Engine/Transmission (1994 - 1998) p-pump tuning

[Cosmo]

Ok so I'm trying to dial in my truck and I'm learning as I'm going. I've read the write-ups online that show grinding the washers on the diaphragm, grinding the foot, cranking the smoke screw, cranking the star wheel, moving the plate and housing forward...



But none of the write ups are really clear on what each does and they don't really say what to do if you want to (blank).





Here's my current setup:

4k gov springs (but stock trans gov)

#100 fuel plate

TST AFC springs - medium installed right now

ddp 50hp injectors

60lb valve springs

hx35 turbo, stock boost elbow (one that came with the fuel plate is in the toolbox now)



I've got the housing and plate full forward, the star wheel backed out almost all the way with the medium TST spring, and the smoke screw in about a turn.



Let me back up a second - I had the light TST spring in, with the star wheel full forward, and the smoke screw turned in about 1/2 way, and the fuel plate supplied boost elbow, but I've been averaging about 15 mpg and WOT merging on the freeway I was hitting 50psi with EGTs rapidly closing in on 1600 degrees.



So I decided to start tinkering, and that's where I am now. Star wheel backed out, smoke screw out, swapped to the medium spring, and factory boost elbow back in, but I'm really not happy with it. I'm still hitting 45+ psi, EGTs don't seem to be much lower at WOT, and now I can't pull moderate hills in overdrive at 50 mph.





I want to increase my low-boost fueling, but not to the point where I'm blowing smoke all the time. I think I also want to reduce my full boost fueling to lower EGTs.





So for the low-boost fueling, what I'm understanding is that I'm going to want to loosen the star wheel (run it forward). Should I use the OE spring, or would the light or medium spring allow for a better compromise between fuel economy and power? Keeping the smoke screw backed out will improve economy, but it'll create a bit of lag, since the increase in fueling will have to wait for boost to come on, correct?



As far as reducing boost and egts, I'm guessing I need to move the housing and/or plate toward the firewall, right? I never shaved the foot on the AFC because I didn't figure I needed to gain the extra travel.







I really don't like tinkering, but I need to get this thing squared away. It is my daily driver, and every now and then I do tow with it. Today I towed a 79 Firebird on a dolly, in two months I may be towing a flatbed with a race car on it, so keeping EGTs under control is imperative.



Throwing a bigger turbo (or twins) at it isn't in the cards right now as I've got other stuff much higher on my priority list.

 

[SRay]

Cosmo: I think the higher egt's is due to the higher rpms of the 4k gov springs. Not sure what truck you have, how many miles, but seems to be similar to mine in setup other than I have factory gov springs. I get high egt's too but can move the truck quite a bit with 1,300 pyro. Everything in my pump is moved for as much fuel as possible which allowed 1,000 ft/lbs torque at just 1,450 rpms with just 283 hp.

The factory cam I don't think is efficient at that rpms and neither is the hx35. 50 psi is asking for trouble.

If you want smoke control, you can fine tune a little more or just control your foot. I control my throttle to limit smoke and can black out the road if I wanted to. 95% of the time I control the smoke while driving or towing. I tow 25% of the time.

I can tow a combined weight of 24,000 lbs up a steep hill in 4th (nv4500) with max boost of 43 psi, 1,500 pyro and foot to the floor for the fun of it. This is at 80 kph, 1,750 rpms.

Turbo is over spinning quite a bit and beyond its efficiency range at 50 psi boost. There is no other option but to get either a larger turbine housing, hx40, better cam, or keep your foot out of the throttle.

I'm sure others have other ideas too as I'm looking for lower egt's while using factory turbo for sled pulling as per the rules.

SRay

 

[Bob4x4]

Lol a 100 plate and towing ,,,,,,,,

 

[mfurrh55]

Lol a 100 plate and towing ,,,,,,,,

He's looking for advice ,not ridicule,,,,,,,

 

[Bob4x4]

He's looking for advice ,not ridicule,,,,,,,

We have had discussions before on his parts choices-he didn't take advice then,I doubt he will now

 

[mfurrh55]

We have had discussions before on his parts choices-he didn't take advice then,I doubt he will now

Got it, Monte

 

[cerberusiam]

Lol a 100 plate and towing ,,,,,,,,

Pretty much. An HX35 spinning to 45-50 psi with those EGT's is a pretty good indication. Too much fuel, not enough turbo, not enough control.

Great play toy, not so good for dual use. Either add more parts or take some off, there are not a lot of choices.

 

[Cosmo]

The 100 plate was supposed to be a #5 plate. I ordered the #5 plate and upon inspection it wasn't a 5, but a 100. I didn't have time to ship it back and wait for the replacement to show up.

And I'll have you know it towed just fine pulling a ~15k pound trailer from Florida to WA, up and over several mountain passes. My EGT probe was aft of the turbo and I was able to keep EGTs below 900 most of the way, with a couple of short spikes up to 1000. I understand that pre-turbo temps were a fair bit higher, but still in the safe range.

