Topic: new to race gas (Read 842 times)

mjohnson · « **on:** July 31, 2009, 02:42:01 PM »

So I picked up 5 gallons of 105 today with hopes to run the strip tonight (provided the weather holds out). Have a couple questions though. Is it possible to have too much octane in a given motor? I'll be running the 100oct file but will also be running water/meth (60% distilled water/40% methanol). Do I syphon the 1/2 tank of 93 and run straight 105? or do I mix the two? and if I mix, is there a ratio I should aim for?

formulanerd · « **Reply #1 on:** July 31, 2009, 03:05:48 PM »

(ROCT*(RGAL/TGAL))+(NOCT*(NGAL/TGAL))

R = Race
N= Normal plump (aka 91)
T= Total
OCT = Octane Rating
GAL = # of gallons

if you want to run 100, you need about 2.7(3.5) gallons of 91(93) to 5 gallons 105.

1gal of 91(93) nets you 102.66(103.00)
2gal of 91(93) nets you 101.00(101.57)
3gal of 91(93) nets you 099.75(100.50)
4gal of 91(93) nets you 098.77(099.66)
5gal of 91(93) nets you 098.00(099.00)

1/2 tank in the mk4 is what, about 8 gallons? if you throw the race fuel in now with your 93, you're looking at 97.61 octane

formulanerd · « **Reply #2 on:** July 31, 2009, 03:35:34 PM »

now.... from what i understand a 5% mixture of methanol will raise octane by about 1 - 1.5 points.... if thats the case you're looking at 8-12 points in octane boost from the injection alone.

you say 40/60 mix... is that pure 100% meth taking up 40%? or 4 parts meth at 40% strength (like windshield washer fluid or something)?

mjohnson · « **Reply #3 on:** July 31, 2009, 03:43:16 PM »

pure meth

formulanerd · « **Reply #4 on:** July 31, 2009, 03:52:19 PM »

in theory, with 100oct file, the water/meth would render the race gas useless.

i'd say mix all the 105 with whatever is in your tank when you get to bandi... run the water meth, and you'll get the most out of that file.... personally i dont think you'll be running "too much" octane, or over doing it, but you may not get all the power out of it because you can't advance the timing anymore.... unless you have revo and an SPS or lemmiwinks, etc.

formulanerd · « **Reply #5 on:** July 31, 2009, 03:55:49 PM »

and if you have any issues, just kill your meth setup.

mjohnson · « **Reply #6 on:** July 31, 2009, 04:01:00 PM »

Thanks for the info. I'll be swapping my 91file for 104 next week. I also have APR's V-Tune which allows me to advance timing and such..

formulanerd · « **Reply #7 on:** July 31, 2009, 06:17:11 PM »

cool, if you notice a slight loss of power, like fuel that isnt completely being burned, you may be able to advance timing and get more power of it, just make sure you're logging for missfires and knock.

LOS · « **Reply #8 on:** July 31, 2009, 06:43:40 PM »

I thought the w/m will provide the smae net octane as race gas. I don't see a point in paying for race gas honestly. I'd say run it with and w/o the meth and see if anyhing changes. I bet it will keep your charge cool but probably won't net you more hp

formulanerd · « **Reply #9 on:** July 31, 2009, 11:21:06 PM »

i agree, and if he hadn't already bought the gas, i would have recommended not buying... but since he has it, he may as well test it out and do some comparisons.

mjohnson · « **Reply #10 on:** July 31, 2009, 11:29:53 PM »

funny you bring that up tonight.. I am actually heading to the dyno tomorrow. I've got about 1/8th tank of 93 in there now. I could prolly dump the 105 in and do my pulls. Then go back in a few days with just 93. Or is there a way to be able to test it both ways with 3 pulls?

I've noticed that my exhaust smells rich (has for quite some time). So from what you're saying I have unburned gas and I should be able to advance the timing and that will take car of it? Obviously I'm not going to mess with any settings until I get a good wideband A/F gauge in. What's a good method to monitor the missfires/knock?

scurvy_bandit · « **Reply #11 on:** August 01, 2009, 03:37:56 AM »

Id say advance your timing some, couldnt hurt. If it pulls like a one legged hooker then you are set.

mjohnson · « **Reply #12 on:** August 01, 2009, 10:25:33 AM »

haha. hookers are fun. well, going from stage 1 to k04 w/ matching 100oct file, it feels like it pulls like that anyway. Right now it spins all through 1st and most of second on relatively new nitto invo's, even after they've been warmed up. Now I know the invo isn't the stickiest of tires, but prior to the tune it would spin only a part of 1st...

