I can't find any dynos other than edmunds that say the L76 has a 4 sec delay. What is also funny is that the L92 6.2L doesn't seem to have this problem nor does the L76/98 that is in Holdens or the LY6 in 2500's.

even the SEA certified chart doesn't match edmunds. Was it a fluke? or something edmunds did wrong while dyno testing?

 

What model was that tested in?

If the 6-speed auto doesn't require such retarded torque management to be in place, then if they tested in the 6.0 in a 3/4 ton, it would be devoid of that delay.

Alternatively, I'm not extremely familiar with dyno testing methods but I have to assume there's some way to bypass that delay. Like maybe brake torquing at full throttle and then letting go of the brakes, or something else like that? Maybe Edmunds didn't know how to bypass that, or else they didn't want to because they wanted to show what a huge power loss the truck suffered at onset of WOT. Granted I'd think if they did that they should have also done a second trial bypassing the delay.

 

Wait a sec - I just realized something. That's a flywheel power dyno chart from SAE. That chart bypasses any effect of torque management or parasitic loss from the transmission or anything else. Of course a flywheel dyno isn't going to show losses from transmission torque management software if there is no transmission present.

 

Maybe they turned it off when they dyno tested the motor.

 

That isn't a chassis dyno. That is the SAE cert engine dyno run for the advertised power.

I don't know how that is done, exactly, under the new standard. I had actually witnessed and even done a few runs on a 5.3L back in 2002 or so, IIRC. Simple engine dyno run. But that was before the new SAE standard took effect.

I still find that 4 second delay before power enrichment to be hard to believe.

However, that was supposedly tested on an actual chassis dyno in a truck, so it is tough to compare it to this engine dyno run.

EDIT: I don't think that 4 second delay on the Edmunds test truck is there for any sort of transmission torque management. If anything (i.e. if that wasn't a cal problem on that particular truck), it is probably there for emissions and/or fuel economy purposes. Those are things that would keep it from going into power enrichment.

 

hmmmm. The Holdens and 2500's all use 6 speed autos or manuals. Maybe it is something in the 4 speed auto? but then again you would think the GMT-800 Silverado SS would have had the same issue. Traction control or stabilitrac on?

 

Was the Edmunds test truck Stabilitrak equipped? I havn't seen the article, but if so, this could account for the some of the delay in power coming on if they didn't turn it off. The newest systems have been more sensitive to a traction control type aid.

 

Another question: where did you get that SAE graph? Is there a site with all graphs for all vehicles that I could somehow get access to? That'd be sweet!

Or at the very least, if it's a private access site could you at least grab the graph for the Tundra 5.7L and the GM 6.2L as well? It would be interesting and answer a lot of questions even if it leaves any potential ECU and TCU issues out of the equation.

 

GMpowertrain.com

 

The Holden L98 doesn't have any issues. It certainly gets the 1800kg VE up and boogeying more quickly than the 1650kg LS1. There is no 4s delay built into any of Holden's LX tunes.

And yes, I have my doubts about the legitimacy of the truck article.

 

maybe the tires were spinning and they didn't notice it

 

The Holden's all use the 6 speed autos. Apparently the 'delay' is torque management on 4 speed auto 6.0s.

 

The 4l60 (or is it the 4l80?) combined with a 3.73 or 4.10 rear and all the power and torque the 6.0L has, may indeed be the reason for the torque management tune. That's a lot of power for an automatic tranny. The 4 speed also has a low 1st gear ratio. The torque management may simply be in place to deter hard launches (like burnouts and flooring the truck at a stoplight with a 10K load) which could shorten the life of the transmission. Let's not forget the age of this tranny. In their basic form, they've been around since '98 or so. The motors had nowhere near the power they had back in 98. I'm not sure about the 6.0L, but the 5.3 has seen an almost 50 hp and tq increase since then. This may be a simple case of GM covering their *** until the beefier 6 speeds are available for the more powerful motors (maybe the reason the denali and cadillac line got them from the get-go?)

I've gone through all the "too much power" crap when trying to find a rebuilt 700R4 for my 67 C-10. It's not real powerful, maybe 230hp or so, but most 700r4's were rated for much less power than that. I ended up getting a transmission that was built using "corvette 700R-4 stuff."


GM's powertrains have been out for some time, and have been somewhat proven as durable. The 5.7 is an all new motor, hooked to an all new tranny, in an all new truck.... I'd take the tried and true over new any day.

 

umm the 4l60e has been around for a while. and the LT1 was giving it plenty of torque in 95. And pretty much the entire LS1 lifespan with 350hp/350tq......

 

Is not the 4L60E an updated electronic version of the 700R4?