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Data log: Inector max clip==TRUE - Air/fuel ratio too lean after this point


Andre34

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Hey guys, I used a dyno with some help from a friend for the first time today. I am runnin an NA xr6 with stock injectors, pump and presure reg.

I found that at 4350rpm, Injector max clip is TRUE and from that point, no matter how ritch I made my fuel base in auF0172, my air fuel ratio was coming out too lean at that point. Does this mean I am running out of injector capacity and need to upgrade to a higher CC rating? I've also told the tune to keep the imcc valve closed at all times but that should only affect figures before 3600rpm. 

 

I've also attached the data log of the full dyno session. This screenshot is from the last run.

 

I played with cam timing also, and found that changing the exhaust overlap auF16503 didnt make any changes even with stupid numbers.

 

It was a good result over all though, made 190kw and 413nm at 5280rpm which im very happy with out of the unopened bf motor. I ran a 13.812 quater mile before the dyno tune so im excited to try another pass with the extra 2 degrees of timing.

 

I'm still very new to all this so any advice helps me heaps.

 

Cheers.

 image.thumb.png.7679ded18530326f723697ed4f231afa.png

xr6 df38lu 15-09-23 dyno.teclog

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2 hours ago, Puffwagon said:

Iirc stock na setup, injectors will be around 85% with afrs around high 12s/13:1.

What are the afrs on this particular car?

My afrs sit in the 12s up until 4500rpm, then it jumps to high 14s after 5k no matter how much fuel I add

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2 hours ago, hjtrbo said:

Injector DC 96% and PW at 26ms etc. Verify fuel pressure before splashing out on injectors. I'm not familiar with N/A. 

How would I verify fuel pressure? If it is running a good afr down low, does that mean I have fuel pressure or not necessarily?

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I looked at your log and it shows you are out of injector. It could be that you're out of pump and have kept adding fuel into the SD tables which has maxed out the injectors.

Depending on which parts you have on hand will decide what you do. You should verify the fuel pressure as it will tell you whether the pump is out. If the pump is fine you need more injector, if the pump is out you need a better pump. If the problem persists after replacing a pump that is out, you need more injector.

To verify fuel pressure you can chuck a fitting into the fuel feed, if your car is all stock then perhaps between the fuel filter and the steel pipe or even in the quick connect fitting to the fuel rail. You could run the return line into a jerry can and if it stops coming out when the car is going flat out on the dyno, it's safe to say the pump is out. There are more ways to do it, that's just a couple of ideas.

Also you should be targeting around 13:1 or possibly mid 13s for na on E85, same applies to 98, you will be losing heaps of power running it into the 11s. Where it makes the most power is where you set it. You don't keep it rich for safety, that only applies to turbo cars. To keep things safe, you set the timing where it should be to prevent knock, which isn't applicable with na and E85. Even a 1000+hp turbo car will want to run around 12.3:1 on E85.

I looked at your timing curve and it is more suited to 98 octane. With E85 you can add timing until it stops making power. You might find the opposite happens at very low rpm, it might actually prefer a bit less than stock. For this reason you don't just add a global 6 degrees, although you certainly could.

Anyhow there's something to think about, check the fuel filter too/first, as they tend to block up after a couple of days when you first switch over to E85.

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1 hour ago, Puffwagon said:

I looked at your log and it shows you are out of injector. It could be that you're out of pump and have kept adding fuel into the SD tables which has maxed out the injectors.

Depending on which parts you have on hand will decide what you do. You should verify the fuel pressure as it will tell you whether the pump is out. If the pump is fine you need more injector, if the pump is out you need a better pump. If the problem persists after replacing a pump that is out, you need more injector.

To verify fuel pressure you can chuck a fitting into the fuel feed, if your car is all stock then perhaps between the fuel filter and the steel pipe or even in the quick connect fitting to the fuel rail. You could run the return line into a jerry can and if it stops coming out when the car is going flat out on the dyno, it's safe to say the pump is out. There are more ways to do it, that's just a couple of ideas.

Also you should be targeting around 13:1 or possibly mid 13s for na on E85, same applies to 98, you will be losing heaps of power running it into the 11s. Where it makes the most power is where you set it. You don't keep it rich for safety, that only applies to turbo cars. To keep things safe, you set the timing where it should be to prevent knock, which isn't applicable with na and E85. Even a 1000+hp turbo car will want to run around 12.3:1 on E85.

I looked at your timing curve and it is more suited to 98 octane. With E85 you can add timing until it stops making power. You might find the opposite happens at very low rpm, it might actually prefer a bit less than stock. For this reason you don't just add a global 6 degrees, although you certainly could.

Anyhow there's something to think about, check the fuel filter too/first, as they tend to block up after a couple of days when you first switch over to E85.

