Gas mileage capabilities (Gen 1/2 SBC vs Gen 3/4)

[9kredline]

As everyone knows the LS series motors are capable of mid 20s in the city and low 30s on the highway.

 

However, I was wondering, couldn't the Gen 1/2 small blocks with a proper EFI system (Megasquirt or similiar for Gen 1, modified stock for LT1/4), similar flowing heads, and a similarly weighted/lightened rotating assembly with a T56 accomplish the same numbers?

 

I guess I just feel if you applied the same technology you could get very similar results. Opinions? Experiences?

[that240guy]

the problem with the cheaper stand alone ecus is that you are not going to get the great gas mileage out tof them that you might desire. They are awsome for making all out power and for driveability, but they don't have cruising tables whereas an LS1 or LT1 computer has tables that will slowly continue to lean out your engine to a point where the computer thinks its safe.

 

I am not sure what you were trying to say about the LT1 fuel injection, but it would be almost impossible to adapt LT1 injection to an old SBC. The LT1 recieves its injector firing signals from the optispark distributor that has a 360 degree optical wheel in it. They work great, but you wouldnt be able to retrofit an opti to an SBC. You might be able to design a wheel that you could attach to the crank and run it like that.

[9kredline]

I am not sure what you were trying to say about the LT1 fuel injection, but it would be almost impossible to adapt LT1 injection to an old SBC. The LT1 recieves its injector firing signals from the optispark distributor that has a 360 degree optical wheel in it. They work great, but you wouldnt be able to retrofit an opti to an SBC. You might be able to design a wheel that you could attach to the crank and run it like that.

 

No no no, I didn't mean adapt the LT1 fuel injection to the previous generation, I was just mentioning modifying the stock FI on the LT1/4 motors to increase the mileage.

 

I was just thinking about buying an already converted S30 eventually but getting the best bang for the buck since gas is won't be getting any less outrageous any time soon.

[zeeboost]

the problem with the cheaper stand alone ecus is that you are not going to get the great gas mileage out tof them that you might desire. They are awsome for making all out power and for driveability, but they don't have cruising tables whereas an LS1 or LT1 computer has tables that will slowly continue to lean out your engine to a point where the computer thinks its safe.

 

I am not sure what you were trying to say about the LT1 fuel injection, but it would be almost impossible to adapt LT1 injection to an old SBC. The LT1 recieves its injector firing signals from the optispark distributor that has a 360 degree optical wheel in it. They work great, but you wouldnt be able to retrofit an opti to an SBC. You might be able to design a wheel that you could attach to the crank and run it like that.

 

 

You should be able to run a standalone more lean than you would with a factory PCM. From what I understand, running over 15.5:1 air fuel ratio will shorten the life of the catalytic converters, so they're programmed not to run that high. Also, I thought most standalones allow you to run closed loop with target AFMs. Correct me if I'm wrong...

[Z48LT-1]

I would be somewhat surprised to learn that the original GM PCM couldn't be tuned to give that kind of mileage on a reasonably-cammed LT1. Implementation of this trick is left as an exercise for the student, as always.

 

Cheers -- Gary

[bodie]

the ls series has so many improvement built into the motor it self that it would be really hard to get that kind of milage out of the lt series or gen 1

the ls has

lighter valve train componts , almost fragile

lighter pistons

gundrilled cranks

the heads flow and scanvage better

and the cooling system keeps every thing and an optimial temp, and does flucatuate as much.

not to mention the the ecm is faster and better able to control fuel

 

short of building a race motor with light componts a really mild cam and a late model pcm it willl be kinda hard to simulate the same results

[280zwitha383]

the ls series has so many improvement built into the motor it self that it would be really hard to get that kind of milage out of the lt series or gen 1

the ls has

lighter valve train componts , almost fragile

lighter pistons

gundrilled cranks

the heads flow and scanvage better

and the cooling system keeps every thing and an optimial temp, and does flucatuate as much.

not to mention the the ecm is faster and better able to control fuel

 

short of building a race motor with light componts a really mild cam and a late model pcm it willl be kinda hard to simulate the same results

 

Except for better flowing heads (atleast better flowing than earlier stock small blocks) the rest of the points are marginal IMO. The best thing going for it from the list you've mentioned is the lighter rotating assembly and that could be compensated for by better tuning (and if what was said earlier is true then not running cats could further help out).

I agree that it might be hard to simulate and the pendulum of the argument may be just that. How practical is it to attempt this? It would seem if cost was the issue you may as well start off with an LSx style engine. A standalone fuel injection setup would probably cost more than buying a complete jy LS engine unless you pieced it together yourself.