Understanding Panel Impact Ratio and Dilution Ratio in Car Detailing

When I first got into detailing, I assumed that all foam cannons could use the same dilution ratio. 

But the deeper I got, the more I realised the difference between: Panel Impact Ratio (PIR) and Dilution Ratio. 

If you want your chemicals to work effectively while minimising waste (and cost), understanding these concepts is key. So, let’s break them down in a way that makes sense.

What is Panel Impact Ratio (PIR) and Why Does It Matter?

Photo by Andre Tan on Unsplash 

Simply put, Panel Impact Ratio (PIR) tells you how much chemical actually hits the surface of your car after going through your pressure washer or sprayer. This is vital because what you put in the bottle isn't necessarily what ends up on the car.

If your foam lance is set incorrectly or your pressure washer dilutes too much, you might think you're using a strong pre-wash, but in reality, it's just a weak mixture running off your paint. On the flip side, if it's too concentrated, you're likely wasting product.

PIR changes depending on your foam lance and pressure washer you're using. 

Understanding Dilution Ratios

Photo by mintosko on Unsplash 

Knowing how to properly dilute chemicals is one of the most overlooked yet crucial aspects of detailing. Whether it’s snow foam, wheel cleaner, or an interior APC, dilution affects performance and safety.

How to Calculate a Dilution Ratio

Dilution ratios are written as 1:X, where 1 is the chemical, and X is the parts of water. Here’s how to calculate it:

For example, if you need a 1:4 ratio (which means 1 part chemical, 4 parts water) and you have a 500ml spray bottle:

So you’d mix 100ml of chemical with 400ml of water to get a proper 1:4 solution.

For a quick reference:

• 1:10 → 100ml product + 1L water

• 1:20 → 50ml product + 1L water

• 1:50 → 20ml product + 1L water

Using too much product can be wasteful and even harmful to surfaces, while too much water dilutes effectiveness. Getting this right is key. For more information on proper dilution practices, check this dilution ratio guide.

Apologies for the oversight. Let's enhance your article by incorporating specific Bilt Hamber products from CA Detailing that align with the discussed concepts of Panel Impact Ratio (PIR) and dilution ratios.

This is a video from OCD Detailing that explains the process: 

Bilt Hamber Auto-Foam

When discussing PIR and the importance of proper pre-wash techniques, Bilt Hamber Auto-Foam is an excellent example. This snow foam is designed to be used with a foam lance and pressure washer, allowing you to adjust the dilution to achieve the desired PIR for effective cleaning.

Auto-Foam's PIR Calculation Example

Bilt Hamber Auto-Foam is recommended to be applied at 4% PIR for optimal cleaning. This means the solution hitting the car should be 4% product, 96% water.

How to Achieve 4% PIR

1. Determine Lance Output – Fill a 1L foam lance with water and spray into a bucket. Measure total output (e.g 12.76L).

2. Calculate Needed Auto-Foam – Multiply total output by 0.04 (4%).

• 12,760 ml × 0.04 = 510 ml Auto-Foam

3. Mix Properly – Add 510 ml Auto-Foam + 490 ml water into the 1L foam lance.

This ensures you're using Auto-Foam at its intended dilution, maximising cleaning power while avoiding unnecessary waste.

Boost Your Pre-Wash with the Right Snow Foam

Getting your Panel Impact Ratio (PIR) and dilution ratios right is key, but so is choosing the right snow foam. As we already mentioned, Bilt Hamber Auto-Foam is perfect for heavy-duty cleaning, while Koch Chemie Active Foam offers versatility for regular maintenance. 

If you’re unsure which product suits your needs, check out our guide on the best snow foams for car detailing. Pairing the right foam with precise calculations ensures a deeper clean and better value.

Final Thoughts: Precision Makes Perfect

When I started paying attention to PIR and proper dilution, my results improved dramatically. I wasn’t overusing chemicals, and I was getting the cleaning power I actually expected. Take a few minutes to dial in your equipment and calculations – it makes all the difference.

So next time you mix up your pre-wash or APC, ask yourself: Is my dilution right? And what’s my actual PIR?

Once you start thinking like this, you’ll never look at a foam cannon the same way again.