Timing questions on my twin turbo 318

[elsensei]

Hi everyone-

A couple years ago I posted that I intended to build up the stock 318 in my 68 Dodge charger to a intercooled fuel injected twin turbo.  Well, I finally got it all together, and it's running, and now I'm just working on tuning.

The specs: when I bought the car it had a rebuilt engine and it had about 4000 miles on it.  It now has about 9000 miles.  I left the bottom end stock, but replaced the cam, the timing set, etc. I am running Edelbrock RPM heads, solid lifters and roller rockers. I built and installed a megasquirt unit and I have full control over fuel and spark. I set the redline to 6000 RPMs. I am running a pair of Garrett GT turbochargers blowing into an eBay intercooler, and then into a 90 mm infinity q45 throttle body.  I also swapped out the stock transmission for a Keisler performance TKO600.  I am running 3.23 gears with a suregrip setup. Oh, right now I am running 9.5 pounds of boost, but I intend to turn it up to 12.5. My goal is 20 mpg on pump 91 and 600 RWHP.

The only specs for timing that I was able to find work in my 1968 charger shop manual.  According to that, timing is supposed to be set at 2.5° after top dead center.

Can any of you make a recommendation as to what the initial timing should be set at for this set up, what full advance should be, etc?

also, the mega squirt system offers a self tuning function that works really well.  All you have to do is set your target air fuel numbers and feed an o2  sensor signal back into the computer and it adjusts while you drive. any recommendations as to what cruising AFR should be? Right now i am at about 15.4 to 1 with no pinging, but under boost i'm running 12.6 at 3 lbs, 12.2 at 6 pounds and 11.8 at 9 lbs. Any advice there?

I know these are kind of off-the-wall questions,and not the usual setup, but I figured if anyone could offer some good advice, it would be someone here.

Thanks in advance (pardon the pun)

Sam

[elsensei]

forgot to mention....also running dual 3" exhausts.

here's an underhood pic.

[Rolling_Thunder]

cruising A/F ratio seems pretty decent...   no need to run any richer if you're not detonating...        A/F ratios overall seem pretty good ---   

The timing on most performance engines seem to be about 10* initial...      but - that is without boost...     ideally you can pull timing as boost is added - but overall your set up doesnt seem that bad off -  maybe play with the timing - bump it up some and see what happens -  its just some keys on your laptop...       

[elsensei]

yes, I can pull timing under boost or anywhere else. The megasquirt system is pretty amazing, esp. for the price.

I was planning on pulling 1 degree per lb.

What do you recommend for maximum advance when NOT under boost?

[Rolling_Thunder]

I would start around maybe 30* total under no boost....     see if you get ANY detonation - if you do then sub some timing out - if not see how she runs -

this is why tuning is the most time consuming part - every build is different ----   so no matter what you will be messing with the MS and just playing - seeing how your combo reacts....

Which MS are you running ?   I would assume a MSII ?

if you feel up for it please post more pics and info on your build -  I've thought about a SB TT build myself....   

[elsensei]

Yes MSII.

OK so i set initial to 11 btdc and what a difference! Fires right up, idles well, between 650 and 715 rpms, not sure what dodge was thinking with 2.5 atdc. Then again, this isn't a stock motor haha.

i have full advance set to 30 at 6K, pulling one degree per lb of boost so at 6K 9.5 lbs timing is 20.5 degrees. It's really nice to be able to specify EXACTLY what timing you want per rpm/pressure intersection, down to the tenth of a degree. I don't detect any pinging but then again it's kind of hard to hear because I have the wastegate dump tubes pointed straight to the ground between the frame and the torsion bars on both sides and when they open under boost it sounds like the end of the world.

I set the timing to ramp up fairly quickly (i think, meaning it seems quick to me but I'd welcome opinions) and then just had the computer interpolate from mid to max RPM.  In fact, I'll take a screenshot and post it in a second...be right back.

[elsensei]

here's the timing map. i made a couple changes already, now full timing is 34 degrees at 6K.

[Rolling_Thunder]

looks pretty good to me - glad that the 11btdc makes a big difference

[elsensei]

to keep you in the loop-

now that the timing is set more aggressively, not only does it idle smooth as glass and run with much more power, but the boost comes on so quickly that you literally cannot feel it. It's just always there.

The other thing that is amazing to me...two days ago while i was still messing with all the settings, while driving it, if it got into boost at all it would fall flat on it's face and then it got harder and harder to start until finally it refused to catch at all. I racked my brain and investigated all sorts of things, checked TDC for the third time, changed timing settings again and was finally reduced to pulling the spark plugs. Of course they were uniformly black and soaked with gasoline. The engine was literally drowning in fuel. I changed the plugs, checked my settings one final time and it started with the first crank. I immediately set the computer to autotune and it started pulling fuel like you wouldn't believe. I would say it easily reduced injected fuel across the board by about 40%! It still hesitated near boost, so I manually lowered those numbers by 25% just so it would boost without stalling and I set the computer to make fast adjustments and went for a cruise. Every time I got into positive pressure it would get smoother and smoother and more powerful.

