2001 Porsche 996 LS1 Conversion Thread by 1dirtyZ

7 minute(s) of a 276 minute read

as for the mixture its ok at 11.7-11.9 just prior to the misfire , and right after the miss happens it shoots up to 23-24:1 , the pulse width soon follows the afr to try to correct the lean spike then settles back down . fuel pressure acts weird sometimes after a few of the misses and not all of them; the pressure dips about 10 psi after the missfire ,,, i thought that was because of the back fire lowering the boost and thus the signal the regulator is seeing , but boost never drops....

so from the above i can assume that the car is not back firing through the exhaust and not the intake , and it doesn't do it becaue of fuel pressure drop ( the drop in pressure happens after the miss) . so this leaves me with the ignition as a culprit.

i'll try to swap coils first , check the plugs again to see if there is anything to see , and maybe try to move the main harness around to see if it it could be some electric noise.

here is a capture of log :





i also have to adjust the new wastegate actuators ,,, apparently i installed them with zero preload on them which might be the cause of the missing boost

9-20-2016

the holley ecu is set up for closed loop so it does the fuel learning by itself, so technically I have it setup to fix any fueling issues that might pop up like a drop in fuel pressure or a spike in boost.

as for the maf ,,, ain't got none but the map has been re located to the port just behind the throttle body on the driver side of the car. this might cause the issue , but the boost reading and map numbers are steady during the events , which rules out the map getting a faulty signal.
( I did have that happen on my friend's car where the map was located just under the throttle body flange on a holley hi rise intake, and I guess it was seeing some turbulence under WOT which was showing in the log,,, we cured that by inserting a long rubber hose connected to the map so it reads from a cleaned area inside the plenum).

the rpm trace is like that because that is how bad the miss is . the cam and crank signals seem to be perfect. I should run an internal log of the specific signals to see if there is anything funny going on with these.

10-10-2016

been messing around tring to figure out why the car was missing at the top end,, well i did a system log and did a few WOT pulls to see if i can see anything ,,,, and i think i found something. during the misfire both cam and crank signals go flat ,, which rules out the reluctor as an issue ( if it was i would still see the cam signal when the crank signal would drop off.)







so this leads me to believe that i have an electrical issue somehwere along the cam and crank wires to the pcm ,,,, so next step is the wiring diagrams

11-28-2016

well I found out why was the car missing at high rpm's ,,,,
turns out the reluctor started to come apart.

so it was time to drop the engine again ;




and this is the culprit:



so that piece was replaced with a billet CBM unit that was pressed then welded in place. And since I had the engine down I decided relocate the map sensor to the back of the intake to get a clean reading at lower rmp's , I also decided to make a hole in the "fire wall" to run the harness through instead of having it go through the stock location behind the tail light and snake its way around. this way I also have easier access tot he engine compartment if I need to run any other wires later. I also used two rubber flaps to seal the hole along with a ring to hold them in place :




and since I had everything apart I got a chance to inspect stuff; the clutch is holding very well with no signs of wear, same as rod and main bearings .
I did also notice that cylinder #8 exhaust port was leaking oil ,,, which explains the puffs of white smoke I had before ,,, and I assume its just normal guide ware ( normal in the sense that these are patriot heads that I bought around 2002 and had them on my Camaro for quite some time - read " abused " )

so after that it was time to shove the engine and trans back in :



so all that is left now is to finish up the wiring , install the accessories and plumb the cooling lines , and add fluids

I also am thinking of running a new positive cable from the battery to the starter instead of the stocker - been getting a hard to start when hot issue that I could not get rid of so far.

12-21-2016

well I finished putting every thing back together again ,,,, and guess what the problem is still there
so I decided to throw in a new set of cam and crank sensors just to see if it helps , I also relocated the cam harness and used the stock cam harness extension and shield that routs the harness under the engine ( it also made the cam sensor extension not needed in my application ) and that seemed to fix the misfire issue!

so now the car revs to the redline effortlessly , and it hits 17 psi right away ,,,,, and starts drifting sideways in 4th gear !
the thing is scary under WOT , even with the drag radials in the rear.

but that brought out the next weak link in the chain ; the new clutch

kennedy told me that this clutch was good to 750-800 hp at the crank , but when I got it I wasn't expecting this thing to make more than 600 at the wheels , let alone 840.

so for now I guess i'll turn the boost down to 12-14 psi which should help a bit .
and I have to start looking for a solution for my clutch problem .

I need to find a twin disc setup that fits on the stock Porsche flywheel ( since it has the same pressure plate bolt hole pattern as the flywheel I have ) , I remember seeing a setup like that a while ago but can't find it anymore.

anyone have any leads?