Inliners International Forums General Discussion Blown and Injected timing ?'s under boost

question is,
How much timing to use while under boost?
I have been consevative and running 21-22 @ around 12 lbs boost. This is also done with a good intercooler. Lately i have been taking it up to 24-26 in stages. It is really starting to make the motor perform. i do not want to get too aggresive with it and cause detonation.
just wanted to see what others have run for timing in boosted inline six applications. V8's are different as they have better combustion chambers. tom

The combustion chamber is fine on your inline.
Some V-8 combustion chambers are worse.
If you have a good quench area,,, you can run more timing.
24-26 total Is about your limit running 93 octane fuel.
I strongly recommend this http://www.jandssafeguard.com/
it's a little pricey,,,, but it will save your engine & well worth it!
A lot of times you cannot hear detonation until it's too late.
It will automatically retard the cylinder/s that is detonating,or all cylinders,depends on what mode you have it in.
Just need to buy a knock sensor also.
I highly recommend an water/alky injection system also.

MBHD

i have a terrible quench area. the piston is a stock forged trw. it has the .300 cup cut into it, that you could drink coffee out of. the piston also does not sit at the good .040 in the hole, but more like .070 down. all good for lowering compression on a stocker, but bad for quench.

That is pretty far down the hole..070
BTW.040 down the hole is not good for getting a good quench either.,esp. if you have a .038 head gasket thickness or there abouts..
MBHD

They make any thin gaskets or copper shim gaskets for the 6? We run GM .28 gaskets on our V8's to keep that quench down.

i guess if you guy's saw my pistons. you would see why quench is kind of a futil thing. they have a dish in them big enough to eat soup out of. what good would it be to bring the edge of the piston up to .040 from the head. then the compression would also be higher.

someone has to have experience with timing #'s under boost, even with a super charger.

revod, have you been getting anymore done with your car? our short summer is winding down. tom

Most of all Buick GN guys run under 26 degrees total timing,For pump gas & no methanol injection.

Read up on the Buick GN forums.

I have said it before,,, if you have a decent quench area you could run say 9 to 1 compression on pump gas,,,, now,,you can have 8.2 to 1 & have it detonate like crazy because you have no piston quench & or sharp edges on pistons or chambers.

That being said, you can get some sort of quench ,even if it is just on the edges around your piston, & yes it will help supress detonation.
Sure your compression will go up, but you can open up your cylinder head chamber.

I have a 250 Chevy w/307 flat top pistons w/four valve reliefs.
Small 194 head milled to 50 something cc's (can't remember right off), but w/that head & pistons I had 12 to 1 compression,220 cranking compression, ran on 91 octane,no detonation.
Pistons are .000-.003 postive deck height,decent quench.
Switched to big chamber head, sunk the valves a bit, unshroudeded & opened up the chambers to 80 something cc's (can't remember right off)

Had 8.5 to 1 compression & a Paxton super charger,still no detonation w/8-9 psi boost pressure & no intercooler on 91 octane.
Total timeing w/supercharger was about 30 degrees total.
So 12- to 1 to 8.5 - to 1 w/out changing pistons,just changing heads & opening up the chambers,not bad.

MBHD