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what percentage of fuel should I pull to increase efficiency

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what percentage of fuel should I pull to increase efficiency

Old 10-10-2008, 09:54 PM
  #1  
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Default what percentage of fuel should I pull to increase efficiency

(JD wanted me to post this here since he feels it would benefit others. I didn't save my first message to him, i'll go ahead and re-type it with more detail.)

Recently I finished my turbo build. For the tune, I decided to go with a bin xenocron posted on his directory which is labeled "Stock GSR motor / 9-10psi / 50 trim t3/t04e / 450cc DSM injectors". The tune runs my car pretty well, no rich smell in the exhaust, idle sits nicely (a little high but that's ok with me @1k rpm).. after about 70 miles I pulled the new set of NGK 4554's out and they show it's running a little on the rich side. This backed up my below average MPG clocked with the first 1/2 tank, which came out to be 21 mpg, give or take 2.

I want to know what a good percentage of fuel would be to pull from the vacuum portion of the map to get a little more out of my tank. I would just throw my wideband on and do it the right way, but I messed up by letting a friend borrow my plx (lesson learned).

my setup is as follows, crappy cellphone picture of the #3 plug is below as well:

b16a 81.5mm
9:1 pistons, h-beam rods
gsr cams

t3/t04e 57 trim
dsm 450's
2.5" down pipe





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Old 10-10-2008, 09:54 PM
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Default Re: what percentage of fuel should I pull to increase efficiency

JD's PM response

Originally Posted by Joseph Davis
I'm on my phone so I can't see the pics until later.

Part throttle mpg improvements are easy. There is no real load in that range as the engine makes less than 20 whp at a 60 mph cruise. Lean that ---- out and as long as it still cruises smooth it's fine. I would do -5% increments.

Also, B16s want different timing in different regions... WOT everything is probably fine, but you might pick up a little power and fuel efficiency by pasting B16 ignition values in the non-boost regions. Given the big drop in CR, I'd also add 2-5 degrees to the same region.

4554s are a bit cold if you aren't at or breaking 300 whp. I may have you step down to a 4091 after I look at the pics.

Can you post everything you asked and my reply to the Engine Management forum? We really should do this where people can learn from it.
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Old 10-10-2008, 10:01 PM
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Default Re: what percentage of fuel should I pull to increase efficiency

I go with JD's 5 percent mark.

On 450s it won't be too big of a jump at a time, and yeah just keep leaning it out till it stumbles. I am a ----- bitch and I like to richen things up early in the game on the load side of things, I'll typically drop it to 14ish around 12-10 inches
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Old 10-12-2008, 11:39 AM
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Default Re: what percentage of fuel should I pull to increase efficiency

For 450cc, 10% fuel is ~1 AFR point.

What your engine will tolerate as a "lean burn" is all over the place, so you need to play around a little. Again, there is no real engine load so don't worry about hurting your engine - if she runs smoothly it's good to go.

And from what little I can make out of the plug in that excellent picture of your valvecover it looks fine. Sooty well, clean ceramic, no appreciable deposits or oil buildup on the ground strap (engine is in good conition, most these days aren't). I'd like a better view of the ground strap so I can place the heat mark, and a view down the well so I can see the base of the ceramic.

PS - I've been asking for high res close up pictures of plugs for years, no one ever comes through. :P

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Old 10-12-2008, 04:37 PM
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Default Re: what percentage of fuel should I pull to increase efficiency

old 1.6 MP camera can only do so much

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Old 10-13-2008, 02:32 AM
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Default Re: what percentage of fuel should I pull to increase efficiency

what rpm/load is that?
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Old 10-13-2008, 03:52 AM
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Default Re: what percentage of fuel should I pull to increase efficiency

4000-7500 WOTin 3rd gear, D16Z6 on 85 shot of nitrous, 87 octane pump gas, 30 lb red top injectors.......








Thi pic wasn't in reference to E85, but the JD's mention the lacking of good pics.
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Old 10-13-2008, 10:56 AM
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Default Re: what percentage of fuel should I pull to increase efficiency

I still can't see all the way down into the well, Bone. :P
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Old 10-13-2008, 12:46 PM
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Default Re: what percentage of fuel should I pull to increase efficiency

looks like you could run a little colder plug from that picture. Cant really see how many threads are discolored tho. Looks to be 3-4. JD is asking for pictures of the bottom of the insulator (where the white part meets metal) That is where you read the fuel ring.

btw, if you have the ability to adjust individual ignition and fuel trims, you should really take advantage of it.
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Old 10-13-2008, 01:14 PM
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Default Re: what percentage of fuel should I pull to increase efficiency

May be a stupid question but when you want to read your plugs you're supposed to rip on it until the rpm you want to check out then imediately shut your car off and pull them right? Cause otherwise you'll just be reading you part throttle low load as you cruise back to the shop?
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