HP and timing

[oc192]

I have been trying to resolve a knock issue for the last few months. I have replaced a bunch of parts and have the knock pretty much under control. I was getting some green knock around 12 lbs before I took my car to the repair shop. While at the repair shop, I had the drive shaft rebalanced and a tranny mount replaced (maybe some false knock with a bad mount?). The mechanic put 5 gallons of 100 octane fuel in my car and pulled the timing almost 3*. The knock is completely gone and I can get up to about 14-15 lbs. The car runs really smooth now and pulls nicely.

I have a 91 octane TT chip but I don't remember what the default timing was set for. Anyhow, on a mostly stock car, how much horsepower am I losing with 3* taken out? Should I try to adding 1-2* back in and maybe some fuel?

Thanks,
Don

 

[Boost231]

well you now know that the knock is real. i would make sure all the good gas is out, fill it up with 91 and see if it knocks. if it does we will figure that out. if it doesn't try adding 1 deg at a time back till you get knock then back it down a deg. that what i would do

let do this before we start worring about power.

 

[BEATAV8]

The other main ingredient is fueling. If the car is running lean it will make it knock. You can increase wide open throttle fueling to clean it up.

 

[theCATman]

I know that a TT 93 octane street chip default timing is 20-18.

91 octane is probably the same, but maybe 19-17?

 

[oc192]

well you now know that the knock is real. i would make sure all the good gas is out, fill it up with 91 and see if it knocks. if it does we will figure that out. if it doesn't try adding 1 deg at a time back till you get knock then back it down a deg. that what i would do

let do this before we start worring about power.

Thanks Brent for the info, that is the direction I am heading in. I am sort of addicted to the 100 now, runs so smooth :biggrin:. Just curious on the HP though, you think I am down 20-30 HP by removing 3*?

 

[Razor]

Thanks Brent for the info, that is the direction I am heading in. I am sort of addicted to the 100 now, runs so smooth :biggrin:. Just curious on the HP though, you think I am down 20-30 HP by removing 3*?

you need to make sure its not leaning out. A scanmaster will show your O2 levels at wot. They need to be at 770-800. If they are coming down 730-720.. it will knock as awell.

1st mod is a scantool. The knock gauge is useless once you start trying to figure out things.

 

[Boost231]

+1 i agree 100%. you need a scan tool. however if your happy where its at, see what happens with the timing low and just 91. if your wanting more out of the car or just trying to max the current tune we need a scan tool. As far as fuel pressure droping off, i would hope that with your walbro and hotwire its fine but there was a issue with the bad pumps awhile back.

 

[oc192]

I do have a scanmaster, I will do some pulls and see what the 02s are. The fuel pump is about 2 months old and came in a kit from racetronix. I have Casper's fuel rail test port that I ran a temp fuel gauge from and at the time I set the fuel pressure to 42#s line off. Maybe the fuel pressure gauge is off?

 

[Boost231]

just do a pull and see what the 02's are. Also you can verify a 1/1 raise with boost if you tape the fuel gauge to the window. If it is only 2 months old im alomost 100% sure its fine.

lets see what the 02's are. roll into 3rd and see what they are at when you let off. your in mesa and let me tell you. az fuel is ****. my car is in arizona, and it hates arizona fuel

 

[oc192]

Did a few pulls and didn't see anything above 730. It seems to jump around a lot. While just cruising around I happened to look over at it and saw 770. So does 730 mean I have too much air for the fuel being supplied and I need to add some through the chip?

 

[six is enough]

Yes you need to add some fuel and get it up to around 780. These numbers will move around just cruising. Your 730 at wide open throttle is lean.

 

[oc192]

ok, so pulling 3* timing prevented the car from knocking even though it is running too lean still? So the action plan would be to add fuel through the chip to get my 02 numbers up to 780 ish and then add timing back in?

 

[Boost231]

i would make sure what your line off fuel pressure is at. then i would check to make sure your getting a 1 to 1 rise with fuel pressure. if those 2 check out add fuel with the chip