'93 TBI 350 Mileage Questions

[1993-Sierra-Z71]

hey guys i got a '93 k1500 with the 350 in it. i was wondering what you guys have done to increase mileage. so far I've done the air lid flip and i have noticed a mileage gain, around 1-5 mpg. if i switch to a drop in K&N Filter, would there be any gains? i know it will be minimal, but worth a try, right? the other thing is that if i do the air resonator delete mod and run a straight tube to the inner fender is there gains there? what about changing the timing on the distributor? any power or mileage gains? the headers and full exhaust setup is to expensive for me right now, but it will come. also, do throttle body spacers really work? any gains? and I've seen the spacers for the jets in the throttle body that claim 5-10 HP gain over stock for 12 bucks on eBay. any truth to that?? any info would help!!!

[Sierra383]

The drop in filter would do little without the whole air intake in my opinion. I've also heard of people that advance their timing a little bit. I never had much luck with my spacer but for 12 bucks what the heck try it.

[1993-Sierra-Z71]

Thanks! Imma try the spacer and Imma go to my local wreck yard tonight after school and look for a intake tube and a gas door spring. and do you know how far they advanced the timing??? I got a timing light but no previous knowledge on advancing timing for power or economy. anyone know?? I don't wanna go into unknown territory ya know? :jerry:

[94_c/1500]

Put the lid back, don't waste your money with a K&N, a tube replacing the resonator will help but not much, timing is usually increased 2-6 degrees, and spacers do work.

My advice for a budget is do all of the TBI mods, turbo muffler, thunderbolt cats, and a chip burned.

[1993-Sierra-Z71]

thanks 94_c/1500. imma try the timing today. also imma still try the intake tube anyway, saw one at the junkyard and im guessing its gunna be like 5 bucks or less so why not try it, right? and im going to need a new filter soon anyway so i'll just get a K&N so i dont need to buy any more filters.

[Srabai47]

hey guys i got a '93 k1500 with the 350 in it. i was wondering what you guys have done to increase mileage. so far I've done the air lid flip and i have noticed a mileage gain, around 1-5 mpg. if i switch to a drop in K&N Filter, would there be any gains? i know it will be minimal, but worth a try, right? the other thing is that if i do the air resonator delete mod and run a straight tube to the inner fender is there gains there? what about changing the timing on the distributor? any power or mileage gains? the headers and full exhaust setup is to expensive for me right now, but it will come. also, do throttle body spacers really work? any gains? and I've seen the spacers for the jets in the throttle body that claim 5-10 HP gain over stock for 12 bucks on eBay. any truth to that?? any info would help!!!

are you on crack? flipping the lid may gain .5+/- mpg and you say 5mpg? with that logic i should be getting 19-24mpg in my 94 c1500. as for the spacer verdict is that they are useless. and are you trying to get power gains or mpg gains? 2 different things. K&N is nice for the sole purpose of never replacing it again. minimal gains. and the timing, let me get back to you in a few weeks when i burn the rest of my tank. be ready to swap the motor if you time it wrong and blow it up though.

[94x4 blazer]

are you on crack? flipping the lid may gain .5+/- mpg and you say 5mpg? with that logic i should be getting 19-24mpg in my 94 c1500. as for the spacer verdict is that they are useless. and are you trying to get power gains or mpg gains? 2 different things. K&N is nice for the sole purpose of never replacing it again. minimal gains. and the timing, let me get back to you in a few weeks when i burn the rest of my tank. be ready to swap the motor if you time it wrong and blow it up though.

well then negative nancy, oh queen of all things engine. please fill all of us ignoramuses in on the magical way to improve mileage.

