Engine temperature tests and results

[ozconnection]

Hey Pete, yes perhaps changes to the heads were more than skin deep over the years and its more than just chamber shape that contributes to detonation resistance.

 

Gotta get some piccys of that stuff on here, like what you showed me before of your cut up head. Good stuff mate.

[rossman]

Have you considered using a waterless coolant replacement like Evans Waterless Coolant ( http://www.evanscooling.com/assets/pdfs/HighPerformanceCoolantFlyer.pdf )? I am considering NPGR for my turbo project.

[ktm]

A waterless coolant is not the solution. Water is the best coolant, all of the other products simply have a higher boiling point.

[Tony D]

Evans Specific Heat rating is (as I recall) somewhere around .81 or thereabouts, pure water is 1.0, 50/50 EG is somewhere around .7, pure EG is lower than that.

 

KTM is correct, the higher boiling points mean you can run the engine hotter without possibility of spot-boiling and the resultant insulation characteristics of steam (grape ape racing page for better explanation).

 

Every coolant out there commercially available for home use (lets not get into military exotics...) has worse heat transfer than water. But a significantly higher boiling point. So the tradeoff is you run hotter, but consistently. As opposed to a runaway situation where the engine keeps getting hotter and hotter till you reach system input/rejection equilibrium.

[510six]

On my setup a Davies Craig water pump is used as a "helper" pump, when in 6th gear on the freeway at about 70-75 mph (1700rpm) the coolant temp would rise. The electric helper pump solved this problem as well as being able to cool the motor down between drag race runs without running the motor. The car also runs consitantly cooler in stop and go traffic on hot days and it controlled by the AEM EMS to active at 185 *. I lost a fan belt once due to a bearing locking up the alternator, the car was able to make it 10 miles home due to the electric water pump.

 

As far as the timing issue goes, years ago when running a 82zx N/A distributor with a turbo motor and using a MSD boost timing master for retard an issue was found to be excessive side to side play affecting timing +/- 3*-5* . This was corrected by replacing the stock bushing with one made out of aerospace plastic . The scattered timing problem was solved and 36* of timing was possible off boost.

[TimZ]

At this point, yes, the thermofan and the water pump work together.

 

There is no temperature dependancy ATM.

 

I could get a water pump controller later on but what for?.......I'm thinking that whatever the stock setup does, (ie come on when the engine starts and turn off when the engine does) I can duplicate that easily enough.

 

I guess for a turbo engine, there'll be more of a reason to avoid heat soak. A turbo timer could be set up to run just the water pump and thermofans after engine shutdown for a period of time......that would be excellent if you had a water cooled turbo.

 

That works - I was concerned that you were going to shut off the pump with a thermostatic switch, which IMHO is not a good idea, although I've seen it suggested several times.

[TimZ]

A waterless coolant is not the solution. Water is the best coolant, all of the other products simply have a higher boiling point.

 

Only if you can keep it from spot-boiling, which appears to be difficult on an l-series head. If there is a vapor barrier between the fluid and the head it doesn't matter what its specific heat is.

 

I've been using the Evans NPG-R for two years now, and it works really well.

[rossman]

I'm definitely no expert here but I think the L series "hyper sensitivity to detonation" (as BRAAP puts it) theory goes something like the following. For whatever reason (poor/marginally designed/manufactured or just out dated) Nissan L series heads develop localized pockets of stagnant coolant during operation. If or when nucleic (spot) boiling occurs in those pockets, the vapor can collect and form an insulating layer between the liquid coolant and the cylinder head walls. Vapor has very little thermal conductivity (compared to water, NPG, etc.) resulting in hot localized head temperatures. These hot localized head temperatures result in a head that is prone to detonation.

 

It appears that Evans NPG addresses the problem by providing a higher boiling point (the temperature at which liquid turns to vapor) and, according to their literature, "any locally generated vapor is immediately condensed back to liquid coolant avoiding the development of an insulating layer of vapor." This property of the coolant keeps the head walls wet allowing for much greater localized heat transfer as compared to a vapor layer.

 

I don't trust marketing hype so I am looking for some real world testing. TimZ is one data point favoring Evan's NPG. If I remember correctly his setup is pushing out some serious power which would significantly tax the old L6 cooling system.

