CougarL92

iTrader: (6)

I am just curious if anybody on here has a direct comparison on a higher compression LS1. Say 11:5:1 and up..One dyno with pump gas another with race gas and what was the result. One of the reasons for me asking is, that I have a L92 TEA headed 416ci motor with 12:6:1 comp that actually runs well on pump 93 oct gas on a daily basis. No issues that i'm aware of as far as detonation. Car made decent power on the only trip to the dyno with 50 miles on the motor 533 RWHP SAE with tuning issues that have since been fixed...Now the motor has about 1100 miles on it and has loosend up quite a bit. This weekend I tossed in 5 gallons of 110 oct and it felt like the car had a diffrent motor in it. Much more powerful and the motor sound noticably more crisp. I'm wondering if I really need some higher octane in there at all times.

allngn_c5

iTrader: (3)

I'll bet on 93 octane your computer was pulling timing. The fact that the car has 1100 miles should make it feel faster as well. Not sure what else to say, but I bet you make an extra 50 rwhp on 100 % race gas. All these lil turbo'd ricers make a **** load of extra power running race fuel after being reprogrammed for race fuel that is, so it makes sense that a high compression big cube motor would make more power too .

WS6FirebirdTA00

iTrader: (33)

Higher octane will do the opposite. It is harder to ignite. Unless your car was getting a lot of knock or your fueling was messed up, then I would say it was all in your head.

You are not going to benefit any more from a higher octane if you do not need it.

allngn_c5

iTrader: (3)

[QUOTE=allngn_c5]I'll bet on 93 octane your computer was pulling timing. QUOTE]


I was taking a stab at his question. I know that better fuel won't do anything unless the motor requires it. I was assuming that he was missing some timing due to knock running 93 octane at 12.6 to 1 comprssion. My car is 11.4 to 1 compression and it would knock like crazy if I didn't use a good source of 93. Any higher compression I feel I would need more octane to keep it from pulling timing due to KR.

Frost

iTrader: (45)

No way. His car was tuned on pump. Even if it wasn't..... No way.


[QUOTE=allngn_c5]
Doesn't matter if it does knock; all it's gonna pull in PE is a max of 4deg (stock table value) if seeing knock. That's not gonna cost him anywhere NEAR 50whp

allngn_c5

iTrader: (3)

I am betting his car is not anywhere near max timing at that compression on 93 octane, and it is still pulling timing. SO the 4*'s you mention plus the 10-12 *'s left on the table probably would yield at least 30 or so. I think you missed the fact that I was comparing his tight fresh engine's numbers to his current feeling about the engine now that its broke in and had the race fuel. Not sure, I don't have his tune in front of me and his car hasn't dyno'd with 100% race fuel since he's gotten broken in.

edcmat-l1

iTrader: (10)

We've done some high compression testing with pump and race gas. If you're not tuning for it, you wont make any more power with higher octane.
And as mentioned earlier, if your motor doesnt require it, race gas wont make a diff. We hear it all the time too. "It sure does run better on 114" from so and so runnin a 383 at 10.5:1
That being said, I could see this vehicle in question, runnin 110 keeping the burst knock out of it, along with the PE KR out, and actually making some more power (I dont know about 50). Its right at the compression level, that if the tune was pretty aggresive to begin with, there may be some to be gained just by adding high octane. The only way to tell is on the dyno, and data logging.
BTW, be careful runnin leaded fuel, it'll ruin your factory 02s. QUICKLY.

allngn_c5

iTrader: (3)

Hey edcmat-l1 thanks for the input. Good post.

edcmat-l1

iTrader: (10)

I've seen 3 degrees make 20+ HP. It dont happen often, but I have seen it before.

edcmat-l1

iTrader: (10)

Thanks. And your welcome!
We have the benefit of seeing alot of diff performance vehicles, not just LS based. We see a fair amount of BBCs and drag cars.
And to add to post #7, 2 degrees too much timing can lead to 10 degrees of KR. So, in a situation like this, the fuel could make a difference of 25 deg or 15 deg, tappering up (KR tappering down). Even if the PE KR is only 4 deg, when you nail it and the burst KR instantly pulls 8-10 degrees, and then tapers off, with the 110 octane, if it kept it from doing that, you would def feel it.

Frost

iTrader: (45)

I've never seen anywhere near that on a non-boosted LSx; though I don't doubt your word at all.



Wait, race fuel isn't gonna stave off burst KR since burst KR isn't based on any event such as a knock sensor; it's a static table and from 3.2K rpms it can pull only 4 degs moving down to 2 deg by 4.4K rpms... It's only based on a dynamic cylinder air table and an enable threshold vs. rpm though, so it's easy to get worked out in the tune. Burst KR is "knock-anticipation.


I digress; I was just trying to point out that a vehicle tuned on pump gas is not gonna have a large gain moving to race fuel. As a matter o fact it should not truly be perceptible.

edcmat-l1

iTrader: (10)

Thats correct. But, when you get into the throttle hard, part throttle stabs, its this table thats crankin 10 degrees of timing out, without even so much as a ping. I've zeroed the burst knock tables JUST TO EXPERIMENT, both on the dyno and street tuning, just to see what would happen.
Disclaimer: I use a 5 gas analyzer while tuning so I have a much better picture of cyl temps and detonation by monitoring NOX levels.
PS I can understand your point, in that the octane level may not even influence the burst knock retard. Again, what I've posted is purely hypothetical, being as the testing we have done with 93 verses 110/114 has not been done on LS based vehicles. Just trying to apply the info that we have gathered on other engines to this instance.

edcmat-l1

iTrader: (10)

I agree completely. If its tuned properly and NOT pulling any timing, you shouldnt feel a thing.
Higher octane does not = more power.

Shoulder Shaker

iTrader: (36)

Wow. You guys are a welth of knowledge. I'm still sitting here rubbing my head trying to understand what you guys have just explained to me. So good to have people like you guys ( and gals ) on this site. O/P Sorry for hijack. Carry on

waterbug1999

iTrader: (3)

LOL.. me too...

I know when I run 92 (~11.5.1 CR) the car does not like it that much. I throw in 100 and it idles better and better throttle response.

Hows that for knowledge! lol

brad8266

iTrader: (23)

my car seems to enjoy 100 octane unleaded

CougarL92

iTrader: (6)

I guess that what i'm feeling also. The throttle response sounds much crisper on 110 oct the motor even sounds better. I guess i'll just have to strap it down to the rollers once again and see if there a diffrence

AshWS6

iTrader: (5)

We dont see anything but marginal gains on 12:1 motors, so I cant see a 11 somethign wanting 110. Test it and see.

allngn_c5

iTrader: (3)

Your compression is 12.6 to 1....It runs well on 93 as a daily driver, but runs like a different motor with race fuel. I don't know how you get it to run so well on 93 octane with that high of compression. They told me 11.4 to 1 was about as much compression as I could run on my car without having to upgrade to a better fuel then premium 93 octane.

edcmat-l1

iTrader: (10)

The OPs motor is 12.6:1. So, as I stated earlier, depending on the aggresiveness of the tune, KR if the timing is cranked up in it, it may actually need the higher octane, and therefore make more power with it.
I agree that there would be no need for it in a 11:1 motor.