FlyYellow

Well did my dyno tuning with the adj. fuel pressure regulator & had an interesting experience.

I was able to squeeze out a bit more power out of it but not much as far as max. hp. (from 256-258), but much more importantly i was able to get more torque & hp throughout the RPM band.

It seems that no matter what we did the max power was fairly constant 254-258, but the power & torque curve in the 3000-5000 rpm band changed....

I'm happy with my result. Car is very smooth on the road...

I'm also enjoying my new DACH sport cats - thanks chris.

Cheers,
Boris

viperbob

That is great Boris. I told you that the fiel pressure adjustment would give you good results... What PSI setting yielded the best curves for you car?

993inNC

Congrats Boris Thank you for the purchase and all your hard work. Can you post either a dyno run sheet or your values and what changed. Rumour has it through someone I know, that a shop buddy of his in town has the ability to get sofware (?) to tune through the ECU that we can play with on his shop dyno. I'd love to see what you have for values vs. what we may be able to change. I haven't had time to contact him yet, but its on the list for first of the year.

SwayBar

Good job!

What was your resultant air/fuel ratio across the RPM range?

FlyYellow

it appears that about 12.5 to 1 is where the car is happiest (generate most power & torque). The challenge is that the computer adjust to richen the mixture in WOT so we had to play with what is the best starting air/fuel to end up with the correct curve. So our best starting position was about 13.2/13.3.

I don't know the fuel pressure (as they did not have a guage to measure it). It was just a little bit richer than stock (+1.5 turns on the adj. fuel pressure regulator). I'll have to scan in the dyno runs. But i did get significant hp in the mid band.

Cheers,
Boris

SwayBar

Tom W

So, Boris, autox only or will we see you out at the track next year?

Brad '95 C4

Boris- Great news on AFPR. Any chance you could post some sound clips of the new exhaust? I haven't had a chance to make it to Devek.

Thanks, Brad

TheOtherEric

Boris,
Can you give the brief idiot's guide to tuning with fuel pressure? i.e. were you custom tuning your chip, or instead just tweaking the fuel pressure? After tweaking the fuel pressure, do you have to leave this regulator in your car, or do you remove it? I'm just trying to understand what equipment is needed and what's involved.

And most importantly-- how much did your 3k-5k torque increase? Something like 10%? 20%? More?

Mark in Baltimore

Nice work, Boris! Thanks for the effort!

FlyYellow

i'll scan the charts and get them posted. but if memory serves me correctly it was about a 10 hp & 10 ft/lbs gain in the mid band. that's very significant (IMHO) because you are adding 10hp to something a lot smaller than 255, so it is awesome.....

as for equipment. you purchase an adj. fuel pressure regulator. you install it (takes 30 mins). it goes behind the plumbing for the heater near the fuel rail.

process: we did 3 dyno runs at each setting. we kept enriching the fuel (by adding higher pressure) to get the best balance power/torque curve possible. each dyno run also gave us an a/f ratio map vs. rpm. it seems that the car generates the most power around 12.5. however if you start at 12.5 the computer in the car seems too stupid to realize it is rich enough and at WOT it would continue to enrich the fuel. then i'm running way too rich and will foul the plugs quickly. so i found that if i started in the mid 13.x then it would give me a balanced curve around the 12.5. i wish there was an easy way to hook up an a/f setting to the computer so that it would know not to continue dumping more fuel, but can't ask for too much.

nevertheless, it seems to have worked well..

cheers,
boris

JasonAndreas

The ECU will adjust for partial throttle but only so much. If you go too far with the regulator and the ECU can't bring the AFR back to stoichometric it will throw fault code 23. Cold starting operates the same way as WOT so that will also be screwed up, actually even more so. It would be interesting to see your fuel trim values before and after the dyno and a hundred miles later.

You would still need to adjust the timing, changing the AFR on its own doesn't appear to do much of anything?

FlyYellow

i would assume the timing is done by the chip. I have a GIAC chip.... it sounds like this may not be as good idea as it thought. but our adjustment was fairly minor. anyway will post charts soon enough.

troppo

so where did you get the adj fuel pressure regulator? cost?

thanks-

FlyYellow

As promised here are the dyno runs...


The plot below demonstrates the additional benefits that i received by adjusting the fuel pressure regulator. The end result was a +1.5 turns toward richer from factory setting.




The second plot below shows my before DACH X Sport Cats & Adjustable Air Fuel pressure regulator install. DISCLAIMER: THESE RUNS WERE ON DIFFERENT DAYS. THE TEMPERATURE WAS MAINLY THE SAME BUT THE ORIGINAL RUN WAS TAKEN WHEN IT WAS RAINING OUTSIDE AND THEREFORE THE HUMIDITY WAS MUCH HIGHER (86% VS. 40%). This is why i put a big do not publish because i don't want people jumping to assumptions because there were multiple changes made to the car spanning multiple days.

But for those of us who want to talk about the graphs and results in this context i'm happy for us to debate, chat..... yada yada yada...




Enjoy...

Cheers,
Boris

PS Sorry about the quality of the scans, their printer was low on ink.