Can someone please advise on these fuel tables

Talk EMS and Computer related performance

Can someone please advise on these fuel tables

Postby tw2 » Sat Sep 11, 2010 10:05 pm

I am slowly getting ready to take my car to get dyno tuned properly. I would like to get my fuel tables configured and do some low load, low rpm street tuning to get the car reliably mobile first.

I have been reading a few recent EFI tuning books which have helped a lot.
- How do the rpm and load spacings for my AFR and VE tables look?
- Does the target AFR table have appropriate values in it?
I would like to make sure these are as good as they should be before spending a lot of time tuning them.

VE fuel table
Image

Target AFR value table for auto-tune function
Image
Members don't see the above ad. Register now - it's free!
Thomas, JDM 90 185, 06 350z
User avatar
tw2
Established Member
 
Posts: 2909
Joined: Sun Dec 11, 2005 3:01 am
Location: Hamilton, New Zealand

Re: Can someone please advise on these fuel tables

Postby MWP » Sun Sep 12, 2010 6:02 am

Target AFR table looks good.

Not sure about the VE table though.
Really need to get on the dyno to tweak that as every engine is different.
My collection of GT4 documentation: http://gt4.mwp.id.au
Daily: Celica GT4 ST185 (~170kw/atw)
Project: Toyota RA28 '77 Celica (1UZ-FE powered)
Chairman of the SA Classic Celica Club.
MWP
Established Member
 
Posts: 1591
Joined: Mon Jun 01, 2009 11:02 am
Location: Adelaide, South Australia

Re: Can someone please advise on these fuel tables

Postby tw2 » Sun Sep 12, 2010 6:38 am

Thanks, I have changed a couple of things in the AFR table, 15.7 is probably too lean to cruise. I have lowered it to about 15.0-15.2 and changed some other low load areas closer to 14.7.

The VE table numbers themselves are not very accurate and need a lot of futher tuning. It will be thrown on the dyno before too long. Do the rpm and load spacings look ok? I tried to give it a lot of low-mid rpm resolution since this is where things will be changing the most.
Thomas, JDM 90 185, 06 350z
User avatar
tw2
Established Member
 
Posts: 2909
Joined: Sun Dec 11, 2005 3:01 am
Location: Hamilton, New Zealand

Re: Can someone please advise on these fuel tables

Postby Simba » Thu Sep 16, 2010 12:59 am

tw2 wrote:15.7 is probably too lean to cruise.


It's very lean and will lead to bad things happening, especially in a tip-in WOT situation from those AFRs. 15:0-15:2 is safe enough for lean cruise, after that you're risking a lot for a tiny increase in economy.

Lots of fast, loud things.
User avatar
Simba
Established Member
 
Posts: 2896
Joined: Wed Oct 12, 2005 10:17 pm
Location: New York, NY

Re: Can someone please advise on these fuel tables

Postby sleeper » Thu Sep 16, 2010 8:46 am

Looks ok,
Not really shure what ems you have, but i think you have to many load points in the of boost area..
20-40-60-80-100 will do.. no need to have one every 10..
89 ST165: 9.89/144 daily driver during summer. 711AWHP.
sleeper
Club Member
 
Posts: 888
Joined: Mon Aug 23, 2004 7:56 am
Location: Norway

Re: Can someone please advise on these fuel tables

Postby tw2 » Thu Sep 16, 2010 9:26 am

Thanks for the help. It is megasquirt 2 extra. Those load points are vacuum, 100 is 0psi. Boost is 100 to 250kPa.
Thomas, JDM 90 185, 06 350z
User avatar
tw2
Established Member
 
Posts: 2909
Joined: Sun Dec 11, 2005 3:01 am
Location: Hamilton, New Zealand

Re: Can someone please advise on these fuel tables

Postby MWP » Thu Sep 16, 2010 11:12 am

Meh, i lean cruise at 16:1 with no problems.
As long as the engine doesnt ping with rapid throttle increase from cruise, youll be fine.
Going lean for a fraction of a second on transition isnt going to melt a piston.
My collection of GT4 documentation: http://gt4.mwp.id.au
Daily: Celica GT4 ST185 (~170kw/atw)
Project: Toyota RA28 '77 Celica (1UZ-FE powered)
Chairman of the SA Classic Celica Club.
MWP
Established Member
 
Posts: 1591
Joined: Mon Jun 01, 2009 11:02 am
Location: Adelaide, South Australia

Re: Can someone please advise on these fuel tables

Postby Simba » Thu Sep 16, 2010 3:13 pm

MWP wrote:Meh, i lean cruise at 16:1 with no problems.
As long as the engine doesnt ping with rapid throttle increase from cruise, youll be fine.


Frankly, that's a hack of a standard and has no place in a proper EFI tuning discussion. "I do it and it hasn't blown up or melted yet" is generally the sort of advice to be wary of.

$2-3,000 for an engine rebuild buys a lot of gas, and the difference between a 15:1 and a 16:1 cruise is around 1-2 mpg at most. You're stressing the engine and running it much hotter than it needs to be run in order to realize a minuscule fuel savings and range increase. That is a ridiculous thing to suggest anyone replicate.

Lots of fast, loud things.
User avatar
Simba
Established Member
 
Posts: 2896
Joined: Wed Oct 12, 2005 10:17 pm
Location: New York, NY

Re: Can someone please advise on these fuel tables

Postby sleeper » Thu Sep 16, 2010 8:09 pm

Simba wrote:
MWP wrote:Meh, i lean cruise at 16:1 with no problems.
As long as the engine doesnt ping with rapid throttle increase from cruise, youll be fine.


