When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Idk if you guys can open this CSV file (open in excel) but I compiled the most recent datalog of a few pulls I had of the 78/75 with a 4" catback I just installed. So I did some runs through the full exhaust (3" DP about 7ft or so into a 4" catback for a 3rd gen firebird). None of these are the 0mph WOT that I did and I can't seem to find those logs if I even took them. But one of them shows boost starting around 2800.
So I found some time to swap out the billet gen 1 78/75 and swapped in the new next gen billet 70/70. I modified the hot side to accept a 1/8" NPT bung to log pre turbo back pressure with the new smaller turbo.
Now I'm working on my tune so I wanted to rescale the base fuel table, AFR table and spark table to a more granular range that I operate in. My only concern is that I topped my fuel/spark to 210kpa which I normally average about mid 190 kpa during normal driving with my EBC commanding 30% over spring rate. It doesn't give me much margin for error I guess but originally my scaling went from 0 - 285kpa and it now goes from 20-210kpa. I normally idle around 50kpa so I would change the lower to 30-35kpa and increase the top end to 225-230 ish if need be. Anyways I wanted to get your thoughts on the updated tables. I pulled my fuel and spark data from the running tune and swapped and populated the new scale to get the fuel and spark close to what I had before. I changed back the learn fuel correction back to 50%+/- so I have the safety for the first couple of drives. Then I will transfer learned data and get me back to +/- 2% as it was before. I normally push 13psi on the street but I have been up to 15psi at 50% duty cycle on my EBC (setting 2) but I never put it on that one.
Anyways let me know your thoughts and if you think the timing should come down more. I wont be able to drive the car for at least 2 more months though. Just trying to get my ducks in a row for spring!
Took the car out on Friday for its first drive with the new 70/70 turbo, no change to the tune. Here is a pic from the fuel learn table and Fueling was from the billet gen 1 78/75 OG. Looks like besides around idle it’s pulling fuel which suggests lower HP output. Except at the top end which I hit 13psi on the EBC which did the same with the 78/75. Car didn’t seem much slower but also felt like it hit a wall at 5700-6k the one time I spun up that high. At the top end the fueling was less than 1% difference. Mostly less than a 5% difference than the 78/75. I did hear the turbo much easier through the full exhaust than I did with the 78/75 and it seemed to get rowdy quicker. I didn’t get any logs but that’s next… I just wanted to make sure it ran fine and didn’t blow up as it was the first time it’s been out in 6months. Logs are up next drive and I’ve also loaded the new tune with the 210kpa max MAP as well as the adjusted fueling and timing tables.
I find that for street cars, you don't need more than one row per 2 pounds of boost. So if you plan to go to 15psi, I see no reason to have more than 10 rows in the boosted area and devote the rest to NA.
Took the car out and decided to get a log with a 100psi transducer in the turbo merge/elbow to see in real time with boost how it's running. I do want to say I only spun this to 5500 again as thats 120+mph to get the log but the boost comes in quick and hard with this new turbo. I will try to update with the log so you can all see in real time. I swapped the oil pressure sensor plug on the turbo transducer as this is just a temporary thing and I wouldn't need to wire up new inputs and configure. So when I upload the log the OIL PSI is the turbo back pressure which the tap is right before the turbo inlet after the merge and WG. I do also want to add that I did these early this AM on my way into work so this is through a FULL exhaust which has a 3" high flow 200 cell CAT installed on the inlet into a 4" catback so I suspect my next log will be with the cutout open to see the differences.
Here are the BP results which put me slightly below 2.5:1 ( I want to see what its like with the cutout open)
BOOST / BP
1 / 6 = 6:1
3 / 9 = 3:1
4.3 / 12 = 2.79:1
5.9 / 14 = 2.37:1
7.2 / 16 = 2.22:1
7.78 / 18 = 2.31:1
8.65 / 21 = 2.42:1
9.81 / 21 @ 4,842rpm = 2.14:1
9.81 / 23 @ 5,000rpm = 2.34:1
9.81 / 24 @ 5,246rpm = 2.44:1
9.52 / 25psi @ 5,508rpm = 2.62:1
Took the car out and decided to get a log with a 100psi transducer in the turbo merge/elbow to see in real time with boost how it's running. I do want to say I only spun this to 5500 again as thats 120+mph to get the log but the boost comes in quick and hard with this new turbo. I will try to update with the log so you can all see in real time. I swapped the oil pressure sensor plug on the turbo transducer as this is just a temporary thing and I wouldn't need to wire up new inputs and configure. So when I upload the log the OIL PSI is the turbo back pressure which the tap is right before the turbo inlet after the merge and WG. I do also want to add that I did these early this AM on my way into work so this is through a FULL exhaust which has a 3" high flow 200 cell CAT installed on the inlet into a 4" catback so I suspect my next log will be with the cutout open to see the differences.
Here are the BP results which put me slightly below 2.5:1 ( I want to see what its like with the cutout open)
BOOST / BP
1 / 6 = 6:1
3 / 9 = 3:1
4.3 / 12 = 2.79:1
5.9 / 14 = 2.37:1
7.2 / 16 = 2.22:1
7.78 / 18 = 2.31:1
8.65 / 21 = 2.42:1
9.81 / 21 @ 4,842rpm = 2.14:1
9.81 / 23 @ 5,000rpm = 2.34:1
9.81 / 24 @ 5,246rpm = 2.44:1
9.52 / 25psi @ 5,508rpm = 2.62:1
I like what you're doing and the detailed posts. Thanks for that!
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
