96 12Valve stock boost performance.
 

Ok folks, I know there is loads of information on this forum and scattered around on the internet about second generation 12 valve, but most of it is related to tweaked/modified setups.

I am having trouble finding basic stock performance specs.

My truck is a basically stock '96 12 valve auto. My primary question is regarding boost. I am seeing a max of ~18psi boost under WOT @ ~2200RPM. At that number I am starting to smoke a little. Everything up about 70% throttle is pretty clean to about 15-18PSI, after that it just adds a more fuel without adding more boost providing very little more power and more smoke.

Is there something that is not adjusted right? Does this turbo have a waste gate? I have seen a lot of talk about boost elbows to add more boost, but it seem that all they allow is more fuel to create more boost which doesn't seem to be my issue.. Shouldn't the stock turbo be capable of more boost than this?

Also, down around 1500RPM, is there a way to get the turbo to spool more, all I get is ~10PSI...

Enlighten me :)

the stock wastegate is set to about 17-19psi. manifold pressure determines when the gate opens and how far it opens. its just a diaphram. a boost elbow has a very small orifice in it which retards the reference signal (pressure) to the diaphram of the wastegate, keeping it closed longer and thus making more drive pressure 9PSI) on the hot side and more PSI on the cold side of the turbo. it is placed anywhere in the reference line from the gate to manifol PSI. a boost elbow has absolutly nothing to do with fuel. i hit 52lbs of boost with my stock turbo before i decided it was time for an upgrade.

Hey guys im looking at buying a 1997 f-250 powerstroke diesel its an automatic with 180,000 miles it is 4x4 its a regular cab long bed. Its all stock except for a straight pipe. They are asking 4500 for it is that a good price or does it sound like a problem truck?

your in the dodge section friend

oh im sorry i just made this thing today and i aint to sure how to work it yet

lol :)

once you get a hang of this forum you will definately find it useful ;)

Ok, I temporarily capped off the boost feedback line that goes from the compressor housing to the waste gate controller. In theory, this should give me 100% of available boost.. The most boost I am seeing is about 20PSI. I am assuming this is because of lack of fueling with the stock setup.

The question I have, is that at about 2000RPM I can get about 19PSI of boost, if I bury the peddle I get some smoke, but almost no more power or boost. If I increased the fueling, how would that be any different? What I am really asking is why do I get smoke? Is that un-avoidable?

Thanks

I don't know, but my truck made 22psi bone stock. I got a few more psi out of it with the BHAF, and a few more with the straight pipe exhaust. Right now with a filter and exhaust I'm making 30psi at WOT, so I'd say something isn't working right for you.

^Did you change your fueling from stock at all? 3k/4k GSK, etc? What year?

with no mods i'd say your truck is acting normal, if you want better performance i suggest grinding your fuel plate and play with it a bit until you like the outcome.. #100 & half way forward should be ok for a all stock truck to make it go a little more than stock.. and for more boost down low you can alter the starwheel.. giving that your truck doesn't smoke in the low rpms...

Does your turbo have end play?

i gained 7psi of boost by putting an air filter system on my truck with a stock charger back in the day. stock systems are a giant let down. recently had to put the stock system back on the truck for a day or two while i fabbed a new system it made my truck near undrivable. absolutly horrid

hmm, air filter was my first mod after gauges... i saw 1-2 psi difference MAX... unloaded, maybe 5psi loaded...

I guess these trucks are just about as different as there are many...

I put the stock filter in after modifying it a bit and it dropped about 10 pounds of boost...

1998. And no, everything is in my sig.

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Which direction for more low end boost? I'm thinking about cranking my stock plate FF. Pulling a trailer on the highway is a real bummer as soon as it shifts into OD @ 60mph and my 2500rpm/30psi instantly becomes 1500rpm/10psi and it falls on it's face.

for more low end boost turn the top of the star wheel toward the engine, more fuel more smoke. turning the top of the star wheel away from the engine will give you less fuel and less smoke.

I don't care about smoke, just wondering how much sliding the plate forward is going to upset the balance of things regarding the other adjustments in the AFC, like the starwheel. While I doubt that the stock locations for everything are working together as well as they could, my concern is that adjusting the plate for more fuel and not knowing what to do with the starwheel in conjunction with the change will make things (power/mileage) get worse instead of better. For some reason all the hours I've spent reading up on tuning the AFC in here has left me with more questions than answers.

I suggest you move the AFC housing full forward, sliding your plate full forward will be good too but the pattern on the stock plate doesn't allow for much low rpm fueling...

just play with the spring until you find your desired setting, you can even fully loosen it and then tighten it from there... all it takes is an allen wrench and a flat screwdriver ;)

Well, today I screwed the starwheel FF to see what would happen. It seems to run smoother, and idles with a full 2psi more fuel pressure. It's definitely got a little more pep across the board. Too soon to tell what affect it may have had on my MPG, but I don't suspect it's gotten any worse because curiously, there isn't any more smoke than there was before. My guess is that with the plate still in the stock position, this little bit of extra fuel is all getting used. I assume that if I move the plate forward or put an aftermarket one in this will change, and I'll have to tighten the starwheel back up a bit to not waste all kinds of fuel out the tailpipe, but so far I'm pleased with the results of such a simple thing. I'll let it ride for a tank or so, then maybe move the housing forward. Then the plate? Dunno. Like they heard from the guy who jumped out the 10th story window as he passed floors: "so far so good, so far so good..."

For 100% tuning you will need to mod your AFC.. but you're off to a good start....

Don't spend money on a plate, just modify your own plate...

The pattern on the plate is shaped in the way that the foot will ride, it will start on the bottom and ride up as rpms increase, so if you leave a bit of material on the bottom of the plate, you will limit the pre-boost fuel...

