Dyno Testing Bolt-ons On The 4.0

[Rickyd]

Engine Masters did a video on cams being too small. They dynoed 3 cams with 250, 260 and 270 advertised duration. The 250 and 260 had nearly the same tq down low, but the 260 started to pull away as the rpm went up. Their assessment was that the smallest cam did not make more tq because the valve did not stay open long enough. The 270 gave up bottom end and predictably made more HP. I don't have a subscription any more to watch it so if someone has HULU feel free to correct me.

The analogy russ pottenger gave me when picking a stroker cam was small vs big block engines. The big block will need a larger cam to not fall on its face at higher rims.

I chose the smaller of the two cams he suggested and wish I'd gone larger. The added cubes and high compression would have really liked a modified 235 cam vs the 231 I used.jezza's dyno results with the 231 show it is more for a 4.0l

 

[Jezza]

There are a few things holding me back from a roller cam. One being the cost. They are not cheap, especially for us 2000+ guys that have to change to the older style cam stuff. The other being the billet core. In my experience they like to chew up distributer gears. I think they have a Melonized gear they sell that is supposed to work with it, but I want to see some longivity results first.

 

[GoldenGorilla]

Does not change the expensive part, but Newcomer has thrust plate cams for the later 4.0L setup so you don't have to switch over to a cam button and non-thrust plate for older ones. And melonized gears.

 

[Captain Phoenix]

The housing really does fit well under the hood.

I really want to know what hose and elbows you used.

 

[astjp2]

Are you asking why people are likely having cam bearing failures, or cam related failures in general?

If you're talking about cam related failures in general, I'd say it's multifaceted. (don't choke on that big word guys ) For the camshaft it's self, one big disadvantage of an I-6 or I-8 is the length. For the bearings, sometimes that comes to material selection, which can become a real issue when increasing spring pressure. Increased spring pressure is also a major issue for all flat tappet cams, not just inline engines. So back to that multifaceted issue, if someone puts together an engine with standard rebuilder grade or worse cam bearings, then wiggles in a higher lift cam and supporting 2x rated springs, well, something has to take the hits and soft bearings are first in line, probably followed by the cam/lifter interface.

Then there's surface finish and hardening issues, but that's well out of my ball field.

But don't take that as garage gospel, I'm just a special needs kid with internet access.

Well in some world of flat tappet cams, cast nitrided cam with tool steel lifters or steel cam with cast lifters. We are talking 8620 castings vs 4340/5140 steel, with a 1-2 degrees slope on the lobes to rotate the lifter in the bore

 

[GoldenGorilla]

So, from all of the magazine and dyno guys over the years (Engine Masters, Engine Builder, Hot Rod etc) they've more or less established a rule-of-thumb that dropping the fuel temp 10 degrees Freedom nets around a 1% increase in power, and visa-versa. Obviously there are limits, so taking fuel from boiling to freezing will not mimic supercharging. The general theory is that the colder atomized fuel cools the air charge.

Hey look, I found the Engine Masters episode covering fuel temp.

Hmmm, is it worth it to reprogram the JTEC+ PCM around a 180 thermostat?

Another episode looking at engine temps and power. In this one they ran the engine with hot coolant, and heated and chilled the plenum and figured out that cold fuel mattered to the intake and a cold head made more power because it created created a bigger pressure differential going into the combustion chamber resulting a slightly larger CFM. However they were running 135F coolant vs 208 coolant.

In winter driving I've seen my coolant temp hold constant at 190F. The thermostat opens at 194F as it should, but I get enough cooling through the Mopar radiator to see it hold at 190 running. The upper hose remains hot but the engine comes out of warm up and into the normal fuel and spark maps. I would assume the thermostat trims flow a little under this situation.

 

[BlueC]

Hmmm, is it worth it to reprogram the JTEC+ PCM around a 180 thermostat?

IDK. The manufacturers and hot rod/race guys seem to have settled in on running engines (coolant temps) in the 200-230 range as being the best. The OEMs like the hotter temps for emissions, efficiencies and boil-off capabilities of the hotter temps. The race guys (not drag) seem to say a hotter cylinder helps with burn rate/efficiency. I think @Steel City 06 (I may be mixing up who) has ventured down the thermal road and might have more knowledge on topic.

 

[srimes]

"Worth it" depends on what you're doing. If max power is the priority then yes, cooler is better. Even without a tune the 4.0 will make noticeably more power at 180 than 220.

If you aren't building a race car then OEM spec temps will give better longevity and mpg.

 

[Wildman]

PSA here is that you can't just swap thermostats. You've got to run a tune that is setup for the cooler thermostat. If you just change to a cooler one you're not doing anything.

 

[GoldenGorilla]

Might have been enough in a cooler thermostat for Jezza to hit his goal. But it also might have been enough to just test it someplace at sea level, but cooler and drier.

I've looked at all the coolant stuff before and agree that the 194F thermostat is the way to go for the long haul when the MFG built it that way. I'm a big believer in running the engine as clean as possible too, so this is something I'm not going to mess around with. It has been interesting to see the cooling struggle to hold temps at 194 in modestly cool (50-60F) weather lately. I was lucky to get one of the later Mopar radiators when I had to change it a few years back. While I don't love the plastic tanks for very long term reliability and will have to figure something out in 15 years, the evidence is clear that the radiator is cooling the system more than needed with temps in the 60s.

 

[BlueC]

PSA here is that you can't just swap thermostats. You've got to run a tune that is setup for the cooler thermostat. If you just change to a cooler one you're not doing anything.

