How much boost on 450's

[patsdsm]

Just wondering i have a 99 GST with the EVO 3 16G, FMIC, intercooler piping, exhaust, and walboro 255lph fuel pump.. just wondering how much boost those 450's can handle somewhat safely??? also i have the S-AFC 2, get back to me! thanks

 

[diablos991]

Get a logger, start at 12psi, monitor your timing advance and increase boost accordingly.
All cars are different, so it is hard to give a standard number.

 

[patsdsm]

roughly... i dont' care about this motor.. i have a 6 bolt that is being rebuilt as we speak...so just so i can have some fun with the car and not have it blow right now... think it'll do fine around 14-15psi roughly?

 

[hottboost]

Without a logger there is no way to tell! One car can run great at 15PSI and another with the exact same mods could be running lean and knocking like crazy. A logger is a cheap tool that you will always be able to use and need with your new motor. Just a thought and good luck!

 

[diablos991]

If you turn up your boost too high, your car will pull so much timing that it will hurt performance and really hurt your engine. I have heard people say that their car was faster at X-2psi than Xpsi.
Well if you don't care about your motor you might as well do 45psi.

 

[donmagicjuan]

Before you make any attempt at tuning your car, you need an aftermarket AFPR to handle the flow of your fuel pump. As for how much boost you can run, the only way you'll know without a logger is by hitting fuel cut.

 

[GVR4592]

http://dsmtuners.com/forums/showthread.php?s=&postid=162072

 

[scottsee]

First off Boost=heat & Airflow=power. 25psi on a T-25 is not the same thing as 25psi on a Gt35r..

450'cc are good for 28.5 GPH. Assuming 1g's 37.5psi base fuel pressure, pump gas and a realistic 10.8:1 AFR you should hit 30lb/min airflow at 99.7% IDC to max out your Injectors. I'm not sure exactly what boost a evo316g requires to hit 30lb airflow. I'm sure somone will chime in..

 

[donmagicjuan]

First off Boost=heat & Airflow=power. 25psi on a T-25 is not the same thing as 25psi on a Gt35r..

450'cc are good for 28.5 GPH. Assuming 1g's 37.5psi base fuel pressure, pump gas and a realistic 10.8:1 AFR you should hit 30lb/min airflow at 99.7% IDC to max out your Injectors. I'm not sure exactly what boost a evo316g requires to hit 30lb airflow. I'm sure somone will chime in..

I have a couple problems with your post. First, the level of boost you're running doesn't exactly correlate to the temperature of your intake charge. It is true that beyond a certain point, turning up the boost will dramatically increase the amount of heat the turbo adds to the air charge, but this point is highly dependent upon the turbo. I think you alluded to this in your second statement, so if I'm misinterpreting you, I apologize. Secondly, I'm confused about your calculation for IDC. For conditions under boost, the fuel pressure is determined by the base pressure + the intake manifold pressure, and you would not be very wise to run your injectors up to over 99% before considering an upgrade. Lastly, 10.8:1 is not a very good approximation of the AFR for the stock fuel maps. A more realistic one would be between 9.5 and 10 to 1. The fact remains that you should never make attempts to "max out" your injectors without the means to safely monitor the appropriate parameters.

 

[GVR4592]

First, the level of boost you're running doesn't exactly correlate to the temperature of your intake charge. It is true that beyond a certain point, turning up the boost will dramatically increase the amount of heat the turbo adds to the air charge, but this point is highly dependent upon the turbo.

I'm a little confused by this. Are you saying that intake temps may not go up when boost pressure is increased?

 

[donmagicjuan]

I'm a little confused by this. Are you saying that intake temps may not go up when boost pressure is increased?

Not exactly. I was more distinguishing the relationship as a markedly nonlinear one.

 

[scottsee]

I have a couple problems with your post. First, the level of boost you're running doesn't exactly correlate to the temperature of your intake charge. It is true that beyond a certain point, turning up the boost will dramatically increase the amount of heat the turbo adds to the air charge, but this point is highly dependent upon the turbo. I think you alluded to this in your second statement, so if I'm misinterpreting you, I apologize. Secondly, I'm confused about your calculation for IDC. For conditions under boost, the fuel pressure is determined by the base pressure + the intake manifold pressure, and you would not be very wise to run your injectors up to over 99% before considering an upgrade. Lastly, 10.8:1 is not a very good approximation of the AFR for the stock fuel maps. A more realistic one would be between 9.5 and 10 to 1. The fact remains that you should never make attempts to "max out" your injectors without the means to safely monitor the appropriate parameters.

