7845

iTrader: (1)

tonight i did a WOT run in 3rd and noticed my duty cycle at 82%. i have motron 60s with 58psi with 0 vaccum. this was at 15psi of boost. fuel system is dual 255s -8 feed -6 return. does thsi sound reasonable? also is there any reference to HP that is being made with this much duty cycle on properly setup fuel system?

Old Geezer

iTrader: (3)

Unless the FPR is boost referenced, the "delta" op pressure at the injs is 58-15, or 43. 3 bars is where those injs are rated.
I'd not think the DC @ 82% is out of line, unless the 60's are not well matched to the FWHP.

7845

iTrader: (1)

yes its a 1:1 FPR

Old Geezer

iTrader: (3)

Ok. Is 600FWHP a close estimate of what U R making?
Some quiky calcs show that, at 600FW, BSFC @ .6, and a duty cycle you have reported, the injs should be operating in the 54.9#/hr area.
@ 58psi op pressure, the injs are now rated at 69.28#/hr. Your reported DC of 82% looks to have a flow of 56.8#/hr.

Looks really close to me....

Lonnies Performance

iTrader: (16)

Boost reference your regulator & you will be good for approx 900rwhp.

You are sacrificing a lot of flow by running fixed pressure.

7845

iTrader: (1)

my FPR is a boost reference 1:1 and im still at the duty cycle

backchannel

I believe if your scaling is less than actual flow, the reported duty cycle will be higher than actual. My afr will richen well past 100% duty with 60's underscaled for the limit of the pcm

7845

iTrader: (1)

my injectors are scalled 72.30 across the table

backchannel

At 0.6 you should be about 99 hp/inj.uncorrected

7845

iTrader: (1)

huh, im not following

backchannel

bsfc of 0.6[6lbs of fuel /10 hp]average for forced induction motor.
82% of 72.3=59.286lbs of fuel used per injector
59.286/0.6=98.81 hp per injector
6cyl would be 593 hp
8cyl would be 790 hp
about- so I expect you are seeing that hp uncorrected if the tune is at 0.60 bsfc.

7845

iTrader: (1)

wow, i see if that is the case this is probably the strongest 4.8 litre motor around. that PT88 is wicked

kbracing96

iTrader: (25)

Show me a log where you get those DC numbers WITH OUT it being in a tire spinning, 7500rpm spike, then you can claim the highest 4.8 around here,

backchannel

we did 442 hp with 1.07 litre 4 cyl and 8- 42 lb injectors

AeroKing

so my Siemens 65#'ers running at 98% duty cycle means i'm making 636hp. i dont think so.

backchannel

explain

AeroKing

where in the equation do you factor in AFRs? cause i could run 12.5 under 20psi of boost, or i could run 10.0 at 20psi. so where does the AFR count

OutlawZ

iTrader: (4)

that is a good question...

FWIW, I'm at 49 psi on a set of 50lb'ers and they are rated at 43.5... So they are running around 55 lb/hr......

Making about 625 WHEEL HP at 11.50:1 AFR on nitrous.... Duty cycle maxes out at around 75%..... This is with a TH400, ATI 4000 stall, 9"..... Probably making around 750-775 flywheel.....

So for a HP versus duty cycle sample is why I responded....

backchannel

afr doesn't factor in; bsfc.,observed hp, % of duty cycleXscaling and # of injectors. You need any three to calculate the forth. If fi, you also need the fuel pressure to be referenced1:1 with boost. I am only in this thread because I thought this was too basic for tuners to bother explaining

backchannel

fuel flow does not go up at the same rate as fuel pressure-you're 55lb is wrong.
Is 625rwhp actual or corrected. What are your injectors scaled at? Read post 19. You are aware that this is fwhp math.
this fails if the injectors are not flowing what the computer says.