Heat Soak Your thoughts

[RedDjinn]

I will be chatting to my panel beater about this

[Yeldarb]

Had a look under a GENII bonnet. Under the insulation there is a small area in between the ribs of the bonnet where you might be able to get some louvers cut in, but as I don't appreciate the capabilty of the machine press that can do this, it's probably necessary to cut out some of those ribs to make a decent amount of space.

Another good location would be behind the TMIC shroud, all the heat from the downpipe could just pour out the top, but there isn't a great deal of room between the shroud and the lip of the firewall.




This would be the locations if you went this way.

[MadAussie]

If I recall correctly there's a mob in Kenwick (Perth) that does louring.

I'm going to look into it.

[Doug_MPS6]

One aspect overlooked is that of what is termed "cooling drag". That strip behind the bonnet is not just to keep water out or pretty-up the gap, it is to reduce airflow through the engine bay, keep it outside the engine bay and over the bonnet as much as possible and hence improve aerodynamics. Opening it might get hot air out but will increase what in aerodynamic terms is referred to as cooling drag. It is up to you which devil you hate most - drag or heat.

The reduction in bonnet apertures in modern cars, including the radiator grille, is mostly about cooling drag reduction, as well as reduction in form drag - the drag created by a specific shape as it is presented to the airflow. Hence the modern tendency to dropped bonnet, small grilles lines and inclined or V-configuration engines to fit smaller and shorter engine bays, along with under-pan shrouds, for improved aerodynamics.

I've spend ages tweaking aircraft to reduce drag where it is far more critical to aircraft performance, and there are 3 types of drag, being lift, form and cooling drag. The latter can be a significant part of the overall drag equation.

[bd581]

Not sure if you have seen it Luke, there is a MPS bonnet for sale on the ozmazdaclub fb page. For the right price it could be good to experiment with

[Byrd]

I agree with Doug, you can't just cut a few louvres here and there in your bonnet and expect it'll do "something", these intakes require specialised engineering and testing to actually do any good.

[RedDjinn]

Had a look under a GENII bonnet. Under the insulation there is a small area in between the ribs of the bonnet where you might be able to get some louvers cut in, but as I don't appreciate the capabilty of the machine press that can do this, it's probably necessary to cut out some of those ribs to make a decent amount of space.

Another good location would be behind the TMIC shroud, all the heat from the downpipe could just pour out the top, but there isn't a great deal of room between the shroud and the lip of the firewall.




This would be the locations if you went this way.

Best place is also the hottest! need these to go in above the mani and turbo. Thansk BTW for digging

[RedDjinn]

If I recall correctly there's a mob in Kenwick (Perth) that does louring.

I'm going to look into it.

Look forward to the reply

[RedDjinn]

I agree with Doug, you can't just cut a few louvres here and there in your bonnet and expect it'll do "something", these intakes require specialised engineering and testing to actually do any good.

I have a AP @Rayd has my logs, before and after will be the decider. If no one try's than it wont go anywhere....

[son of eevil]

I have a AP @Rayd has my logs, before and after will be the decider. If no one try's than it wont go anywhere....

I'm very interested to see how you go with is and I'll follow closely.

One aspect overlooked is that of what is termed "cooling drag". That strip behind the bonnet is not just to keep water out or pretty-up the gap, it is to reduce airflow through the engine bay, keep it outside the engine bay and over the bonnet as much as possible and hence improve aerodynamics. Opening it might get hot air out but will increase what in aerodynamic terms is referred to as cooling drag.

Would you expect an expedition in louvring to produce positive of negative results taking into account the possibly of increased power (probably single digits of KW) and the erxtra drag created by it?

[spooon]

Would you expect an expedition in louvring to produce positive of negative results taking into account the possibly of increased power (probably single digits of KW) and the erxtra drag created by it?

Interesting question; I think it would be hard to tell, it would depend on few things like the size of the opening, the volume of air coming out, the tempture etc. Speed would also have a factor too generally in cars anything above 120km/h aero has a more considerable effect. I think drag increases would be in the single digit of overal % drag anyway. It would be one of those pro vs. con type things, as I would think having a few openings to let out would help reduce underbonnet heat, esp if you're running a big turbo (which, in theory is offseting any drag increase with power )

I suck at explaning aero though

[Yeldarb]

I wouldn't do this solely for power. Any benefits like that would be a bonus. Cooler air passing around the engine must be a good thing.

