TT chip and octane

[Shimy87]

I have a tt chip, marked 60 lb injectors , 93 octane, 15-17 boost. I think 21 degrees timing but not sure. I can only get 91 octane. When I roll into boost (12 lbs) in drive I get bad knock. I tried adding 6% wot fuel but I don't even get to wot. Will I need a new chip burned for 91???

[Steve Wood]

Under the assumption that it is hearing real detonation and not false, set the third/fourth gear timing to 18 degs

[Shimy87]

I can hear it as well so pretty sure its real, should I set 1/2 gear as well? I punched it from a stand still and instant knock.

Also not sure on the timing marked on the chip, will pull it and check first.......th anks!!

[Steve Wood]

It will not hurt to reduce 1/2 by three degrees from whatever is marked on the chip as well.  18 degs used to be pretty much standard and they sometimes will be faster with 18 degs than with 21.

[Steve Wood]

make sure your fuel pressure is rising with boost

[Shimy87]

Fuel pressure is rising

Chip says 20 degrees - 18 degrees

Also 16-18 lbs boost, seem like alot of boost for pump gas??

[Steve Wood]

I think 15 is pretty good on 91 octane.  try 18-17.  Bob Bailey used to set his to 17 in third gear in the old days.

[Shimy87]

Thanks Steve!

[Steve Wood]

thinking about it, the alky is out on my GN and I think 14 is about it altho it has more compression than factory...it also has a 210 deg cam which should help...but 14 to maybe 15 is all it will do on 91

[Shimy87]

I was thinking also,
car has a TA 49 turbo and a 3 in DP. Im guessing the chip was for a stock set up so I probably have to add alot of fuel also?

[Steve Wood]

Could be.  Look at your o2's at wot toward the higher end of the rpm range if possible.  If they are around 780, the fuel is good.

i'm not sure the Octane rating of today is comparable to the octane of yesterday so it may be difficult to make comparisons as to what it should do now.  I recall that when 91 came out in Ca years ago.  Everyone was turning the boost down or buying alky kits.

[Shimy87]

Well, no suprise, this old girl is determined to be dificult. lowered timing in first/second to 17 and also in 3/4. added 10% WOT all gears fuel, turned up FP to 45 hose off for good measure. Still knocks, cant even get to WOT long enough to have SM retain info. SM knock got up to 4.6 when I lifted. I'm thinking I should just get a chip burned for this cars specific's? I tried to roll into boost in drive from about 40 mph also and cant even get to WOT before I need to lift because of knock.

another weird thing, after one pull, slowing down from 90 mph'ish, foot off gas, O2's read 0 for the longest time, then blipped the gas and they came back???

[nocooler]

Are you sure it's real knock? Bad tank of gas?

[Shimy87]

gas is new, its real, I could actually hear it

[nocooler]

I'd reach out to Eric about the chip.
Can you add some octane? Xylene, Toluene, or something like boostane, racegas concentrate, torco, vp octane boosters to see if it goes away?