StatoJase

Hi, chasing a few opinions on a blowthru carb problem I had at the track last night, Good burn out, pulls hard till about 3/4 track and its almost like the fuel bowls are being emptied. starts to break up then lean out. Wondering if my stock needle and seats or my 13204 aeromotive reg with 2x -6 feeds causing it. What are the limits of these?

I have restricted the hsabs and the afr is steady till this happens, i'm using a1000 pump with -8 feed and return, 6 psi base pressure, rises nicely seeing hat pressure.

3700lb full weight street car, stock ls1 with cam, intercooled vortech t trim, victor jnr intake, self modded 800 holley, turbo 400, 3000 stall, 9 inch with 3:7 gears.

Any thoughts? car ran 12.08 at 111mph, 1.7 60ft and put down 480rwhp on dyno. Set up for 10psi boost but noticed heaps of belt slip soot over everything so obviously not getting it all at the track.

turbo iroc

iTrader: (1)

I have the same problem, I did a fuel pump test on my a1000 and it took 47 seconds to pump a gallon of fuel. I'm thinking fuel pumps shot.

StatoJase

Good point, The pump has been in the car for a couple years but hasn't had that much use really. Definitely Worth checking filters and flow rates then at least I can rule it out either way.

just tested it free flow into a bucket, only got a 30 second shot as the bucket filled up really fast. Measured at 5L for the 30 second burst which converted over to 160 gal/hour or there abouts with the relay bridged on the car so around 12 volts.
Don't think its my pump and filter screens clear.

must be carb related.
Msd 6010 has about 30 deg at cruise, 27 at 0 and tapers down to 15 at 9 psi. also my graph drops down to zero not far after that as I dont want to push anymore boost through.

StatoJase

self modded carb set up 76f/95r jets .078" pvcr front with 6.5 pv, no provision for rear pv.
50cc pumps with brown/blue pump cams set correctly, needed an agressive shot to clear a lean transition into boost. stock press in hsabs restricted with wire at the moment which has flattened out the curve pretty good.

going to go over the carb again to see whats going on. First run at track but been on dyno twice and driven on street a bit. Problem hasn't arisen due to not going full throttle that long on the street.

turbo iroc

iTrader: (1)

OK sounds like my pump is shot...ill check the filter first tho. I would try to up the rear jets to 99 , also check the obvious stuff first, fuel pressure boost
reference, floats, etc. Check theturboforums.com for all your blow thru needs. Its THE blow thru website.

turbo iroc

iTrader: (1)

Also I ran a home modded Holley for a while and just couldn't get it work right so I went with a qft750ban by quick fuel technologies. It has adjustable everything and I currently have the pvcr restrictions totally removed ( about 1/8in hole) 99 jets in the rear and 74 up front. Cruise afrs are perfect along with the idle afrs. Just starts to go lean in higher rpms, I see 12 and I let out of it. This is in a 402ci lq9 l92 heads with 88mm Turbo. Timing is about 27 idle map sensor takes it up as high as 38 cruising then tapers from 30 down to 22 when in boost. 11 Psi boost 9.3 :1 CR no pinging whatsoever.

MillsMotorvation

Check FPR, that was my problem. What FP you running to carb, may need to add a pound or 2. Add a pound or so of fuel see if the car runs better.

StatoJase

I've run the blow thru stock bottom ls1 for a learning curve and to see what I can get out of it. Have a forged 408 waiting in the wings for after but will be efi and turbo'd. I'm running the aeromotive 13204 reg with 7 psi fuel pressure at idle. When I rev it in park fuel pressure rises with the hat pressure, quite alot. Going to try log whats going on when I go for a spin with the wideband and get a better picture of whats happening. Not the same on the street though.

StatoJase

threw the laptop in car and logged a burst, afr was sitting at about 12.4 in boost. Not good!
raised float level to half glass, FP at 7.5psi, and threw more jet at it and run again, pretty fat cruise 11 then into boost drops to 10.3 and flickers between that and 10.7afr run out of road but stayed fat till I had to back off at about 110 mph.

Think I got a handle on this now, Try get my cruise back in line, play with Wot and back to track on wednesday.

MillsMotorvation

Add a pound of boost to eat the fuel, or add timing, if there is no knock.

StatoJase

I actually backed the timing off a bit out of fear when all this started. Went to track tonight with vent tubes extended bout 8 inches facing the hat entry. Pulled jetting out to suit and ended up 74/90 to achieve a 11.5 ratio and rattled off an 11.8 quarter mile at 117mph. Heading in the right direction at least I think