I'm sure you're aware with any known compressor efficiency anyone can calculate the heat of a turbo at any specif boost reference. I was just clarifying all turbos are different, and using boost as the subject of his question is less important then the level of airflow when calculating IDC for his injectors. At some point over boosting the turbo will over heat the charged air causing airflow to drop as boost increases making the IDC go down..

FP is in fact determined by BFP + vac/pressure. We have a 1:1 boost FPR thats accurate to around 68psi. I was saying that on his 1g with "correctly" adjusted base fuel pressure of 37.5psi he would be flowing a max of 28.5 GPH of fuel. Any other FP would calculate differently. like upping BFP to 46 would result in injectors flowing like 500cc's. That was simply for Math purp's only.. Same thing with 99% IDC. I was only stating the limits of his airflow to 100% IDC (all tuning aside). I was using 10.8:1 because its an pretty common rich AF to tune for with pump gas. 9.5:1 is the stock fuel enrichment when airflow reaches over 2.1g/rev, and thats no fun now is it?

I was trying to make a long post short. I didn't mean for anyone to take it out of context. sorry about that..
Edit: I just noticed you're in Wa too...

 

[donmagicjuan]

I'm sure you're aware with any known compressor efficiency anyone can calculate the heat of a turbo at any specif boost reference. I was just clarifying all turbos are different, and using boost as the subject of his question is less important then the level of airflow when calculating IDC for his injectors. At some point over boosting the turbo will over heat the charged air causing airflow to drop as boost increases making the IDC go down..

FP is in fact determined by BFP + vac/pressure. We have a 1:1 boost FPR thats accurate to around 68psi. I was saying that on his 1g with "correctly" adjusted base fuel pressure of 37.5psi he would be flowing a max of 28.5 GPH of fuel. Any other FP would calculate differently. like upping BFP to 46 would result in injectors flowing like 500cc's. That was simply for Math purp's only.. Same thing with 99% IDC. I was only stating the limits of his airflow to 100% IDC (all tuning aside). I was using 10.8:1 because its an pretty common rich AF to tune for with pump gas. 9.5:1 is the stock fuel enrichment when airflow reaches over 2.1g/rev, and thats no fun now is it?

Agreed. I understand the quest for brevity on these forums. I find myself getting quite longwinded at times.

Spokane's not terribly far. I've made it out there on a few occasions. Must be nice not having rain all the time.

 

[GVR4592]

Damn you're both in Washington, small world.

 

[scottsee]

Must be nice not having rain all the time.

It's nice makeing plans 3 weeks ahead of time and not having to worry about if it's going to of not.

 

[biglady112]

I am not going to tell you our boost level as we are at 6000ft above sea level. But the car was flowing 37lb/min at 55psi base fuel pressure. This was a stock motor 96 gsx with dsmlink and all other supporting mods. Just thought we would see how far they would go.

Steven

 

[GVR4592]

I am not going to tell you our boost level as we are at 6000ft above sea level. But the car was flowing 37lb/min at 55psi base fuel pressure. This was a stock motor 96 gsx with dsmlink and all other supporting mods. Just thought we would see how far they would go.

Steven

Altitude doesn't affect the amount of pressure inside of the intake manifold. Boost is the turbo's job, regardless of altitude, boost is boost. The only difference is the turbo has to work harder to achieve that boost level.

 

[biglady112]

18psi on the 450's. This was with a stock exhuast though. Say 4 more psi and 4lb/min by simply bolting on a 3" exhuast and test pipe. This was also with 950's here. The injectors were pushed very far though. As I said, 37lb/min.

Steven

 

[patsdsm]

Do you guy think that I would be fine with 15 psi.

 

[donmagicjuan]

Do you guy think that I would be fine with 15 psi.

Some people have gotten away with running this much on stock injectors with an EvoIII, but remember that every setup will be different. I certainly wouldn't go much higher than this without upgrading.

 

[scottsee]

I would stronly suggest getting a pocket logger if you want to run effecently. 15psi "should" be ok.. Who really knows untill you log a few 3rd gear pulls..

 

[fastasleep]

Do yourself a favor and buy THIS. Since you're asking for speculation and opinions, that's all youre going to get. If you want to risk your motor on speculation from the internet then be my guest, but no one here, including yourself is going to know EXACTLY how much boost you can run until you LOG.

 

[DSMSpyder99]

with all my mods in my profile (stock 450cc) i run 15psi and have about 18-19 advance timing with 91 octane. When i run 16psi it pulls a lil timming 1-2* depending on the weather outside.

 

[chicagoavenger]

Do you guy think that I would be fine with 15 psi.

Are you not getting the point? Get a logger and find out some people are fine at 19psi some run lean at 12psi because each car is different. There is no "safe" limit unless you know what the hell is going on with some type of logger