merchauser

Bill, I think you make a very good point, and I can't deny the facts of my first post!

what I could do, is run this tank down, and put it some Sunoco 100 octane race fuel. does the group think this would be a good test??

Speedtoys

And,,partially anecdotal and missing a _shedload_ of data to prove how same or different the car was operating/operated.


Because we know..the fuel comes from the same terminal tap, with changes in detergents, not energy or octane capacity, added after the fact.

The Scientific Theory -is- useful, but only if you follow it. Nearly blind observations of a result, does not lead to any conclusions.

Buy some PEMs, borrow a ST, do science.

Speedtoys

No.

Because you're changing conditions...obviously 100 will knock less than 93, but you already have a 0 result, another 0 result with different parameters is a waste of money and time.

Chase this down with a solid set of data points, and a tight methodology.

jcorenman

Yes, same spigot but there are certainly differences. Paul (merchauser) here, also Bill (placer), hard to argue with audible knocks in a DD, we've seen it also when tuning our GT. Fuel is the same when delivered to all the stations on the same day, but I haven't heard anyone say that the fuel is the same from one week to the next. And some stations get deliveries every few days, others much less so. And refineries are switching to winter fuel in some parts, so there might be big variations depending on when the tanker shows up. No data, lots of variables.

I think the best test is to stick to one station, find out when they get deliveries and record that in a notebook, and then repeat the same test-drive every time you refill and note the ambient temperature, barometric pressure, humidity and knock-count and record that also. The Sunoco race gas would be boring because it won't knock at all. But if you had a Sharktuner then it would be fun to see how much timing you could add and how much more power you could make at the local dyno. Slippery slope, this is.

merchauser

above points well taken;

Speedtoys, only reason I am not pulling the trigger on ST, is that I want to install X pipe first, and with this and other projects on the table,
that won't (can't) be until after the new year. also, X pipe gives me the second bung for the wide band

for the moment, a friend with tools (FWT) is going to help with vacuum, fuel pressure, and smoke, tomorrow. I have the correct specs
for fuel pressure, (thanks fred) for not running and idle. is there a test for fuel pressure under load? at certain RPMs? useful or irrelevant?

any other specifics regarding vacuum tests: should I test each dampener separately, as well as the FPR? other vacuum tricks?

merchauser

FWIW: just to remove all doubt, and any possibility that I might have any sort of combustion leak, I picked up a block tester
kit with dye. all good; no issues.

jcorenman

The important spec is engine stopped, pump jumpered: 3.8 +/- 0.2 bar (55 psi +/- 3). The reason for engine-stopped is no engine intake-vacuum, which will change (reduce) fuel pressure to maintain a constant delta-pressure across the injector (which also sees intake vacuum). The pressure at idle is "approx 3.3 bar", which simply confirms that the FPR is connected to engine vacuum. Fuel pressure with the engine running is highly variable depending on engine vacuum, and not useful. You already tested that the pump is delivering all the fuel that a stock engine can possibly use (2.5L/min), that checks the flow through the whole fuel system (pump-filter-regulator and back to the tank).

The check for the two dampers is that they are not leaking fuel out the vacuum port. Disconnect the vacuum line and sniff, or disconnect the vacuum hose and route a small hose from damper's vacuum port to a catch-can and jumper the pump (with engine stopped).

This is from the '90-95 Tech Spec booklet, don't try to work on these cars without one:

merchauser

^^^^^^^thank you jim very useful information. will report upon completion.

a little more "testing" this AM: first step was to check my idle contact, and WOTS. idle fine, WOTS not working (not closing, stays open).
outside temps 65F. started the same way, lightly pushing down on pedal @3000, 4000, and 5000, and all readings were 0.

then I gave it the full monty, and got 18. pulled over and again checked WOTS and it was not working. stomped on the pedal and got
WOTS to work, another full bore run, and 18??

of course I cannot be CERTAIN, but I made many runs, and it "appears" that it makes no difference whether the WOTS is working or not.
does that provide any additional clues?

then, being Halloween, I journeyed to that special Shell station, and juiced her up. (ran fuel level down as far as I could) even went to the same
pump, #7.

performed all of the mentioned tests, and nearly identical results.....so no magic syrup at that store.

questions of the day, are nearly the same as before:
-what might have occurred to get those ZERO knock results?
-why am I not getting any different readings with WOTS working or not?
-and, hypothetical, WHAT IF, I put in super 100 octane fuel, and got the same results?

SeanR

Have you done that intake refresh, that everyone has been telling you that needs to be done, yet?

merchauser

com' on, sean...I thought you spoke with roger everyday..lol. intake refresh is done, as well as knock sensors, hall, CPS, MAF, O2, fuel pump
and a lot more....

really appreciate all the insight provided thus far. hoping you might have an idea of where to go next??? gimme a new direction.....

928S MN

Only thing I have is to install a wide band O2 sensor and see what the air fuel ratio really is. Running lean will tend to cause knock. Maybe you have a "weak" injector.

merchauser

thanks for chiming in 928S MN. agreed, I need to see the AFR. X pipe would make me happy, and has the 2nd bung for a wide band. I sent out the injectors for cleaning, and they are all
in spec. unless, one injector is not firing, but I took a stethoscope to each one, and they are clicking properly. not sure what else might create a lean condition??

928S MN

X-Pipe O2 bungs only read one bank of 4 cylinders. At least that's how mine is.
Maybe go to a Dyno shop, which should have the wide band O2 wand they stick up the exhaust so it reads all 8 cylinders.

Speedtoys

EOM

Speedtoys

Eh, gather data now, the use it again. It will also gather easily a single channel of WBo2, and with some work on your side..you can input a 2nd channel of WB02, as well as other things, if you need to, but generally dont. On a set of new known fresh injectors, one is enough if you can hear all 8 clicking then.

Your only investment will be PEMs.

It was brought up earlier..have you done a full intake system refresh?