pwrtrip75

iTrader: (8)

72 Nova - 4 link chassis. 5.3L stock bottom/cam, 8.6:1 comp, ported 6L heads, edlbrock Vic Jr intake w/ custom elbow, GT-45 turbo 15# boost, TH350/3800 stall, 3.50 gears in rear, weight around 3400 Tuned w/ HP tuners 2-bar SD w/ wideband by me.

IAT runs around 120, A/F is 11.2, timing logs at 12*,

I can foot brake it on the line and spool it up and it launches hard, It hits 15psi almost instantly, but it just seems kinda doggy accelerating, not taching up fast. Doing some racing on the street with some freinds just to see how it runs I would say it would run a low 12 the way it is now doesnt seem to MPH like It should. It has pulled harder before just making small tuning runs. But now it sucks I think. Fuel is not cutting off, I have plenty of that.

Anyone have any suggestions on where I should look, tuning wise? And What I should expect out of this setup? Hopefully I provided enough info.

67Firebird455

iTrader: (27)

I would imagine, for max power, you could bump the AF up some, and are you getting KR? Wondering why you're only running 12* timing, that could kill power pretty quick.

pwrtrip75

iTrader: (8)

My base timing is 15* it was pulling some cause of the AIT hitting 120, I changed it and i'll have to see how it is. I am getting like 4* of KR also. The car is very ridgid, solid engine mounts, solid chassis, So I wonder If that is setting off KR. And if I should desensitise the knock sensors? Is that safe? what to set them to?
Im going to make some passes now and check it out again.

Frost

iTrader: (45)

how bad does it push through the converter? What are your tranny temps looking like? How do you feel about your converter?

pwrtrip75

iTrader: (8)

TCI super street fighter w/ anti-ballooning plate. Got it from a friend whos car ran good with it. Tranny temps are unknown. But the engine that was in it before was a procharged 427, and prior to that a 377 w/ a 4800 coan converter, tranny has been excellent.

pwrtrip75

iTrader: (8)

just made a log here is what the chart says:

RPM- 5605
speed - 4 (not hooked up)
INJ DUTY (%) 143

MAF- n/a
MAP (kpa) - 205.6
WB 02 (afr) n/a

KR (*) 3.6
Advance - 8.0
TPS- 96%

INJ B1 (msec) 31.2
02 B1S1 (mv) 881
INJ B2 30.1
02 B2S1 755

LTFT B1 5.5
STFT B1 0.0
LTFT B2 1.6
STFT B2 0.0

A/f fluctuates between 11.2-11.4 under boost. they are 42Lbs injectors.
My belt also flys off after every pass.
Any clue why the KR? and why my timing is only at 8*? in the high table its set to 15*. When does it switch over to the low table?

Frost

iTrader: (45)

Well it doesn't seem to go with one timing table or the other, but rather an interpolation of the two... and when you factor in the KR and the possibility of pulling spark for IATs, well... Also, while we know that the WB is the real indicator, your stock O2s are reading quite lean.

Overall it looks like there is just time left to be spent tuning.... I wouldn't keep any level of KR.

Beaflag VonRathburg

iTrader: (176)

I know very little about tuning, but it looks to me like you need larger injectors. If your inector duty is 143% @ 5605, the higher you rev it the more you're pushing those injectors to the limit. Especially noticing the 11.2 - 11.4 afr, that seems a little lean to me for your application. I'm not saying I'm right, because I know very little at all about tuning and data logging, that just stuck out very clearly to me.

Beaflag VonRathburg

iTrader: (176)

Another question, at what RPM are you shifting at? If you're having problems as it gains RPMs it really seems to me like the injectors are being over worked and the increasing IATs are just causing it to pull timing.

gametech

iTrader: (1)

I would hate to guess how lean the motor is going with the injectors maxing out so early, but the KR pulling your timing from 15* to 8* would be enough to kill probably 50-75 HP or more. Of course if you're throwing belts, the injectors might be maxing out because of the voltage going low to the fuel pump when the alternator quits turning.

DarkblueTA

2 words.......FUEL SYSTEM. You're injectors are way over worked. You should never go higher then 80% but you can get away with less then 90%. You're going to have to add a pump(maybe 2?) and probably bigger injectors. If you reach the 600rwhp area, you'll want to look into fuel rails to or #7 will go bye-bye on you.

Get your fuel system in line and then worry about the knock retard and any other issues.

BTW, your 'advance', unless you put the '-' in front of the 8, wouldn't that be negative 8*???

hellbents10

iTrader: (10)

My guess would be that you are seeing a lot of false kr. Put some race fuel in it to determine weather or not you are seeing false kr or if its real. Then go from there. Your 11.2:1 AFR is pretty close to ideal for a street tune up.

pwrtrip75

iTrader: (8)

The fuel system is an aeromotive A1000 w/ bypass regulator . 3/4 tubing to the pump and 5/8 tubing from the pump to regulator and -8 AN to each of the edelbrock rails. I dont have a prob w/ pressure dropping or the pump starving.

Timing is 8* advanced, I did put the (-) in there sorry.

IAT's are not pulling timing, I have it set to not pull any till it hits 131* Max IAT hit 127* so that is ok.

Ive read on here people making just over 600hp with a 346 using 42# injectors. this is a 323 and i figured I could get by with them.

I shifted at around 6000rpms, it just doesnt seem to pull anymore.

Think its just not getting enough fuel?

Frost

iTrader: (45)

If pressure is solid you are definitely out of injector. I've read of a few people around 600RW on 42s also... but seems like they are mostly 6-speed guys. Buy some 60's... the 60's are actually rated at about 40psi, so they will seem to be a good but bigger at near 60 psi. I didn't mention injectors in my first post cuz I thought it stuck out like a sore thumb.

I don't know how many miles/passes are on that converter, but I used to run a loose 10 inch that needed tightening up after the first whole season I ran it... I was losing alot through it. At first it was just seeing MPH drop, but soon it was clear that it just never got close to 1:1...

pwrtrip75

iTrader: (8)

OK, thanks everyone. I'll just turn the boost down to half, around 7 and see how it is untill i get some money for injectors.