Running lean under boost
 

Would like to know if anyone else with a boosted Z has experienced the car running lean under boost, and what their issue was and how they fixed it please?

Only just had my TT build finished up and currently being remote tuned by Seb, but ran into this problem of the car going lean when I tried the WOT pulls.

AAM Competition RHD TT Kit
ID1050x
Walbro 460
CJM S1.E System
Fuel Pump Relay Kit
Running e85


Below is part of am Ecutek log when I tried the pull:
https://s6.postimg.cc/9ylgw6lqp/rece...0888210554.png

My workshop has looked for possible fuel leaks and pump voltage and that seems to be all ok. So they assumed my Aero340 pump before was too small, so they changed the Aero340 to a Walbro 460 and that instantly made the car feel better and more responsive but the lean issue was still there although not as bad as before the new pump.

Seb has tried to force more fuel in the tune which also helped but as you can see from the graph it still progressivly gets more lean under the load as it increases.

My fuel pressure on idle is @42 psi, I think that is with the vaccum/boost hose connected, not sure if it should be higher?

Atm I am waiting till Monday to get it onto a dyno so we can check the fuel pressure under load, as suggested by Seb.

Has anyone had this problem before please share you experience with me, thank you!

Looks like you don't have enough injector. Most folks get at least IDA 1300cc injectors for
for E85. I am using IDA1700cc for my build. Go through the trouble shooting process and see what happening with the fuel pressure.

Did you get the fuel pressure gauge with the CJ Motorsports fuel system? It shouldn't take but a pull or two on the dyno if you do. Then you will know.

If you have the return kit you should be able to increase fuel pressure under boost ... if it was tuned correctly and started doing this you may have a vacuum leak on the fuel pressure regulator ... my fuel pressure at idle is 52 but I also have different injectors

Ideal should be between 50-55, might have a small leak in your fuel
Lines.

My Ecutek log shows my injector duty cycle only reaches 50-60% under load, does that mean I still have a bit of room left in my injectors?

Also interestingly, on another log I took the other night of a semi-pull in 2nd gear, 'Injectory Duty Bank 1' dropped from 50 to almost 0 momentarily. But I think that may be another issue altogether that Seb has said may be a failsafe map dropping the throttle, which he has adjusted and sent another tune through, I have not tested that new tune but will do tonight. See below:
https://s6.postimg.cc/ldhy0zdkh/rece...1787740464.png

Yes I did the mini pressure gauge. That is why I am taking it for a run on the dyno on Monday to see if it is holding pressure under load.


Yes I have the return kit. Well I will check the pressure under boost on the dyno, see if it is increasing. It started doing this possibly the moment I got the build done and tried my first WOT pull.

The workshop it was at, said they done a leak test accross the fuel system, tensioned all lines and could not find any faults?

I would verify the vacuum source to the regulator and make sure there isn’t any leaks ...you should see around 52 at idle and for every pound of boost it should increase one psi per pound ... on average.. depending on injector size a tune
May be different with e85 tho ... I’m speaking from 93 oct settings .... but either way idle should be 52 ish and it should increase with boost

Just got Sebs latest revision and my car basically resulted in the same logs where under WOT my AFR will start rich but then increase leaner under the load. But it did get rid of that sudden injector duty drop from bank 1.

https://s6.postimg.cc/727mn47gh/Inj03.png

You'll find it. Something wonky is going on.

Seb has told me 42psi idle is fine with the vacuum connected. He said if I remove the hose it should increase to ~50psi.

I am wondering if I can adjust the pressure by increasing it by an increment of 5psi and see if that will help stop the leaning out issue?


Any ideas?

Seb is the man, follow his lead.

Will do!

Is voltage suppose to drop in spikes?

Can anyone check out this graph and let me know if it is normal?

https://s6.postimg.cc/prwecnxgx/20180723_164523.png

Wow, it looks like you may have a bad cell in your battery. The voltage shouldn't drop like that. Bad batteries can cause some strange things.

Could that be the reason I am going lean under boost? Maybe battery is not supplying pump with enough voltage?

It is possible that it is not supplying enough current. Have the battery loaded tested. Looked for loose connections and a bad ground.

It is possible that the pump is getting a voltage drop causing lean condition ...but it would also show a dropping fuel pressure ..have you monitored the fuel pressure during the run ...if pressure rises and is consistent during boost I would look into tuning or injectors issues ....If you see very little increase in fuel pressure or a drop during boost I would look to mechanical issues ...voltage ..vacuum line ..etc

I have just sent my car back to the workshop yesterday...again.

This time they will put it on the dyno and monitor what the pressure does under load. So will know soon if I have pressure drops.

Found the issue, it was a faulty FPR.

They replaced it and told me it is now holding steady 11.1-11.5 AFR under WOT.

:)

That was an easy fix, diagnosing it not so much.:tup:

That is why I am a huge fan of the mityvac mv5445. It’s the only fuel tester that gives you a 100% outlook of what the fuel system is doing without having to leave your stall. Sadly not many have one and then people chase their tails on what is going on.

Dude, why are you using Australian products?
Lol

Strange, after my boost controller install I am getting a lean spike on the graph of AFR Bank 1 midway through a WOT.

Anyone have this issue before?