[brentil]

Well, I've been chcking GM Dealer World every day in hopes of finding new info. There's a couple specific things I look for. Wheel images, radio images, engine info, etc.

Well this weekend GM officially put up the dyno graphs for the 2.4L VVT ECOTEC engine across all the lines using it except the HHR so far.

I've attached the following files;

1. Solstice dyno graph
2. G6 dyno graph
3. Cobalt SS dyno graph
4. Cobalt 2.2L dyno graph
5. Cobalt SS Supercharged dyno graph

I'm working on photochop of them together for comparison reasons.

 

[psycho-squirrel]

Nice find brentil!

I am curious as to why the Solstice 2.4L has a hiccup around 3000 rpm for both torque and HP?

The torque curve at 3 grand has a dramatic dip, while the hp graph is only slightly affected.

There seems to be little or no hiccup on the other 2.4's (detuned versions).

Anyone have an idea about what's going on here?

 

[rlhammon]

Thanks for the post...

I only wish that the graphs had common scaling so that you could compare them side by side without a little more ease.

Seeing as the Cobalt is roughly 130 lbs. heavier, and little less torque, and it's front wheel drive I think the Solstice will be "fun" to drive, though a FI motor would be "more fun".

You can break loose the tires in the base Cobalt in 1st and the 1st to 2nd shift. I haven't had the pleasure of driving the Cobalt SS w/ the Supercharger in it tough, and doubt I'd be able to "test" it as I would like.

Glad to see the official dyno's though... great find, and thanks for looking (so I and others didn't have to).

 

[Fformula88]

Great find Brentil! That is a funny hiccup. Cam changeover for the VVT?

 

[DreamerDave]

......... Cam changeover for the VVT?

That's my guess.

 

[brentil]

Combined comparison graph to scale.

I wanted to say VVT too, but look at the 2.2L, it has it too.

 

[stonebreaker]

Could be tired/bad valve springs developing a harmonic. Do the ecotec springs use dampers or are they beehives like the LSx engines?

 

[WaitingForBoost]

Great find Brentil! That is a funny hiccup. Cam changeover for the VVT?

The LT1 has exactly the same "hiccup". I've seen it on other graphs, too. It's not uncommon. VVT? No, I don't think that's part of it.

 

[ImSlow]

Hehe maybe Im being anal but the torque drops a few ft/lbs below 90% of peak at that dip at 3000....not that i care about a few ft/lbs really...its just the point

 

[cdb]

it looks like the solstice motor is tuned to produce the most torque in the low rev range compared to the other NA ecotecs. that could accentuate the dip at the VVT changeover. if the trade is a dip at 3000 for more tourque off the line then i'm all for it.

 

[Adrenaline]

From the other thread on shifting techniques and my recent discoveries, having a drop at 3,000rpm isn't a big deal at all, just shift a little before 3,000.

 

[DreamerDave]

OK, you guys that're better than me with a calculator, could you figure out if up shifting at 6500RPM would drop you above or below that torque valley around 3000RPM?

 

[ImSlow]

OK, you guys that're better than me with a calculator, could you figure out if up shifting at 6500RPM would drop you above or below that torque valley around 3000RPM?

I highly doubt it will drop even close to 3000rpm...anyone get transmission numbers yet? If it does Im gonna go buy something else :brentil: .....in my current neon when i shift at 6500 from first to second gear it drops to roughly 4800

 

[SkyCaptain]

1st, the fourth dyno pic is pretty screwed up. The lines are supposed to cross at 5252...

2nd, I'd definately have to drive the car to see if the flat torque makes up for the ridiculously low hp in the low rpm ranges...

 

[SolsticeMan]

1st, the fourth dyno pic is pretty screwed up. The lines are supposed to cross at 5252...

...

I thought the same exact thing, Sky'. For whatever reason, they re-scaled the hp axis. If you fix the hp axis, the crossover is at (or eyballing it) 5252.

 

[brentil]

I'm thinking this is not VVT switch over. Because as I said the 2.2L has it too, and it doesn't have VVT. I'm betting it's just how the ECU is designed to make the engine perform at the lower RPMs in order to provide more Torque. Because looking at the other two 2.4L VVT engines they don't have it. However they also have much lower starting Torque values. I'm working on another photchop of just 2.4L compares.

1st, the fourth dyno pic is pretty screwed up. The lines are supposed to cross at 5252...

It's screwed up I believe because for some reason they used two different scales on either side. They only used up to 150 on teh HP scale, but 300 on the Torque scale. If you look at my combined chart it's in the right place.

Hehe maybe Im being anal but the torque drops a few ft/lbs below 90% of peak at that dip at 3000....not that i care about a few ft/lbs really...its just the point

Actually 90% of 166 is 149.4. Which looking at the dyno chart it seems the line drops to about ~148~149. GM has also only ever said 90% was available at 2400 RPM, they've never said it stayed above 90% all the way up unfortunately.

 

[Darkhamr]

It could be poor fuel tuning, but looks a little much for that. I would guess poor IM design.

 

[stonebreaker]

The LT1 has exactly the same "hiccup". I've seen it on other graphs, too. It's not uncommon. VVT? No, I don't think that's part of it.

The LT1's torque dip is easily cured with a set of aftermarket springs.......

 

[WaitingForBoost]

The LT1's torque dip is easily cured with a set of aftermarket springs.......

Then a harmonic makes sense. The supercharged Ecotech doesn't have it because FI engines are different animals.

If I could post attachments, I could include a dyno graph of my 1993 Z28, from the F-body mailing list get together in Memphis, in 1998. It clearly shows a very similar dip. (At that time the only engine mods were headers, catback, and cold-air intake, pretty lightweight stuff. Rated at 275 hp at the flywheel, these mods got me ~295 at the wheels. Clearly GM was under-rating their hp claims even then.)

 

[brentil]

This took longer then expected because I had to deal with some other stuff first.

This is a comparison of the 3 flavors of 2.4L VVT ECOTEC so far available. I'll add the HHR and Sky once they're released.