Spoolinup98

All,

Im tuning my twin turbo 4.8 and am starting to get jittery on adding more boost. Ive read danmahs opinion of 14*/14psi being pretty successful but im unsure if he ran meth with that. Ive also read that less timing and more boost is potentially safer than high timing low boost. I want to drive this car somewhat reliably for alittle while before i turn it up. I plan on just reading the plugs after runs but its been raining its *** off and i haven't been able to.. Can i get pump gas timing/boost ratio opinions?
-gen 3 4.8 862 heads
-pac1218
-stock cam (higher compression with stock cam?)
- twin he351cw cummins turbos

Im currently at 14*/8psi. I know these turbos are made to be efficient around 21psi so im curious what direction you all would go in regards to 93 octane timing/boost.

P.S. Posting the build right now also if interested.

Thanks,

3 window

iTrader: (1)

Spoolinup98

Thanks for the info! is the meth needed for the 14/14 rule of thumb though? I will research how to build a meth setup.

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gametech

iTrader: (1)

I have ran your current timing versus boost numbers with an un intercooled whipple blower on a 4.8. Putting on a largish A/A intercooler allowed me to add about 6* of timing across the board. This was with east coast 93 octane gas. I once drove past San Antonio and had to lower the timing on the old setup 2 to 3 degrees on the west coast craptastic 91 octane gas. So I guess I am saying 11-12 degrees with no intercooler on crap gas at 8 lbs, vs almost 20 degrees on 93 with a good intercooler. Obviously there is a difference between a pd blower and turbos, but this should give you an idea.

epfatboy

iTrader: (3)

Apologies to the OP but I have recently wondered about the same thing. 14psi was my target as well on a SBE 4,8 with a single ON3 73/65 and a "stage 2" cam.

Is 14/14 with Meth and NO intercooler okay?
What about 14/14 with NO meth but with an Intercooler?
Last would be 14/14 with Meth and a Intercooler, would that be shorting the timing or boost or both?

ddnspider

iTrader: (26)

Read the plugs....that'll tell you what it wants. In the 12-14 psi range I've typically been in the 10-12* range.

Kfxguy

iTrader: (1)

On pump 93? thats where the confusion comes in. Some people specify, some dont and it makes a difference.

ddnspider

iTrader: (26)

I've only ever ran 92/93, no race gas no meth, no anything. Streetcar/DD stuff ova here.

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epfatboy

iTrader: (3)

I run nothing but 93 here but you never know when your gonna get a tankful of crap so best to tune conservative.
Agree with reading the plugs, they are never wrong. Just be prepared to make a pull and shut her down quickly so you get a clean read.

Now that I think about it a bit does running meth clean the marker on the plug strap?

Spider, So you don't run an IC or meth? Wouldn't you bump a few degrees if you did?

ddnspider

iTrader: (26)

I run an intercooler of course, just no additives like meth/alky/race gas etc. I don't like adding timing/boost with a meth kit because something in the kit can always fail. Use it for the cooling effect and this way if it craps out, you didn't add timing/boost to where it would knock.

Kfxguy

iTrader: (1)

Stonerracing

So with a carb; an intercooler and boostane professional in 91 octane gas may end up being a safer bet? Humm. Instead of depending on a water/meth injection kit. I was planning on 14# at 14 degrees of timing. 140000 miles on 5.3. Never regapped the rings.

2JZFC

iTrader: (26)

What 3 windows said, x10! There are too many variables for there to be a magic formula, ratio or opinion that everyone can follow for their setup. Invest $$$ for a 10x jewelers loupe (~$10+), a set of fresh plugs, a pair of gloves and some patience. Go to your favorite test spot or track, pull over and put the fresh plugs in. Make a couple of pulls, avoid a lot of idling and low-speed driving, and pull over and swap the plugs again. Take the fresh plugs home and inspect them:

- look at the heat mark on the strap to determine too much/little timing. Halfway between the end and the curve is safe.
- look at the heat on the threads to determine if plugs are too hot.
- use the loupe to look at the porcelain for signs of detonation. Black specks are a bad sign and silver specks are aluminum! You cannot see it with the naked eye and if you can hear detonation under boost, it's probably already too late.
- only way to tell rich/lean at WOT is to carefully cut the thread off one of the plugs and look at the ring at the base of the porcelain.

PITA, but the plugs are the only things to follow for tuning YOUR setup. Like others have said, run meth and run it straight to get the octane and let the plugs tell you how much more timing you can run. DO NOT trust pump gas or windshield washer fluid, etc, etc. With pump gas you want the additional octane from the meth, especially running a small displacement 4.8L with higher cylinder pressure.

Kfxguy

iTrader: (1)

I wouldnt. at 14psi on pump you better keep it around 12 degrees.

jimmyg

you guys using knock sensors at all? Mines set up to pull timing in relation to knock. It’s pretty touchy . I’ve had issues with false knock . Exhaust hitting frame etc...but it seems to work well. This is with a whipple 2.9 . Im Running 18* @13-14 lbs with 93 , meth /water. But the intake temps are relatively low. 25 over ambient usually.

TrendSetter

dont be such a sally, 14/14 is pump gas no meth or water. i had a decent intercooler so i ran 14 psi at 15-16* no problem and ran up to 20psi in my 4.8 and 5.3. i used to daily on 31psi in my evo, 93 pump, ive never bought methanol in my life.

47ford

3pedals gave you the best advice to follow..... but **** when I was blow through I didn’t pull timing till 6psi and ran in the 20s timing wise at 12 psi..... don’t do that lol