Advice/Comments - AFR above 12 by 5300rpm

[flat_6]

Not sure what to check next?

I have my BLWUR enrichment adjusted to the point that it will not drop the CP any more. I got 1.6 bar @ 26*C.

I have checked the flow rates and got;
Entering Fuel dist. = 2200cc
Entering WUR = 473cc
System pressure = in spec (checked at mechanic)

Here is the data from this morning

Second gear


Third gear

[Lapkritis]

Fuel pump tired or low voltage at the pump...

[9Thirty]

Are you sure you don't mean 4300 rpm?

[flat_6]

Red dotted line on the graph is AFR=12. Maybe I am missing something, what are you seeing?

Thanks,

[9Thirty]

Originally Posted by flat_6

Red dotted line on the graph is AFR=12. Maybe I am missing something, what are you seeing?

Thanks,

I was looking at the numbers at the bottom of the graph that appear to be a guide for the rpms. They are listed in 200 rpm intervals. The gold line appeared to be the AFRs. So it appears to me that it hit 12 AFR at 4000 rpm in second gear and 12 AFR at 3000 rpm in third gear. It is hard to read the numbers on the left side of the page vertically. Is that where the rpm numbers are listed for reference?

[smurfbus]

X-axis is time! Read the little boxes.

Fuel pump checks (possibly swap to bigger pumps), 7 bar system pressure and if not enough a split second controller for the WUR like Thierry did. First I would check the flow at the injectors and make sure its close to even when metering plate is fully pressed.

[flat_6]

Thanks for the tips. I will confirm fuel pump voltages and system pressure. I still need to check the injector flow, this has been on my list for too long.

[Lapkritis]

The pressure only needs to drop a little when under loads. This can be due to a pump showing wear; it will hold pressure fine at idle but not as flow increases with engine loads. A fuel pump controller that ramps voltage up (Mallory or msd makes one) with a boost signal input is a nice tool to get the most from your existing system and future upgrades.

[Lapkritis]

Here it is:

http://www.msdignition.com/Products/Accessories/Fuel_Acc_/2351_-_Programmable_Fuel_Pump_Voltage_Booster.aspx

This is one of the secrets to matching fueling with increased boost. Worth every penny if you want to go faster just make sure you have a good healthy pump first.

[flat_6]

I didnt think that boosting the fuel voltage in relation to boost work with CIS system.

[flat_6]

I checked the system pressure and found it to be in spec for my fuel head, 6.2bar. I increased it to 6.6 bar and reset the WUR and still have the same results of going lean at 5300 rpm.

Fuel pumps are working correctly. I verified the voltage at the front pump and is only dropping 0.25v vs the battery.

Now what??

thx.

[Lapkritis]

A tired pump is my bet. It simply won't flow enough at the top end even with adequate voltage.

[RarlyL8]

I don't see what your engine mods are. The stock spec head will support about 375WHP.
At ~97psi you should have plenty of pressure to sustain the AFRs. I cannot read your graph well so unable to see if a hint is there.
If a pump is weak idle and cruise will be rich and on-boost lean. Curve tuning will be difficult.
Please list your mods as that is a go-no go gage.

[flat_6]

If you click on my user name and then my garage you will find all the specs and mods on my car.
Thanks for the advice so far guys.

[RarlyL8]

At 0.8bar the mods should put you around the 375whp threshold where more fuel is needed.
Can you estimate peak whp from the data you have?

[flat_6]

I haven't taken it to redline due to the fueling. Once I hit AFR of 12 I lift.
I calculated whp to be 290 but that is including rolling and wind resistance and a estimated weight.

[RarlyL8]

290whp would be very weak for those mods. At 1bar you should be at 400whp.
The GT35 family supports as much or more than a K27/29.
Redline is past peak HP most likely.
AFR of 12.0 is not lean. I don't like to go above 12.2 however spikes above that are tolerated if not chronic and the engine is not running hot. I suspect there are a lot of 930s out there running 13 and don't even know it. Smart move on your part to verify and protect your new engine.

[flat_6]

OK, so I checked the voltage at the rear pump and its low, 1.5v less than the battery or 1.0v less than the front pump.
I dont know if this would cause what I am experiencing with the AFR leaning out to fast since its the return pump. Or is this my problem??

[fredmeister]

Originally Posted by flat_6

OK, so I checked the voltage at the rear pump and its low, 1.5v less than the battery or 1.0v less than the front pump.
I dont know if this would cause what I am experiencing with the AFR leaning out to fast since its the return pump. Or is this my problem??

You have to remember that you have alot more wire length to get back to the rear pump so its gonna see more voltage drop from more resistance than the front pumps readings.

I think I saw roughly a 0.5 to 1 volt difference between the front pump and the rear on mine when I measured it as well.

Did you make sure to measure it with the car running and after a minute or 2 so the pumps could be up to running temperature and loads?

The rear pump is not a return pump its actually a second pump in series with the first one to boost pressure and flow. I think its more critical to have a good front pump since it supplies the input to the rear pump so when I changed out one of my fuel pumps to the Bosch 044 unit I installed it on the front and left the rear stock.
Not to be picky but I reread your initial post and am not sure you measured flow rates correctly. Going from memory I think the owners manual says to measure flow on the return line back to the tank with both the pumps running. Then you can also isolate each pump and take pressure readings to see which one is failing. This might help you figure out if a pump is not up to spec....good luck.

Fred

[flat_6]

I did let it run for maybe 5 min. before checking.
Thank you for the tips and clarification on the rear pump.
So, I am down to the fuel head rebuild for more flow or a new front pump.
Thoughts?