Boost levels vs. octane rating
02-04-2011, 04:54 PM
#1
Racer
Thread Starter
Boost levels vs. octane rating
Just got my used Vitesse kit with all goodies included (PB, V-flex, MAP, boost control etc.).
The recommendation when running pump gas (US 93, EU 98) is to stay at 15psi boost.
I was hoping to run app. 17 psi and when doin some searches I find that a lot of Vitesse users are running higher boost levels.
What fuel octane rating is recommended at 17psi?
I use an octane booster claimed to increase the rating from 98RON to 98.4RON when added at a level of 30ml per 10litres of gas.
One alternative would be to add 10% E85 which should give 100-100.5 RON.
/Dea
The recommendation when running pump gas (US 93, EU 98) is to stay at 15psi boost.
I was hoping to run app. 17 psi and when doin some searches I find that a lot of Vitesse users are running higher boost levels.
What fuel octane rating is recommended at 17psi?
I use an octane booster claimed to increase the rating from 98RON to 98.4RON when added at a level of 30ml per 10litres of gas.
One alternative would be to add 10% E85 which should give 100-100.5 RON.
/Dea
02-05-2011, 03:54 PM
#4
Racer
Thread Starter
Should be no problem dialing in a new AFR curve with the Piggyback.
I was hoping not to have to use water injection, more stuff to install and some kind of warning system will be needed to detect low water levels so you don't run ot of water when on the track.
/Dea
/Dea
02-06-2011, 12:40 AM
#5
Drifting
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well for 17 psi i realy dont think you have to
the cheapest knock monitoring I've seen is this
http://www.powertune.com.au/turboxs-knocklight.html
or this
http://autospeed.com/cms/article.html?&A=0353
and i believe if you search you will find a thred on here to rig up an LED to so you the knock counts from the KLR
the cheapest knock monitoring I've seen is this
http://www.powertune.com.au/turboxs-knocklight.html
or this
http://autospeed.com/cms/article.html?&A=0353
and i believe if you search you will find a thred on here to rig up an LED to so you the knock counts from the KLR
02-06-2011, 08:22 AM
#6
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Many variables affect how much boost you can run on pump gas. You have outside temps, heat soak, quality of fuel (not all 93 or 98 octane are the same from all suppliers), how long are you on boost, how well your intercooler is functioning, do you have any oil in the intake (from blow-by..)...
We recommend 15psi on pump gas to leave you a safety margin. We know many of our customers run higher than 15psi on pump gas, we just don't recommend it. With the V-FLEX, ignition will get retarded under boost to keep knock away. However, you get to a point of diminishing returns...
Boost on the street for a short period is very different than boost on the track for a extended period.. You get away with plenty on the street, but not much on the track. Our products are designed to live on the track, customers are winning endurance races with these same products.
The higher the boost you run on pump gas the less of a safety margin you have. We can make a recommendation, but it's up to you to figure out what works best for your car. Our recommendations are based on years of experience. We know high boost gets people excited, but not much excitement when your engine fails just because you ran unreasonable amount of boost. A safety margin is not a bad thing.
We recommend 15psi on pump gas to leave you a safety margin. We know many of our customers run higher than 15psi on pump gas, we just don't recommend it. With the V-FLEX, ignition will get retarded under boost to keep knock away. However, you get to a point of diminishing returns...
Boost on the street for a short period is very different than boost on the track for a extended period.. You get away with plenty on the street, but not much on the track. Our products are designed to live on the track, customers are winning endurance races with these same products.
The higher the boost you run on pump gas the less of a safety margin you have. We can make a recommendation, but it's up to you to figure out what works best for your car. Our recommendations are based on years of experience. We know high boost gets people excited, but not much excitement when your engine fails just because you ran unreasonable amount of boost. A safety margin is not a bad thing.
02-09-2011, 06:42 AM
#7
Racer
Thread Starter
Thanks for the advice.
It's a track day car so some safety margin is of course good.
Seems like the smart thing is to run 15psi this season and log AFR, EGT and knock count at the track to get some real life data.
/Dea
It's a track day car so some safety margin is of course good.
Seems like the smart thing is to run 15psi this season and log AFR, EGT and knock count at the track to get some real life data.
/Dea
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02-09-2011, 10:13 AM
#9
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I am in the same boat as John on this one – many customers ask about ‘how much boost’ they can run.
Strangely enough I have the same answer as John – 15psi (its quite possible that John and I have done a little testing over the years and found some similar answers!)
What this means is that 15 psi is safe for 0 degrees, 100 degrees, 5 days at the track or being stuck in a traffic jam. At least on my set ups (and I think on John’s system as well) this means you can run 15psi in any situation safely.
