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RPM surge at start?

Sabrewings

Sabrewings

New member
I recently finished my base file for me to start tuning with. It included mostly transmission changes with a few basic engine changes as guided by WebRacin's tuner guide.

Now, whenever I start my car the RPMs surge a few times before it settles where it should be. It was much worse the first few times I started, but it still does it to a small degree more than it did with the stock file.

I haven't yet gone back to the stock file, but I think I might this weekend to see if that cures it. Anyone else seen this or know how to fix it?
 


check your timing and your IAC....it could either be your startup AFR being off because weather is getting warmer or it could be that you may have to mess with the timing at startup a bit. It's probably about time to start on a good summer tune though.
 
I didn't mess with the timing at all nor the fueling. Only what was in WebRacin's tuner guide at setting up a base file (even then, I hadn't done his spark adjustments yet).
 
Throw the stock file back on and see what happens. If it quites then I would compare the stock file to the new one you created and see if you can find the problem.
 
In a controlled test, I started the car. RPMs surged some, like I've been noticing, and I let it idle normally for a couple minutes. Shut down.

Flash stock bin. Restart car. RPMs are dead on perfect as soon as it started, just like it should be.

Flash back to my tuned bin. Start car, still the surge. I've had to start it again since and it nearly died out (dropped to ~500RPMs, then surged to 1200, then started to settle, but still kept wavering for about 10 seconds).

Can someone look over my two bins? I've been looking at the stuff I changed and can't think of what would cause this. The zip file size is larger than the forum will allow, so I'm not sure an easy way to distribute it for someone to look over besides e-mail.

For reference, I made the changes suggested by WebRacin in his 1.0.9 tuner guide with some suggestions from Will for the 04+ transmission stuff.
 


Okay, I was looking through the changes again and came across this:

Fuel/PE/Open Loop Base AF by Coolant Temp: Modify all between 86 and 158 deg to 11.7, then go back and modify all between 176 and 212 deg to 11.6.
Click to expand...

I did notice that the car smelled very rich at start up. I think this may be my answer. I'm going to go back to stock in that table. If that fixes it, maybe I can find more reasonable settings as I may be nearly flooding it during start.

Any reason this table is like this? Some pointers with it?

Edit: Never mind, that's PE mode. Way off base. To help everyone out, here's all the changes made in the fuel folder...

Fuel/AE/AE_TPS_Re-Allow: Set to 30 (This is the value the TPS must be below to allow AE mode. Since we will be changing the PE to 30%, we don’t want AE active when PE is engaged.
Fuel/AE/AE_MPH_Modifier: Change all values to 1.
Fuel/AE/AE_Enrichment: Change all values by 108%. Now I like my tables with a clean look, so I only have 2 decimal places. I delete everything after the 2nd decimal place, but this is personal preference.
Fuel/Fuel Injector/Injector_Flow_Rate: Import the file needed for your setup. If you are stock, leave it stock. If you have 42.5 then import that file.
Fuel/Fuel Injector/Injector_Skew_Percent: If you have checked your plugs and have a skew % already, use that value. If not set 3 and 4 to 100% and 1,2,5 & 6 to 96%. The idea here is that since 3 and 4 are in the middle of the engine and are the pistons that crack more often it could be due to higher cylinder temps since they have more surface area bordering other cylinders than the other cylinders. You should check your plugs and set this according to what the plugs show and not use a generic figure.
Fuel/MAF/MAF_Airflow_Table: If your stock, leave it stock, if you have an aftermarket, import the appropriate file.
Fuel/PE/Open Loop Base AF by Coolant Temp: Modify all between 86 and 158 deg to 11.7, then go back and modify all between 176 and 212 deg to 11.6.
Fuel/PE/Base_PE_A/F: Modify all between 86 and 158 deg to 11.7, then go back and modify all between 176 and 212 deg to 11.6.
Fuel/PE/PE_Enable_TPS: Set all to 30% TPS to enable PE
Fuel/Torque Mgmt/Torque_Abuse_A/F: Set this to 11.6
Fuel/Torque Mgmt/Torque_Abuse_Differential_Score: Set this to 11.6
Fuel/Torque Mgmt/Traction_Control_Desired_A/F: Set all to 11.6
Fuel/Torque Mgmt/Torque_Abuse_Drive_Injector_Disable: Set to 0 (we never want injectors to shut off)
Fuel/Torque Mgmt/Torque_Differential_Score_Injector_Disable: Set to 0
Fuel/Torque Mgmt/Traction_Disable_Injectors: Set all to 0
For the High MPH, I set the numbers for a natural progression. Even though we will never hit 252 mph, I want no complications later on down the road.
Fuel/Torque Mgmt/Disable_All_Injectors_High_MPH: Set all High to 255. Set all Low to 254.
Fuel/Torque Mgmt/Disable_1_Injector_High_MPH: Set to 252.
Fuel/Torque Mgmt/Diable_2_Injectors_High_MPH: Set to 253.
Fuel/Torque Mgmt/High_RPM_Fuel_Cutoff: Set High to 6250. Set Low to 6249.
Click to expand...
 
Last edited:
I fixed it. It WAS the PE base AF table like I originally thought. On a whim I reset it back to stock and it's just fine with no other changes. Guess I'll tweak it a bit rich, but not that rich.

It was nothing more than a hunch. The really rich exhaust was a clue.

Anyone got any more input on how that table SHOULD be set? No offense to WebRacin', but that wasn't working for me. :(
 
I would have to look at that file on my pt (which I don't have because I am at work) but I suppose that when you started your car it was in open loop and surged. Then when it went into closed loop it settled down because it was running a 14.7 afr in closed loop.
 


Open loop when it first starts, and during WOT. Closed loop at idle, cruise, and moderate acceleration (I think, still new to this).
 
I would assume that the pcm doesn't use the base open loop file while you are in PE so I don't see why it couldn't be set to stock?
 
Yeah, I wasn't sure about that either. I understand why the A/F ratios during traction control and stuff you'd want rich (to avoid popping a piston), but I could smell the gas from my car starting up with the table how it was.
 


BTW mine is set to 11.7. I don't see why you couldn't have it set to stock. No need to be pumping in all that extra fuel. I guess if you set it to stock and see knock somewhere try setting it back to 11.7 and see if the knock goes away? Maybe someone with more knowledge than me (other than you ;)) will post and let us know what is up with this table.
 
Sabrewings said:
Open loop when it first starts, and during WOT. Closed loop at idle, cruise, and moderate acceleration (I think, still new to this).
Click to expand...

I think you have it backwards...I my self could be wrong though
 
I am pretty sure closed loop is anytime the pcm is fueling off of the O2 sensor. Becuase if you look at closed loop afr it is 14.7. So I believe Sabrewings is correct.
 
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