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So I cut the shroud between the two "ears" where the pins hold in on. It's double layered plastic and a bit a pain in the **** but it didn't take too long.
I got the idea from another post to use Torque to log my LTFT's and Intake temperature. So did.
Before I cut I made a 20 mile each way trip and saw a peak intake temp of 40'C with ambient temps around 20'C...this was during city driving.
I monitored the intake temp as I hit the highway and it took about 10 minutes for the intake temp to bottom out at +4'C above ambient.
I cut the 1 part of the shroud out and the other part bent it down. Did a quick 10 mile round trip and in the first 2 minutes saw temps as low as +3'C above ambient.
I then removed the rest of the plastic so there is a 6-7" X1" cut in the shroud now to permit airflow. Ran the same 10 mile circuit and saw temps get as low as +2'C above ambient (which is now up to 23'C)
So my questions are:
1. is +2'C above ambient good for intake temperatures?
2. My LTFT's are slightly different from side to side. Are usually around +1-3 and are within 5 points of each other always. Under driveline braking (downshifting) they go quite high say maybe +10-12. Very rarely are they negative. Are these within norms for a stock LS2?
3. Timing is around 30-33' during cruise at 75MPH and even with some hard pulls I've only seen the timinig go negative once. Does this mean anything?
4. I've had some acceleration pinging...which I attribute to the 11 year old plugs and wires and I've ordered replacements. However after this modification it seemed to eliminate all the pinging I was getting. Would the lower temps really eliminate this issue?
5. I seafoamed the car when I bought it 1000 miles ago...but noticed that the bottom of my intake is still pretty grungy and there is trace oil stuck in the ribs of the horrible stock accordion duct. Do I need to replace something in my PCV system or is this Normal?
Thanks in Advance guys.
PS...torque has a ton of functionality I didn't even know about.
Edit: PPS I had no surging or codes. The car actually runs much better even shifting smoother.
Shroud of Turin? I have no idea what shroud you are talking about. A few pics would help a lot. WTF is Torque other than a measurement of bending moment (which is very useful, I agree but I think you are talking about something else entirely)?
2 degrees C above ambient sounds like a pretty good intake temp, you're not going to get more than 2 degrees C cooler than that.
Shroud of Turin? I have no idea what shroud you are talking about. A few pics would help a lot. WTF is Torque other than a measurement of bending moment (which is very useful, I agree but I think you are talking about something else entirely)?
2 degrees C above ambient sounds like a pretty good intake temp, you're not going to get more than 2 degrees C cooler than that.
Cut my radiator shroud.
Torque is an OBD II diagnostic software that works with the cheap chinese bluetooth adaptors and logs data from the ecu.
So I cut the shroud between the two "ears" where the pins hold in on. It's double layered plastic and a bit a pain in the **** but it didn't take too long.
I got the idea from another post to use Torque to log my LTFT's and Intake temperature. So did.
Before I cut I made a 20 mile each way trip and saw a peak intake temp of 40'C with ambient temps around 20'C...this was during city driving.
I monitored the intake temp as I hit the highway and it took about 10 minutes for the intake temp to bottom out at +4'C above ambient.
I cut the 1 part of the shroud out and the other part bent it down. Did a quick 10 mile round trip and in the first 2 minutes saw temps as low as +3'C above ambient.
I then removed the rest of the plastic so there is a 6-7" X1" cut in the shroud now to permit airflow. Ran the same 10 mile circuit and saw temps get as low as +2'C above ambient (which is now up to 23'C)
So my questions are:
1. is +2'C above ambient good for intake temperatures?
2. My LTFT's are slightly different from side to side. Are usually around +1-3 and are within 5 points of each other always. Under driveline braking (downshifting) they go quite high say maybe +10-12. Very rarely are they negative. Are these within norms for a stock LS2?
3. Timing is around 30-33' during cruise at 75MPH and even with some hard pulls I've only seen the timinig go negative once. Does this mean anything?
4. I've had some acceleration pinging...which I attribute to the 11 year old plugs and wires and I've ordered replacements. However after this modification it seemed to eliminate all the pinging I was getting. Would the lower temps really eliminate this issue?
5. I seafoamed the car when I bought it 1000 miles ago...but noticed that the bottom of my intake is still pretty grungy and there is trace oil stuck in the ribs of the horrible stock accordion duct. Do I need to replace something in my PCV system or is this Normal?
Thanks in Advance guys.
PS...torque has a ton of functionality I didn't even know about.
Edit: PPS I had no surging or codes. The car actually runs much better even shifting smoother.
OK - So, not sure I'll get all your questions answered.
