I Want To Run Lean
#1
Elite Member
Thread Starter
iTrader: (16)
Join Date: Aug 2007
Location: Houston, TX
Posts: 9,293
Total Cats: 475
I Want To Run Lean
I got MS II going and have a wideband hooked to MS and a 12 dollar panel meter guage, so I can measure, datalog, and watch my AFR. I want to set the car up to get the best gas mileage. I know a Ring and pinion swap would help, but for now I just want to lean it out for best mileage.
I have it set for 12.5:1 at WOT, and 16:1 at cruise. I've run it 17:1, and it ran fine. Should I just keep moving it lean till it starts to stumble, then add a little fuel? Lean at cruise shouldn't hurt anything as far as I can see. Is there a majic number for best gas mileage? I'll be making a 270 mile trip friday and I'll be able to see what my new mileage is running MSII.
Thanks.
I have it set for 12.5:1 at WOT, and 16:1 at cruise. I've run it 17:1, and it ran fine. Should I just keep moving it lean till it starts to stumble, then add a little fuel? Lean at cruise shouldn't hurt anything as far as I can see. Is there a majic number for best gas mileage? I'll be making a 270 mile trip friday and I'll be able to see what my new mileage is running MSII.
Thanks.
#4
2 Props,3 Dildos,& 1 Cat
iTrader: (8)
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,338
Total Cats: 573
I'd keep it richer than 15 anywhere but flat no-throttle cruise or lift-off just because you'll not want to be too lean as the manifold pressure swings from vac to boost.... I'd call that limit 60 kpa absolute, maybe 50. I cruise between 15-16:1 and shut off the injectors below about 17-20 kpa.
Otherwise your only limiting factor is going to be EGT. You dont want to run super lean and end up with 1500F EGT at cruise or you'll burn up valves with all that mileage. Try 1300-1350F for a max EGT during cruise.
Otherwise your only limiting factor is going to be EGT. You dont want to run super lean and end up with 1500F EGT at cruise or you'll burn up valves with all that mileage. Try 1300-1350F for a max EGT during cruise.
#5
I'd keep it richer than 15 anywhere but flat no-throttle cruise or lift-off just because you'll not want to be too lean as the manifold pressure swings from vac to boost.... I'd call that limit 60 kpa absolute, maybe 50. I cruise between 15-16:1 and shut off the injectors below about 17-20 kpa.
Otherwise your only limiting factor is going to be EGT. You dont want to run super lean and end up with 1500F EGT at cruise or you'll burn up valves with all that mileage. Try 1300-1350F for a max EGT during cruise.
Otherwise your only limiting factor is going to be EGT. You dont want to run super lean and end up with 1500F EGT at cruise or you'll burn up valves with all that mileage. Try 1300-1350F for a max EGT during cruise.
I choose a Honda CRX HF..56 MPG back in 1990...
#6
I'd keep it richer than 15 anywhere but flat no-throttle cruise or lift-off just because you'll not want to be too lean as the manifold pressure swings from vac to boost.... I'd call that limit 60 kpa absolute, maybe 50. I cruise between 15-16:1 and shut off the injectors below about 17-20 kpa.
Otherwise your only limiting factor is going to be EGT. You dont want to run super lean and end up with 1500F EGT at cruise or you'll burn up valves with all that mileage. Try 1300-1350F for a max EGT during cruise.
Otherwise your only limiting factor is going to be EGT. You dont want to run super lean and end up with 1500F EGT at cruise or you'll burn up valves with all that mileage. Try 1300-1350F for a max EGT during cruise.
I choose a Honda CRX HF..56 MPG back in 1990...
#12
Supporting Vendor
iTrader: (5)
Join Date: Jun 2006
Location: Duluth, GA 30097
Posts: 803
Total Cats: 0
An N/A car will usually make best power between 12.6-13:1 at WOT. If the car is dedicated race (especially road race)... stay closer to 12.6:1 for longevity.
__________________
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
#15
Supporting Vendor
iTrader: (5)
Join Date: Jun 2006
Location: Duluth, GA 30097
Posts: 803
Total Cats: 0
It really depends on the car, but generally speaking in Miataland-- maybe 12.3-12.4:1 at 7-8psi and 12:1 flat at 12psi. Up around 14-15psi I'm looking for around 11.8:1 or maybe a tad richer.
This is on a properly intercooled turbo Miata, no water injection, etc. Everything factors in... If your IATs are out of control you might have to run stupid rich as a bandaid for poor intercooling, though really you should fix your IC problem. If you're running WI you should be able to keep it in the low 12's as the WI will keep the combustion temps lower and help prevent det.
This is on a properly intercooled turbo Miata, no water injection, etc. Everything factors in... If your IATs are out of control you might have to run stupid rich as a bandaid for poor intercooling, though really you should fix your IC problem. If you're running WI you should be able to keep it in the low 12's as the WI will keep the combustion temps lower and help prevent det.
__________________
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Jerry a.k.a. 'FoundSoul'
DIYAutoTune.com
'91 Miata BEGi S3 GT2560 w/ MSPNP - 14.1psi - 253whp, 232wtq
'95 Miata n/a
A few other cars....
Last edited by FoundSoul; 02-07-2008 at 03:24 PM.
Thread
Thread Starter
Forum
Replies
Last Post
Greasyman
General Miata Chat
2
09-28-2015 10:44 AM