With the cold air where I live during this time of the year, I think I am maxing out injectors on my GM stage 2 kit. The other day when ambient temps were in the teens there was an audiable change in the noise of the engine above 6400rpm. With the aeroforce I measured 16psi on the 3.07in pulley. Considering the AFR is in the mid to high 10s (Rich GM Tune) does this sound probable, I will be getting a tune soon hopefully.

A video is here: https://drive.google.com/file/d/0B4G...ew?usp=sharing

Forgive the honks, my buddy with a cobalt ss/sc wanted to run, hes stock so you cant see him in the vid. Lol

 

Very possible that it hit 100% IDC at 16psi on stage kit injectors, but since the A/F is so rich it won't matter. If it was tuned to a more sensible A/F it wouldn't be at 100% on normal stage 2 boost.

 

Yeah, im thinking its mostly because of the cold weather, because 16psi is high for a 3.07in pulley. I usually only hit about 14-14.5psi in the summer when the air is less dense. If i get a good tune on a 2.9in I will either switch back to gm pulley in the colder months or just remember to shift earlier.

 

beating on your car when its in the teens is foolish and asking for your engine to pop

 

I always make sure everything is warmed up before I ever run it fast in cold weather, usually won't do runs below freezing but my friend wanted to see the difference between stock and stage 2.

 

Hmmmm wonder where that saying comes from, great turbo/blower weather............ But yet around here anyone says anything about going wot in cold temps and everyone thinks the motor will go boom. Not seeing where it will go boom if the tune is correct and the engine is fully warmed up.

 

Edit

Those stock timing adder tables based on iat like to add a lot of timing at the coldest temps. most people zero out these portions so that your not adding a bunch of timing in the cold, but it doesnt typically cause issues for those with a stock or gms2 tune because they run so rich.

 

Very good info southal thank you for that.
This is why I am tuning right now for a winter tune and will readjust this spring when it warms up.

 

I dont see why it wouldnt be accounting for the colder air since the iat is part of the maf. It should be able to calculate air density from that.

 

It does have a thermistor that provides the iat1 and uses it for ve calculations and possibly even some fueling calculations, but we dont have access to it in hptuners. May not need it either though, because the relationship between air density and temperature gauge air inlet temp doesnt change.

After a bit of research though, it seems gm mafs actually can account for mass variations due to temp fluctuations and provide a real mass value instead of just flow as some of the older mafs tended to do. So i was wrong.

Im still a bit skeptical that it is always accurate though. Extreme hot and cold temps can really screw with electronic measuring devices.

 

keep in mind that our cars, like any other modern car, are designed to sell at any place in north america. they have the be set up so they can run in the desert in vegas and that same car can be driven up to northern canada and still run fine. gm had to be able to warranty the car no matter where it went. aside from california, the stock tunes are all the same regardless of location.

my point is, the pcm has to be able to compensate for hot and cold, high and low altitude. when tuned, sure, the tuner may not be able to access all the tables that help with temp related conditions, however it doesnt mean that they need tweaking, and that they arent still doing their job. however, like any tuned car, you should be keeping an eye on things all the time. im always watching for knock and keeping an eye on my afr. i find very little variance in afr between summer and winter. if anything, i find it actually tends to run a little richer below freezing, and that tells me the pcm is compensating for the colder air temps, like gm intended it to.

i typically dont beat on my car in the freezing cold though, cause where i am we tend to have black ice a lot. and what fun is beating on a car on snow tires?

 

Youre right sharkey. I have never thought or worried too much about the cold, because it rarely gets below freezing where im at.

 

Read the IDC and you will know. I was hitting 140%+ IDC on the GM stage 2 tune on the GM stage 2 pulley.

 

I've never hit anywhere near that high on my GMPP 42's. That's nuts.

Most of my harder testing I put my car through is when it's in the mid 30's - low 40's.

That's about as cold as my car ever see's anyways, lol.

 

it has nothing to do with warming up your car

the saying is true to a point these cars do not do well with big swing in temps I have seen when they hit p.e. run as much as 1 to 2 points leaner in the winter @ wot remember the o2 is not used in wide open throttle

 

I can understand that if the car was tuned in the summertime and then the temps cool off. It seems like a winter tune and a summer tune is a good idea!

Already seeing this myself since I had wot set at 11.6-7 on the top end, and last night on the way home was hitting down into 11.2 just with it being 10 degrees warmer.

 

Any way I can get it to not run rich on gms2?

 

Yes.... lean out the AFR a bit.

You will get a little extra headroom with the injector pw with the leaner afr, as it won't be commanding so much fuel.

GMS2 was designed to run rich to cater to all sorts of different climates, elevations, locations, etc. Lean it out, watch for KR, and adjust accordingly.

 

What staged said. If you have access to hptuners, just disable cat over temp fueling corrections for pe, lean out the pe enrichment ratio to 11.5ish on the safe side, use a wideband to get your maf calibrated and watch for knock retard. If you get knock, either drop a degree of timing or so in the wot section of the table and make sure it has smooth transitions. Thats all i did on gms2.

Im not sure if cat overtemp is actually meant to prolong the life of a catalytic converter or not. My car was always catless when i disabled it

 

I don't have a log so I have to get a snapshot of RPM and Pulse Width on my Aeroforce, haha, so yeah I checked and in below freezing temps it did hit almost 110% on the 3.07in Pulley. Not Good!

Was alot warrmer today ~50'F and I hit about 95% at worst out of all my runs. Mostly about 90%.
Wideband AFR is still reading in the 10s either way so atleast no dangerous lean spikes, my STFT are decent (Below +/-5% on highway cruise) for a GM canned tune so my MAF calibration is surprisingly not horrible for never being tuned.

I will probably be going 60lbs Injectors and a 2.8in Pulley here in a little while and have it tuned in for 93 octane at 11.5:1 or so, looking for +20whp... we will see.

 

It definitely scares me how many people run 2.9s year round on GM Stage 2 Tune. I could see you getting by in above 70'F ambeint but definitely not when its cold, I am having trouble with the 3.07 lol.

 

As long as your Air Fuel stays good, I wouldn't get too excited about IDC going past 100%.
It's a calculated number.

I see mine go to 110% frequently on my turbo LS during a pass. AF stays rock solid.

 

exactly!

 

If you can get a HP Tuners cable then PM me. I will tune you.

 

I don't however I am in touch with a local tuner thats going to get me setup on some 60lbers and a 2.8 here in a month or so.