Re: Octane Boosters

Mike, The owners' manual on my 350 Trans Am (LT-1) advises that low octane gas can be used, but it would be "compensated" for, by the computer. The book says to expect a drop in performance, using low octane gas. If you can boost the octane rating of your gas, I might expect that the situation would become the opposite. If so, then maybe you *could* feel an increase in performance, using an octane booster. Octane is a measure of how enthusiastic to burn that your gas will be. High octane gas burns much slower and cooler than low octane gas. In a high compression engine, low octane gas will burn even before the spark can fire; it ignites from the compression and heat in the cylinder. The result is "pinging"; your pistons are not being pushed, they are being driven by hammers - and the "timing" is 'way too advanced. Serious engine damage could result. The manual seems to say that the computer can avoid this damage (not sure that I really believe that), by dialing back the performance. High octane gas in that same engine would not detonate prematurely like that. The cylinders runs cooler, and the gas waits for the spark to ignite the mix. Then it burns at a reasonable rate, not as an explosion. Now the timing is correct, and the high compression produces serious horsepower - by using *less* powerful gas. If your computer senses higher than regular octane, it should then (by the owner's manual) dial up a noticeable increase in performance, over low octane gas. In older cars (with no computer), the only thing that octane booster could do for you is to stop an engine from pinging. Unless the pinging problem was so bad that the engine was running rough, you'd probably never feel an increase of performance, in an older car using octane booster. Maybe that is why drivers say that octane boosters do not increase performance; now, with computers, octane boosters might make all the difference. IMHO. Personally, I use the highest octane gas that I can find. Hey, I do this driving bit for *fun*. After paying the price of the car, I'm not gonna give away any fun, just for pocket change.

I've done tests with 87, 89, 91, and 91+booster (forget the octane on that) fuel in my dad's '94 Z28 with a cable connected to a laptop and the ECM. During hard acceleration, I logged the data (most notably the spark advance/retard) and compared them all when it was all said in done.

The results? 87 is certainly quite doable for the LT1, but does incur a notable amount of timing retard compared to the other. 89 has a very slim amount more retard than 91. 91 and 91-boosted are identical.

The LT1 will retard when it senses knock, but won't advance on its own beyond its preset. It honestly has no idea what octane you're feeding it. So if technically you set it up to not ping on 87... ;)

Milhouse

Oh yeah.....TRULY scientific results.

Sorry Milhouse, but you're wrong. And so is that idiot Red. Why is it people are so freaking ready to pass out bad information. I would love to see your control conditions, your method of testing, atmospheric density, tire compound and wear, etc...

And Octane is not...how did Red put it, "a measure of how enthusiastic to burn that your gas will be." That's just wrong, and if you believe him, you deserve whatever happens to your poor powerplant. If you want to know what Octane is, do a google search on some of my old posts or simply go look it up.

I dunno....I may just stop posting altogether and let the inmates run the asylum. I'm sick and tired of correcting bad information.

Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna

Milhouse, I would certainly like to be better informed, like the man said. Sure, I know the chemistry and physics, but I am on vacation here. :-) Can you tell me what else your laptop monitored, besides spark advance? I can imagine the computer changing that, to avoid knocking, plus maybe a few other things. It seems reasonable to me that each of these changes would decrease performance a bit, but I doubt that the computer would or could do everything imaginable. I'd also like to duplicate your laptop testing ability, for my use. Can you give me a list of components? I realize that the results will be subjective, but testing usually is, to some extent. It would be good to know what is best, for the car and conditions that I drive. Reply off-line, if you wish.

Blah, my dad and I did this years ago...the raw data is long gone, or I'd post it all. (Let's put it this way, my dad's P233MMX Thinkpad still had a working battery then...)

The cable is a unit from

- that site is really all you need, they've got the cables, the kits if you really want to do it yourself (though I recommend just letting him do it, heh), and links to the software.

Again, it's been a long time, but IIRC we used FreeScan... a screenshot of the data it can capture is here:

Milhouse

Christ man, I never said it was the be-all and end-all of testing. That would ideally involve a good amount of track time as well and better datalogging than an old Thinkpad and a cable.

If it makes you feel any better...the runs were all done at night in AZ (70-80 deg F, very low humidity)...at the time, factory-stock '94 Z28 M6 (it since has a K&N FIPK, LT4 knock module, TB bypass, MSD coil, and a modified shifter...and a failing OptiSpark) riding on BFG Comp T/A ZR's. It was never intended to be an ultra-scientific test; that would be more like the one Car & Driver did in 2001

withmultiple cars, a dyno, track time, and draining the tank both when receivingthe cars and then when going from 87 to 91. The runs were from a slow roll,0-5mph, to roughly 60mph; go out when it cooled off and there'd be littletraffic, wind it up a bit a few times, come back, and check the numbers.The exception to this is the 91 vs >91 octane (sometimes it was 91 withbooster added in; others it was a few gallons of Turbo Blue 104 on analmost-empty tank of 91) which we did get a few track runs in as well.These were all spread out enough so that the tank was nearly empty and thenfilled up with the octane we wanted to test, then driven for a day or two,then tested.

