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According to Clark's Garage the stock fuel pressure is 2.5 bars for all 8V cars, so he'd need even bigger injectors.
That's a great calculator!
Personally, when I was in a "lean" bind and didn't want to wait for an adjustable regulator I installed a 3 bar & it made a significant improvement in fuel delivery. When from 14.5:1 to 13:1.
Power went way up, I think I was very close to the 200 hp mark with stock injectors, but only after the 3.0 bar.
Michael...he could be maxing out DC and running leaner AFR at high rpm.
Lean does make power, to a point. His expert tuner should be able to optimize AFR. He does have high CR and head work, things that reduce the need for peak timing...
Also, the 1989 ran on a 3.8 bar FPR like the 944S/S2.
My Fuel pressure Reg and Dampener is the same unit as the 924S 2.5 1987 which is 2.5 Bar I think?, it's definitely not a 3.8 bar as the 2.5S / 2.7 /S2 944 unit..
What I find amazing and incredibly annoying is putting multiple spaces between every sentence. It makes your posts read like a bad episode of Start Trek.
Can I get a cliff notes update on what is going on in all these threads? Is someone claiming the stock AFM barn door can meter the air and be tuned as precisely as any modern system?
Thanks Hacker....Yeah Star Trekkin!!!
Cliff notes? I'm guessing this is like a Summary ?
This project is a Road / Street car, non a turbo and I wanted better low and mid range torque, NOT the highest horsepower figure at 6000rpm +
Hence the people I found and was led to, advised me the best system for this application I wanted was to stick with all the Stock BOSCH ignition system etc...
Many times over 12 months I asked them and mentioned so many different components that I was thinking (Like many) needed to be changed and upgraded...
The answer every time was, YES they can fit them but there will be no gains for my intended street use.
Hence I succumbed in the end and went with their advice..
The results are spectacular, far more than I expected...
But you can Imagine the guys in the know...were kinda considering saying "We told you so..." but they didn't because over 25 years you can imagine they have pretty much seen and heard it all from multitudes of people who think they know what they want and what it does..
So from this I think it's fair say that on my N/A application for road use I'm informing the Anti AFM Squad that the UK guys here that have decades of tuning these engines were correct, as it's not only performed
well but exceedingly well..
I 've looked and considered many other systems, UK and worldwide over a 4 year period
Nothing seems clear cut enough, the costs are high and some members here and other people in other places have expressed difficulties.
The differences on power graphs are not much more than a remap / chip and I'm sure many other members too are not convinced but they don't want to get involved..
So having gone with the experts and then seen my 2.7 8v engine fettled meticulously for 8 hours, and starting the day at 179bhp and ending at 205bhp / 205 Ft Lbs. I can now report with great vigour that those that have fallen for the myth's (Easily done) that the stock ignition system, Injectors and the AFM etc..etc.. are terrible and simply cannot produce these results....
Are wrong, because the results are real.
Other people can now still consider them with more confidence when looking to tune their engine.
R,
Do you understand fuel injector sizing? This is not "overthinking physics", this is a fundamental tuning concept. If you don't understand the relationship between fuel flow, AFR, and power, go to this link and click on the shortcuts at the top of the page: https://www.rceng.com/technical.aspx Seriously this is good stuff to know, I'm not being a smartass.
Going to that link, here is a calculation for your injectors.
You have a stock 2.5 bar FPR so that's your rail pressure. I used the posted value of 236 cc/min as per Clark's garage. The first few lines show the pressure adjustment: this is because the 236 cc/min is at 3 bar, so for a 2.5 bar system, the actual flow rate is about 215.6 cc/min.
Here...I'll give you a 45% BSFC (which is super optimistic for an NA engine and means relatively high power level from a relatively small amount of fuel).
To support 200 bhp on a stock FPR, you would need injectors more than 1.5x larger. Fact.
80% duty cycle is standard but you can re-run this with whatever you want, and see that even 100% doesn't work. This model doesn't accurately reflect DC past 80% because after that, the injectors are static and the required injector size is too low - which makes this calculation even more conservative for this purpose. and yet, still can't make 200 bhp.
