Nigel Posted June 21, 2004 Share Posted June 21, 2004 Hi all... I haven't posted in ages, so just as a reminder, I have a 240Z Turbo with an SDS EM3-6F system (yesterday I did a 13.9 1/4 mile, and placed 2nd in the eliminations on my second try at drag racing!). Anyway, my question is this, and I think it's pretty simple... When intake temperature goes up, the SDS systems leans out the mixture, correct? I figure that hotter air being less dense will therefore need less fuel to maintain the same air/fuel ratio, at the same pressure. The reason this is on my mind is that I have my temp sensor (the optional 1/8 NPT Dale sensor) screwed into the intake manifold right between runners 3 and 4 (where the stock fuel pressure regulator vacuum line fitting used to be), and at idle my intake temps are soaring to 60+ deg C and the engine starts running very lean! Plus, when I'm on the highway, I'm seeing intake temps of ~39C when the ambient temperature is ~19C , for example. So I obviously need to move the sensor... I guess to the J pipe... but how do I mount it so the sensor is thermally isolated? Nigel Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 21, 2004 Share Posted June 21, 2004 Hi Nigel. I am running a EM-3E and have put my air temp sensor right at the back of the intake manifold, next to the brake booster vacuum line. I don't notice any lean conditions as a result of this, except in closed loop mode. (I assume yours is off?) To thermally isolate the sensor from the manifold, just use 3-5 wraps of teflon tape as you would on any other pipe thread. Teflon doesn't conduct well at all. Are you using any sort of heat shielding under your intake manifold? That would be what I suspect is the problem. You need one... especially with the sensor in that position. My intake temps at idle don't seen to get over about 40-50C if my memory serves me. Cruising temps will always be higher than ambient, 20C higher doesn't strike me as alarming. Quote Link to comment Share on other sites More sharing options...
Nigel Posted June 22, 2004 Author Share Posted June 22, 2004 I drove the car to work today, and at lunch I pulled the j-pipe, drilled a hole in it, stuck a rubber grommet in the hole and screwed the temp sensor into the grommet. So, now my temp sensor should be getting a more accurate read on the air temperatures. I did notice significantly different behaviour in the air temps. The response is faster. For example, the temperature drops faster now when going from stationary to moving. Plus, I'm now seeing temperatures of 34 - 37C cruising on the highway instead of 39 to 42C at 19C ambient. And yes, I have a big heat shield under the intake manifold with a layer of that Thermotec heat blanket stuff. To elaberate more on what's got me thinking about all of this, is I finally got my Techedge wideband meter installed, so I can now see what's really going on. I'm seeing changes in AFRs that I believe are due to air temp changes, because all else is remaining the same. For example, when idling, I can see the AFR's go from 12.5/1 to 14/1 as the intake temps climb. Yesterday, after driving on the highway for about 2 hours, I stopped for a quick break. When I started the car up again, the air temp showed 70C and AFR's were showing ~18 to 1! SDS used to allow you to adjust air temp compensation, but they eliminated it because too many people were screwing that part up. I'm beginning to wish the left it in, because now with the WB, I can see just how much it affects AFR's, all else being equal. Hence, my quest to give the sensor the best reading on the air temps possible. Nigel Quote Link to comment Share on other sites More sharing options...
Drax240z Posted October 7, 2004 Share Posted October 7, 2004 Some more info here... I finally got around to wideband tuning and have noticed the same thing. Before with the narrowband O2 sensor it wasn't noticable at all on the AF meter. I talked to Ross at SDS and this was his reponse: We recommend mounting the a/t sensor in the intercooler discharge pipe before the TB as this involves less heat soak problems and faster change due to higher local mass flow. L series engines have issues with fuel heat soak due to the proximity of the fuel rails to the exhaust radiation. This causes decreased fuel density and altered AFRs which the ECU cannot compensate for. Moving the a/t sensor may help quite a bit. Aluminum fuel rails are a bad idea on these engines in particular. I think I am going to move mine as Ross has suggested. I'll try to remember to add to this thread once I've done that and can compare results a little. Quote Link to comment Share on other sites More sharing options...
