RNS-11Z

0% difference for me between usa93/aus98 pump and ms109 @ the track. That's on a tuned/ header combo.

mthis

I had very similar results.
race gas works ms109 works. its like crack for this car.

Wobble64

There are so many things that can make a difference when running our cars. I personally did not feel a difference on a road track when starting with 93 octane and switching to 100 after a couple sessions.


The best would indeed be to be able to monitor whether the car starts to knock and is pulling timing. I wonder whether DashCommand or Throttle could help with that.

mthis

I have logged it also with zentronic Dashdaq system and it does add more timing .

Mike450

Don't mean to call bs on you, but no, that's not better than a log.

If you're gonna claim timing advance , you can't dispute a log that shows it. There are plenty of variables that will effect a trap.

I'm gonna assume you're not running a dedicated fuel system either, so mixing the 100 with your remaining 93 and driving thru the pits to the starting line isn't exactly flushing a true 100octane to your rail.

I'd still like to see your slips though, as they should show the highest corrected trap of any stock C63 to date, if what you say has a chance at being accurate. Any 93oct run car should be a full 3mph off your best slip, at minimum.

mthis

Good tires ( use of drags radials) and leaving the car in sport what can make the trap speed change .

roadtalontsi

11:1+ is high compression a normal sequential port fuel injected engine. I never said the 156 is the highest or badest of them all by anymeans. Hell even old *** honda's have ran more in the past but dont argue that it is low or non performance. Mazda has been running direct injection for a long time and you can run much higher compression with that. Just like diesels in the 20:1+ club. With direct injection you can have multiple combustion cycles in one power stroke it's a whole different world of technology. It's also true that europe/other countries have way better fuel quality. Our gas isn't half the price just because we are usa and use so much - get the sams club discount. They get alot different engines over there because of it that can do lean burn cycles that get substantially more fuel economy because of it.

Yes higher octane does burn slower this allows you to start the combustion event earlier. Typically any higher compression or boosted motor will not reach maximum brake torque before detonating with 93 octane, meaning there is power to gain with additional octane. Yes higher octane makes less btu's meaning you'll consume more fuel to make the same power - not sure why that was even brought up - kind of a given. This is why e85 cars consume approx 30% more fuel because the octane is so much higher. The quanity of fuel is minimum and ecu can compensate for that as it's well within 5%. I agree anything over 100 octane probably has no futher gain as the stock ecu has probably given all the timing it will with a stock tune, but its not going to hurt either. Just stay unleaded if you like your oxygen sensors.

BLKROKT

Ran the tank dry. Here's my spreadsheet.

Wobble64

Blkrokt,


thanks for sharing - that is a helpful data point!

BLKROKT

Yeah, I am pedantic about data. Always have been - have all my runs for every car I've owned with DA, notes, etc on a spreadsheet going back to 2005. I like to know EXACTLY what changes/mods work and what doesn't work.

I don't know if I have a 113mph car, because those were the only passes I ran it on 93 octane. Every other pass was on 100 octane gas, and every other (22 total) was in the 116's.

Have seen similar results on race gas with my old 996TT, but of course boost changes everything...

Mike450

This data;


What you have above is a spreadsheet of results that could be attributed to many variables.

Gerry_M

Nice. 3 mph on MS109....isnt MS109 105 octane? I assume this was still stock as the mods list looks to be just plugs.


I understand what you are saying , although that data is also subject to interpretation and how each individual graph affect each other, or you could be missing some data point that you did not or could not measure. I enjoy the car by how it feels and how far it goes. Does not all that data secondary to just how the car drives.

Wobble64

Mike450, in case the chart you shared was intended to contribute to the question at hand - it is not legible. What does it show?
If not, then Blkrokt's spreadsheet is still the only actual datapoint in the thread.

BLKROKT

What exactly are these "many variables" you speak of?
Same day, same mods, same conditions, runs done 18min apart. The only change was switching to race gas.