If we're talking about louvers though, you wouldn't expect too much extra drag... As the louvers are facing back, it's the negative pressure drawing the air out while in motion.

I would do this solely to let heat out while stationary, which is where I think Luke is going.



Sent from my GT-N7105 using Tapatalk

[shaneski]

Wouldn't the louvers actually suck air in to cool motor while at speed, similar to a SLR5000/A9x bonnet scoop when you look at it you think whats the use of it hows air going to get in there, but the air at highspeeds fold into it and and ram the air into the carby. I have noticed there are many louvered bonnet cars at APSA drag racing lately (twin turbo v8 cortinas and a few early mustangs) i doubt they do it for traffic as they don't actually start the cars up after being to towed to stage before the burnout.

[RedDjinn]

I'm very interested to see how you go with is and I'll follow closely.



Would you expect an expedition in louvring to produce positive of negative results taking into account the possibly of increased power (probably single digits of KW) and the erxtra drag created by it?

Doubt it would be a HP mod. The benifit would be at idle around town, If you can suck the air out while moving would be a plus! As for drag it would only be a issue like 250kph+ who teh hell woudl b looking at there speed at that speed

[son of eevil]

Isn't the goal to promote airflow to reduce engine bay temps so you can get lower BATs which in turn allow you to run more timing advance?

My understanding is that as heat rises out through the bonnet it creates a low pressure system that draws more air into it and out at all speeds?

[spooon]

Sort of... This is where I suck at explaining aero, cooling drag can actually increase pressure infront of the car (at the point of opening) say, at the radiator grill... And without being able to wave my hands in the air and make wooshing noises I suck at explaining the rest. (Doug... Help!!)

Sent from my HTC Velocity 4G using Tapatalk

[spooon]

Also I would be looking to reduce under bonnet temps as a way of reducing a contributing factor in knock/ping. More of a reliability thing then chasing timing advance

Sent from my HTC Velocity 4G using Tapatalk

[Yeldarb]

I'm with you @spooon

Sent from my GT-N7105 using Tapatalk

[GibbA]

Also I would be looking to reduce under bonnet temps as a way of reducing a contributing factor in knock/ping. More of a reliability thing then chasing timing advance

Sent from my HTC Velocity 4G using Tapatalk

Certainly agree with this. In terms of faster response once heat soaked and reliability I'd say would be the goal.

Sent from my Nexus 5 using Tapatalk

[Oldhead]

One aspect overlooked is that of what is termed "cooling drag". That strip behind the bonnet is not just to keep water out or pretty-up the gap, it is to reduce airflow through the engine bay, keep it outside the engine bay and over the bonnet as much as possible and hence improve aerodynamics. Opening it might get hot air out but will increase what in aerodynamic terms is referred to as cooling drag. It is up to you which devil you hate most - drag or heat.

The reduction in bonnet apertures in modern cars, including the radiator grille, is mostly about cooling drag reduction, as well as reduction in form drag - the drag created by a specific shape as it is presented to the airflow. Hence the modern tendency to dropped bonnet, small grilles lines and inclined or V-configuration engines to fit smaller and shorter engine bays, along with under-pan shrouds, for improved aerodynamics.

I've spend ages tweaking aircraft to recue drag where it is far more critical to aircraft performance, and there are 3 types of drag, being lift, form and cooling drag. The latter can be a significant part of the overall drag equation.

Always a wealth of of knowledge ,your the man DougMPS6. Aussie climatic conditions are hugely variable and high temps tend to be the norm ,we all are aware that high temps are the killer of HP ,oil, and engine components and it would seem especially for us living in most areas of Aus that if tweaking correctly or as best as possible any area to lower engine bay temps would be somewhat beneficial ,but to what degree is open to discussion. I agree that aerodynamics has been a huge part of modern design ,(fuel usage ,drag, etc) but im yet to see a modern car fly. Placement of vent/louvres would need to crucial NOT asthetic .