Power mods calculator
Bigger tires, a heavier truck and thin air all take away the pull it had stock. Pick your truck and engine, then add power mods one at a time: forced induction, a tune, headers, an intake, a snorkel, an exhaust. Each shows what its maker claims and what independent dynos found, and the page tells you how close it gets you to the way the truck pulled new, and what gets the rest back.
How to use this 3 steps
- Pick your truck and engineFactory horsepower and torque fill in. Your tires, gears and weight come from your saved rig, or type them under your truck.
- Add mods one at a timeForced induction, a tune, headers, an intake, a snorkel, an exhaust. Each shows what its maker claims and what independent dynos found, and joins the total as you add it. Stop after any step.
- Read the verdictHow hard the truck pulls for its weight against stock, what took it away, and what gets it back: a mod, a regear or pounds off.
You can skip the folds under your truck when your rig is saved; the page fills them in. Open them to set the elevation you drive at, your scale weight or your tire and wheel weights.
Pick your truck to see how it pulls against stock.
Pull against stock
Where these numbers come from Pull, weight, elevation, how gains count
Gains are the makers’ and the testers’, on their trucks, their fuel and their dynos. Yours will differ with mileage, fuel, heat and how the truck is set up. Use at your own risk.
Horsepower and torque
How gains are counted Claims, dynos, crank and wheel
What each fix buys
Pull against stockOn the highway
EstimateHow this was worked out Air, tires, the climb
Estimate. Real road load depends on wind, tire pressure, the truck’s shape and how it’s loaded. Use at your own risk.
Links go to the makers. Check fitment for your exact year, and California legality where you live, before you order.
How the numbers work
What does “pulls like stock” mean here?
How hard the tires push the truck forward for every pound it has to move, in the same gear at the same engine speed, against the truck as it left the factory with a driver aboard. The push at the tires is engine torque times the gearing, over the tire’s radius. Taller tires lengthen the lever, so the same torque pushes less; deeper axle gears shorten it again. Weight divides what’s left, and tires and wheels count about 1.6 times their weight because they have to be spun up as well as moved. Power mods multiply the torque the engine sends in.
Do power mods fix bigger tires, or do I need gears?
A regear is what fixes the tires. Deeper gears in proportion to the tire put the engine back where it was at every road speed, so the truck pulls the same in every gear. A power mod adds about the same share at every speed, which helps with the tires and the weight alike, but a typical bolt-on adds a few percent while 35s on a truck that came on 31s take about 10%. Weight is the part only more power or fewer pounds give back. The ledger shows each piece, and the list under it shows what each fix would buy on your truck.
Why two numbers for every mod?
Makers publish their best result, often the biggest gain at any one engine speed rather than peak to peak, sometimes at the crank and sometimes at the wheels, on premium fuel. Independent dyno tests by magazines, shops and owners often find less. Where tests exist, the page counts the median of them. Where none do, it counts the maker’s claim as published and marks it untested. Once at least three products in a category have both a claim and an independent test, untested claims in that category count at the share of the claim those tests found, and the product says by how much. Every product shows both numbers, with its sources.
Crank or wheel horsepower?
Factory ratings are at the crank. Chassis dynos measure at the tires, usually 15 to 20% lower on a 4x4 with an automatic because the transmission, transfer case and axles take their share. A gain read at the wheels is a bigger share of the engine’s output than the same number at the crank, so the page divides a wheel gain by 0.82 for an automatic and 0.85 for a manual before comparing it with the factory figure, unless the test gives the stock wheel figure it started from, which is better.
Does a snorkel add power?
A little, at highway speed, and only with the head facing forward. At 65 mph the head catches about half a percent more air pressure than the air around it, so at full throttle the engine can make about half a percent more power: around 1.5 hp on a 300 hp V6, and about 2 hp at 75. A chassis dyno can’t blow that much air at the head, so a dyno test only shows what the snorkel’s pipe and bends cost. Dirt Lifestyle ran a snorkel on and off a built Tacoma on the rollers in How much Power is LOST through Off-Road Snorkels? and found no change beyond normal run-to-run variation, so the pipe costs about nothing and on the road you keep most of the ram air. The page counts it on the highway rows at their speeds and leaves it out of the pull against stock, which compares the same gear and rpm at any speed, trail speeds included. What a snorkel also brings is air drawn from roof height, above the dust and away from the engine’s heat, and an inlet that stays dry in a water crossing.
