FigsZ28

iTrader: (70)

How can I get rid of this lean spike?? Here is my fuel set up: Walbro 255 inline and intank, Delphi 42lb injectors, everything else is stock, ie lines and rails. I didnt get a chance to log my inj. duty cycle on nitrous but they are at 70% NA. I was thinking of putting in some 60lbs inj I have along with buying some type of aftermarket fuel rail. Will this help any?? Thanks

Matt@HSW

iTrader: (14)

A regulator on your fuel rail (along with a return) could help a little. I don't think rails or new injectors will help you with the wet shot, but NA you might benifit from them. You could try a longer N2O line from the solenoid to the nozzles or use a controller to delay the N2O solenoid to get rid of the spike if you really wanted to.

Matt

white2001s10

iTrader: (4)

Depends on what is causing the spike.
Have you checked to see what your fuel pressure is doing?

227Hawk

iTrader: (1)

Try running a Hot-wire to the pump. My guess is it's looking for more power.
Hawk

BadAssFast

iTrader: (2)

I'm in the middle of sorting out a new system. I had a more severe problem perhaps caused by getting crap in my fuel solenoid (or something) and possibly even a weak new Racetronix pump...although i'll bet it was something I did at install...anyway...after speaking with Paul at Thunder today it seems like the stock fuel rails should be fine for me and from what I can tell you as well. If my pump is good, and when the new solenoid gets here, i plan on starting with a minimal 75 shot and watching FP...if okay then 100 shot...if okay...150 shot. I'll be watching my FP guage like a hawk. These lean spikes are common...to what degree is another thing.

cantdrv65

iTrader: (3)

Id think you be close to the limits of that 255 intank and an inline pump is not going to do much good. Id go with a dual intank setup for that much power....

jimmyblue

iTrader: (11)

Thing is if it's a "spike" then the fuel system does catch
up, it's just not fast enough to anticipate or even react
timely. A slower roll-on of the shot (long hose perhaps
acting as an accumulator, slowing / smoothing?) or some
sort of transient enrichment (think accelerator pump but
nitrous-specific) I think is what's wanted (for a spike;
have to know whether it is truly transient or a general
problem just made briefly worse).

The problem really (I think) with the intrinsic slowness
of both airflow metering inputs (MAF, IAT) relative to the
step temperature drop with the shot. Jacking the IAT is
relatively easy (though getting to two distinct settings
for enrichment and timing pull, more complicated). The
MAF, fuggedaboudit unless you're up for a real electronics
project.

If you know the width of the lean spike maybe making a
two-stage IAT tricker is not a bad idea; two relays, one
for main shot timing and another energized only on the
leading edge to bury IAT totally (-40C), then release back
to (say) the second-leftmost (-30C) column in the PE vs
IAT adder table. Both of these would index the leftmost
IAT spark adder column (-10C). Talking probably 10 -20
bucks' worth of parts and a night worth of soldering /
wiring it up. Plus of course you'd have to do the tuning
to populate those tables properly, and tweak in the
comp shot "dwell" to cover the lean dip but not make
it soggy too long after.

white2001s10

iTrader: (4)

I didn't catch all the data in the original post.
It looks like this is on a 408 cube engine.
First thing I'd try is more pump shot as it looks like your spike is around 4000 RPM where you may have just floored the pedal on the dyno?

I don't know if some tuners give you much option for pump shot, but I think you would get quickest response by adjusting the VE table in that area.

The next possibility if pump-shot doesn't work, I'd consider upgrading the rails due to the size of the engine and injectors. Hot wiring the pump never hurts either.

Jimmy, I wanted to add a point about using trickers. I suggest having a bigger spread in your columns than the -40 / -30 you mention for a dual-stage kind of thing. I'm actually more comfortable working in the upper end of the temp scale as well. I really like trickers myself.

If his fuel system isn't keeping up due to the engine/injector size, then unfortunately a tricker is unlikely to help though.

FigsZ28

iTrader: (70)

this is what I was thinking, Im thinking that the rails are being emptied when I hit the nitrous, thats why I think If i put bigger rails/injectors it should help out some. If that dont work ill go stand alone for the nitrous.

Robert56

iTrader: (2)

I agree with Matt, get a reg and return at the rails. you'll never see optimum performance from your current fuel system until you do. this will keep pressure and volume stable at your heaviest load times, and right now it is not able to do this. changing over will not get rid of your lean spike alltogether, but will allow your fuel system to work to it's best. Then you can do/try some of the other tricks if you want to try to eliminate it altogether. If it's just a second or less, it realy does no harm, unless it's a gigantic spike then you have a coupleof issues together possibly. Stock rails will support your hp level when everything else is up to par. I would get a fuel pressure gauge and log that as well, maybe you'll see exactly what the problem is rather than speculation. some things to think about anyway. Nice numbers by the way.
Robert

FigsZ28

iTrader: (70)

thanks Robert, Ill be doing some logs tommarow and checking out what the fuel pressure is NA , and on nitrous. thanks again guys for the input, im a newbie to N20 Any sugestions as to which regulator to get??

cantdrv65

iTrader: (3)

Agreed. If your running the stock in tank reg you need to ditch that junk....