higher boost/lower timing - how far is too far?
Oct 28, 2008, 09:31 AM
#31
Richer AFR converts more CO (pressure) into mechanical energy. Leaner creates more heat. At some point (usually 12.5 - 13.0AFR depending on many things) the two assits each other to create the highest cyl psi while leaner or richer makes less power. Timing is just the means of leverage by getting the peak pressure on target (also dependant on many things). Boost just allows more fuel (potential energy) to be used and the goal is minimizing the amount that passes out the tailpipe unburned (WB wont tell you that either) getting to peak pressure.
Backpressure increases on turbine as more volume (rpm) goes through, esp stock turbo. This screws up the combustion and negates any boost achieved.
Backpressure increases on turbine as more volume (rpm) goes through, esp stock turbo. This screws up the combustion and negates any boost achieved.
Oct 28, 2008, 04:16 PM
#32
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Richer AFR converts more CO (pressure) into mechanical energy. Leaner creates more heat. At some point (usually 12.5 - 13.0AFR depending on many things) the two assits each other to create the highest cyl psi while leaner or richer makes less power. Timing is just the means of leverage by getting the peak pressure on target (also dependant on many things). Boost just allows more fuel (potential energy) to be used and the goal is minimizing the amount that passes out the tailpipe unburned (WB wont tell you that either) getting to peak pressure.
Backpressure increases on turbine as more volume (rpm) goes through, esp stock turbo. This screws up the combustion and negates any boost achieved.
Backpressure increases on turbine as more volume (rpm) goes through, esp stock turbo. This screws up the combustion and negates any boost achieved.
Oct 28, 2008, 08:56 PM
#34
"If one psi is worth 10hp and dropping 1* of timing is gonna lose 5hp, then its worthwhile until the EGTs exceed a safe level for what form of racing you are doing. If you drag race and are really using the car for only 10-11 seconds at the time EGTs are irrelevant. If you make highway pulls for 30-60 seconds then it becomes more pronounced on how long you can stay at low timing and high boost. If you are roadracing for 20min or 2hrs then its even more critical to keep the boost low and timing high to keep the EGTs down."
On E85 we are in a totally different level since between the octane and the evaporative effect of the fuel we can operate WAY outside the efficiency range of the turbo and still make great power.
Point is, its all dependent on how you use your car and what your desired time before rebuild is. I have 37,000 miles on my car and 25,000 of it was high boost/low timing on pumpgas. Only the last 4k or so has been on E85 and 30k of it has been with a Green at 25+psi and careful tuning. Not just anyone is gonna be able to go out and run 30psi though. It took weeks of 1psi at a time, changing all the driving conditions, logging, tweaking, logging, etc. before I upped the boost and then repeated the process.
Just so no one misunderstands I am not advocating tuning for MBT or tuning for excessively high EGTs. In either event when you find the threshhold you need to back up from where you are. In the case of MBT 4* is sufficient, and EGT drop boost and raise timing back in so the peak and average EGT are 100* less.
hope that was all in english
aaron
Last edited by JohnBradley; Oct 29, 2008 at 06:16 PM.
Oct 28, 2008, 10:42 PM
#36
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4* @ pk tq / 15* up top
28~29psi @ pk tq tapering to 21psi at redline, 3bar confirmed.
11.5 AFR from peak to redline
93 pumpgas
I dragrace and tune accordingly. With that in mind, I have found more boost and less timing is better. Timing blows **** up if you get crazy.
SQ
28~29psi @ pk tq tapering to 21psi at redline, 3bar confirmed.
11.5 AFR from peak to redline
93 pumpgas
I dragrace and tune accordingly. With that in mind, I have found more boost and less timing is better. Timing blows **** up if you get crazy.
SQ
Oct 29, 2008, 03:32 AM
#37
Its just like how much timing is enough? With timing its MBT, the point where adding timing doesnt add power or if it is its not leaps and bounds. With boost on any turbo, stock turbo especially, it can be summed up by something Mark Shead said on this forum awhile ago. Unfortunately most of the thread got deleted or moved because it had turned into a pissing match but the basic thought was something like this:
My personal experience and what Bryan (Razorlab) backed up on pumpgas (92 for me and 91 for him) is that on a Green 29-30psi was possible with 9-10* of timing at redline and only -1* to 0* at peak boost. For the record that was only about 4-5* less at peak boost than you would get with 22-23psi and a good intercooler. I didnt actually dyno but in my datalogs I showed acceleration increase with more boost/less timing, estimated horsepower (datalogging) increases, and seat of the pants. My car went from 385 to 415whp with 6psi more and 4* less timing. I believe Bryan saw similar percentage of increase gains when we were both on gasoline.