1. Ambient C compared to IATC - From part of your text, at 23C ambient, it is very easy to match IAT or be within 1*C with the stock CAI and unaltered. I have numerous datalogs using HPT that show this. The real test is in the range of 32-35*C. At this point, the stock CAI begins to separate and can be 5-8*C higher than ambient 35C.
At 32C, the ECM begins to pull timing because of IAT being to hot. 3* timing is pulled at a spark air mass of .52 all the way up to a SAM of 1.36. So, if your location gets up to 32C ambient at any time, this is where you want to DL; otherwise, there is no gain in IAT if you just left the shroud alone.
2. On LTFTs anywhere around a +5%to a -5% on either side is within normal ranges. When I tune, I seek to hold a -3 to -5% on both sides. I do not like to maintain + LTFTs as these lean trim corrections carry into PE which interrupts the PE fueling refinement I like to maintain.
Ignore high LTFTs on deceleration because of DFCO. Fuel cutoff at deceleration will impact LTFTS but not anything to adjust. They are recording what they should. Only be concerned about LTFTs when holding a throttle position or accelerating, at least up to PE. After PE, it is open loop unless you brought into PE a lean FT.
3. 30-33* timing is not very meaningful unless I can see spark air mass, or some relationship to commanded throttle. It is probably normal. WOT, if everything is stock, should be more around 20-22*.
4. Not enough information to evaluate spark retard. The pinging you are describing can be caused by numerous items. For example - what temp range spark plugs? What are the ambient air temps?, altitude? Fuel? Then after these are known, what tuning intervention has there been? Changes to fueling in PE? For example. Too many unknowns.
OK - So, not sure I'll get all your questions answered.
1. Ambient C compared to IATC - From part of your text, at 23C ambient, it is very easy to match IAT or be within 1*C with the stock CAI and unaltered. I have numerous datalogs using HPT that show this. The real test is in the range of 32-35*C. At this point, the stock CAI begins to separate and can be 5-8*C higher than ambient 35C.
At 32C, the ECM begins to pull timing because of IAT being to hot. 3* timing is pulled at a spark air mass of .52 all the way up to a SAM of 1.36. So, if your location gets up to 32C ambient at any time, this is where you want to DL; otherwise, there is no gain in IAT if you just left the shroud alone.
2. On LTFTs anywhere around a +5* to a -5* on either side is within normal ranges. When I tune, I seek to hold a -3 to -5* on both sides. I do not like to maintain + LTFTs as these lean trim corrections carry into PE which interrupts the PE fueling refinement I like to maintain.
Ignore high LTFTs on deceleration because of DFCO. Fuel cutoff at deceleration will impact LTFTS but not anything to adjust. They are recording what they should. Only be concerned about LTFTs when holding a throttle position of accelerating, at least up to PE. After PE, it is open loop loop unless you brought into PE a lean FT.
3. 30-33* timing is not very meaningful unless I can see spark air mass, or some relationship to commanded throttle. It is probably normal. WOT, if everything is stock, should be more around 20-22*.
4. Not enough information to evaluate spark retard. The pinging you are describing can be caused by numerous items. For example - what temp range spark plugs? What are the ambient air temps?, altitude? Fuel? Then after these are known, what tuning intervention has there been? Changes to fueling in PE? For example. Too many unknowns.
5. No comment about seafoam...at all....
Thank you.
Lots of good info.
I changed the plugs and wires tonight. Installed AC Delco 41-110 plugs and 9748RR wires.
The old plugs were fine the old wires were pooched. A quick warm up and run showed no signs of the telltale pinging, but it's only 23'C and humid.
The tune on the car is 100% stock. I'm trying to get everything sorted out so I can use my Diablo Intune I2 and install the canned tune...then eventually a Dialblew tune.
I will try to log some other data points with my tablet once the car gets used to all 8 cylinders firing all the time.
You're welcome - Not sure 32*C is ever a problem in Nova Scotia so maybe never will IATs be an issue for you. As long as typical driving temps maintain 29*C or lower, you will not have an IAT issue. Then it is a matter of whether you have better airflow if you use any type of CAI. Typically, with an LS3, the stock CAI is sufficient for airflow as the filter is NOT the gate. I do NOT have as much first hand experience with LS2s, but I understand there can be improvements in airflow over the stock CAI on an LS2 factory filter.
Before I cut I made a 20 mile each way trip and saw a peak intake temp of 40'C with ambient temps around 20'C...this was during city driving.
I monitored the intake temp as I hit the highway and it took about 10 minutes for the intake temp to bottom out at +4'C above ambient.
