Engine/Transmission (1994 - 1998) 1st tow with 370s

[ndurbin]

I got alil bored earlier and decieded I'd go drag my trailer around to see how the 370s did. I was really surpirsed at how much difference being in 3rd and OD going up hills was. In OD I really had to keep an eye on the guage whereas in 3rd I could hammer down. EGTs haven't been as bad as I thought with the stock turbo, but I think I'm going to need a GSK and DVs. 50-55 aint gunna cut it outta OD. My truck really seems to defuel at 2200 rpms.



Other then that she's running great Oo.



Nathan

 

[Rams-n-Hogs]

Nathan,



It really gets fun when you upgrade the turbo, tho.



Jim

 

[MatthewPark]

If your truck defuels at 2200 I'd bet money you aren't getting full throttle. My truck would defuel at about 2100 rpm when I got it, it wasn't even close to getting full throttle with the pedal mashed into the carpet. 5 minutes adjusting the rod on the side of the pump and it goes to 2600rpm. Be careful adjusting the rod, if it's too tight it can break (don't ask me how I know).



I have noticed a buddy of mine only pushes on the bottom of his smoke pedal (he's got short legs, and it would shift at 2000 rpm. As soon as he moved his foot to the top of the pedal, it starting actually making power and shifting at 2500rpm.



Just something to check, it makes a huge difference.

 

[JGheen]

I got alil bored earlier and decieded I'd go drag my trailer around to see how the 370s did. I was really surpirsed at how much difference being in 3rd and OD going up hills was. In OD I really had to keep an eye on the guage whereas in 3rd I could hammer down. EGTs haven't been as bad as I thought with the stock turbo, but I think I'm going to need a GSK and DVs. 50-55 aint gunna cut it outta OD. My truck really seems to defuel at 2200 rpms.

The reason your EGTs get so hot in OD is cuz your engine speed is much slower than in 3rd gear and the turbo is not spoolong fast enough to get the exhaust gasses out so they build up and get really hot. When you pin it in 3rd, the engine speed gets greater, faster and feeding the turbo the air it needs to get the gasses out and be much cooler.

Not sure why it would be defueling so soon, but Matthew has a good point and a place to start for checking full throttle fueling. But that doesn't mean you shouldn't get the 3K GSK. Oo. Go for that definately, but find your current issue at hand first.

I would also stay away from lugging in OD at anytime as it kills that gear in the transmission. Never use OD when towing either, especially lugging it while towing, that will really heat things up in the 'ol auto.



Joe

 

[ndurbin]

I would also stay away from lugging in OD at anytime as it kills that gear in the transmission. Never use OD when towing either, especially lugging it while towing, that will really heat things up in the 'ol auto.

I keep it wound up when towing in OD. If it starts to lug (which has happened once) I just downshift. Besides I'd be beating my head against the a-pillar if I had to run in 3rd all the time towing.

If your truck defuels at 2200 I'd bet money you aren't getting full throttle. My truck would defuel at about 2100 rpm when I got it, it wasn't even close to getting full throttle with the pedal mashed into the carpet. 5 minutes adjusting the rod on the side of the pump and it goes to 2600rpm. Be careful adjusting the rod, if it's too tight it can break (don't ask me how I know). I have noticed a buddy of mine only pushes on the bottom of his smoke pedal (he's got short legs, and it would shift at 2000 rpm. As soon as he moved his foot to the top of the pedal, it starting actually making power and shifting at 2500rpm.

I'll haveta look where I push on the pedal and I'll check the rod on the pump. But it just really seems to fall on it's face at about 2200. Might be time to run the valves and make some timing adjustments again too.



Thanks for all the input

Nathan

 

[MatthewPark]

I'm going to have to disagree with your EGT comment. The reason the EGT's are high is because the turbo can't spool up at low rpms (to create airflow to burn the fuel). Lots of fuel without air to burn it (boost) = high EGTs.



Exhaust gas doesn't back up and get hot, it's hot because you can't push enough exhaust through the turbo to make boost, and without boost, EGTs are going to go up. His EGTs are directly related to airflow through the engine in relation to fuel, not the exhaust backing up behind the turbo.



The amount of exhaust pressure when he is running boost is FAR greater than when he is lugging it out of boost. At the same time, I'd be willing to bet his EGT's are lower.



The cheapest way to get more air through your engine (to lower EGTs) is to downshift. His engine just can't produce enough exhaust at low RPMs to create boost, so his EGTs are high. When he downshifts, the engine can create enough exhaust to spool the turbo up, and now he can burn all his fuel. Wham, lower EGTs.

