feb 47 Posted June 6, 2006 The following experiment was done in a private test track I wanted to measure the air intake temperatures so I fitted a digital thermometer to the car with the remote temperature sensor in the engine bay next to the K&N filter. It is interesting to see the rate of change of temperature rising/dropping very steeply when stopped/rolling. Ambient temperature was around 22-23C. Start the car and rolling, speeds up to 45 mph, the air temp is between 23-25C. After about 6 minutes of driving I stop for about a minute, the temp rises to 35C (water temp in 3rd line). I start rolling again and the temperature drops to 26C in less than a minute. I continue driving from 20-110mph and the air temp is between 23.9-25C. I then stop and wait for the fan to cut in, crawling every now and then to simulate traffic jam conditions. The temperature starts to rise, ranging between 30-39 most of the time, going up to 44 when the water reaches the 4th line (90C). I continue to start/stop moving only a couple of meters each time in first gear for around 15 mins, the air temp rises slowly to 58C going up to 64C, staying around 58 most of the time. Rolling at 30mph again and the temp drops to 26 within less than a minute. The purpose of this was to find out if high inlet temps make the car ping with the K&N sucking hot air. This used to be the case after sitting for long time in traffic and pulling over, pinging would happen around 2k until i started rolling then everything would be fine. Ever since i changed the spark plugs though the pinging hardly ever happens only sometimes when inlet temps are as high as 60C. Previous spark plugs have done 11k miles and looked ok. It would be interesting if someone could record their inlet temperatures with different setups: - original 205 airbox - throttle bodies/carbs with lowered radiator and heat shield between trumpets and radiator. - throttle bodies with airbox Cheers Share this post Link to post Share on other sites
crogthomas 0 Posted June 7, 2006 What sort of thermometer did you use? Share this post Link to post Share on other sites
feb 47 Posted June 7, 2006 What sort of thermometer did you use? i just used a digital one with in/out sensors. you can get one from bq or an auto store. not sure how accurate it is Share this post Link to post Share on other sites
crogthomas 0 Posted June 8, 2006 I think I know what you mean. Like this? http://i5.photobucket.com/albums/y190/crogthomas/temp.jpg They seem reasonably accurate, but can take a while to stabilise and read a temperature correctly. There is a lag. For example, put the sensor in a freezer at about -20C and it will take a while (maybe a minute or so) to reach -20C on the display. Its not the air in the freezer cooling down slowly since it is already at -20, but the sensor on the thermometer cooling down slowly to match its surroundings. I will try it on my standard GTi intake system if you like? Share this post Link to post Share on other sites
feb 47 Posted June 11, 2006 I think I know what you mean. Like this? http://i5.photobucket.com/albums/y190/crogthomas/temp.jpg They seem reasonably accurate, but can take a while to stabilise and read a temperature correctly. There is a lag. For example, put the sensor in a freezer at about -20C and it will take a while (maybe a minute or so) to reach -20C on the display. Its not the air in the freezer cooling down slowly since it is already at -20, but the sensor on the thermometer cooling down slowly to match its surroundings. I will try it on my standard GTi intake system if you like? yep, sth similar. yes if you could try it on the standard system it would be great. KN is not for hot climates as there is not much air flow. Share this post Link to post Share on other sites
inferno 1 Posted June 11, 2006 (edited) the best way to do this is with a snap on monitor plugged into your ecu i would of thought? it takes readings direct from your inlet temp sender. on my zx turbo i tried this to see how efficient the intercooler i modified was, sitting still at 56 degrees intake temp to start with, rev it a little and no pinking but rapid drops to 26 IIRC in less than a minute! didnt do such a thorough experiment as u did mind. this was with a k n n filter also inside the engine bay very neer the rad when the fans had just turned off, so sucking in the hottest air in traffic conditions with no airflow over the intercooler. this could suggest that a small intercooler may improve performance on an NA car... Edited June 11, 2006 by inferno Share this post Link to post Share on other sites
24seven 104 Posted June 11, 2006 (edited) It would only have minimal gains on an NA car. Your probably better off fabricating a custom heat shield keeping warm engine bay air away from the filter. This picture is of a custom one someone had made for his Almera GTi. Looking at it, this particular one probably doesn't do all that much, but if better designed with some insulation on the non filter side, I'd imagine it would probably help. If you were prepared to go totally overboard you could fabricate a sort of enclosure around the filter that draws air in only from around a vent in the wing or bonnet and from under the car, but if you were going to do that you may as well keep the standard air box and just use a more free flowing filter. Edited June 11, 2006 by 24Seven Share this post Link to post Share on other sites
inferno 1 Posted June 11, 2006 i did notice a difference in performance after lagging my turbo intake and boost pipes, but again the gains on a turbo car are likely to be higher than in an na, as said above. the drop in temp in a charge cooler is dependant on the difference between the ambient and charge air temp, ie the hoter turbo charge and common ambient will have a bigger effective power increase than a lower temp intake on a NA car useing a cooler in the same ambient... hope this makes sense... Share this post Link to post Share on other sites
24seven 104 Posted June 11, 2006 Turbochargers see a greater benefit from an intercooler because the intercooler allows teh turbo to run more efficiently, as well as providing cooler air. Basically the turbo compresses the air, and Boyle's law dictates that for a given mass of a gas, decreasing its volume increases its pressure and increases its temperature. using an intercooler, this compressed air can be cooled back down to nearer ambient temperature (or lower), thus reducing the temperature and pressure. this reduction in pressure means the turbo itself is less backed up (less back pressure) and so it is able to run more efficiaently. Share this post Link to post Share on other sites
crogthomas 0 Posted June 17, 2006 Well I tried to replicate your experiment as closely as possible. I placed the temperature sensor hanging inside the air intake snorkel behind the grill on a 1.9 Gti with a standard intake system. Ambient air temperature was higher than when you did it, so perhaps its better to work out the temperature difference. Either way it seems quite clear that the K&N filter is getting a lot more hot air than the standard set-up, as expected. I suspect that the radiator fan actually helps drag hot air away from the air intake on the standard set-up, but is actually forcing hot air toward the K&N, which is on the exit side of the radiator. Ambient air temperature = 27.5C 45mph driving = 25.0C Stopped for 1 min = 28.9C B road driving low to high speeds = 24.2C Stop and wait for 15min, 47.2 C is the maximum before fan kicks in. 30 mph driving = 24.8C Share this post Link to post Share on other sites
