how much boost can the stock injectors hold

[myturbo]

ok how much boost can i run on stock 450cc injectors with stock car with 3" exhaust, i have dsmlink i can put in, im only wanting on this one only like 14-17 psi or so, just something to keep me ok till my other car is done,

 

[dannyd97gst]

I've been running 14-15psi with no noticeable problems, of course that is assuming my "Faze" boost guage is accurate. Just my 2 cents.

ps: "Faze" boost guage is crap, very intermitant operation

 

[myturbo]

yeah the faze i had along time ago was a pos, so i decided to spend the extra money and buy a autometer

and do you think the 16 will be ok with stock pump and fpr, i think ill put my dsmlink in since its just sitting around & my aem wideband ugeo and of corse a real boost gage

 

[toofast82]

The stock a/f ratio is in the 9s at wot which is very rich. Leaning out the fuel mixture to say 11:1 on pump will free up some injector duty% as well as power
17psi will be pretty much be at the stock pumps limit with a rewire

 

[2gGSX]

Given the stock 9.5:1 tune, at 43 psi base fuel pressure and assuming 90% max IDC, then theoretically you will max out at 25.7 lbs/min of airflow worth of boost.

 

[toofast82]

Given the stock 9.5:1 tune, at 43 psi base fuel pressure and assuming 90% max IDC, then theoretically you will max out at 25.7 lbs/min of airflow worth of boost.

Curious what formula that you used. This could be of use to me!

 

[Artago]

Curious what formula that you used. This could be of use to me!

Here's a good a write up you may want to read.

http://www.dsmtuners.com/forums/tuning-engine-management/244522-injectors-fuel-pumps.html

Tom

 

[Demon33]

Given the stock 9.5:1 tune, at 43 psi base fuel pressure and assuming 90% max IDC, then theoretically you will max out at 25.7 lbs/min of airflow worth of boost.

1G turbo's have a base fuel pressure of 36-38 PSI. 2G's are 43 PSI. With your calculations, what max air flow do you get with the new 1G fuel pressure value of 37 PSI? Logic says that it be less given the lower fuel pressure.

 

[2gGSX]

25.7 * sqrt(37/43) = 23.8 lbs/min

The formula would be injector size x 4 x s.g. of fuel / 454 (to convert to mass flow from volume flow). I posted this on a writeup I did a long time ago I believe.

 

[Fiascoxl]

i ran 18lbs easily on 450's and 14b with a rewired 255 pump and aeromotive fpr bumped up to 43lbs. I was getting 10:8 to 11:2 a/f's but my idc's were to high at mid 90's and with the injectors working that hard theyre spray cant get erratic

 

[Demon33]

ok how much boost can i run on stock 450cc injectors with stock car with 3" exhaust, i have dsmlink i can put in, im only wanting on this one only like 14-17 psi or so, just something to keep me ok till my other car is done,

I have a similar setup- 3" turbo back exhaust, 14b, 450cc injectors and I boost to 17 PSI. However, I have a rewired 190lph fuel pump. Honestly, I feel greater acceleration at 10-15 PSI than I do at 17 PSI, probably because I'm blowing hotter air at 17 PSI. I'm waiting on a serial cable for my Palm datalogger so that I can verify the air flow, knock count, etc. to compare different boost settings against one another.

I 'think' you should be fine in the 14-17 PSI range you are looking for with the stock fuel pump, but a rewire wouldn't hurt.

 

[zhjiln]

I have a similar setup- 3" turbo back exhaust, 14b, 450cc injectors and I boost to 17 PSI. However, I have a rewired 190lph fuel pump. Honestly, I feel greater acceleration at 10-15 PSI than I do at 17 PSI, probably because I'm blowing hotter air at 17 PSI. I'm waiting on a serial cable for my Palm datalogger so that I can verify the air flow, knock count, etc. to compare different boost settings against one another.

I 'think' you should be fine in the 14-17 PSI range you are looking for with the stock fuel pump, but a rewire wouldn't hurt.

you guys are maxing out those 450s.... 17psi is too much boost...thus your timing gets pulled...thus sluggish acceleration at higher psi...

