12v Tuning advice

mtm94ramnasty

mtm94ramnasty

New member
I am looking for some advice on which direction to go with getting my current setup dialed in. To start, the truck is 100% a toy and my end goal is simply to maximize the current setup. First i will give a little back story on where the setup was. This dyno was 2 days after installing my current compounds from an s369sxe. Before the compounds i had not dynoed the truck, but its a full weight single cab 4x4 ran 11.51 @ 117mph with a s369sxe.

Truck recently dynoed 707.98 hp 1173.6 tq uncorrected on a dynojet 224x fuel only changing from the 69 to the compounds. pump setup was untouched from the s369. I felt those numbers were a bit low for my setup and assume it needs to be dialed in.

Fass 240 @ 65 psi - pressure is pretty steady at wot
Colmbus diesel 12mm pump ( started life as 180 )
built back in 2008-9 benched 600cc's with open holders/full cuts (what was in the pump for the dyno )
afc had a looser spring brining in full fuel around 30 psi from my previous setup.
afc modified for full rack travel.
pump timed at 30*
5x.018 145* vco, stock body no modifications
thin injector washers
stock fuel lines from pump to injectors
s366/s480 compounds (66/74/14 - s480/96/1.32 )
with that setup i was running 95 psi over all egts around 2000* smokes like a freight train even on top end at full boost. Gate on the 66 was set to full open at 45 psi. ( un touched from when i got the kit )
.010 over head gasket
arp head studs
stock cam
cylinder head is un touched other then o-ringed and valve springs.
still on stock intercooler

Since i had the truck on the dyno the following is what i have changed.
Checked valves and adjusted them to .006 / .015
Changed out the afc spring, full rack travel is now at 45 psi
swapped out the open holders for stockers
swapped out delivery valves from full cuts to comp cuts
verified timing did not slip and confirmed 30*
verified no exhaust leaks
verified no boost leaks
bumped up fuel pressure to 80 psi.
loosened up the gate on the s366, starts opening around 18 psi - full open by 40 psi. Anything lower seems to loose mid range power.
I have to hook up my drive pressure gauge and install a boost gauge between stages to really dial in the compounds. Will report back with those numbers when i get them.
On the street now egts are 1850* boost around 93 psi. Smoke is heavy, cleans up to a heavy haze by full boost. I feel like i am making progress, but its small. Im now starting to have issues with traction in 3rd gear where before wasnt an issue. With the loss of traction I am assuming I am headed in the right direction.
Is there any suggestions on anything that needs to be changed? The current setup seems to still be over fueled, but I would like to crack at least 800whp and dip into the 10s if possible.
 
Pull the plate after you get your drive pressure gauge. Push it a little harder up top. It sounds like you could go a bit stiffer on the afc spring to help light everything. You've covered most of your bases it sounds like though. Maybe a 7mm 100cc delivery valve would help some with the smoke down low, but wont hold back any on the top end..
 
95cummins5.9 said:
Pull the plate after you get your drive pressure gauge. Push it a little harder up top. It sounds like you could go a bit stiffer on the afc spring to help light everything. You've covered most of your bases it sounds like though. Maybe a 7mm 100cc delivery valve would help some with the smoke down low, but wont hold back any on the top end..
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I actually have a set of 7mm dv valves I was debating on throwing in, but was worried about loosing top end fuel with them. I’ll have to give them a shot and see how they work. I also should have mentioned that I’m not running a plate and use afc live to dial out fuel for when I’m driving on the street. I have it setup with the “full power” switch that bypasses the afc live and 100% uses the afc for fueling which is what I’m using on the dyno / track. Trying to use it for max power doesn’t seem to work well for me possibly because my afc spring is too soft. It’s kind of like an on off switch. Where would you reccomend full fuel to come in? Maybe around 60 psi ? Waiting on some dry weather to get some readings from the compounds.
 
