^^^ wondering the same thing

 

My guess if for the factory IAT function, but I think some people use the MAF to base the low speed/boost tune off of.

 

Yeah just using it for the AIT sensor. I have a sensor, just been lazy on wiring it in.

Update on setup. Everything is in, big thanks to Kyle at KB-Racing for the downpipe and 3" intercooler pipes. I also got the rest of 4" exhaust done dumping over the rear axle. The tips are still in the roll pan for looks mainly. First feedback... This is a big dang turbo and it drives like a big turbo on this engine. It's like I removed the bov because it's never releasing pressure during normal driving lol like it did before. Truck is much deeper on the 4" setup and it below 3k you have Zero boost. Right around 3K you start to get like 1psi lol and it takes a few to really come online. Best way to describe this turbo on a 4.8L is simple, it's drag racing turbo. A few people said I should have went bigger on the A/R or bigger turbine wheel, those people haven't install one of these a 293. You would need a 3600+ stall. I can say without a doubt I will need nitrous to get this very heavy truck out the hole now with my tight 3k stall and I wouldn't put it past I MAY have to get a smaller housing, well see how it does though.

On to power, man its like a damn freight train. It's very very strong and once over the hump the damn thing rolls. I wasn't able to test it out much though as my 40mm wastegate can't keep up. I even put the light spring back in it. It opens around 12-13psi and by 5500 it rocketing past 20psi. I was at 105% injector at 5500 and 12.4 airfuel. This is with the deka 80s@ 60psi base, dual walbro 400s, KB boost a pump to both pumps, 8an feed. E85

This turbo flows some air, but I have to get a new gate in there now. What do you guys recommend? Install another 40? Or try to cutup and go bigger on my current location.

 

Yea that's just the nature of the beast with small ci. Prob gunna have to leave around 4500 rpm min with that combo on boost only. Bet it picks up around half sec at the track tho.

 

Yeah, Jarret whats your thoughts on a wastegate. 50mm or 60mm? It's kind of tight down there to add another 40, but maybe an option.

 

Idle clip, the Borla Xr-1 works great. For a 4" setup, it's pretty quiet overall to my happy surprise and becomes very vocal under boost.

GMC RST 4.8L with 4" Turbo Back Borla Xr-1 - YouTube

 

Sounds a lot like the S480 behaved on my 4.8. I would say turn the WG down to atmosphere to see how it controls boost, but you don't have a v-band... Backpressure is basically working against you at this point. Its just such a low restriction turbine and housing that not enough exhaust is forced through the gate. I would try a bigger gate for sure. 60mm is gonna have over twice the area for boost to push against so it will control it better. If any of that was obvious to you, sorry I made you read it!

 

Not sure Im still running the little 38mm turbosmart on mine lol. It's a poor mans boost by gear..

 

Well what the heck...

 

What's the danger of going with a WG that's too big over twin 40's?

Your combo sounds like what/how my STS used to work. I was cutting 2.7 sec 60' and wouldn't hit boost till about the 330' mark and 4500 rpm's. After that it was all kinds of fun and squirlyness since it was making 747rwhp/8xx rwtq. It wasn't much fun from a dig which is why I changed it all up.