Transient Fuel - Warmup vs. Impact Factor

[Aaron407]

I'm wondering if anyone can shed some light on this for me since transient fuel perfection seems to be a bit like chasing a unicorn.

In general, I'm wondering when the warmup transient tables are used and how they transition or overlap the normal impact factor/evaporation tables. My normal engine temperature transients are tuned fairly well, but I'm still getting a lean tip-in after a cold start until the engine gets close to normal operating temperature. As such, I'm trying to determine whether I should focus on the warmup transient table, normal impact factor table at the colder temperatures, or both.

For example:

1) Are the main warmup transient table values used as adders on top of the normal impact factor values, or are they active instead of the impact factor tables up to a certain transition point? If they are used separately, what is the transition point? Initiation of closed loop operation?
2) For my car, the impact factor table uses MAP kpa as one criteria and intake valve temperature as the other. However, the warmup transient table has undefined units instead of kpa, and the range runs from 0-80 rather than the 0-100 shown in the impact factor table. Can anyone tell me what the units are for the warmup table?

I don't currently have VCM suite in front of me to be able to verify some items, so I might be a bit ambiguous in my statements. However, if anyone has some thoughts on the matter, please let me know. Thanks in advance!

EDIT: car is a 2009 Pontiac G8 GT

[BigDaddyCool]

I'm wondering if anyone can shed some light on this for me since transient fuel perfection seems to be a bit like chasing a unicorn.

In general, I'm wondering when the warmup transient tables are used and how they transition or overlap the normal impact factor/evaporation tables. My normal engine temperature transients are tuned fairly well, but I'm still getting a lean tip-in after a cold start until the engine gets close to normal operating temperature. As such, I'm trying to determine whether I should focus on the warmup transient table, normal impact factor table at the colder temperatures, or both.

For example:

1) Are the main warmup transient table values used as adders on top of the normal impact factor values, or are they active instead of the impact factor tables up to a certain transition point? If they are used separately, what is the transition point? Initiation of closed loop operation?
2) For my car, the impact factor table uses MAP kpa as one criteria and intake valve temperature as the other. However, the warmup transient table has undefined units instead of kpa, and the range runs from 0-80 rather than the 0-100 shown in the impact factor table. Can anyone tell me what the units are for the warmup table?

I don't currently have VCM suite in front of me to be able to verify some items, so I might be a bit ambiguous in my statements. However, if anyone has some thoughts on the matter, please let me know. Thanks in advance!

EDIT: car is a 2009 Pontiac G8 GT

Add exactly 1% to the warm up table.... the lean stumble should go away...... Alot of times its caused by either closed loop or the open loop EQ ratio table being out.......... but by adding 1% to the warm up transient table it normally helps fix this....

[Aaron407]

Thanks for the reply. Unfortunately, I've already tried adding 1%, 5%, 10%, and more, and it didn't seem to clean things up much. To confirm, though, how long is the warmup table used, and is it used in conjunction with the impact factor table (e.g. added to)? Since the impact factor table has intake valve temperatures that run the full range, I'm wondering what the need for the warmup table is. I have had some success at the cold temperatures by adjusting the corresponding impact factor table values, but I want to ensure that I'm adjusting things in the right place.

Also, I really should have noted that the car is supercharged with a roots blower (TVS 1900) with a 2.8" pulley, LS9 53 lb injectors, and 1-7/8" long tube headers and running MAF only. From tuning my normal transient fuel, it seems that the supercharger really throws things out in terms of transients. My apologies for neglecting to note this major variable.

[BigDaddyCool]

Thanks for the reply. Unfortunately, I've already tried adding 1%, 5%, 10%, and more, and it didn't seem to clean things up much. To confirm, though, how long is the warmup table used, and is it used in conjunction with the impact factor table (e.g. added to)? Since the impact factor table has intake valve temperatures that run the full range, I'm wondering what the need for the warmup table is. I have had some success at the cold temperatures by adjusting the corresponding impact factor table values, but I want to ensure that I'm adjusting things in the right place.

Also, I really should have noted that the car is supercharged with a roots blower (TVS 1900) with a 2.8" pulley, LS9 53 lb injectors, and 1-7/8" long tube headers and running MAF only. From tuning my normal transient fuel, it seems that the supercharger really throws things out in terms of transients. My apologies for neglecting to note this major variable.

lol yeh bit of a big thing to forget to mention. Setup the car in open loop.......... do a cold start and monitor the AFR vs IVT temps

Look at the IVT vs GAS Table..... modify that or essentially just add a crapload (10-50%) to the cold area of the normal transient table......

[10_SS]

I also had lean tip in on cold start on a Whippled Camaro LS3 so you may want to compare a ZL1 file to your stock file, on my 2010 M6 LS3, most of the transient tables were 0'd. the ZL1 populated them and seems to be a great start, no more lean tip in during warm up.. haven't changed them much... and when I do, I get weird results, like Transient fuel being added in the middle of a WOT run.. lol

[schpenxel]

Transient fueling is a bastard to get right. That's all I have to offer, lol.

[Aaron407]

Thanks guys, and yes, transient fuel is definitely a pain. I have had some success getting things working and I can see the IPW's blip a bit when I stab at the throttle, but I don't want to blindly add too much, especially in areas that might cause problems when it gets much (much!) colder here in Saskatchewan. I'll take a look at a ZL1 file and compare the tables to where mine are right now. I was using a CTS-V file as a reference previously, but it had most of the transient tables zeroed out as well.

Thanks again.

[schpenxel]

I've read all kinds of conflicting data on how transient fueling works on stock setups. One post I saw from I think it was Chris@HPT said that the stock setup depends on the MAF values for transient fueling calcs to work correctly based on the stock transient fuel tables.. so running SD screws that all up. Another post in the same thread said that dynamic airflow #'s are used and it didn't matter if the MAF was working or not. So.. lots of bits of info, not much of it is any good though.

There's a thread on one of the truck forums where someone did a good job of posting screenshots of all the different types of transient fueling issues and how they look.. i.e., sharp spikes vs. long drawn out ones, etc. and what to change to fix each one. It wasn't the best laid out info in the world but was probably the best I've found. If I can find it again I'll post the link.

Personally I'd just try to get it where it goes slightly rich on tip in and call it good. I've never been able to get it right everywhere and would rather it go a little rich than lean

[Niemer]

Take a look through this, fixed my cold start problems.

http://www.hptuners.com/forum/showth...F-only-is-fine

[Aaron407]

Thanks. However, that looks to be related primarily to VE tunes rather than MAF. Overall, though, I am making some progress. I have it so most positive throttle transitions during warmup are putting it slightly rich (e.g. 13.8:1 AFR) mostly by adjusting a combination of the warmup table and impact factor table. I get the feeling that the warmup table is effectively used as a scaler table against the impact factor table, but I could be wrong. At any rate, the only throttle transitions that are left running lean are when I snap the throttle from a dead idle. It might relate to the scaler table that modifies according to airflow, so I'm going to try adjusting that a bit.

In terms of using the ZL1 tables, I checked them out, but they are wildly different compared to what my car used stock. I don't know if I'll try that route unless I just can't get things dialed in elsewhere. All in all, though, things are improving, and I no longer have the stutter that I had before. The only indication that it's still leaning a bit is the wideband signal, so that's some improvement.