. none are performance related but im sure different flow characteristics and of the such.

Edited November 25, 2012 by New 2 z

[240zphilly]

PMC that's a really clean setup, looks very professional. 

[Koryu]

Jeffp, is there anyway we can get the diminesions from 2-6 where to drill? I heard you knew within thousands of an inch. Im thinking about doing 2-6 and connecting them to a common tube then run that out towards the radiator. Im not gonna guess where to drill and by the pics I cant really tell exactly where to drill. If I can drill them at the same horizontal plane, that will make my install much cleaner. By the way I am kind of mirroring your build.

[osirus9]

Hey, I'm bumping this bad boy up from the grave with a few questions for people who have done this.

 

So I've read this entire thread, and I will be going ahead and doing this mod when I rebuild my engine and go turbo. I don't have any issues keeping my temps under control now even on super hot autocross days, or stuck in traffic in 95+ weather, so I can only assume my cooling system is up to snuff. I am going to get a higher pressure radiator cap, add some water wetter, and do this mod, which I gather will be sufficient to safely keep my engine happy at around 350hp which is where I hope to be. I also understand that this mod doesn't really cool the engine down more, but instead evens out the flow so there is less stagnant water in the rear of the head, thus helping to prevent premature detonation in those cylinders due to boiling steam pockets.

 

Now, I've heard people running higher pressure caps, between 18-30#, what kind of pressure cap would be a good idea for my pretty common setup? I'm guessing 18 would be fine for me, but what are the risks of running a higher pressure cap? How high can you run the pressure without damaging oem-style coolant hoses?

 

I've also seen some pictures of people's setups and it looked to me like KTM ran his 5-6 bypass lines into where the heater hose attaches near the lower rad hose. Forgive me, but this is the inlet of the water pump right? How does bypassing the radiator help cool the engine?

I would think you would want to route the coolant around to the front of the engine to the lower thermostat housing, but I have not seen a picture showing how people have routed hoses to that area. I suppose you could just run a line across the top of the intake manifold by the injectors? It looks like PCM raceengines was doing this, but his setup was incomplete at the time. Would this be a superior arrangement?

 

Also, the talk of the internal bypass... if you routed your 5/6 bypass to the lower thermostat housing, would you be able to block off this internal bypass without risking cavitation?

 

Again, apologies, I read the whole thing but I'm no fluid dynamics engineer, so much of it (especially Tony Ds posts haha) went over my head, although the summaries helped a lot, I just want to clarify a few points before I do something stupid.

[ktm]

It is the inlet to the water pump.  Tony D and I talked about where I should route the bypass and the inlet to the water pump is the easiest and cleanest location for a street car.  Keep in mind that I was not doing it for cooling purposes per se, but to get the hot water that was stagnating at the back of the head out.  I kept blowing head gaskets and every single time it was between #5 and #6.  After the mod I would blow periodically them but they would be between #3 and #4 or #4 and #5.

 

The bypass does not flow a significant quantify of coolant so by-passing the radiator was not an issue and I never saw an increase in the overall operating temperature of the car.  Again, it was just to get the water moving from the back of the head.

Edited October 6, 2013 by ktm

[osirus9]

OK, that makes sense, so if you still had a heater would it be safe to just route the coolant into the coolant line that runs along the passenger side of the engine to the pump inlet? Being that it is the exit of the heater shouldn't disrupt its function even if the heater is on or off correct? And for that matter, would it make sense to route the bypass to the heater core inlet? That way the coolant would be cooled a little if the heater was on, but where would it go if the heater was off.. back into the head? Or is that idea just retarded.

Edited October 6, 2013 by osirus9

[blue72]

After reading through this whole thread again, I've formulated the tentative plan for the cooling system on my turbo motor build.

 

 

I originally started making this diagram, then got distracted and made one for each of the stock cooling systems too. They're over here: L6 Cooling System Diagrams

 

Now, this diagram bars any special AMOT housings or cool adaptations to the thermostat housing itself. It'd be something I could do on my own without having to machine anything. Returning the coolant back to the stock thermostat housing would be a good way to go but I couldn't see a way to to it without custom parts.

 

The coolant log that the #2 - #6 lines (rear two -6 AN and front three -4 AN) run into would be 1.25†aluminum pipe that is capped at one end and hooked up to a standard radiator hose on the other. It'd be relatively easy to fabricate, requiring only some welding of the cap and AN fittings. The thermostat itself gets relocated after the radiator hose tee fitting. With the internal bypass blocked, one decent size external bypass line still exists to help prevent cavitation before the thermostat opens. It also happens to function as the turbo cooling line. I'm keeping a heater in the diagram because a defrost is required by state law here.

[HowlerMonkey]

Leave the exit at the back of the cylinder head connected to the heater core and parallel the core with a small cooler that's located up front of the car.

 

Sure, you will have two extra lines on the right side of the engine going forward but there really isn't anything else occupying all that empty space anyway.

 

The heater still works and you alleviate the problem of introducing hot coolant back to the water pump inlet.

[HowlerMonkey]

I've made an observation when swapping heads.......

 

One head I have came off an engine that possibly went 5 years on straight water. (It took a very long time to get the coolant clear)

 

This head runs without any sort of heat issues on extended high power pulls while all of my other pristine heads start to run hot.

 

I'm wondering if the thin casting flash has corroded away?