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Old 03-14-2006, 09:18 AM   #1
MidRex
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Default Weather changes

Since I had my tune at TXS I have been running Map1 which is my most agressive street map. Where I used to live I only had access to 93, but now where I live I can get 94 right by my house. When the weather got cold and I would run 93 I would get knock and would have to drop down to Map2 which just lowered the boost, but if i was running 94 I would get no knock. In the cold weather my car runs awesome on 94. The boost is a little higher in the cold though and my logs look good. Even AndrewTech verified this when I was out at his place.

My question is that since it is starting to get warmer now my car seems noticeably slower. Should I just turn the boost up a little bit to get that power back?
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Old 03-14-2006, 10:30 AM   #2
ride5000
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let's take two scenarios:

a) it's cold as hell out. the turbo compressor works more efficiently due to colder iat. the intercooler works more efficiently due to colder ambient air. you have chilly manifold charge temps. the turbo is pumping a lot of air mass into the engine. this cool, dense charge will take a lot of advance before detonating, BUT the cool dense charge requires less advance to achieve minimum best timing.

b) it's hot as hell out. the turbo compressor works less efficiently due to warmer iat. the intercooler works less efficiently due to warmber ambient air. you have hot manifold charge temps. the turbo is pumpg a lot less air mass into the engine. this hot, rarified charge will not accept much advance before detonating, BUT the hot rarified charge requires more advance to achieve minimum best timing.

you can see how forced induction cars love cold air temps.

can you up the boost to get some of that power back? depends on what you're running now, on what turbo. if you can up it a bit to get some of your lost mass air flow rate back then you'll get a bit of torque in the process. however, if you push it too much you will exacerbate the issue of hot, rarified intake charge which requires more advance for MBT but will not tolerate it due to det.

as for me, i run about 2-3 psi less boost in the summer in rhode island.

hth
ken
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Old 03-14-2006, 10:41 AM   #3
MidRex
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Default

I'm running a VF34 with a TXS Topmount

I'm tuned for 18psi on 93.

In the colder temps my boost would climb to ~20psi.

Running map1 on 94 in the cold almost feels like running my race gas map5 in the hot weather on C16.

I haven't changed any settings on my tune other than moving the MAP value from 7 to 10. How do I determine MBT?
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Old 03-14-2006, 10:52 AM   #4
ride5000
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Quote:
Originally Posted by MidRex
I'm running a VF34 with a TXS Topmount

I'm tuned for 18psi on 93.

In the colder temps my boost would climb to ~20psi.

Running map1 on 94 in the cold almost feels like running my race gas map5 in the hot weather on C16.
i'll bet it was a lot more torque than you were used to! you got a little more boost and a lot more mass air flow than you had been getting before.

you could get away with a bit more boost with that vf34 and big tmic. 20 psi is not out of the range of reasonable for 93 octane. just make sure you have loggers going when you try to tune in the extra boost for warmer weather. if you're using an abc it might just be easier to use that to up the boost a tad. go slow, 1/2 turn at a time.

Quote:
I haven't changed any settings on my tune other than moving the MAP value from 7 to 10.
which MAP value did you change specifically from 7 to 10?

Quote:
How do I determine MBT?
ahhhh... the best question yet! without a dyno this becomes a difficult endeavor.

since i don't have one, i have to essentially rely on two things: butt dyno (prone to subjectivity, but always on) and logs from the same sections of road (requires a high attention to detail).

in the long run we are limited by octane in terms of power output, so the idea of running as much advance as we can get away with without knock nets us our effective MBT.

ken
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Old 03-14-2006, 11:10 AM   #5
MidRex
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Default

Man....I must have been still sleeping when I typed MAP. I meant the value in the parameters for WGS. Changing it from 7psi to 10psi would net quicker spool correct?

Since I have 94 readily available to me now, I could possibly advance my timing some then too right? If I was to advance it, how much of an increase would you start with and in what areas? Across the whole map?
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Old 03-14-2006, 11:39 AM   #6
ride5000
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frankly, i would just run more boost instead of more advance.
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