Advantages of running high octane

[daniel240]

i can get 100 octane for pretty cheap and i was wondering if it would be worth it to run it. i know it helps prevent knock and ping so can i advance my timing by using it and by how much? im running 8psi and currently retarding timing using the msd btm at .5deg/psi. could i possibly run at stock timing?

[574-240sx]

It helps with detonation. I run it at the track, autoX, and drift practices. I run it just in case. I guess its better to be on the safe side. Also it tends to run a little cooler. Nick

[240SicknessX]

leaded fuels tend to throw off o2 sensors, run about 2 more tanks of gas though the car and it should be fine, it will make the car run rich and guzzle gas, at lease this is what happenes when my uncle runs 116 in his GN at the track. Also i would imagine you would get more power from adding boost rather timing, if your adding 100 for tuning purposes.

[WDRacing]

Running 100 octane you can probably run 12-14psi of boost with the timing set to retard the way you have it right now. You don't want to depend on timing for more power. Unless you can remap the timing curve based on your new boost and octane level.

[daniel240]

hmm so i guess theres really no point in me running it right now since my injectors max out at around 8-9psi anyway, correct? or can i still turn up the boost higher than 8psi w/ the 370cc injectors if i run 100octane? if not, will i gain anything from running 100octane and leaving everything how i have it now at 8psi?

[WDRacing]

Increasing your octane without changing anything won't yeild any noticeable improvement. You can run the 100 octane and not retard your timing at all as long as you keep boost where it is now. Or you can add boost and keep the timing retarded with the current injectors.

Higher octane fuel allows you to run alot leaner mixture without detonation. Which is why cars run on straight alcohol or nitromethane. Methonal for some reason when used as the only fuel requires over double the amount of pump gas you would normally use.

In short, yes you can raise the boost with higher octane.

[daniel240]

you say it tends to run rich. so if i kept my setup the same and turned up the boost to say 12psi, with 100 octane, wouldnt it run rich untill i got past 8-9psi and my injectors max out? wouldnt i need to tune my car to run on 100 octane or could i leave it tuned how it is for 93 and just turn up the boost when i run 100? btw im just using a hacked mafs right now. another thing, wouldnt my mafs max out also if i run that high of boost?

[klattr1]

running race gas wont change your air fuel ratios (timing doesnt either).with the race gas, your just less likely to detonate (its like wearing a helmet in battle).if you have a stock mafs, yes it will max out prolly past 10 psi.

[WDRacing]

Here's the deal, your car is running right now on 93 octane at 8psi on a fixed amount of base timing with .5* of timing being taken out per lb of boost.

Using 100 octane will allow the same setup to run more boost without detonation. Not only will you gain power from additional boost, but you'll gain more power do to the leaner mixture you able to run with the higher octane.

Your MAF will be at max noise by 8 psi. This means your ecu won't increase the duty cyle for incoming air anymore then its at at this moment. However, if your not detonating, then you can still add boost.

The best way to do this is with a wide band and a knock meter. When I was running Alcohol injection and 100 octane I was hitting AF ratio's in the high 13's under 28 psi of boost. Once you crest 12.5/1 AF you start to make a ton more power.

As far as timing goes, you don't want to have to remove more then 1 degree of timing per lb of boost to keep from detonating. Retarding timing also yeilds higher EGT's which will eventually lead to knock.

What are you using for an O2 Meter?

[daniel240]

i dont have a wideband or knock meter, but i do have access to a wideband. what im thinking i might do is mix 100 octane w/ 93 about 1:1 and try increasing my boost 2psi up to 10 and see how that works. does this sound ok with my setup?

[WDRacing]

Yep, that sounds like how I started tuning with alky back in the day. Add alky, add boost...repeat.

[daniel240]

thanks, i will try it out and see how it goes.

[240SicknessX]

you say it tends to run rich.

when i said it would run rich i didnt mean by adding the 100 it would change the afr, but exhaust from the 100 octane would contaminate the 02 sensor, then the 02 wont be able to read the correct afr resulting in a rich conditionsry for any confusion

[Tx-Sx-FS]

hey WD...i have questions for ya...(1) u said that for every lb of boost to retard timing a .5* degree...is that true with every car?? (3) why is that? and how hard? **i will be running a SAFC and 370cc injectors**(2) but will i still max out my MAF at 9-10psi?? I will look to you or someone that u can send me to for information on settings when tuning rpm ranges on SAFC...(3) can u help me there??

[WDRacing]

I ran out of shielding gas on my welder today or I'd be done with the damn car already, I'm using a 8?1 FMU just to get the car out of the damn garage. I have a new fuel rail and a set of 42lb injectors going in as soon as I order my 300zx MAF. I'm also using the SAFCII to tune it with. So I can probably help you out when you need it. My suggestion is to get the 300ZX MAF off of ebay. Its WAY worth it.

To retard timing you'll need the MSD BTM, or MSD6 BTM, they are basically the same except the MSD6 is a spark amplifier and its alot more expensive. I'm using the MSD BTM. Once you install it, you can set how many degree's you want it to retard timing per lb of boost. Its real simple.

Your stock MAF will probably max out by 8psi.

I'm gonna run some alky to, so I'll be able to boost about 12 psi with the stock injectors, ot atleast till my injectors lock open or fuel lines burst...lol.

[daniel240]

hey WD, did you say you are using a knock meter? where can you get those at? i searched everywhere but couldnt find one for the 240.

[WDRacing]

http://www.jscspeed.com/univer...t.htm

Thats the same one I'm using...