I've recently installed a 90mm Throttle body from a C6 on my 08 Sierra Denali, and when I took the CAI tube off and had someone mash the throttle to the floor, I noticed that it's not going WOT, only about 85%. I can physically open it all the way,so it seems to be an ETC /ECM issue. When I reconnected my stock 87mm TB, it opens fullly. I know from checking other sites that this has been a problem for those who install the C6 TB on the ETC trucks, but I've yet to find a solution, so I'm wondering if there is one? Even the HP Tuners forum doesn't seem to provide any answers, although I've found numerous posts about others having this problem from as far back as a couple of years ago.
I don't know yet what the TPS voltage is, since my multimeter is on the blink and my tuner is out of town for a few days, so I can't get the HP Tuners on it as yet to see what the ETC % or TPS % is with each TB at WOT.
Does anyone know whether there's a fix for this?

 

do a search for drx harness

 

Thanks. I checked it out. I couldn't find much on it, but it seems to be an adapter harness to adapt the older 3 bolt 78mm throttle body to the newer 4bolt style harness?
My truck came with the 87mm 4 bolt TB and the C6 90mm is a plug and play deal, except that the damn thing won't open all the way to WOT. WTF?

 

that's just it . . . unless there's something else. . . you'll have to buy the adapter box to make it work.

 

how much gain do you expect with 3mm?

 

yeah no joke ^^^^ I wouldnt think there would be any other advantage?

 

It's not just that it has a 3mm bigger blade. The stock 87mm truck TB has huge ridge at the bottom, in front of the blade that has to be a restriction @ WOT (unless its ported - which I'm thinking of doing). I posted a thread the other day about this mod and somone responded that they knew of someone who had done it and gained a .15 - .2 second reduction in ET, so I thought it was worth a try. Besides, the 90mm is actually an LG ported LS2/Z06 TB and I got it off a friend for nothing, so why not try it?
There is a big difference in appearance between the two, even the ETC motor is different, maybe even the gear ratio is different?
Another thing I've noticed is that the blades rotate in a different direction on each of the TBs, which might be because of the angle of the Truck intake vs. the Car intake.
So, who knows, it might not be worth ****, but you wouldn't know until you try it, right?

I've found the website for the harness. It's a company in Canada called TorqueRush. What I'm trying to ascertain is whether this is an adapter harness to adapt the older LS1 Corvette style plug to the newer ETC plug. That will NOT fit my truck since I already have a new style plug/harness (so, I DON'T need an adapter).
Having said that, there must be some difference in the WOT voltage signal between the new 87mm Truck TB and the 90mm Car TB, because on the Torque Rush site the install instructions tell you that for the new Truck TB (which they erroneously call a 90mm) you have to leave two looped wires inthe harness intact, whereas, with the Car 90mm TB you have to cut the two looped wires. That tells me there is a difference in what the Truck TB needs to see from the ECM that what the Car 90mm TB needs to see, no?
There has got to be someone out there who knows something about this, I would think...

 

Update:
I've just received an e-mail from Torque Rush and they have confirmed that their adapter will NOT work on my truck, just the older LS Trucks. Grant @ Torque Rush says they were working on a prototype for the TBSS guys, which would have worked on my truck, but the lack of demand has committed that to the shelf.
So, I guess I might as well bolt back on the stock TB, unless one of the tuning gurus have a fix. I am convinced there must be some way to fix this with a tune, since my truck has the same E38 ECM as the LS3 C6's right? So why can't my ECU be programmed to tell the C6 TB to open all the way to WOT?

 

If your logging with hptuners it will only show 83% open, but in reality is open 100%, look in the help area it will show you.

 

the new truck TB's open very slowly, so not only do you gain the extra airflow but the throttle response should be greatly improved with the new throttle body.