Foreword: Over the years we have published this site, many readers have raised questions about power upgrades to improve engine performance. When we had occasion to have our own truck serviced by Chuck Arnold at "The PowerShop" in Enumclaw, Washington (Seattle area), we knew from personal experience we had found a highly competent and professional expert on engine performance enhancements. As a consequence we asked Chuck if we could tap into his expertise for the benefit or our readers, and ask what we consider are the most important -- and challenging -- questions about this subject. We think the responses that Chuck provided are absolutely crucial to RVers who want objective, factual information about upgrading engine performance. We're grateful to Chuck for the time taken to put together these thoughtful and informative answers.

QUESTION: Many of our readers that own trucks that tow larger fifth wheels have expressed interest in options for “power upgrades”. Realistically, what approximate increase in horsepower and torque can be expected from a power upgrade? Is either a gas engine or a diesel engine a better “candidate” for a power upgrade? And does it matter whether the transmission is automatic or manual?

ANSWER: There is no simple answer to the how much horsepower question. The key to long term success with any vehicle modification is compatibility. A modification where the amount of power added is compatible with the weight, is compatible with the transmission, is compatible with the engine, is compatible with the brakes and is also compatible with the budget will give you great long term service. To the degree you ignore important compatibility issues, adding more power than you can use efficiently, you will contribute to your future troubles with the rig. I can make some general comments, which will be true in most cases.

a. Gas or diesel: The majority of people who drive RV vehicles in the mountains want more power after the first trip. Most are quite happy with moderate power increases in the 40 to 60 horsepower range. 50ish additional horsepower is enough so you can really feel it but not so much that it is overwhelming to other components. Performance enhancements that work by adding fuel may increase demands on the cooling system and must be very well engineered to avoid overheating problems hauling heavy loads up hills in hot weather.

b. Your diesel pickup will be much better off with 50 horsepower, gauges and a retarding system than with 100 horsepower and an endless chain of transmission failures during its service life. Upgrading your automatic transmission, when or before it fails, to be compatible with higher horsepower will allow you to make good (compatible) use of more aggressive power upgrades.

c. If you can use a manual trans in your application then do so. People towing heavy trailers with auto trans pickups will typically have to pay for an expensive transmission repair between 30 and 110 thousand miles. If, at the time a trans is worked on, it is upgraded properly then there is hope it may go the distance. Without upgrades, automatics built over the last 20 years will usually fail long before a manual transmission doing the same work. The new GM Allison automatic along with new offerings from Ford and Dodge offer some hope that you may finally be able to buy a big pickup for towing where the stock auto trans is not the weakest link in the vehicle.

QUESTION: What’s the difference between “horsepower” and “torque”. Is one or the other more important for towing a fifth wheel or trailer; or for driving a motorhome?

ANSWER: Horsepower and Torque are often misunderstood. Many an old trucker will tell you “I don’t care about horsepower, it is torque that does the work.” In truth you can’t have one without the other. Torque is instantaneous twisting force. If you apply one pound of force to turn a shaft with a one foot lever you have applied one “foot pound” of torque. Horsepower is a measure of work done over time. One horsepower is the amount of work done when 550 foot pounds of torque is applied to the job for one second. You can see that without keeping the force applied for a period of time there is no horsepower. You will find that it takes a finite amount of horsepower to push a weight up a hill at a certain speed. The faster you go the greater the power demand. When you can’t go any faster using all of the available torque at the engines peak horsepower rpm, the amount of power is in equilibrium with the forces of gravity and wind holding you back. It is true that if you add torque you will be able to go faster up the hill because to add torque is to add horsepower.

QUESTION: We’ve heard of some lower cost options that are described essentially as installing “a new chip”? Wouldn’t this be a simpler and easier solution to achieve increased power?

ANSWER: Chips are electronic devices that increase fuel rate and/or enhance timing to improve performance. Compatibility is the key when considering how to safely use any product that can increase the amount of fuel used by the engine. It is easy to install a chip (or other plug in module) but if heavy loads are involved, it is almost never wise to use electronic enhancements without first improving the engines breathing via intake and exhaust enhancements. Without better breathing, increased fuel leads to more heat as well as increased wear and tear on the engine. Push too far and your valuable engine can quickly become scrap. If your tow vehicle will gain measurable power with just a breathing enhancement, you should consider prudent exhaust and intake changes to be the foundation for use of chips or other electronic enhancements. Chips always increase exhaust flow. If flow is restricted, the engine labors just to pump air in and exhaust out. It is obvious efficiency will be worse if a chip increases the volume of exhaust gas. Inefficiency in this discussion means HEAT and can mean NEW ENGINE.