After I got here, I moved the fuel plate and AFC housing forward. I was still only hitting low 40's. When I put the 50hp injectors in it really started spooling too much.

I KNOW I'm over-spinning the turbo. I want to know how to fix it, aside from putting a block under the throttle pedal. I can certainly control my foot, however I'd rather not have to rely on that method as other people occasionally do drive this truck.

And Bob, being a dick isn't required. You recommended that I skip the AFC springs and get a bigger turbo. Mighty white of you. You also recommended that I not get a #5 plate (which apparently I didn't). I didn't necessarily listen, but you weren't necessarily right. My smoke output wasn't obnoxious, my EGTs weren't too high, and it towed just fine.

So if you have advice on dialing in the fuel, I'm all ears, but otherwise gtfo. I've got what I've got, and I'm not dropping $1000-1500 on a new turbo at this time. I know I need more air. I have a feeling I know what I need to do to make this work, but I'm asking for information on tuning what I've got from people who know. If you don't know, then skip pressing the reply button with your condescending attitude.

 

[cerberusiam]

My EGT probe was aft of the turbo and I was able to keep EGTs below 900 most of the way, with a couple of short spikes up to 1000. I understand that pre-turbo temps were a fair bit higher, but still in the safe range.

What makes you think those post turbo temps were anywhere near fine? Likely you were already pushing 1500 degrees in the exhaust manifold and THEN you added injectors to the mix.

The 40 psi on an HX35 should have told you it was already over fueled for the air it could generate. That is so far out the map it just compressing hot on hot and lacking enough oxygen to make a difference.

Add more air or start taking fuel out of it, there are not a lot of choices to the physics of it.

 

[Cosmo]

F. F. S.


Let's try this again.

If all you're going to say is "add more air or remove fuel" then please just hit the back button and get out of here. You're not adding anything to the conversation.

What I'm asking, in this thread, is for people who KNOW what they're talking about to explain what the impact is for the adjustment of the fuel plate, afc housing, smoke screw, and star wheel. I *think* I have it figured out, but I'm asking for those who really know to provide their input.


The 40 psi I attributed to the boost elbow that came with the fuel plate, since that's what "they" say it's for - increasing the amount of boost.
I was under the impression that too much fuel created excessive smoke - mine's running clean now.

 

[NIsaacs]

And I'll have you know it towed just fine pulling a ~15k pound trailer from Florida to WA, up and over several mountain passes. My EGT probe was aft of the turbo and I was able to keep EGTs below 900 most of the way, with a couple of short spikes up to 1000.



I KNOW I'm over-spinning the turbo. I want to know how to fix it,

You can tow all day long at those temps. As far as the high boost numbers, it sounds like your waste gate is not working, maybe a hole in the diaphragm or sized up? I think a #16 turbine housing would help and is a cheap mod.



Nick

 

[cerberusiam]

I was under the impression that too much fuel created excessive smoke - mine's running clean now.

Excessive partially combusted fuel makes smoke, not neccessarily too much fuel. The problem is air quality at lower rpms and boost, ie towing range. The addition of better air at 20 psi will cool the combustion temps. You don't get that until you have better air induction, ie turbo. Or, you take fuel out of the equation.

You can tow all day long at those temps.

Not if those temps translate into high cylinder temps and pressures. Temps read post turbo are not indicative of cylinder temps on a mondified engine. The only time they are apllicable is on a bone stock engine.

 

[Bob4x4]

You can tow all day long at those temps. As far as the high boost numbers, it sounds like your waste gate is not working, maybe a hole in the diaphragm or sized up? I think a #16 turbine housing would help and is a cheap mod.

Nick

The 300 degree difference Internet myth. My 12 valve can see as much as 600 degree difference between pre and post turbo while towing

 

[NIsaacs]

The 300 degree difference Internet myth. My 12 valve can see as much as 600 degree difference between pre and post turbo while towing

The 300 degree drop past the turbo has been the rule of thumb for engine and pyro manufactures since way before the internet and TDR, it's no myth. If pre were so critical, why would you only moniter half the engine? What happens if the other half develops a slobber puss injector? Pyro's are not engine specific, they are universal. A factory 100 hp engine exhaust temps will mirror a factory 600 hp engine.

I will retract my previous statement..... MY engines will sustain 900-1000 degrees all day long.

You might see a 600 degree spike difference in temps when you stomp the throttle but a spike won't hurt anything or sled pullers and drag racers would fry an engine at every pass. The post pyro will react fast enough to prevent engine damage so they work for me.

Nick

 

[AH64ID]

The 300 degree drop past the turbo has been the rule of thumb for engine and pyro manufactures since way before the internet and TDR, it's no myth. If pre were so critical, why would you only moniter half the engine? What happens if the other half develops a slobber puss injector? Pyro's are not engine specific, they are universal. A factory 100 hp engine exhaust temps will mirror a factory 600 hp engine.

