Project Bird

2000 trans am ls1
ls6 intake 243 heads 228r cam fast 36 lb injectors stock fuel pump stock 4l60e custom built cameron 3200 stall
386/366 on dynojet ~3700 lb rw

made 332/341 on same dyno with just bolt ons a year before cam swap (headers, exhaust, ls1 intake) car would trap 85 mph and go 8.10s 1/8 mi, 12.70s 105 mph 1/4 mi on this setup with converter and bolt ons (I thought this was a low trap speed too but seemed ok for the setup)


cam swap last october, did not go to track until beginning of december, few spinning passes with 86-88 mph traps, dead hooking pass and best et to date went 7.61 to the eighth at 86 mph, 1.66 60 ft back in december

this past saturday, march 25, carolina dragway.. 1st pass was low about half a quart on atf and flared 1-2 and 2-3 shifts. 7.95 to the eighth at 85 mph, 1.69 60 ft, add atf and 4 hours later 1.66 60' 7.83 to the 1/8 at 86 mph.. 103 mph out the back.

I do not have a wideband, or a fuel pressure gauge, my first thoughts are the stock fuel pump is too weak and is dropping fuel pressure and leaning it out WOT.. I plan to test my theory tomorrow and try to tape a harbor freight gauge to the windshield.. Does this sound very likely? I'm assuming it's been like that the whole time and was even struggling on my tuner's dyno since i don't think he logs fuel pressure, and he probably adjusted for it in the tune to a good afr? which makes me think i'll need to get it back on the dyno and retuned after i put a new pump in it, if that's what my problem is.

Any other possible ideas, thoughts? Just put a new pump in it since that's 100% my issue?

thanks

thunderstruck507

iTrader: (18)

What was the density altitude at the track?

trap seems pretty low for 243 heads and 228r cam, in average DA I wouldn't think 110mph would be an issue

check your fuel pressure first but you would probably be able to feel it nosing over I think

could be a tune issue, could be a cam/lifter problem, cam could be a tooth off...really hard to tell without logs or more data

if the air/fuel ratio is good WOT it's a moot point whether the pump is low or not...proper fuel is proper fuel since there isn't anything mechanically limiting airflow, it either has enough fuel or it doesn't

Project Bird

DA was 1739

zzracer

iTrader: (33)

I think the mph seems low for sure now and before. Just curious what did the fuel look like on the dyno when it was tuned?

Project Bird

went ahead and just got my tuner to log it on the dyno with wideband

was adding 25% fuel to bank 1 thus messing with the long term fuel trims and making it go rich, like 12.1 afr WOT..

we disabled LTFT, thinking bank 1 o2 may be going bad.. or possibly have a intermittent misfire on that side making the sensor think the motor is lean, but misfire tables are maxed out so no codes

anyways, car made 12 less rwhp and 6 less tq today than it did back in october.. It was 10 degrees cooler today and same humidity as opposed to then, weird but I care more about trap speed than dyno numbers.

Sladester2

iTrader: (1)

Just for an example my cam only c5 auto with a bigger stall traps about 94mph in the 1/8th

Pro Stock John

iTrader: (34)

... Bad 02 on that side, vacuum leak, intake manifold not sealed...

Or could be also shift points are off.

I'd think you'd go 92-95 in the 1/8th.

Project Bird

update: set my aeroforce scan gauge to watch short term fuel trims, it's both banks loading up with fuel. replaced both sides o2 sensors today and still same problem. will check for leaks soon and try out my buddy's coils on my car

and yes, i agree.. i would think my trap should be 90+ mph. i'm going to do the free ram air mod (i don't know why i haven't yet).. and try and get this loading up at idle issue sorted out and go back to track and see what it has in it. shift points should be fine, i think they are around 6250 or so, i really need to just get a copy of my tune file

Sladester2

iTrader: (1)

Mine are 6500-6600 although my cam is quite a bit larger