[ABNSTEPSIDE]

the way i always looked at it was its a full size truck you cant really expect a lot out of it..but everylittle bit helps the pocket. i never run k and n filter they are gravle filters they let in fine stuff that's how they let more air in is because the pours ar bigger dont let anyone else try to tell you differnet i have seen many truck destroyed at silver lake because sand will pass right through them i have personally pulled the motor apart from a buggie that was only ran at silver for one summer and the walls were scared to **** and sand was in the intake. get rid of the mechanical fan and put on an electrical fan. advanced the timing 4 degrees and no more and dont forget to unplug the wire under the passenger side dash before you try to time it. its a little brown wire if im correct its been a while since ive done it. but i have done it to about a dozen differnet trucks and all of them run fine. if you go to much you will have detonation and then your going to beat yours bearings to death. and ive always found the best way to save fuel is general maintenance and keep a lite foot.

[ABNSTEPSIDE]

oh and flipping the lid does absolutly nothing doing so lets warm air in from the engine in and actually makes thing worse so flip it back over.

[Srabai47]

well then negative nancy, oh queen of all things engine. please fill all of us ignoramuses in on the magical way to improve mileage.

magic fairy dust. havent you heard of it? they sell it at all fine auto parts stores. just go in there and tell them your an ignorant ****. they'll know what to get.

[Doober]

Spacers help with wet flow systems, you're thinking of a dry flow like a Vortec.

-TBI mods, flow matched injectors, proper fuel pressure
-TBI spacer
-Longtube headers with 2¼" exhaust
-Properly functioning EGR (doesn't deserve the bad rep it gets)
-Tune with more timing in the high vacuum areas, lean cruise if possible

That's about the extent of your available modifications without opening up the engine.

[GreaseDog]

Spacers help with wet flow systems, you're thinking of a dry flow like a Vortec.

-TBI mods, flow matched injectors, proper fuel pressure
-TBI spacer
-Longtube headers with 2¼" exhaust
-Properly functioning EGR (doesn't deserve the bad rep it gets)
-Tune with more timing in the high vacuum areas, lean cruise if possible

That's about the extent of your available modifications without opening up the engine. FINALLY! Someone who actually knows what they're talking about!

I tinkered a bit with my 92 C1500 scsb with a 5.7 and a 700R4....

3.42 gears 235-75-15 tires, 100% stock engine and trans.
Modifications:
Full tune up, cap, rotor, plugs,wires, fuel filter, pcv, all ac delco parts.
EP-241 Ac Delco fuel pump (92 5.7 TPI Camaro)
Flowtech 11504 headers and y pipe, mandrel bent 3"single exhaust, Flowmaster 3"40 series muffler.
k&n cold air intake.

Only thing not per factory specs was the plugs gap, I found that my truck liked the plugs gapped at .055" rather than factory spec.

This setup brought me 20mpg mixed city and highway driving for several tanks.

[Doober]

Heh heh thanks, I take that as a complime t to a currently drunk person :D

The only full tank measurements I got from my 100% stock truck (4.3/4L60/3.08s/28" tires) were expressway, and that was 24.5mpg from Flint, MI to Tucson, AZ. The only 'mod' was an MSD coil that I already had, I'm not sure if it contributed or not.

[hewdamwright]

tbi mods is bull @*%$ throw that choke tube away move the coil cut the sids off the stock breather drill a holein the bottom of the breather vent tube and you have direct air to injectors for nothing set your timing to stock settings get some mid length or shorty headers cheaper easy to install less heat on starter and a y pipe and good cat back system be happy with a little for less because after that its inside the engine and then some real timing and fuel changes that sounds like your not ready financially for

[Doober]

Care to add a couple commas and periods there? So you're saying that ridge doesn't affect the airflow at all... small wonder my 454 throttle body doesn't have them. Stock base timing isn't enough on a TBI engine, advancing the distributor 5-7 degrees won't hurt it, I drove a bone stock '91 Sonoma that ran much better after advancing the timing, and it ran like that for 70,000 miles+ until I sold it.

[phoebeisis]

Boy if I had any sense I would stay out of this, but since I don't.....

