IAT clamp vs. Throttle position

[dadasracecar]

So I did the coil spring stretch and I wanted to see if it fixed the winter fuel cut. I thought I would datalog a couple of WOT runs with the IAT set to 82 deg and then take the IAT clamp off and repeat to see the difference and datalog a fuel cut if it was present. The ambient temp was 46 deg which should produce a fuel cut most of the time on my car. Short story is that no fuel cut happened so the coil spring does play some sort of role, crazy as that is.
This morning however, it was 37 and I was routinely fuel cutting in 6th at 3600 rpm with the stock IAT sensor. The fuel cuts seem to be less severe and less jerky but they're still there. Spark blowout?

The weirdest thing about the fuel cut is that you can dial it with the IAT clamp. Higher IAT temps dialed with the potentiometer move the fuel cut to higher rpm and eventually prevent it. So while the spring stretch mitigates it, it does not remove it for me. So there is still work to be done.

Anyway, the point to this thread... So I did three runs at WOT in 4th. The afr is almost identical. This is expected as the car has a MAP IAT that is most likely used for air density calculations. The interesting thing is the throttle behavior. The tps is all over the place in both but it opens about 25% more with the IAT clamp! Look at the axes. The IAT clamped runs are near 80% while the stock IAT barely hits 60%. Here are the logs. You'll also notice that the timing is the same so at IAT=82 deg the car is running the stock timing.

IAT=82run1

IAT=82run2

stock IATrun1

 

[laloosh]

i already posted my thoughts on 6club but have another question. Why is your maf voltage so low?

 

[dadasracecar]

I think it's the scaling that the Dashhawk uses isn't right. I'm up above 4 volts when I datalog with the standback.

 

[laloosh]

also out our curosity, did u ever do a 1/4 run? if u do log ure a/f and kr during the run. im will to bet u will be higher then the 12.1 ure running right now. For some reason my car runs leaner when i floor it through the gears rather than just doing a 4th gear pull at a low rpm

 

[Flogbox]

Nice bit of information there.

 

[jp4130]

Hey dada dial in some crazy cold temps and see what it happens.

I got my first boost cut the other day at 20; when it was -20 or even colder here it would not cut at all.(uhm) This would prove your theaory that it is a hole in the ecu's programming. I still do not like this type of fix, however i think you may be right on the cause of the cut being the ecu's programming.
Give it a try.

 

[Captain KRM P5]

Excellent work as always dada

So I did the coil spring stretch and I wanted to see if it fixed the winter fuel cut. I thought I would datalog a couple of WOT runs with the IAT set to 82 deg and then take the IAT clamp off and repeat to see the difference and datalog a fuel cut if it was present. The ambient temp was 46 deg which should produce a fuel cut most of the time on my car. Short story is that no fuel cut happened so the coil spring does play some sort of role, crazy as that is.
This morning however, it was 37 and I was routinely fuel cutting in 6th at 3600 rpm with the stock IAT sensor. The fuel cuts seem to be less severe and less jerky but they're still there. Spark blowout?

The weirdest thing about the fuel cut is that you can dial it with the IAT clamp. Higher IAT temps dialed with the potentiometer move the fuel cut to higher rpm and eventually prevent it. So while the spring stretch mitigates it, it does not remove it for me. So there is still work to be done.

Anyway, the point to this thread... So I did three runs at WOT in 4th. The afr is almost identical. This is expected as the car has a MAP IAT that is most likely used for air density calculations. The interesting thing is the throttle behavior. The tps is all over the place in both but it opens about 25% more with the IAT clamp! Look at the axes. The IAT clamped runs are near 80% while the stock IAT barely hits 60%. Here are the logs. You'll also notice that the timing is the same so at IAT=82 deg the car is running the stock timing.

IAT=82run1

IAT=82run2

stock IATrun1

 

[dadasracecar]

Excellent work as always dada

Thank you.

I was feeling like my car was a little sluggish today on the way home. I am still running the stock IAT and it just dawned on me that that throttle may have been the culprit for the way my car felt on my way home so I went back and looked at the logs. Here they are with 60% highlighted in green. I think I found my issue...

stock IAT

IAT clamped at 82

 

[dadasracecar]

Based on the way my car feels now (stock IAT) OMG do we need throttle control.

 

[palerider]

Based on the way my car feels now (stock IAT) OMG do we need throttle control.

Not to be a killjoy... but reading this the first thing that popped into my head is the Cobb guys saying throttle control, ISNT necessary. I am curious as to why they would claim this when so many disagree.

Im getting sick of all the ghetto mods we have to do in order to get our cars to kinda run right...sorta maybe.

Great info though.. thanks for sharing. I hope your passing stuff like this along to the programmers.

 

[tru-boost]

this is my thought on it ......
if your car has the same amount of boost, same amount of timing, and same AFR, what do you think you are gaining from having the throttle open more ??
it looks to me from your logs that everything stayed the same with the exception of the TPS %. i'm very iffy on this.

 

[Craighjr]

Hey dada dial in some crazy cold temps and see what it happens.

I am pretty sure the iat clamp doesn't work that way. You can only add resistance which increases the temp reading. The coldest you can read is what ambiant currently is.

 

[jp4130]

I am pretty sure the iat clamp doesn't work that way. You can only add resistance which increases the temp reading. The coldest you can read is what ambiant currently is.

Oh I see, I did not look into this mod. I don't like the idea of of tricking the ecu like this. I still find it bizzare that the cut will happen at 20 but not at -20. If the cold is what causes it, -20 would be the ecu's worst nightmare.

 

[Mid_Life_Crisis]

Oh I see, I did not look into this mod. I don't like the idea of of tricking the ecu like this. I still find it bizzare that the cut will happen at 20 but not at -20. If the cold is what causes it, -20 would be the ecu's worst nightmare.

As I pointed out previously, this makes it look like bad maps. At some temperatures the car runs great, at others it is a POS. It isn't everything below a certain temp, it is a certain range that has the problem. Depending on how good Cobb's software is, we might be able to fix this with a reflash.