QUESTION: Do power upgrades impact fuel economy?

ANSWER: Power upgrades do impact fuel economy. Poorly engineered upgrades (changes where compatibility issues are ignored) usually will prove to be a fuel economy detriment. It is very common for well-designed enhancements to improve economy somewhat if measurements are taken at comparable speeds. The effect of wind resistance while traveling 70 miles per hour on the level (with a high frontal area 5th wheel or motorhome) requires the same horsepower as moving up a 6% grade at 50 miles per hour. If you travel faster, after a power enhancement, you are choosing to use more fuel. My example above applies to moving at highway speeds. Crawling up passes at 30 mph in lower gear is inefficient. If a power enhancement gains you a gear and 10 plus miles per hour, your hill climbing mileage will be vastly improved due to a big decrease in the number of revolutions your engine must turn to get you over the top. People who get the best mileage with RVs drive moderately. If your engine is working freely as opposed to straining for all it is worth, mileage and longevity are both improved. Ease in and out of the throttle and take pains to reduce load while shifting to get the best mileage and help your vehicle last. It is also helpful to monitor fuel mileage. With some experimentation you will find the “sweet spot” traveling speed where both power and economy are at a happy medium. Use changes for the worse in mileage as an indicator of mechanical issues requiring attention.

QUESTION: Many readers express reservations about the potential warranty implications of any modification designed to increase engine power, except those offered by the vehicle’s manufacturer. Based on your own personal experience, should RV owners be concerned about invalidating a new engine warranty – and/or are there steps they can take to minimize that risk?

ANSWER: Warranty is a complex issue due to the fact that vehicle dealers and manufacturers don’t always play by the rules. To describe the warranty implications of vehicle modifications requires a three part response, preceded by a disclaimer of my own that what follows is not intended as "legal advice", but rather as practical guidance based on many years of experience in observing the handling of warranty claims.

a. Understand your legal rights. According to your vehicle warranty manual and federal law, “modifications to your vehicle (using aftermarket parts) do not, of themselves void your warranty but if a failure is caused by a non (Ford, Chev or Dodge etc.) part then your warranty may be affected.” The above statement or a very similar one is in the warranty section of every owner’s manual for every vehicle sold in America. To comply with the Magnuson Moss Act and be a legal warranty, such a statement is required. Use of the phrase “caused by” in the warranty statement means that for your warranty to be legally voided, due to a modification, the manufacturer of the vehicle must demonstrate how the modification caused the failure before denial of a warranty repair. Over more than 30 years of doing RV vehicle enhancements for a living, I have found that compatible and prudent enhancements do not cause failures but rather extend service life in most cases. It is important to note that any modification that constitutes "emissions tampering" will give the vehicle manufacturer a legitimate reason to deny an engine related warranty claim. For this reason, it is important to choose enhancements that are tested and certified to be emissions legal in all 50 states. Installation of an enhancement product that has emissions certification does not constitute emissions tampering as long as the product is installed and calibrated properly.

b. Understand warranty from the dealer’s viewpoint. If the law of the land as stated above was always adhered to warranty issues would be simple but unfortunately the law is sometimes ignored or abused. For many reasons, (none of them noble) vehicle manufacturers and dealers will often blame a modification for a failure with no proof of cause and sometimes with no diagnostic efforts at all. This happens for the following possible reasons:

i. The dealer would rather you pay for the service than wait for the manufacturer to pay and also scrutinize the transaction.

ii. The dealer is not willing to take the time to determine the cause of a failure, which involves a modified system. The dealer may be worried that billable time will be lost when his technical people struggle to understand the modification in order to make a fair decision as to cause. Some dealership technicians are also very anti- modification and refuse to help as they should.

iii. Technical expertise is lacking and the dealer is unable to (or worried that they will be unable to) determine the cause of the failure. The vehicle manufacturer will (properly) reject invalid causes of failure and not pay the claim so, if a dealer knows his technical people will come up with invalid causes a percentage of the time, some dealers will choose the strategy of denying warranty up front to avoid the possible loss later. To the degree they get away with this they break the law.

iv. The vehicle manufacturer orders the dealer to deny warranty merely because a modification is present and without valid diagnostic efforts to determine the cause. Every time this happens the dealer feels his hands are tied and will go along with the big company in unfairly denying a warranty claim. Over the years I have seen hundreds of cases where the first response of the manufacturer, in a case of major failure, was to deny warranty. In a majority of these cases a fair decision resulted after the vehicle owner refused to accept the arbitrary denial and argued effectively for his legal rights under the warranty contract. In this kind of case, to pay the bill your self without forcing the proper process to be done is the throw away your warranty rights. In my experience a disturbing trend in recent years is that manufacturers have engaged in this behavior with increasing frequency, with Chrysler Corporation being the worst offender.