I cut the 1 part of the shroud out and the other part bent it down. Did a quick 10 mile round trip and in the first 2 minutes saw temps as low as +3'C above ambient.
I then removed the rest of the plastic so there is a 6-7" X1" cut in the shroud now to permit airflow. Ran the same 10 mile circuit and saw temps get as low as +2'C above ambient (which is now up to 23'C)[QUOTE]
I should have commented about these and I realized I did not.
For the remark about "before the shroud cut" - in a 20 mile drive you saw a peak 40*C IAT with 20*C ambient air temps in city driving, this is not a good test because as you stop and go in city driving and with very slow speeds, the IAT is subject to heat soak just from stagnant air flow in and around the engine compartment. But, and this is important - if you're commanding very low throttle %s as in city driving, then IATs are not that impacted by rising air temps. Next time, continue out of the city on open roads, travel at more like 65 to 80 kph and see if ambient C and IATC return to 1 or 2*C difference. It should/will. The stop go, slow driving is not representative of performance driving where the air flow dynamics come in to play a big part.
I should have commented about these and I realized I did not.
For the remark about "before the shroud cut" - in a 20 mile drive you saw a peak 40*C IAT with 20*C ambient air temps in city driving, this is not a good test because as you stop and go in city driving and with very slow speeds, the IAT is subject to heat soak just from stagnant air flow in and around the engine compartment. But, and this is important - if you're commanding very low throttle %s as in city driving, then IATs are not that impacted by rising air temps. Next time, continue out of the city on open roads, travel at more like 65 to 80 kph and see if ambient C and IATC return to 1 or 2*C difference. It should/will. The stop go, slow driving is not representative of performance driving where the air flow dynamics come in to play a big part.
I did this more to get the IAT up and see how long it took to drop back down to ambient.
Without the shroud cut it took 10+ minutes of driving at 75mph to drop the temperatures to what they bottomed out.
With the shroud cut it takes less than 2 minutes at 75mph to accomplish the same thing..from the around 40'C mark.
The cut only improves the rebound time I don't believe it lowers temps any more than 1-2'C
Again..thank you for all the great info.
The other issue I'm having now is that I seem to be pulling oil from the "clean" pcv line. This may have to do with several WOT pulls I've done as part of my diagnosing. I normally don't go WOT often but have done so maybe 8-10 times in the last two days trying to detect ping/log data.
With my plugs changed I feel the pinging issue is gone, however, I'm concerned that I may have some underlying issue causing this excess oil migration through the pcv.
I did the old school check with a piece of paper to the oil filler cap under idle and there was vacuum there...so I'm hoping that blowby isn't an issue. But I understand that this is hooked to the intake...so there is a source of vacuum there at all times.
Alot of posts seem to recommend a "catch can" I had one on my C5 and it had a few ounces in it every oil change. I'm wondering if this would solve my issue. Any thoughts?
I did this more to get the IAT up and see how long it took to drop back down to ambient.
Without the shroud cut it took 10+ minutes of driving at 75mph to drop the temperatures to what they bottomed out.
With the shroud cut it takes less than 2 minutes at 75mph to accomplish the same thing..from the around 40'C mark.
The cut only improves the rebound time I don't believe it lowers temps any more than 1-2'C
Again..thank you for all the great info.
The other issue I'm having now is that I seem to be pulling oil from the "clean" pcv line. This may have to do with several WOT pulls I've done as part of my diagnosing. I normally don't go WOT often but have done so maybe 8-10 times in the last two days trying to detect ping/log data.
With my plugs changed I feel the pinging issue is gone, however, I'm concerned that I may have some underlying issue causing this excess oil migration through the pcv.
I did the old school check with a piece of paper to the oil filler cap under idle and there was vacuum there...so I'm hoping that blowby isn't an issue. But I understand that this is hooked to the intake...so there is a source of vacuum there at all times.
Alot of posts seem to recommend a "catch can" I had one on my C5 and it had a few ounces in it every oil change. I'm wondering if this would solve my issue. Any thoughts?
Yes, if you improve recovery time cooling down the measured IAT back to 1-2*C difference from ambient air temps when accelerating back to steady 70/80 kph from lower speeds then very good mod on the shroud cut.
For the PCV issue, it is pretty common with lots of pulls to build crankcase gasses from some blowby. Leaving the factory PCV "tube" in place will draw wet gasses into the intake. I think you are describing the upper vent tube from the valve cover outlet to the intake charge tube. Wet residue there isn't a good sign. How many miles on the engine?
