Need help with safc and egt's

[Randy87T]

Can't seem to get my egt's up past 650C in elbow (calculated 1300F preturbo) . Would like to get egt's to about 845C in elbow (calculated 1550F preturbo) Have been playing with the fuel pressure and safc settings but not sure just how far to go. Running 16lbs psi boost and 91 octane (all they have around here unless I go to 110). Running 43 psi fuel pressure.

How much fuel should I take out with s-afc?
Could o2 sensor be giving me problems?


K&N, lex afm, full bore custom 3" elbow
3" exhaust, no cats, Walbro GSS341,
afpr, 550's, avcr,safc, dual pod with
Greddy peak and hold egt and boost gauges,
JBL custom intercoolers and stock ct-26.

Any help would be greatly appreciated.
RandyM
87T

[ZaZZn]

Hey randy sorry I dind't get back to you I don't have you're number!!

Anyhow.. You're egt's sound migty low.. I'd recheck to see if the EGT was installed properly...

My problem with my egts is I can't get below 1500!!! Even when I'm just crusing i'm having some nasty numbers! I've even hit 1600!!

I think I may have a injector that went on me.. but We'll see soon..

Anyhow..

The best way to tune with afc is to remove 1-2% take a run and watch you're air fuel..

Take another run watch you're EGT's see how they fair however, the absolute best way would be to go to a DYNO and use the wideband to tune. The way I've been tuning has been to watch the EGT's and A/F gagues and adjust accordingly. However, I have not done much tuning since I have some crazy egt numbers.

[SupraKirk]

Originally posted by Randy87T
Can't seem to get my egt's up past 650C in elbow (calculated 1300F preturbo) .

When you say 'elbow' do you mean the O2 housing (post-turbo) or Downpipe (post-turbo) or actually before the turbo (because you are saying pre-turbo)? There is a discrepancy between readings pre and and post-turbo.

[Randy87T]

To get preturbo temp need to add about 100 F to the post turbo temp which in my case the probe is located in the turbo elbow. I gave both readings so that those that only had gauges and probes located preturbo and read fahrenheit would be able to help me.

650 centigrade post turbo = 1202 fahrenheit post turbo

1202 F post turbo + 100 F = 1300 F preturbo

My comment was right on unless the equation changed somewhere along the line. If so then let me know.

[Randy87T]

The basic question is what percentage of fuel is to be taken out (for those of you that have similar upgrades) using the safc to get my egt's up to 1550 F preturbo? 10%, 20% ?? I am not sure how far to go and don't want to screw up my new rebuild. Someone out there has to know. Please help.

[drjonez]

bad news man, you CANNOT just add #s to translate from pre to post turbo. there is no way to accurately tell how much heat (energy) the turbo is removing from the exahust stream. goto mkiv.com and read the writeup on the two egt guages....it will be an eye opener. the egt pre-turbo is a fair tuning tool, post turbo it is more useless than an autometer a/f guage.....

[SupraKirk]

Originally posted by Randy87T
To get preturbo temp need to add about 100 F to the post turbo temp which in my case the probe is located in the turbo elbow. I gave both readings so that those that only had gauges and probes located preturbo and read fahrenheit would be able to help me.

650 centigrade post turbo = 1202 fahrenheit post turbo

1202 F post turbo + 100 F = 1300 F preturbo

My comment was right on unless the equation changed somewhere along the line. If so then let me know.

Yeah Drjonez is referring to the same article that I was going to point you to once I was sure what you were talking about. Additionally you posted:

Would like to get egt's to about 845C in elbow (calculated 1550F preturbo)
which by your above stated calculation is incorrect (it would be 1650F), and why I asked for the clarification.

[ASL MKIII]

[however, the absolute best way would be to go to a DYNO and use the wideband to tune. The way I've been tuning has been to watch the EGT's and A/F gagues and adjust accordingly. However, I have not done much tuning since I have some crazy egt numbers. [/B]

zazzn2002 hit the nail on the head! Take your car to a dyno shop that has a wideband 02 and data acquisition and tune the thing based on your A/F. That is the absolute best and safest way to tune your car.
I'll bet the title to my car that you pick up some torque and hp also!!!
(just kidding about my car):)

[dbsupra]

i agree w/ above. all cars are diff, esp ones that are 10+ yrs old.

also to mention- just because the egt's are low does NOT mean u are running rich. running too lean will cause low egt's as well. the egt's are cooler running rich because the excess fuel is cooling it down. the egt's can also show cool running lean because the excess air is cooling it down.

good luck-

Dave

[Randy87T]

I have checked the spark plugs and they are more of a dark brown color rather than a tan. Isn't this indicating that the engine is running rich? If so then can I lean it out some more?
Thanks
Randy

[ZaZZn]

Randy.. BTW it's Eric from Toronto...

Anyhow what you want to do if you don't want to pay the money for a dyno is to watch 2 things.

#1 the EGT's at turbo elbow should not exceed 1450 C according to Reg Reamer.....

#2 A/F meter even though it's not accurate and under WOT you're in a closed loop it gives you a general idea whats going on. I watch to make sure I'm in the green when WOT and also make sure that my egts never pass 1550 (i'm on the turbo inlet)

Although I have hit 1600 some times (not quite sure why yet) I let go of the throttle right away.


What you're going to need to do it tune carfully. A EGT is slow to respond about 1-2 second delay so you could be running LEAN at a specific RPM point. However, you could be pig rich at another RPM.

What I suggest for now since you seem to be pig rich acorss the board is get on the highway go WOT in 4th and 5th let them ride out so you create max heat.. Take note of the number you get.

Then start removing fuel slowly till you hit about 1400 EGT's Take out the same amount acorss the board ie 1% on all rpm ranges. Keep doing this until you reach that number.

I would not try to aim for 1450 due to the fact you maybe running very lean at a specific rpm range... Best thing to do is get a base line to tune from.. IE go to the dyno get on the wideband set it perfectly then as you start to add more boost ect adjust the fuel accordingly ie if i run 1 psi more I would prob add 1% across after I tuned from 12:1. Reasion is to ensure I dont run lean.

Running lean kills moters.. Running rich doesn't really do too much harm at all unless running very rich. In which case can bulid up carbon in the cly's that later may cause detonation.

Also as a side not make sure that you remember that going TOO lean can sometimes produce LOWER egt numbers. So thats why I say keep a eye on the A/F gague.



Hope this helped..

Damn I actually wrote more then a 1 line answer... Whoohoo for me. :eek:

[Randy87T]

Thanks for the help everyone. From the info that I gathered I will be moving the egt probe to the preturbo side, installing new plugs and wires, getting an a/f gauge installed and testing my o2 sensor. Eric you answer was very informative. Will let everyone know how this turns out when I am done.
Thanks again
Randy
87T

[ZaZZn]

Np glad i could help