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Old 04-28-2009, 03:34 PM   #7 (permalink)
cfg83's Avatar
Join Date: Dec 2007
Location: Southern California
Posts: 5,864

1999 Saturn SW2 - '99 Saturn SW2 Wagon
Team Saturn
90 day: 40.49 mpg (US)
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Wonderboy -

Originally Posted by Wonderboy View Post
I linked to a thread about my car in my previous post. There are pictures there of where I routed the intake. I am just reading intake air temp from my SGII. I would expect mine to get a little more than "warm" (wherever the temperature threshold is) because my highway run was only about 6 miles... it will probably rise above 140 on substantial (hour long?) highway trips... then again maybe not. More results are yet to come.

@cfg83: Could you explain the risk of knock/ping involved with using regular octane gas? Should I consider using 91?
There area others that can explain it better than me. I think that we are safe because we are not driving under heavy load (high RPM), we are "featherfoots", so to speak.

Here are some quotes from RH77 :

Fuel Grades - Post #9
Originally Posted by RH77 View Post
When I had my HAI (160F) I used premium to prevent detonation, but the cost-benefit was off. Now, intake temps are 100-120F with full advanced timing and no ping with near-full load (some knocking at high RPM, so I don't go there much).

The TSX "requires premium", but runs just fine on regular. The savings add up. FE is the same too. There's a bit of stumble from time-to-time at 6k RPM with VTEC, but again, very rarely used.

Long live 87!

Cold air VS Warm Air Intakes - what's the difference? - Post #5
Originally Posted by RH77 View Post
I have a brief response -- incomplete answer.

From the shop manual on my vehicle, the engine is intended to run richer at intake temperatures below a certain figure (I forget the exact number, let's say 60F). Warm air is needed to satisfy this requirement, especially in Winter.

Beyond that, I've determined with repeated testing that my engine operates most efficiently with IATs at 90-100F. Beyond 120-130F, it starts to dump-in more fuel to compensate for pre-ignition, and fools with the timing. So that temp above the maximum requirement of ambient up to at least ~90F yielded around a 15% increase when I first tested it 2 years ago (the abstract is floating around somewhere -- I think there was a cold-air intake on the car before). FE drops when colder air is introduced, even at ~70F, which is well within the requirements of the sensor/ECU closed-loop management. You may find terms of HAI and WAI (hot and warm air intakes).

How it works -- not exactly certain. A couple years ago I did quite a bit of testing with different temps and found the "sweet spot" for my car. There's still quite a bit of discussion on the topic and the term "pumping losses" can best be explained by someone with more Physics knowledge than I have.

My advice? Experiment yourself with different temps -- and stay as Scientific and consistent as possible. See if you can obtain info on IATs and the vehicle ECU's compensation from a shop manual or enthusiast website. BTW, what kind of vehicle do you have?

Let us know if you test and come to some conclusions.



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