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Honestly there is a lot to look at when diagnosing.
I would:
-After a pull/track/street, check the log to see what boost it made at the leave and how long it took to make to make target boost. If boost is consistently below commanded you might need more dome pressure ie. it's consistently 2 lbs lower through the entire run. You might not be making commanded boost on the leave so the car is slower all over. I myself am looking at this today, I might need to have a buddy help me build a boost builder table, I'll post later.
-Check for boost leak.
-Do you have fuel and boost cuts programmed? Hitting one of those?
-How are the fuel trims?
-Shift points right?
Honestly there is a lot to look at when diagnosing.
I would:
-After a pull/track/street, check the log to see what boost it made at the leave and how long it took to make to make target boost. If boost is consistently below commanded you might need more dome pressure ie. it's consistently 2 lbs lower through the entire run. You might not be making commanded boost on the leave so the car is slower all over. I myself am looking at this today, I might need to have a buddy help me build a boost builder table, I'll post later.
-Check for boost leak.
-Do you have fuel and boost cuts programmed? Hitting one of those?
-How are the fuel trims?
-Shift points right?
Yeah and I have a lot to learn about this car. A shop built it but I'm taking it from here.
How are you controlling boost via the Holley? With no CO2 I assume duty cycle? Boost by gear, rpm, time, etc?
Although I don't think it is your issue, there are a lot of things in the Holley that can help with spooling and also tell you what is going on via the data log.
I'm reading a book on cams right now by Billy Godbold from Comp Cams. This is two of their cams. The milder one is meant for small turbines/full exhaust street turbos with higher backpressure to boost pressure. Its got -6 overlap. The bigger cam is for bumper exits and has +4 overlap. My cam is on the safe side but I think it was a pretty good choice. I also think I was on the right track with thinking up to +5 overlap (which is still pretty mild compared to a hairy NA cam) is acceptable for typical street/strip turbo setups. Godbold those would work good up to 1.5-1 backpressure/boost ratio. I still think a bit lower duration and tighter lsa within reason would be the hot ticket for response if you aren't trying for 7k+rpm. Like I said, for now I'll stick with the cam I have but if anybody finds this maybe they'll try a Truck Norris or similar with a turbo and let us know how it goes.
Yeah once you have figured out if everything is working. You shared sa your combo:
LJMS stage 1, 222/227 and 113lsa +3
.030" over 5.3, flat top pistons (so might be around 10:1)
CNC'd ls6 heads
LS6 intake (I've seen one combo peak around 6200 on the dyno)
Huronspeed, the basic cast $400 VS 7875 turbo with .96ar turbine housing.
4l80E no transbrake
3.25 rear end gears
3000rpm stall converter (this is a tight converter)
25" tires
Terminator X
It revved to 6200rpm and made 550whp on 13psi. Bottom end is lacking imho, can barely get it to spin tires (I assume you did not lock the converter?)
Fuel?
How much timing were you running at 13psi?
Its been a heck of a week, busy at work and had to switch storage units. I'll get my info from the Terminator X.
All that is correct, except now my exhaust was hanging low and bottomed out. That sped up my timeline, I bought the turbo I really wanted which is a VS G42 80/98 compressor wheel, 83/75 9 blade turbine wheel (1.25ar) journal bearing. It should be about the same as a VS Gen 3 7875 except its vbanded together. Along with that I am having a 4" bumper exit exhaust installed sooner or later.
Here's some screenshots. The boost vs rpm is probably my biggest problem. Should be way more aggressive. I've been told the fuel is also too rich going 11-1 as soon as it hits 0psi. The tire height and rear gear is set wrong too. Probably not helping. Should be ~25" and 3.25.
Here's some screenshots. The boost vs rpm is probably my biggest problem. Should be way more aggressive. I've been told the fuel is also too rich going 11-1 as soon as it hits 0psi. The tire height and rear gear is set wrong too. Probably not helping. Should be ~25" and 3.25.
How is your dome pressure set up?? Are you using CO2 or the compressor?? I'd turn your TPS boost modulation on. Try bringing your dome pressure rpm down to start at like 2500 and go up from there. Just play around with the settings and log some pulls to see how things react.
How is your dome pressure set up?? Are you using CO2 or the compressor?? I'd turn your TPS boost modulation on. Try bringing your dome pressure rpm down to start at like 2500 and go up from there. Just play around with the settings and log some pulls to see how things react.
No CO2.
Maybe the shop that built it was kind of baiting the hook for future dyno sessions and "upgrades". Or just wanted to keep me from Mustanging the crowd leaving Cars and Coffee. Lol
Maybe the shop that built it was kind of baiting the hook for future dyno sessions and "upgrades". Or just wanted to keep me from Mustanging the crowd leaving Cars and Coffee. Lol
Could be yea or they just played things super safe. Either way I'd just start playing with things while taking logs to see how everything goes. I found the dome pressure PID settings took me some time to get the boost curve smooth without huge spikes
Here's some screenshots. The boost vs rpm is probably my biggest problem. Should be way more aggressive. I've been told the fuel is also too rich going 11-1 as soon as it hits 0psi. The tire height and rear gear is set wrong too. Probably not helping. Should be ~25" and 3.25.
Very minimal gains to be had with a lower duration cam. You need RPM. Its pretty simple physics. If you don’t have RPM you won’t build boost w a reasonably sized turbo. Either have to run and undersized turbo and 2:1+ back pressure +. Or get a converter that allows an ACTUAL 3500+ stall speed.
Tune changes can help. But only so much can be done without a proper amount of RPM. If on E85, you can run NA peak TQ timing and AFR up to around 5psi. your map is about 5* shy of optimal timing at 100kpa and prior a well. That can be as much as 30-40hp. More power = more flow, more flow = faster spool.
Most of the factory stuff peaks out at 28-29*. If you are on e85, I’d def up timing in the 81kpa thru 134kpa (id actually make that 126kpa field 134kpa). I’d start at 26* in all the fields from 113kpa to 134kpa. And 29* from 81 to 100kpa. Drop a new plug in the hottest cylinder and go do a pass and read it. Slowly bump timing up to a peak of 28* through the 113-134kpa range as long as plugs look good. Should wake up a bit
With E85 I also target 12.5AFR up to 5psi or so. I’d target 10.8 at anything over 20lbs and 11.8 at 6lbs and interpolate between the group for a progressively richer mixture with boost increase.
Also, isn’t there a makeshift “trans brake” like option for the 4l80e where it puts you in 3rd gear with a button? Then when released, it drops it back in 1st? (google “sloppy trans brake) That will allow you to load it a little more with the foot brake and build more boost.
even with all that it may not build boost like you are wanting with your converter. IF you can’t mat the gas from a stop in 1st and see 3000+rpm flash stall speed… its too tight.
Last edited by Forcefed86; Oct 8, 2024 at 09:34 AM.
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