 

So the tradeoff is you run hotter, but consistently. As opposed to a runaway situation where the engine keeps getting hotter and hotter till you reach system input/rejection equilibrium.

So do you think it's correct to say that a higher overall temperature in the head due to NPG's lower heat transfer is negligible assuming the cooling system has the heat rejection capacity to keep up?

 

Sorry ozconnection for kinda going off topic...

[TimZ]

So do you think it's correct to say that a higher overall temperature in the head due to NPG's lower heat transfer is negligible assuming the cooling system has the heat rejection capacity to keep up?

 

Sorry ozconnection for kinda going off topic...

 

Thing is - it doesn't run hotter. At all. In fact, my cooling system now works as well or better than it ever has. I am running the stock viscous clutch fan and the LD water pump, so that is probably helping a bit, but I now have far fewer problems with the coolant temps climbing above the 195 degree setpoint than I ever have.

[ozconnection]

On my setup a Davies Craig water pump is used as a "helper" pump, when in 6th gear on the freeway at about 70-75 mph (1700rpm) the coolant temp would rise. The electric helper pump solved this problem as well as being able to cool the motor down between drag race runs without running the motor. The car also runs consitantly cooler in stop and go traffic on hot days and it controlled by the AEM EMS to active at 185 *. I lost a fan belt once due to a bearing locking up the alternator, the car was able to make it 10 miles home due to the electric water pump.

 

As far as the timing issue goes, years ago when running a 82zx N/A distributor with a turbo motor and using a MSD boost timing master for retard an issue was found to be excessive side to side play affecting timing +/- 3*-5* . This was corrected by replacing the stock bushing with one made out of aerospace plastic . The scattered timing problem was solved and 36* of timing was possible off boost.

 

Yeah, I was looking at those as well and was considering using it to change the direction of the coolant flow into the back of the head. I can see that your efforts have worked quite well for you.

 

I've also got the MSD 6BTM, left over from the days when I ran a turbo setup in my Cedric. At the time, I found a similar thing to you, that there was excessive play with the drive spindle causing erratic timing.

I solved the problem by pinching the drive slot a little (and very carefully) at the end of the distributor. Then, when replaced, there was some preload applied to the drive spindle and the mesh with the crank was more snug, timing was perfectly stable after that.

 

Cheers for your insights.

 

I'm using the redline water wetter mixed with distilled water....did I notice a difference....nope, couldn't tell any difference at all. The buggar still pings.......it might work for some but where I'm looking for a solution to the problem, clearly this wasn't it.

[ktm]

Some of us modified the heads to address the stagnant cooling pockets. You can also run a different coolant solution such as Evans to help with the localized boiling.

 

I am not advocating on solution or another. I was incorrect in stating that a waterless coolant was not the solution. What I was trying to confer is that you need to identify the source of your temperature issues before deciding on an apparent fix. What is your engine build? CR ratio? Aluminum radiator? etc.

 

I am still sorting out my cooling issues too. I recently installed new gauges, an LD water pump and an Arizona Z car aluminum radiator. The 50 mile drives I've taken have shown me that I barely break 170 degrees when cruising (160 T-stat) on a 75 degree day; on colder days it is slightly over 160 degrees.

 

Your timing may be inappropriate for your build. I know you referenced BRAAPs post, but every car is different. Some like more timing, others less. Some like to run rich, others are happy leaner. Fueling differences between here and Oz may be a contributing factor. I learned the hard way that you can not take a blanket statement like BRAAP's and think that you are safe to apply it.

 

What I did not see is whether you verified timing at the higher RPMs. Sure, your idle timing may be ok but your mechanical advance may be off. What is your timing at 3000 rpms?

[Tony D]

This goes to the spot boiling tendency. What you get with Evans NPG is the same equivalent decrease in spot boiling tendency as you would get were you to run a 30 or 45psi radiator cap.

 

What you end up with is the thermal reserve of the radiator is reduced 20% due to the decreased heat transfer possibilities of the coolant.

 

Were you to run the same system with water and the higher pressure cap, you would not experience any reserve reduction. The reason you don't see any increase in the coolant temperature is that you have a radiator capable of rejecting the heat at the load point you are monitoring.

