Hey guys I talked with JR over at Team ZR-1 yesterday evening and he seems to know a great deal about what he is doing tuning wise so if you are looking for someone I would go over there. But there was one thing he mentioned about my MAF/IAT sensors. I have a 2000 Silverado which means the MAF and IAT sensors are mounted together in the same body. Now I have a Whipple blower on the truck and as we all know and kind of compression blower will obviously make the air coming in hotter. To make a long story short, my MAF/IAT sensors are mounted on the airbox, which is BEFORE the blower so logically the sensors for both will be registering BEFORE compression. SO, I figured the IAT would be way off and so will the MAF. I know you can adjust for the MAF but I was wondering if the IAT being different would affect the timing and detenation, because the PCM will think it is 80deg intake temp and it is really 100-120deg, therefore it is not adding enough fuel. Any comments or suggestions would be appreciated on this issue. Thanks!!
<img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />

 

I'd imagine the maf would still read right, since the same a mount of air has to be pulled through it as what's being pushed into the motor. But I see you're point on the IAT sensor. Ls1Edit will let you increase the IAT values, so you could 'shift' the stock table down the rpms some. Or you could maybe stick a resistor inline with the sensor, assuming more resistance=hotter air.

 

You could snip the two wires going to the IAT sensor in your Mass air meter and then get an IAT from a camaro/firebird. Connect it to the two wire that you snipped, and you could place that IAT sensor anywhere. The computer will now see your added IAT sensor and not the 'whipple' hot one.

 

Ewww, there's a nasty problem.

I did some digging into Edit, and the only real differences that I could find are timing. If your intake charge is 40 deg F hotter, then your timing will be advanced +3 more than it should leading to KR. However, with the 40 deg F hotter intake charge, fuel is only bumped up ~4% (from what I could find).

I think that your MAF will be more accurate prior to the whipple. The air flow will be straighter. The velocity of the air might be higher than what the MAF was calibrated for, so there is a good chance that alot of air is getting by that it isn't "seeing". The higher the velocity, the more induced turbulent flow, the less straight the air yadda yadda.... I think.

I would keep the MAF where it is, and just move the IAT sensor to the appropriate place. Then use Edit and recal your MAF.

Just my suggestion

Good Luck
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

OK another question is if I moved the whole MAF/IAT assembly would the boost be too much for the wires to handle from a physical standpoint or from a "too much air to register" standpoint? What you guys think???

<img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

 

Well, all the fbody FI cars are blowing through the maf, so unless it's a different maf it should work. But how does the whipple mount on a truck? If it's like other whipple I've seen, it mounts in place of the intake. Gonna be hard to put the maf between that and the heads.

 

Well, all the fbody FI cars are blowing through the maf, so unless it's a different maf it should work. But how does the whipple mount on a truck? If it's like other whipple I've seen, it mounts in place of the intake. Gonna be hard to put the maf between that and the heads.

 

No it has like a little tube that goes from the blower to where the throttle body was and that's where it goes into the intake. Perfect place to register AFTER whipple IAT and MAF. BTW, do you guys think that this would be a big enough factor to cause me to get 3-4deg of KR????

<small>[ August 13, 2002, 07:50 PM: Message edited by: Will ]</small>

 

I think the iat is only for timing advance/unadvance? When it is running hotter the timing would be lower.

The maf senses air by heating the little wires that hang in the air flow area, and then when air is pulled by them it cools them a little. If that’s true (which I’m not sure of) the hotter air, the more the maf would be off on the amount of air it’s detecting.

I have only been around a few FI cars, so I really don’t know that much about them. I would say the maf would work better befor the blower if the maf/pcm was tuned for it.

On ls1's web site the pic's of the bowers show the maf before the supercharger

Here’s a picture
http://www.ls1speed.com/catalogimages/vortech_ls1.gif

<small>[ August 13, 2002, 09:10 PM: Message edited by: dissonance ]</small>

 

anyone else think it would help very much to move it after the blower? CHRISB I would appreciate some commentary from you PLEASE?!!?

 

will, there may be a problem with moving the IAT sensor, not sure who told me this but they thought that the IAT would be maxed out most of the time if it was placed after the blower, the table in ls1edit only goes to something like 190deg. if it was pegged at 190deg all the time it wouldn't do much good either.

on my truck i am in a part of the timing curve where it only asks for 6-9deg of timing and if the IAT was seeing high temps it would pull as much as 10deg of timing.

i would like to see what the actual intake temps are, i could see if you did move it and were using some kind of water injection it could act as a back up if you were to run out of water, if the temps went way high it could pull lots of timing alowing you to program in more timing. i want to know where you put the sensor and what sensor you get if you move it.

 

Not sure which table your speaking of but tables I see within Ls1edit go as high as 215 C (419 F) which is also what SAE specs the max temp for IAT.

At this point Will has not measured the airstream from the SC and it could be higher then the value he used in his example above.
Being he is running 9 PSI boost and no intercooler, with the VE it could easy go over 110 F.
IAT is part of the math PCM uses for AFR being if it gets IAT before SC gets it hands on it, then it thinks air into inrake is close to outside air temp but due to compressing the air, heats up, PCM does not know that and you end up with a super lean condition.
If a least he mounts a IAT like on C5s which is on airbridge right before throttle body the PCM would be getting better temps from SC and commanding longer injector pulse widths.

With larger injectors he may get close but without intercooler may be forced to go 6 rather then 9 PSI boost.
I doubt 28 lb injectors can handle the existing SC setup.

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by parish8:
<strong>will, there may be a problem with moving the IAT sensor, not sure who told me this but they thought that the IAT would be maxed out most of the time if it was placed after the blower, the table in ls1edit only goes to something like 190deg. if it was pegged at 190deg all the time it wouldn't do much good either.

on my truck i am in a part of the timing curve where it only asks for 6-9deg of timing and if the IAT was seeing high temps it would pull as much as 10deg of timing.

i would like to see what the actual intake temps are, i could see if you did move it and were using some kind of water injection it could act as a back up if you were to run out of water, if the temps went way high it could pull lots of timing alowing you to program in more timing. i want to know where you put the sensor and what sensor you get if you move it.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">

 

team zr1, i am not sure what tables you are looking at or if the trucks have a diferent set of tables but within my ls1edit files i see the (IAT vs MAP timing retard) maxing out at 90deg C and the (open loop F/A multiplier) maxes out at 120deg C(although i bet this is coolant temp), i can see on that table how it might help with part throttle enrichment but at part throttle you should be in closed loop and at wide open(any boost) on that table the multiplier is 1.0 so no help there either.

i agree it would be better to tell the computer what the real temps are and then adjust from there.

 

Just goofing around with bernoulli's and some efficiency calcs, your inlet air temp on an 80 deg day would be somewhere around 140 to 150 F depending on your supercharger efficiency.

I think and intercooler would work wonders for you.