I really think this is a cool build, but I'm sorry...that's an over-adjusted dyno sheet. Your engine cannot physically get enough fuel to produce that much power. These are just the facts.
R,
Do you understand fuel injector sizing? This is not "overthinking physics", this is a fundamental tuning concept. If you don't understand the relationship between fuel flow, AFR, and power, go to this link and click on the shortcuts at the top of the page: https://www.rceng.com/technical.aspx Seriously this is good stuff to know, I'm not being a smartass.
Going to that link, here is a calculation for your injectors.
You have a stock 2.5 bar FPR so that's your rail pressure. I used the posted value of 236 cc/min as per Clark's garage. The first few lines show the pressure adjustment: this is because the 236 cc/min is at 3 bar, so for a 2.5 bar system, the actual flow rate is about 215.6 cc/min.
Here...I'll give you a 45% BSFC (which is super optimistic for an NA engine and means relatively high power level from a relatively small amount of fuel).
To support 200 bhp on a stock FPR, you would need injectors more than 1.5x larger. Fact.
80% duty cycle is standard but you can re-run this with whatever you want, and see that even 100% doesn't work. This model doesn't accurately reflect DC past 80% because after that, the injectors are static and the required injector size is too low - which makes this calculation even more conservative for this purpose. and yet, still can't make 200 bhp.
I really think this is a cool build, but I'm sorry...that's an over-adjusted dyno sheet. Your engine cannot physically get enough fuel to produce that much power. These are just the facts.
Sure, I 've been waiting for something like this, it was inevitable.
R,
Do you understand fuel injector sizing? This is not "overthinking physics", this is a fundamental tuning concept. If you don't understand the relationship between fuel flow, AFR, and power, go to this link and click on the shortcuts at the top of the page: https://www.rceng.com/technical.aspx Seriously this is good stuff to know, I'm not being a smartass.
Going to that link, here is a calculation for your injectors.
You have a stock 2.5 bar FPR so that's your rail pressure. I used the posted value of 236 cc/min as per Clark's garage. The first few lines show the pressure adjustment: this is because the 236 cc/min is at 3 bar, so for a 2.5 bar system, the actual flow rate is about 215.6 cc/min.
Here...I'll give you a 45% BSFC (which is super optimistic for an NA engine and means relatively high power level from a relatively small amount of fuel).
To support 200 bhp on a stock FPR, you would need injectors more than 1.5x larger. Fact.
80% duty cycle is standard but you can re-run this with whatever you want, and see that even 100% doesn't work. This model doesn't accurately reflect DC past 80% because after that, the injectors are static and the required injector size is too low - which makes this calculation even more conservative for this purpose. and yet, still can't make 200 bhp.
I really think this is a cool build, but I'm sorry...that's an over-adjusted dyno sheet. Your engine cannot physically get enough fuel to produce that much power. These are just the facts.
As much as I like your reasoning, there's a problem with the calculator:
The 944 Turbo S would need a 542 cc/min injector while it had a 384. The difference is 1.4x.
To support 250 bhp on a stock FPR in a 944 Turbo S, Porsche would need injectors more than 1.4x larger. Fact.
I have to agree here..plugging in the info of a stock healthy 944 at 150hp and 2.5 bar FPR, the calculator says ~24# injectors (~250cc) at 85% DC.
It seems to work better for NA stuff, the ROW 163 bhp car will work with 90% DC and BSFC=0.45 with a 234 cc/min injector. Stock is 236.
The Turbo S will also get 250 bhp with 90% DC and BSFC=0.45 with 361. Stock is 384.
When I was looking at injectors for my engine I found on this board that NA injectors were pretty much maxed out in the stock configuration. If memory serves 90% DC was actually mentioned.
Regardless of the calculator, the stock injectors are pretty much maxed out from the factory. I think this is an interesting choice from Porsche. Why didn't they leave a larger safety margin? Why not use a 3 bar fpr?
08-24-2016, 11:09 AM
I 've been waiting for something like this, it was inevitable. 
