Lean spike and acceptable amount?
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TECH Apprentice
Joined: Sep 2004
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From: Kona, Pearl Ridge
Lean spike and acceptable amount? I get a quick lean spike about 3100rpm and returns to "normal" around 3200rpm. Window is set to come in at 3000rpm. A confusing thing is that KR would come in the first run but on the second run it would be less and by the third run it was gone all together.(bottle ran out too 
)
How lean is acceptable for this 100rpm window when the spike happens. My wideband/ HPTuners show 16.X-1 afr at the peak. I think i worry too much its only 100rpm... but better safe than sorry new short blocks aint cheap.
)How lean is acceptable for this 100rpm window when the spike happens. My wideband/ HPTuners show 16.X-1 afr at the peak. I think i worry too much its only 100rpm... but better safe than sorry new short blocks aint cheap.
That lean spike might be from draining the fuel rails before the pump can catch up right when you hit it .
Mine did that before i put a bigger pump in the car .
Are you tapped into the end of the stock fuel rail and using a stock fuel pump ?
If so , upgrade your intank pump .
Mine did that before i put a bigger pump in the car .
Are you tapped into the end of the stock fuel rail and using a stock fuel pump ?
If so , upgrade your intank pump .
Thread Starter
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From: Kona, Pearl Ridge
Thats what i thought it was but it only has the quick spike then it handles the load. Going to try and get the bottle filled today so i can set my jets for optimum afr for 100, 150shot.
The KR i still dont get. one run its there and the next its completely gone. i think i may just go with a stand alone in the battery compartment and leave the stock fuel system to handle the motor.
The KR i still dont get. one run its there and the next its completely gone. i think i may just go with a stand alone in the battery compartment and leave the stock fuel system to handle the motor.
Originally Posted by chris.shea
The KR i still dont get. one run its there and the next its completely gone. i think i may just go with a stand alone in the battery compartment and leave the stock fuel system to handle the motor.
Put a bigger pump in the tank to be safe and get rid of that problem all together .
255 walbro pumps are cheap nowadays .
Chris, normally a lean spike that lasts less than a second is accepted in the industry. However, I think just a pump and you'ed be fine. Myself, I don't like any lean spike, and have neutralized this issue with fuel system upgrade, much cheaper than a stand alone. Did you have spike on each run?
Yes, as stated your clyinder pressures go down as bottle goes empty, so likely you need to pull some timing.
Robert
Yes, as stated your clyinder pressures go down as bottle goes empty, so likely you need to pull some timing.
Robert
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From: Kona, Pearl Ridge
Answers noted. I was able to fill the bottle today but roads are damp and wont be able to log tonight. I really want to get some full bottle runs in so i can tackle the KR problem.(either pull timing 
or mix fuels $$$)
pic attached to show the lean spike. last pass so bottle pressure is low thus causing the fat afr throughout the run and lack of KR.
or mix fuels $$$)pic attached to show the lean spike. last pass so bottle pressure is low thus causing the fat afr throughout the run and lack of KR.
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From: Wichita Falls, TX
Looking at a lean spike over the 13.1 points is a good starting point. The spike being like a mountian top. Look at your time from the started 13 to the ending 13. That timeline needs to be under 1 second.
If your spike looks like a cam lobe there is something wrong with fuel delivery.
If your spike looks like a cam lobe there is something wrong with fuel delivery.
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From: Kona, Pearl Ridge
My n/a afr is 12.3 just right before the spike. then it kinda bottoms out around 9.7 and climbs to 10.3 right before redline. bottle was going empty which explains the 9's but on a full bottle run my afr was just as rich but i was only logging with the fast wideband so i cant really tell where. im going to bump down on a fuel jet and log again to see if i can get my AFR where it needs to be and see if the less fuel(required) reduces the spike upon activation some. its pulling enough fuel to give me 9.7 afr when target is 11.5-11.8
thats as close to zoomin in as i can do the times are... spike starts @ 17.375 seconds, peaks @ 17.578seconds and bottoms @ 17.968seconds in the run.
thats as close to zoomin in as i can do the times are... spike starts @ 17.375 seconds, peaks @ 17.578seconds and bottoms @ 17.968seconds in the run.
On The Tree
Joined: Jul 2006
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From: houston, TX
Try a nitrous line that is six inches longer from the nitrous solenoid to the plate. Nitrous moves faster than fuel since they are under such different pressure. I had this problem a NX plate kit and solved it by having a six inch longer nitrous line than the fuel line. Btw, this was a ford efi plate kit, but the principles are the same.
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From: Kona, Pearl Ridge
Update Got some passes in last night 
Changed up my fuel jet and got my AFR to a decent ballpark.(62N,33F). on the bottle my afr is 11.1 then gradually climbs to 11.5 towards redline. im still on the fence as to try a little smaller fuel jet and lean it up. didnt get any KR either. too bad the track was crap or id post up decent numbers but i wasnt able to get anything better than a 2.5 60ft all night long... it was ricernight so they dont prep the track.
Changed up my fuel jet and got my AFR to a decent ballpark.(62N,33F). on the bottle my afr is 11.1 then gradually climbs to 11.5 towards redline. im still on the fence as to try a little smaller fuel jet and lean it up. didnt get any KR either. too bad the track was crap or id post up decent numbers but i wasnt able to get anything better than a 2.5 60ft all night long... it was ricernight so they dont prep the track.
Thread Starter
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From: Kona, Pearl Ridge
Originally Posted by Frost
Your timing is at 31deg at the lean spike and climbs thereafter for a bit.... This isn't a bit high?
a minute amount of KR 0.4* but only happened once so im living with it.
