Self Tuning With SCT Pro Racer

03cobra#2

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I would do the slopes also if you have a good MAF curve.
I ended up increasing base pressure to 50 psi. Gave the car a quick start up and idle for 1 min. No datalog but it started up fine and idled OK with AF being around 1 lambda at idle. I just finished up ramping up the injector high slope, low slope, breakpoint, and compensation for battery voltage by 10% to match the 10% increase in base pressure. I also changed desired pressure drop across injectors from 39 to 46 psi per Don Lasota's book. Flashed to the car and ready for a startup in the morning.

Tomorrow I'll take the car for a spin and post results.

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03cobra#2

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Did some driving / datalogging and the increase in fuel pressure definitely brought injector duty cycle down. Tonight I'll add the 2lb lower and increase base pressure to 55psi. That should give me some headroom with my combo and I will works towards dialing in this as my final combo.
 

c6zhombre

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Did some driving / datalogging and the increase in fuel pressure definitely brought injector duty cycle down. Tonight I'll add the 2lb lower and increase base pressure to 55psi. That should give me some headroom with my combo and I will works towards dialing in this as my final combo.

Nice! Sounds like you are very close now.....excellent job progressing thru this project.
 

03cobra#2

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Nice! Sounds like you are very close now.....excellent job progressing thru this project.
Thanks! After I get af dialed in I need to populate the failed maf table. I have a part throttle tip in stumble. I really hope enabling the failed maf table fixes it.

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01yellercobra

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Thanks! After I get af dialed in I need to populate the failed maf table. I have a part throttle tip in stumble. I really hope enabling the failed maf table fixes it.

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I've found that makes a decent difference in driveability. Using the histogram makes it a snap to do as well.
 

03cobra#2

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Small update: put on the 2lb lower to go along with the 3.5 upper. Increases base pressure to 55psi. Went out on the highway and did a quick wot pull in 4th up to about 4500rpm. I was shocked to see the boost gauge showed about 27-28 lbs at 4500. Injector duty cycle was at 76% at 4500 rpm
Will I have enough fuel to get me to 6500 rpm or so? Do I need to put the stock lower back on and back off on the boost? Car pulls hard and feels good. Plugs look OK and fuel pressure held steady around 55psi delta. I need some input here. Here is a screen shot.
d04a05d3187f9470fc04755a5f65c9b0.png


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Wings65288

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Yeah I woulda been 30 pounds lol. I think I'll start with my 3.75". Should put me at at 27ish hopefully
 

03cobra#2

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Small update:
I would say I have the tune is 3/4 of the way done. I have my base fuel pressure set up at 55psi and put the stock diameter lower pulley back on. Looks like it holds around 24lbs of boost. I did a wot pull up to about 5500rpm and the numbers look pretty good. Looks like I'll have plenty of injector at 55psi base pressure. The maf curve needs some fine tuning, and I'm hoping I won't hit the maf limit and have to rescale the curve again.

Couple small things that need attention:

Idle hunts a bit. When parked or at a light the idle is sometimes steady, sometimes surges just a bit every 5-7 seconds or so. I think it just needs a bit of tweaking still.

I have a rich tip in and lean tip out. Not terrible but it's there and can cause the car to buck in first gear from time to time. When cruising you can feel it. I have transitional fueling turned off right now until I get my failed maf table set up. I have started to use the histogram feature in SCT livelink to fill in the table. Hopefully this solves it. If not I guess I can play with manifold volume or other parameters.

Lastly is my short term fuel trims. At idle and steady cruising they are off a bit. Like 7-10%. Sometimes more sometimes less. Reason I'm not too concerned is that under partial load / partial acceleration the trims even out and are much closer like 2-4% diff.

Lastly I still have my dyno appt on Wednesday. I'm not sure if the tuner will want to work off the tune I have created or if he will want to start from scratch. Hopefully if everything checks out we can take it to 6500rpm or so and dial in the timing. Can't wait to see what it makes.

All in all I'm really happy with the way my car runs so far and have learned a ton by tuning myself... I mean a ton. Before I'm like wtf is a maf curve or injector slope lol. If I was to continue on my own I could probably have it dialed in myself eventually but I feel more comfortable with a pro to do the final stuff and make sure it's making good safe power.





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03cobra#2

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Trying to set base fuel pressure. I have a mechanical gauge on the fuel rail. When I turn the key on and the pumps fire up (engine not running) I set the gauge on the rail to 55 psi. When I go out driving and datalog delta fuel pressure hoovers around 58spi in SCT livelink. When I look at the mechanical gauge on the rail while the engine is running the needle is bouncing too much to get a reading. Is using my datalog through sct live wire an accurate way to set base fuel pressure? Im guessing with the engine off and at 12 volts the pumps are not putting out as much pressure vs the engine running and the pumps getting 13.8-14 volts. Thoughts?

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JAJ

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My thought is that regardless of the actual pressure, it's what the ECU thinks the pressure is that matters, because that's what it responds to in setting the injector duty cycle. The value in the PID is what matters.
 
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03cobra#2

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My thought is that regardless of the actual pressure, it's what the ECU thinks the pressure is that matters, because that's what it responds to in setting the injector duty cycle. The value in the PID is what matters.
I'm going to fire up the car and log the frps and adjust the regulator down to see if the reading in SCT live wire changes. I'm thinking that's probably the most accurate way to set the fuel pressure.

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03cobra#2

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My thought is that regardless of the actual pressure, it's what the ECU thinks the pressure is that matters, because that's what it responds to in setting the injector duty cycle. The value in the PID is what matters.
When I dataloged the frps is was saying 57ish psi at idle. Turned the regulator down until it was showing me a average of 55.2 to 55.4. I think I'm dialed in now. Looks like that is the best way to set it. Using a mechanical gauge gets you in the ballpark but obviously it was off a bit.

Keeping the frps intact has given me valuable tuning info... Definetly the right move to keep it with my return system.

That small adjustment helped the idle and fuel trims at idle. Idle pretty much stopped surging and is pretty much rock steady. I'm going to pull the plugs tonight to do a quick inspection and off to the tuner Wed morning.

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03cobra#2

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I was gonna wait until Friday to post when I picked up the car. Ended up making 711whp @ 25lbs of boost. I don't have any other details yet. It was hot out today (91) and he said Iat2's were hitting 150's. So I guess I'll invest in some cooling mods and hit the rollers again in the fall.

He did say he got a good tune, no problems, and drivability should be good.

When I get the car back I'll have a dyno sheet, and I copy of the tune I can modify if I wish. I'll probably work off it to create a 93 tune.

All on all not bad / not great but I'm satisfied. I really think that when get the Iat2's under control and a bit cooler weather I'll have some nice gains.

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