Boost question.
Boost question.
So I recently got my car tune for e85 and is making 365hp. So far she runs great. My question is when when I'm going thru the gears I'm boosting fine. First gear tops off at 10psi, 2-5 gear it's hitting 25psi which seems normal. Now when when I'm accelerating onto the freeway I can see my boosting gauge hitting 27-28 psi! Is that normal? Or it's just my driving? I usually like to gun it on 5th and hardly downshift to accelerate.
Evolved Member
Joined: Oct 2013
Posts: 1,334
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From: United States
There are a few aspects that make doing this "bad" for your engine:
1. Unpredictable boost spikes - as you are loading the car in a higher gear and generally with a decent amount of wind resistance, the onset of full boost is going to come sooner. The amount of peak boost (and subsequently torque) will thus be higher in the case of a careless wategate/boost mapping in your ECU.
2. MIVEC - the fact that we don't have a stock crossover point for MIVEC mapping, this means the aggressive overlap dialed in for fast spool in 2nd and 3rd, is also applied to 4th and 5th gears. This exacerbates the problem stated in #1
3. Surge - since your turbo will be building that much more boost at lower RPM, it will cause surge as it is pumping more air than the engine can flow in that range. This is bad for the turbo itself and also causes spikes in MAF metering which leads to jagged timing and fuel delivery.
4. Uncharted territory - as your turbo will be spooling that much faster and calculated load will be spiking due to surge, your car will pass through breakpoints in your timing and fuel maps that your tuner probably has not accounted for. This could lead to overly rich or lean conditions, as well as overly-advanced timing.
So, say you were tuned for a nice conservative 350 lb-ft (Dynojet) in 3rd gear. With all of what results from 1-4, you may *easily* spike over 400 lb-ft on a 4th or 5th gear pull. Momentarily, you could even hit over 450 lb-ft before our reactive boost system kicks in.
The worst thing that can happen in combination with 1-4 is detonation. Given that you could be running unpredictably lean, along with more boost and potentially more timing advance than desired all make for perfect conditions for detonation. These factors combined lead to a faster burn as well as a more volatile air/fuel mixture that is easier to sporadically light off. One or more severe detonation events can lead to significant hammering on a connecting rod that subjects it to way more force that it is designed to handle. Thus, rod through side of block.
1-4 alone can lead to failed connecting rods and similar failures. 1-4 plus detonation is almost guaranteed to result in a windowed block. This is why it's safer to tune for more torque on ethanol blends such as E85. Being that you're relatively assured detonation will never be experienced (not on stock turbo output, at least) on 70+ percent ethanol, you don't have to worry about that added danger factor.
from: http://www.evoxforums.com/forums/sho...d.php?t=247458
post#5- hope this helps.
1. Unpredictable boost spikes - as you are loading the car in a higher gear and generally with a decent amount of wind resistance, the onset of full boost is going to come sooner. The amount of peak boost (and subsequently torque) will thus be higher in the case of a careless wategate/boost mapping in your ECU.
2. MIVEC - the fact that we don't have a stock crossover point for MIVEC mapping, this means the aggressive overlap dialed in for fast spool in 2nd and 3rd, is also applied to 4th and 5th gears. This exacerbates the problem stated in #1
3. Surge - since your turbo will be building that much more boost at lower RPM, it will cause surge as it is pumping more air than the engine can flow in that range. This is bad for the turbo itself and also causes spikes in MAF metering which leads to jagged timing and fuel delivery.
4. Uncharted territory - as your turbo will be spooling that much faster and calculated load will be spiking due to surge, your car will pass through breakpoints in your timing and fuel maps that your tuner probably has not accounted for. This could lead to overly rich or lean conditions, as well as overly-advanced timing.
So, say you were tuned for a nice conservative 350 lb-ft (Dynojet) in 3rd gear. With all of what results from 1-4, you may *easily* spike over 400 lb-ft on a 4th or 5th gear pull. Momentarily, you could even hit over 450 lb-ft before our reactive boost system kicks in.
The worst thing that can happen in combination with 1-4 is detonation. Given that you could be running unpredictably lean, along with more boost and potentially more timing advance than desired all make for perfect conditions for detonation. These factors combined lead to a faster burn as well as a more volatile air/fuel mixture that is easier to sporadically light off. One or more severe detonation events can lead to significant hammering on a connecting rod that subjects it to way more force that it is designed to handle. Thus, rod through side of block.
1-4 alone can lead to failed connecting rods and similar failures. 1-4 plus detonation is almost guaranteed to result in a windowed block. This is why it's safer to tune for more torque on ethanol blends such as E85. Being that you're relatively assured detonation will never be experienced (not on stock turbo output, at least) on 70+ percent ethanol, you don't have to worry about that added danger factor.
from: http://www.evoxforums.com/forums/sho...d.php?t=247458
post#5- hope this helps.