I'll post dyno numbers when I get them.

[Rolling_Thunder]

Damn!    40% reduction on the injectors is HUGE.       Figure that will save you some fuel on your MPG scale         

When coming into boost it should be a fairly smooth transition - this is of course managed by fuel and timing - as you have well learned   

I have been dicking on a friends Lexus that we built a turbo system for...    running a conservative 9psi...       the MAF sensor mounting was causing some turbulance through the intake - making the fuel map compensate for erratic MAF sensor readings...      not cool....         

keep us updated on the progress -  most guys around here might not care due to their reliance on carbs but a few of us sure do...   I am working on some EFI projects myself - something about a Twin Turbo set up for a BB           

[elsensei]

yeah I'm kind of over the whole MAF thing. See if he'll consider going megasquirt w/MAP sensor.

[Rolling_Thunder]

Well he is trying to keep the car compliant with CA smog laws -  currently he is running a CARB legal turbo kit - but if you replace the ECU with the MSII you fail the visual test...        so...      He is actually running this set up with a factory ECU - no flashing or mods -  which is actually pretty cool that the Lexus ECU will adjust enough to control this...    he's aiming for 400hp with 9psi and methanol injection - he's planning on auto crossing it - against my Charger actually...     so I figure it will be a good run when I get my car up and running.

[elsensei]

sweet.

I'm most likely going to the dyno tomorrow. Dare I turn the boost up to 12.5?

[Rolling_Thunder]

I would - but again if there is ANY symptoms of detonation get out of it quick -  you'll need to adjust the timing once again as well as the fuel mapping...      but thats the place to do it     

[elsensei]

Ok Back from the dyno. Ended up running 11 psi, made minimal changes to boosted timing, richened it up a little bit up top to try to stay safer, and it actually made MORE power that way. That was a nice surprise. I'm scanning the dyno sheet now, but it made 509 HP and 473 lb/ft at the wheels, SAE corrected, at 6000 RPMs on pump 91. Zero detonation. I just let the megasquirt tune itself for fuel. I could probably advance the timing some more but didn't have time, plus that much power on a stock bottom end...how much more can it take?

[elsensei]

Here it is.

[Rolling_Thunder]

Nice numbers!    glad the higher boost worked out for you ---     i'm sure there's some more power kicking around in there with fine tuning -  but those numbers are more than respectable --       the 318 is a kick ass engine - it is a very stout bottom end -   

[elsensei]

regarding the 318 as a stout bottom end...

how stout is it, really? I have no idea about the composition of the crank or rods or pistons in this motor, because frankly, I figured if it blew up I'd just grab another one (they practically give them away at the junkyard), bolt all my aftermarket parts on it, install it, turn the boost down by 1 psi from whatever level exploded it and hit the road. So I figure it's comprised of whatever dodge was using back in the day, or rather, whatever engine rebuilders were using in a grandmotherly grocery-getter. (this car had 67K miles on it when I got it, and I found a receipt for a rebuilt engine from 63K miles). And it was owned by a little old lady, the original owner. I am not making this up.

Back on topic, I do know that the greatest stress on the motor is the connecting rods changing direction, and that is why I'd prefer to run more boost than wind the engine to higher RPMS. But having said that, does anyone know how fast you can safely spin one of these? Aside from the valvetrain, the rods and bearings must be the limiting factors unless I am missing something. How high can it go?

[Rolling_Thunder]

I know the 318s used a factory forged steel crank - so you're good there...           I have heard (somewhere) that the factory 318 rods are fairly strong - the weak links (if you can call them that) are the connecting rod bolts.

The block is like any other small block chrysler -  fairly stout but not impossible to damage...       


To honestly answer this question:  No idea...       i'm not sure how much HP you can pump out of your 318 without it grenading.   

I would bet it could spin to 6500rpm easily...     with the valvetrain and heads that will work that high....        I don't know about you but my stones aren't big enough to spin anything to 7000rpm (on purpose) --   I've spun a 426 hemi past that as well as a 440...      but wouldnt do it on purpose.   

[elsensei]

i might turn the redline down to 5000 but up the boost to 15 psi. that ought to be interesting.

[Rolling_Thunder]

well that would definitely increase the stress on the engine -  you'd be better off IMO to just try 12 -14psi with a 6000rpm redline   

[elsensei]

really? I was under the impression that higher RPM is more stressful than higher boost. to a point.

[Rolling_Thunder]

well the higher RPM does cause stress - the higher boost will cause even more - it causes more heat and greater cylinder pressure...    you'll possibly start running into cylinder head sealing problems --   

you could try both and see which works better for you   

[elsensei]

true. just FYI at night my intake air temps are holding steady at 68-70 degrees. I have a pretty burly intercooler and my own special intake that i submitted for patent. Plus, I'm running cometic head gaskets and switched to ARP studs.

I'll mess around with it and see what happens...

[Rolling_Thunder]

Ah - cometic with studs ---   turn up that boost until you get a little detonation at 6000rpm and then turn down 1 psi   haha