On E85 we are in a totally different level since between the octane and the evaporative effect of the fuel we can operate WAY outside the efficiency range of the turbo and still make great power.
Point is, its all dependent on how you use your car and what your desired time before rebuild is. I have 37,000 miles on my car and 25,000 of it was high boost/low timing on pumpgas. Only the last 4k or so has been on E85 and 30k of it has been with a Green at 25+psi and careful tuning. Not just anyone is gonna be able to go out and run 30psi though. It took weeks of 1psi at a time, changing all the driving conditions, logging, tweaking, logging, etc. before I upped the boost and then repeated the process.
hope that was all in english
aaron
My personal experience and what Bryan (Razorlab) backed up on pumpgas (92 for me and 91 for him) is that on a Green 29-30psi was possible with 9-10* of timing at redline and only -1* to 0* at peak boost. For the record that was only about 4-5* less at peak boost than you would get with 22-23psi and a good intercooler. I didnt actually dyno but in my datalogs I showed acceleration increase with more boost/less timing, estimated horsepower (datalogging) increases, and seat of the pants. My car went from 385 to 415whp with 6psi more and 4* less timing. I believe Bryan saw similar percentage of increase gains when we were both on gasoline.
On E85 we are in a totally different level since between the octane and the evaporative effect of the fuel we can operate WAY outside the efficiency range of the turbo and still make great power.
Point is, its all dependent on how you use your car and what your desired time before rebuild is. I have 37,000 miles on my car and 25,000 of it was high boost/low timing on pumpgas. Only the last 4k or so has been on E85 and 30k of it has been with a Green at 25+psi and careful tuning. Not just anyone is gonna be able to go out and run 30psi though. It took weeks of 1psi at a time, changing all the driving conditions, logging, tweaking, logging, etc. before I upped the boost and then repeated the process.
hope that was all in english
aaron
I blame my beat up stock FMIC lol.
Oct 29, 2008, 09:36 AM
#39
Make it simple, tune the fuel, turn up the boost with timing pulled back. If running small turbo dont go into high backpressure (too much WGA preload). Add timing until it stops producing while retuning afr and load each time.
Running too retarted with or without high boost just turns potential HP into EGT. Too advanced, will just lead to too retarded anyway with knock control or too rich with high cyl temps.
Translated to english
Running too retarted with or without high boost just turns potential HP into EGT. Too advanced, will just lead to too retarded anyway with knock control or too rich with high cyl temps.
Translated to english
Last edited by C6C6CH3vo; Oct 29, 2008 at 09:39 AM.
Oct 29, 2008, 10:51 AM
#41
Try adding some water to that meth and then retune. The water does a better job than meth suppressing knock and lowering EGTS, making it safer.
The last car I tuned with a 50/50 meth/h20 HFS-5 with 2x 1.0mm jets, I managed 6* peak, 14* redline, 12.4-12.5 AFRS, +28 PSI!!! all that with 0 knock.
The car was stupid fast, this is "street/drag car" NOT USED FOR ROAD RACING.
JB said it perfectly keep adding it till it you cant without knocking.
Evan Smith
Last edited by Vivid Racing; Oct 29, 2008 at 10:53 AM.
Oct 29, 2008, 12:24 PM
#43
Also the higher Ron resists predet not knock, two completely different things.
You have 2 burns in the engine. 1. Predet 2. Deflageration. Octane (Ron) controls the predet and prevents it. Predet somtimes appears as knock, as our knock sensors are not perfect. DET cans can help clearify.
Deflageration is the burn you want to inhance and build upon without the influance of predet. This is why no race gas company is the same. Anyone can produce good octane numbers. But which ones inhance the burn you actually want to inhance? knock occurs during this burn.
You know what predet is so I wont explain...
Knock is after TDC and after the ignition happens. You ignite the fuel, it starts in one place then spreads to the rest of the cylinder. Knock is when another flame starts on the other side of the cylinder and meets the intal flame head on creating a little boom aka knock.
Knock is produced by mainly (but not always) by hot air being compressed. knock is like predet so its easly confused its just after when the ignition has already happend. Meth helps cool that air therefore reducing knock. Water goes into the cylinder mixes then controls the burn and incylinder temps up to 60*! Water will easly remove more heat than meth in turn reducing knock. All this to Allow you to advance the timing, leaning it out and uping the boost = more power.
Good luck!
Evan Smith
Last edited by Vivid Racing; Oct 29, 2008 at 12:35 PM.
Oct 29, 2008, 01:35 PM
#45
Water will also make combustion happen later too so you automatically have to add 1-3 degrees too. There was a study done I read where they developed a method of determining angle of peak pressure just by spraying an unmetered amt of water into the charge on a steady load and rpm state.