Advice/Comments - AFR above 12 by 5300rpm

[flat_6]

Thanks guys, really appreciate your help.

To answer a previous post, here are pics of my homemade pump tester using the fuel filter fittings

[Lapkritis]

I'm talking CIS here.

If you put a weaker flowing pump in series then it will choke the 044 unless you use a surge tank and have the weaker pump in series before the 044. A weaker pump downstream will not increase pressure; it will free-wheel with the higher flow 044 pressing against it while slightly increasing the work the 044 handles.

Now, if you put a 044 in series with a weaker rear pump and no surge tank then you'll be straining the 044. This will present as heat fatigue; when the pump gets hot the engine will show as lean mixture or hot start issue with fuel boiling in the pump body.

The pressure / flow make of the 044 are excellent relative to other pumps available. If I were building a serious 911 I would use the Integrated Engineering dual 044 surge setup. Run a stock rear pump to fill the surge/pump bath and relay the pumps with 10g wire directly to the battery.

http://www.intengineering.com/integrated-engineering-submerged-dual-044-billet-surge-tank-with-pumps

[Lapkritis]

Originally Posted by Ken911

Actually when running CIS there are two pumps in series to get the pressure high enough.

This is incorrect if you're using simple addition of pressures. This is correct if you mean you're using a pump at the tank end to fill a surge for the primary pump near the engine side that will be doing the work. I.e, a half dozen tired pumps that produce 10psi each won't get you 60psi when chained together.

6.2 bar is 91 pounds. And for proper delivery if you have a lot of mods sometimes system pressure has to be close to 7 bar. For EFI systems your only running about 40 psi. The 044 pump is a good replacement also for the rear pump since it's failed. I missed the part in your post where you said the rear pump was bad. Normaly thought when you just cant get enough gas the front pump is the weakest of the two. The Stock rear pump can take anything the 044 pump can send it.

Not all conventional systems operate at 40PSI. I used a Bosch CIS pump on an efi engine with a RRFPR for a number of years. The system would peg the 100PSI gauge at the fuel rail with 17PSI manifold pressure. When not in boost the system operated at 4bar.

[JFairman]

Originally Posted by RarlyL8

The accumulator is a surge tank. The -044 pump is a common uprgade that has been used in front, rear, or both. Any position will relieve the remaining OEM pump to some degree. As with all performance mods the system must be verified in spec after the mod and tuned/adjusted as needed.

This is incorrect information.
The CIS fuel accumulator is not a surge tank.

Surge tanks are installed before the main pressure fuel pump(s) and the surge tank is supplied fuel from the main fuel tank by a dedicated seperate fuel pump.
Their purpose is so when the fuel tank or fuel cell in a race car is almost empty the the main fuel pujmps will still have a steady non intermittant fuel source to draw from during hard cornering and not be starved for fuel when the remaining fuel in the main tank moves away from the fuel pickup.

935's and 962's had two fuel pumps in parallel feeding the surge tank that looked like the same fuel pumps that were in the old bosch mechanical fuel injection Mercedes cars from the late sixites before they started using CIS in the early seventies.
Then they used 3 bosch fuel pumps in parallel that look a lot like the rear bosch fuel pump in the 930.
They used more fuel pumps than needed to run correctly mounted in parallel in an aluminum frame in case one failed during a raceand with 3 pumps the car would keep going and not be a DNF.

The 930 fuel tank has the plastic swirl pot in the bottom of the tank with the fuel pump pickup in the middle to keep some fuel available to the fuel pump during hard cornering, braking, and acceleration when the fuel level is low.

Race cars use a rubber fuel cell full of pieces of special open cell foam rubber to keep fuel from sloshing around during lateral G forces while driving..

[fredmeister]

Originally Posted by flat_6

Thanks guys, really appreciate your help.

To answer a previous post, here are pics of my homemade pump tester using the fuel filter fittings

Thanks for the post.

My CIS tester does not even remotely have all the fittings needed.

Fred

[JFairman]

Or you can just buy one here...
It just keeps going up in price... used to be about $60 six years ago.

Star Products , TU-14PB Fuel Injection Tester - Bosch C.I.S.

[RarlyL8]

Surge protection, or more aptly pulse dampening, is most certainly the function of the fuel accumulator. There is no need for race car sump baffles and such for a street CIS 930. KISS rules.

[Lapkritis]

A proper surge setup can work wonders for any high performance primary pump. It mitigates the need for tank baffles to a certain degree although ideally you would run both for a high performance track vehicle. Street car? I would prefer proper surge if I had to choose between the two. This ensures the primary pump is not labored with drawing fuel on the inlet side. The benefit then is for wot pulls and acceleration exercises rather than for cornering starvation although both are addressed with a simple surge.

[9Thirty]

I'm having the same problem, put the car on the dyno and she is perfect at a 11.5 AFR until she hits 4500 rpm or so and then starts to go lean. The good news is that she pulled 393 rwhp and 457 rwtq, but was in the mid 12 afr and climbing. We adjusted the Leask but it didn't change, going to check the fuel pumps Monday. If they need replacement, what do you guys think of these choices? Has anyone toyed with the idea of installing bigger injectors (964)?
Bosch Fuel Pumps - BoschFuelPump
Fully Enclosed FP34 044 Fuel Surge Tank, FP34 - 034Motorsport | Performance Parts for Audi, Porsche, and Volkswagen
Fuel Pump | Bosch 044 Motorsport | 3.8L RSR - GT2 Porsche Part Distributed By Patrick Motorsports

[JFairman]

From what you've already done the next step is to send your CIS fuel head to Home - CIS Flowtech if you want more fuel at high rpms. Or ditch it and go EFI.

[flat_6]

Ok. I changed the rear pump to a Bosch 044 and also ran independent power from the battery to each relay. I also ran a new dedicated power to the rear pump and now have only a 0.5v drop from the battery to the rear pump. It was 1.5v drop before. I then readjusted the WUR.
Currently system pressure of 6.4bar, cold 1.7bar, warm 3.6bar, boost 2.1bar (this is as low as it will go)
With this I am still going lean buy now it's at 5600rpm.
What's left??? Help!

[flat_6]

bump....need help with next steps

[fredmeister]

You could try dropping the warm control pressure a certain amount and the boost control pressure will drop along with it.
At least it should. This will fatten up your normal cruise running AF ratio but will also fatten up your boost AF at the same time which is what you are concerned with right now.
You might be able to lean out the new cruise AF ratio by adjusting the allen screw on the fuel head.

Dont know what else to tell you unless you are simply at the limit of fuel flow on your fuel head. Worth a try.

let us know what this does.

Fred

[fredmeister]

Originally Posted by flat_6

Ok. I changed the rear pump to a Bosch 044 and also ran independent power from the battery to each relay. I also ran a new dedicated power to the rear pump and now have only a 0.5v drop from the battery to the rear pump. It was 1.5v drop before. I then readjusted the WUR.
Currently system pressure of 6.4bar, cold 1.7bar, warm 3.6bar, boost 2.1bar (this is as low as it will go)
With this I am still going lean buy now it's at 5600rpm.
What's left??? Help!

You could try dropping the warm control pressure a certain amount and the boost control pressure will drop along with it.
At least it should. This will fatten up your normal cruise running AF ratio but will also fatten up your boost AF at the same time which is what you are concerned with right now.
You might be able to lean out the new cruise AF ratio by adjusting the allen screw on the fuel head.

Dont know what else to tell you unless you are simply at the limit of fuel flow on your fuel head. Worth a try.

let us know what this does.

Fred