1G fuel curve and an IPW question that is related

[Van]

I got my logger :D
OK, In the "prelogger days," I've always thought that I noticed a lean spot in the factory fuel curve right around 4500 rpm.
I noticed (or imagined) this after the full exhaust mods, intake mods, higher boost, etc., via EGT's and O2 volts feedback. The logger seems to confirm it, at least on my DSM anyways.
I'm now wondering if any other 1g'rs have seen this? I think it could/might be only a 1g thing...not sure. Basically what I'm getting at is that you need more fuel (highest s-afc settings) at right around 4500 rpms. Anybody else see this pattern? I know that each car is different, just wondering...

I currently have a 2g mas on my '91 DSM with the stock 450 injectors and the 14b. The highest IPW I've logged, only once so far, was 18.974 ms. I can maintain at least 15 degrees of advance at an O2 voltage of .86 all the way. Right about 4500 rpms is where I need the s-afc set highest to maintain this .86v. At about +22%, this 18.9 ms isn't very high, basically 70% duty cycle according to this. http://www.ecanfix.com/~mdhamilton/dutycyclechart.html
But, I'm thinking maybe I should raise my fuel pressure to the 2g rate, so that I wouldn't have to be so high on the s-afc % for now.
The injectors clearly aren't maxed, I already have a walbro 255 rewired, the higher +% I go with the s-afc the closer I'll be to fuel cut; so should I just slap in bigger injectors or raise the fuel pressure to the 2g rate first? What is the popular vote?

Future turbo mod will be the Green model...



[Edited by Van on 06-15-2001 at 05:15 AM]

[Rdy2race]

wait on the Inj as the green will demand a large inj that you can't use now.

The stock Inj are 450CC @ 42PSI rail pressure.

this car has a 36PSI rail pressure so they are not even 450s!!!! AHHHHH!!!!!

heheheh

What i am getting at is yes the fuel pressure is a bit low. this was done in a effort to help spool time as it will be a bit leaner then normial if the rail pressure was @42PSI

With that said your @ 70% but not using 450's really since they are metered at 42PSI not 36.

Bring the rail pressure up some and see how she goes.

Yes I also have seen this lean problem on almost every car. From 3K-4500 is where the acr starts to come alive. From the boost kicking in to the cams coming on all this stuff takes place around this point. What I have seen is that the hacked MAS don't like this at all and tend to keep it lean down low till the fail safe fuel curve that Mitsu installed kicks in. ( gets richer with RPm no matter what is going on.)

With this I also would like to say the timming needs to be looked at . Feel free to send me your logs for review VAN ( not everyone I love my pocketlogger don't you. I LOVE TOYS!!! =-) I don't think that your getting the timming that your looking for. The small advance that I am seeing is showing me some this is not right.

BM-

[Van]

Hey Bill thanks,
I'm gonna try to get two cleaner WOT logs today, my first run was kinda "messy," hehe.
At idle my timing was about 8 degrees, during cruising I get 35-38, when decel it'll go 44-45...Upon wot I'll get 23-25 degrees and then as the rpms climb I've tuned her to maintain at least 15 degrees, usually 16-17-18 degree range with knock sums below 5. But to get her there, the Hi throttle s-afc settings had to go up and I turned the boost down a little bit.

Hence my question about the raised fuel pressure getting me some s-afc settings room for now.

On that note, next question...
I do not have a fuel pressure gauge yet, what might be the cheapest/safest proven method for now to raise the fuel pressure?

When $$ is available, I plan on doing the stevetek line upgrade, an SX regulator and an electrical fuel pressure gauge.

[Rdy2race]

the quick cheap O one is the AT DSM FPR as I think that is a 42 # one or was that the NT one??) but some other DSM FPR's are 42# stock. B&M make a adjustable FPR for this car. not the best but no worse then factor and it's adjustable.

Tip: Always use a liquid filled fuel pressure gauge or a electric gauge in the car. I say liquid B/C of shock from the road will bust it and the motor makes it shake, the clear oil that it is filled with will stop that. They are about $35 from Earl's ( Earl's Lines.. and if your in NY anybody or close to do you know of a Earl's Dealer?? I have been missing my Earl's dealer since I moved from San Diego back to NY.)

[Le Talon]

Or a 2G turbo FPR. The only problem is that you need the fuel rail as well, the 2G FPR just won't bolt on a 1G fuel rail...

[Van]

Now that pintle vs disc is solved...at least IMHO.

I've been researching the digest archives, and there only seemed to be one common thing/problem. Too high of fuel pressure at idle, this would happen when installing a higher
flowing pump that overruns the stock fpr at idle.
What is generally needed is to be able to lower the pressure at idle with an SX or a Paxton adj. fpr. And it seems to be more of a problem the bigger the injectors you run, or you start fighting minimum injector pulsewidth at idle. ARRGGHH!

I've been considering installing a 1G A/T FPR. (Cheap for now.) This will raise it to 2G fuel pressure levels, 42.7 - 43 psi. For me, it *shouldn't* be a problem at idle, with the stock injectors, the 2G mas and the s-afc and gain me some room up top (again for now.) But I'm thinking bigger injectors would be the right step and leave the pressure alone.
I REALLY hate to do things twice...I hate to undo something I just did even worse!

Any input/experience on say, 660 injectors with 2G stock fuel pressure at idle, with the newer s-afc and a 2G mas on a 1G and fighting the minimum injector pulsewidth issue?
I'm thinking of future mods here...
There is virtually no info in the digest archives about 660 injectors with 2G fuel pressure and IPW issues at idle, on a 1G.