Malobu

I'm looking to use a 2000+ LS1 for my 65 Chevelle. However, one thing I want to get away when doing this heart transplant is the current high compression on my SBC that requires premium fuel.

Does this limit my options to truck engines OR can the ECM control timing or (?) to allow mid-grade California fuel on any F-body LS1 engine with the higher CR's, i.e., 10:1?

Thanks!

cablebandit

iTrader: (37)

I would imagine so if it jumps to the low octane timing table or you create your own. I have a low compression turbo ls1...8:81 and i raised the timing way up from stock and run 93 all the time. Sometimes on a long trip though I will put in 87 just for the money savings and have no problems as long as I dont hammer it with 17psi of boost

jyeager

I tend to run mostly premium in mine ('01 T/A). I can run 89 octane just fine though. When the temp gets higher (90+) I can hear the mid grade ping.
However, the ping is handled by the computer and it will eventually switch over to the low-octane spark map. You will get best performance with premium, but you can always use lower octane.
If you really hate the idea of hearing any pinging and using the low-octane map in the computer then you need to lower the compression either by using a truck engine, or modifying the motor for slightly lower compression.

MrDude_1

iTrader: (4)

heres something funny alot of Fbody owners have noticed.


the price diff between premium and midgrade is minimal... but the gas miliage lost by running the low octane timing tables more then made up for the price diff...



so its CHEAPER for them to run premium, then it is to run midgrade and get worse miliage.

Oscar Will

I run mostly 89 octane with no problems, I have run 87 without hammering the throttle. My engine is all stock LS-1 internally.

lilbuddy1587

iTrader: (1)

You people buy a hi-performance engine and want the best performance possible but yet you want to use shitty gas ? Just to save a couple pennies and more than likely waste MORE money when you get shitty gas milage? You guys kill me.

B T

I use 87 all the time, can't tell a performance (time slip) or mileage (MPG) difference between 87 or 93.

13.50's and 20 MPG
Use your own judgement based on what your application is doing and your needs.

That's in the Texas heat BTW.

Just my .02

Ackattack1

iTrader: (7)

I can run 89 year round here in Washington where it doesn't get very hot. When I lived in Kansas I had to run 91 during the summer.

That's interesting on the fuel mileage thing. I might have to do a little testing of my own on that.

MrDude_1

iTrader: (4)

id highly encourage that.

i was told something similar from my former roomate with his vette... the vettes give real time MPG figures to work from... athough i dont really trust his word for much.. lol


but with the fbody people ive seen, its true...


if it was me testing, id also be running a scan tool (laptop) and datalog driving around... just so you can see how much timing is being pulled.

B T

A quick search yielded this information on 87 octane, I agree with Jimmyblue.














https://ls1tech.com/forums/showthrea...+versus+octane

Diolar Magnum

91+!!

Oscar Will

It seems that a popular misconception exists concerning this fuel octane question. Some people believe that a "higher grade" fuel (i.e. higher octane rating) is a better fuel and that a lower octane fuel is "shitty" fuel. In actuality, the only real difference is in the formulation that causes a fuel to be less prone to detonation with a higher octane rating. A lower octane fuel isn't just cheap crap that may cause your engine to run bad. You need to run the lowest octane that your particular engine can burn without detonating......putting 91 in an engine that doesn't NEED it is just wasting money and isn't doing the engine any favors

MrDude_1

iTrader: (4)

very very true.


now think about this.

your engine is a 10.5:1 compression motor with alot of timing. from the factory these cars came with aggressive timing..
the knock sensing and timing strategy is better then previous GM ECMs, however, it still pulls "extra" timing out when it detects knock..

that of course, hurts efficiency.
hence the mileage decrease.




if we were talking about a car that was not designed for premium, you would be 100% correct... but this one is made to get peak efficiency out of it.... that's why there's a diff.


believe me, ive had this same debate with alot of people and i agree with what you say.. alot of people foolishly waste money on premium because they think its better some how... really its just like low grade... but with more toluene.

Frizzle Fry

iTrader: (1)

Follow the basic concepts these guys did applied toward an LSx and you're well on your way...

Oscar Will

MRDUDE_!..............Amen brother!

B T

>>>>>
the knock sensing and timing strategy is better then previous GM ECMs, however, it still pulls "extra" timing out when it detects knock..

that of course, hurts efficiency.
hence the mileage decrease.



The only time it will pull timing is when knock is detected, otherwise it will not, driving at less than 50% throttle shouldn't cause any knock therefore keeping the efficiency that your talking about.
Even 12:1 compression in stop and go traffic and light cruising (HWY) the engine doesn't require or need high octane.(it's only wasting it).

I think we are splitting hairs here versus slight timing retard for MPG VS cost at the pump for all out performance at 100% of the time.(track duty)

The difference is very negligible at best.

I'm also using the HPP III tune with my 87 octane, so I must be getting some major ignition retard.

Everyone's setup (plugs/gaps/heat range/mixture/engine temp./tire size/ wheel weight/windows down/AC on/ect. ect. ect. is going to be a little different per car.

When gas hits $10.00 a gallon we should have this disscussion again.

Malobu

Thanks for all the replies. I only get about 16gpm when babying the throttle and about 12 at best when I "step on it" with my current carb set up...so yes, I'm looking for better mileage as well as lower octane rating requirement.

Luna

iTrader: (6)

It would be interesting to see in a controlled environment where you would get the best gas mileage reg. mid or premium

RXette

all you have to do to raise "octane" is to add a less volatile clean burning substance to the gasolene. a previous post said that the refiners use toluene. i use fuel injector rated twcIII 2 stroke oil. 1/3 oz per gallon, about a 400/1 ratio compared to up to 50/1 in 2 stroke fuel injected engines. i have used 87 octane in high compression engines with no problem. no knocks, detonation etc. better mileage. the twcIII also adds lubrication above the compression rings. $6/gallon @ walmart. it is specifically formulated for injectors. no spark plug fouling or clogging.

just my unscientific .02

dan

B T

Good read on octane---->http://www.gnttype.org/techarea/misc...explained.html

I found this link from another post by smokeydoge in another thread, Thanks smokeydoge.
Thread---> https://ls1tech.com/forums/showthrea...24#post2992324


Q: Why bother to boost octane at all since my engine can run just fine on lower octane fuel?

A: For a high compression engine to run on low octane fuel, the engine management system will need to retard the ignition timing to prevent preignition or pinging. Retarding the ignition timing means that the firing of the spark plug is delayed until a later moment in the compression stroke. It does not take much to see that a later onset of combustion means that the combustion is less complete, which in turn mean less power and poorer fuel economy. It is possible that the casual driver will still come out ahead in terms of saving money by using low octane fuel, but the retarded ignition advance also means a rougher running engine and a much duller throttle response. Thus octane boosting is not necessarily of interest to all motorists but rather the enthusiasts.