Drax240z Posted March 16, 2006 Share Posted March 16, 2006 Now' date=' how did you slip that in there without an edit showing up??? I could swear there was no other reply after z-ya [/quote'] Being a mod has some privledges. Quote Link to comment Share on other sites More sharing options...
Doug71zt Posted March 16, 2006 Share Posted March 16, 2006 Moby - The big concern with Alky seems to be that the IAT sensor isn't really constructed to be sprayed with liquid, at least the GM version. I'm not sure about MS using the IAT during Alky injection - I'm just lurking and learning about MS as some people have been asking me to install and tune for them. I figured that I'd better learn something about it before that happens.... Austin - I don't think that distribution would be that great to cylinder #1 in the cold start hole. Doug Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 16, 2006 Share Posted March 16, 2006 Moving the IAT sensor upstream of the TB in a IC pipe will just give the ECU false air temp readings. This is because the air in the IC pipe before the TB is much cooler than the air in the plenum. Make sense? If you are having heat soak problems when the IAT sensor is in the plenum, then your air tempreature compensation algorithm is out of calibration for some reason. The sensor needs to be as close to the intake port of the head for maximum accuracy, period. The ECU will compensate for any extreme intake temps so that heat soak never happens. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted March 16, 2006 Share Posted March 16, 2006 So it seems that the arguement over placement has boiled down to a comprimise between heat soak and placement as close to the cylinder as possible. Right before the TB being the best place for the least heat soak. And middle of the intake manifold being the best overall location with possible heatsoak. I guess my question/statement in line with z-ya would be: It seems that the time of most concern for IAT is under boost, and it follows that under boost there will not be any heat soak issues because so much air is moving by (and has been for some time). I believe the heat soak issues only happen after the car has set for a few minutes and you fire it back up, or maybe sitting at idle for a period of time. Ideally we would have an IAT on every intake runner just before the injector and a wideband on every exhaust manifold runner. The question still remains for water injection: Will water/alky mixture damage the GM IAT sensor? Does anyone have proof of that? Has someone been running for a while with water/alky injection hitting the sensor? Being a mod has some privledges. - Quote Link to comment Share on other sites More sharing options...
tannji Posted March 16, 2006 Share Posted March 16, 2006 So, given your summary, if I were to use a Phenolic Spacer between the head and the Plenum, I could probably run the IAC in the plenum? And as far as the H2O/Alchy injection, if indeed it will damage the IAC, next best spot for IAC would be in a Phenolic Spacer between the plenum and the throttlebody? For my application with the crossflow 2RZ, I dont have exhaust mani under the plenum, so I am thinking I would be able to get away with something like this. I am just a little confused on how you can run the IAC before the injection, and not have problems with the sensor temp versus intake temp due to the H2O/Alchy injection? Quote Link to comment Share on other sites More sharing options...
Drax240z Posted March 17, 2006 Share Posted March 17, 2006 For my use, there was no comparison between results. I had very erratic AFR's from run to run on my dyno with the air temp sensor near number 6 runner. In 3 runs back to back I would see a varience of 0.5-0.75 points of AFR. (ie: 10.5:1 one run, and as different as 11.25:1 the next) Over 20 or so dyno runs back to back the results were staggeringly inconsistant, torque and power we as inconsistant as the AFR's as well, as would be expected. I talked to Ross a bit at SDS, and he said he'd seen it before with the L-series, and that I'd get a much more stable reading with my temp sensor just before the TB in my cold pipe. Now in ~20 dyno runs back to back I can throw a blanket over my AFR's, they are that consistant. The temperature profiles for most of these EFI setups (including the SDS) are adjustable, and mine would not dial in at all in the previous heat soaked state. It was a piece of cake to do this time with the air temp sensor before the TB. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted March 17, 2006 Share Posted March 17, 2006 sensor near number 6 runner So that location may not work then. Sounds like somebody needs to log AFRs with megasquirt and see if the middle of the plenum works better. A good experiment would be to log AFRs and move the sensor from the "pop off runner 6" location to middle of plenum and then before the TB and see if you get results like Drax's and then put up the graphs so we can all look over them. Who is up for that? Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 17, 2006 Share Posted March 17, 2006 I talked to Ross a bit at SDS, and he said he'd seen it before with the L-series, and that I'd get a much more stable reading with my temp sensor just before the TB in my cold pipe. Now in ~20 dyno runs back to back I can throw a blanket over my AFR's, they are that consistant. The temperature profiles for most of these EFI setups (including the SDS) are adjustable, and mine would not dial in at all in the previous heat soaked state. It was a piece of cake to do this time with the air temp sensor before the TB. Sounds like SDS has an issue with their air temp compensation. Or, because the intake is getting so hot that it is beyond the scale of the sensor (unlikely). By moving the IAT sensor, you are fixing the symptom, not the problem. Moving the sensor is compensating for some calibration error. An example of why the sensor needs to be in the intake manifold after the TB: Under heavy acceleration in a boosted application, lots of air is flowing through the system, so the IAT in in the IC pipe will give you an accurate reading. But as soon as you let off the throttle, the throttle plate slams almost shut, cutting airflow through the system. In this instance, the air in the IC pipe is MUCH cooler than the air in the intake, but it is the temp of the air in the intake that is important to the ECU. I have seen this behavior, and if the air temp compensation is not correct, the engine will stumble a few seconds after the throttle plate closes. The is due to the fact that now the AF ratio is wrong for the given intake air temp. Once the throttle is opened up a bit, and the temperature drops, the stumble goes away. I have seen the temp jump over 10 deg C (50 F) after a full boost dyno pull. After making a correction to the air temp compensation, the problem went away. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted March 18, 2006 Share Posted March 18, 2006 well i'm running mine about 6" after the air filter on a custom CAI I welded up. I have no problems thus far, however my milege is still low, maybe this could be a possible reason? Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 19, 2006 Share Posted March 19, 2006 Yes, it could be causing it to run rich, but if you have dyno tuned it, it would have compensted for the location of the IAT. Quote Link to comment Share on other sites More sharing options...
Nismo280zEd Posted March 20, 2006 Share Posted March 20, 2006 well the whole motor is out of the car being rebuilt now, maybe once it's running stable Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 27, 2006 Share Posted March 27, 2006 Mine's exactly where Warren's is, in the space behing the T/B, right behind the throttle shaft, no airflow disturbance there. As for mounting it before the turbo, if you are intercooled perfectly, or even decently, it "shouldn't" make that much a difference. But on a stock setup, you will have some serious density issues as the intake air on even a 60F degree day can be 20 to 40 degrees hotter, depending on speed. I'd not recomend that position to anyone. Quote Link to comment Share on other sites More sharing options...
badjuju Posted March 27, 2006 Share Posted March 27, 2006 I'll post a pic, I just put mine in this week; I put it in my lexxan spacer, drilled two holes of different sizes, one all the way through for the actual element, then one 5/8" about halfway down, then put blue gasket stuff on the inside and screwed my iat sensor in. We'll see how it works as i tune. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted March 28, 2006 Share Posted March 28, 2006 mine is on the cold side tank of the ic.i drilled a hole and threaded .its kind of hidden. Quote Link to comment Share on other sites More sharing options...
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