On the engines/EMS stuff I do the typical set up will run the correct AFR/timing up to 25psi so its not a question of the engine running lean or bad timing. The problem is that we (the builders /tuners) cannot predict all the possible scenarios that the end user might encounter or create. I am quite confident that the engines/EMS that I build will run at 20+psi for street driving or dyno pulls. On the other hand I can also say that if you ran the engine at 20psi for an hour straight at the track when there is 100 degrees air temp you will heat soak the intercooler and the intake temps will start to rise until you eventually run into detonation. Based on that I cannot say that the end customer can run 20psi safely in any condition. 95% of the time it would be fine – but that last 5% in the hands of someone that is not being ‘prudent’ will cause a problem.
On my street car I run 15psi as a daily drive setting, 18psi for ‘fun’ and 20psi if somebody needs to be impressed. If I really needed it I could do 25psi….but in all reality all I would get was wheel spin!
Oh yeah – for the original poster – forget commercial ‘octane boosters’….they are just about useless. Search the list for toluene if you really feel the need to use additives.
Strangely enough I have the same answer as John – 15psi (its quite possible that John and I have done a little testing over the years and found some similar answers!)
What this means is that 15 psi is safe for 0 degrees, 100 degrees, 5 days at the track or being stuck in a traffic jam. At least on my set ups (and I think on John’s system as well) this means you can run 15psi in any situation safely.
On the engines/EMS stuff I do the typical set up will run the correct AFR/timing up to 25psi so its not a question of the engine running lean or bad timing. The problem is that we (the builders /tuners) cannot predict all the possible scenarios that the end user might encounter or create. I am quite confident that the engines/EMS that I build will run at 20+psi for street driving or dyno pulls. On the other hand I can also say that if you ran the engine at 20psi for an hour straight at the track when there is 100 degrees air temp you will heat soak the intercooler and the intake temps will start to rise until you eventually run into detonation. Based on that I cannot say that the end customer can run 20psi safely in any condition. 95% of the time it would be fine – but that last 5% in the hands of someone that is not being ‘prudent’ will cause a problem.
On my street car I run 15psi as a daily drive setting, 18psi for ‘fun’ and 20psi if somebody needs to be impressed. If I really needed it I could do 25psi….but in all reality all I would get was wheel spin!
Oh yeah – for the original poster – forget commercial ‘octane boosters’….they are just about useless. Search the list for toluene if you really feel the need to use additives.
02-11-2011, 02:29 PM
#10
Racer
Thread Starter
Good advice! I'll start at 15 and when everything is tuned and tested I'll increase it in 0.5psi increments and look closely at the knock counter.
The target was not really to have 17psi boost but to reach 320 whp.
I'll probably be somewhere around 290whp at 15psi (VR-kit as listed above, SFR stg 2 turbo, improved exhaust).
I'd prefer not to use race gas (btw what is the definition of race gas? >100 US octane? ) since it's hard to get hold of and you have to bring it with you to the track meetings.
Maybe a cam or headers to get increase VE is a better way then just turning up the boost.
/Dea
The target was not really to have 17psi boost but to reach 320 whp.
I'll probably be somewhere around 290whp at 15psi (VR-kit as listed above, SFR stg 2 turbo, improved exhaust).
I'd prefer not to use race gas (btw what is the definition of race gas? >100 US octane? ) since it's hard to get hold of and you have to bring it with you to the track meetings.
Maybe a cam or headers to get increase VE is a better way then just turning up the boost.
/Dea
02-12-2011, 09:55 PM
#11
Burning Brakes
another good alternative is sunoco 100 gt unleaded, it has a stoichiometry closest to pump gas , I belive the stoich on this 100 unleaded gt is 14.4 and on regular pump unleaded , the stoich is between 14.6-14.8.
@Chris White +1
-octane boosters are like non alchoholic beer, so don't buy them. toluene ( I pronounce as Tol-u-eene) is righteous. But I think you will have better luck with unleaded race gas with higher boost levels, you just need to dial in the correct mixture depending on the stoichiometry of the gas you are using. IIRC, in John's kit (vitesse), the instructions said something about , if using race gas, use fuel with closest stoichiometry to pump gas for easier tuning when swithing from pump to racing gas or something of that nature, or John himself told me that, now I don't remember....
@Chris White +1
-octane boosters are like non alchoholic beer, so don't buy them. toluene ( I pronounce as Tol-u-eene) is righteous. But I think you will have better luck with unleaded race gas with higher boost levels, you just need to dial in the correct mixture depending on the stoichiometry of the gas you are using. IIRC, in John's kit (vitesse), the instructions said something about , if using race gas, use fuel with closest stoichiometry to pump gas for easier tuning when swithing from pump to racing gas or something of that nature, or John himself told me that, now I don't remember....
Last edited by kev951; 02-13-2011 at 02:35 PM.
02-17-2011, 03:42 PM
#13
Three Wheelin'
E10 is basically what gas is over in the states now I think. I can't find a single station in Orlando that doesn't have a sign saying "Contains at least 10% Ethanol"
