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Discussion Starter #1
Hi

I`ve been wandering on something for a while.

First of I live in eastern Canada, the tempatures in the winter can dip down to around -10F. With the cold temp comes denser air. More air means more boost, and that means over boost. Or does it, I know the ECU takes care of the A/F for the lower temp, is there any adjustement to control the extra boost? I`m just thinking a summer tune could be dangerous in the winter for overboosting?

Now my other question, I know when tunning they turn off everything, radio, AC, fan...now I understand turning off teh radio since it could cause ghost knock. But i`m wandering with the AC and fan, since they add load to the engine, and they could cause knock...wouldn`t it be best really to tune with EVERYTHING on? Cause if you get a perfect no knock tune, then you drive around with the AC on that could load it and knock and damage stuff? I`m just wandering if I`m seeing this the wrong way or not?

The way i`m thinking the safest tune would be with everything on in freezing cold. If it doesn`t knock then, it should be good anytime. (in the summer you wouldn`t be optimized tho)

Imput would be greatly appreciated, but only if you actualy know what your talking about please no guesses.
 

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Colder air is less likely to knock - you can run leaner AFRs on colder air as a result. If you get tuned when it's REALLY cold, then when it's hot you may get some detonation as a result of AFRs that are too lean. This is why it's a good idea to tune to a safe AFR regardless of temperature outside, so that when it heats up you're still in good shape.

I haven't heard of the radio or ac fan causing false knock on these cars.

To deal with overboost you can either run PSI based boost control which will make sure your car always targets a certain PSI rather than a load value and the car (with proper error correction) will always hit the desired PSI regardless of temperature. The main thing you have to deal with is just making sure your error correction tables are set up correctly (and enabled) to reduce WGDCs and you shouldn't have to worry about much overboost (except on shift or when flooring it at a high rpm, but there are ways around this, and another thread on it).
 

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Hi

I`ve been wandering on something for a while.

First of I live in eastern Canada, the tempatures in the winter can dip down to around -10F. With the cold temp comes denser air. More air means more boost, and that means over boost. Or does it, I know the ECU takes care of the A/F for the lower temp, is there any adjustement to control the extra boost? I`m just thinking a summer tune could be dangerous in the winter for overboosting?

Now my other question, I know when tunning they turn off everything, radio, AC, fan...now I understand turning off teh radio since it could cause ghost knock. But i`m wandering with the AC and fan, since they add load to the engine, and they could cause knock...wouldn`t it be best really to tune with EVERYTHING on? Cause if you get a perfect no knock tune, then you drive around with the AC on that could load it and knock and damage stuff? I`m just wandering if I`m seeing this the wrong way or not?

The way i`m thinking the safest tune would be with everything on in freezing cold. If it doesn`t knock then, it should be good anytime. (in the summer you wouldn`t be optimized tho)

Imput would be greatly appreciated, but only if you actualy know what your talking about please no guesses.

That is somehwhat true but not entirely. Assuming everything else is equal a drop in temperature will need added fuel to combine with the higher oxygen amount ( because cold air in denser and therefore contains more oxygen molecules per mole). This is also who cars and internal combustion engines in general make more power when they have cold air. A good example of this is the intercooler on our cars. Yes they help fight knock and detonation but they still need increased fuel to compensate for the higher oxygen concentration. This is why almost all newer cars are fitted with a MAF sensor and Intake air temperature Sensor. With these two sensors the car can determine the velocity and temperature of the intake charge and supply the proper amount of gas to allow proper combustion.


If you were to take a car that just had a turbo charger and ran perfectly fine without any knock and then added a intercooler ( without adjusting the fueling) that lowered the intake charge 50 degrees the car would definately have severe knock. The colder intake temp would help fight the knock but due to the severe lack of fuel the car would be very lean and this would cause knock.


This is the same reason a car needs to be tuned for nitrous administration. Yes the nitrous helps cool the air intake charge and yes the cooler temp helps fight knock but the nitrous supplies such a large amount of oxygen that without additional fuel it will run lean.


So, to answer the OP's question, yes the temp can affect tuning. BUT, our cars are fitted with sensors that allow automatic adjustment of the fuel to supply the additional fuel if the air temp drops. If someone had they car custom tuned and the tuner messed with these ( automatic adjustment trim values) then the car could have a problem but as far as I know they dont do this normally and if they do they take temperature fluctuations into consideration when doing so.

Im not 100% sure but I dont think the air conditioner or alternator will have a large enough affect on the engine to cause knock.
 

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Discussion Starter #4
#1CBR, So what you are saying is that even if the car is tuned in cold or warm temps, the opposite temps shouldn`t effect the over all knock count?
 

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#1CBR, So what you are saying is that even if the car is tuned in cold or warm temps, the opposite temps shouldn`t effect the over all knock count?
I'm pretty sure all he was saying was that the car takes into account air temp when applying fuel and attempting to hit the target AFR, which from what I could tell you already new. My point is that an AFR of 11.8 might not knock when it's 20 degrees out, but it may knock when it's 100 degrees out.