 

Run the engine at 100% power on a dyno for an hour, with each coolant...then tell me what your temperatures are.

 

JeffP was running pure Ethelyene Glycol, and did not go 'runaway' with his engine, but found the equilibrium point one day climbing a mountian grade at a constant boost situation. Because of the coolant used, no overboil was experienced, but it got hot. In the same situation, Evans would go about 10% longer due to better heat transfer than EG.

 

The radiator ultimate rejection will determine equilibrium point. It is set at X BTU's an hour. If you can transfer heat FROM the engine TO the radiator at 100%, and your heat input is below that rejection point, you will have stable low temperatures.

 

If you inject MORE heat than it's capable of rejecting, your heat will rise in the system to whatever equilibrium is obtainable.

 

Under boost, effective transfer is the FIRST problem. Evans helps with this in that it won't spot boil and insulate (but water can do the same thing with enough head blanket pressure.)

 

After effective heat transfer from the block to the fluid is obtained, rejection is the next step. That means radiator and flow through the respective circuits...

 

In all their testing, Electramotive never had a DNF due to cooling at power levels between 700 and 1000 HP.

 

They ran (as most racers are required to do) straight water and a high pressure cap, and some astounding flows through the engine due to coolant passage modification. They used a standard L-Series water pump (may have been LD pump...) and nothing supplemental to boost flow externally.

[kolonelklink87]

Hey Pete, yes perhaps changes to the heads were more than skin deep over the years and its more than just chamber shape that contributes to detonation resistance.

 

Gotta get some piccys of that stuff on here, like what you showed me before of your cut up head. Good stuff mate.

 

The plot thickens somewhat when considering all the different cast that are out there....

At home I have a 260z e88 such as is well reported on here.... this is the head that is sliced up as a porting guide. In addition to this I have two very late non-US efi e88's. Each of these has significant notable casting differences(yes, two separate casts of the late-model heads!)... I really have to sit down and catalog the differences between heads but that will have to wait untill my return from japan. Something that I did note whilst doing some porting on one of the heads the other day was there is a significant difference in the shape of the coolant passage above 5-6 intake/exaust and the later model lacked the large hex-plug access point that the earlier head possessed.

These are just incidental finds... I'm sure if i sit down and write a list of differences I will find others (I only had the 5-6 cutaways in my hand at that point).

 

It is possible that the cast was modified for EFI purposes.. I'll have to sit the e88 EFI down next to my other EFI head(p90) to investigate this.

Perhaps it is coincidence or perhaps nissan made some subtle changes in later models to attempt to correct the detonation issue *shrug*

Has anyone else out there noticed this? *Paging Tony D*

[ozconnection]

What I was trying to confer is that you need to identify the source of your temperature issues before deciding on an apparent fix. What is your engine build? CR ratio? Aluminum radiator? etc.

 

Your timing may be inappropriate for your build. I know you referenced BRAAPs post, but every car is different. Some like more timing, others less. Some like to run rich, others are happy leaner. Fueling differences between here and Oz may be a contributing factor. I learned the hard way that you can not take a blanket statement like BRAAP's and think that you are safe to apply it.

 

What I did not see is whether you verified timing at the higher RPMs. Sure, your idle timing may be ok but your mechanical advance may be off. What is your timing at 3000 rpms?

 

Valid points, especially about what you said about taking the advice from someone on the other side of the planet, hell even different hemispheres!! But at the end of the day it's worth giving it a shot, and maybe identify an alternate solution to a pesky problem L engines seem to have.

 

Until the other week when I started this experimentation, my cooling system was working perfectly. A recently overhauled 3 core radiator (2 core stock) with a system flush was the only addition because the old one was starting to weep. I've always used EG as a coolant material and mixed it up per manufacturers recommendations.

 

The fuel issue is an interesting one, I use the best (read highest) 98 RON octane fuel I can get from the bowsers. Unleaded premium of course but I don't add anything to it....maybe I should be adding that lead substitute stuff....I think that has some anti-knock properties IIRC. I don't want to go there if I don't have to though.

 

Otherwise stock N42/N42 L28. CR is 8.3 Timing has been verified by using my lovely Innova fully adjustable timing light. ATM my timing is set at 38 degrees total mechanical advance @ about 3500rpm's.

