Bump. Any more info to share?

My car found the LPFP limit. The HPFP flows better than the LPFP. At a certain speed the lamda requirement lowers requiring even more fuel at WOT (ECU adding fuel to keep EGTs constant on sustained WOT) and anyone making say 650+ wheel will experience fuel cuts due to the LPFP not being able to keep up with the fueling demand. Unless you know how to program around it you have to keep power down to maybe 600 wheel. The HP numbers are an educated guess only. Running a lot of meth helps to prevent the fuel cuts as well but still needs the ECU programming to work.

 

In-tank same as 997.1 or is a pwm brushless system?

 

You should be able to find a LPFP solution fairly easily.

 

From what I understand (which isn't much), the hardware isn't the issue...it's the software. It's why, even after 3+ years of development, there is still no effective fueling upgrade solution beyond 650-ish wheel HP.

 

Perhaps you meant the other way around. It isn't a software issue, it's a hardware issue. This isn't new or specific to the porsche platform. This is an issue that every DFI platform has. The BMW community has been dealing with this since 2007 and they have yet to find a real solution. Specifically, it's an issue with the HPFP.

 

If it was simply a hardware issue, I think BBI would have solved it after years of R&D. They have built two 997.2 DI motors already. Both to 4 litres and upgraded turbos. They can't increase wheel HP on these cars beyond 6XX because they are still limited by the stock fueling. They have the hardware, but I don't think it's as simple as hooking up a more powerful LPFP to feed the HPFP. If it was, these cars would be at 1,000+ HP long ago. But they aren't because BBI did not have a fix the last time I went for a visit. They are trying believe me. I think additional programming is needed to make it all work, and this is by far the most complex part about the project. Maybe I'm wrong. But maybe not.

 

It doesn't matter how much software you have, if the high pressure pump can't keep up you're going to have a bad time.

 

The HPFP is the limiting step. They are very precise pumps that take very very expensive tooling and machining to build. It is rare to have an upgradable high pressure pump. APR spent over a million bucks on their Hitachi HPFP upgrade but they have a much larger economy of scale. It includes a new larger cylinder and piston in the pump and require diamond micofinishing, etc to do it right and reliably.

As per Cobb the 991 has a higher capacity HPFP than the 997.2 and wil subsequently be able to make more power.

 

Maybe the 991 pump can be used on the 997.2? That would be an incremental step.

 

I believe Champion experimented with that and said it was not a direct bolt on.

They paused 997.2 fuel system development the last time I spoke with them due to weak demand from the high HP 997.2tt junkies. There doesn't seem to be a lot of us outside of this forum.

 

Based on an EWAG (Engineered Wild Assed Guess):


44 HP-hr/gal (gasoline energy content) * 374 liter/hr (fuel pump rate) * 1 gal / 3.79 liter (conversion) * ~25% thermal efficiency @ WOT = 1085 HP


This too high strictly theoretical number is just based on the fuel flow rate and energy content in the fuel, there are many other constraints (air flow, heat rejection, mechanical strength of components, etc.) that limit what a real life engine can produce.

 

So how much power can I be running with just 3" short straight pipes either side and a tune? My car had fuel pump limitations just with these mods unless my exhaust makes a big difference. We had to lower boost at top of rev range etc

 

@MONKEY LONDON, there are two fuel pump types on 997.2 and later DFI turbo motors. One setup is a low pressure one with pumps in the fuel tank. This setup supplies fuel to a high pressure fuel pump (HPFP) which multiplies pressure from the low pressure side supplying it to the rail at 5-600psi at idle to 1900-2000psi at WOT. Given fuel pump flow testing on the LPFP (low pressure fuel pump side) we should be good to at least 900-950hp crank which at this point no one is near from the tuning point of view. Its the HPFP side that is the first bottleneck on pump gas. If we were talking about running straight E85 on the 997.2 though then an LPFP upgrade would most likely be the first one necessary due to ~30% higher fuel demand on the fuel system over gasoline.

Dzenno@PTF