Some Of The More Common Potential Engine Concerns When Stock or Tuned.
- Pistons on the B4x Gen 1 are known to be fragile in nature, whilst there are 3 variants of the B4x/B4xTU/B48A20T1 engines that come with either a 9.5 compression, 10.2 compression and 11 compression configuration. The B48A20T01 that comes with 9.5 CR pistons are forged and are not really considered to have any issues, this information mainly pertains to the B4x Gen 1, B4xTU really don’t have as much of a problem due to running 10.2CR vs 11CR pistons.
The main cause for piston failure is poor quality fuel combined with lean AFRs, around 90% of the B4x Gen 1 cars come with the 11CR pistons. These pistons are very sensitive to low quality fuels, what we have seen is a lot of tunes tend to run fairly lean AFR targets which combined with poor quality gasoline based fuels runs the cylinders way to hot and causes premature piston failure. Another cause for concern is the intercooler on water 2 Air B4x’s whilst this intercooler is considered an upgrade over the N2x platform its really more like a “stage 1” intercooler and in hot climates we have seen IATs reach well into the 120-140F range! (Over 120F is a concern, and over 130F is dangerous at WOT) as this causes the piston rings to fail or pistons to crack.
Typically since a very large majority of the B4x engines made are with the 11 compression engines they have the highest failure rate. For higher compression engines you need better octane to minimise knock/detonation due to the increased compression.
10.2 CR based B4x & B4xTU engines are less prone to piston failure as the lower compression allows for lower quality octane fuels to be run with less chance for heat damage. However it is worth noting that there are some tunes out there that do run quite lean on the AFRs which is fine if you are running really high quality fuel.
- HPFP “High Pressure Fuel Pump” these pumps pressurise the fuel from the fuel tank and prepare it for the Direct Injected Injectors to deliver fuel to the cylinders. The issue with this pump is if the tuner is not careful or people push their car too much on Ethanol mixes or larger turbos, the HPFP starts to fail at delivering correct amounts of fuel the AFRs go lean and piston/ engine damage or component damage occurs. Whilst this does offer a 20% fuel flow rate improvement over the N20 HPFP and Pump Cam Lobe design there are still limitations on larger turbos and E85 blends.
- Driveshaft, Flex Disc breaking We have seen some issues in the community where the flex disc “guibo” has sheared away prematurely or the driveshaft has snapped. Because the B4x have forged rods alot of tunes tend to run alot more low RPM TQ, combined with an XHP gearbox flash you end up loading up the gearbox and drivetrain to much when doing launch control, resulting in driveshaft or flex disc failure. It is worth noting though we have seen this happen on 20i B4x over 500nm of TQ to the wheels on DynoJet based dynos with a XHP flash and an aggressive tune. We have seen this on B48 Hybrids and B48 30i cars running bigger turbos, or really aggressive tunes if you are worried about this happening or have had this happen already the solution is either:
- Have the tune reduce TQ demand during launch or below 3000RPM.
- adjust your XHP launch control settings to reduce shock TQ loads during a launch.