coolguycooz

I was wondering how much would a Walbro 255 change your AFR by? how rich would it make you across the board? The reason why im asking is because im maxing out my injectors 105% IDC, but the thing is im only runing 21 psi? so im wondering if throwing in my fuel pump will richen me up a lil reducing my IDC.

recompile

iTrader: (38)

I recently tuned an 03 Evo 8 that had stock fuel/timing maps, running MBC holding 21 psi... he had 100% IDC at 6000RPM and 12.0 AFR with as high as 12.5 after redline !!!

We installed a Walbro, made NO other changes, and he had 10.0 AFR to redline. This allowed us to take out some fuel and he now has IDC of 90% at redline with 11.5 AFR running 23psi.

DEFINITELY buy the Walbro

DEFINITELY buy a wideband

Mellon Racing

iTrader: (38)

with an EVO8 it's going to richen it up significantly.. EVO9, not so much. Your IDC's should drop considerably AFTER you lean it back out.

coolguycooz

Thanks guys, i knew a fuel pump was a must for evo8's its just i never had any AFR problems or high IDC %s before. I'm assuming the efficiency of my stock pump decayed a lil in combo with everything else.

Thanks for the reply, I order my walbro 255 1 min ago

Mellon Racing

iTrader: (38)

good deal! when you install mods and raise the boost, you're increasing the air intake significantly and the stock pump simply cannot maintain the proper fuel pressure to keep up with demand...so the higher the boost the leaner it will get and the IDC's will skyrocket.

our system is a 1:1 rising rate meaning for every psi of boost increase the fuel pressure regulator should allow the fuel pressure to also rise 1psi, when that doesn't happen, you start leaning out and IDC's rise.

Jack_of_Trades

iTrader: (17)

I run 23psi and 21psi at redline and I hit roughly 98-100% (roughly 11.0:1 at redline)from 6500-7500rpms with a 255 HP Walbro. It seemed a tad bit higher than I would have expected with the wally pump. I just purchased a pruven fuel pressure adapter plate to confirm my fuel pressure is within spec. Is this roughly where you guys see your IDC's maxing out at too? I was going to get larger injectors but I also planned on running alky so i think I'll preserve the stock injectors and get the alky first since it will help me to lower my IDC's anyhow.=, while helping me tune more aggresively for a bit more power.

Mellon Racing

iTrader: (38)

being tuned for 11.1 is going to use significantly more fuel than say 11.5 and has much to do with the high IDC you're seeing.

I'm running 680cc injectors which most will tell you is too small for my mods (20g evogreen, fmic, cams etc..) but I plan on adding water/meth injection soon so I won't need nearly as much gasoline in the mix. Will it be enough injector... time will tell

madmax4499

iTrader: (3)

chris, what meth kit are you looking at

Mellon Racing

iTrader: (38)

I'm in love with the aquamist HSF-5...I have a customer that's looking to sell his so we're talking about trading out some tuning work/money for the kit. If that falls through i'll just order one eventually. I'll probably start off with water and eventually do a 50/50 mix of water/meth.

the evogreen just isn't impressive on pump gas.

Jack_of_Trades

iTrader: (17)

The one thing that confuses me is how people run cams with stock injectors and a 255. I'm hitting 100%IDC without cams yet I know tons of people are running stock injectors with cams too.

Mellon Racing

iTrader: (38)

what AFR are you tuned for in a 3rd gear pull?

Jack_of_Trades

iTrader: (17)

around 12:1 at peak load, 11.5:1 at peak torque and tappering to roughly 11:2-11.0:1 at redline. The only thing I can think of is my WB readings aren't correct. Can you recalibrate the zeitronix WB O2 by pulling it out of the exhaust stream and turning the key to the on position? I've had it for almost a year now on my 2G and swapped it over to the evo. I'm sure a recal or new sensor might be in order.

EDIT: Just talked to Zeitronix and said their setup is self calibrating

coolguycooz

Mellon i know all that bro, thanks for the refreshing review. All i am simply trying to say is, i have been runing 21 psi for 6 months and my IDC were at 93-95% tops. Out of nowhere im pushing 100+% and yes i know it has gotten colder so i my MBC might spike a bit higher, so i turned it down a tad bit for the winter time temps. and all i wanted to know is why my IDC would suddenly jump by 10% without anything changing, 10% is a significant amount. I am a guy that likes to know why stuff happens rather then just swapping a part and calling it a day never really fully understanding what caused the problem in the first place.

Jack_of_Trades

iTrader: (17)

EDITED ORIGINAL POST:

Brain fart.....ignore the smell

Mellon Racing

iTrader: (38)

the colder air could be the culprit, did the idc's go back down when you lowered the boost a tad?

lower boost = less air/fuel = lower idc