TURBHOE

iTrader: (4)

Under load and at that rpm lag shouldn't be much of an issues. Try the S472 but keep that turbine. It's not like you're running a 5.3l, that 6.0 should spool it just fine. I tow with mine all the time. From a 30' camper to just a pair of quads. I have my EGT probe on the number 7 cyl about 3"s from the manifold flange. Water meth helps with EGT's but also not dropping your timing too far and not over fueling. You may see 5-6psi at part throttle and 2500rpm but that doesn't mean that you have to back timing down to 5*, doing so will sky rocket EGT's. I've seen it because I've done it. Mine will pull hills at 2000 rpm at 33% throttle with 5psi and 1300* egt's. I'm running a TC78 with a 68mm turbine its a little small but i don't have the money to upgrade right now.

Now one thing that most people don't think about while doing this. when you're at low rpm like that and in boost make sure you have the oil pressure to do so. what i mean is low rpm/ low oil pressure but big load on the crank can equal the bearings and crank making love and spitting out little copper babies. iIm not saying its an issue with ls motors but just something to pay attention to.

As far as VVT comp has springs and cams that will work with the VVT stuff. In fact their cams for those (with tuning) seem to make a rather large increase in power. If my Tahoe computer could control VVT you bet your *** i'd use it.

camarokid6771

ill be watching this closely. I have similar ideas only im using a tvs2300 blower mostly cause that's what I already had on the shelf from another project. im starting with a stock LQ4 once I get a handle on the tunning ill build a 10:1 or so 390 or 408 so its a little more responsive out of boost. im also doing it on e85.

if it were me id be looking into compound turbo setup. with a single smallish turbine that will give great response at 2000-2500rpm will have huge amounts of backpressure if your ever loaded real heavy and it wants to do a 2ng gear downshift. let heat spool the turbo not backpressure. the hardest part will be keeping it at a sane boost level

did your cam'd LQ4 loose torque at 2000rpm?

GRRR65GTO

I cant tell you about EGTs, I'll have to leave my faith in slowhawk that he did it right, but I towed with my truck for the first time the other weekend and I was surprised how well it did. I towed a 20' open car trailer with a mustang on it (6000 lbs maybe?) and the truck didnt downshift until I hit some pretty decent hills in vermont. It just lugged in 4th gear in boost goin up hills but my 4:10s prob helped that, and only maxed out the WG a few times (at only 7 psi). Ive got a 76/64 On3 and it seems like thats what youd want for towing, it spools nice and easy on the highway. Considering youd be doing it to much newer truck with better heads and everything I would think itd do pretty good

Choda

iTrader: (1)

i have a stage 2 from trick on my 5.3 and towed my car/trailer combo which weighs around 5000 total. It was a cake walk and never went into boost unless i wanted it to. i could cruise or haul ***.

Doc_speeder

iTrader: (1)

No, definitely not, if anything it's stronger. With the 3.73 gears and 4L80E it runs around 2k rpm on the highway towing my 7500lb 5'er much better than it did before and holds OD better that stock.

Note though, I'm not sure how much of that is from the cam, or more likely the heads. They're small chamber, small runner 706 heads that I had ported and blended with 2" intake valves. So it has big compression and better slow speed port velocity. The combo works for towing even better than I had imagined it would, and better than people told me it would.

The best part is even with the very small cam it still has a great surge above 4k rpm.

Doc_speeder

iTrader: (1)

All good points thank you. The oil pressure thing is very logical and something to keep in mind for sure.

I was looking at either the Bullseye S368 or S472. Both look like good options I think, but I'm pretty new at turbo stuff. Bullseye makes an S375 and S475 both with a 75mm compressor and 83mm turbine with the same A/R options. What's the difference? Any advantage for my purposes of either one? Isn't the S3 series smaller overall? What does this affect?

Also, I would definitely keep the VVT if possible. Any reason you can't run a low boost setup with VVT functional? I like that the 2500 trucks don't have AFM at least.

smokeshow

iTrader: (16)

You can keep vvt, but you have to have a very experienced tuner...

TURBHOE

iTrader: (4)

Spring pressure and cam size both affect the VVT. If the spring pressure gets too high it can be hell on the cam phaser, but for what you want you wouldn't need any crazy *** springs. Comp has some for their VVT cams that should work well. They also have cams that are made for VVT (along with EPS and other cam companies). There is a phaser stop that gets installed inside the phaser to keep it from retarding the cam too far. If it retards too far your pistons and valves may kiss and that’s not good at all. You will need tuning for this stuff to be safe and make good power. But either way, if you’re going boosted it needs a tune.

Not sure on those two turbos I would have to look them up. For the most part though, on borg warners website the s300 series are t4 and the s400 series are t6 turbine housings. However, with the custom made turbos like bullseye and forced inductions they put different housings on them if wanted. A lot of it will depend on when you want boost to come in while towing and when you want to shift at WOT during play time and not loaded. If you don't care that it’s out of steam by 5800-6000 rpm and the cam matches then get the smallest compressor that can do the job but not so small that it has to work hard to do it. Same basic idea with the turbine side. At part throttle boosting 5psi low rpm you're not going to making near the exhaust flow as you would at a high rpm WOT so get what fits.

The TC78 I have is real small on the turbine side. It spools super-fast when towing but it's to the point where it's way too small for what I want to do.

TrickTurbo

iTrader: (12)

What exhaust wheel.

Anything pulling needs a 75mm or larger on exhaust side of things.

The boost or no boost when boost comes in is all good.
But no need to boost at all to increase pulling power.
Even if you don't build boost at low rpm no biggy.
The truck will still pull better.

TURBHOE

iTrader: (4)

Mine is the 68mm F1 iirc. I already know mine is too small.

This is true too. You will notice that you will hit zero vacuum faster and with way less throttle than before. Which means the turbo is providing air just not over what the engine can flow at that time (not pressurizing the manifold).

But there are a lot of guys using boost to tow easier on gassers besides the obvious (ecoboost). But if your going to do it on purpose I highly suggest an egt guage to go along with the other stuff. And don't try to go 11.5:1 AFR right off the bat. No need in it at those low boost areas it will just big the motor with fuel. I keep mine at 13-13.5 at 0-2 ish psi then run it down from there. Feeling the way it pulls and watching egt's will help you find the sweet spot. I hope you can tune, if not learn how because this isn't something you can just dyno tune in.