Finally Touched by HP Tuners!
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From: Hubert NC
VVT is Vtec? I was under the impression that only Honda had different cam lobes for high and low RPMs. I always thought that VVT was just the PCM advancing and retarding the cam timing for optimal efficiency. If GM has Honda style Vtec then wow, these cars should respond to boost like a fat kid to McDonalds.
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http://en.wikipedia.org/wiki/VVT
Piston engines normally use poppet valves for intake and exhaust. These are driven (directly or indirectly) by cams on a camshaft. The cams open the valves (lift) for a certain amount of time (duration) during each intake and exhaust cycle. The timing of the valve opening and closing is also important. The camshaft is driven by the crankshaft through timing belts, gears or chains.
The profile, or position and shape of the cam lobes on the shaft, is optimized for a certain engine rpm, and this tradeoff normally limits low-end torque or high-end power. VVT allows the cam profile to change, which results in greater efficiency and power.
At high engine speeds, an engine requires large amounts of air. However, the intake valves may close before all the air has been given a chance to flow in, reducing performance.
On the other hand, if the cam keeps the valves open for longer periods of time, as with a racing cam, problems start to occur at the lower engine speeds. This will cause unburnt fuel to exit the engine since the valves are still open. This leads to lower engine performance and increased emissions.
Pressure to meet environmental goals and fuel efficiency standards is forcing car manufacturers to turn to VVT as a solution. Most simple VVT systems (like Mazda's S-VT) advance or retard the timing of the intake or exhaust valves. Others (like Honda's VTEC) switch between two sets of cam lobes at a certain engine RPM. Still others (like BMW's Valvetronic) can alter timing and lift continuously, which is called Continuous variable valve timing or CVVT.
Piston engines normally use poppet valves for intake and exhaust. These are driven (directly or indirectly) by cams on a camshaft. The cams open the valves (lift) for a certain amount of time (duration) during each intake and exhaust cycle. The timing of the valve opening and closing is also important. The camshaft is driven by the crankshaft through timing belts, gears or chains.
The profile, or position and shape of the cam lobes on the shaft, is optimized for a certain engine rpm, and this tradeoff normally limits low-end torque or high-end power. VVT allows the cam profile to change, which results in greater efficiency and power.
At high engine speeds, an engine requires large amounts of air. However, the intake valves may close before all the air has been given a chance to flow in, reducing performance.
On the other hand, if the cam keeps the valves open for longer periods of time, as with a racing cam, problems start to occur at the lower engine speeds. This will cause unburnt fuel to exit the engine since the valves are still open. This leads to lower engine performance and increased emissions.
Pressure to meet environmental goals and fuel efficiency standards is forcing car manufacturers to turn to VVT as a solution. Most simple VVT systems (like Mazda's S-VT) advance or retard the timing of the intake or exhaust valves. Others (like Honda's VTEC) switch between two sets of cam lobes at a certain engine RPM. Still others (like BMW's Valvetronic) can alter timing and lift continuously, which is called Continuous variable valve timing or CVVT.
As for a company, not familiar with the area.
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From: Moncton Newbrunswick Can.
Originally Posted by ADRIEL
Changing from the VVT-VTECH debate. Does anyone know of a company that tunes Cobalts in Westren Canada (Manitoba west)??
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From: Calgary,Canada
Originally Posted by ADRIEL
Changing from the VVT-VTECH debate. Does anyone know of a company that tunes Cobalts in Westren Canada (Manitoba west)??
http://westers_garage.eidnet.org/Index2.htm
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From: Atlanta
Originally Posted by panblackrose
I'll look into that Witt, I plan on making a trip to Dynotuned Performance in Hampton within the next couple of days. I'm still just playing around seeing whats up with the system. If I kill my cat, good, a reason to buy a highflow system. 
As for speed limiter, I upped it from 120 stock to 150 for the hell of it, but yes you could tune it for 70 if you want to keep people from messing around. If I remember correctly, you can set the rev limit for each individual gear
Yes, VVT IS VTEC, but I don't know why everyone thinks vtec sounds like ****, its just the hondas that carry it. I had a 94 D16Z6 SOH VTEC 1.6L that sounded like a monster, especially when vtec kicked in. No nasty vibrations, no ugly sound. Once I hit 4000 in the cobalt, it just pulls harder and sounds a little deeper.
As for speed limiter, I upped it from 120 stock to 150 for the hell of it, but yes you could tune it for 70 if you want to keep people from messing around. If I remember correctly, you can set the rev limit for each individual gear
Yes, VVT IS VTEC, but I don't know why everyone thinks vtec sounds like ****, its just the hondas that carry it. I had a 94 D16Z6 SOH VTEC 1.6L that sounded like a monster, especially when vtec kicked in. No nasty vibrations, no ugly sound. Once I hit 4000 in the cobalt, it just pulls harder and sounds a little deeper.
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From: Phoenix, AZ
I just got ahold of my friend's laptop with HP Tuners. Within a frew days of sitting down and reading I decided to start making changes.
