TIMING VS EGTs

[TURBOSPYDER]

I have a 99 GST and I was wondering which is more important:
Good Timing or Good EGT's

Heres the situation:

EGTS at 850c with timing rising from 10-16 degrees in the top of third.

OR

EGTS at 890c with timing rising from 3-13 degrees in the top of third.

For info on my set up, go to: http://www.turbospyder.dsmpower.com

Unfortunatly I cant tell which AFC setting makes me go faster. Any info on this subject would help.

Thanks in advance.

 

[allturbo]

I'm no expert, but for the street I generally like to run it safe, ie more timing advance from ecu and lower egts. The 3-13deg of timing you are getting is too low IMO. You would probably see some decent knock values if you could log it. Does one set up feel better than the other? From my experience at the track I ran better at lower boost/higher timing than higher boost/lower timing (107.4mph/17psi/22deg vs 105.8/20psi/16deg). I would tune more for timing when running pump gas. Remember 900C isn't exactly "good EGTs", my car runs like crap at the temp because it's knocking and pulling back timing.

 

[Awdboost]

Your EGT help you tune. Run your car to 820 C on a third gear pull. Your EGT should just got to 820 and stay there. I felt more power when I did that then when I ran hotter. You want high timing too.. You also want to tune for Timing. The higher the more power, untill you start to get past 25 degree of advance. A normal street pull should be about 20-21 on pump gas. and 23 is were you want to be at. Timming is very important it make your power. When you get very hot EGT is because 1. timing is being pulled, or if your running too lean your start to melt or over heat your piston. Every one thinks the 1 cylinder is the hotest but they are wrong. It's number 2. As proof were is you knock senser located? number 2.

 

[2-0turbo]

The problem is they are closely related. As you see knock, your timing is retarded. Retarded timing = late combustion which means you are dumping fuel out of the cylinder before it is completely burned. EGT's go through the roof, even though the cylinder temps are quite low. If you have good timing AND high EGT's, then you need to add some fuel. Bad timing and high EGT's might mean you need to turn your boost down.

I rarely get 820C on the street--I just can't get on the gas that long. On the track this weekend (road course), I was pegging 940C at the end of the straights. This forced me to get off the throttle 2/3 of the way down the straight. Between runs, I turned the boost down 3 PSI and added first 4%, the a total of 7% more fuel in the upper RPM bands to try and cool things down. It worked, and I would just see the warning light come on at the end of the straight (900C). I was really stretching 4th at the end of the straight, so I started shifting to 5th to lower the RPMs a bit and help keep EGT's a bit lower.

 

[TURBOSPYDER]

I guess Ill be playing around the settings a bit. This is probably one of the toughest things I ve experienced. TUnning is hard if you dont really know what your doing.

 

[Awdboost]

Originally posted by 2-0turbo
I rarely get 820C on the street--I just can't get on the gas that long. On the track this weekend (road course), I was pegging 940C at the end of the straights. This forced me to get off the throttle 2/3 of the way down the straight. Between runs, I turned the boost down 3 PSI and added first 4%, the a total of 7% more fuel in the upper RPM bands to try and cool things down. It worked, and I would just see the warning light come on at the end of the straight (900C). I was really stretching 4th at the end of the straight, so I started shifting to 5th to lower the RPMs a bit and help keep EGT's a bit lower.

Hey Put more fuel in.. I wouldn't be running that lean. I bet your getting lots of burn marks on your piston, if not you will be melting soon. I don't recommed going over 900.

 

[2-0turbo]

Originally posted by Awdboost

Hey Put more fuel in.. I wouldn't be running that lean. I bet your getting lots of burn marks on your piston, if not you will be melting soon. I don't recommed going over 900.

I know it is too hot--my warning comes on at 900C. I did put more fuel in (see post), and the temps came down. I doubt my pistons are burned--stuff like that doesn't happen instantly. Can you put your hand in a 500F oven for 10 or 15 seconds? Does your hand get anywhere close to 500F?

At the present time, I really cannot put anymore fuel in. I am hitting pretty high duty cycles (mid 90's) on the stock 450's with the FP already at 43 psi. 660 injectors are on the list.

 

[Taboo]

Originally posted by Awdboost
Your EGT help you tune. Run your car to 820 C on a third gear pull. Your EGT should just got to 820 and stay there. I felt more power when I did that then when I ran hotter. You want high timing too.. You also want to tune for Timing. The higher the more power, untill you start to get past 25 degree of advance. A normal street pull should be about 20-21 on pump gas. and 23 is were you want to be at. Timming is very important it make your power. When you get very hot EGT is because 1. timing is being pulled, or if your running too lean your start to melt or over heat your piston. Every one thinks the 1 cylinder is the hotest but they are wrong. It's number 2. As proof were is you knock senser located? number 2.

Running well above 20' of timing advance results in the cyilinder pressure going through the roof (and chancing blowing the head gasket) with very minimal HP gains. The more you advance the timing, the more beating the piston pins, rod and main beaings take, resulting in premature wear and/or bearing failure. More HP is always achieved with fairly conservative timing (18-20') and higher boost level than with lower boost level and more timing advance (since the volume of air one can add fuel to affects the HP output much more than igniting less A/F mixture a few degrees of the crank revolution sooner).

A/F ratio will determinate EGT, but it's very common misconception to believe that the leaner the A/F ratio, the higher the EGT. Peak EGT occurs at stoichiometry - 14.7:1. If one is "on the wrong side of the hill" and runs leaner than 14.7:1, the EGT will actually go down when the A/F mixture gets even leaner. That's one of the reason why one should always start on the rich side. Our engines produce maximum HP at 12.6:1, but 12.2-12.4:1 leaves some safety margin for error. When tuning, start at very low boost level (to eliminate knock and consequently timing retard) and set the A/F ratio and timing advance first. These two variables should not change (with good 1:1 AFPR) even when raising the boost level 'til enough knock to trigger the ECU is realized.

The #1 cylinder actually tends to run hotest, we tested it (and tapped the #1 and #2 runners of the EM the exact same distance from the head, ran the same - Team RIP - probe and the same gauge without changing any other settings). The reason might be the #1 cylinder and combustion chamber being constantly surrounded by the hotest coolant or fuel pressure drop within the fuel rail - especially on cars running stock fuel pump, injectors and high boost level. The knock sensor is placed on the #2 cylinder so it can evenly monitor knock occuring in ALL cylinders (not just #2) with the #1 and #2 cylinder priority. If placed on #1, the knock sensor might not detect knock in #4 in reliable manner.

 

[wira4]

What is the O2 sensor in mV at AFR=12.3:1 ?

Currently I am experiencing this problem:-engine misfires at 7200rpm at 23psi boost but EGT=1500F b4 misfire and spikes to 1600F during misfire and O2=0.82mV?? and timing at 18 ADV. Not using knock detection anymore. These are on 720cc inj at 86%DC using 97RON PF.

Thanks

Wira4

 

[RocketBoy]

It's pretty hard to say what AFR is equal to 12.3:1 using a stock oxygen sensor. The stock oxygen sensor can not be used for reliable data only a wideband o2 can (used at dyno). It seems like most people tune their o2's to .92-.96.