formulanerd · « **Reply #13 on:** August 01, 2009, 02:57:35 PM »

the invo is a sick looking tire, but the performance is pretty horrible..... but with your setup traction will be non-existent in first either way

if i had 3 dyno pulls, i'd pull a 93, then a 93+w/m, then a 93+105.

mjohnson · « **Reply #14 on:** August 02, 2009, 12:43:18 AM »

Decided not to test between different fuels, but instead I checked between a cone filter, stock (modified) box, and open exhaust (w/ stock box). The winner was the stock box w/ closed exhaust at 199whp and 219 tq. Climate conditions are on the chart. I couldn't remember what gear is 1:1 and the dudes pretty much deal with muscle, so they just did 4th gear pulls from 2500-6000rpm.

Not to open up the can of worms again, but I kind of expected a little more. I took in to consideration that the previous numbers were likely skewed, but I still figured I'd break 200. I don't remember the climate conditions from before, but I know it was cooler and way less humid, but it was in colorado, no bama. Besides operator error, the only other thing I can think of is that the pulls in colorado were done in 3rd.

The only reason I have a slight doubt about the accuracy of these numbers today is that this Mach 1 mustang http://www.youtube.com/watch?v=MF-q3HhUKxo made 485whp just after a fresh tune, and then today (without any changes to the car) made 430whp. Hmm. Ok so the guy takes it to the track every week, but still. Losing 55whp over some use? Seems a little drastic, but maybe I'm naive.

and as you can see I'm running way rich until about 3500rpm..

punkrider99 · « **Reply #15 on:** August 02, 2009, 12:50:56 AM »

it's just a number mark. you should only use a dyno for comparative analysis. you don't race dynos do you? no, so the numbers don't mean anything. your operator used the right correction factor: zero (actually .01 so close enough). you don't correct power on a turbo car like you do on an n/a car.

btw any other car and you'd be considered super lean but 1.8t's and any other factory turbo smog car have to run lean to pass emissions. are you running a cat?

punkrider99 · « **Reply #16 on:** August 02, 2009, 12:52:50 AM »

btw you're obviously not running rich. race gas has a very different odor than regular pump gas.

mjohnson · « **Reply #17 on:** August 02, 2009, 01:00:26 AM »

Sorry Nate, didn't clarify. I wasn't running race gas. It was 93 w/ w/m.

I know it's just a number and that it could say I have 50hp, but the only thing that counts is what it does on the street/track. At the same time though, it'd be nice to get some accurate numbers just to get an idea.. I digress. Feeling the difference between what it was and is now, I'm in love again

Really? I've always heard that somewheres around 12 or 13 is what you want you're a/f to be at.

Right now I have a high flow cat. But I have been thinking about going 3" catless turbo-back with a magnaflow muffler

mjohnson · « **Reply #18 on:** August 02, 2009, 01:18:01 AM »

My buddy brought his Pontiac G8 with intake, full exhaust, and chip to the dyno as well. On the way we had a little fun on the highway and we were pretty much neck and neck. The only time one would pull away from the other is a bad reaction time, or something small like that. The little one-eight that could. (his is a 6.0 v8 mind you). That made me smile.

On the way home I passed a guy on a big ole harley. Well, I guess he wanted an excuse to play so he stayed right on me until the next light and then we took off. He started pulling on me until I hit 4th, then rolls reversed. That also made me smile...

mjohnson · « **Reply #19 on:** August 02, 2009, 01:22:07 AM »

Perhaps I set my goals too high. Now that I think about it, the dudes in the shop and even other dudes there w/ their american muscle said they were impressed compared to the numbers of the other cars tonight. Couple of em said they'd like to see the car on the track next friday.

scurvy_bandit · « **Reply #20 on:** August 02, 2009, 02:44:04 AM »

now its just time for a BT.

mjohnson · « **Reply #21 on:** August 02, 2009, 08:11:46 AM »

Yeah. Well, since this turbo seems to be running fine. I think I'll capitalize on that and go ahead and catch up on other smaller mods I would like to have done before going BT. (ie, fmic, redo the exhaust, couple more gauges, etc.)

punkrider99 · « **Reply #22 on:** August 02, 2009, 09:33:09 PM »

the generic rule of thumb is that a cat will make your afr look 1 point leaner than it really is. so an indicated afr of 14:1 is really more like 13:1 when you use a cat.