There are a few aspects that make doing this "bad" for your engine:
1. Unpredictable boost spikes - as you are loading the car in a higher gear and generally with a decent amount of wind resistance, the onset of full boost is going to come sooner. The amount of peak boost (and subsequently torque) will thus be higher in the case of a careless wategate/boost mapping in your ECU.
2. MIVEC - the fact that we don't have a stock crossover point for MIVEC mapping, this means the aggressive overlap dialed in for fast spool in 2nd and 3rd, is also applied to 4th and 5th gears. This exacerbates the problem stated in #1
3. Surge - since your turbo will be building that much more boost at lower RPM, it will cause surge as it is pumping more air than the engine can flow in that range. This is bad for the turbo itself and also causes spikes in MAF metering which leads to jagged timing and fuel delivery.
4. Uncharted territory - as your turbo will be spooling that much faster and calculated load will be spiking due to surge, your car will pass through breakpoints in your timing and fuel maps that your tuner probably has not accounted for. This could lead to overly rich or lean conditions, as well as overly-advanced timing.
So, say you were tuned for a nice conservative 350 lb-ft (Dynojet) in 3rd gear. With all of what results from 1-4, you may *easily* spike over 400 lb-ft on a 4th or 5th gear pull. Momentarily, you could even hit over 450 lb-ft before our reactive boost system kicks in.
The worst thing that can happen in combination with 1-4 is detonation. Given that you could be running unpredictably lean, along with more boost and potentially more timing advance than desired all make for perfect conditions for detonation. These factors combined lead to a faster burn as well as a more volatile air/fuel mixture that is easier to sporadically light off. One or more severe detonation events can lead to significant hammering on a connecting rod that subjects it to way more force that it is designed to handle. Thus, rod through side of block.
1-4 alone can lead to failed connecting rods and similar failures. 1-4 plus detonation is almost guaranteed to result in a windowed block. This is why it's safer to tune for more torque on ethanol blends such as E85. Being that you're relatively assured detonation will never be experienced (not on stock turbo output, at least) on 70+ percent ethanol, you don't have to worry about that added danger factor.
from: http://www.evoxforums.com/forums/sho...d.php?t=247458
post#5- hope this helps.
1. Unpredictable boost spikes - as you are loading the car in a higher gear and generally with a decent amount of wind resistance, the onset of full boost is going to come sooner. The amount of peak boost (and subsequently torque) will thus be higher in the case of a careless wategate/boost mapping in your ECU.
2. MIVEC - the fact that we don't have a stock crossover point for MIVEC mapping, this means the aggressive overlap dialed in for fast spool in 2nd and 3rd, is also applied to 4th and 5th gears. This exacerbates the problem stated in #1
3. Surge - since your turbo will be building that much more boost at lower RPM, it will cause surge as it is pumping more air than the engine can flow in that range. This is bad for the turbo itself and also causes spikes in MAF metering which leads to jagged timing and fuel delivery.
4. Uncharted territory - as your turbo will be spooling that much faster and calculated load will be spiking due to surge, your car will pass through breakpoints in your timing and fuel maps that your tuner probably has not accounted for. This could lead to overly rich or lean conditions, as well as overly-advanced timing.
So, say you were tuned for a nice conservative 350 lb-ft (Dynojet) in 3rd gear. With all of what results from 1-4, you may *easily* spike over 400 lb-ft on a 4th or 5th gear pull. Momentarily, you could even hit over 450 lb-ft before our reactive boost system kicks in.
The worst thing that can happen in combination with 1-4 is detonation. Given that you could be running unpredictably lean, along with more boost and potentially more timing advance than desired all make for perfect conditions for detonation. These factors combined lead to a faster burn as well as a more volatile air/fuel mixture that is easier to sporadically light off. One or more severe detonation events can lead to significant hammering on a connecting rod that subjects it to way more force that it is designed to handle. Thus, rod through side of block.
1-4 alone can lead to failed connecting rods and similar failures. 1-4 plus detonation is almost guaranteed to result in a windowed block. This is why it's safer to tune for more torque on ethanol blends such as E85. Being that you're relatively assured detonation will never be experienced (not on stock turbo output, at least) on 70+ percent ethanol, you don't have to worry about that added danger factor.
from: http://www.evoxforums.com/forums/sho...d.php?t=247458
post#5- hope this helps.
i never experienced any 5th gear problem(any in gear problem) . i can floor it as long as the car doesnt chocking in 5th gear below 2k easy, and just keep my feet on the floor all the way untill it gets out of the hole i made for her
Never had any glitch and you dont suppose to only just a chocking car. Which wont accelerate perhaps. So i wouldnt call it an Evo problem.
imho if that matters.
for the other guy, you migjt want to recheck. your car witha tuner and let him solve the problem. if he cant then you need a new tuner.
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