Octane requirements for 23-25psi no alky

[Amelio]

Ok this is for the guys who run this boost level with no alky.....

I am prepping my car for the track and I would like to try and break into the 10's....my challenge is that every time I go to the track they open at 1pm and run until about 5-6...this is at Silver Dollar raceway.

So trying to tune...letting the car cool between runs usually nets me about 4-6 passes then I am out of time. This sucks because its a 2 hour drive from my house. I want to get my boost set and the car happy at that boost level before I even get to the track. Once I can get the car making 23-25 psi I will then go to the track and begin to dial in the tune from their.

I have never run the car at this psi before....I ran the car earlier this year at 17psi and was able to click off an 11.80 on a soft 5psi launch... this was on pump gas , I tried a 10psi launch but the tires would not hold. I believe the car will bust into the 10's at the 23-25psi range with a good solid launch.

With all this said I will have to make a trip to Atlanta dragway to buy some fuel......put that in the car and get the boost level to the 23-25 mark....this way it saves me a lot of tuning time that I don't have to eat up at the race track.

I kinda doubt 110 will be enough for this boost level but again I have never run this amount of boost so I don't know and as I said I don't have time to experiment.....

Should I go straight for C-16?

 

[TurboDave]

110 would do it if it were a strong mixture over 90%. 112 would be better. I used to run 112 at at least a 90% mix and ran 28psi easilly.

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[Amelio]

ok good to know I believe I can get 112 unleaded from the VP guy......I plan to run the car low on fuel and dump in 5-8 gallons should give me less dilution .

Thank you!

 

[buickGN3:16]

like turbodave said, 110 will do it if u run the tank as empty as u can & then dump 4 or 5 gallons in or 2 or 3 gallons, u dont want too much fuel cuz fuel is weight & weight slows u down. I have succefully run 25-26 psi on 110 w/ no alky & a tt race chip.



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[BIGPSI]

I did the same thing,but i used 116 and set car to boost level and had it tuned perfect before i went to the track. It saved a ton of time and the car went 11.01 on first pass then busted a 10.81@124. I was kindly asked to leave since i had no cage or fire jacket. I had my boost around 29#. Going thru the traps the O2 was about 730 with O knock. i never touched the tune at the track

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[Amelio]

I did the same thing,but i used 116 and set car to boost level and had it tuned perfect before i went to the track. It saved a ton of time and the car went 11.01 on first pass then busted a 10.81@124. I was kindly asked to leave since i had no cage or fire jacket. I had my boost around 29#. Going thru the traps the O2 was about 730 with O knock. i never touched the tune at the track

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This is what I am shooting for....I am pretty confident I have the power plant to click off a 10 sec pass ......it just burns up a lot of time inching up the boost utill the desired level is reached.

I plane on getting some fuel and making some 3rd gear pulls.......I got lots of empty country roads by me so I can get away with it

I just bought a PLX wideband and I am gonna pick up a new set of Mickey T DR's.....I plan to get to the track have the car set at 23-25 psi make some passes and play with the timing and launches hopefully everything works out and I can hit my goal.

 

[Red C5]

I always preferred using C16 and being on the safe side.

 

[87GN_70GS]

Is E85 available in your area?

 

[ijames]

What turbo, intercooler, heads, and compression ratio? How much timing do you want to run? That list will pretty much determine the octane requirement.

 

[Pronto]

I looked at the VP site and don't see 112 unleaded? I see Motorsport 109 ul which says good to 25lbs of boost.

 

[Amelio]

Is E85 available in your area?

Yes it is near me and I mix it with 93 which allows me to run 17psi which nets me a mid 11 sec pass....however it will in no way get me to my goal. I would have to run straight E-85 and I still dont know if that would cut it...plus I dont have enough injector to run straight E-85

 

[Amelio]

What turbo, intercooler, heads, and compression ratio? How much timing do you want to run? That list will pretty much determine the octane requirement.

TE-66, stock heads with bigger valves ported and polished by champion...same on the intake. Stock location 1 1/2 IC stock size pistons just forged aluminum TRW's

I dont know how much timing..... that is an unknown. .......

I wan a 10 sec pass and from what the car does at 17 psi I figure its gonna take 23-25 psi to achieve it. I plan to get the boost set just testing in 3rd gear on back roads then take it to the track for dialing in of launch psi and timing until I can click off a 10 sec pass.

When I was last at the track I ran 17psi and the timing was around 23 degrees in first/ second and I left 3rd gear to the stock setting on the TT chip. this was on 93oct with 4 gallons of E-85 which is what I run every day.

 

[Amelio]

I looked at the VP site and don't see 112 unleaded? I see Motorsport 109 ul which says good to 25lbs of boost.

yeah I saw that too....I could swear I was told by the VP guy at the track he had 112 unleaded....I must have heard wrong.

