Hood vents question?

[COMP]

Originally Posted by MrBig

You could also put some spacers where your hood attaches to your car. This will raise your hood near the windshield and allow some of the hot air to escape. I've seen drifters use this technique because of the extra heat from their turbos.
It's real cheap (just cost of spacers) and easy to do (& easily reversable if you don't like it).

true and some you can just remove the gasket

[holypaulie]

Originally Posted by MrBig

You could also put some spacers where your hood attaches to your car. This will raise your hood near the windshield and allow some of the hot air to escape. I've seen drifters use this technique because of the extra heat from their turbos.
It's real cheap (just cost of spacers) and easy to do (& easily reversable if you don't like it).

Not a good idea to raise the hood. The best air flow is when you have big difference is air flowing pressure. Area close to the windshield has high pressure almost same as is the front of the grill. Now area close to radiator has low pressure and that's the best spot for hood vent.

BLUE-->LOW PRESSURE
GREEN-->HIGH PRESSURE
RED--> THE HIGHEST PRESSURE

[ShadowWorks]

Hood vents either bring cold air into the engine bay or intake, or the provide a vent for hot air in the engine bay, I have lined and insulated my hood with aluminium foil that is to 100mm of rock wool, I do like the heat, the hotter the engine the less fuel it takes, I would say remove part of your grille block.

I have yet to make my grille block so I can understand if your worried about to little cooling.

[COMP]

Originally Posted by ShadowWorks

Hood vents either bring cold air into the engine bay or intake, or the provide a vent for hot air in the engine bay, I have lined and insulated my hood with aluminium foil that is to 100mm of rock wool, I do like the heat, the hotter the engine the less fuel it takes, I would say remove part of your grille block.

I have yet to make my grille block so I can understand if your worried about to little cooling.

what wool and foil ???

[GasSavers_BluEyes]

Originally Posted by ShadowWorks

the hotter the engine the less fuel it takes.

Nope. When running hot, engines are calibrated to run rich to help avoid preignition and to help cool the engine. Insulation will help speed warm-up and keep the engine warm when running errands however and this improves economy by reducing warmup time.

Regarding lifting the back of the hood, that does not exhaust air, it pushes more air under the hood. Musclecars have used this since the 60's, called cowl induction, to bring in higher pressure, cool air to make more power. Often special intakes are used that seal to the raised cowl area forcing the air into the engine. From an aerodynamics perspective, lifting the rear of the hood is very "dirty" as it causes MORE airflow through the engine bay and underneath the car.

No, Paulie has the right idea. A grille block reduces airflow through the engine bay, while a well placed hood vent redirects some of the airflow that is there under the hood back above the car instead of underneath. Not only will this help reduce drag but also reduce front end lift for more stable handling at high speed. If the hood vent is sufficiently large, a duct could be made to seal the vent to the radiator and redirect ALL cooling airflow out the hood, avoiding airflow over the non-aerodynamic engine block entirely. At that point, a grille block may be superfluous.

[ShadowWorks]

Originally Posted by BluEyes

Nope. When running hot, engines are calibrated to run rich to help avoid preignition and to help cool the engine.

Not on my engine, for example the hotter the coolant the leaner the fuel mixture gets as it uses a NTC sensor to monitor the warm up cycle, I have a knock sensor which retards boost using the waste gate, I have never had ping due to a hot engine, even when the coolant is at 98 degrees Celsius. If an engine is Pinging than something is wrong.

[COMP]

Shadowworks you see my question ??

[GasSavers_BluEyes]

Originally Posted by ShadowWorks

I have never had ping due to a hot engine, even when the coolant is at 98 degrees Celsius.

Makes sense now. That's because 98c/208F isn't running hot, it's just on the high side of normal. After all, you could technically run straight water coolant at those temps. I would expect to see an efficiency gain at that temp if your OE spec thermostat is a cold one like 185 or even 175F.

Many cars don't even turn on the cooling fans until 220F/104.4c but you may see some pinging there on cars with no knock sensor depending on engine speed/load. You won't hear knock if there is a knock sensor, but the reduced timing will hurt efficiency. Stuff like hot enrichment and timing retard are really hitting when the engine gets hot like 230F/110c.

[ShadowWorks]

Originally Posted by COMP

what wool and foil ???

Sorry I missed that, it's not actually wool, Its thermal insulation called type 2 foil insulation in the house building trade, its basically super thick bubble wrap with two foil layers on each side, this has the same thermal value of 100mm of wool.

It reduces sound from the engine bay and helps the warm up time of the engine, it also helps the engine say warmer for longer after its been shut down.

[COMP]

Originally Posted by ShadowWorks

Sorry I missed that, it's not actually wool, Its thermal insulation called type 2 foil insulation in the house building trade, its basically super thick bubble wrap with two foil layers on each side, this has the same thermal value of 100mm of wool.

It reduces sound from the engine bay and helps the warm up time of the engine, it also helps the engine say warmer for longer after its been shut down.

thanks,,, I have some of that bubble foil