b727pic

iTrader: (1)

I agree with your assessment, as you can see the AFR was pretty good up to just past 5500 RPM where it starts to go pretty rich. I plan to make these adjustments prior to the next dyno pull.

currently I am running a 75/25 mixture, tried 100% meth but wasn't getting the cooling I wanted. a bad by product of spinning the impeller to max was very high IAT's (150-165) during the summer months with ambients around 100*.

Thanks for the input, will post results as they come in....

C/Performance

Run the meth 50-50 and your IAT will go down quicker and run cooler and the pcm will add timing.
Then you know your METH IS DOING ITS JOB !
Then you back down the timing.
Its a time consuming process.
Also when the car is on the dyno take the air filter off, its a major
restriction at wot.It will suck it closed.
Do not overtighten your blower belt,as time goes by, it will take out the bearings on the blower.
Seen it happen.
Something to keep in mind:
After 12 to 14psi your belt will start slip and if you cog the blower, the blower is history within
a couple thousand miles.

b727pic

iTrader: (1)

ahhhh.. the perils of FI, gotta love it! I have been tweaking on this car for nearly 5 years.....it never seems to end, always something that needs to be adjusted / replaced for what ever reason.

white01ss

iTrader: (37)

134 kPa is 5.1 psi not 9.3! You should see around 165 kPa for 9 psi.

I can't read your logs, but going richer than 10.5:1 can kill power in a big way. Also, look for kinks or restrictions in your intercooler piping. They can limit your power yet the boost graph will look fine. NGK 7s are a good plug for your power level.

b727pic

iTrader: (1)

Thanks for the correction, did a little research and found the flaw in my math Actually I am quite happy about that, since around 5 lbs is what I wanted as part of my quest to figure out what is happening with my setup.

Aside from the pulley change out, I am going to go ahead and install the tr7's gapped to .028, street tune where I can, then back to the dyno and see if anything changed in the upper RPM.

98Z28CobraKiller

iTrader: (17)

What's happening on the dyno you should be able to feel on the street. If you can't, then it's probably load related (like a clutch slipping or a converter if you had one).

b727pic

iTrader: (1)

tires are spinning at the speeds I am talking about, so in reality I guess that is a no load situation. very difficult to find a 235 tire that is going to hook at these power levels on the street

b727pic

iTrader: (1)

Back on the dyno today with some changes made.

1) Removed TR6 plugs installed TR7's gapped @ .025
2) Meth disabled
3) Tweaked AFR to 11.5(ish) on the dyno
4) pulls made with 12 PSI pulley and a 5 PSI pulley.

Results: While the graph was a little more linear due to the AFR clean up, power still drops off considerably around 5500 RPM.

At this point I am eliminating the exhaust / header theory, as they same issue exists whether I am pulling 600+ or 450HP.

I think its also fair to eliminate the valve float theory for the same reason as the exhaust. same issue with very low boost pressure???

Car runs smoothe thru the pulls, however power just simply starts to fall off a cliff at 5500 RPM.

My current theory is this:

In both my 408 and now the 403 the same issue existed. In both cases I had installed the cam "dot to dot". I have seen and heard of cases where just being off one tooth has had similar results. So even assuming my "dot to dot" is accurate, I am planning on tearing into front of the motor and actually degree the cam. If that doesn't show anything significant, I suppose at that point I should toss another cam in and see what happens???

I am wondering about affects from bad sensors....ie cam and crank? as stated the car runs smoothe, so no ill running effects that I would think would be evident from a bad sensor??? I guess before I tear into the motor too deep, I should at least pull the crank and cam sensors....not sure what I would be looking for other than obvious damage?

What about reluctor wheel runout? I can see how RPM might play an effect on this, how does one go about checking runout at RPM???



Need input....what are your opinions??

C/Performance

If you run the car all motor, does the power drop at 5500?

b727pic

iTrader: (1)

We didn't try NA on the dyno today?

I would have thought by reducing my PSI as dramatically as we did should have all but eliminated most of the previous theories. I have to pick up the chart later (ran out of ink) but I couldn't have been pulling more than 3.5-4 PSI @ 5500RPM when the power started to drop. Boost doesn't seem to impact the point of hitting the wall....its seems to be RPM related regardless of airflow?

Bob@BruteSpeed

iTrader: (16)

Ron, when the cats blew out did you check your mufflers to see if the innards from the cats clogged them up? Bob

C/Performance

Does your fuel pressure stay steady at 5500rpm?
Did you try running the car open headers?

99bluefirebird

iTrader: (8)

That is a gnarly long turn and piping (3" I assume) going into the blower, I bet the P1 just can't produce enough suction to flow air for more than 5k rpms. And when you slowed the blower down it still cant make the suction. Take that inlet off and I bet you gain 50-100rwhp.

b727pic

iTrader: (1)

Hey Bob,

Well they were metallic CATS the brick melted on the front end, but nothing came out the back. I cut the CATS out of the old midpipes (gonna weld in the new ones) and the back of the bricks were intact.

Great thought though appreciate the input.

b727pic

iTrader: (1)

Fuel pressure climbs on a 1:1 ratio with boost. I log this data with HP Tuners all is working well in the fuel department.

Have not tried open headers....

Here is my thought on this. When I bought my procharger kit from EPP (Bob), I bolted that system on to a bone stock new Ls1 made 450 to the wheels with absolutely everything else being stock!!!

having added the JBA shorty headers, catless mids, and a Magnaflow catback one would think flow should have been improved....not hindered? I do have a Stainless works 3" catback that needs new muffs installed. I suppose I could blow the dust off that setup and see what happens.

I just find it very curious that I keep hitting the wall at the same RPM, regardless of airflow???

b727pic

iTrader: (1)

Point taken: Although that intake setup is pretty well documented on the GTO Boards without any issues? However that being said, its an easy thing to pull off on the next dyno session.

I thought about doing it today, but I am leaning away from "airflow" related theories in favor of a mechanical issue. Keep in mind this "issue" is the same as it was with my 408 install, and at that time I didn't have the "intake" mod as it currently is installed, yet the wall was hit at the same RPM???

BlueThunder2

iTrader: (3)

If you decrease your timing to 15 degrees and an a/f ratio of 11.95 how will she do?

You know, I had a customer's 2004 GTO w/ a P1SC do something similar to me when the Maf was still part of the tune. Once we did a true speed density, no more issues. Above is the final a/f and timing on the tune we did. Over 600 rwhp, never lags, never studders, never plateaus all the way to redline. But, this was a heads, cam, p1sc LS1.

Otto j

Bypass the blower and run it on the dyno and see if it will pull higher without issue.
If so double check your springs,pressure and installed height.
If you can get your hands on a height checker pull a spring and be sure of your installed height.

GrannySShifting

iTrader: (10)

that will cut the curve head off, it wont make it plummet.

valvefloat or other valvetrain issue, or ignition. And its not plugs, making 5 lbs of boost tr6 and .035 gap will light it off fine, much less 7s and .025 gap? It still has ind coil per cyl right

I dont have to close my gap with an out of the box .032 gap plug making @1000 hp burning 100#/hr worth of e85 at 19 psi

GrannySShifting

iTrader: (10)

being off a few degrees in cam timing will move the curve forward or bck, but it wont make it crash.

Why do you have silly rhoads lifters? Sure they arent pumping up or bleeding down drastically? Run virtually no preload one pull and see what happens