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After removing the clips and hood insulator, decided to apply damping material to underside of hood.
The hood lacks adequate damping and suffers from panel flutter...especially near windshield.
I had considered injecting Automotive grade foam or adding additional adhesive between upper and lower hood panels..as the original adhesive is tired.
Butyl damping sheets are too heavy, will overwhelm the hood struts and will not respond well to engine heat.
However, neoprene loaded cork offers damping, light weight and is rated for 220 F.
Acquired 36" X 36" X 1/8" sheet from McMaster-Carr.
Some images of the work.
Will not extend application of cork further forward to avoid overwhelming the hood struts.
Underside of hood with insulator removed. Material installed. Will not apply cork further to avoid overwhelming hood struts. May apply thin aluminum over cork to improve damping. Paper templates atop cork sheeting. Same template works on mirror opposite side attests to production unformity. Perhaps not necessary to tailor the material, but makes for better presentation.
I don't understand only doing half. Why any if not the whole thing? If you're worried about compromising the hood struts just get some more heavy duty hood struts. I know they exist, my hood struts have so much compression I need to actually put some force into moving it. Not sure what brand the previous owner put on but I can take a look.
You mentioned maybe putting aluminum in there also. I'm not an engineer, just an insulator (40 years), but wouldn't the aluminum work as a radiant barrier and just deflect all the engine heat back into the engine bay and heat from the sun back up onto the hood?
I don't understand only doing half. Why any if not the whole thing? If you're worried about compromising the hood struts just get some more heavy duty hood struts. I know they exist, my hood struts have so much compression I need to actually put some force into moving it. Not sure what brand the previous owner put on but I can take a look.
You mentioned maybe putting aluminum in there also. I'm not an engineer, just an insulator (40 years), but wouldn't the aluminum work as a radiant barrier and just deflect all the engine heat back into the engine bay and heat from the sun back up onto the hood?
The hood struts work well in Summer but are less supportive in colder weather.
Placing more weight at the top end (front).of hood exerts more leverage and may overcome the hood struts.
McMaster-Carr advises the 36" X 36" X.1/8" neoprene cork weighs 5.4 pounds...
I estimate adding almost 2 pounds already.
Welcome information on higher pressure hood struts...of course overcoming increased strut pressure requires exerting more force while closing the hood.
I would be concerned about stressing the hood or gas strut mounting points.
A majority of aftermarket butyl-based damping materials use an Aluminum constraining layer.
This also.serves as an abrasion and heat barrier.
The idea is to apply a thin aluminum sheet to the cork to improve its effective damping.
Unconstrained it is not as effective as butyl.
Some info with image on point: Untreated steel, Free Layer Damping and Constrained Layer Damping
I don't understand only doing half. Why any if not the whole thing? If you're worried about compromising the hood struts just get some more heavy duty hood struts. I know they exist, my hood struts have so much compression I need to actually put some force into moving it. Not sure what brand the previous owner put on but I can take a look.
You mentioned maybe putting aluminum in there also. I'm not an engineer, just an insulator (40 years), but wouldn't the aluminum work as a radiant barrier and just deflect all the engine heat back into the engine bay and heat from the sun back up onto the hood?
Aluminum isn't much of an insulator, but it is a fantastic conductor of heat.
Waiting for actual measurement results in dB with spectrum charts.
Where would you propose I place the dB meter when traveling at 60 MPH (100kph)?
This particular project contends with hood panel flutter and to dampen vibrations that can be felt on the hood.
I put my fingers and ears on the hood at idle, and report back to everyone if a difference.
If you can arrange for Toyota facilities to perform testing then am happy to make the car available.
I submitted before and after professional test data when I extrude honed the intake manifold and received nothing but criticism on the 20 H.P. and 25 ft/lbs torque increase.
Open your hood and knock on it and you will observe the hood flutter...especially at span closest to windshield, where high pressure exists...thin sheetmetal in contemporary automobiles is a contributing factor.
It is more pronounced in other brands...can actually see another manufacturers hood flopping up and down in back at highway speeds...and hear the wind buffeting.
Have considered selectively injecting two part Automotive grade foam into hood voids but difficult finding anyone body shop wise who really understand how to correctly apply it.
Two part foam expands rapidly and with such thin sheet metal do not wish to mess up the hood.
A majority of hoods would respond well to increased rigidity.
One more question: would increase in airflow (due to extrude honing) increase the fuel consumption too? In that case, the same can be obtained by just increasing the size of the air intake. I've seen some guys cutting the air filter box half open, so the engine gets more air, but I assume that besides extra HP it also consumes extra fuel.
Sorry to switch subjects, but where did you get the extrude honing done?
And for those who want to see what it looks like, it's quite surreal: https://www.youtube.com/watch?v=2QBc59YZYxA
(the interesting bit is around 1:50)
See post featuring extrude hone and dyno testing of ACIS. (Acoustic Control Induction System) manifold on 1999 LS400
One more question: would increase in airflow (due to extrude honing) increase the fuel consumption too? In that case, the same can be obtained by just increasing the size of the air intake. I've seen some guys cutting the air filter box half open, so the engine gets more air, but I assume that besides extra HP it also consumes extra fuel.
It was explained to me that an internal combustion engine is but an "air pump".
The longer intake runners of the Acoustic Control Induction System on our LS400 LS430 had a fair amount of seams, casting flash and roughness.
The primary goal was to remove these internal snags to improve airflow uniformity between runners, airflow efficiency and reduce unproductive turbulence...so the engine breathes easier.
It was not to port the intake in the traditional sense.. notwithstanding the fact there was no practical way to do it on this ACIS intake
The other goal was thermal management...
The roughness of the intake runners and interior chambers of ACIS casting imparts more heat into intake airflow vs smooth surface.(rough surface = increased surface area)
Less heating of intake air equals greater charge density.
As far as air-fuel mixture, the ECU controls this.
Arguably, if I wish to travel at steady 60 MPH, the engine requires a set amount of fuel (energy consumed) to maintain that speed.
With similar engines, if one breathes easier, or can more easily draw air, then it has the potential to produce more power on demand, is more efficient and less emissions.at a comparable RPM and you don't have to press as far on the pedal for a set speed.
A dirty air cleaner element is an example of an understood airflow restriction which reduces power, increases fuel consumption and increases emissions.
You can easily stall a large displacement gasoline engine by covering the main air intake with your hand. (Don't try this with a diesel!) As testimony to how sensitive an engine can be to airflow.
08-14-19, 06:04 PM
Hood sound - vibration damping
but wouldn't the aluminum work as a radiant barrier and just deflect all the engine heat back into the engine bay and heat from the sun back up onto the hood?
