LS3 / 525 crate motor.... what's a "normal" operating temperature range
10-07-2019, 05:33 PM
#41
You're trying to create a temporary path of lower restriction for hot air to exit the compartment at the back of the hood. If the air can leave the compartment with less restriction, more air will move across the rad when the fans come on.
I don't know how the hoods work on these cars -- I'm imagining there's some sort of hood release inside the car and then a secondary latch at the back of the hood. Guess I was thinking you could tie off the latch on the hood side to the latch on the firewall side in a way that assures the hood won't come completely open but will remain 'cracked' to allow more airflow. Then go and drive the car - try to recreate the conditions that have caused problems in the past. If your temporary "vent" resolves the issue -- you know what the solution is.
Almost all vehicles reject the warm air from the engine compartment out the bottom/back of the engine compartment. If you have to vent the hood to solve the problem, be sure to do a bit of research about where to place the vent(s). Ideally, you want to pick a location that sees low pressure on the top of the hood as the car is moving. A low pressure area will enhance moving higher pressure air under the hood out the top. Low on the hood (near the front) and the base of the windshield are typically higher pressure areas. In between those two areas, where air is 'flowing' across the hood, air pressure will be lowest - the best spot for vents.
I don't know how the hoods work on these cars -- I'm imagining there's some sort of hood release inside the car and then a secondary latch at the back of the hood. Guess I was thinking you could tie off the latch on the hood side to the latch on the firewall side in a way that assures the hood won't come completely open but will remain 'cracked' to allow more airflow. Then go and drive the car - try to recreate the conditions that have caused problems in the past. If your temporary "vent" resolves the issue -- you know what the solution is.
Almost all vehicles reject the warm air from the engine compartment out the bottom/back of the engine compartment. If you have to vent the hood to solve the problem, be sure to do a bit of research about where to place the vent(s). Ideally, you want to pick a location that sees low pressure on the top of the hood as the car is moving. A low pressure area will enhance moving higher pressure air under the hood out the top. Low on the hood (near the front) and the base of the windshield are typically higher pressure areas. In between those two areas, where air is 'flowing' across the hood, air pressure will be lowest - the best spot for vents.
10-08-2019, 09:13 AM
#42
You're trying to create a temporary path of lower restriction for hot air to exit the compartment at the back of the hood. If the air can leave the compartment with less restriction, more air will move across the rad when the fans come on.
I don't know how the hoods work on these cars -- I'm imagining there's some sort of hood release inside the car and then a secondary latch at the back of the hood. Guess I was thinking you could tie off the latch on the hood side to the latch on the firewall side in a way that assures the hood won't come completely open but will remain 'cracked' to allow more airflow. Then go and drive the car - try to recreate the conditions that have caused problems in the past. If your temporary "vent" resolves the issue -- you know what the solution is.
Almost all vehicles reject the warm air from the engine compartment out the bottom/back of the engine compartment. If you have to vent the hood to solve the problem, be sure to do a bit of research about where to place the vent(s). Ideally, you want to pick a location that sees low pressure on the top of the hood as the car is moving. A low pressure area will enhance moving higher pressure air under the hood out the top. Low on the hood (near the front) and the base of the windshield are typically higher pressure areas. In between those two areas, where air is 'flowing' across the hood, air pressure will be lowest - the best spot for vents.
I don't know how the hoods work on these cars -- I'm imagining there's some sort of hood release inside the car and then a secondary latch at the back of the hood. Guess I was thinking you could tie off the latch on the hood side to the latch on the firewall side in a way that assures the hood won't come completely open but will remain 'cracked' to allow more airflow. Then go and drive the car - try to recreate the conditions that have caused problems in the past. If your temporary "vent" resolves the issue -- you know what the solution is.
Almost all vehicles reject the warm air from the engine compartment out the bottom/back of the engine compartment. If you have to vent the hood to solve the problem, be sure to do a bit of research about where to place the vent(s). Ideally, you want to pick a location that sees low pressure on the top of the hood as the car is moving. A low pressure area will enhance moving higher pressure air under the hood out the top. Low on the hood (near the front) and the base of the windshield are typically higher pressure areas. In between those two areas, where air is 'flowing' across the hood, air pressure will be lowest - the best spot for vents.
Thanks for the explanation. The hoods lift forward. I'll try to give it a good test by propping up the rear of it enough to were it looks like it'll vent. It'll be a good test. With the hood closed or even unlatched it does look like it's pretty closed off. The hood vent I'm looking at would be slightly forward the middle of the hood in a low pressure area while moving.
