1NSIGHT

iTrader: (3)

I just want to post some info for some of the users who are modifing there cars for more hp. And give some numbers to keep them from blowing their motors.

My car has a new street ported motor with an s5 turbo and stock injectors and an areomotive fuel pump. I have a 3in exhaust from the turbo back and get some boost creep because if it, and the street port. I wanted to know the limits of the stock injectors before I put in my 1000IDs. So I maxed out the injector dwell on my Haltech and did some pulls.

At 4100ish rpm and 16 psi the AFRs left the comfort range for me of 12.5. Intake temps at 64 degrees F. And below that point at 3600 rpm I hit the boost cut set at 16psi. 4100 rpm is relatively low in the rev range and I know that most gals and guys dont have new street ported motors but I just want to give a lil first hand account on the limits of the stock turbo wastegate and the injectors rather than the heresey I sometimes read.

So be careful of going for more power without the supporting mods. Fuel is important for these motors.

7speed

12psi

1NSIGHT

iTrader: (3)

Im not asking a question. The jist of the post was to insert that boost creep happens and that the bottom line limit of the fuel system is 16psi at 4100 rpm. So that if you expect you may be getting boost creep and dont have any monitoring systems as far as fuel ratios go, thats the point of no return.

RotaryEvolution

iTrader: (30)

boost level is independent of limit to the fuel system, airflow at the boost level is related though.

a stock top mount intercooler will have a larger pressure drop due to restriction than a larger core intercooler. a larger intercooler will allow the turbo to make more power at the same boost level. the same goes for exhaust restrictions.

fuel limit is dependent of power potential of everything you have bolted to your car, so the question is flawed.

your wideband is already telling you the answer, although a skewed one. because the injectors haven't even finished staging by 4100 RPMs in lower gears due to lag in the readout. you should have more RPM limit than that but your staging is obviously weak.

basically speaking, boost pressure is irrelevant unless comparing completely similar setups, ie stock cars. in which case 10psi is about my limit on a stock setup and not because the fuel system doesn't have more room, other things have their limits in that range such as the ECU mapping and the FPR. if the car has a standalone then you could push 13-14psi before reaching a stock limit.

i suggest porting the wastegate and doing research into fixing the injector staging before going further. 12.5:1AFR isn't a horrible figure but it could obviously use some seaming help.

1NSIGHT

iTrader: (3)

All 4 injectors were at a high duty cycle. The staging is fine. My setup is similar to what alot of people may have. Which is mostly stock. I did the run multiple times. Im not posing any type of question just trying to give a first hand account to the limits of a stock setup. I know every engine is different and there are factors that I didnt mention. I was trying to give a possible scenario for what your boost levels could spike to and if they do what are the limits. There are a lot of post talking about what the limits are of the stock system and not much concrete details. I wanted to provide some definite info on the matter.

If any person has a large exhaust and street port they will probably have similar results as mine.

Maybe I should have posted my datalog.

RotaryEvolution

iTrader: (30)

you'd be better off posting a list of mods and the power level and corresponding duty cycle along with RPMs with all the relevant data.

it seemed like a question, one to which your car will tell you the answer to. each car will give a slightly different answer so that is why there is uncertainty as to the answer. fuel makes power so fuel limits power, those 2 factors will be about the closest to certainty between any 2 cars given. how much power the setup can make will determine the fuel requirements/limits. the stock fuel system can only really make about 235whp before being strung out, beyond safe limits. a standalone can push this number slightly higher but the pump(stock TII) and injectors again will reach a crossing at close to 250whp.

so basically you're reaching about that figure at the points you gave. at roughly 7,000 RPMs the fuel requirements begin to drop on most cars so 7k is usually going to be where your fuel system needs to maintain to(on highly modified cars that can breathe better the number will be higher).

raising base fuel pressure can bandaid fuel injector volume to a smaller degree.


so as you can guess, the variables are almost limitless.

1NSIGHT

iTrader: (3)

Aeromotive stealth fuel pump, 3in exhaust, Grimmspeed boost controller set to 0 psi, New street ported motor. My pulls were in 5th gear I wasnt on a dyno. I dont know the exact duty cycle it was around 80 or 90.

The initial point of this thread was to note that some guys might modify there cars like i have done but may not have accurate means of measuring boost, injector cycles, whatever. (ie keeping the stock ECU) and that they may experience the boost creep. And that boost levels can go well past the safe levels for their cars.... the 16psi + that i am getting. If that person has boost creep or a boost spike below 4000rpm and 16psi their engine may live to see another day if not then it'll be time for a rebuild.

Like i said i just wanted to give a first hand account as to the limits of the fueling system. Alot of people have said the same things that Im saying about not pushing past 14 pounds and boost creep, ect. This my PERSONAL account on those same notions for anyone with the desire to know. Im not saying turn up the boost and keep it below X rpm; im saying that at THIS boost at X RPM this is what happened to my car and my setup.

RotaryEvolution

iTrader: (30)

yes, even 14psi is well beyond the territory for popping an engine with light mods. many people have blown engines at lower power levels mainly because they're using the stock ECU which is even more limited.

gxl90rx7

iTrader: (1)

i agree boost doesnt matter, its airflow that the injectors cant keep up with. you can make 250whp at 5-6 psi on the stock turbo, which on stock injectors will be too lean

Evil Aviator

I understand your intent, but there are other variables involved, such as fuel rail pressure, ambient air pressure, fuel octane, the condition of the fuel injectors and the engine, the calibration of the AFR gauge, the tune of the engine, etc. This is why there is so much hearsay, and you are unintentionally adding to it. The important thing here is the process by which you determined the safe limits for your particular engine in your particular environment, not the numbers involved.

^ This.