If stuck with a healthy L05 TBI... Options for 'go-faster' and improved fuel economy?

[SpitShine_PL]

As in the post title.
What are the entry-level options for going, errr, a BIT faster and enjoy better fuel economy with the L05? (Yeah, I know how it sounds, but 2 mpg more would be an improvement, right?)
I figure - a TB spacer, improved flow intake manifold, and better exhaust headers would come first, right? What is the actual specs limit for these mods that doesn't require a chip re-tune (which is a PITA, last I heard)? I'd go for a bit of more acceleration in the mid rpm range (for passing by with more confidence at 60-70 mph). (I can already feel people are gonna reply I'm joking, haha!)
One item of note is that a potential L05 Suburban would run dual fuel. This means aftermarket LPG delivery, kinda like in Honda propane-butane powered industrial trucks. LPG for motor vehicles is immensely popular in Europe - first because of gasoline prices (over 6 bucks a gal in most places... Talk about Europoors!). Even the TBI-compliant LPG systems have evolved enough they're not problematic; still, however, LPG is a fuel which burns 'dry' - this means less unburned residues in the engine internals, e.g. valves, cylinders, bores, etc. than running regular gasoline.

 

[DerekTheGreat]

I'm not convinced a TB spacer would add any sort of improvement. I feel the best thing you can do is to enable lean cruise. I believe my truck has that going for it, it'll do 19+ mpg on the expressway at 70mph. It is a 350 five speed truck, regular cab short box, K series (4x4) with a 3.73 axle ratio. I'm very impressed with those numbers. Everything on it is stock, timing set to 0 degrees as mandated by the factory.

 

[SpitShine_PL]

19 mpg would be very neat. Hell, 18 mpg-ish sounds very good, too (my regular long distance drive is hwy, 70 mph 2/3 of the way). 5 speed, that's a stick shifter, right?
You also got a pickup truck... A Sub adds several hundred pounds of good ol' Murican steel to GVWR, a considerable factor when talking weight vs. fuel economy (plus aerodynamics... them lovely cinderblock-form OBS SUVs!).
So... Probably a 3.73 RAR would improve things a bit over the stock 3.42.

 

[95burban]

TB spacers help on a TBI motor but not much. Very similar to a carb spacer.

Biggest improvement would be a gear change.

 

[SpitShine_PL]

I am actually considering a RAR change, as I'm looking into an LSD for that car; L05 means a Burb w/o stock electronic traction control, and we all know what G80 is like.

 

[Schurkey]

WHAT YEAR? 2- or 4 wheel drive? 1500?

First Guess: You'd never notice the TBI spacer or different intake manifold on a dyno unless it made things worse. The TBI intake is as tall as the "high-rise" intake that comes on a ZZ4 crate performance engine.

Headers, high-flow catalyst, and low-restriction muffler might make a meaningful difference; although I bet the original catalyst--if it's a pellet-style like my '88--has blown out all the pellets by now and is currently an empty shell.

G80 on the ten-bolt axle is a mess; G80 on either of the 14-bolt axles is not so bad.

I can imagine a shift from 3.42 to 3.73 gears making an improvement in performance...if your overall speeds are low enough. As a highway cruiser, you might be going the wrong way for economy. 3.08, perhaps. 'Course, it'll take you all afternoon to get up to that highway speed.

Consider adding a degree or five of initial timing. Supposedly, the TBI swirl-port heads don't need much advance, but I'd experiment--and keep an eye on the knock sensor output so the truck doesn't detonate and retard the timing you've just advanced.

Consider a 205 degree thermostat. Might help...might not.

Rebuild the brake calipers so they don't drag. Air up the tires, but not so much you burn the tread off the center. Use the A/C instead of rolling down the windows. Use the cruise control when possible.

Beyond that, enabling Highway Lean Cruise in the computer programming would be wonderful. One wonders if that's already active on a Euro vehicle. But all that programming stuff is way beyond my skill set.

 

[SpitShine_PL]

I guess you figured it out I've already eyed out a specific L05 vehicle.
The RPO sheet says I'm already good with the gears and brakes, I think.
The Burb is not an export/Euro/GCC build; someone imported a US version here, so I guess no HLC was enabled (tho the GMT400 Tahoes and Burbs used to be sold in Germany, Belgium, France and somewhere else, complete with Euro-spec headlights, like those from Arteb).

 

[wb292]

I drive about 70 miles each way to work. So at 140 miles a day, gas mileage is very high on my list of priories. Here are few thing I've done on my RCSB K1500 with a 5 speed HM290 Transmission.
I installed load range E tires and aired them up to the 85 PSI listed on the side wall. Removed the entire exhaust and threw it away. I installed JBL shorty headers and y pipe. Then 3 inch single pipe to a muffler and stopped before the rear axle. I also wrapped the exhaust from the heads to the transfer case. Removed the air pump and EGR. installed a edelbrock tbi intake that I bored to 48MM. installed a 180 deg thermostat so I could advance the timing and keep pinging to a minimum. I used a 4 inch X 14 air filter to help it breathe.
I bought a stage 1 chip from Harris Tuning with gas mileage as my biggest request other than power. I consistently get 21 MPG driving it at 70 MPH for 50 miles each way.

 

[tayto]

find someone to do a tune, they can enable things like "highway mode" etc that will bring up your mpg. FWIW, while LPG has it's pro's one con is it's usually it gets 30-40% LESS mpg. IMO you really need to build a high compression engine (11:1+) to really extract all the benefits out of LPG.

 

[HotWheelsBurban]

I guess you figured it out I've already eyed out a specific L05 vehicle.
The RPO sheet says I'm already good with the gears and brakes, I think.
The Burb is not an export/Euro/GCC build; someone imported a US version here, so I guess no HLC was enabled (tho the GMT400 Tahoes and Burbs used to be sold in Germany, Belgium, France and somewhere else, complete with Euro-spec headlights, like those from Arteb).

We have a member who can run VIN reports for members for free, and you can see what all those codes stand for. His username is @1ton-o-fun. I can tell you that the JB 6 is the suburban 11" brakes that are better than the half ton pickup ones. I think GT 4 is 3.73 rear end gears; my Burb has 3.42 gears so my code is different.