IF I were to do this mod...I would block AFTER the MAF so that potentially I could still have a functioning SGII....though I might have to reset the engine displacement down some to compensate?
The TPS range on my Focus is 16 to 92 (92 being slightly low due to a throttle mod).....I'm usually in the 32-37 range manually (for best BSFC)...though the CC will hit 42 at times....and I figure 37 TPS is ~ 50% throttle.
So when using the SC with this mod...what gauge reading would be the best to monitor and what extremes should I look out for under the 50% TPS scenario? Load AND ignt advance?
KR defined...
FAQ: What is spark knock? What is KR (knock retard)?
Since I'm using a WAI and have a partially blocked intake...this could be an issue.
I wouldn't see an issue with blocking the accelerator to keep it under 50%...as simple as a block of wood under the pedal would work....50% pedal is pretty brisk acceleration....though probably some form of blasphemy to the avg car enthusiast.
While I could do this free mod in an hour or so and it is easily removable...but I'm not that interested in messing too deep. With a potential 20% gain...it's worth looking into. Might be a way to "detune" an engine for mpg purposes vs the car makers tendency to cater to the typical consumers desire for power at any cost?
I recently saw a 5% gain from installing a cone filter that has a bell-shaped intake molded in vs the factory straight edged intake pipe...at least I think this is where the gain derives from. Just a
minor conflict with an intake block?
Could it be that more air flow OR less air flow results in better mpg?
.....
After thinking about this mod some...I come to the conclusion that when blocking AFTER the MAF...the function of the MAF is not changed any...there will just be some restriction of air flow at higher flow rates.
Since I drive for mpg...90% of the time my TPS reads from 16 (idle) to maybe 19 or 20 at the most...17 or 18 if I can manage it. Which means the butterfly is only open up to ~4* over idle position 90% of the time...the block would be really not affect anything under these conditions? The 10% (?) of time where the flow rate at the TB is greater than that allowed through the blocked opening would be affected.
Quote:
Originally Posted by Phantom
By blocking the air to the MAF you are changing the calculation for load so it will read lower and increase timing that will help in mid-low load situations but if your timing map was close to the point of knocking in the high load area it can cause problems.
As for fueling the O2 sensor will compensate to the difference in fueling and adjust till it hits and stays at 14.7:1. With out the MAF getting a proper reading the engine will not be able to respond to a quick change in air flow. That will result in a lean mixture with to high timing when going from 20% throttle to 100%and that can pop pistons/heads/cylinder walls depending on the weak point.
To get the most benefit you should have a custom tune done on the car to increase the timing to a few points before the point of KR when the car is running on a hot day, if it is done on a cold day the KR will happen at a higher advance.
Depending on how the cars tuning is set up you might be able to disconnect the the MAF and run is SD (Speed Density) mode for the tune and get different results.
I would NOT do any of that without a scanner that at the very least will show you KR in real time to keep you from blowing your engine.
-I have had some fun tuning GM cars and this post is going to make me drive my wife's car so a can work on the tune again since I do not have the tools to tune me TDI.
|