If you do not want to take responsibility for defending yourself from the kinds of warranty abuse described above you should think twice before you modify your vehicle because there is a chance you will run into at least some unfair treatment during the warranty period. Do understand that responsible manufacturers of performance products and installing shops will help you all they can if a problem comes up but the ultimate responsibility for defending yourself resides with you.

c. Stay in control of the situation when you go in for warranty service. At the PowerShop I teach our performance enhancement customers to use a strategy for dealing with warranty issues that will always be effective when you are working with a vehicle dealer who has your best interests at heart (and will also be effective in many cases where you would otherwise be taken advantage of as a matter of dealership or manufacturer policy). The process we recommend is a series of steps that permit you to stay in control of a failure resolution issue and have the best chance of a fair outcome. The steps of the process follow, along with supporting explanation:

i. Remove or disable active electronic enhancements. If your vehicle has changes installed that modify the electronics, disable or remove them. I am not talking about hiding anything. If the dealer’s technical people are competent you will probably not be able to hide the fact you have been using the enhancement. I recommend that chips be removed and electrical modifications to transmission performance be disabled so that the dealer’s technicians can work on what they are used to without confusion added by an unknown system.

ii. Dealers always assume that you expect repairs to be free. Letting the dealer know you understand that if the modification is the cause of failure you will have to pay for repairs takes the pressure off and should make the dealer willing to really help you as you have taken away his perceived risk.

iii. Make “job one” for the dealer be finding the cause of the failure. When you arrange to take your vehicle to the dealer for correction of an issue you hope will be covered by warranty, tell them you are authorizing them to “FIND THE CAUSE OF THE FAILURE”. Make sure they understand that you are not authorizing repair until the cause is determined. Tell the service writer that you understand that if they have to do extra work because of a modification or if the modification is found to be the cause of the failure, then you expect to pay for additional diagnostics and any needed repairs legitimately caused by the modification. It has been my experience that many, if not most, warranty denials have the dealer’s fear he will not get paid by the manufacturer, as a component of the problem. By using the strategy I recommend here, you take that risk out of the equation, as long as the dealer’s technician is competent. IF YOU DO THIS STEP AND THE DEALER WON’T PLAY BY YOUR RULES THEN FIND A DEALER WHO WILL AND GO ELSEWHERE EVEN IF IT TAKES A TOW TRUCK!

iv. Make the dealer’s tech people explain the cause of failure in terms you can understand. I have found that non-technical people can always understand complex failures well enough to see that an explanation of the cause of failure is reasonable if some effort and thought is put into the process. IF THE SERVICE WRITER CAN’T EXPLAIN THE CAUSE OF A FAILURE IN TERMS YOU CAN UNDERSTAND THEN HE DOESN’T UNDERSTAND THE CAUSE HIMSELF. ASK TO TALK TO THE TECH. IF YOU STILL CAN’T UNDERSTAND THEIR REASONING BASED ON THE FACTS OF THE DIAGNOSTICS THEN STOP THE PROCESS AND GO TO A DIFFERENT DEALER!

v. The four steps above are for the sole purpose of helping you CONTROL the process so that you get a real and fair cause of failure known BEFORE the vehicle manufacturer is asked to contribute to or make a warranty decision. I have found that, most of the time, a fair decision for all concerned will result when the dealer’s technical people can explain what caused a failure and the exact steps taken to determine the cause. Often when going through this process, BEFORE the vehicle manufacturer becomes involved, you can get great help from the enhancement manufacturer or from the shop who installed the enhancement while they can still be an ALLY of the dealer’s tech department rather than their ENEMY. Also you avoid the possibility of an erroneous denial being attached to your vehicle’s permanent record and coming back to haunt you if a future failure occurs.