A catch can is a very good addition if you are going to push an LS engine a lot. When I did my catch can it is a little more sophisticated because of the FI. Here, I needed a CC with a one way valve because of the intake manifold changes from vac to pressure. I take the crankcase gases directly from the valve cover, through the can and return clean back to the clean side of the PCV (intake manifold). The dirty CC side of the PCV gets drawn off from the direct line into the intake, at the air filter. This line is long enough that solids do not make it to the filter, just gasses are pulled by the vac created at the intake air tube. Catch can is good
Yes, if you improve recovery time cooling down the measured IAT back to 1-2*C difference from ambient air temps when accelerating back to steady 70/80 kph from lower speeds then very good mod on the shroud cut.
For the PCV issue, it is pretty common with lots of pulls to build crankcase gasses from some blowby. Leaving the factory PCV "tube" in place will draw wet gasses into the intake. I think you are describing the upper vent tube from the valve cover outlet to the intake charge tube. Wet residue there isn't a good sign. How many miles on the engine?
A catch can is a very good addition if you are going to push an LS engine a lot. When I did my catch can it is a little more sophisticated because of the FI. Here, I needed a CC with a one way valve because of the intake manifold changes from vac to pressure. I take the crankcase gases directly from the valve cover, through the can and return clean back to the clean side of the PCV (intake manifold). The dirty CC side of the PCV gets drawn off from the direct line into the intake, at the air filter. This line is long enough that solids do not make it to the filter, just gasses are pulled by the vac created at the intake air tube. Catch can is good
Engine has 96,000 kms or 60,000 miles. Car runs fine and with new plugs and wires pulls really well.
I was describing the valve cover to the intake tube hose being wet(at the nipple where it meets the tube).
I will pull the intake again tonight and have a look in the manifold. Excess vacuum could pull some oil from the valve cover as well. But this car is new to me....so anything is possible at this point.
I used seafoam to do a top end cleaning so the manifold should have been spotless. But it definitely has oil still in there. I'm thinking a catch can would help this (it did on my c5) but obviously it's not going to stop pulling oil/vapour from the valve cover.
Yeah, should not be dirty up there. Check the PCV loop (U-tube) see if it's really dirty or clogged up. A two port CC would solve it if it is really dirty, but if it is easy for you to do a cylinder leak down test would be good.
Yeah, should not be dirty up there. Check the PCV loop (U-tube) see if it's really dirty or clogged up. A two port CC would solve it if it is really dirty, but if it is easy for you to do a cylinder leak down test would be good.
I don't have the gear for a leak down test. I will check to ensure that the valley cover to intake manifold tube is clean tonight.
I will clean the stock accordion duct well. And monitor this over the next few weeks of daily driving.
The car was very clean...starts easy and was a two owner car (it had GMPP till 2012) and has only had 5000 miles put on it since then by ~65 year old fella. I'm really hoping the engine doesn't have an underlying issue. I spent top dollar to buy this thing. I looked under the car thoroughly with a head lamp before purchase and there wasn't so much as a drop of oil or wet spot underneath. I couldn't have said that about my 60,000 mile C5.
Looks like oil ingestion from this port is common under hard acceleration so much so that both GM and Elite engineering offer a Clean side separator as a solution.
I'm gonna clean it up and drive normally for a few weeks. If the problem persists. I'll order both the catch can and the CSS.
If I get lots of oil...I'll start digging into this further. But I'm betting it's from me gunning it WOT on every on ramp/opportunity for the last 3 days trying to detect WOT pinging.
It's also remotely possible that it's been pinging for some time and this has damaged the pistons...however I'd have to believe oil consumption would be through the roof...and it's not. It hasn't changed level since I bought the car. and I've got more than 1000 miles on it.
I really appreciate you taking the time to answer my questions.
These cars run pig rich from the factory... I see no reason for the pinging, your not getting more air... just fresher air
How much butt dyno improvement did you feel??
Pinging was from the absolutely trashed stock wires and it was there before I cut the shroud, went away afterwards. I didn't feel more in the butt dyno but it sounded the way a corvette should. And pulled like my old C5 smooth and fast. 80kph to 200kph in a few seconds. Idle is way smoother.
I think the lower intake air temps helped with preventing detonation, but the real issue was poor spark quality from the 11 year old wires.
I'll have to wait and see if there is another issue at play as Blind has suggested. I'm hoping not.
If you have a stock intake I would cut the shroud....it's easy and corrects what I see as an obvious oversight of no cold air intake from the factory (I think the z06 and LS3 have the issue corrected somewhat)
If you're ambitious and have 125.00 you can get a vette-air (what I cut out is the same as what you would need to remove in order to install this unit)
09-18-2017, 09:49 PM
Cut the shroud...Have a few questions