I will retract my previous statement..... MY engines will sustain 900-1000 degrees all day long.

You might see a 600 degree spike difference in temps when you stomp the throttle but a spike won't hurt anything or sled pullers and drag racers would fry an engine at every pass. The post pyro will react fast enough to prevent engine damage so they work for me.

Nick

It's still a myth, and why it's recommenced to monitor pre-turbo temps. The pyro's main goal is not to monitor for 1 bad injector, but the current state of the motor. A quick search of QSB data (since it's easily available and ISB is not) shows a difference of 164°-376°. With multiple motors being closer to 400° than 300°. Not to mention those are OEM motors with matched parts, as you mismatch performance parts that number will grow. Of all the ratings I looked at only was was close enough to 300° to call it 300°, and they were all slightly different. . sure makes it hard to be an industry standard.

Pyro's may not be engine specific, but safe EGT's absolutely are especially on more modern emissions laden vehicles. If you drove a bone stock '96 at the same temps a bone stock '06 ran you would melt the '96, and if you drove the '06 like the '96 you wouldn't get anywhere. EGT and cylinder temp are not always parallel, and things like timing/injectors/fueling will effect the difference.

Even on a 12V you cannot sustain the same EGT's at OEM timing as you can at advanced timing.

Temperature differences between pre and post turbo are a function of airflow over the turbine, turbine speed, drive pressure, etc. As you get a turbo out of it's map, as the OP is clearly doing, it's very easy for the temperature split to increase.

 

[Bob4x4]

The 300 degree drop past the turbo has been the rule of thumb for engine and pyro manufactures since way before the internet and TDR, it's no myth. If pre were so critical, why would you only moniter half the engine? What happens if the other half develops a slobber puss injector? Pyro's are not engine specific, they are universal. A factory 100 hp engine exhaust temps will mirror a factory 600 hp engine.

I will retract my previous statement..... MY engines will sustain 900-1000 degrees all day long.

You might see a 600 degree spike difference in temps when you stomp the throttle but a spike won't hurt anything or sled pullers and drag racers would fry an engine at every pass. The post pyro will react fast enough to prevent engine damage so they work for me.

Nick

Nick,my truck has pulled sleds and drag raced and it still tows

 

[cerberusiam]

The 300 degree drop past the turbo has been the rule of thumb for engine and pyro manufactures since way before the internet and TDR, it's no myth.

Always has been and always will be a myth when applied to a modified engine. The only application, and very narrowly, is a bone stock engine with extensive testing to determine what the max post turbo temp is compared to pre turbo and cylider temp. To the best of my knoiwledge that number has never been associated with or attributed to a B series engine, always been C or larger.

 

[AH64ID]

I looked at 3 QSC's today as well, and there were 2 of them at 350° difference and one at 330°. I looked at a few QSM's (11L) and they were much closer to 300, but there was still a variance based on hp rating.

 

[NIsaacs]

Nick,my truck has pulled sleds and drag raced and it still tows

Exactly, I have no doubt it has and does. What are the temps at the finish line, pre and post. If we use 1300 pre and 1000 post for a maximum sustained temp, how could one go wrong? There is a built in safety factor at both of those temps. If one insists pre is better, why is only half of the engine monitered? What is going on with the other half? With post you get an average temp of all 6 cylinders and if one injector goes bad you will see it. A 1000 degrees post is a 1000 degrees, be it stock or modified. I have used that figure as a maximum forever, what the pre temps were during all those years, I have no idea. When turbos and exhaust manifolds were single inlet/outlet, pre made perfect sense but with the split housings you can only get half a reading. I think that too much emphasis is placed on pre, that the sky will fall if you don't, that post burns up engines. If post is wrong, why does Isspro build them? I understand if the post pyro were mounted downstream too far you would get a false reading. All three of mine are mounted in the exhaust brake, all are modifed and all are made to run hard up to 1000 degrees.



Question: What was the industry standard temps, pre and post, before oil cooled pistons? What about intercoolers & aftercoolers, did that have any affect on max temps? I keep reading if you modify, all bets are off, why?? Does one modify his truck and then down grade his exhaust temps? What would be the gain in that.



Nick



Nick

 

[NIsaacs]

It's still a myth, and why it's recommenced to monitor pre-turbo temps.

The myth is, if you don't run pre turbo you will melt your engine. That is not the case. There are probably way more engines running without than with. You are picking little black specks out of pepper! 300 degrees is close enough for me, if I had to worry about 50 or 100 degrees I can't build trucks. It's not like 1301 degrees pre or 1001 degrees post will cause failure, there is a built in safety factor with those temps. If the temp is hot pre, I guarantee you that temp will work it's way post soon enough to prevent any engine damage.



Nick