wut is up with the new 2006 4.2 vortac?

[venom blk]

first off i love this site , it has helped in way u would not know how. ok in the last few weeks i have been looking in to the stats of the 2006 trailblazer and it has 290@6000hp and 277@4800tq. now this can not be the change of cams or heads because the TQ only went up by two what do you think cause im thinking programer :confused:

[Dave]

Welcome to the site! My guess would be programming or the higher hp rating is at a higher RPM.

[wmomran]

I guess programming also since TBs soled on arabian gulf claim to have 294 HP @ 6000 RPM check here (http://www.chevroletarabia.com/content_data/LAAM/BH/en/GBPBH/chevrolet/models/trailblazer/specification/trailblazer_engine.htm).

Note:
This may be because the different meanning of "Gross HP" vs. "Net HP". I don't know if the 274 HP listed on the american (http://www.chevrolet.com/trailblazer/specifications/#engine) site is net or gross.

[tb_ky]

I was thinking that the peak 275 hp on the 2002-2005 models was at 5700 rpm. Maybe I'm wrong.

[oachalon]

did gm even change anything to the engine or did they just rate the engine on the new sae standard and the engine is putting out more power than what gm originally rated it for like the rest of their engines. I dont know if you guys have been up to date but gm's engines have been rated conservatively and on the new standards their engines have been gaining horsepower while the rest of the car manufacturers have gone down.

[tb_ky]

Interesting.... :undecided

[bmm354]

did gm even change anything to the engine or did they just rate the engine on the new sae standard and the engine is putting out more power than what gm originally rated it for like the rest of their engines.

I was wondering the same thing. But I'd guess they did some minor software tweaks to bring the I6 more in line with the Explorer's reworked V8. One of Chevy's bragging points about the TB was how the standard 4.2 I6 made more hp than the Expy's optional 4.6 V8 (275 vs. 240) and was just 5 ft-lbs of torque shy of the 4.6. The Explorer V8 has 292 hp for '06, and now the I6 pretty much matches that. Interesting how close the hp figures are... :undecided

I think it's cool that the new standard shows just how truthful/conservative GM was with hp ratings. I've heard that in many cases other mfg's ratings took a fairly big drop.

[rtay2000]

The bump in HP maybe due to the new SAE standards they are using to get HP/Tq numbers now. if you notice the 06 z06 was rated at 500 but after the testing they are showing as 505hp.


Edited just because i read the whole thread and someone already mentioned this. :duh:

[briant73]

Hi newbie here but I found out two things from GM on the new power rating
1) Higher compression ratio for 2006
2) Better engine breathing for 2006
This is according to GM media online at http://media.gm.com/us/powertrain/en/product_services/whats%20new/06%20truck%20eng/06_PWT_%20Vortec%204200%20LL8.pdf

So for the compression ratio not a lot you can do but a CAI or better airflow might give you a decent power increase.

[CarbonEnvoy]

great info... thanks for the post.

Although it's cool to see some more performance squeezed out of the 4200, I hope pushing it harder doesn't hurt reliability.

[envoy62]

Interesting letter, after reading it i would like to point out the following.
The better breathing is due to larger intake and exhaust valves so thesre isno new better intake manifold used. Upgrading an older engine is not easily possible, new cylinder head might fit the older engine.

Mass airflow sensor, well on my 2002 GMC Envoy i have a map sensor (manifold absolute pressur). I don't hnow if pre 2006 had all map sensors or if they channged down the road.

The difference is that air intake is not measyred directly, but is calculated using the map sensors pressure gutput and taking in account volumetric efficiency at various operating conditions.

Traditionally non US automakers used the mass airflow sensor since a long time. In the past there was allways a debate about what is better, mass air flow sensor measures air intake directly, which with the new devices might be more precise and therefore make it possible to squeeze some horses more out of the engine.

The other difference are also interesting to note, since they deal mostly with engine durabilkity and reliabilty.

This also means that in the feature we won't see many engine tuning parts for older I6. Since the engine management system is going to mass air flow systemm nothing will be compatible.

Cheers

[Toolman]

I need to get some 06 heads..