i was just wondering if a cam change in the L61 will effect the computer at all and if the comp cams on gravanas web site and the ones that jbody have are the same

 

I emailed Turbo Tech about these cams a little over a month ago, They told me that the stage one cams can be run without computer mods. I also asked them about the stage 2 cams, they recomended me not to use these cams unless i planned on running a stand alone system. stage 1 good for 8 to 12hp.

 

Does anybody know if Stage 1 cams are ok for daily driving? Is there anything else you need to get after installing the cams?

 

They should be okay for daily driving, its not like the lift or duration will be anything unheard of for a 4cylinder or anything. Im guessing they have close to stock cam profiles with a slight bit more aggressive lift.

 

gravanas is stage 3 cams (sais right there) so def. would need computer tuning.

 

even if they say tunning not needed, it still should be done. its always best to be safe, thats y im waiting for better tuning for my car.

 

exactly. regardless of what a manufacturer tells you, unless you have tuning done, you will not extract complete potential form switching cam profiles. it may run "decent" but it would run better when tuned right. if it's a grind that you can run on the stock ecu with no tuning, chances are it's so mild it wasn't worth the time to put it in.

 

Stage 1 works with no computer mods, and is fine as a daily driver. We have a special on these (stage 1 and turbo cams, in stock) for only $399.99. We are only offering this price for 2 more sets of each stage, email us soon for a discount code.

 

wut kinda gains on stage 1

 

6-10 hp. 10 being tuned

 

i always see it this way....cams will add more air into each cylinder, but the computer still senses the same amount of air (since it wouldnt know about the new cams), so wont add any additional fuel. thus, you'll run a little lean...course i heard our cars run a little rich anyways, so maybe thats why you can use the stage 1s without a tune

 

Good concept.

Also, being that you have a MAF sensor and not a MAP sensor, the change in manifold pressure due to the cam overlap, it isn't affecting the way the air is being metered as harshly. This is why you guys really can go ahead and do this and actually gain power successfully.

 

right, but don't expect some catastrophic gain, 5-6hp if that. you won't extract a new can grind's true potential until you tune fuel for it.

 

X2, a MAF is excellent at metering air regardless of changes in cams. The cam will allow more air into the combustion chamber due to increased lift and duration, which the MAF sensor can detect. On speed density systems, the change in idle vacuum can really play games with the MAP sensor.
Explanation?

Cobalts use a MAF sensor, any adjustments will be picked up by the car's fuel trims if necessary, and positive trims carry over to the power enrichment values. Bringing fuel trims closer to 0 does not unlock any potential, so I'm kinda lost in what you're trying to say here.

Edit: As long as turbulence in the induction pipe is minimized, no adjustments should really even be necessary, as trims shouldn't change.

 

a MAF doesn't know what your overlap is, nor does it know at what a/f you stop making power or start coming into knock. sure, it's going to, to a point, tune better than speed density when you make a change like this, but it's only changing fueling as much as the stock flash will allow, which is not going to keep performance in mind. also like I said earlier, with a more radical cam grind thats going to make impressive power in the higher rpm's, the stock system isn't going to do a whole lot but run marginally better in that area. I"m not even touching upon cam timing itself either. you're making a major change to the valvetrain, so tune for it, it's not very hard to fathom. 12whp gain on stock ecu is less than 30whp gain with proper fuel tuning.

 

You have confused tuning a speed density system with a MAF one. The MAF doesn't need to know anything about the cams, it has one job, to measure how much air flows by it. Changing cams doesn't change that parameter. A MAF does not dictate air fuel ratio.

Cams change the volumetric efficiency of an engine. MAF calibration does not depend on VE, it only measures an amount of air that passes by it. What does depend on VE is the Speed Density calibration, or more commonly referred to as a VE table. Changes in VE affect the VE table naturally.

Point I'm trying to make, is the MAF calibration is not going to dictate how much power you make. Don't think you'll make more simply because you're "not tuned".

