MFI Calc

About this site

This site provides access to our jetting calculator (MFI Calc). It is to compute jetting and other setups values for racing mechanical fuel injection (MFI). This is useful for racers who set up mechanical fuel injection engines, usually for motorsports. MFIcalc access includes several membership packages:
  • MFI Calc (formerly ProCalc -- through
  • MFI Consult (formerly ProTune -- through
  • MFI Consult Advanced (formerly ProTune Advanced -- through
MFIcalc determines jetting changes for the following:
  • air density changes throughout a race day or weekend
  • engine revisions; example: engine size changes, camshaft / cylinder heads changes affecting volumetric efficiency, fuels changes such as adding nitro, and others.
  • fine tuning MFI setups to target a performance record or other competitive purpose.
Changes to blower overdrive (in those engines so equipped) can be determined with MFI Calc. This is done to maintain power for  a performance target, such as in bracket drag racing categories (on land & on water motorsports).
MFI Calc is linked to This site provides current air density data for tuning in over 1,000 motorsports facilities worldwide. Air density & other data for tuning includes:
  • temperature, humidity, & barometer
  • air density, density altitude, dew point, & grains of water
  • racing facility orientation &  altitude
  • wind speed & wind direction relative to the facility orientation
  • up to 2 day hourly forecast
  • up to 5 year hourly history for most locations.

MFI Calc works on most common web devises with web access:
  • smart phone
  • note book
  • lap top
  • desk top.

FAQ: MFI Calc & Consult | FAQ: DA Calc & Tracks | Articles | Disclaimer | The Developers | Credits
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FAQ: MFI Calc & Consult (formerly ProCalc, ProTune, & ProTune Advanced)

(I) How much do these cost and what do I get access to?

MFI Calc (formerly ProCalc) is an annual subscription for $89.99. This will get access to all 3 jetting calculators and the air-fuel ratio calculator.
  • Up to 3 MFI baselines can be stored for different engine setups
  • Access these baselines with 4 different jetting calculator formats: get mbp, get nozzles, get jetting from pressure, get air to fuel ratio (AFR)
  • Access your membership from most anywhere with internet access, especially internet-enabled smartphones.
  • Access your membership from more than one device.
  • Data can be exported as a csv (comma separated values) data string file. Note: This file format can usually be displayed by a spread sheet file in a computer program such as Microsoft Excel or Apple Numbers. It is for keeping extended records.
New features may be added. Learn more about MFI Calc here.
MFI Consult (formerly ProTune) is a one time payment of $249.99.
  • All of the services from MFI Calc (formerly ProCalc) are provided
  • Custom training & assistance is provided for racers to set up their ideal fuel injection baseline; primarily on a single setup.

MFI Consult Advance (formerly ProTune Advance) is a one time payment of $599.99. This package is similar to MFI Consult, but more extensive.
  • more detailed custom analysis using your current data
  • analysis of a dynamometer test (if available) & calibration to that test
  • analysis of flow bench test (if available) & calibration to that test
  • consultation in setting up a new combination.
Some examples of MFI Consult Advanced additions to one or more optimum MFI setups:
  • computing intake port velocity to determine boost limits
  • cam shaft timing analysis, assistance in combining MFI with nitrous oxide
  • consulting for adding nitromethane
  • consulting for applications up to 7,000 horsepower
  • consulting for land speed racing
  • consulting in a foreign language using an email translator program.
We have experience with thousands of optimum mechanical fuel injection (MFI) setups in most applications around the world.

(II) Renewing your MFI Consult or MFI Consult Advance memberships

Near the end of your Consult membership, you will be notified of the expiration without any further obligation or charges. You will also be offered a renewal at the current MFI Calc price ($89.99 at this time). Added training & consult services are available however.

(III) How do I sign up?

  • For the MFI Calc membership, go to the MFI Calc page and click on the purchasing links page.
  • For the MFI Consult or MFI Consult Advanced memberships, go the the MFI Consult page and click on the purchasing links mambership of your choice.
  • From there you will be taken to third party website where your payment will be processed.
  • The site can process a single credit card transaction.
  • If you have an account at that third party site, you can choose to charge your membership to your account as an alternative.
  • Upon successful completion of payment, you will be redirected to the registration page for the MFI Calc website.
  • There, you can create your login name & password.

(IV) How long does it take for me to get access to MFI Calc and/or Consult?

MFI Calc access is granted as soon as payment is received. You will be emailed instructions to complete your signup as soon as your order is processed.
  • If you do not receive an email from us, check your spam folder.
  • If you still have not received an email, contact us and we will assist you.
Consult and Consult Advanced access takes a bit longer to get setup. As soon as your payment is received, you will be emailed instructions, and you will be given immediate access to the Consult area of MFI Calc. Please allow up to 5 business days to finish your Consult setup. Also, please be aware that we may contact you by email for further information regarding your setup. If you have further questions regarding Consult, contact us for further information.

(V) What is your refund policy?

MFI Calc customers have 30 days from date of payment to request a refund. We will remove your access and refund the full amount of your payment. To request a refund, contact us here. Consult and Consult Advanced customers can request a refund if they have not yet submitted information about their setup. Once we have your information and begin configuring your setup in our system, a 50% refund may be granted if we have not yet completed your setup. To request a refund for Consult or Consult Advanced, contact us here. Read more about our refund policy on our Terms and Conditions page. Any questions regarding our refund policy can be made by filling out our contact form here.

(VI) What types of fuel are supported?

