S550 issues on Nitrous

[R8Bill]

A buddy of mine is having an issue running nitrous and getting knock. We has tried 3 different tuners and still has it on a 100shot, even tried 2 different nitrous kits. We even tried removing IMRC's thinking flaps could cause false knock and also lowing the timing a lot and still he sees knock when the shot comes in. Not sure if it is false knock but nevertheless the knock sensors trigger timing to be removed. I have heard of other S550's having the same knock issues on nitrous but no one says how they fixed it, that's if they did. Does anyone on here have any experience with nitrous tuning on the S550 and have experienced the same issues and what you did to fixed it?

I have a log to post but don't see the upload link to do it, wtf

[Jn2]

You need to upload the log using the "manage" attachments button when reply from advance reply. Then click upload file and upload it for it to become attached.

KR is most likely a lean spike...need to see logs to know for sure

[R8Bill]

Here is the log. The shot came in at the middle of the log and you will see knock. Timing was already low and you can see from the log the knock came in at the same time lambda was starting to go rich, which lambda was commanded to go to 0.73. I did ask him if on other pulls he made if he started the WOT enrichment sooner than when the shot came in, he said yes and still had "knock" which is why we swapped tuners a few times only for him continue to have the same knock result. I can try and get him to do another data log with and schedule shot to come in later after he goes rich, but again, he said he already tried that. Not sure what to do right now.

100Shot-01.hpl

[wayno]

like jn2 said its a lean spike it shows in the log. if the maf is dialed in 100% you need a bigger fuel pill, or speed up enrichment rate

[murfie]

Short term trims are not compensating fast enough for the initial shot. your very lean for about a second. Trims should have been double if they were fast enough. Then they are compensating about 10% the entire pull. Id say you need a bigger fuel pill to not only help with transient, but overall. Commanded is really low as it's trying to do what the trims say it should do and that is request more fuel other wise in OL your lambda actual would be much worst. From the rest of the log MAF and fuel looks ok.

[Jn2]

Your lean spike is much worse than the one my example below
15578077_1800312196895336_296169249581878903_o.jpg
My example one only lasted 1/2 a second and caused zero KR at 28* of spark advance, to correct this we went with a shorter fuel line(1/3 the length of the nitrous line). This allowed the fuel to make it to the plate around the same time as the nitrous. Remember the nitrous is at 900+psi and your fuel is only 55psi, the nitrous will will the race every single time, this causes a lean spike which the ECM cannot react too fast enough.

[R8Bill]

The fuel line is already 1/3 the length of the nitrous line. He is already using a larger jet for the fuel (31 for fuel and 52 for the nitrous for the 100shot). The enrichment rate was set to 0.500 lambda/sec but can be increased to 1.00. Should the tuner try to adjust the acceleration transit time constant to bring in fuel faster on acceleration, and any suggested values to use if this is to be done? Also, per the coyote handbook, the suggested WOT lambda for a 100 shot it 0.73, is this correct?

[murfie]

What MAF size do you have?

Your fuel trims compared to your MAF period don't look that bad, but compared to your EQ commanded/actual error its pretty bad. I suspect a high enrichment rate for this difference.

The enrichment rate for stock 5.0 is .050. For the 2017 GT its .025. Thats a high horse power boosted V6. I think raising this for boosted applications to prevent fuel delays is incorrect. the 2.7 and 3.5 v6 f150's eco boost has it as .025 as well while the 2.3l mustangs are at .100. 3.7L NA v6 mustangs and 3.5L NA SHO's have it at .250. Seems to me the lower torque the engine makes for its size the higher this value is. In a nitrous application you will be making lots of torque and following the trend in the stock calibrations I would say you need to lower this enrichment rate to compensate for fuel requirements.

[HPF]

yah guys 2 of my customers fits nitrous on their s550 GT's non of them work well I did every thing
call me crazy but i think all these problem cuz +15 new manifold we will install boss/m and will see what happen

[LavaRed50]

What fuel? Sounds like it's dropping fuel pressure on the initial hit, then struggling to catch back up. I would put a mechanical gauge on it. When you put the larger fuel jet in, it could have made the problem worse.

[R8Bill]

E85 with 47lb injectors and BAP

[mstang_man]

rule of thumb is to pull 2deg of timing (min) for every 50 shot of NOS and adding fuel just before the NOS kicks in.you could also raise fuel pressure to help in transition, just as everyone mentioned above.

[LavaRed50]

i would put a mechanical gauge on it. Make sure the pump booster is upping voltage before the fuel solenoid opens.