hi,
i have an '87 t2 that i have built from the ground up myself. mods list:
E6K w/3bar
fuel pres gauge
egt (approx 800 deg C under full load)
j&s knock (stupid thing keeps lighting up)
FMIC
full exh.
T78
550 pri
1600 sec
walbro 255
fp reg (44psi static)
street port w/ Hurley 3mm
wideband tuning (cruise=14.4, <5psi=12.5-13.5, >10psi 10.0AFR)

i am writing this b/c i am completely frustrated about the fact that i can still see detonation @ 13psi and up!!! this cost me 1 engine already @ 6000miles!
i think that 93 octane on this set up should be able to support 16-18psi. am i right?? please look at the following and tell me any suggestions that you have:

fuel AFR's= cruise=14.4, <5psi=12.5-13.5, >10psi 10.0AFR

timing= from 3k rpm to 8k rpm- 30deg adv @ 0psi, linerized to 12deg adv @15psi

trail split (>2k rpm)= 10deg @0psi, 2deg @ 5psi, 10deg @15psi (linerized between points listed)

corrections:

timing vs. intake air temp= starting @ 100deg 1deg ret per4-6deg temp rise

fuel vs. intake temp= i have it taking away very little to nothing above 100deg inorder to further richen the mixture

the thing is this engine is NOT leaning out. the detonation is coming from something else. i am baffled. i feel those timing values are already too conservative. can an engine detonate from being too rich? is it possible that small imperfections in the rotor housings/side plates could allow blow-by igniting the next charge? please forward any input that you have. thanks for your time.


justin

513 518 1994

 

pump gas is so inconsistant that running this aggressive a setup is going to be disasterous. Unfortunately you have found that even with good tuning problems can arise. I would not use pump gas on any modified turbo engine, especially one that is run at over 13psi of boost. you can try reducing the timing even more to try and help, but race fuel is really the only way to cure this problem. what are the intake air temps? this is likely the real culprit. intercooler is heat soaked and then you run it wide open and bang the detonation. race fuel is going to have more octane which is resistance to detonation. on my turbo race motor which only ran 10psi of boost I had to run race fuel to keep it alive. it lasted three seasons of racing without any damage. only problem was I had worn the apex seals, but everything else was in good shape. try some race fuel and see what happens. good luck

 

umm, where can you get race fuel from exactly???

 

At The RACE TRACK

Out here in CA lots of Union 76 dealers will sell you race gas in 55 gal drums or dispensed into your own container (it is illegal for them to dispense it directly into your street car) In the EAST you should try your local SUNOCO dealer, their Std. Premium is 94 octane , and I think many may still dispense 101 octane super premium gas at the pump.
It really sucks that we can only get 91 octane pump gas out here in CA

 

I do not know if this will help you but I run a 3rd gen with up to 18 lbs of boost on stock turbos. I am running the highest octane unleded fuel I can get. It is K & S 103-107 octane. That along with all the other mods keeps me save. To date I do not know of anybody else running the boost I do. I have had no problems at all.

Car was tuned by Kogi at XS Engineering to run the boost I said with the fuel I am using.

Hope that helps.

Allan

 

AIR PLAN FUEL. those rate 120. and is much cheaperthan race fuel. the only problem there are lead and my friend tell air plan fuel is different than car feul.
use on my friend car doesnt seen to had problem

 

12 Degrees advance @ 15 psi may be too much for pump fuel !! , you should be around 10deg max or even lower than that.Find out where torque peak for the engine is and retard the timing to about 5 deg at that point , do this at the RPM ranges just before and after that point also from there you can carefully go up a degree at a time , if the gains are minimal then revert to the prior lower value. Advancing the ignition on a rotary doesn't make such a big difference to power but it will cause you to detonate , ask me how I know !! , as for the split I was detonating at 0 deg advance with 5 psi boost because my split was too close!!!.

 

Also scence your building it yourself, check for small burs on the rotor. These can become excsively (sp) hot and cause detonation.