99 C2500 5.7l IAT

[computerfriedbrains]

Hi, guys! Noticed a similar thread, but that's for a different application from mine. I have LTH on a brand new 5.7 Vortec. Here's my question. As we all know, the hotter the IAT reads, the more spark it pulls back. It's running about 120*-130* with AC on, at 90* ambient. Here in South Texas, it gets to the low 100's pretty easily. My question is, should I adjust the IAT/Spark Retardation table, or just do what the guy who installed the engine for me's, suggestion. Which was, splice in a pigtail, and have the IAT read from the front of the truck. Which would be better? I plan on shielding the intake better (K&N), or even routing it to about where the stock intake pulls in air from the fender well. Lastly, is the retardation to protect the external components under the hood, or the internal? I'm still new to tuning, and have a rather... Eclectic variety of mechanical knowledge. This particular topic is one of those things I don't know very well. Thanks!

[Oleblu]

Leave it factory location. Or put it closer to the filter. Adjust your table to start removing timing at 115F get aggressive taking timing out after 130.

[Fast4.7]

Ditch the K&N and pickup a Volant intake. Cooler air is better for power all around. I had a Volant on the 99 Suburban and later transfered it to the 99 Tahoe with the cammed 305 as well. My 2011 4.0L Pathfinder also has a Volant. The Volant system gave a noticeable power and performance gain on all 3. Be careful removing the timing retard. It can cause detonation and knock retard. Lastly use a 170?F thermostat. I got mine at Oreilly.

[Fast4.7]

Murray 4117 is the 170F for a Vortec. It will drop the coolant temp, allow the iron heads to run cooler and allow you to run MBT timing without detonation. My 97 Express van was much lighter on its feet so to speak in hot weather running cooler. With the 170F thermostat, it ran 178-182F year round here in North Texas. It also keeps the fan clutch from engaging as often or as long which was more added power and better mpg. With the stock engine and headers I was able to run more timing advance. I was able to run 29-31 degrees of timing on 91 octane which resulted in peak output from the near stock engine. Factory timing map only gives at most 24 degrees of timing.

[computerfriedbrains]

I actually used to have a 170* thermostat in it, but I finally put the stock 190* one back in, because it was KILLING my gas mileage. Is that tunable? That parameter? Also, where can you get Volant? I've never even heard of them. I know K&N, Airraid, and airdog(?).
Thanks for the advice!!!

[kingtal0n]

If you start messing around with high flow air filters you will need to measure/monitor crankcase pressure to prevent oil from blowing out of the engine over time.

WOT pcv action is supplied via air filter pressure drop (air filter restriction drives PCV at WOT) and if you eliminate the pressure drop, you've eliminated PCV suction.

For IAT I prefer monitor just before the intake manifold in an aluminum pipe, like intercooler plumbing. Use a plastic washer and brass style IAT sensor to relocate and isolate.

[computerfriedbrains]

If you start messing around with high flow air filters you will need to measure/monitor crankcase pressure to prevent oil from blowing out of the engine over time.

WOT pcv action is supplied via air filter pressure drop (air filter restriction drives PCV at WOT) and if you eliminate the pressure drop, you've eliminated PCV suction.

For IAT I prefer monitor just before the intake manifold in an aluminum pipe, like intercooler plumbing. Use a plastic washer and brass style IAT sensor to relocate and isolate.

OK, I'll def do that. already ordered a Volant to replace my K&N, I'll see what that can do for me. Thanks!

[Fast4.7]

I actually used to have a 170* thermostat in it, but I finally put the stock 190* one back in, because it was KILLING my gas mileage. Is that tunable? That parameter? Also, where can you get Volant? I've never even heard of them. I know K&N, Airraid, and airdog(?).
Thanks for the advice!!!

I didn't change anything on my 97. It gets better mileage with the 170F and always has. Even with the 0411 and now the P59 it has worked well with the 170F. Closed loop happens quickly on these, its in closed loop in under a minute. I don't see how a 170F negatively effected your MPG. Mine was a dog and would spark knock anytime the engine got even close to 200F.1

[Fast4.7]

If you start messing around with high flow air filters you will need to measure/monitor crankcase pressure to prevent oil from blowing out of the engine over time.

WOT pcv action is supplied via air filter pressure drop (air filter restriction drives PCV at WOT) and if you eliminate the pressure drop, you've eliminated PCV suction.

For IAT I prefer monitor just before the intake manifold in an aluminum pipe, like intercooler plumbing. Use a plastic washer and brass style IAT sensor to relocate and isolate.

I have had free flowing air filters for years on many makes of vehicles. Never have expeienced oil blowing out of the engine. Personally don't see how that can even happen unless the seals or gaskets are bad. On my 97 the IAT or rather MAT was in the T-Map on my Marine intake and currently in the MAF on my modified stock intake. Not much difference either way.

[Fast4.7]

OK, I'll def do that. already ordered a Volant to replace my K&N, I'll see what that can do for me. Thanks!