Awesome, thanks for the write up! Very informative. From what you’ve said, i think ill go for some 600cc injectors and a 255 pump. Reason being the current stuff is as old as the car and it wouldn’t hurt doing an upgrade. Fuel filter is a good mention, I’ll be sure to remember to replace that.

 

When it comes to tuning spark on e85, do I just keep adding timing until I stop making power/start seeing knock?

 

Ok, once I get the injectors and pump in, I’ll tune to have no lower than 13afr. 
 

I’ll give the lower spark at low rpm a go. I’ve lost a bit of torque and power from keeping the imcc valve closed so it would be good to pick up that lost power again for launching.

 

 

Also, I’ve got my stoich set to 10.2. I was going to put 9.7 but I was told it’s too rich for NA. With 10.2 stoich, my idle fuel trim is +-2. Does that mean my stoich is set ok or does stoich have more play in what the engine does

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With the timing it will pick up a certain amount of power per degree. It will keep doing that until it's close to MBT then it will start to make a bit less per degree, then more timing will do nothing.

Generally you will keep adding timing until it makes no difference, then go back to where it made the most power, or 0.5 to 1 degree less. Go up in 2 degree increments as a general rule, then fine tune it at the end. On E85 it will stop making power before it starts knocking, whatever you're seeing in the log that's removing timing is probably valve train noise.

Move the fuel to where it makes the best power. You have some dyno data already, when the fuel is fixed you'll see if it makes more or less power compared to now at various rpm points.

The stoich number refers to the fuel characteristics, not the engine. Normal petrol has a stoich value of around 14.7:1, E100 has a stoich value of 9.0:1, methanol is 6.5:1 etc. You use a bit of math to work out what stoich values various blends have. Google has heaps of info about this.

As far as changing the value in the tune goes, it's just a global multiplier which will either lean out or richen everything up, from the cold start, normal driving, wot etc. If your trims are within 2% as you say, it's as good as it ever needs to be and doesn't need to be tuned further.

There is a HP academy video on YouTube regarding E85 tuning and shows how sometimes a car wants less timing down low. It's not a huge difference but it's something you would tune for if you wanted every bit of performance possible. Gonna take a bit of effort with the Falcon as you'll have to run it up, hold the car at a rpm and load cell, make a note of the torque number on the dyno, then reflash it with different timing numbers. Have a quick look at the difference but don't spend heaps of time on it unless the dyno is free lol.

On the subject of injectors, the na reg runs less pressure then a turbo reg. It would be worth seeing if a fuel pressure change gives you enough headroom with the injectors.

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8 hours ago, Puffwagon said:

With the timing it will pick up a certain amount of power per degree. It will keep doing that until it's close to MBT then it will start to make a bit less per degree, then more timing will do nothing.

Generally you will keep adding timing until it makes no difference, then go back to where it made the most power, or 0.5 to 1 degree less. Go up in 2 degree increments as a general rule, then fine tune it at the end. On E85 it will stop making power before it starts knocking, whatever you're seeing in the log that's removing timing is probably valve train noise.

Move the fuel to where it makes the best power. You have some dyno data already, when the fuel is fixed you'll see if it makes more or less power compared to now at various rpm points.

The stoich number refers to the fuel characteristics, not the engine. Normal petrol has a stoich value of around 14.7:1, E100 has a stoich value of 9.0:1, methanol is 6.5:1 etc. You use a bit of math to work out what stoich values various blends have. Google has heaps of info about this.

As far as changing the value in the tune goes, it's just a global multiplier which will either lean out or richen everything up, from the cold start, normal driving, wot etc. If your trims are within 2% as you say, it's as good as it ever needs to be and doesn't need to be tuned further.

There is a HP academy video on YouTube regarding E85 tuning and shows how sometimes a car wants less timing down low. It's not a huge difference but it's something you would tune for if you wanted every bit of performance possible. Gonna take a bit of effort with the Falcon as you'll have to run it up, hold the car at a rpm and load cell, make a note of the torque number on the dyno, then reflash it with different timing numbers. Have a quick look at the difference but don't spend heaps of time on it unless the dyno is free lol.

On the subject of injectors, the na reg runs less pressure then a turbo reg. It would be worth seeing if a fuel pressure change gives you enough headroom with the injectors.

Thanks for the info! It’s very helpful for me because I didn’t know all of these details.

 

I’ll look into the pressure reg thing because I have heard other baby builds just changing the reg. 
 

with what you said about coming closer to mbt spark, does that mean I shouldn’t touch my mbt table and just play with the borderline knock spark?

 

No free dyno for me unfortunately. I gotta pay 100 an hour. Maybe one day I’ll buy a dyno and chuck it in the garage just to make the neighbours hate me hahah

 

I’ll play with the bottom end spark while I do the top end and use the best spark it does in the time it takes to tune the top end. I’ll check out that hp academy video too.


Thanks for all the advice! 

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