I never said it was a good idea to run 87 in an LT1. It won't grenade, or even cause drivabilty issues at your average (i.e. non-WOT or close to it) speeds, but the computer is keeping the timing back from where it likes to be, and you're certainly losing performance. I'd only run it myself assuming a) I was actually driving the Z28 and b) I was stuck in the middle of Buttfuck Nowhere, USA and all they had left was 87. 89 behaves much better, but the price difference isn't worth the fact that you're still not doing anything good for your engine. 91 is certainly the way to go. The 91 vs

high-RPM retarding from the ECM, even after installing the LT4 knock module. Maybe it's an oddty of that particluar red and black '94, but the logged timing numbers for (what were sometimes back-to-back runs) 91 and >91 were always identical. Zero performance increase down the track.

My '70, on the other hand...well, I'm just very careful to make sure I never end up in Buttfuck Nowhere, USA, where they only have 87, because I figure I'm pushing it with 10.2:1, Vortecs, and 91 as it is.

Milhouse

Martin, Sorry if I did that so badly. Didn't mean to piss you off. The question was : Thoughts on octane boosters. I've got a 02 WS6 GMS MAS and air box along : with a K & N air filter and Corsa Cat Back. I've heard they are worthless : but I swear I can feel the difference big time.

After being told that octane boosters are "worthless", he still says that he can feel the difference. (as opposed to no octane boosters, right?) Can you explain? Red

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GLK9MM wrote:

You didn't piss me off Red, and neither did Milhouse.

It's just obvious that this person is a noob and he's not getting the whole picture based on what you guys are saying. (Especially your response regarding octane.) And he's going to do damage to his powerplant, you can just feel it.

As far as his question, I can tell now that we are reading it differently. Grammatically, his question is contextual and refers to the previous statement regarding modifications, not octane additives. And I answered it as such. As far as octane additives...bah...he may feel the vehicle run a little smoother, but he's not really seeing a performance boost, not with the setup he described.

For the record....once again....octane is one of the MANY components of what we call gas...petrol...fuel...whatever. Octane is one of the heavier compounds in gasoline. For whatever reason...people associate octane with oxygen which is so completely wrong since octane is a hydrocarbon. (No oxygen in octane.) For obvious reasons, higher octane fuels have a different flash point than lower octane fuels. The level of octane (and whatever else you have in your fuel) should be a function of how you have your vehicle tuned.

'Nuff said...I'll give ya'll the last word.

Martin '01 Formula - MTI Air Box Lid, K&N Filter, Hurst-6, SLP Cold Air Induction & Smooth Intake Bellow Corsa Catback w/Premium Tips '83 V45 Magna

Well Interesting conversation. Some more info. Where I live in CA only 91 octane is available. I switched from Exxon to Philips 76 premium at the same time I added the octane booster. Also I thought the car to be a little sluggish on throttle response prior to changing gas brands and adding the octane booster. I had always wondered if either the sensors or computer was a little off then by adding some octane it compensated for that.

Thanks for all the response's

Mike

In your defense, the Highway and Traffic Safety Administration lists the Z as a premium fuel engine.

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98 Camaro

10.5:1, but it's also got aluminum heads and a computer with a knock sensor...

My '70? Uhhh...iron heads and blowby ;)

Milhouse

I was never trying to say it wasn't - the original poster was asking if he'd see an increase in power by adding an octane booster to his fuel. Myself, I've never seen the ECM in our '94 add any more timing than it does with 91 alone.

Milhouse

Just supporting the decrease you stated with less then Premo. No need to be defensive. Get it! I don't flame. Well, expect the extreme ricers, but that's cool.

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98 Camaro

91 is as high as you can get around here without paying for 100-octane race fuel. All most of that post was saying is that an LT1 can survive on 87 or 89, and that from what I can tell, they don't benefit from anything beyond

2. Milhouse

Hey, we're cool. :)

Milhouse

Just adding 2 cents..

91 octane should be about perfect for a WS6. If you want a performance increase using octanes like 100 no-lead, advance your spark with something like Hypertechs Power Programmer III, otherwise you aren't helping anything over about 91. The K&N is not as good as the Holley Blue PowerShot Filter because the K&N's surface area is lessened by the wax overlap residue when they make 'em, so any bonuses you get for more airflow are sort of lost by the smaller surface area of the K&N vs the Holley. You will never notice a difference in a 1Hp gain on a WS6 from these oil filters but they ARE re-usable and that's worth something. The Holley filter might be a little better. Please don't buy a air-restricting/swirling "Tornado" for the love of Pete!

Mike