74u

iTrader: (9)

My recently built 416 is going to need a tune very soon. It has 350 miles on it running on my previous stroker tune and runs ok. Once I hit the 800-1000 mile mark I'll be looking to get a dyno tune.

Since the car will be my daily 20K miles per year, I was thinking how nice it would be to run 87 vs 93.

My questions are do you see any problem having it tuned on this fuel? How much power do you see it losing if successfully tuned on 87?

Combo:

LS3 416 (Wiseco -15cc with .045 quench) 11.2:1 scr
TEA TFS 225's
239/246 -- .623/.595 -- 113+2
Fast 92 opened to 95mm
100mm L'felter MAF
1.75"x3" FLP Headers

The car will occasionally see a 100 shot dry...when I spray it I would run it low on fuel and fill with 93.

What do you think?

1989GTA

IMHO your compression ratio is to high to be running on 87 octane.

74u

iTrader: (9)

I know it's not apples to apples, but I (and many other) drag racers felt our liter bikes ran just as good if not better on 87. These bikes were all in the 11.5~12.5:1 scr range.

I think my cam spec's are going to play a huge part in determining feasibility...but I'm not that skilled

lil john

In general 9.5 or less compression 2 run 87 octane. With alloy heads even less with cast iron.

74u

iTrader: (9)

Based on what? Not saying I disagree...just curious why?

lil john

KNOWLEGE... go look it up.
Just something I no... Basic engine building
Intake-Fire- Compression & Exhaust..we have 2 know @ what compression will the engine fire a lesser grade of fuel.

lil john

Lots of reading & wrenching in my younger days. Now 37

lil john

Heres 1 for U?
how could some1 I no run 13 to 1 comp. on pumpgas with a 355 iron head engine.
Donkey D*** cam.
FACT.


catch you all in the mourning.

74u

iTrader: (9)

That's my point.

I'm just thinking these stock motors are getting away with as much as 10.8:1 with a "regular" fuel rating. The cam they run must have less tendency to bleed off compression than mine, right?

https://ls1tech.com/forums/conversio...ification.html

CAMSTER

iTrader: (10)

Solution:

Prius C for dd will cost only $1,346 to drive 20.000 miles a year based on 52 mpg average @ $3.50 a gallon / 87 octane.

Wana see a pix of my Prius C ?

Yep, savings pay for the Prius.

Problem solved...worked for me !

lil john

Correct yet the ECU does the most part of controlling things, other than cylinder press. Ole schools just over cam it 2 bleed of cylinder press.
oh yeah try a new engine with iron heads and C if you can get 87oct to run. Alloy hold less heat... That is 1 reason 4 higher compression ratios.

JakeFusion

iTrader: (7)

I'd keep compression around 10.1:1. From a DCR perspective, 93 oct can handle 8.7:1 pretty cleanly and 8.5:1 safely. 91 octane drops that all down to 8.3/8.0. 87 would be even more dramatic. So you'll have to figure probably a DCR of around 7.0 safely and maybe 7.5 pushing it.

redtan

iTrader: (5)

Even though it's cheaper to run 87 octane on a low compression engine, you will most likely get more MPGs out of a high compression engine running 93 octane.

So in the end, it's basically a wash when it comes to cost of gas. Except the higher compression engine will make more torque and drive better.

74u

iTrader: (9)

I thought about that. Lower octane needing more fuel to run the same...if true then it would not be worth it.

Looks like to consensus is 93...oh well.

redtan

iTrader: (5)

It's not that it needs more fuel, that's based on engine air needs. An 87 octane engine will need the same amount of fuel as a 93 octane engine.

It's the fact that a higher compression engine will make more torque from the same volume of air and fuel, thus you will need less throttle input to keep the car going at speed. So basically it's more efficient, does more with the same amount of gas.

VGLNTE1

iTrader: (1)

10-13k on a motor and care about 2.00$ each fill up plus loss in power?? Is this Ashton kutcher?

redtan

iTrader: (5)

That's a whole 'nother thing, didn't even want to go there yet.

74u

iTrader: (9)

Every little bit add's up, but my main reason is I resent paying so much for fuel as it is.

Bottom line - I asked a tech question...your opinion about my spending habits aren't what's important

If it could be tuned safely and with little consequence on 87 I would do it in a second...H/C/I 416 on street tires ought to be ok even if it loses a couple HP.

redtan

iTrader: (5)

And it was answered accordingly. Unless you have a specific hard-on for 87 octane, you are better off going with the compression to run 93 safely.