I ground my plate to a #0, and had it set @ 75% full forward at first, then i slid my AFC housing full forward and completely released the spring, and then worked my way back until i could mash it without everything drowning in smoke...

You can feel that if you have your AFC spring completely loose with a fuel plate mod and AFC full forward.. that too much fuel will result in poor spool up, so make sure you tune it correctly..

I had mine set at a reasonably clean setup at first, here's a video of my old truck with my first mods after i fully tuned the AFC:


This was as you can see, reasonably clean... but would put ~360hp to the wheels...

Smoke is not always a good thing, although it can be cool to roll smoke if you go fast with it...

That does look like it's running amazingly clean. Plates are so cheap now that I'd just assume buy one, that way whatever I do is still reversible. It seems to have responded well to this step. Not substantial power mind you, but different enough that I no longer feel the need to turn off my OD around town to not feel like a complete turd. It's sort of like the TC feels tighter or something, like the stall is a couple hundred rpm lower. Regardless, I'll move the housing after I've run it this way for a few tanks. Do I need to worry about fuel gushing out while doing any of these AFC mods?

I suggest that you buy a kit for your transmission.. maybe even a converter too.

I'm not familiar enough with these 47RE/RH trannys, i'm all for the NV4500/5600...

Nah... I'm just going to run this one until catastrophic failure and put a built one in.
Grenading this tranny is the excuse I'm waiting for. Don't get me wrong, I don't beat my truck and I'm not trying to blow it up, but I don't give a crap if this tranny goes. I'm a stick guy too, but it sucks pushing snow.

I am most interested in fuel economy. I am assuming that smoke=unburnt fuel=bad fuel economy.
Is there anything we can do with these 12Valves to reduce the hazing/smoking? I assume timing may have something to do with this.. It seems I start smoking above 1800RPM, worse the higher the revs.
2200RPM=~19PSI, ~1100deg, and visible smoke.
This is with a stock fuel plate and system. Only modification is the boost line is capped.

Thoughts?

Unfortunately I already had my intake and exhaust when I got my gauges put in, so I'm not sure how big a difference they made in my EGTs, but that sounds off. Until I moved my fuel plate I never got my pyro over 1000°. With it slid all the way forward I can just now hit 1100°, and the difference in power was so dramatic that I can't believe you're getting that hot with the stock fuel setting. Could just be truck to truck differences though, or even gauge to gauge.

Regardless, from what I hear, bumping the injector timing makes a big difference in MPG. I picked up at least 2 MPG when I slid my fuel plate forward, and finally started driving normal again (couldn't keep my foot out of it for a little while, or the stupid grin off my face). I'm hoping to tab my KDP and bump the timing in the next week or so, can't wait to see how it does then. I still haven't moved my AFC housing or done any significant playing with the starwheel or smoke screw, but it's not really smoking unless I stand on it, and even then not enough to see in my mirror so I haven't worried about it.

take fuel away up top or put a bigger charger on it and take fuel away down low.

Normal EGT's are only max 1000deg, but with a prolonged pull up a hill @~1500RPM @~12PSI will see 1100deg.

I have been suspicious of a leaking injector, but I took a infrared thermometer to the exhaust ports and they all seem to be pretty consistent temperature-wise. The front cylinder seems to run ~50deg cooler, but that may be error in measurement because of less exhaust gas flow. Thoughts?
Externally the fuel system is very clean, no leaks, etc.
What are normal idle EGT's? I am seeing 350-400 depending on weather, if I put the trans in neutral and idle for awhile I can see 300deg.

Can a dirty/clogged fuel filter hurt MPGs? If so/how?

*Edit* 6 months ago I did a ~4000mile trip and averaged (hand calculated) 21.6MPG. Normal around-town-freeway mix was ~19.5-20mpg. Recently I have been seeing 17-18. I know it is winter fuel, but I live in SoCal, so the "cold" is not too extreme, rarely below 40degF when I am driving.

Those idle EGTs sound identical to mine. Before moving my plate, I noticed my performance go down as my fuel filter neared the end of it's time under the hood, and jump back with a fresh filter. While I haven't necessarily noticed the same thing with economy- at least not to the extent of 3 MPG- I can logic out that it could do the same thing. Starving these things for fuel certainly doesn't make the mileage go up, but fueling the hell out of them for some reason does. Reverse process would suggest that a restrictive fuel filter sure wouldn't help things.

Concurrently, I change my fuel filter every 5,000 miles, and I notice a difference. I've never talked to anyone else who does it that often, most people do it annually at the most. If mine is dirty enough after 5K for me to feel a difference changing it, how much more difference would 10K, 15K, 20K make? Probably enough to start affecting the MPG I'd think. Just postulating here, any guess from me about this stuff is barely educated at the most.

I'm going to guess you have a 215 engine while he has a 180. It would cause the difference in boost.

A '98 automatic? I'm not positive, but for some reason I thought I have the 180.

Ok you have the 180 then. Hmmmm. Prior to IP mods with only exhaust and air filter I could only hit 23 or so psi, but that was with stock wastegate settings.

Could be my mechanical Autometer boost gauge isn't accurate. I've been meaning to replace it with an ISSPRO to match the others when I'm a little more flush, then I'd see if there's a discrepancy. Doesn't look to be coming to the priority front anytime soon though.

Smoke will usually come at the cost of high EGTs, so it's not entirely good, i'd mess with your timing, set it to 16,5° (could be 19° if you don't really boost over 40psi) and then loosen the starwheel about 4 total rounds away from the firewall.. slide the AFC foward a bit aswell, you will feel a tremendous difference...