It's not really about what psi it comes in at, it's more about having a strong enough spring to hold the afc foot back while its spooling to eliminate smoke and aid in lighting everything up. Have you tried without the afc live at all?
 
Yes, the “full power” switch bypasses the afc live. So I have the switch in the “on” position bypassing the afc live when I am looking for full power ( racing, dyno, test / tune) I only use the afc live for when I’m driving on the street. Even when the afc live is bypassed accelerating the smoke is very very controllable under part throttle.
If I am sitting at a dead stop, loading the truck up for a 4x4 launch, there is barely any smoke and the truck comes up on boost with no issue at all for a launch. Once I let off the brake / launch, it will smoke heavy and clean up after a second to a heavy haze.
The truck has a full manual valve body so if am driving and select 3rd and roll into it around 1900rpm it will smoke a bit, as rpm increases to about 2100 and the boost starts coming on hard, the fuel comes on heavy / thick, once at peak boost the smoke clears to a heavy haze. So with what your saying is to keep toying with the afc spring until the fuel comes in with the boost more evenly so as the boost rolls on the fueling remains say at a constant haze? This way I’m not overfueling hurting the spool up?
 
mtm94ramnasty said:
Yes, the “full power” switch bypasses the afc live. So I have the switch in the “on” position bypassing the afc live when I am looking for full power ( racing, dyno, test / tune) I only use the afc live for when I’m driving on the street. Even when the afc live is bypassed accelerating the smoke is very very controllable under part throttle.
If I am sitting at a dead stop, loading the truck up for a 4x4 launch, there is barely any smoke and the truck comes up on boost with no issue at all for a launch. Once I let off the brake / launch, it will smoke heavy and clean up after a second to a heavy haze.
The truck has a full manual valve body so if am driving and select 3rd and roll into it around 1900rpm it will smoke a bit, as rpm increases to about 2100 and the boost starts coming on hard, the fuel comes on heavy / thick, once at peak boost the smoke clears to a heavy haze. So with what your saying is to keep toying with the afc spring until the fuel comes in with the boost more evenly so as the boost rolls on the fueling remains say at a constant haze? This way I’m not overfueling hurting the spool up?
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Yep, sounds like you're close, tighten the spring a few more clicks. Some springs will bind up and not allow full travel also, so you may have to accept a happy medium with your current spring.
 
Did the 369 feel faster than your compound setup around the time you dyno’d it ? I have a single that flows about the same amount of air , 5x18s, 7mm, 180 pump at 20*. I’m hoping to get into the 11s this year with more timing,tuning, fuel pressure.
 
What is your axle ratio ? Do you remember what Rpm’s your truck was at with the 369 ? Curious about your combo with the single. Thanks
 
Curious as to why you chose those 2 chargers? The old 74 turbine is a turd down low. I was never happy with it on mine. Also the cast 80mm wheel is a turd especially in a race cover.

That being said I’d put the smaller DVs in too help low end spool. I’ve taken the afc spring out and heated it up and stretched it a little also to slow that foot travel down. I’d also throw away that afc live and just tune off the spring.
 
SCHMITTY said:
What is your axle ratio ? Do you remember what Rpm’s your truck was at with the 369 ? Curious about your combo with the single. Thanks
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I have 3.54s, I don’t remember what rpm I was crossing the line at. I run 265/70r16s prob could do the math and figure it out. Powerband feels very different with the twins vs the s369sxe. Certainly feels a bit stronger overall
and has a bit more attitude on the street when on the skinny pedal w the twins. I finished this build last summer, took the 69 off after 3 weeks because it was heavily over fueled and with a .90 ungated housing boost was around 70-72, drive pressue was getting up there. I knew I was asking for trouble. Only made 2 passes with it and sold it. It went on another 12v, 180 pump never off the truck, 5k gsk, afc modded for full rack, 191s, sdx 5x.018 sac, same trans I have and gear combo went 11.8s and ran much cleaner then the setup I had.
 