Do gains add up?
Roughly, and not always. The page adds the counted gains of each category. A supercharger or turbo kit comes with its own calibration, so a separate tune isn’t stacked on top of one unless the kit maker asks for it. Headers and intakes are often tested with a tune; when a product says it needs one and none is picked, the page flags it rather than guessing.
Why does a part count less than its maker claims?
Makers test their own parts on their own dynos, often on a warm day after a few runs, and quote the biggest gain they saw anywhere in the rev range. Independent tests on owners’ trucks usually find less. So wherever we have both for a kind of part, we compare them. Once at least three products in a category, tunes say, have a published claim and an independent dyno test, the page takes the median share of the claim those tests found and counts every untested product in that category at that share. The product card and the Horsepower and torque table say when that’s happening and show the maker’s full figure next to it. A product with its own independent test counts its test instead, and a figure you type in from your own dyno counts as typed.
What about elevation?
An engine that breathes the air as it comes loses about 3% of its power for every 1,000 ft, close to 30% at 10,000. Garrett, which makes turbochargers, puts it at that rate and says a turbo engine’s computer raises boost to hold its power as long as the turbo can keep up. Ford said in 2009 that its EcoBoost V6s keep peak torque to well over 5,000 ft, so the page holds a turbo to 5,000 ft and lets it fall at the same rate from there. A belt-driven supercharger spins at a fixed ratio to the crank, so its boost falls with the air pressure; Ripp sells altitude pulleys to make some of it back.
Which parts are legal in California?
In California, a part that changes how the engine breathes, fuels or burns, or anything ahead of the catalytic converters, needs a CARB Executive Order to pass smog. The EO number is on the maker’s page, and a smog station can look it up. Cat-back and axle-back exhausts sit after the converters and need none, though Vehicle Code 27151 still holds a truck under 6,000 lb GVWR to 95 dBA. Gas trucks from 1975 and older and diesels from 1997 and older skip smog check altogether, so any part goes on those. Passing smog and having an EO are separate things: a tune without an EO isn’t legal on a California road even when the truck passes, and BAR has been reading the engine computer’s calibration ID at smog check to catch software it doesn’t recognize. Switch Parts legal in to California and every list leads with the parts that have an EO or need none. Parts without one whose makers say they leave the emissions controls alone follow in their own group, labeled.
Why isn’t my delete tune or catless downpipe listed?
Removing or disabling emissions equipment on a road vehicle breaks the Clean Air Act in every state, and EPA has fined the people who sell those parts and the shops that fit them. So the page leaves out anything whose job is removing or defeating it: delete pipes, test pipes, catless mid-pipes and delete tunes. Headers are listed, long-tubes included, because the converters can go back in downstream: those cards say they need catalytic converters. Parts their makers sell for off-road and race use only are listed too, in a group of their own and tagged, and they never show as a suggested fix or in California mode. Every product shows its California status: its CARB Executive Order number, or that it has none.
Where do the figures come from?
Factory horsepower and torque come from the makers’ press releases, spec sheets and brochures for each year. Product gains, prices, octane and California status come from the makers’ own product pages and instructions, and the independent tests from magazines, shops and owners’ dyno sheets, each with its link. Anything from a retailer or a forum is marked. Every factory figure on the page can be edited to match your truck.
Use at your own risk. These calculators are here to help you plan and to inform your decisions, not to sign off on a build. Many numbers are estimates worked out from factory figures, and some factory figures are not yet confirmed. Check every number against your own truck, its manuals and a qualified shop before you buy parts, cut, weld, lift, regear or drive on it. Long Range Desert Tools is not liable for anything you do based on these calculators or their results. The full terms are in our policies.