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I'm back!
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Racing last night against a Cobra on pump gas, I kept the boost right around 18.5psi, and the AFR was solid 11.2 through 5th and 6th gear. Anyone wanna chime in on how safe this is on 93 octane fuel? Just wondering what other people generally like to see on the same gas and boost.

Oh FYI I have a full fuel system with 850cc injectors and dual fuel pumps, and my electronics are VPC and SuperAFR.
 

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Edge On The GE-T Epidemic
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OT brad , but your vids are halarious , nice kills. I agree with Az man , for 93 Piss jucie 18.5psi is right on the line , i doubt its doing too much harm but it isnt exactly pampering the engine. Throw in some race gas and let it burn. Later
 

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You can't go by how much boost you are running. It all comes down to how much power you make on 18psi on pump gas. 11.2 is very safe but yea just to be safe I would run 100 octane or soo to run top gears. Car has a lod of load on top gears and the heat can cause detonation etc. I don't think I would really be worried on a 67mm turbo though.. Good luck..

Sherbaz
 

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Shawn Davis
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Sherbaz said:
You can't go by how much boost you are running. It all comes down to how much power you make on 18psi on pump gas. 11.2 is very safe but yea just to be safe I would run 100 octane or soo to run top gears. Car has a lod of load on top gears and the heat can cause detonation etc. I don't think I would really be worried on a 67mm turbo though.. Good luck..

Sherbaz
I'm surprised by this comment. Isn't the pressure you're running and the amount of load the primary factors in deciding octane? You're suggesting that the power level is more important. So if I have a cold charge at 18 psi and make more power than a hot charge at 18 psi, you're suggesting I need more octance for the cold charge?
 

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Have you ever noticed why people don't do highway pulls on Bpu cars at 18psi?? Like I mentioned in my comment earlier; the heat that is produced in tall gears can cause detonation and thus the 100octane remark. Yes, the hp also is a key factor. Let me give you another example. Check the v8 guys who run turbo's, why do u think they only run 5-6 psi of boost??? The reason they only run 5-6 psi of boost is b.c they have big motors and at that boost level , they can make the same amount of POWER to what we will make at lets say 18-20psi so you can't really go by pressure only. Good luck

Sherbaz
 

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95 Hardtopper X 2
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I have a 63mm turbo and stock fuel system, what I notice is that if I run pump gas and 17.5-18psi and a consistent AFR's of 10.5 (my car is running rich) the egt stays at 690C through 4th gear, but in 5th even with the same AFR egt's shoot to about 810-820C. So I have noticed the AFR gauge is not a good measure on how safe things are. BTW egt probe is in the 6th runner for comparison.
-Mani
 

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MANI009 said:
I have a 63mm turbo and stock fuel system, what I notice is that if I run pump gas and 17.5-18psi and a consistent AFR's of 10.5 (my car is running rich) the egt stays at 690C through 4th gear, but in 5th even with the same AFR egt's shoot to about 810-820C. So I have noticed the AFR gauge is not a good measure on how safe things are. BTW egt probe is in the 6th runner for comparison.
-Mani

EGT also measures engine load.
 

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Sooooooo JDM
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Sherbaz said:
Have you ever noticed why people don't do highway pulls on Bpu cars at 18psi?? Like I mentioned in my comment earlier; the heat that is produced in tall gears can cause detonation and thus the 100octane remark. Yes, the hp also is a key factor. Let me give you another example. Check the v8 guys who run turbo's, why do u think they only run 5-6 psi of boost??? The reason they only run 5-6 psi of boost is b.c they have big motors and at that boost level , they can make the same amount of POWER to what we will make at lets say 18-20psi so you can't really go by pressure only. Good luck

Sherbaz
Most of the V8 guys running low boost are running higher compression OEM pistons and advanced timing (optimized for N/A) . High Compression + Boost + too much timing = Detonation. A correctly setup FI V8 engine and proper tuning will allow 17-18 PSI on pump gas without detonation. Detonantion is what kills most boosted engines.

Ryan
 

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Ryan23 said:
Most of the V8 guys running low boost are running higher compression OEM pistons and advanced timing (optimized for N/A) . High Compression + Boost + too much timing = Detonation. A correctly setup FI V8 engine and proper tuning will allow 17-18 PSI on pump gas without detonation. Detonantion is what kills most boosted engines.

Ryan
:werd: :iwdumbass
 

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Shawn Davis
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Ryan23 said:
Most of the V8 guys running low boost are running higher compression OEM pistons and advanced timing (optimized for N/A) . High Compression + Boost + too much timing = Detonation. A correctly setup FI V8 engine and proper tuning will allow 17-18 PSI on pump gas without detonation. Detonantion is what kills most boosted engines.

Ryan

Thanks for saving me the explanation of compression ratio. Let's not forget that in most cases they have more displacement to produce that power as well, but as Ryan set the contributing factor in this conversation is the higher compression ratio.
 

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IMHO, the EGT reading is more important here. You know your AFR is fine but on a long highway pull you'll want to make sure your EGT doesn't exceed something safe. If you have a probe at the collector and you hit 900C, you probably want to let the car relax a bit.

AZMongoose said:
EGT also measures engine load.
 

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I wouldn't do a highway pull on pump gas - especially not 5th and 6th.
 

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I've done tons of highwaypulls on pump and my motor is in great condition still. Maybe my maps are conservative enough and I'm smart enough to keep an eye on the EGTs but I wouldn't go saying you can't do it on pump. It's just a matter of having things setup properly and keeping an eye out for trouble signs like AFR, EGT, Oil temps and such.
 

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The need for speed
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silvino said:
I've done tons of highwaypulls on pump and my motor is in great condition still. Maybe my maps are conservative enough and I'm smart enough to keep an eye on the EGTs but I wouldn't go saying you can't do it on pump. It's just a matter of having things setup properly and keeping an eye out for trouble signs like AFR, EGT, Oil temps and such.

Exactly... There is no magic number for boost you can run on pump gas - there's just so many variables. With piggyback stuff you don't really know for sure if you're knocking or not, so you rely on the stock ECU to pull timing. With enough timing being pulled, EGTs will get even hotter. People say EGT's aren't important (for tuning) but they are important for ensuring the health of the motor, as long as you have a baseline for what temps are good/bad based on the probe location.
 

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Sherbaz said:
You can't go by how much boost you are running. It all comes down to how much power you make on 18psi on pump gas. 11.2 is very safe but yea just to be safe I would run 100 octane or soo to run top gears. Car has a lod of load on top gears and the heat can cause detonation etc. I don't think I would really be worried on a 67mm turbo though.. Good luck..

Sherbaz
power has nothing to do w/ it.

very simply:
an engine runs on air & gas. too much air, too lean, it runs hotter, and a prolonged run @ a lean A/F could spell disaster.

adding another variable:
an engine running hot in the combustion chamber w/ advanced timing leads to detonation. the air molecules are closer together in the combustion chamber when the spark goes off. the spark ignites one molecule, and b/c of the (already present) heat & proximity (due to reduced combustion space), you get an uncontrolled reaction.

if you had kept the A/F richer, the gas acts as a coolant in the combustion chamber.

obviously, there are other variables like intake temp, is the turbo beyond its efficiency & heating the air, is the IC beyond its efficiency, etc.
 

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The need for speed
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silvino said:
Another issue might be the fact that the Supra has a really shitty engine bay for getting hot air out of it.
That's why you buy a TS hood or something along those lines to help air escape out :)
 

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Still not all that great even with those vents. Those hoods also become more dangerous the more open they are for street use.

mav7 said:
That's why you buy a TS hood or something along those lines to help air escape out :)
 
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