When do I need a pyrometer?

[ThreeQuarter]

I am upgrading my exhaust (already installed a 3" downpipe) and I'm wondering at what point should I install a pyrometer? I would like to remove the soot trap and replace the muffler with another quiet one. If I go with a 3" all the way back, will I be setting myself up for turbo problems if I can't monitor the exhaust gas temps? What about 3.5"? Your experiences/opinions/best guesses are appreciated.

[DmaxMaverick]

A larger, higher flow exhaust in itself will lower EGT's, not create more of a need to monitor. Adding fuel, increasing boost, and/or adjusting timing creates a need to monitor. If the engine is otherwise stock, you won't increase EGT's, but monitoring is always a good option. If you are going to install a pyro, do it before your new exhaust or any changes. Monitor it during different conditions do get a baseline. After your exhaust (or other mod) upgrade, you will be able to see the result of your investment.

[sturgeon-phish]

Monitoring EGT is critical when under load, especially if you have mods that will fool the on-board computer, like boost foolers. The EGT is a great dignostic tool to monitor improvments from exhaust mods. If someone is stock and does not push their truck hard, EGT monitoring is "nice" but not mandatory, IMHO. Note: I have and reccomend an EGT gauge!
Jim

[More Power]

Back in the early days of The Diesel Page (1996-97) and 6.5 performance modifications, people would add power programming without making any other changes to the vehicle - no exhaust system mods, no gauges, etc. A number of these 6.5 owners damaged their engine during a hard pull up a steep grade with a trailer simply because they didn't know any better. This began the recommendation here in TDP for additional mods that help protect the engine when using upgraded programming - namely to install a performance free-flowing exhaust system and a set of boost pressure & exhaust temperature gauges.

Anytime you move away from the factory power or programming, the onus for protecting the engine is shifted onto whoever is driving the truck/Suburban.

Jim

[Cowracer]

You are probably ok with just an exhaust change so far, but the mantra I keep (kept) repeating over the years is.

1) exhaust
2) guages
3) chip
4) Injectors
5) crack open the engine and start messing with the greasy bits.


If you skip #2, you will go directly to #5

Tim

[ThreeQuarter]

Thanks, cowracer, for breaking it down simply. I have gotten out of order already--I forgot to mention that I have also installed "performance" injectors (high-flow, not high-pop). But they don't appear to be using any more fuel than the old stock ones I removed. The injectors, the downpipe, and a '97 cooling pkg. are the only perf. upgrades I've made, so IYO do you still think I need gauges? Or can they wait until just before I chip it?

[DmaxMaverick]

"High flow" injectors will not flow any more fuel than standard, in themselves. The "flow" is determined by the injection pump, not the injectors. Pressure is determined by the injector, by the pop pressure spec. High flow injectors will allow more fuel to pass through them at an extreme. Increasing the flow capability w/o a pressure increase only allows the fuel to pass through a larger hole, decreasing atomization (less efficient spray pattern). Realistically, they will decrease performance with an otherwise stock configuration. Having a higher flow ability means less restriction at lower volume, creating a situation for a less efficient spray pattern, and less efficient combustion. If you replace worn out injectors with high flows, you may not see any degradation, or improvement, because you were probably using a less efficient injector (worn out) before replacement. I suspect mileage and running characteristics would have improved at a greater rate with a stock configuration injector. If you plan on staying at or near stock performance levels, or don't use the potential of the injectors, you will likely see less than optimal performance, and economy. For lack of a better description, wasted money, fuel, and increased emissions (could cause quicker cat plugging, more black smoke and soot), unless you intend to use the full potential of a higher fuel flow injector. I think it's irresponsible for a retailer to sell these injectors w/o a disclosure of this sort. Many of them do it, but it doesn't make it right.

[ThreeQuarter]

Mav: I didn't catch your opinion about gauges... You're invited to comment on the merits of my injectors in my other thread: http://www.thedieselpageforums.com/tdpforum/showthread.php?t=31450 Thanks!

[DmaxMaverick]

Well....I guess my last post here could apply to both. I didn't have anything to add to MP's post on your question. I'm pretty sure he and I are on the same page with your situation.

Performance modifications are very subjective. It is a competitive market, and I don't care to comment on the claims most of the suppliers make regarding expectations (or blatant guarantees). I have more respect for suppliers who make no claims regarding guaranteed gains, than those who make false claims (most fall into this category). 40 HP injectors don't exist. There is no injector you can install on your 6.5L TD that will give you and additional 40 HP. You can get 40 HP with the injectors, but not by themselves. To me, this is misleading, and dishonorable business practice. Snake oil, for lack of a better description. If you want offline advice regarding specific modifications, I'll be glad to offer it (PM or email me). But, I won't get into that discussion on an open forum. I tend to speak my mind, and it usually conflicts with the general consensus and/or marketing claims. I think you will find this fairly common among most of the more educated/experienced folks around here.

[ThreeQuarter]

Truth be known: I thought I needed new injectors and I found a way to get these for $325, so I figured "What the heck, I'll gamble and see." Does that sound like a ripoff? I feel like I've been called a dope for buying them...and in a post where I was really asking for an opinion about a pyrometer.

It's cool that you're opinionated--opinions are what I was asking for, but I'm looking for pyro advice here.

[DmaxMaverick]

It happens a lot. When you run two "performance" related threads, they get crossed. I could have responded to your other thread, but I was already here, and the topic got skewed into the other already. You brought up the new injector install. I can merge the two together, if you wish.