Frankly, that's a hack of a standard and has no place in a proper EFI tuning discussion. "I do it and it hasn't blown up or melted yet" is generally the sort of advice to be wary of.

$2-3,000 for an engine rebuild buys a lot of gas, and the difference between a 15:1 and a 16:1 cruise is around 1-2 mpg at most. You're stressing the engine and running it much hotter than it needs to be run in order to realize a minuscule fuel savings and range increase. That is a ridiculous thing to suggest anyone replicate.



well, combustion temps are not higher at 16:1 than 15:1, they will actually be higher at 15:1 than 16:1... ( exhaust temp normaly is at top at about 14.2afr.. and get`s lower the more you lean it out due to lack of energy... ( fuel)
89 ST165: 9.89/144 daily driver during summer. 711AWHP.
sleeper
Club Member
 
Posts: 888
Joined: Mon Aug 23, 2004 7:56 am
Location: Norway

Re: Can someone please advise on these fuel tables

Postby MWP » Thu Sep 16, 2010 10:10 pm

sleeper wrote:well, combustion temps are not higher at 16:1 than 15:1, they will actually be higher at 15:1 than 16:1... ( exhaust temp normaly is at top at about 14.2afr.. and get`s lower the more you lean it out due to lack of energy... ( fuel)


... this is true.
My collection of GT4 documentation: http://gt4.mwp.id.au
Daily: Celica GT4 ST185 (~170kw/atw)
Project: Toyota RA28 '77 Celica (1UZ-FE powered)
Chairman of the SA Classic Celica Club.
MWP
Established Member
 
Posts: 1591
Joined: Mon Jun 01, 2009 11:02 am
Location: Adelaide, South Australia

Re: Can someone please advise on these fuel tables

Postby ___Scott___ » Fri Sep 17, 2010 2:25 am

NOx formation correlates with combustion temperatures, so in the graph below you can get a general idea of what the combustion temperatures are going to do as a function of AFR by looking at the NOx curve:
Image
Scott
Colorado Springs, CO - USA
SONY
Opera - The better browser
User avatar
___Scott___
Established Member
 
Posts: 2057
Joined: Mon Aug 09, 2004 5:30 pm
Location: - - USA - - Colorado Springs, CO

Re: Can someone please advise on these fuel tables

Postby tw2 » Fri Sep 17, 2010 5:57 am

Exactly, oxides of nitrogen only form in very high temperatures which is why most new cars run 14.7, some running that ALL the time (at a loss of WOT power obviously) to have optimum emissions, and reasonable (ie not the best absolutely possible) economy. Fuel has a cooling effect. The leaner you go the higher the combustion temperature and the more sporadic and non-uniform the burn is. The fewer and further between the fuel molecules are the more the mixture burns in little pockets one at a time = detonation. The question really is how high is safe, I am not going above 15.2. I want to try and get good economy but I also want excellent reliability and margin for error.
Thomas, JDM 90 185, 06 350z
User avatar
tw2
Established Member
 
Posts: 2909
Joined: Sun Dec 11, 2005 3:01 am
Location: Hamilton, New Zealand

Re: Can someone please advise on these fuel tables

Postby Simba » Tue Sep 21, 2010 5:10 pm

sleeper wrote:well, combustion temps are not higher at 16:1 than 15:1, they will actually be higher at 15:1 than 16:1... ( exhaust temp normaly is at top at about 14.2afr.. and get`s lower the more you lean it out due to lack of energy... ( fuel)


The issue I was referring to is not EGT at lean AFR cruise. It's what happens when you transition from a very lean cruise to a tip-in WOT condition. Potentially very bad things.

There are a number of things to consider-- how much cam overlap exists? Is there a cat in the exhaust? What, exactly are the EGT and CHT temps in a particular application? How quickly does the fuel system and EMS in use react to load changes? Those metrics, and many more decide if a given lean cruise AFR is safe. "I do it all the time so it's safe for you" is irresponsible.

Lots of fast, loud things.
User avatar
Simba
Established Member
 
Posts: 2896
Joined: Wed Oct 12, 2005 10:17 pm
Location: New York, NY

Re: Can someone please advise on these fuel tables

Postby MWP » Wed Sep 22, 2010 1:09 pm

So what bad things exactly?
I want to know what can happen that's that bad in the fraction of a second (ie, one or less rpm's) before tps pump enrichment kicks in.
If it's not knocking or getting high egt's, what's going to cause damage?
My collection of GT4 documentation: http://gt4.mwp.id.au
Daily: Celica GT4 ST185 (~170kw/atw)
Project: Toyota RA28 '77 Celica (1UZ-FE powered)
Chairman of the SA Classic Celica Club.
MWP
Established Member
 
Posts: 1591
Joined: Mon Jun 01, 2009 11:02 am
Location: Adelaide, South Australia

Re: Can someone please advise on these fuel tables

Postby cozmic512 » Thu Oct 07, 2010 3:06 pm

I have a few questions here. Is the lean cruise based solely on throttle position?
which translates to load? or is it simply rpm. Im not familiar with the way megasquirt is tuned.
I know you have afr's tuned for each cell based on rpm. what is fuel load %?
because the scale goes up to 250, and that makes no sense to me.
how can you have 250%. sorry about that, I think Im missing something.
regards,
Cory
92 ST185
cozmic512
Club Member
 
Posts: 214
Joined: Fri Jan 28, 2005 4:27 pm
Location: New York, USA

Next

Return to EFI Corner

Who is online

Users browsing this forum: No registered users and 2 guests