Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[TTC]

Like i said in my other thread, im going to tune my car some on saturday and im going to use some race gas incase I make a mistake or advance my timing to much on my higher boost map. My current maps timing is bang on fine, but im adding about 4-6psi at red-line to it so im going to knock off some timing and tune it.

My question is: If i use racegas as abuffer for user error and tune on it, will my AFRS change when i switch back to regular gas?  Also, since racegars burns different, if i dont advance my timing enough will the racegas actually be detrimental to my day? Ex: Run hotter?

[jarebear667]

higer octane runs cooler,helps stay away from detonation,
ras gas burns slower than pump gas, so it should change your air fuels.

[Joseph Davis]

Race gas does not burn slower than pump gas, it will not change your AFRs.

Race gas timing is pump gas timing right up until you exceed the octane (read: cooling) of the pump gas which causes it's timing requirement to fall off.  Some V8's which are biased for low and midrange power, as well as oddball setups with too much CR and not enough cam like my D16Y5 Type-R, will have a 1-3 degree difference in pump gas and race gas timing on a NA engine, and this includes stock engines.  These engines reach detonation before they make best power.

That said, for your typical inline four cyl you make best power with a 3-5 degree buffer before you detonate - very easy engines to tune.

[TTC]

Thx alot JD.

[kgx]

higer octane runs cooler,helps stay away from detonation,
ras gas burns slower than pump gas, so it should change your air fuels.

i'd be more worried that most pump gas is blended with 10+% ethanol which changes the equivalence ratio. it's not much, but if you're tuned on the ragged edge on race gas you'll be too lean on normal pump- unless you can find non-oxy gas. some mom and pop stores still sell it.

[bigdaddyvtec]

Q16 WILL change your AFRs...(not alot but will) as will any oxygenated fuel.


a mix like youre talking??? It would be so minute that its not worrysome

FUCK YOU

[narfdanarf]

my car idles at 15:1 on c16 and when I put pump in it without changing the map it went to 18:1

[Joseph Davis]

Never seen that happen, narfy.

[jarebear667]

i wish i wasnt such a hillbilly sorry for the bad advise

[TTC]

Im not tuning so much for race gas as hoping for a window of safety incase i add to much timing. When im done tuning that day im going to go to a dyno and do it propah

for instance timing map currently on pump timing was at rouhgly 14psi at redline with a peak at bout 18. Was safe there

Going to tune for 18psi at redline now that i have an ext gate. So im going to knock off 3degrees to begin with and see if it detonates.
My concern is that when i tweak it with Race gas mix, probably 5050 that the a/f tweaks will be way off when i go back to 100% pump and run 14lbs again.

[lilpooh21186]

Your mbt will occur later with blended fuel than that with strait pump so there for when you reach mbt on blended fuel your probly going to slightly detonate on pump depending the blend. If your tuning on the dyno use a low timing value increase by 1deg untill your tq stops climbing or falls off then back up one degree and go from there

[Joseph Davis]

Your mbt will occur later with blended fuel than that with strait pump

How does fuel type affect where the engine naturally ingests the most air?  Really?

so there for when you reach mbt on blended fuel your probly going to slightly detonate on pump depending the blend.

That's ASSuming he's approaching knock limit for pump.  You're completely unfamiliar with the engine he's tuning, I'm pretty sure you've never tuned one. 

[92CXyD]

I'm finding this discussion interesting and entertaining. Are there going to be articles, graphs, or any other tech. to explain this posted.

I like tech info. it is crack for this nerd. ;D :yes:

[d112crzy]

I've gone from 92 to Trick 101 and noticed almost a full point richer at idle. This was on a 12:1, mild cam f22. Part throttle was slightly richer, but as it got closer to 0 vac, the change in afr was less. Weird.

[Joseph Davis]

That makes me wonder if there's some wierdness with viscosity between fuels.  Also, the ethanol laden fuels can go into solution with a certain amount of water which obviously displaces a small portion of fuel, on top of the lower energy by volume ethanol.

I've dealt with Shell and Exxon 93 going to Torco 110, unknown brand 114 (what they have at Shadyside, I'll have to ask), and C16.  To the best of my knowledge none have ethanol, and none are oxygenated.

[bigdaddyvtec]

I could see how from mfg to mfg there may be a BIT of a diff in AFs due to vsarious additives in the fuel, but 15 - 18??? WOW, even on Q that seems like ALOT

I agree with JD that the avg "pump" fuel with the uncertainty of the ethanol content DEFINATELY contributes.

[TTC]

Quite often here we use Sunoco 94 which is heavily laden with ethanol ... What about using toulene?

[bigdaddyvtec]

Toulene heptane and a splash of tranny fluid... LOL.


BLAMO

[narfdanarf]

I could see how from mfg to mfg there may be a BIT of a diff in AFs due to vsarious additives in the fuel, but 15 - 18??? WOW, even on Q that seems like ALOT

I agree with JD that the avg "pump" fuel with the uncertainty of the ethanol content DEFINATELY contributes.

Everyone I have talked to agrees that it is very weird.  It's almost like I accidently put e85 in the car or something. 

[Joseph Davis]

Shadyside uses Sunoco 114

[lilpooh21186]

Your mbt will occur later with blended fuel than that with strait pump

How does fuel type affect where the engine naturally ingests the most air?  Really?

i Never said anything about volumetric eff changing with fuel jd I was talking Min best timing which should change with higher octane fuel.  ;D

so there for when you reach mbt on blended fuel your probly going to slightly detonate on pump depending the blend.

i am unfamilier with his build probly never tuned one.
That's ASSuming he's approaching knock limit for pump.  You're completely unfamiliar with the engine he's tuning, I'm pretty sure you've never tuned one.