[BRAAP]

(E88' date=' N42, N47[/i']), have their optimum non octane limited spark advance in the 38-42 degree range.

 

"If you can't get 38 degrees total ignition advance above 3500 RPM at WOT, (N/A), with E-88, N42 or N47 head because it is rattling, you are leaving HP on the table."

 

..

Your timing may be inappropriate for your build. I know you referenced BRAAPs post, but every car is different. Some like more timing, others less. Some like to run rich, others are happy leaner. Fueling differences between here and Oz may be a contributing factor. I learned the hard way that you can not take a blanket statement like BRAAP's and think that you are safe to apply it.

 

 

Bo, you are absolutely correct in that every engine is different and every engines ideal timing curve, (talking N/A here), is going to be different. I listed a window of maximum total mechanical ignition advance above 3500 RPM for combinations such as ozconnetions, he is only trying attain the safer, lower end of that window, he’s not trying to achieve a blanket statement that might only work for 5-10% of those head/piston combo's.

 

For example, my '75 280-Z listed below is an extreme example of the upper end of that window that I wouldn't recommend to everyone as not all combinations, even ones similar to mine could run that much ignition advance, but that window of 38-42 degrees above 3500 RPM should be attainable by 95% of those combinations.

 

Car was a Daily driver, '75 280-Z, N/A L-28, 42 degrees total mechanical ignition advance that was all-in before 3000 RPM, (I think it was in by 2500 or so). 2800 lbs with driver and half tank, bone stock '75 short block with OE dished pistons, '78 N47 head with extensive valve unshrouding, stock '75 EFI, stock '78 cam, Z, 8:1-8.1:1 static C/R, ran 14.4 @ 97 MPH, 0-60MPH in 5.7, and delivered between 28 MPG with dual 2" exhaust, 30 MPG with dual 1 3/4", (performance was the same for both exhausts).

[MatMan]

...snip... I use the best (read highest) 98 RON octane fuel I can get from the bowsers. ...snip...

 

You are still getting detonation on 98??? I would pay an extra $.50/gal if I could get 98 in CA... Union 76 used to sell 100, but I haven't seen that since around '98.

 

Maybe a couple degrees less timing would help a bit....

[TimZ]

You are still getting detonation on 98??? I would pay an extra $.50/gal if I could get 98 in CA... Union 76 used to sell 100, but I haven't seen that since around '98.

 

Maybe a couple degrees less timing would help a bit....

Careful with the octane numbers - other countries may not use the same system that we do in the States - I think their 98 is more like our 92 or 93

[MatMan]

I apologize, I thought RON was RON wherever it was measured. Was this incorrect thinking?

[Tony D]

RON is RON, but the pump rating may be RON, MON, or R+M/2 as in most of the USA.

 

The standard in USA is R+M/2.

 

Outside the USA depending on where you are, it could be any of the above combinations. MON is really the most important as it's a physical check of the fuel in an actual knock engine. Honda used a fuel in F1 during the turbo years that met the MON standard of 104 or whatever it was at the time, but it's RON was close to 70! Exotic blend, but it ran great as long as charge temperature was above 140F...so it would atomize. It wouldn't run your street car... but in the USA if sold for motor fuel it would have had a rating of 104+70/2 = 86 or basically 'regular'... It's actual performance was equivalent to 104 when run in the engine as the engine was designed around the fuel...

[Ben]

I just thought I briefly say that this is a fascinating thread, and a very relevant discussion - along with the previously mentioned thread on the coolant flow improvement.

 

It is of particular interest to me as I too have been somewhat frustrated with the fact that I was having to run around 17deg under full-boost 98RON+ octane booster in my N42/N42 L28ET Z, while my RB25DET will happily run 22+deg all day on straight 98RON (with approx the same power output, a 'tiny' intercooler and more restrictive exhaust). All design improvements aside, I was sure that the old L could do a bit better (yes, I'm aware of the 'average' design traits of this combo specifically in a boosted application).

 

If nothing else, I will seriously consider; a) an LD pump, , 5&6 supplementary flow mods, and c) a 1.5-bar cap for my F54/P90 engine currently under construction.

 

Again, I for one appreciate the R&D going into this matter.