Your ECU knows how much air is coming in and how dense it is based upon temperature, so assuming your injectors/pump can support the required amount of fuel, you won't have issue with the car being lean in the winter or rich in the summer.
 

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To deal with overboost you can either run PSI based boost control which will make sure your car always targets a certain PSI rather than a load value and the car (with proper error correction) will always hit the desired PSI regardless of temperature.
If load based is setup correctly, this isn't a problem either. Cobb uses load based on all of the X's they tune. I tried direct boost (PSI based) and didn't like the varying load vs boost. There is a good a bad side to everything.
 

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If load based is setup correctly, this isn't a problem either. Cobb uses load based on all of the X's they tune. I tried direct boost (PSI based) and didn't like the varying load vs boost. There is a good a bad side to everything.
I know, thats why I said:

"The main thing you have to deal with is just making sure your error correction tables are set up correctly (and enabled) to reduce WGDCs and you shouldn't have to worry about much overboost"

Either works so long as you have error correction set up properly. :godance:
 

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OP, there is a table within our ECU that controls timing retard based on intake air temperature.



Let's see if I can explain this without getting roasted. Bear with me.

As you can see, and supporting #1 CBR, when it gets cooler out the ECU knows, based on intake air temperature, to retard timing by x amount.

The cooler temperatures are making the air more dense and the MAF takes that into account when entering the intake. But once the air passes through the intercooler it becomes even more dense due to the cooling effect of the intercooler. The same amount of air is in the system but what is ready to be supplied to the cylinders is a little bit more dense i.e., a little more oxygen (higher load). The ECU uses the IAT to compensate for that by retarding timing.

In warmer temperatures, timing is retarded to combat hot air which raises cylinder temperatures and increases the likelihood of engine knock/detonation.
 

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I just learned something, I had never heard of that table! Thanks Silicon! Is our MAP sensor before or after the intercooler?

If it is after, then the increased density of the further cooled air would be accounted for no?
 

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I just learned something, I had never heard of that table! Thanks Silicon! Is our MAP sensor before or after the intercooler?

If it is after, then the increased density of the further cooled air would be accounted for no?
After, it is on the intake manifold. I believe so, I am not sure on that part, maybe someone else can chime in. I am not sure what all our MAP plays a part in.

For instance, our stock map only retards timing at 19F and 133F, between 20-100F no timing retard takes place. I changed mine to the other one, I would often get some knock at 95F+ so I added more retard there.
 

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I have a question;

I was tuned when it was really hot (104*), and running 11.2-11.7

Now that it is about 50* outside, I am seeing 11.4-12.0....is it normal for the afr's to change with weather, or should they always look the same? I thought that even if it gets colder and the car can get more oxygen, it should add the appropriate amount of fuel, making the air/fuel ratio stay the same.......so why am I leaning out?
 

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I would say it's because the cold weather has resulted in different cells being hit (ie. different load), and those cells haven't been tuned quite right.

Rich
 

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Should I bring it to my tuner then? Thanks for the response Richard.
 

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ok i was tuned in 3rd gear (our 1:1 i believe), and was doing my street pulls in second. Apparently it's normal to have leaner afr's in the gears below which one is tuned in...is that research correct, or just internet-thread bs?
 

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That's what I see. I tuned my afr to be at 11.0:1 using 3rd gear. When I ran 4th gear to redline at the track, the wideband read 10.8:1-10.6:1.

I can see now that I won't be able to resist another round of tuning. ;) Stretch its legs a bit in terms of boost targets (can stretch a bit higher in 4th+), revise fuelling to run at 11.0:1 in 4th instead of 3rd... and see how she goes.

Rich
 

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4th is 1:1 on a GSR? So why do tuners do 3rd gear pulls? Shoot, ive been doing 3rd gear pulls when I was getting e-tuned, does that matter?
 

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I guess road tuners do third gear pulls because doing repeated fourth-gear runs in a modded (most likely illegal) evo on the street is flat-out insane lol.

My dyno tune was in fourth I learned.

Anyways, my Afr's kinda settled back to normal...only thing I can think of is me resetting the fuel trims. tonight is the coldest it has been here, and even my second gear was 11.1-11.4ish. Never more than 11.7.

Makes me feel safe :)
 

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Exactly. It's a speed issue on the road.

And what does 4th being 1:1 have anything to do with anything? In a GSR, 4th is actually 1.096:1 and 5th in an MR is 1.008:1. The rear end of a GSR is 4.687:1 and an MR is 4.062:1. That makes the Final Drive Ratio of 4th in a GSR 5.137:1 and the FDR of 5th in an MR 4.094:1. So you can see that the two 1:1 gears are totally different from each other.

For comparison, FDR of 4th (1.322:1) in an MR is 5.370:1, which is almost the same as GSR's 4th.
 
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