The MAP sensor on the 7.3 Powerstroke is limited to around 22-24psi of boost. Once you start pushing the turbo beyond that range you will start getting a check engine light with overboost codes.
The overboost codes then cause the PCM to start defueling which results in decreased performance. The way to fix this is to install a boost fooler, to trick the engine into allowing boost pressures beyond 22-24psi without defueling.
I run a boost fooler on my 7.3 F350 – but if you are running a custom tune you might be told you don’t need to. I’m going to cover the purpose of a boost fooler, how it works, and discuss why you need one, even if your tuner says you don’t.
What is a Boost Fooler?
A boost fooler is a simple 7.3 Powerstroke upgrade that will allow you to push past 24psi of boost on the stock turbo and prevent defueling, which starts to happen at 22psi of boost.
Boost levels are monitored by the MAP sensor. A boost fooler works by connecting into the MAP sensor and basically fooling it to believe that the turbo is operating at 22psi of boost – so that you can boost beyond that without defueling and losing performance.
There are 3 different types of boost foolers. They all do the same thing but they work differently:
- Electrical: these piggyback the MAP sensor reading and tell the PCM boost is never more than 22psi to prevent overboost and defueling
- Relief Valve: this acts like a blow off valve and bleeds boost – it basically feeds the MAP sensor a lower boost level than the engine is actually receiving
- Regulator: a mechanical solution that basically feeds less boost air to the MAP sensor in order to read lower levels – it is adjustable so you can control the reading
Before I get into which one is better and which one you should run – let’s talk about why you need one in the first place.
Does My 7.3 Powerstroke Need a Boost Fooler?
The short answer is yes. A lot of programmers, chips, and custom tuners will say that their tunes do not need a boost fooler. And they all will prevent the check engine light for overboosting.
You can tune around the defueling and prevent the PCM from pulling fueling through custom tuning which is why tuners tell you that you don’t need one.
The caveat is that tuning around it and tuning out the light causes you to lose low boost fueling. KC Turbo’s explains it well, but basically the low boost fueling tables get tuned out which leads to slower turbo spool and causes your engine to run worse (and hotter) during normal driving.
A 7.3 Powerstroke will run so much better with a boost fooler, even if your tuner says you don’t need one. I run one, even with my custom tunes, and the difference is astounding vs not using one.
What About OBS Trucks?
The 1994-1997 7.3’s don’t have the same problem as the 1999-2003 models do and therefore don’t typically need a boost fooler. There are some instances where you would want to run one if you are heavily modified but I’d suggest working with your tuner on this one as it usually isn’t needed or recommended on OBS trucks.
Best 7.3 Boost Fooler
I personally run an electronic boost fooler and that is my recommendation for anyone looking for one. There really isn’t a wrong option – you can DIY a regulator style one for like $30 which is a popular option but everything on the market is only $70-$80.
Relief valve style foolers create a boost leak to work which isn’t ideal and the regulator styles are more likely to self-adjust and cause problems. Overall, the electrical foolers have the least problems and that’s why I run an electrical one.
Here are the main ones, they’ve all got good info on their benefits and how they work:
- Full Force Boost Fooler: mechanical regulator style or Driven Diesel Annihilator
- ATS Fooler: electrical style
- DieselSite Boost Relief Valve: valve style
Ultimately, running a boost fooler is probably more important than which style you choose. No option is really the wrong option – it’s more so preference. Moral of the story is spend $80 and get a boost fooler – don’t listen to people telling you you don’t need one.