I saw the motorsport 109 it only has an MO rating of 101oct and an RO of 109....I dont know if thats enough if I need to go 25psi.

I think the C-16 is probably the safest since it has a MO rating of 117.

The big question I have always had is what kind of CR is the engine have when at 25psi?

the C-16 is good for turbo engines and 17:1 CR I doubt the CR in my engine is that high but I would think its got to be close to 14:1

 

[TurboTnZ06]

110 should get you there. Bring ice and a fan, don't worry about cooling the car off too much in a TnT. Me? I'd run a full tank of 116 when you get to the track and crank it up. I did that for 10 yrs, drive to track, fill up with race ga$, race, drain tank of race gas, drive home. Now I run alky and life is simple again, the same tune that can go 130+ in the 1/4 is what I use to go get drive thru lunch.

 

[Chuck Leeper]

Call Ed at Silver Dollar, and ask what he has there. They sell race gas, and may have the right stuff.
I don't think guessing at the % is a good idea.
drain the tank, add the race gas, and reverse that, when u R done. No point in beating up on your wide band sensor.

 

[Amelio]

yeah Chuck that was my concern with tuning near the house on fuel....how much abuse will the wideband take? I would not think that making pulls near the house in 3rd would wipe out my O2.....I will drain the tank throw in some fuel a fresh set of plugs and start inching up the boost until I hit 23-25 psi nice and clean. Then I plan to leave all my settings a lone and hopefully get to the track the week or two after that. Hopefully I can do this in the next month or so before the track closes.

I will most likely get some fuel from my buddies race shop near the house its 20 min away as apposed to silver dollar which is 2 hours

 

[ijames]

TE-66, stock heads with bigger valves ported and polished by champion...same on the intake. Stock location 1 1/2 IC stock size pistons just forged aluminum TRW's

I dont know how much timing..... that is an unknown. .......

I wan a 10 sec pass and from what the car does at 17 psi I figure its gonna take 23-25 psi to achieve it. I plan to get the boost set just testing in 3rd gear on back roads then take it to the track for dialing in of launch psi and timing until I can click off a 10 sec pass.

When I was last at the track I ran 17psi and the timing was around 23 degrees in first/ second and I left 3rd gear to the stock setting on the TT chip. this was on 93oct with 4 gallons of E-85 which is what I run every day.

This is all by feel based on tuning several cars over the years, but with that combo and a low 18-20 degree timing street chip I would expect you could run about 19-20 psi in 3rd gear on straight 93 octane. Keep the timing low and add boost up to about 25 psi and you will need in the ballpark of 100 octane, maybe a little more, maybe not so much, so since 100 and 104 unleaded is pretty common one of those would be a good place to start. If you go to 25 psi and add more timing like 23-24 degrees you might need all the way up to 110 octane and that's hard to do without lead. You will definitely pick up more hp from the boost than from the higher timing, and the lower the timing the easier and safer it is to tune becase the engine is less detonation prone if you get the fueling too far off. Good luck.

 

[BIGPSI]

This is all by feel based on tuning several cars over the years, but with that combo and a low 18-20 degree timing street chip I would expect you could run about 19-20 psi in 3rd gear on straight 93 octane. Keep the timing low and add boost up to about 25 psi and you will need in the ballpark of 100 octane, maybe a little more, maybe not so much, so since 100 and 104 unleaded is pretty common one of those would be a good place to start. If you go to 25 psi and add more timing like 23-24 degrees you might need all the way up to 110 octane and that's hard to do without lead. You will definitely pick up more hp from the boost than from the higher timing, and the lower the timing the easier and safer it is to tune becase the engine is less detonation prone if you get the fueling too far off. Good luck.

i can run 18-20# on straight 93 no problem. i have similar parts,te45a ported heads and intake with a front mount. i just wanted to be safe,so i used 116 ,new o2 and new plugs. bam 10.81@124. i went 11.80 on 93 and 18# all done on low timing

 

[we4Mateo]

yeah I saw that too....I could swear I was told by the VP guy at the track he had 112 unleaded....I must have heard wrong.

I saw the motorsport 109 it only has an MO rating of 101oct and an RO of 109....I dont know if thats enough if I need to go 25psi.

I think the C-16 is probably the safest since it has a MO rating of 117.

The big question I have always had is what kind of CR is the engine have when at 25psi?

the C-16 is good for turbo engines and 17:1 CR I doubt the CR in my engine is that high but I would think its got to be close to 14:1

Your compression ratio is static regardless of boost. Cylinder pressure will vary with boost and power but the compression ratio stays the same. You're builder will know but probably between 8:1 and 9:1.

 

[delcowizzid]

There is a calculator online to work out what dinamic comp ratio vs boost my 8:1 v6 at 14 psi worked out at around12:1 ill find the calc when im at my desktop

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