Whittie Posted February 18, 2009 Share Posted February 18, 2009 Hey guys, I’ve had a persistent high engine bay temperature problem at the track and after a few other mods it's not going away. I've coated the extractors inside and out with a ceramic coating and flushed the cooling system with 'cooling system cleaner' and whilst this helped it has not removed the problem. The big issue is that the Triple Weber’s draw air straight from under the bonnet and so I need to get this hot air out of the engine bay. I've been giving it some thought and what I think what I need is more airflow through the radiator and cooler air to the air filters. What I was thinking then is to put some bonnet vents in place to get air into/out of the engine compartment. The issue I have now is that I have read quite a few write-ups and can't decide what is the best course of action: A) put 2 bonnet scoops in to feed cool air to the filters and then test again to see what the result is. Or, put air vents in at the front of the bonnet (approx 1/3 from the front, one on each side) in the low air pressure point on the bonnet to draw hot air out of the engine bay, promoting airflow and cooling the engine compartment. The one thing I can't get an accurate answer for is the best type and placement of vents. Should I put vents in 1/3 of the way from the front of the car, or some scoops directly above the air filter to direct airflow in? Also, what should I cover in the front to direct air to the radiator. Obviously, sealing the radiator and the air dam so air can't travel around gaps close to it, but what about those circular wholes where the air con vents come in from the front of the car. My z doesn’t have the vents, just the holes in the front structure, should I close those off? Any and all help is appreciated. Tom. Quote Link to comment Share on other sites More sharing options...
MJLamberson Posted February 18, 2009 Share Posted February 18, 2009 If I read that right I suggest you find yourself a 77-78 280z hood, they had two fully functional vents right out of the factory. back when I had that hood on my Z you could actually see the heat rising out of them! Quote Link to comment Share on other sites More sharing options...
deja Posted February 18, 2009 Share Posted February 18, 2009 I agree, I can see the heat coming out of my vents. The down side of course is it also allows water in when its sitting in the rain or washing the car. If I read that right I suggest you find yourself a 77-78 280z hood, they had two fully functional vents right out of the factory. back when I had that hood on my Z you could actually see the heat rising out of them! Quote Link to comment Share on other sites More sharing options...
Whittie Posted February 18, 2009 Author Share Posted February 18, 2009 Heat coming out at idle is one thing, what i really need is for the hot air to be pushed/pulled out of the engine bay at high speeds (+60mph when its a problem with the temp guage not going down whilst racing) From memory they had one vent on either side of the bonnet near the back right? From what i have read, that seams to be a high pressure point at speed, effectivly stalling any air flow that was being encountered at idle... I think i need to do some aero-testing with string tied to the bonnet of my car to see what the results are Quote Link to comment Share on other sites More sharing options...
MJLamberson Posted February 18, 2009 Share Posted February 18, 2009 You mentioned it being at the track, why not run your car with the hood popped open, but so its still latched (obviously)? Quote Link to comment Share on other sites More sharing options...
Whittie Posted February 18, 2009 Author Share Posted February 18, 2009 Illegal. Bonnet has to have two safety mechanisms and be locked to be allowed on the track. You would get black flagged pretty quick for an open bonnet. From what i have read i get mixed stories but more people seem to think that where the heater inlet ducts are located (end of the bonnet) is at a high pressure area. This high pressure would prevent the air under the bonnet from flowing out. What i really want to know is what type of vent/scoope to install, where best to put them and if they will do anything Quote Link to comment Share on other sites More sharing options...
280zx 2by2 Posted February 18, 2009 Share Posted February 18, 2009 they sell those extenders for honda hoods so the rear is open, it souldnt be to hard to make some for a Z since thats the way the hood opens... Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 18, 2009 Share Posted February 18, 2009 The high pressure is caused by the resistance of the windscreen. As to how far forward this high pressure extends would only be answered by testing. Put some tufts of string on it and go for a drive. (And stop using MPH, you're an aussie ). IMHO, I'd investigate putting the vents a few inches behind the raditor on the bonnet. The reason being at this point the air is still curving upwards and around the lip of the bonnet, ie. its flowing in essentially the right direction to pull air upwards and out of the engine bay after the radiator. Some small upwards ducting running from the bottom/rear side of the radiator upwards would also encourage this. Do you have radiator inlet ducting? Dave Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted February 18, 2009 Share Posted February 18, 2009 You can try putting some holes between the engine compartment and the fenderwell (air in engine compartment will flow into the wheelwells). I believe that George Costanza in the GA Z Club did this and added some fans to cool his V8 Z... I'd also think about building a box araound the inlets for the webers and duct cool air to them from the front of the car. This would insure the coolest air possible.... Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 18, 2009 Share Posted February 18, 2009 Brad, I thought the windtunnel tests indicated that the wheel wells are one of the main sources of drag in the front of an S30. If thats the case then the wheel well is already a pretty high pressure area, and thats unlikely to be very beneficial. Bonnet vents definitely work. Dave Quote Link to comment Share on other sites More sharing options...
capt_furious Posted February 18, 2009 Share Posted February 18, 2009 Nissan's initial early solution to underhood temps was a fiberglass fairing over a large hole smack in the middle of the hood. I can't find any photos, but it was similar in appearance to a cowl hood, with vents at the sides. Quote Link to comment Share on other sites More sharing options...
Whittie Posted February 19, 2009 Author Share Posted February 19, 2009 Thanks Guys. I think I'm going to go for a spin today with some string on the bonnet and see what happens. I'll try and find a navigator to take some photos as we go. Helix, i use MPH for the same reason i put "Hood" in the thread title, cause most Americans don't know proper maths or english.... Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted February 19, 2009 Share Posted February 19, 2009 Hehe.. true. Dave Quote Link to comment Share on other sites More sharing options...
Whittie Posted February 19, 2009 Author Share Posted February 19, 2009 There's another thread going here: http://forums.hybridz.org/showthread.php?p=990042 probably easier to keep all the chatter in one spot Quote Link to comment Share on other sites More sharing options...
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