Turbo Tuning and Fuel Economy
03-22-2007, 06:56 AM
#1
Registered User
Thread Starter
Join Date: Jul 2005
Location: Gie
Posts: 1,670
Likes: 0
Received 0 Likes
on
0 Posts
Turbo Tuning and Fuel Economy
While I have a lot of experience with the flow dynamics and mechanical workings of engines, compressors, and turbines, I'm a little lacking in the tuning department. Perhaps the tuners, or those familiar with the ins and outs of tuning could shed some light on this subject for me...
Back when my engine was stock, I could routinely get 25/29 MPG city/highway. Naturally, my engine requires significantly more fuel now when additional air is being forced into the engine. But what I am seeing, on long trips and extended highway driving when not in boost, is a highway fuel economy in the 22 mpg range.
I understand this is all in the tune, and my main question is what kind of A/F ratio is needed for low load, part throttle operation? Full throttle situations obviously need a lower A/F ratio in the 11-12 neighborhood, but what about cruising? 14, 15, 16??
The daytime high temperature was around 25 degrees when my car was tuned, meaning the air was quite dense. Now that the temps have warmed considerably, would the less dense air have a huge effect on my performance/economy?
Some simple math...just throwing some numbers out there. If my cruising A/F ratio averages 13:1 and I can safely increase that to around 16:1, I will be reducing my fuel consumption by 18.75%. So a highway average of 22 mpg would increase to 26.125.
I'm not sure what my cruising A/F ratio is right now. I'll hook up my laptop and do some datalogging on the way home from work tonight.
Back when my engine was stock, I could routinely get 25/29 MPG city/highway. Naturally, my engine requires significantly more fuel now when additional air is being forced into the engine. But what I am seeing, on long trips and extended highway driving when not in boost, is a highway fuel economy in the 22 mpg range.
I understand this is all in the tune, and my main question is what kind of A/F ratio is needed for low load, part throttle operation? Full throttle situations obviously need a lower A/F ratio in the 11-12 neighborhood, but what about cruising? 14, 15, 16??
The daytime high temperature was around 25 degrees when my car was tuned, meaning the air was quite dense. Now that the temps have warmed considerably, would the less dense air have a huge effect on my performance/economy?
Some simple math...just throwing some numbers out there. If my cruising A/F ratio averages 13:1 and I can safely increase that to around 16:1, I will be reducing my fuel consumption by 18.75%. So a highway average of 22 mpg would increase to 26.125.
I'm not sure what my cruising A/F ratio is right now. I'll hook up my laptop and do some datalogging on the way home from work tonight.
03-22-2007, 10:31 AM
#2
Registered User
Join Date: Feb 2004
Location: Lafayette, LA
Posts: 591
Likes: 0
Received 0 Likes
on
0 Posts
Stoichiometric is 14.7, that is the theoretically "perfect" ratio for max efficiency. Just enough air to completely combust all the fuel.
Hi load, WOT, etc. you make more power with richer mixture say 12.5. And being supercharged, you want it very rich 11 or 12 to keep the charge cool and avoid detonation.
Light load cruising you can go 14 or 15. Stock may go as lean as 15.5 or 16, but stock is NA. Of course light load, you're not boosting anyway.
You are right to start out rich for safety, then slowly start leaning it out while being careful to avoid detonation, hi EGT, etc. Just take your time and log everything. Don't make big jumps, and don't make any change leaner w/o checking for hi temp, knocking, detonating, etc.
Changes in ambient air temp do affect air density, and therefore your tune. THat's why there is an IAT sensor to compensate. Your EMS has an IAT correction table. Now that the intake temps are higher, you can edit the higher temp end of that curve to get the A/F back in line.
Hi load, WOT, etc. you make more power with richer mixture say 12.5. And being supercharged, you want it very rich 11 or 12 to keep the charge cool and avoid detonation.
Light load cruising you can go 14 or 15. Stock may go as lean as 15.5 or 16, but stock is NA. Of course light load, you're not boosting anyway.
You are right to start out rich for safety, then slowly start leaning it out while being careful to avoid detonation, hi EGT, etc. Just take your time and log everything. Don't make big jumps, and don't make any change leaner w/o checking for hi temp, knocking, detonating, etc.
Changes in ambient air temp do affect air density, and therefore your tune. THat's why there is an IAT sensor to compensate. Your EMS has an IAT correction table. Now that the intake temps are higher, you can edit the higher temp end of that curve to get the A/F back in line.
03-22-2007, 04:27 PM
#4
Not true. You tune the base fuel maps once and only once for each set of mods. Any further tuning should be done to the correction maps, NOT the base maps.
Tim
Tim
03-22-2007, 06:41 PM
#5
Registered User
Originally Posted by timg' date='Mar 22 2007, 04:27 PM
Not true. You tune the base fuel maps once and only once for each set of mods. Any further tuning should be done to the correction maps, NOT the base maps.
Tim
Tim
Thread
Thread Starter
Forum
Replies
Last Post
Chiung
S2000 Street Encounters
11
12-01-2003 12:09 AM