 

you're taking what I said wrong. the point of all this is that the stock ecu will only tune to what it feels is ideal, and often times, it does not produce the most power at that point. I am not confused with speed density at all, the points still remain the same in that the MAF sensor is the means in which your airflow is metered and the most direct influence of fuel delivery. your primary o2 is going to catch it when things get too out of hand, but your MAF is always going to be the main influence since it is telling your ecu how much air it "sees" entering the engine, which directly influences what the fuel demand is.

not to mention that on many sets of cams, due to your overlap, you will see an a/f that will be in the 14's-15's and still be making power (because it is a flawed reading), but if you have your stock o2 read that it will and should richen the mixture.

if you really want to split hairs, your engine does have a MAP along with the MAF on the harness used in stock metering/tuning, and in theory should adjust great to it, but that is not always the case, and most likely will not be now.

go into any respectable shop and tell them you're planning to put cams in an engine and have the stock ecu tune for it, they'll either laugh at you or tell you the same things I have been.

I'm not going to debate something that is fact on various levels along with experience. you don't put aftermarket cams in an engine and expect the stock computer to tune for the best gain. you might pick up a few horses, but not what you should, unless you tune for it, thats just how it is.

 

omg you guys are making my head explode!

 

The post I asked you to explain earlier was how could a change in the car's tune unlock more power? What exactly would you change in a MAF metered EFI tune? I know exactly how an EFI system works, I don't need that explained, just what your interpretations of changing a fuel cal to unlock power.

The parts I highlighted really don't make any sense in what you're trying to explain.

First off, any emissions legal vehicle runs in closed loop in which the o2 has constant control of the fuel metering. It doesn't catch anything, and in PE an o2 has no effect on enrichment values, so you lost me on that point. The reason I keep saying the points you are providing only apply to a speed density setup is just that. Take a car that uses either a MAP sensor or alpha-n system to meter air, change the volumetric efficiency, and you'll be lucky if the car runs at all, let alone make more power. The MAF system doesn't work that way. It measures the actual air being ingested by the engine, so VE changes have no impact on its readings. The whole point of having a MAF based setup is its simplicity and ability to adapt to changes in VE as an engine ages.

Second, the flawed reading is not true. An increase in timing overlap would only affect oxygen sensors at idle (high vacuum), not in a condition in which power would be desired.

Third, any tuning shop will tell you that you will make the cams potential power not because of a change in MAF tuning, but because of the lack of supporting modifications such as a ported and polished head, UNLESS you have a speed density or alpha-n setup.

Lastly, you really haven't debated the question I asked. "Thats just how it is", isn't really a great arguement.

Thanks for keeping the conversation civil, I'm not trying to flame in any way.

Edit: Wow, this went off topic, all this is speaking of course in response to the Comp street cams.

 

changing cams on a 2.2 will unlock the upper end of the cams projected gains assuming you have the ability to flow the extra air. nothing really would need to be changed to unlock more power since the MAF can adapt to the increase in airflow

This is because pcm does not reference the o2 sensors at all during PE mode...it figures out how mch air is coming in...figures out its fueling for 14.7 then looks at its pe divisor...calculates new desired AF ratio then compensates teh fueling calculations to get that...no o2 sensors involved anywhere

 

Witt - the more I read through this, the more I think we're not seeing eye to eye because I mainly work on speed density systems. I might also be looking more toward the more radical end of the spectrum as far as cam grinds that are drastically different, along with having the supporting head work, again as this is mainly what I work with.

djt - so you're telling me if your primary o2 sees a far rich condition that it won't try to lean out at all because the PE mode calculations? this is true for WOT as well?

 

The car doesnt care what the primary o2 sees in PE.

Tho long term trims seem to carry over into PE.

if the car sees uber rich in closed loop (non PE) it will correct it...this correction will also carry over into PE...but the car is also monitoring the airflow all the time and adds fueling as reqired to keep desired af

Basically car wil completely adjust to cams and make extra hp

but fine tuning the limits set inside the pcm for spark and fueling may/will yield higher numbers (by allowing more timing/fuel to be run)

 

thank you, thats what I was getting at.

 

Ive just been reminded that -trims do not cary over into PE...only + trims

 

I think the confusion started because I originally quoted you in saying you had to tune for fuel to unlock the true potential of the cams, and stated why that isn't true. You assumed I said tuning in general I believe.

With the more wild street cams, they'll usually move the torque curve towards the upper end where VE is at it greatest. Changing parameters such as idle speed and rev limiter would be required to unlock the true potential of the cams and address issues with drivability. These are not considered fuel calibrations as you're not making any change in the way the car meters air, nor are you changing any enrichment multipliers.