No one was suggesting anyone is a dope. $325 for a set is a good price, if they do what you need of them. Just because it isn't what my first choice would be, doesn't make it a bad choice. Keep an open mind here. I do. As I've said before, much of this is subjective. And, I don't think I'm "opinionated", in as much. Educated and experienced, perhaps. But not opinionated. That's my opinion, anyway.........

[ThreeQuarter]

No sweat, DM.

OK, since we're off the topic of the pyro, I would like to discuss injector theory here. No doubt the 40HP claim is dubious. I'm not sure I even believe that there is potential for that much HP increase with other improvements. Anyway, here are some things that I want to discuss, mostly because I've read people's posts about these ideas but I haven't heard any engineering data to back it up--it all seems to be just theory in our heads. Thus, the argument AGAINST these injectors has no more real-world basis than the sales pitch FOR them. My other thread (referenced in a previous post) is my attempt to show some real-world experience with these nozzles, as feeble as it is (can't speculate on atomization, the condition of my old injectors, etc., can only report what I found).


The "flow" is determined by the injection pump, not the injectors.
My understanding of our systems is that the injection pump determines displacement, and nozzle size + pop pressure determine flow. (Flow is a rate, displacement is a volume.) So, yes, I'm getting the same displacement (in theory) with a higher flow. But I think there are other principles/factors at work here that my untrained, non-engineer brain doesn't register.


Increasing the flow capability w/o a pressure increase only allows the fuel to pass through a larger hole, decreasing atomization (less efficient spray pattern).
Is this a conclusion based on theory? Do we have a demonstration of the actual atomization and spray pattern that high-flow nozzles provide? Again, I think there are more factors than simple A+B=C, but I'm not an injector designer, so what do I know? And we also don't know which burns faster: more poorly-atomized fuel that is injected more quickly, or the same displacement that is atomized better but injected over a longer duration. You'd have to know the degree to which each of those factors is occurring before you could answer that question. (This is a theoretical question--I'm not yet willing to assert that atomization is worse with "high-flow" nozzles, because we just don't know that.)

If you have any hard data re: the atomization/spray patterns/pressures of hi-flow nozzles and stock nozzles, please share with the group! I can discuss theory all day long, but the problem is that theoretical discussions don't affect reality. Thanks!

[DmaxMaverick]

My use of the word "flow" was referring to the displacement. Not the actual characteristic of the fluid behavior.

Without high speed photography in a controlled environment, spray patterns are essentially speculative. Visually, it should be a mist or vapor, whereas worn injectors or less than optimal pressure/volume results in a less fine mist, or drops (dribble). Dribbling injectors create excessive hot spots in the combustion chamber, and incomplete/inefficient combustion. The hot spots can be on a piston crown, which can lead to disaster. Getting a specific volume of fuel into the combustion chamber is not enough. The fuel has to be available for combustion, meaning, the fuel droplets need to be exposed to the O2 in order to combust. Smaller droplets translates into more molecular exposure to the air. Higher flowing injector nozzles, at a given pressure/volume, will have a larger droplet size than a lower flowing nozzle. Same reason we put nozzles a the end of our garden hoses. It's my opinion, however informed or otherwise, increasing nozzle volume without increased pressure and/or fuel volume can decrease the efficiency of the spray pattern. A higher pressure at the same volume and nozzle size yields a shorter injection event, resulting in a higher rate of atomization. This can make the system more sensitive to timing. Diesel rattle, or ping, can be used to describe the result. This is why timing adjustments change the way the engine sounds, at the same fuel volume. Late Diesel engines use a multiple injection process (split shot, pilot injection, etc.) at much higher pressures, spreading a quicker combustion event over more of the stroke. This leads to less Diesel rattle and more complete combustion of the same amount of fuel (less fuel, more power, lower peak combustion temps and EGT, and the EGT is the average of the extreme combustion process temps).

The only use I can see for "high flow" injectors is high performance situations. High performance meaning, something other than normal, every day driving. Using a high flow injector at normal pressure and volume results in a less efficient fueling event. They must be use at or near their potential to gain an advantage. The term "high flow" can be very subjective. Were there any statements by the supplier indicating how much more flow? This could be very important. In all likelihood, it is an insignificant amount, IMO. If the amount were significant, it could cause serious problems for the normal user. The lack of catastrophic failures reported after installation of the "high flows" by normal users indicates to me the increase is essentially benign. Makes for an effective marketing pitch, though.

It is sometimes difficult to discuss the whys and wherefores without getting into fluid dynamics and physics (among other sciences). Many theories and laws apply, and there is very little room for speculation once broken down to the level of the science. I can get as "scientific" as you can stand, but I generally try to keep it in simple terms. Let me know if I get too far out there.

[More Power]

If I were selling "high-flow" or "high-pop" 6.5 injectors, and truly believed that they provided some benefit I would publish engine/chassis dyno results comparing new OE and new "high-flow" or "high-pop", and I'd invite customers to do the same. If improved fuel economy was an ad claim, I would also perform a BMSFC test to prove it.

Without independently verified and published qualitative/quantitative test results, ad claims are just that... (mostly BS)

Some vendors sell "marine" injectors with the inferred claim of better performance. Again, without reproducible and verified test results, the ad claims are just that. I prefer to use marine injectors with marine fuel injection pumps, and OE injectors with OE fuel injection pumps... ;)

And another thing.... I've been a part of the magazine industry long enough to know that when they publish dyno data as part of an article, the shop's name, location and type/brand of dyno are specified in the article. Anyone reading the article could contact that shop to verify the numbers.

Jim

[rustyk]

To get back to the original question (When Do I Need a Pyrometer?):

Always with a turbodiesel. Otherwise, you'll not know what's going on down there...