Guest 1SickZ Posted November 8, 2004 Share Posted November 8, 2004 do you guys have part # for the sensor you are using. i cant seem to find one. thanks. Quote Link to comment Share on other sites More sharing options...
Nigel Posted December 27, 2004 Author Share Posted December 27, 2004 Drax240Z... I recently discovered that you can change the air temp map! Ross faxed me the instructions. It involves jumpering two pins on one of the connectors on the ECU. I'm going to try accessing the map sometime this week. However, the Z is off the road for the winter, so it's going to be a while before I can see if it actually helps. I'm also going to do some additional heat shielding to see if I can cool down the fuel rail. 1SickZ... I'm just seeing your post now. Which sensor are you talking about? Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
Drax240z Posted December 27, 2004 Share Posted December 27, 2004 Hey Nigel, any chance you can forward that info to me? I am not sure I need it as of yet, but it would be nice to have if I do. Quote Link to comment Share on other sites More sharing options...
spork Posted December 27, 2004 Share Posted December 27, 2004 actually, if you would post that info on here if you can, that way anyone can get to it if they need to. If not, just emial it to me as I'd like to have it on file. datsun280zxt@sbcglobal.net James Roraback Quote Link to comment Share on other sites More sharing options...
Nigel Posted December 27, 2004 Author Share Posted December 27, 2004 Ok guys, I'll try to post it sometime today (I don't have it handy at the moment). Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
Nigel Posted December 27, 2004 Author Share Posted December 27, 2004 Ok, I've got the instructions for accessing the Air Temp Map, and I've personally tried it out. Before I give you the instructions, PLEASE NOTE: Ross disabled the Air Temp Map access for a reason. People were messing with it and screwing everything up. So, you should only play with the Air Temp maps if you are experienced with the SDS system and you've gone as far as you can adjusting all the other parameters. I don't want Ross cursing my name because I gave out this information and now everybody is contacting him because they've made a mess of their Air Temp maps and their engine won't run right! Also, the instructions I am going to give involve jumpering two pins on an ECU connector. You do this AT YOUR OWN RISK! If you screw it up and fry the ECU (unlikely), it's your own fault! Finally, these instructions are titled EM -3 Setup Mode. I don't know if the same instructions are relevant for the EM -4. Here we go... EM -3 Setup Mode AIR TEMP ACCESS Unplug hall sensor plug from ECU. Power up the ECU with the programmer plugged in. Momentarily (1/2 second) short out pins 6 & 7 on the hall plug port on the ECU using a wire or setup tool (provided by SDS). You will see SETUP TEMPSENSOR in the programmer window. Push the > 4 times until you see SETUP AIRTEMP. Push the +1 button once to get AIR TEMP ACCESS Push +10 to exit setup mode. That's it. The Hall Plug Port is the DB 9 female connector in between the DB 9 male programmer connector and the DB 25 harness plug. The location of my ECU makes the connector difficult to jumper, so I pluged a serial cable (male to female - and make sure it's not a crossover cable) into the Hall Plug Port and used a paper clip to short pins 6 & 7 on the female connector at the other end of the cable. Once you exit setup mode, you're back to the regular program screen. The Air Temp Map is now there just like all the other maps for RPM Fuel, ManPress, etc. Just scroll through the screens until you get the Air Temp Map. So we have it on record, here's the default Air Temp Map (perhaps someone could verify this)... -50C 130 -40C 112 -33C 100 -26C 96 -19C 92 -15C 88 -10C 86 -8C 84 -4C 82 -2C 81 2C 80 4C 79 6C 77 8C 76 11C 74 13C 73 15C 72 17C 71 19C 71 21C 70 22C 70 24C 70 26C 69 28C 69 29C 69 31C 69 33C 68 34C 68 35C 68 37C 68 39C 67 41C 67 42C 67 45C 67 46C 66 48C 66 50C 66 52C 65 53C 65 56C 64 58C 64 60C 63 62C 63 64C 62 66C 62 68C 62 70C 62 73C 61 76C 61 78C 61 81C 60 85C 60 88C 60 91C 59 95C 59 100C 58 105C 58 110C 57 118C 56 125C 55 135C 53 148C 50 170C 48 190C 46 Nigel '73 240ZT Quote Link to comment Share on other sites More sharing options...
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