02sierraz71_5.3

iTrader: (2)

Working on a buddies whipple charged 8.1L this thing has been a pain. He has always had kr 1-4 when you jab the throttle and it almost always pulls 5kr at wot. It was dyno tuned with the whipple piggyback and set at 12.2:1 AFR and a conservative 14 degrees WOT with 6psi by someone else. He bought the truck with the whipple already on it.

-Piggy back was removed, 42lbers installed. Now it will only pull a max of 3psi. Able to line up trims better plenty of fuel WOT around 920-930mv little less kr but it is still pulling timing wot with plenty of fuel and only 11 degrees timing.

-Still using MAF, doesnt have map to read boost or wideband. IAT sensor in stock location.

Im missing something because now with only 3lbs boost and good fuel WOT it still hits KR with 11 degrees timing. I have never heard it actually ping either.

Spenser309

Sounds like false knock? check for a bad motor mount, transmission mount, exhaust pipes banging, loose accessory bolt, and bad pulley install?

for the low boost, may need a boost controller. the BOV prob has a 3lb spring in it and without the boost controller that is all you will get unless u can somehow reuse that part of the piggyback system. or get a 6# spring.

get a wideband o2. 920-930 means it aint at stoich and thats about it.

You should have a map sensor. its usually at the rear of the intake, but you can connect one to any vacum line. so it may be off hidden somewhere else, even inside of the computer.

42lbers last to about 600 hp. especially in FI apps.

This really doesnt sound tuning related, but instead mechanical.

02sierraz71_5.3

iTrader: (2)

looking over the logs/tune I noticed the as soon as he gets on it a little the map jumps from 53 to max as soon as it hits max it automatically pulls 5kr.

Also it looks like hes very close to maxing the MAF with it reading 11k at 4k rpms.

Spenser309

whats raw voltage of 11k?

Spenser309

your maxing out your map sensor then. This is because it should show over 100kpa in boost. it would be 120kpa at 3 psi. Make sure your not in speed density and put a wb02 on it if its not pipes or broken motor mounts its caused by going lean on the injectors. what is the injector pw, if its over 100 get new injectors.?

02sierraz71_5.3

iTrader: (2)

11k is the hz reading so he is very close to maxxing out the MAF. I know the MAP is maxed because its the stock 1bar map he needs at least a 2 bar and Ive been trying to get him to put one in, could this be the reason for the kr WOT?

With the 42's he is seeing a high around 80% duty cycle the fuel is there, trims relate that. Timing is around 12 degrees WOT. He is not in speed density I made sure of that since he doesnt have a map that can read boost.

Spenser309

sounds like mechanical stuff, the black box aint always the problem.

only other thing i can think of, is because of the huge bore the timing could be too high. Its really hard to guage what your timing needs to be. Try putting wot timing at 10 - 12 and then maybe alil lower. Iono, im just not convinced its the PCM.