 

[JGheen]

I'm going to have to disagree with your EGT comment. The reason the EGT's are high is because the turbo can't spool up at low rpms (to create airflow to burn the fuel). Lots of fuel without air to burn it (boost) = high EGTs.



Exhaust gas doesn't back up and get hot, it's hot because you can't push enough exhaust through the turbo to make boost, and without boost, EGTs are going to go up. His EGTs are directly related to airflow through the engine in relation to fuel, not the exhaust backing up behind the turbo.



The amount of exhaust pressure when he is running boost is FAR greater than when he is lugging it out of boost. At the same time, I'd be willing to bet his EGT's are lower.



The cheapest way to get more air through your engine (to lower EGTs) is to downshift. His engine just can't produce enough exhaust at low RPMs to create boost, so his EGTs are high. When he downshifts, the engine can create enough exhaust to spool the turbo up, and now he can burn all his fuel. Wham, lower EGTs.

Read my post again. I said exactly what you said. Engine speed creates more exhaust, hence spooling the turbo up and creating boost to get the exhaust out. I never said the exhaust backs up, I said it builds up in higher gears cuz it is not moving as fast through and out the turbo, hence slower moving exhaust gases= hotter EGTs.

You still disagree?

 

[y-knot]

Not too sure how equal are two trucks are, I do not have the larger injectors as you, but I also do not have an EGT issue when towing. I have the larger 16cmsq housing, which does flow much more then my stock 12cmsq housing did. Trade-off was less boost at lower RPMs, which means I smoke some(alot if I need to) on take offs. But it really helped at the upper RPM band, I have much more power and the EGT's are not an issue anymore. I tow a 16,000lb trailer without worry in OD and up and down what ever hills I come across. I also monitor per and post turbo EGT, and have been very pleased with the set-up. I thing with it like this and the ATS trany locking up and keeping you locked in 4th gear around town, it is very easy to hit high EGT's (1200 pre) by lugging the motor down. I now always use the OD off in town and around congested areas, it keeps the RPM's higher which keeps the EGT's lower, also I will build more boost and the E-brake is more effective. I just thought it was an interesting study of how the engine performs at high fuel levels and low boost. The ability to breath is as important to us as it is to the diesel engine, you can throw at the fuel you want at it, but without the right amount of air you have nothing.

 

[CATCRACKER]

part of the reason you have low egt's is b/c your transmission is not locking up at lower speeds you are running on the fluid coupling which takes unused hp and turns it into heat. lock the transmission up at lower speeds and watch your egt's skyrocket look at my signature you will see i know this from experience.

 

[MatthewPark]

>Read my post again. I said exactly what you said.



You didn't say exactly what I said. You are stuck on the boost pushing exhaust out. That's not what cools EGTs down.



>I never said the exhaust backs up, I said it builds up in higher gears



Explain the difference of "backs up" and "builds up" to me. Either way, it has little or no effect on EGTs.



>I said it builds up in higher gears cuz it is not moving as fast through and out the turbo, hence slower moving exhaust gases= hotter EGTs



That's NOT what I am saying. I'm disagreeing with you EXACTLY on that point.



What creates hot EGTs is THE TEMPERATURE OF COMBUSTION. Boost doesn't cool EGTs by pushing exhaust out, it cools EGTs by giving the engine air to burn the diesel with. At low RPMs, what happens after the exhaust leaves the engine is irrelevant. If there was so much exhaust "building up", it would just push through the turbo faster and create boost.



I'm not here to start a fight. I'm asking you to explain your explanation of his EGTs, maybe so I can learn something if nothing else. You still haven't made an explanation to me that makes sense. Rolling your eyes doesn't explain anything.

 

[JGheen]

>Read my post again. I said exactly what you said.



You didn't say exactly what I said. You are stuck on the boost pushing exhaust out. That's not what cools EGTs down.



>I never said the exhaust backs up, I said it builds up in higher gears



Explain the difference of "backs up" and "builds up" to me. Either way, it has little or no effect on EGTs.



>I said it builds up in higher gears cuz it is not moving as fast through and out the turbo, hence slower moving exhaust gases= hotter EGTs



That's NOT what I am saying. I'm disagreeing with you EXACTLY on that point.



What creates hot EGTs is THE TEMPERATURE OF COMBUSTION. Boost doesn't cool EGTs by pushing exhaust out, it cools EGTs by giving the engine air to burn the diesel with. At low RPMs, what happens after the exhaust leaves the engine is irrelevant. If there was so much exhaust "building up", it would just push through the turbo faster and create boost.



