3rd gear pull, timing low, plz help

[JoeyGST]

I just datalogged my car and found that it's getting very poor timing.

Between 4000RPM and 5400RPM, my timing drops down a lot, going
to 7 degrees at the lowest point. Generally, I'm told that I should
increase fuel on the S-AFC at the point that timing is being pulled.
However, my O2 was at .94 to .98 during that range, so it's already
running rich.

What else can I do to prevent the timing from being pulled so much?
I still have the stock sidemount on the car, is getting an upgraded IC
the only solution? Or can I try something else first?

Car: 99 GST
Mods: Big16G, 550cc inj, 190walbro, 2.5" full exhaust, S-AFC, boost
control, Injen intake

 

[1LE]

Well, first of all I highly recommend that you ignore the A/F... It's not terribly reliable to begin with and especially so on 2g's. At .92 my car was blowing big clouds of fuel smoke! Mine now (new sensor now and new FPR) reads .85 at the setting that gives me the best timing. I still am rich enough that I leave a small bit of fuel smoke... BUT, if I pull the fuel back to make it run cleaner, my timing holds... IMHO, tune by timing and watch your EGT just to make sure you don't really screw up The A/F has been completely useless for me!

 

[TrustGs-R]

wats up joey.

What logger are you using? What's your timing at 7000 rpms? It sounds like your ECU is seeing a lot of knock and pulling a ton of timing. Get a good logger and see what's really going on buddy.

 

[webbdog]

Originally posted by TrustGs-R
wats up joey.

What logger are you using? What's your timing at 7000 rpms? It sounds like your ECU is seeing a lot of knock and pulling a ton of timing. Get a good logger and see what's really going on buddy.

I think he already has a datalogger.

You're stock sidemount could be your problem, depending on the outside temps and how much boost you're running (which is always a good excuse to get a front mount). My advice would be to turn the boost down to 13-14psi and get it tuned well there (no knock, good advance). Then increase your boost a little and tune it again. Keep doing this until you reach a boost level where you can't increase the fuel enough to combat knock. My guess you'll only be able to get away with 15-17 psi on the stock sidemount.

Oh, and test for boost leaks as well. They can have a bad effect on tuning as well.

 

[JoeyGST]

TrustGSR: I have a pocketlogger, and my timing is good at 7000RPM.
It just dips real low around 4000-5500RPM range. I was thinking
knock too, and since I'm already running rich at that range, I was
asking if there was anything else I could do besides upgrading
intercoolers to prevent knock.

Webbdog: Good advice, I'll give it a try running at 15psi. I don't think
there is much difference though. I'm running 17psi currently.

I don't want a FMIC, because I had one previously and it overheated
my car. If necessary, I'll probably just get a big SMIC. I'd just like to
try and get some good timing before having to upgrade.

-JoeyGST

 

[TrustGs-R]

Joey,

you got rid of your biggie greddy fmic rite? It was overheating your car as i recall (don't worry it did the same on my gsx when i had one...).

Ya. That sounds like similar behavior to what I used to see when i first started logging/tuning my dsmlink. Knock retard would come on 5-6 degrees in the mid range and usually by the high end It'd come down enough to give me decent timing (12 or so @ 7500 rpms).

Currently at 19psi I'm seeing the full stock timing advance from 5500 rpms + and I have minimal/no knock retard throughout the band (unless it's like 100 degrees outside again and i'm WOT'ing 5th gear) haha. This is on stock pump gas.

My learned lesson from tuning: 2g's like to knock on pump gas and the ecu will aggressively pull timing to save your motor. Once the knock is gone, the ECU slowly gives timing back, so by the time you're at redline your timing might still be pretty low. The best thing to do is pull timing (or boost if you want) so you don't knock in the first place. Or you can get that 100 octane fuel from 76 if you want to go that route.