I wanted to share some information that I have learned over the last several weeks about the 997TT intank fuel system. It is different from the 996TT in terms on 997TT uses two pumps. What most people dont know is they are actually staged and neither one is a true primary. Primary pump depends on the level in the gas tank, whether its under or over 13.7gal. One pump has 3 outlets and the oter one has two. Small ones on the bottom are for low pressure driver side jet pump. One of the pumps has an extra outlet on top that feeds the passenger side jet pump, that pump is primary when fuel level is under 13.7gals. It not only feeds the rail but also fills the basket. The pump with the high pressure jet outlet flows about 35% less than the pump without the jet outlet. Another interesting point is that there are no checkvalves so the must be built into the pumps, anytime you run a multi pump system you need one way checkvavles after every pump.

Here is a tech page on the setup ..



The return line is now under the battery tray


Few pics of the basket





We were simply going to throw two Walbros in there and continue on but that proved to be a PITA task. the factory basket is glued shut unlike the 996tt where there is just a few pry clips.



Few pics of the low pressure jet pump feeds from bottom of the pumps..







The return line



we took the basket apart but not sure we will reuse it or not. thinkinging of feeding both jet pumps from one Y just like 996TT does it and other sied of Y will Y in with the secondary pump which is fairly straight forward. Walbros are also a tad large or the factory basket but I think we can make that work.

Has anyone else tried to tackle this project?

 

Is your fuel pressure dropping under load currently?

Dzenno@PTF

 

at 18psi AF was extremely stable. at one more psi the A/F got wawy last thousand RPMs or so. car still had pump gas timing and was making a tad over 600awhp on Mustang dyno on E85. Tony told me he runs out of pump on Ethanol around the same time we did ( we are using same dyno as his).

I have seen guys make 900whp on racegas on stock pumps on a dynojet so it makes sense we started running out where we did on Ethanol. Getting some fittings made to run the Walbros in tank and have them run the jetpumps like factory. Hopefully will be done today.

 

How much boost were you running? Are you logging actual boost using an external datalogger or on the dyno and confirming its not boost maybe that's getting wavy or throttle closing causing the swing in lambda? Have a fuel pressure sensor wired in? Unless you're using a standalone I'd suggest getting the PBC Pro EBC and hook up a fuel pressure sensor for failsafety just in case.

Great work by the way.

Dzenno@PTF

 

Logging boost on Cobb and the sensor on the dyno. 19psi. Using an HKS EVC 6. The boost curve is amazing, flat, not a single dip or hickup. Throttle was 100%, we had throttle closing stuff friday but he figured that stuff out already so we are now past that point.

600awhp doesnt sound like alot but once you take into account 30% Ethanol eats up on supply, it sounds about right. We'll know soon enough.

 

Cool. Just FYI you won't have boost visibility in the Cobb logs as the OEM tmap is a 2.5bar but your EBC will see it. By the way, what turbos are on the car atm?

 

I'm very glad that you posted this, I'm pretty much at the same point with my car. Is that a shop manual you have taken a couple of photos of?

I would love to drop a couple Walbro pumps in my car as well to get a bit more flow out of it. I'm not sure where the lines and/or filter/FPR are going to become a limiting factor though.

It would be great if you could post some more information when you get it completed. I would like to do something similar with mine.

 

If you're flow limited you'll want parallel pumps. If you're trying to maintain pressure mostly I'd just add an inline pump. I wouldn't really modify lines, rail etc. on the first go and try the easy wins first. My 2c

 

yep its same as 996 sensor runs out at 22psi of boost too. i heard cobb allows you to use a different MAP sensor to get around this. i believe Cobb, BBI and FVD are doing this for the 997.2s already so it will probably come over to the .1s as well soon. There are 3bar and 4bar sensors availabl from what i hear. 3 bar would be perfect for now for what we are looking to do. i am using FP billet HTA30Rs with external gates

 

FP =

I have been told that the 3 bar support for the 997.1 will be available "soon" with Cobb.

 

COBB has added support for aftermarket MAP sensors on the 997.2 and we're already tuning with them in place. I'm looking forward to them adding it to the 997.1. At the moment on the .1 you can sort of make out what your boost is doing by looking at some other loggable parameters in the logs such as MAF that sort of help but not ideal obviously.

Excellent choice on the HTAs What AR? We went with the FP HTAs on our big turbo BMW kits as well. Curious why you didn't like the Alpha 30s, internal gates and OEM .1 manifolds? What are your goals with the setup?

It'll be a great comparison to our project car once we're done. There's another local .1 car going GT30s, custom manifolds and EWGs soon that we'll be tuning. We'll throw them all in the mix and am looking forward to see what setup from the hardware point of view works out the best from the response/spool characteristics.

Dzenno@PTF

 

I used the .63 A/R T3 hotsides with pre turbine EGT bungs for stock sensors. I have use many different turbos on my 996tt ... FVD Race K24s, Old tial K24/GT3076 hybrids, Alpha3076, PTE 6262s, PTE 6466s. Problem I found with the Alphas was that the tighter stock location hotside created back pressure and with internal gates they were running out of steam. nice external gates will give better control down the line at higher boost levels and power levels. I am also using 3071s not 76s but my hotside is bigger so power delivery is a bit smoother. I had a wide powerband in mind and ability to push further on same turbo once motor is built and 30s give you just that. Overlaid vs stock my car doesnt make any less HP in any rpm vs stock turbos, 30s are perfect IMO.

 

997.1 exhaust manifolds are a better flowing design than the 996 OEM though. I'll be testing with some non OEM 997.1 headers back to back once we get them to see what improvement they might have but I'm not sure at this point we'll see much given power goals in mind. If anything I suspect it'd lose a bit of low end response/spool going wider primaries, "maybe" a little gain on the top end, not sure, we'll see.

Great choice of AR. This one right? http://store.forcedperformance.net/m..._Code=Turbo-FP

We haven't hooked up EGT probes on our setup but I've been thinking of adding them back on on the manifolds and/or on the aftermarket ones when we get to trying those out. Adding backpressure probes?

Excited to see what you guys end up with in this setup. Good luck

Dzenno@PTF

 

nm, just saw prodigy isn't use vtgs.

Still curious about this question though:

Did you strictly use obd or did you wire up all the individual pickups for the ebc?

-Jose

 

I thought it'd do the VTGs given their pamphlet as well but apparently not. It'll do the 996, conventional WGs. At the moment you need an external form of boost control on the 997.1 for two reasons: 1) to control a conventional non-VTG setup 2) to see/control boost appropriately past the OEM 2.5bar TMAP. Hoping to see Cobb resolve these two issues soon and we can remove the EBC entirely from the car and have the DME run the show entirely.

Wiring it up is really the only way to do it right. If you use the OBD setup you lose visibility when datalogging as you can't have two things running concurrently on the CANBus at the same time, e.g. Cobb AP/ATP using OBD as well as PBC using OBD.

Dzenno@PTF