 

[Demon33]

you guys are maxing out those 450s.... 17psi is too much boost...thus your timing gets pulled...thus sluggish acceleration at higher psi...

While I don't completely disagree with you, I noticed that my car pulls harder and runs better, much better on cold nights even at 17 PSI. I figured that the denser, colder isn't heated up enough by the turbo to be that noticable and my still stock intercooler isn't heatsoaking as badly. If I were maxing out my injectors on a hot or normal day, I should most certainly be making them out on a cold night with the denser air, but the increased performance says otherwise. And I have yet to hit fuel cut at 17 PSI even on the coldest nights.

Without a logger (still waiting on a cable) I can't say for sure if it's air temperature, timing, injector duty cycle, knock, air flow, etc. that's causing the variation in performance. I'm guessing it's a combination of two or more of them, but I won't know until I start logging- hopefully by the end of the week.

 

[Bluefire16]

Yea come to michigan, i had mine running at 15psi and hit fuel cut, it was so cold (like 4 degrees out haha) but yea, turned boost down and was fine, cant wait till it gets warmer again.

 

[habitatguy187]

you guys are maxing out those 450s.... 17psi is too much boost...thus your timing gets pulled...thus sluggish acceleration at higher psi...

Timing doesn't get pulled due to nearly maxing out injectors, it gets pulled due to not having a good enough intercooler/not big enough turbo.

Anyway vfaq says that if you're using 93 octane you can run 18psi with a fuel pump upgrade/rewire.

 

[dsmfa9nutter]

I've daily'd 16lbs with a stock 63t fpr and stock colt pump. This was with a maf-t with mid and wot switches one click clockwise (richer) with excellent results. Bumping to 17lbs or higher results in fuel cut though.

 

[easy]

funny thing about boost gauges, i've had two autometers and they both crapped out on me... not ive got a vdo and havent had a problem yet...

 

[myturbo]

can i run 17 psi safely with what i listed on #1 post and a 255hp walbro i got one that i cant use in my other car

 

[GS ice T]

I ran 18psi on a t25 all day on stock injectors and a rewired stock fp but the engine was built too... and eventually blew the oil seals in the turbo. Im sure there are other factors that would play a role in max boost like how dirty the injectors are and how much oil if any is in the intercooler. I also shifted about 6-6.5k to be cautious. With the 255 and an aftermarket fpr to go with it I'd say 17psi would be fine.

 

[myturbo]

I ran 18psi on a t25 all day on stock injectors and a rewired stock fp but the engine was built too... and eventually blew the oil seals in the turbo. Im sure there are other factors that would play a role in max boost like how dirty the injectors are and how much oil if any is in the intercooler. I also shifted about 6-6.5k to be cautious. With the 255 and an aftermarket fpr to go with it I'd say 17psi would be fine.

well i shift at about 7k and a 14b is alot better than a t25 and i can only do something quick and has to be done tommorrow so .....

and i dont have a boost controller on it and for some reason it boosts somewhere between 15-18 WTF ?

has anyone heard of that im alittle worried, nothing is clogged up ive checked

and it runs lean as hell at idle and rich as hell at wot, and at this momet the injectors are set at 660cc because i havent changed it or tuned it yet because my usb adapter is a P.O.S.

 

[2gGSX]

You're running 450's and have DSMLink set to -31%? Your profile also says you're running 1200's.

 

[myturbo]

thats my other car

 

[myturbo]

so could i run a 255 walbro and a nt fpr ?????

 

[kqodprez]

so could i run a 255 walbro and a nt fpr ?????

Not on your car. That is on the 1g's that could swap fpr's and bump the fp. Just do a rewire and drop in a fuel pump (cost about 120 total). I ran 16 psi on my 1g with just a rewire and 1gnt fpr. I wouldn't push it past there. Just save up and get the supporting mods if you want to have a little fun. Remember to boost safe...or be sorry!