I'm not here to start a fight. I'm asking you to explain your explanation of his EGTs, maybe so I can learn something if nothing else. You still haven't made an explanation to me that makes sense. Rolling your eyes doesn't explain anything.

How does what I am saying not make sense? Lets forget about the "backing up or building up" comment for a minute. It is simpler than 2+2=4.

If your cruising up a hill in fifth gear @ 1700rpm and you give the engine more throttle to increase the vehicles speed, regardless of boost, the EGTs will go up because the engine speed is low. This is due to a heavy amount of fuel being injected into the engine at that speed and not enough air speed or boost to burn it all and get it out thus creating high EGTs.

Try that same thing again, in fourth gear @ 2400 rpm and you have safe EGTs cuz the engine is moving faster and able to burn all the added fuel due to the faster air speed and boost through the engine.

If you don't understand what I just said then I don't know what to tell ya except that reading more can go along way in ones quest to understand.

 

[MatthewPark]

>How does what I am saying not make sense? Lets forget about the "backing up or building up" comment for a minute. It is simpler than 2+2=4.



No, because that's what I was arguing. High EGTs in his case have nothing to do with exhaust building up or any BS like that. He simply can't get enough boost in there.



For our purposes, the only thing that controls his EGTs is the amount of air he has in his cylinder compared to the amount of fuel. RPM affects it because obviously you get more air through at a higher rpm, but if you can jam a ton of boost in there at a low RPM with a ton of fuel, your EGT's won't get high. The only reason RPM really affects him is probably because he can't get any boost in there. If he could get boost in there, we wouldn't be talking about this, because his EGTs would be low. You are way too bent on RPM. Think more about airflow, because that's what matters. I don't give a damn what RPM you are at, if you have enough air for your fuel, you won't have high EGTs.



>If your cruising up a hill in fifth gear @ 1700rpm and you give the engine more throttle to increase the vehicles speed, regardless of boost, the EGTs will go up because the engine speed is low.



Only if you aren't putting enough airflow through your engine to burn the fuel. You can throw a ton of fuel in there if you have sufficient boost to burn it, and your EGTs won't be high. EGTs are DIRECTLY related to your air/fuel ratio. You are too focused on RPM. Sure, higher RPM will allow you more air, but more boost does the same thing.



>If you don't understand what I just said then I don't know what to tell ya except that reading more can go along way in ones quest to understand.



Right back at ya.

 

[JGheen]

I don't know what your saying anymore. You keep contridicting yourself as before you said boost doesn't cool EGTs and now you are saying it does.

If what you are saying is right, then how come when I am cruising up a hill in 5th gear, I can get 30+ psi of boost @ 1700-1800 and my EGTs skyrocket. Because I am dumping in lots of fuel at a low engine speed(which translates into low airflow through the engine) and boost is not that same thing as airflow, it is a unit of pressure. You can have all kinds of boost with no airflow, but that just brings the temps up as the air is not entering nor exiting the engine efficently enough.

 

[Dual EE]

370s 1st tow

I got alil bored earlier and decieded I'd go drag my trailer around to see how the 370s did. I was really surpirsed at how much difference being in 3rd and OD going up hills was. In OD I really had to keep an eye on the guage whereas in 3rd I could hammer down. EGTs haven't been as bad as I thought with the stock turbo, but I think I'm going to need a GSK and DVs. 50-55 aint gunna cut it outta OD. My truck really seems to defuel at 2200 rpms.



Other then that she's running great Oo.



Nathan

My truck defueled at 2200 rpms also. Changed to 3GSK and now it pulls through 3k and above. In 3rd w/od off-I can go 65-70 mph.



When you added your 370 injectors-how strong were your power gains? (Seat of the pants?)I have been thinking about them as my next modification.

 

[ndurbin]

Dual EE



I really noticed it when I towed my trailer around, more than daily driving. Seat of the pants feel so far, I hoping I can get on a dyno sometime soon to see where its at. I think once I get a GSK, DVs, and a turbo the truck well really come to life. And I need to do some tweaking to my timing and a valve adjustment.



JGheen and MatthewPark



I see both your points. JGheen your saying that my EGTs are a problem in OD because my RPMs are to low, which doesnt allow enough air to get through the engine. MatthewPark your saying that my EGTs are a problem because I dont have enough air moving threw the engine regardless of RPM.



Am I correct here on both my assumptions? If I am then can I ask one question, what determines the amount of air flow through the motor? Is it, RPM, boost, cylinder volume cap. ?



