I6 Power band....why?

[MikeyLikesIt]

First off, hello to all - newbie here (but long-time reader)...great resource and great people!!! This forum has definitley help me and my '03 Envoy SLE (I6 / 3.72's)...

My question is this: Why (oh why) did GM engineers decide that such a capable power plant as the I6 should have it's power band centered in a region that 99% of the GP will never see (5 - 6000RPM)???? I mean really, I could probably count on one hand the amount of times my Envoy has been over 3000 - 3500 RPM, and half of those weren't on purpose (pushed my foot a little far while saying "I need a tune")...

I know that hight MPG ratings sell vehicles, and that this is a ~5000lb. vehicle, but really - what would have been wrong with engineering peak torque at say, 3500RPM??? Maybe I should by a diesel (:D ), but it just seems odd.

Cheers!!!

[gmcman]

Welcome.......The I6 has a very flat torque curve and at around 2500 RPM's it is near it's peak or about 15-20% from it. This goes all the way to redline and the "powerband" you are referring to is when the exhaust variable valve timing kinda gets put in the mix and you have great response at this RPM range cuz the engine can get the exhaust out of the motor more efficiently. Headers help in this regard but can sacrifice some low-end torque so VVT is a viable option as in many of the import engines.

You will notice if you keep your foot at about 1/2 throttle and let the RPM's build it is very smooth and not "peaky" but pulls harder as RPM's increase....kinda like a turbo engine but with a small amount of boost.

I wish it had more torque around 1800-2200 RPM's but the 4-valve head kinda likes to be revved and you lose torque down low with this configuration but not much.

Want more torque down low get the V8 or a tune but I personally like the I6 better which is the main reason I bought this vehicle. I love I6's and they have their own distinct characteristics....enjoy it :thumbsup:

[ScarabEpic22]

Yep, gmcman is absolutely correct.

The I6 loves to be revved, but a tune really helps make the power come on sooner. Basically it is GM's Torque Management system coming into play that limits the throttle significantly until like 3000+rpm (think pedal to the floor yet the PCM only commands 70% opening till 3000rpm...).

If you look at the dyno graphs around here, the I6 TQ curve is almost flat. It goes to ~200-215tq (tuned) by ~2500rpm and stays above that till 5800-6000. The HP curve is more normal, but the TQ curve is more of a straight line. One of the reasons the I6 pulls pretty hard when you lay into it.:yes:

[MikeyLikesIt]

Great info - thanks a bunch!! I had wondered if Torque Mgmt. had something to do with it.....but it also makes sense if the dyno's are flat. It just feels a bit 'car-like' in the 1500 - 2500 range unless you are really feeding it some pedal.

Time for a tune....:cool:

[ScarabEpic22]

Great info - thanks a bunch!! I had wondered if Torque Mgmt. had something to do with it.....but it also makes sense if the dyno's are flat. It just feels a bit 'car-like' in the 1500 - 2500 range unless you are really feeding it some pedal.

Time for a tune....:cool:

Do it NOW!!! Seriously, even if you only have ~$200 get a tune and have PCM4Less (or whomever) tune it for a CAI. Then next month get a CAI for your truck and it will be amazing.

[Blazernut]

I think MTPockets said something about the Variable Valve Timing kicking in at that area too. It makes for a goofy power band that a good tune can make smoother by giving you more a little earlier rather than all at once kinda late.

B.

[ScarabEpic22]

I think MTPockets said something about the Variable Valve Timing kicking in at that area too. It makes for a goofy power band that a good tune can make smoother by giving you more a little earlier rather than all at once kinda late.

B.

:yes: :yes: My PCM4Less tune significantly changed the VVT engagement which is why it is sooooo smooth all the way to redline.

Im going to play with VVT and see if I cant get even more TQ down low where I need it launching off the line.:undecided

[blandmiller]

Erik, have you logged the valve timing at WOT to see what has changed in the tune? I am hesitant to make any changes until I have an idea of how far they are changing the variables. I imagine this will take a lot of dyno time to fine tune.

