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Discussion Starter #1
Ok guys need some help here

Long story short, I built a front mount turbo system for my NA 350ci SBC. 1.75" headers, 2.5" cross over, 3" downpipe thats 5 feet long. TC76 T-netics turbo, 0.96 (F1) AR. It has a stealth ram intake on it, switched from 24# to 80# injectors

I never got it to the track with anything but street tires when it was NA so my ET's were terrible since its a clutch car, but I was seeing 106.5 MPH in the 1/4. I have it on 3psi and tuned on the 80# injectors, it's only hitting 94.5MPH in the 1/4, timing is 29 degrees under boost, i have zero knock retard unless it's very heat soaked, my afr is 12.7 @ 3psi, it spools at 2400rpm, I'm waiting on my boost controller to come in but for right now I'm trying to make sense of my loss of over 10mph :confused:

My thinking is that the exhaust is now so restrictive (50mm wastegate tho...) that the meager 3psi boost pressure is not enough to make up for the power loss. But then you read about a 5psi kit adding a decent amount of power to a car so that leads me to think my tune is FUBAR somehow. This is my first turbo car and right now it's making me wish I had built a nitrous car :-damnit

I have an attached plot (.docx) of my pass from last night, and the CSV (excel) file form tunerpro if that helps anyone.

EDIT: ok I cant attach it (or im just not seeing the button) but I can send you the files if anyone wants to see them)
 

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Id verify that your timing is indeed what you think it is. I had a locked HEI distributor that was set at 25*. By 4k rpm it was retarded to 12*. I read the HEI's have a tendency to retard timing with RPM and this was a stock shortblock so the timing set was probably well worn. Just something to think about.
 

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x2 double check the basics, verify no hotside leaks, as well as timing and O2 readings are where you think they are.
 

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Discussion Starter #4
OK I checked everything out except AFR readings, no leaks, my true timing matched my logs exactly. My charge pipes are 2.5" for abour 18", then a 3" in, 3" out 1000hp rated intercooler, and 3" to the TB if that matters

How should I veryify AFR readings? It seems to be accurate, rich readings smell rich, lean pops, 14.7ish runs nice and smells correct, fuel table changes up/down show change in the correct direction on the WBO2, but I know thats not at all an accurate way to determine if its correct
 

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What timing did you run NA?

I would guess more than 28 degrees.

Set the timing back up to something like 36 and you will pick up power.

3PSI does not need any timing pulled out. You should be good to at least 5-7PSI without taking out any timing.

Reduced timing, nearly the same intake pressure, higher intake air temperature and the exhaust restriction of a turbo would account for your MPH reduction.
 

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What timing did you run NA?

3PSI does not need any timing pulled out. You should be good to at least 5-7PSI without taking out any timing.

Reduced timing, nearly the same intake pressure, higher intake air temperature and the exhaust restriction of a turbo would account for your MPH reduction.
i agree with this guy, but dont take that to mean i know what im talking about :rolleyes:
 

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Discussion Starter #7 (Edited)
I believe I had 6 degrees of mechanical advance, and 33 degrees added by the computer on top of that when it was NA

I'm currently seeing zero knock anywhere, as in not even once cell in the 7000 cell data log, I'm not sure if that's becasue my tune is so conservative or I have a sensor/computer issue
 

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Discussion Starter #9
I have it set to 33 in the computer which results in 29 true timing, I though it was the same as NA in but it's anout 8 degrees retarded, NA timing was really 38~39. I'm trying to sort out why the timing is 4 degrees less with the timing light than it's set for in my timing table, but I'm gonna bump it up in the table to 37 and maybe 40, so 33 and 3 and see how that goes
 

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I think we should ask the guy what fuel he is running before we tell him to leave full timing in it till 6psi. On pump gas I dunno if I'd do that. 2-3psi yes, just me though.

I would give it some more fuel also, 12.7 in boost is fairly lean again it depends on fuel. Try 11.7-11.9 first and if it picks up put it at 11.5-11.7 and leave it.
 

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Discussion Starter #11
93 right now and low boost (<10psi), will be going e85 once I get all the bugs out of the system and go for more power


I'm still trying to figure out why my timing is really 4 degrees less than what it is set to in my timing tables...
 
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