Actually I think it's worse than that. If you just swap in a cooler thermostat into an OBDII emissions controlled vehicle, it will continue to run in "cold" mode running rich trying to reach temp, which will lead to flooding/fuel washing issues.

 

[Wildman]

Actually I think it's worse than that. If you just swap in a cooler thermostat into an OBDII emissions controlled vehicle, it will continue to run in "cold" mode running rich trying to reach temp, which will lead to flooding/fuel washing issues.

I don't remember what all the down sides are just remember it was a No-Go unless you tuned it also.

 

[Wildman]

Here's what AI says on the subject.

Running a colder thermostat without a proper ECU tune causes inefficiency, poor fuel economy, increased emissions, potential engine damage (moisture/acids in oil), and can trigger a "Check Engine" light because the engine stays cold too long for the computer to run optimally, leading to poor fuel atomization and incomplete combustion. While it might seem to help with overheating, it masks underlying issues and prevents the engine from reaching its designed, efficient operating temperature, requiring tuning and potentially a better radiator for true benefit.

Problems with Colder Thermostat Without Tuning

• Incomplete Combustion: Fuel doesn't vaporize effectively at lower temperatures, reducing power and efficiency.
• Moisture Buildup: Water and acids can accumulate in the oil because it doesn't get hot enough to burn off, leading to engine wear.
• Check Engine Light: The car's computer sees the engine staying cold and throws codes.
• Poor Heater Performance: Takes much longer to get warm air in the cabin.
• Masks Real Problems: Hides the real issue, which could be a bad fan, clogged radiator, or failing water pump, notes Summit Racing and YouTube.

 

[MikeE024]

Hmmm, is it worth it to reprogram the JTEC+ PCM around a 180 thermostat?

Another episode looking at engine temps and power. In this one they ran the engine with hot coolant, and heated and chilled the plenum and figured out that cold fuel mattered to the intake and a cold head made more power because it created created a bigger pressure differential going into the combustion chamber resulting a slightly larger CFM. However they were running 135F coolant vs 208 coolant.

In winter driving I've seen my coolant temp hold constant at 190F. The thermostat opens at 194F as it should, but I get enough cooling through the Mopar radiator to see it hold at 190 running. The upper hose remains hot but the engine comes out of warm up and into the normal fuel and spark maps. I would assume the thermostat trims flow a little under this situation.

They might not have touched on it or cared for their scope, but there is a GM study that showed ring wear increases as coolant temps decrease. Even 240* coolant temps resulted in more wear than 260* coolant temps.

I have since wondered if that's a reason why vehicles are in the higher range, but low enough to not cause other issues like blow head gaskets etc.

 

[GoldenGorilla]

Again - not advocating for this. I've read the same studies @MikeE024 is referring to and I want my engine to last just as long in the future as I've had it today. Although the 4.0L architecture is a bit of a dinosaur, it's been a long time since engines were designed around a 165F thermostat. And keep in mind - just because you put a 180F thermostat in the system - it doesn't mean it can or will actually hold at 180F if the radiator isn't able to cool sufficiently. If it's 115F outside, you're realistically going to see temps in the 200F-210F range, which isn't overheating.

If someone really did want to do it, I believe there are 2 tables in HPTuners you'd need to address for the JTEC/JTEC+ PCMs. If you don't, spark and fueling will be stuck in their warm up cycles doing bad things for efficiency.

 

[BlueC]

there is a GM study that showed ring wear increases as coolant temps decrease.

Is that the paper from around 2000. If so, I think that study also determined that something like 90% of wear happened while running "cold", like idling to warm up.

 

[Steel City 06]

IDK. The manufacturers and hot rod/race guys seem to have settled in on running engines (coolant temps) in the 200-230 range as being the best. The OEMs like the hotter temps for emissions, efficiencies and boil-off capabilities of the hotter temps. The race guys (not drag) seem to say a hotter cylinder helps with burn rate/efficiency. I think @Steel City 06 (I may be mixing up who) has ventured down the thermal road and might have more knowledge on topic.

Technically hotter engine temps = more efficient and also more power, at least until you reach the point of having to pull timing due to pre-ignition or detonation.

The reason is because less heat is lost to the cylinder walls and other internals when they are kept hotter. On the extreme end, it is theoretically possible to scavenge some of that heat back into mechanical energy by simply letting it get transferred back to the air and gasoline inside the cylinder which expands it a small amount.

Hotter temps also yield more complete combustion, which means more efficiency, better emissions, and in some cases more power.

 

[LJ owner]

"Worth it" depends on what you're doing. If max power is the priority then yes, cooler is better. Even without a tune the 4.0 will make noticeably more power at 180 than 220.

If you aren't building a race car then OEM spec temps will give better longevity and mpg.

Better mpg in a jeep?

 

[BlueC]

Better mpg in a jeep?

It's all relative. 12.5 mpg is relatively better than 12 mpg.

 

[GoldenGorilla]

Little improvements like @Steel City 06 and I have done add up to make a difference.

He's been far more intentional.

I wanted more power available which unintentionally resulted in better fuel economy. I've gotten 16.2mpg as my best tank with 55-65mph drving in rolling terrain on 33s and usually get 15.5+mpg with 65 mph highway driving now. A solid 20% improvement. Cd*V^2 gets ugly at 75mph even with p at 6000+ft elevation.

Still bad in context when our other cars get 26mpg highway and both have well over 300hp available. I was pretty surprised to put a full tank of miles on a Camry hybrid recently and get over 50mpg. I'd gladly take those 225-232 horsepowers in the TJ.