Drawing back on somethings I remember from college; my engine will pull in as much air as it can everytime it takes an intake stroke, the only way I remember to change that is by using boost (increasing the air denisty) and increasing the amount of air it can pull in. So if what I remember is correct, the more boost I can create and the more air I can move through the engine, the lower my EGTs well be.



Thanks

Nathan

 

[Extreme1]

The '94-'95 auto trucks do defuel at 2200 RPMs. The manual trans trucks go a little higher but things changed considerably in '96. The 3k GSK kit will make a world of difference, trust me. A set of 181 DV'd will also make a diference if you you have a rough engine around 1,200-1,400 RPM, the '94-'95 autos trucks come with 131 DV's. See if the place you are getting the GSK kit from has a set of used DV's laying around, it was the best $50 I ever spent on my truck.



As for airflow, I used a wastegated 14 cm and never noticed a lag but that was pre-370's. I was running a #5 plate though. You should also check the exhaust manifold, that one can break the mounting ears off the head if it shrinks too much. A temp fix is to remove the end cylinder bolts one at a time and drill the clearance hole in the manifold out larger.



Come on up to Goerend's and put it on the dyno on the 11th.

 

[MatthewPark]

>I don't know what your saying anymore. You keep contridicting yourself as before you said boost doesn't cool EGTs and now you are saying it does.



When did I EVER say that? That has been my WHOLE DAMN POINT for this ENTIRE thread.



>If what you are saying is right, then how come when I am cruising up a hill in 5th gear, I can get 30+ psi of boost @ 1700-1800 and my EGTs skyrocket. Because I am dumping in lots of fuel at a low engine speed(which translates into low airflow through the engine)



Put a big pair of twins on there and run the same 30 pounds with the same amount of fuel. The 2 larger turbos will be flowing plenty of air to cool you down. The reason you are hot is because there isn't enough air. You have a small turbo that doesn't flow enough for your fuel at 30 pounds and 1800 rpm. Measurement of PSI is only relevant when comparing boost levels on the same turbo. My truck got hot as well at low RPM. I pulled the wastegate line, and now they are safe. My turbo can't flow any more, so I can't safely make any more power with my turbo, but it's safe the way it is.



ndurbin, you are somewhat correct. JGheen doesn't believe that you can ever put enough air through your motor at 1800 rpm to cool your EGTs with the amount of fuel you have. I'm saying you can. That's what turbos are for.

 

[JGheen]

If I am then can I ask one question, what determines the amount of air flow through the motor? Is it, RPM, boost, cylinder volume cap. ?

Nathan, just to answer your question, airflow and boost pressure are two different things. The air flow through the engine is limited by the cylinder head. If you throw on a aftermarket intake and exhaust manifold onto the engine with doing nothing to the head ports then you will still have the same airflow through the engine as the ports are restricting you from moving any more air. However, when it comes to boost pressure you can be running 30 psi or 40 psi and you will have the same airflow as before due to the head ports restricting it. You could even be running 100 psi and will still get the same airflow. The turbo flows air as well as compresses it, but again it will only flow as much air as the cylinder head ports will allow. Once the turbo reaches its max airflow due to the ports of the head restricting it, it will continue to compress the air, of course until the wastegate opens allowing the exhaust to bleed off and not spin the turbine wheel any faster creating more compressed air. A given port area will only move so much air as the volume of the ports will allow. An example of this would be the arguements of the Banks High Ram and Twin Ram intakes flowing more air into the engine. They provide more volume of air on the intake manifold to breathe from, but they do not allow more flow unless the cylinder head port volume has been increased as well. I personally believe that the Twin Ram intake on my truck does not flow any better than the stock single ram, but it does distribute the air more efficently to all cylinders and not starving cylinders 4,5 and 6 for air.

Now when it comes to RPM, obviously airflow will increase due to engine speed but again it will only flow as much as the head allows and if we want to get really technical airflow can improve with how much the valve opens, but I am sure Cummins has flowed their heads with the appropriate lift for max flow with the given port volume. You can have more or less flow through a cylinder head with a given valve lift but if the valve opens too much it is restricted by the port volume. If the valve opens too little the valve restricts the airflow. Regardless of the airflow you can throw any number of boost you want at the engine but of course only as much as the head gasket will take, but pressure is not volume dependent. Look at our hard injector lines for example. I can't remember, but they have something like 1500 psi (maybe more, I can't remember off the top of my head) of pressure running through them and they are only like 1/4" in inside diameter.

Hope this explaination helped in your understanding of airflow through an engine.



Joe

 

[Bob4x4]

Volumetric Eficiency!

 

[JGheen]

Volumetric Eficiency!

Yup, thats it, just had to explain it out some.