vi. If, after going through the steps above, you get a denial, whether it seems to be fair to you or not, expect to pay the bill and take the issue up with the enhancement providers and/or fight on with the manufacturer. Make sure at this point that you have communicated with the tech people from the enhancement manufacturer and that they have had a fair chance to help in the above process. DOCUMENT EVERYTHING! Keep a written record of dates and times of all phone calls, who you talked to, what you authorized and did not authorize and always get a WRITTEN STATEMENT OF DENIAL on a service invoice or the dealers letterhead. MAKE SURE TO SAVE ANY PARTS WHICH FORM EVIDENCE OF THE CAUSE OF FAILURE! If a failed part has a core charge, pay the core charge and keep the part or you will throw away any chance of recovery. The core charge will typically be refundable after you finish working the dispute.

vii. Once you have a written denial on a paid invoice for the diagnostic process as described above, you have the option of having the dealer make repairs or going elsewhere. If you have not developed faith, via the process above, that the dealer is technically competent, honest and that the real cause of failure is known, you may be very wise to seek outside help. Just last week I helped a customer who had been denied warranty for a supposed injector pump failure. Two Dodge dealers claimed the injector pump needed to be replaced when in fact the throttle linkage was not properly adjusted after the first Dodge dealer performed a recall on the linkage. Our tech diagnosed and fixed the problem in just over an hour.

viii. It has been my experience, over years, that the above process is a very effective tool to ensure you get fair treatment in warranty issues. The better performance enhancement companies will typically reimburse you for your expenses if you do this process and their products are found to be the cause of a failure. This process gives you the best chance of getting the dealer and manufacturer of your rig to do their job, find the real cause and honor their warranty. If you end up having to pay for repairs out of pocket, you have what you need to pursue the issue further through arbitration, small claims court or a lawsuit and be able to do so with great prospects for success.
If you don’t want to take responsibility for exercising CONTROL as described above then be willing to just pay the bill if warranty abuse occurs or don’t modify your vehicle. If you find a dealer who works hard to help you get fair treatment in warranty issues help his business by spreading the word of your experience to other people. This dealer is one you want to stay in business and prosper.

QUESTION: In your opinion what is the relative importance of exhaust brakes (or retarders) in the overall picture. Are there significant differences among the available products that RVers should consider when selecting a product? Again based on your experience, are some systems more effective and/or reliable than others?

ANSWER: People need retarders is the short answer. If you tow a heavy trailer with a diesel pickup or travel in a diesel powered motorhome, an exhaust retarder will add tremendous confidence, safety and reduce brake repair costs. If you haven’t used a retarder and try one, the first big hill will convince you not to travel again without it. As with all products, quality and performance varies. Any RVer who has looked at the Internet or trade publications recently knows that there is an industry war going on over whose retarder is best. At the PowerShop we handle this issue by taking into consideration the individual user needs and vehicle and then teaching the needed facts to make you able to arrive at an informed decision. There is not a simple blanket answer to the question of which retarder is best.

QUESTION: We frequently get questions at our website asking, in effect, what upgrades are available to increase the towing capacity of a tow vehicle. Are there any upgrades, or combinations of upgrades, that can increase the manufacturer’s weight ratings?

ANSWER: While it is possible to make any component of any vehicle stronger and to make RV use vehicles more powerful, there is no way to raise the manufacturer approved tow weight rating of a vehicle. Vehicle manufacturers will never raise a published rating because modifications have been made. This means that if you choose to haul more than the rating, you take risks, regardless of what modifications you may have done to help your vehicle work better. I know many thousands of people who have traveled millions of trouble free miles with moderately overloaded RV vehicles BUT (and it is a big BUT) if you are involved in accident and the cause of the accident is found to be your overloaded vehicle, you risk losing life as you know it. An accident that is not really your fault may be blamed on you. Your insurance may not cover the liability because you may technically have broken the law and there may be a clause requiring you to use your vehicle legally to maintain your insurance coverage. You could, as in one case I was asked to consult on, lose your spouse, when unable to stop, you crash into the back of a logging truck during the first week of retirement on the first adventure of your “golden years”. The only professional recommendation I can give is that if you must tow more than your vehicle's ratings will allow, then GET A BIGGER TRUCK.

I would very much like to thank you for the opportunity share my thoughts with you and hope to help many of you with your RV performance needs in the future.

Chuck Arnold, The PowerShop

Note: Chuck has indicated he would be happy to respond to reader inquiries directed through the form he's created at The PowerShop website. Once you've entered the website, click on "More Info" to access the form. By submitting queries this way, a more carefully tailored reply can be provided by Chuck.

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