QuestionQUESTION: I have a 1996 GMC 2500 4x4 5.7 V8 with 83,000+ miles, everything original. Mpg is 13 - 15 mpg at best. When towing a trailer it drops to 9-10 mpg. I was told that changing to a different camshaft would help mpg. A friend of mine did that many years ago and found @ 20% increase in mpg. Someone else recently suggested doing a "very mild grind" on the cam which would increase mpg and hp. Your thoughts, please. Where can I find additional suggestions on increasing mpg? Thank you.
ANSWER: The cam work will help. There are many other variables that will help and/or hurt as well. The climate, elevation, tires, gear and axle ratios, etc. When towing you can disregard MPG. I have a 1999 Dodge Ram. I installed a cold air and flowmaster exhaust. It did help. Keep in mind the internal combustion engine is essentially your basic air pump. I will say for your vehicle, older four wheel drive. You are doing about average.
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QUESTION: But what cam work exactly? Are you concurring with the "very mild grind" comment I provided? Is there not a different cam to buy that is specifically designed to enhance the mpg? My friend referred to his new cam as a "trailer cam". Although I suspect it was to assist the truck to haul the extra weight of a trailer, he specifically installed it for mpg purposes. Are there different rockers to be installed or rods, etc. etc. in order to address this mpg issue?
Concerning the climate (Canadian prairies) how do you make adjustments to the engine to address climate issues? Is there a chip that could be installed or a diagnostic tool that could be bought?
To refer to your "air pump" analogy, I noticed that the Mass Airflow sensor is a restriction in the air intake system. Although I understand its purpose, is there anything that can be done to remove the restriction yet have a functional MAF? We install less restrictive intake and exhaust systems yet at the same time have this restrictive MAF right in the middle.
I know my questions bring up several issues, but mpg is the focus of it all. Thanks again.
ANSWER: Let me answer this question in parts. To be completely specific about the cam, I would need to have your truck in my shop. Did you replace the cam bearings when you replaced the cam or inspect them. http://www.compcams.com/Company/CC/CamRecommendation/CamHelpNew.aspx click on the cam quest 6 link in the left menu at the bottom. You will need to register, and answer specific questions to your vehicle.
You could change to stage two injectors, roller rocker, economy heads, chromoly push rods, and the list goes on. Keep in mind this should be done as a weekend project. If you do the cam or rockers you should do everything from the heads up. In my personal opinion. A cold air intake will help. I would strongly recommend Spectre. It will cost you about 80.00 for the complete system. You may consider picking up a recharge kit as well.
There are many on board monitors that will afford you different settings and diagnostic tools as well. I am planning on installing one in my 1999 Dodge Ram 1500. I would try www.autoanything.com for these applications. There are many to choose from that will let you select economy to extreme performance.
As for the MAF sensor, you can find an after market replacement for that as well. You can consider an ECM/ECU as well. I would replace the MAF personally. Consider a "flow-through" Catalyst.
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QUESTION: How would a throttle body spacer help? A parts dealer suggested that just the other day as an mpg helper. he said it would provide more time/space for the air and fuel to mix before hitting the cylinders. Your thoughts?
AnswerA throttle body spacer creates a larger area for air to the throttle body. This gives the throttle body a larger capacity for air intake. The throttle body spacer allows a greater amount of air to pass through the valve, increasing the power available to the car. This also improves the car's energy efficiency, due to the fact that the air is readily available, so the car does not need to expend effort to bring it to the throttle plate.
Basically, more air push more fuel to the cylinders=more power. This do not necessarily use more fuel, however it does help the engine become more efficient. Depending on what you have in your motor and how you have it tuned. Another thing you may look at is a more effiecent ECM or "mapping", if it is possible. Some are "flash" computers (only flash the codes), others can be adjusted (need laptop and software).