You will like it. It pulls cooler air directly through the fender like the OEM intake but the plumbing is streamlined for better airflow. My LT1 cammed 99 Suburban went from a 9.3-9.4 to a 9.1 and even 9.0 a few times in the 1/8th. Gained 2-3 mph trap speed too. S10 converter and 3.42s. Stock L31 with a 95 F-car LT1 cam, Hooker long tubes and dual 2.25" Hooker exhaust with a H-pipe.

[kingtal0n]

I have had free flowing air filters for years on many makes of vehicles. Never have expeienced oil blowing out of the engine. Personally don't see how that can even happen unless the seals or gaskets are bad. On my 97 the IAT or rather MAT was in the T-Map on my Marine intake and currently in the MAF on my modified stock intake. Not much difference either way.

you never measured crankcase pressure so how do you know it was adversely affected? All I said was to measure it to make sure. Not that it would definetely cause a issue to use a aftermarket filter.

My filter is AFE 7-Layer and produced 1.5" Hg at wide open throttle 600rwhp. But at just 300rwhp there is no pressure drop I bet. So application & power output total vs CFM flow rate of the filter matters.


This is a very common issue it even has a TSB
truckpcv.png




Almost always caused by high flow filters on stock engines which cannot pull a vacuum on the crankcase at WOT, causing oil to flow into baffle system and blow from the engine.

Then people blame the PCV system without realizing the filter is part of the PCV system.


PCV is a high performance secret, you measure it carefully and set it up for the engine, every time.

[Fast4.7]

you never measured crankcase pressure so how do you know it was adversely affected? All I said was to measure it to make sure. Not that it would definetely cause a issue to use a aftermarket filter.

My filter is AFE 7-Layer and produced 1.5" Hg at wide open throttle 600rwhp. But at just 300rwhp there is no pressure drop I bet. So application & power output total vs CFM flow rate of the filter matters.


This is a very common issue it even has a TSB
truckpcv.png




Almost always caused by high flow filters on stock engines which cannot pull a vacuum on the crankcase at WOT, causing oil to flow into baffle system and blow from the engine.

Then people blame the PCV system without realizing the filter is part of the PCV system.


PCV is a high performance secret, you measure it carefully and set it up for the engine, every time.

Must be a highly special case. I have measured crankcase pressure on a few engines but never a stock one. Basically I measured to be sure the stock PCV system was flowing adequately. I would think if it were an issue I would see oil consumption. My Titan had a 2,200 cfm filter on it and never saw excess oil burning. That same filter got recycled onto a 6.0L in an 87 G20 van. That 6.0L used very little oil with the GM revised LH valve cover. My intake tubes and throttle bodies stay clean and oil free. Whatever small aount of oil finds its way into the intake manifold is from the PCV valve. Old small blocks had a breather system that dumped in on the outside of the air filter with a separate breather filter and the marine engines have an open tube pointed at the flame arrestor.

[kingtal0n]

Every engine has blow by so every engine has PCV flow. If pressure rises above atmospheric there is a slew of issues ranging from oil contamination to partial pressure of dissolved gasses to the density of gas flowing through the pcv system carries more oil. Crankcase pressure must be set by the engine owner per specific application to maintain 0.5" to 1" Hg at all times.


Dangerous crankcase gas




Partial pressure of dissolved gas, dynamic equilibrium from chemistry textbook applies to all liquid-air interfaces



Blowby gas influence on ring function




PCV valve blows oil out to the intake manifold in natural aspiration when crankcase pressure rises



A vacuum pump article statement regarding influence of gas density



Proper crankcase suction due to filter restriction is a measurable quantity


Published paper PCV crankcase pressure target 0.5" to 1" Hg for OEM engines



Threads where I cover these items in sometimes excruciating detail
https://www.supraforums.com/threads/.../post-13980010
https://www.thirdgen.org/forums/powe...ml#post6462919
https://www.theturboforums.com/threa.../#post-2050290
https://www.corvetteforum.com/forums...post1604427919
https://www.corvetteforum.com/forums...post1604386206

crankcase pressure situations with dry sump
https://www.corvetteforum.com/forums...post1601048750
http://www.turbosport.co.uk/showthre...=1#post3147205


Crankcase pressure, oil leaking


Electric vacuum pump , importance of crankcase pressure practical application for oil control
https://www.evolutionm.net/forums/ev...l#post11930508

I decided the short the Hobbs switch to check out the vacuum with the air pump turned on. To my surprise it wasn't turning on. Upon inspecting the 15amp fuse it had blown so it was not working when under boost. This might explain why I had oil pushing past the rear main seal. I swapped in a 20amp fuse and it works like it should and pulls ~5" at idle. Because I monitor the pressure with my AeroForce Gauge it allows me to set a warning light. I now have the warning light come on anytime the PCV presssure exceeds 0psi.

notice it applies to all engine crankcase systems. Symptoms take time to develop. A major warning sign in Natural aspiration apps is pcv valve orifice flowing oil, which can only happen if the engine crankcase pressure at WOT is going higher than intake manifold pressure. Leading to people blaming the pcv system and baffle system when it was the air filter preventing WOT pressure drop on the crankcase which causes PCV valve to flow oil.