at what rpm is that k04 going to full boost at?

mjohnson · « **Reply #23 on:** August 02, 2009, 09:58:33 PM »

You know, I haven't really paid too close attention to that. The last dyno recorded boost.. It peaks at about 23 or 24psi at around 3300 I'd have to guess (without going for a drive right now).

scurvy_bandit · « **Reply #24 on:** August 03, 2009, 03:09:47 AM »

I hear ya man, makes sense to do the other things before jumping into the BT. Have you thought about a LSD yet? That could make a world of difference if you are spinning in 1 and 2 alot.

mjohnson · « **Reply #25 on:** August 03, 2009, 08:01:16 AM »

I actually have considered it. I've also considered picking up some super cheap wheels for the front and slapping on some drag radials..

In my quest for an LSD I've noticed regular LSD's and torque biasing LSD's. Is there a difference? or just a different name for the same thing?

Smokestack · « **Reply #26 on:** August 03, 2009, 08:24:03 AM »

Quote from: mjohnson on August 03, 2009, 08:01:16 AM

I actually have considered it. I've also considered picking up some super cheap wheels for the front and slapping on some drag radials..

In my quest for an LSD I've noticed regular LSD's and torque biasing LSD's. Is there a difference? or just a different name for the same thing?

There's two types of LSDs, but I think the VW scene uses primarily torsion diffs (torque biasing). You have ones that use clutch packs on the side gears to limit the amount of different wheel movement. Those are typically dirt cheap and found in a lot of RWD cars and 4x4s, but the clutches are a wear item that need to be replaced somewhat frequently to keep the diff from becoming an open diff. Torsion diffs use a whole bunch of gears to transfer the load across the side gears.

Clutch type diff on right with an arrow pointing to the clutches. Open diff on left:

Torsion diff:

mjohnson · « **Reply #27 on:** August 03, 2009, 09:04:09 AM »

Good to know.

The torsion diff pic didn't wouldn't load.

ianacole · « **Reply #28 on:** August 03, 2009, 11:35:22 AM »

The big thing to consider when looking at a TBD vs. and LSD is the expected use. A TBD is also a torque multiplier, multiplying the applied torque of the freer spinning wheel to the one with traction:

Quote from: http://auto.howstuffworks.com/differential6.htm

The Torsen (from Torque Sensing) works as an open differential when the amount of torque going to each wheel is equal. As soon as one wheel starts to lose traction, the difference in torque causes the gears in the Torsen differential to bind together. The design of the gears in the differential determines the torque bias ratio. For instance, if a particular Torsen differential is designed with a 5:1 bias ratio, it is capable of applying up to five times more torque to the wheel that has good traction.

The downside of this is that if one wheel has zero traction (ice, or in the air after bouncing off a curb on a race track, which is why I'm switching to an LSD), and your TBD is a 5:1 multiplier, 5x0 is 0, so it's back to being an open diff. In most cases, the wheel with less traction, still has some, generating torque. So if your inside wheel has 25% of the traction of the outside wheel, with the 5:1 TBD, 2.5 times the torque is applied to the outside wheel (very good at pulling you through a corner).

While an LSD does not have the benefits of multiplication, it will apply power to the wheel with traction regardless of the state of the wheel with less (or zero) traction. This is why the LSD is a popular choice for race cars and 4x4 vehicles, which will see a wheel in the air at some point in time. The downside of the LSD, as pointed out, is that it uses wear items to transfer power, requiring periodic maintenance.

For Volkswagen (especially the MKIV) most available differentials are TBD - Peloquin and Quaiff - with the WaveTrac being a "hybrid." Kaaz has recently released a true, clutch-based LSD for the MKIV, which I am in the process of installing in our 02J, switching from the Peloquin. While I won't have any direct reference for performance (back to back testing), I can relay some of my feelings on the performance and differences following this upcoming weekend's event at PPIR.

mjohnson · « **Reply #29 on:** August 03, 2009, 06:33:48 PM »

Good info.

punkrider99 · « **Reply #30 on:** August 03, 2009, 10:44:47 PM »

Quote from: mjohnson on August 02, 2009, 09:58:33 PM

It peaks at about 23 or 24psi at around 3300 I'd have to guess (without going for a drive right now).

now take that info and go look at your dyno plot and you'll understand why i said you're running lean.

MileHighAssassin · « **Reply #31 on:** August 08, 2009, 03:39:12 PM »

I kind of skimmed this but I wouldn't run meth injection over 40% meth.

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