I would data log it next time at the track on Thu (first time this year with my winter mods), but I have exactly zero interest in running pump gas. Take it or leave it. I think there are enough people who support this, and enough real-world experience shared by others.

BLKROKT

SPECIFICATION SHEET FOR MS 109
(Typical Values) Specific Gravity: .722 @ 60°F
Oxygenated: Yes
Color: Clear
Motor Octane: 101
Research Octane: 109
R+M/2: 105
Reid Vapor Pressure: 6.17
Oxidation Stability (min.) 1440+
Distillation:
10% evap @ 147.0°F
50% evap @ 167.8°F
90% evap @ 213.3°F
E.P. @ 263.8°F
Production: Elmendorf, Texas USA
Availability: Sealed Drums
Rev: 02/04


You are correct. Only changes I had made were plugs at that time from my prior runs.

Mike450

What I posted is not a c63 dataview, only an example of what data you would use to evaluate a mod and it's effect on performance.

Data like shift points, timing, knk, iat's, MAP, clutch slip, etc ... all of which are variables that will determine how fast you get down a track and give you a view into why you ran what you ran.

Did your car shift at 7krpms in 1/2 or 3 gear, or did it shift at 6700? Did the TCM invoke torque management in 2nd gear? Did you have an unusual IAT on your first run that resulted in stKnk? Did your 113mph run see 4 degrees of STknk from a the not so-93 octane you were running?

You won't know any of that if you don't log, but you'll be faster/slower because of it. And most of it has nothing to do with fuel.

There are broad effects from the most minuscule variables that a PCM or TCM sees, that can results in significant changes during a measured event such as DR. That's all I'm trying to convey here, but I see some feathers are rustled. I apologize, that is not my intention.

Wobble64

All great questions and points. However, the best way to get from opinion to knowledge is by getting the facts. Who can do the research and get a comprehensive set of data?


I'll sponsor - a complete test report gets a case of beer! There you have it, the gauntlet is down!!

BLKROKT

Oh yeah, great idea!
Who wants to go pound the **** out of their car on pump gas because we think they knock on the top end so you have to continually redline the snot out of it and datalog your results?

........crickets.

Mike450

Why would anyone do it? Because it would take the "we think" out of the whole discussion.

As a true self described "pedantic" data person, one would believe it'd be data you would like to see. As far as I can tell, it'd be the only data actually.

Wobble64

Blkrokt,

now we are being a bit dramatic aren't we?


Those engines are able to deal with a lot of abuse without damage - timing and AFR is just two parameters it can work with. If you throw in real crap and a cylinder cannot be stopped knocking, the engine actually turns that cylinder off.


So, not really a risk, but work it is. And useful it would be......

BLKROKT

Tell you what. Since I'm not going to waste my precious limited runs at the track, I'll be the guinea pig and datalog on the road. Can I do this with my Autoenginuity or DashCommand? If someone knows how, I'll do it this week.

Wobble64

Blkrokt,

Great! Not sure about the tools you mention, but why don't you play with them some and I'll try my luck with Torque.

Maybe we can come up with something that way. I am actually curious to learn about this. I may also be able to get some things out of MHP (for example help in interpreting some data we collect). I have a good connection to them.

Mike450

Waste your runs? Why do you think its called a T&T (test and tune) night? ..lol

BLKROKT

Because a) I don't get to the track much, it's 2.5hrs away if I'm lucky with traffic, and like to run my best every run; b) If you've ever been to Atco or ETown here in the Northeast, you know that runs are precious as you only get a few; and c) because this Thu is a grudge match against my old friend in his Mitsu GSX running mid-11's, and I have to make every run count for bragging rights

TAILWAG

Not to be argumentative, but, even though times do not lie, you really can't claim that results on a given day/conditions and a result of a 3mph gain is consistent with switching gas.

I have ran the same car, back to back without changing a darn thing, and gotten different times/speeds...an awesome launch vs. a good launch again can yield differences of 0.2-0.4 seconds and traps of 3-5mph...

Just my 2 cents.

Carry on.