In general there aren't any simple,cheap add on modifications that will improve PART THROTTLE FUEL ECONOMY and a modern vehicle with electronic controls.And even thew Throttle Body 93 had electronic controls-probably a mass air sensor probably O2 sensors .
The OEM engineers aren't fools-they are better than the aftermarket engineers.
Yes they do have restrictions-noise and emissions- but those limit peak power more than part throttle FE.

What works
1) Change in driving style-pulse and glide in city driving. GM trucks have transmissions that are perfect for that-they glide at low speeds with very little engine braking if you keep it in D and just lift off gas.
2)Slightly lower hy speeds-these vehicles are bricks-with CDs over .45-drop from 70 mph to 66 mph- put it in cruise control(except in hills mts)
3)Get rid of excess weight-some folks take the 3rd row-77 lbs- out of Suburbans if they never use it.
4)Keep tire pressure up-maybe to side wall max not door numbers.
5)If you don't need AT tires use all season-usually lower rolling resistance. If you need AT well get the lowest RR all terrain.

In general pulse and glide-in D- is worth about 15% in pure city driving-maybe 1.5-2 mpg.
Charlie

[1993-Sierra-Z71]

0.0 i haven't checked this in awhile... i still have the lid flipped all the intake junk is gone and i pulled the liner off the bottom of the hood and i gave the headers a nice tight wrap of heat wrap.

[rabbiporkchop]

I am yanking out my tbi and replacing it with a 2002 lm7 for an extra 100 horsepower and 1-2 mpg.

[elwaupo]

Boy if I had any sense I would stay out of this, but since I don't.....

In general there aren't any simple,cheap add on modifications that will improve PART THROTTLE FUEL ECONOMY and a modern vehicle with electronic controls.And even thew Throttle Body 93 had electronic controls-probably a mass air sensor probably O2 sensors .
The OEM engineers aren't fools-they are better than the aftermarket engineers.
Yes they do have restrictions-noise and emissions- but those limit peak power more than part throttle FE.

What works
1) Change in driving style-pulse and glide in city driving. GM trucks have transmissions that are perfect for that-they glide at low speeds with very little engine braking if you keep it in D and just lift off gas.
2)Slightly lower hy speeds-these vehicles are bricks-with CDs over .45-drop from 70 mph to 66 mph- put it in cruise control(except in hills mts)
3)Get rid of excess weight-some folks take the 3rd row-77 lbs- out of Suburbans if they never use it.
4)Keep tire pressure up-maybe to side wall max not door numbers.
5)If you don't need AT tires use all season-usually lower rolling resistance. If you need AT well get the lowest RR all terrain.

In general pulse and glide-in D- is worth about 15% in pure city driving-maybe 1.5-2 mpg.
Charlie

I have to agree with this one. Baby the throttle, run light and keep the tire pressures up. I don't run ATs unless needed as most of my driving is on the blacktop.I have a 95 4.3 K1500 extended cab that I can pull over 20 mpg, hard to believe but true.

[phoebeisis]

GM's with that 4L60E glide like no ones business.
If I lift at 35 mph-it will carry up and peak at 37 mph-and it will take 30 seconds-roughly 1/4 mile-to glide down to 28 mph
This is how I run it in city driving with 35mph limits

[ChevyVan]

Pretty cool stuff to know...I never knew that about the 700r4 tranny...when my fuel pump went out on me just after a take off I was still in drive and was able to coast on a flat road almost a half mile...before the engine quit a was going around 45mph...other cars I've had in the past would seriously slow down if the engine stalled...I remember that about my El Camino I had...it would not coast very far in drive or neutral if the engine was off.

[todd1969]

I have to agree with the GLIDE abilities of these trucks. With very little throttle, and in any gear, take foot off throttle and it just rolls on and on. This is the 2nd GMC from 1995 I've had with the 5.7 engine and the 4l60E trans. The other one would glide forever too.