How Much Fuel Actually Burns? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


ECUs and Tuning Discuss Engine Management, Tuning, & Programming

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 01-27-2015, 07:53 PM   #1
Junior Member
Thread Starter
 
Join Date: Jan 2014
Location: Green Cove Springs, Florida
Posts: 71
Total Cats: 7
Default How Much Fuel Actually Burns?

I have an '03 running FM's Voodoo II ( yeah, I know). I have FM's Crossflow radiator and their stage II fan kit. Intercooler. I'm currently running 8 psi and my Wideband shows about 11-11.5 at full boost. Car runs fine no overheating or detonation.

Recently on a club event, the driver of the car behind me commented on how rich I was running in boost. Some black smoke he said. At 11-11.5 I can see how that could be.

QUESTION IS: is the purpose of fueling at boost to provide fuel to be burned? Or to act as a cooling agent? Some of each?

At 8 psi I'm considering tuning the Voodoo box to try to get closer to a 12 AFR. Would I lose the cooling properties of the extra fuel? Or is it what I should aim for.

I'm aware of the virtues of Megasquirt. I'm just not ready to give up my stock ECU. Trying to get the most efficiency out of what I have, while keeping the engine safe.

Paul
pmhellings is offline   Reply With Quote
Old 01-27-2015, 08:03 PM   #2
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

Extra fuel cools the charge a bit. It also helps prevent localized lean spots in the fuel/air mixture by putting extra fuel in. It also slows down the flame front, which shifts peak pressure to the right of TDC, which lowers peak pressure in the cylinder. This will allow you to add timing to the engine to shift the curve back to the left (closer to TDC). Generally on a knock limited engine, rich allows more timing, and makes more power than running lean and running less timing, and is "safer" too.
patsmx5 is online now   Reply With Quote
Old 01-29-2015, 08:54 PM   #3
Junior Member
Thread Starter
 
Join Date: Jan 2014
Location: Green Cove Springs, Florida
Posts: 71
Total Cats: 7
Default

Thanks Patsmx5. A little technical, but answered the question.

Paul
pmhellings is offline   Reply With Quote
Old 01-29-2015, 10:54 PM   #4
Elite Member
iTrader: (1)
 
Join Date: Jun 2014
Location: Austin, TX
Posts: 2,842
Total Cats: 271
Default

You could also inspect your plugs to observe if its bad and/or inadvertently upgrade your ignition to light up that rich mix more efficiently
Girz0r is offline   Reply With Quote
Old 01-30-2015, 04:33 AM   #5
Elite Member
 
codrus's Avatar
 
Join Date: Mar 2007
Location: Santa Clara, CA
Posts: 3,877
Total Cats: 344
Default

Personally I don't think I'd mess with the Voodoo to try to lean it out. You've got a 10:1 compression ratio motor with stock rods, and a piggyback fueling system that lacks a lot of safety measures. Running 11:1 *is* your safety measure.

I run something like 12.5:1 at 8 psi on my car, but I've got a built motor, 9:1 compression, a full ECU that knows about the turbo and the knock sensor, and I run 95 octane in it.

--Ian
codrus is offline   Reply With Quote
Old 01-30-2015, 08:14 AM   #6
Senior Member
iTrader: (1)
 
Join Date: Jan 2011
Location: Chattanooga, Tn
Posts: 1,038
Total Cats: 157
Default

I personally don't think running 11:1 on a 8 PSI motor is a "safety margin" and unless your oil change schedule is on the aggressive side....might actually be a detriment to it's longevity. If your motor is detonating due to spark timing or compression being too high...throwing fuel at it isn't the answer.
TNTUBA is offline   Reply With Quote
Old 01-30-2015, 11:45 AM   #7
Moderator
iTrader: (11)
 
sixshooter's Avatar
 
Join Date: Nov 2008
Location: Tampa, Florida
Posts: 15,654
Total Cats: 1,559
Default

12 or 12.5 would be better, but as stated above, since it is a Link you have less fine control. If you decide to remove a little fuel, compare your timing to others with similar compression to ensure you aren't playing with fire.
sixshooter is online now   Reply With Quote
Old 01-30-2015, 04:13 PM   #8
Junior Member
Thread Starter
 
Join Date: Jan 2014
Location: Green Cove Springs, Florida
Posts: 71
Total Cats: 7
Default

This is the OP. There is no detonation and the motor is running fine. To re-state, I wondered about how much of the fuel was for, well, FUEL, and how much was for the cooling effects. As stated, I'm running about 11-11.5 AFR. I'm considering dialing the AFR back to about 12 to minimize over-rich condition. I agree with TNTuba with respect to excessive fueling requiring more aggressive oil changes (currently 3,000 miles. Synthetic)

My fuel management is via a voodoo box and I'm running -4* static spark retard. I appreciate the thoughts of those more experienced than I am.
Paul
pmhellings is offline   Reply With Quote
Old 01-30-2015, 05:48 PM   #9
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

Yes if you had a standalone, you could run it leaner possibly. But with what you have, I'd leave it alone. 10: comp with no timing control running boost with piggy backs is not ideal, leaning it out could be dangerous.
patsmx5 is online now   Reply With Quote
Old 01-30-2015, 07:25 PM   #10
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Quote:
Originally Posted by pmhellings View Post
To re-state, I wondered about how much of the fuel was for, well, FUEL, and how much was for the cooling effects.
I hate to be a wet blanket, but I honestly don't think you're going to find a definitive answer here.

This forum is host to a tremendous amount of solid practical experience built on empirical research and real-world application, but this question exceeds that which can be expected of even the most experienced engine tuner. I would suggest that you seek out a forum frequented by members of the SAE (society of automotive engineers) and its many university-level affiliates. These will be the people most likely to be able to provide a satisfactory answer supported by reputable data.
Joe Perez is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
Walbro 255lph Fuel Pump $50 lsc224 Miata parts for sale/trade 2 10-01-2015 10:17 AM
"Chimney Ethanol" E100 MiataGarage Engine Performance 5 09-30-2015 12:04 AM
why is my car running like pewp? (tune/datalog) itsMikey MSPNP 3 09-28-2015 07:40 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 10:42 AM.