1. Remove Speed Limiter
2. Have Fans Come On Earlier For Cooling
3. No Delay For Power Enrich Mode
4. WOT Is 88% Throttle, Instead Of 92%
5. Power Enrich Adds More Fuel Than Stock
6. Stoich AFR Is 13.7 Instead Of Stock 14.7
7. Piston Protection Enables At 3300 RPMs Instead Of 3800 RPMs
8. Idle Begins With 1200 RPMs And Steadily Lowers To 950 RPMs Once 170 Degrees Is Reached
EDIT - 9. Changed rev limit to 7000 and so far so good. I wont go higher until I have better springs and cams (then itll be set for 8000)
1. Remove Speed Limiter
2. Have Fans Come On Earlier For Cooling
3. No Delay For Power Enrich Mode
4. WOT Is 88% Throttle, Instead Of 92%
5. Power Enrich Adds More Fuel Than Stock
6. Stoich AFR Is 13.7 Instead Of Stock 14.7
7. Piston Protection Enables At 3300 RPMs Instead Of 3800 RPMs
8. Idle Begins With 1200 RPMs And Steadily Lowers To 950 RPMs Once 170 Degrees Is Reached
EDIT - 9. Changed rev limit to 7000 and so far so good. I wont go higher until I have better springs and cams (then itll be set for 8000)
You can set WOT to about 75%, and disable A/C at the same Throttle Position%. Does not add power but gives you WOT without having to ram the pedal to the floor.
You might want to set PE delay to about 2500-3000 rpms. It doesn't prevent it from happening, it just scales it back until then. Try messing with the enrichment rate value in the PE screen by bumping it up just a TINY bit.
Would you mind emailing me a stock 2.4L tune so that I can play with it. I will send you back my results. I have tuned 14 cobalts so far, so I might be able to help you out some. Thanks
EM to stevenkenniff2005@yahoo.com
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From: Phoenix, AZ
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From: .
http://youtube.com/watch?v=WRv4Mp-pmBo
just close your eyes and imagine me on the mower powerhifting all the way through 7th (yea its a 7 speed) on the rear wheels the whole way, then i hit the nitrous and this happens
http://youtube.com/watch?v=7032PBiIDyM
LOL. that cobra sounds so damn good, god i want one.
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From: .
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Joined: 05-20-06
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From: Phoenix, AZ
actually they edited this video onto the sound of my mower.
http://youtube.com/watch?v=WRv4Mp-pmBo
just close your eyes and imagine me on the mower powerhifting all the way through 7th (yea its a 7 speed) on the rear wheels the whole way, then i hit the nitrous and this happens
http://youtube.com/watch?v=7032PBiIDyM
LOL. that cobra sounds so damn good, god i want one.
http://youtube.com/watch?v=WRv4Mp-pmBo
just close your eyes and imagine me on the mower powerhifting all the way through 7th (yea its a 7 speed) on the rear wheels the whole way, then i hit the nitrous and this happens
http://youtube.com/watch?v=7032PBiIDyM
LOL. that cobra sounds so damn good, god i want one.
Those are great videos!
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From: Phoenix, AZ
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From: Oakland, Ca
lots of bad misinformation in this thread.
its not possible yet to change the phasing points of vvt, and if it was, i doubt you'd see any difference in preformance (if not degraded preformance) without a cam swap.
more timing is a desired thing. However, with PE spark adder+high octane tables my modified tables only give me 35-40 degrees at WOT w/ 91octane, i HIGHLY doubt your stock tables are higher then my modified tables.
log advance in a histrogram and you'll clearly see where your confused. your not racing at .08g/cyl, your idle revving!
also, if you've corrected your PE-AFR before you've calibrated your maf your going to be chasing your tail when you start modifing spark.
no.
its not possible yet to change the phasing points of vvt, and if it was, i doubt you'd see any difference in preformance (if not degraded preformance) without a cam swap.
log advance in a histrogram and you'll clearly see where your confused. your not racing at .08g/cyl, your idle revving!
also, if you've corrected your PE-AFR before you've calibrated your maf your going to be chasing your tail when you start modifing spark.
no.
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From: Virginia Beach, Va
Ok, first, I changed the stock AFR because I thought that would help me under acceleration, but I reflashed closer to stock because I realized my mistake.
Yes, I added a small amount to the PE enrichment rate and also took the delay to zero and it really did help with the response of the car.
As for my advancement, Im still not a big tuner guy so I haven't messed with anytihng else until I finish reading and learning more about it. I did get some runs down in a log to 95 mph and it clearly shows my advance on timing is 38+ degrees when I was under full acceleration... I think I know when I'm idle revving.
As for all of the helpful hints and all, thank you, im may reply a little snippy, but I have been really busy lately. I just woke up after actually getting a little sleep in the past 48 hours (worked constantly over the past weekend. 3:30-9:30pm, went back at 3-11am, went back again for 4-7pm and finally had some rest)
Psykostevo, thanks for the offer, email with instructions on how to do that well_of_souls245@yahoo.com
Yes, I added a small amount to the PE enrichment rate and also took the delay to zero and it really did help with the response of the car.
As for my advancement, Im still not a big tuner guy so I haven't messed with anytihng else until I finish reading and learning more about it. I did get some runs down in a log to 95 mph and it clearly shows my advance on timing is 38+ degrees when I was under full acceleration... I think I know when I'm idle revving.
As for all of the helpful hints and all, thank you, im may reply a little snippy, but I have been really busy lately. I just woke up after actually getting a little sleep in the past 48 hours (worked constantly over the past weekend. 3:30-9:30pm, went back at 3-11am, went back again for 4-7pm and finally had some rest)
Psykostevo, thanks for the offer, email with instructions on how to do that well_of_souls245@yahoo.com