I do have stainless steel headers that aren't wrapped. So i have some wrap ordered to try and reduce under hood temps before i cut the hood. Fortunately/ unfortunately we just had a cool front come through in Louisiana so it may be a while until i get some 90-95* temps to test in.
Michael, Do you think this could be a tuning issue? Timing too far retarded at idle for my situation? Could advancing thinking at idle possibly help out? I know there's more to it than just adjusting timing like an older motor but just curious if it might be with looking into.
Ryan
10-08-2019, 10:03 AM
#44
Gmpp ecm that is supposed to be tuned for the cam they put in this 525 crate motor. It's an e67 ecm. Tilden motorsports only programmed ecm to work with factory tcm for the 4l70e. I do plan to bring it to have a custom tune on it soon. Just trying to figure this out before
On my torq app i see 12.5 -13.5* of timing at idle. It'll jump a little above and below that randomly. That timing is in park idling with ac on. Doesnt change if engine coolant temp is 200 or 230. I'm just thinking of carbd engines and manually adjusting distributor. I'm thinking it should all be ok in tune but never know.
Thanks again
Ryan
10-08-2019, 10:36 AM
#46
I've been told that the aerodynamics with the c3 hood while the car is moving, is that there may not be much air pulled out of a gap in the hood near the windshield area.
I've been told that vents near the nose are more effective.
Standing still, I have to believe that any gap or vent will help.
I've been told that vents near the nose are more effective.
Standing still, I have to believe that any gap or vent will help.
10-08-2019, 10:52 AM
#48
Launching!
Random thought, but you've also got 206*F IATs because your intake is picking up air from behind the radiator. I have no idea how that thing is tuned, but it seems reasonable to assume it's going to pull a good bit of timing for that, which may create a bit of a vicious cycle.
12.5* timing advance at idle sounds a little low, but not ridiculously so, though.
12.5* timing advance at idle sounds a little low, but not ridiculously so, though.
10-08-2019, 11:13 AM
#49
With GM tune I wouldn’t think timing would be an issue. Couldn’t agree more on getting cold air to intake tract - you lose 1/2-1% HP for each 10F of higher intake air temp. Base of the windshield and nose of the car are high pressure areas on all vehicles. It’s where the air “piles up” before it’s forced to change directions.
Last edited by Michael Yount; 10-08-2019 at 07:12 PM.
10-08-2019, 11:48 AM
#50
Yes. Even sucked it up and bought ls type radiator with stem line connection to rule it out. Used a vacuum tool to fill coolant to rule out any air pockets.
10-08-2019, 12:05 PM
#51
Random thought, but you've also got 206*F IATs because your intake is picking up air from behind the radiator. I have no idea how that thing is tuned, but it seems reasonable to assume it's going to pull a good bit of timing for that, which may create a bit of a vicious cycle.
12.5* timing advance at idle sounds a little low, but not ridiculously so, though.
12.5* timing advance at idle sounds a little low, but not ridiculously so, though.
Intake is getting air from over the top of radaitor. Which is great while moving. Radiators are leaned back in these cars and fans are angled downward. I do agree it is getting saturated with hot air and it doesnt take long to get to 130 or so at a stop light. Takes prob 15 min for iat to get to upper 100s and 25 or so to 200. I'm very limited to intake setups due space up front and how the hood opens/closes. At this point it's what i have now (and insulate/seal it better), typical 90*off tb and have it sitting there open on driver side of motor or 90* down and have it sitting low with prob radiator fans blowing on it. I don't think I'd have enough room to flip intake backwards.
Hopefully getting the headers covered will reduce some engine bay heat.
Anyone have recommendations on what to wrap that gto air box/tray with to help reduce intake air temps?
10-08-2019, 12:44 PM
#52
Launching!
Most ECUs will start pulling some timing when the air temp or coolant temp get high. What temperature they start pulling timing at, and how aggressively they pull timing varies from application to application. It seems like stock truck calibrations are absurdly aggressive about this stuff, for example.
10-10-2019, 04:29 PM
#54
10-10-2019, 05:07 PM
#56
Thanks, I'll have to think of something or sealboff my intake box. I know guys have gone so far as to put in a less wide radiatorbto get air tubing up front
10-11-2019, 07:56 AM
#59
10-11-2019, 08:05 AM
#60
Ha, yeah that's why i never considered it. I think best option is seal off box and insulate it. Along with header wrap and vent should help out my engine bay heat issue which seems in turn will help out engine temps at idle for extended periods of time.