Methanol is the main fuel that is supported on this site. E85 is also supported. We have MFI Calc procedures for other ethanol blends as well as racing gasoline. Contact us with questions regarding your application. Nitromethane is supported as well. When using the calculators, an option to enter a percentage of nitro up to 100% is available. Percentages are calculated either by weight or by volume. This option allows you to test your setup using methanol while also by adding percentages of nitro to your setup.

(VII) What kinds of engines are you supporting?

Normally aspirated engines with MFI are supported. That would include:
  • stack type
  • hat type (manifold or tunnel ram mount)
  • throttle body type (manifold or tunnel ram mount).
Supercharged engines with MFI are supported with single or multiple rows of nozzles and bypasses:
  • Roots or screw supercharger
  • centrifugal superchargers
  • turbocharged racing engines.
Note: These setups include those using mechanical or slide valves for fuel bypass. Slide valve examples are the Hilborn variable boost valve, the Pete Jackson bypass valve, Don Jackson BDK valve, and the Don Jackson All Valve.
Other engines with MFI:
  • 2 cycle engines.
  • rotary engines.
MFI is supported for most any unique MFI setup such as in opposing cylinder engines and radial engines. If you are unsure if our MFI calculator will work with your engine, please contact us for further assistance.

(VIII) MFI calc capabilities & limitations

MFI Calc currently has data inputs for 1 to 8 cylinders, up to 4 nozzles per cylinder, and up to 3 bypass's (mbp, hs, 2hs or pump sizer). We have procedures for setups that may exceed these numbers. MFI Calc limitations -- applications that are NOT SUPPORTED at this time:
  • carbureted engines
  • electronic fuel injection (EFI)
  • fuel determinations for added nitrous oxide (NOS).
  • compression ignition (diesel) engines.
If you are unsure if our site will work with your engine, please contact us for further assistance.

(IX) What are the advantages of using air to fuel ratio?

Air to fuel ratio is a proven method of maintaining the optimum combination of air & fuel for the purposes of combustion within your engine. By maintaining this ratio with changing weather or elevation, you will be able to maintain your engine's peak performance despite environmental changes. Air to fuel ratio is the fundamental value used in EFI for fuel control. MFI Calc provides that information to mechanical fuel injection as well.

(X) I'm not familiar with tuning using air to fuel ratio. Will I be able to easily understand your site?

The first time you log in to MFI Calc, you will be prompted to create a fuel injection jetting baseline using easily accessible information about your engine setup. An air to fuel ratio will be calculated from that. It can be used as a starting point for fine-tuning your setup. In addition there is an extensive help section along with 'help' videos available to MFI Calc members.

(XI) MFI Consultation services

If you are still unsure about going it on your own, we created MFI Consult & MFI Consult Advanced to further assist you in getting setup. With these services, we will get details about your engine setup and consult to create you first baseline. In addition, we will provide detailed information about your specific setup, training, and guidance in an optimum combination. We did thousands of MFI setups throughout the year with our calculator & hands-on racing experience. Click here for more info about MFI Consult services. If you have dynamometer data, flow bench data, or an extensively customized setup, we offer MFI Consult Advance further services. That is also highlighted on the Consult link.

(XII) Do you have any plans for developing this site further?

Further development for the site & our calculator:
  • MFI combined with nitrous oxide
  • expanded use of variable high flow, slide valve MFI setups such as Top Fuel
  • application of electronic controlled bypass for MFI
  • MFI for higher horsepower setups: 800+ cubic inch normally aspirated engines
  • MFI for 5000+ HP forced induction engines
  • MFI for compound supercharging
  • MFI for Budack cycle engines
  • MFI for Miller cycle engines
  • MFI for engines with early closing intake valves
  • intake port velocity calculation to determine boost limits
  • EFI fuel map development
  • racing carburetor jetting.
If you have ideas for features, please contact us.
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Helpful Articles

We wrote several articles for our website & for various publications. These may assist you with weather data & engine tuning. They will help you get more use out of this site. Check this page often for the latest articles.

Visit articles page


Please note:
  • This site is a reference for racers to check their mechanical fuel injection jetting.
  • It is not intended as a diagnostic tool for complete engine function.
  • Checking results against other qualified sources is necessary.
  • Many engine setup & tuning needs go beyond the intent & capability of this site.
  • Ultimately the racer, crew chief, or car owner has final say in which engine modifications are made.
  • Information throughout this site is not intended to apply to motor vehicles required to meet air resources board or any other emission control standards applicable to internal combustion engines.
Full details of our legal policy can be found on our legal page. Any questions or comments regarding this policy can be made on our contact form.

Meet the developers

Meet Bob Szabo -- I am a graduate engineer, long-time drag racer, circle boat racer, & author at I wrote and published materials about engine tuning for racers using air to fuel ratio (AFR). I am an advocate for using AFR tuning for greater control and repeatability in engine tuning. You can learn more about my background in my bio on
Meet Jennifer Szabo -- Jennifer Szabo is my daughter and a professional web developer who grew up around drag racing. She helped write & edit our fuel injection and racing fuels books on Jennifer is the web developer of She also developed MFI Calc. She applied the math for mechanical fuel injection fundamentals to this web program. Jennifer also developed this website. Her main contribution to this site is as the programmer who keeps the site running on the web. She developed This site provides racing weather info for over 1,000 motorsports facilities world wide. Jennifer and I enjoy interacting with racers. If you have any questions regarding the use of this site or racing in general, send us a question, and we will do their best to answer it.


Information and math related to air density and engine calibration came from publications/news/forums provided by FAQ: MFI Calc & Consult | FAQ: DA Calc & Tracks | Articles | Disclaimer | The Developers | Credits Return to top

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