I still have not seen any indication of torque management affecting the throttle position. I have logged APP & both TPS sensors and do not see what you are seeing. Do you have a log that you can email me that shows this function?

[ScarabEpic22]

Erik, have you logged the valve timing at WOT to see what has changed in the tune? I am hesitant to make any changes until I have an idea of how far they are changing the variables. I imagine this will take a lot of dyno time to fine tune.

I still have not seen any indication of torque management affecting the throttle position. I have logged APP & both TPS sensors and do not see what you are seeing. Do you have a log that you can email me that shows this function?

I have, but my VVT settings were tweaked by Alvin at PCM4Less (he was testing something out), so I dont feel I can really say what he did as that is his business. But, yeah, Im going to try a couple things and street test them. I dont have the time or money for a day at the dyno to try and tweak the settings, but I plan on trying a couple settings and then going from there.

I cant say for sure that reducing the TM affects the TP, but I do know with the TM significantly reduced there is a lot less lag on throttle tip-in.

[blandmiller]

Fair enough. I never intended my request to be an infringement on the proprietary skillset of the tuner. Maybe I will purchase a "tune" from Alvin and see for myself. Good luck with street tuning the VVT. I hope you are using a G-Tech at least. If not, you might use the RWHP calculated PID that I posted at EFILive. The road load calc is still not finalized, so you will have to correct for ambient aero drag.

Since you don't have any data to support the torque management effect on 'throttle tip-in' we have to assume that your statements are an opinion and not verified.

I am not trying to start a conflict, I just want opinions stated as such.:thumbsup:

[Knightslugger]

First off, hello to all - newbie here (but long-time reader)...great resource and great people!!! This forum has definitley help me and my '03 Envoy SLE (I6 / 3.72's)...

My question is this: Why (oh why) did GM engineers decide that such a capable power plant as the I6 should have it's power band centered in a region that 99% of the GP will never see (5 - 6000RPM)???? I mean really, I could probably count on one hand the amount of times my Envoy has been over 3000 - 3500 RPM, and half of those weren't on purpose (pushed my foot a little far while saying "I need a tune")...

I know that hight MPG ratings sell vehicles, and that this is a ~5000lb. vehicle, but really - what would have been wrong with engineering peak torque at say, 3500RPM??? Maybe I should by a diesel (:D ), but it just seems odd.

Cheers!!!

People who drive cars and trucks do not drive on Horsepower, they drive on torque. the only time you drive on horsepower is on a sportbike and a road racing circuit.

[Jozuah]

People who drive cars and trucks do not drive on Horsepower, they drive on torque. the only time you drive on horsepower is on a sportbike and a road racing circuit.

:yes: :iagree: :iagree: :iagree: :iagree:

[ScarabEpic22]

Fair enough. I never intended my request to be an infringement on the proprietary skillset of the tuner. Maybe I will purchase a "tune" from Alvin and see for myself. Good luck with street tuning the VVT. I hope you are using a G-Tech at least. If not, you might use the RWHP calculated PID that I posted at EFILive. The road load calc is still not finalized, so you will have to correct for ambient aero drag.

Since you don't have any data to support the torque management effect on 'throttle tip-in' we have to assume that your statements are an opinion and not verified.

I am not trying to start a conflict, I just want opinions stated as such.:thumbsup:

Thanks for understanding man, I dont want a conflict either!:no:

Im going to try a couple different tunes tonight and see what happens, I will report back later or tomorrow with results.

And, unfortunately no G-Tech or anything. Think Im going to have to take a buddy along with a stopwatch.:(

Edit:
Well I just reflashed a tune with tweaked VVT settings, and so far it feels maybe a little faster but Im going to leave the tune in for a day or two so I can actually get a better variety of driving in before I make a final call.

[MikeyLikesIt]

People who drive cars and trucks do not drive on Horsepower, they drive on torque. the only time you drive on horsepower is on a sportbike and a road racing circuit.

Uhh...isn't that what I said I was looking for (torque)? :confused:

Cheers!

[Knightslugger]

Uhh...isn't that what I said I was looking for (torque)? :confused:

Cheers!

you never really said...