TheSilverBullet said:
Curious as to why you chose those 2 chargers? The old 74 turbine is a turd down low. I was never happy with it on mine. Also the cast 80mm wheel is a turd especially in a race cover.

That being said I’d put the smaller DVs in too help low end spool. I’ve taken the afc spring out and heated it up and stretched it a little also to slow that foot travel down. I’d also throw away that afc live and just tune off the spring.
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To be completely honest, because I got a smoking deal on a brand new unused set of industrials “race” compounds. I figured worst case I could list the 66 up for trade if I was that unhappy with it and replace it with something a little more appropriate. For now though, before I change any of the chargers I would like to see what I can get out of them and then possibility step up on the atmospheric charger and add more fuel with something bigger.

I am definitely going to swap in the 7mm’s I have and see how it runs. I’ll have to try stretching the current afc spring. Basically I have given up on the afc live and keep it bypassed when looking for all out performance.
 
What spring is in the AFC currently? I did a lot of screwing around with AFC springs and ended up having great results with a cut down common rail valve spring, with a compound setup you should be ok with something stiffer than stock.

Wouldn't hurt to swap the comp cuts for a 7mm but it shouldn't be a big difference, you'll lose a little fuel with them.

The 66 should be fine in that setup but I agree with what was said earlier about the cast 80 being a turd. If you do anything with the chargers I'd bump up that 80 first.
 
zachu812 said:
What spring is in the AFC currently? I did a lot of screwing around with AFC springs and ended up having great results with a cut down common rail valve spring, with a compound setup you should be ok with something stiffer than stock.

Wouldn't hurt to swap the comp cuts for a 7mm but it shouldn't be a big difference, you'll lose a little fuel with them.

The 66 should be fine in that setup but I agree with what was said earlier about the cast 80 being a turd. If you do anything with the chargers I'd bump up that 80 first.
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I am currently running power drivens stiffest spring they offer for the afc live. They rate it for 45-65+ psi. Bench tested with no preload it hits full travel at 45psi. I don’t want to make too many changes at once and get too off track. For now my plan is to play with the afc a little more and try to dial out the low/mid range fueling. If I can’t find a happy medium I will swap in the 7mm delivery valves and continue with the afc tuning until I nail the fueling curve.
During that time I will hook up the boost gauge between stages and the drive pressure to see what’s going on with the compounds to verify the gate on the 66 is set correctly. If all of the above gets sorted out, egts remain as hot as they are, and I hit the dyno / track and I don’t get the results I want then I will look into having the 80 modified or replaced.
 
I had ran 60 psi full travel on a 62/74 over a 480 to get it to spool decent and keep the smoke down. I stretched out a factory 215 spring
 
Just asking, but why does everyone say to get rid of afc live? I think on a street truck or tow pig it works great because you can really set it to a cool, smoke free tune and then full fuel with just flipping the switch if you want
 
mtm94ramnasty said:
I have 3.54s, I don’t remember what rpm I was crossing the line at. I run 265/70r16s prob could do the math and figure it out. Powerband feels very different with the twins vs the s369sxe. Certainly feels a bit stronger overall
and has a bit more attitude on the street when on the skinny pedal w the twins. I finished this build last summer, took the 69 off after 3 weeks because it was heavily over fueled and with a .90 ungated housing boost was around 70-72, drive pressue was getting up there. I knew I was asking for trouble. Only made 2 passes with it and sold it. It went on another 12v, 180 pump never off the truck, 5k gsk, afc modded for full rack, 191s, sdx 5x.018 sac, same trans I have and gear combo went 11.8s and ran much cleaner then the setup I had.
Click to expand...


Thanks. 3.54s on mine and 4ks , 180 pump.. it needs more timing for sure . If it holds together with a small shot I’ll be happy
 
Did it smoke less on the street than the dyno? I have always had trouble getting my truck loaded up as much on a dyno. Usually runs out of rpm before it gets fully loaded. On the street/track what rpm do you shift at?
 
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