Full Power

VSR7875 Billet next gen .96AR on LM7 stock compression 5.3
TSP Low-Lift .551" 208/214 cam.
Motor is sound, runs good NA, as well as 295 horspower in a 5800 pound pig can run.
CircleD 2800 triple disc converter and 3.73 gears, I feel like I should have pretty quick thrust at take off.
What are some Tuning strategies to MINIMIZE Turbo LAG ?
How can I get this pig spooled up quicker ? \
Currently at 20 degrees spark advance idle, Should I bump my low load cells around 1000-1600 rpm up to 32 degrees ?
Can I leave it LEAN, with AFR 14-ish under 100kPa ?

Best fuel on road system here is 90 Octane, so my peak torque 4000 to 4400 rpm over 1.2G/Sec cells are sitting at 9 degrees, ramps back up to 11 degrees through 6400 rpm

This is my first Turbo project, am proceeding cautiously and don't want to melt pistons.

NoGo

iTrader: (2)

If you are on factory computer the strategy is to run timing as far advanced for part-throttle conditions as you can go without knock and run the engine at a ~13.5 to 14.0 a/f ratio. This will give you the least amount of turbo lag.

If that is still too laggy and you don't want to do setup-stuff (ie. taller gear, tighter converter, etc...) you can run an anti-lag program/button. On an aftermarket computer, just trigger the two-step/launch control connected to the button at either the launch rpm that works, or an elevated rpm (like 4k) if you are doing a rolling anti-lag. On a factory computer, you have to wire the IAT circuit to a relay that selects a "cold" resistor. Depends on your harness, but for many it is around an 8k ohm resistor. In the IAT table, set the timing to 0 at temperatures less than 30 deg F - (gimps your ability to drive in the winter). You can adjust the timing up/down in 5 deg chunks to get the turbo to light better depending on your setup (automatic/manual, etc...)

LQ4-E39

iTrader: (7)

Don't underestimate the need for a well designed hot side that retains heat and velocity which equals energy to spool the turbo. Truck manifolds, a "small" cross over (2") and wrap everything to keep the heat inside. As others mentioned, keep timing as at "NA" levels until you get into boost.

I recall you mentioning this build was in a Suburban. I'd love to see more details/pics on the build if you have it.

Jacob VH

For a turbo application I'd coat everything with something like cerakote piston coat. It's a thermal insulation coating. When I turbo my truck it's going on the entire hot side inside and out before it hits the turbo and then the outside of the turbine housing. If you want to go one step further wrap it with heat wrap and a turbo blanket. Turbo runs on waste energy and that heat is energy. even NA the added exhaust velocity will give you more power.
​other thing is make sure you use a boost controller to hold the waste gate closed till it hits peak boost
Running a different cam might also help if you haven't purchased yet. Truck Norris is good because the tight LSA allows some more duration while keeping the dynamic compression high for low and mid range power which will help light a turbo. might be iffy on 90 though

91 Z28

iTrader: (3)

Don't be putting too much faith in the Cerakote. My entire hot side is coated with it and honestly I'd probably just use a good wrap but it does look really really good even after many heat cycles

Jacob VH

Wrap has been shown to perform better, although I think the guy who tested it only had the outside of the other peice coated with ceramic . He did also show that they both were significantly better than without anything
My problem is I drive in the winter and wrap is a great way to get everything super rusty. That's why I'm going to stick with cerakote.I also apply it all myself, did a whole bunch if stuff for my motor with that and micro slick

Forcefed86

iTrader: (4)

Coatings and wrap are going to show negligible improvement at best on their own. You can’t expect to light off a turbo with baby amounts of HP and no real RPM to speak of. At least not with that turbo charger. Throw a tiny restrictive turbo on there and you can make it spool like a light switch. The 78/75 is a laggy turbo by nature. It has an oversized compressor wheel and undersized exh wheel. SO by nature it won't be as responsive as other units. What kind of power do you want? Do you need a 78/75?

The converter is hands down the most important part and will make or break the setup. I’ve tuned a lot of turbo cars and I’ve had nothing but problems with Circle D converters not stalling to their rated RPM. They are shelf converters and they will stall at totally different numbers depending on the power and load put on them. You can fart around with hotsides and the tune all you want for tiny gains. If the rpm isn’t there, there’s only so much “spool” to be had.

Do a quick test. Put the car in 1st and stomp the gas to the floor. What does the RPM flash to? That is your “Stall” rpm. Usually Circle D stuff is much tighter than advertised. Not saying there is anything wrong with the converter or the company. Only that in my experience they are always way tighter than advertised which kills response on turbo setups. Personally I’d want a 3500+ as my stalls flash rpm. This will ensure decent turbo response.

So replacing the converter (or re-stalling it) or running a smaller more responsive charger are your best bets IMO.

91 Z28

iTrader: (3)

This is exactly what I'm going thru with my 258mm pro billet Circle D unit. The thing stalls at like 2700-2800 and it's a complete dog off the line. I've got a brand new FTI converter waiting for me at home when I get out of work in 5 days. I'm hoping for better results with FTI

The BallSS

iTrader: (9)

Circle D can restall it for you pretty cheap.
I think they'll do the first one free or for like $60 and they'll send you a shipping label to save money on shipping too.
Mine was much better after restalling.

91 Z28

iTrader: (3)

Yea there was always that option and I was strongly considering that but my brother needed a converter for his 5.3/4l80 swap into his 94 Mustang so I have it sold to him for $1000 and the new FTI will only cost me $500

Forcefed86

iTrader: (4)

Just tell them you make 300 less HP than you really do. Then ask for 500 more RPM than you really want it to stall.

The BallSS

iTrader: (9)

You shut up lol.

djones293

Contact Pete Nichols at Circle D and tell him what you want. I had him spec my turbo 4.8 converter and it’s exactly what I wanted.