Engine/Transmission (1994 - 1998) Stock- boost vs RPM curve

[TurboFan]

I have allot of questions I guess. Read on if you're bored!



I just installed a boost EGT gauge on my presumeably stock 96 12v 5 speed, and I was wondering what my boost should be at any given RPM. I know I'm probably dreamin on that. Seems like there should be an approximate curve.

Max boost stock?



Before you get too deep in though on that, i'll tell you that I have an SPA Technique combo gauge. crap, I gotta tell ya what I did. I put the boost sensor on the end of a 5 inch tube because it wouldn't fit in the factory manifold hole. The injector pump is in the way. Will that affect the readings?

I'll make fixie when the temps get above zero. My fingers are cold!



The mighty Cummins is supposed to develope peak torque at 1600 rpm, but mine doesn't do ANYTHING until about 1800 rpm, and doesn't really get with the program until about 2100-2200 rpm. The seat of my pants puts peak torque at 2200rpm.

Then power drops off sharply at about 2700 rpm. That's why the steering wheel shaped mark on my forehead. Just about the time I start thinking we're getting somewhere, it's over.



I noticed that on mine, boost peaks at 2500 rpm (about 25 lbs), then drops off as rpm continues up. it doesn't maintain max boost. Should it maintain max boost?



Okay don't harp at me for doing it. Another thread suggested it is not harmful to rev to the governor unloaded. They even suggested it is a proceedure for checking tach calibration. It galled me, but I did it. I eased it up to wot and the rpm stopped at 3125 rpm.

Do I already have a 3gsk in there?



For the first couple of miles on cold days there is a bump in the rpm as I decrease past about 900 rpm, as I let it go back to idle. Is that a stock thing? I've read that 3gsk can do that?



Also while I'm asking, (thanks for your patience) When I first bought it about 4 months ago, I could see very faint black smoke going up a steep hill (wot or nearly so). also, when I wound it up to maybe 2600 rpm on only 2-3 occasions it put out a cloud that would block out the sun. Not every time, and never since those 2 or 3 times.

Do cats get sooty with mild driving/sitting and then "clean out" when you romp on it?



Lately there is NEVER any visible smoke. That's not a bad thing by it's self, but tells me that I'm not fueling like it was before. Right?

I'm in Alaska, maybe it is due to winter diesel?



Thanks for wading through all that!



I'd like to hear your opinions on what you think I'm looking at.

 

[REFLOYD]

to me it sounds like you have the 3k gsk kit in your pump. mine truck wont go above about 2550 rpm.

 

[NIsaacs]

I am not sure what you mean about the 5" tube thing on your boost connection. It would be better if you went directly to the intake manifold. There should be one or two 1/8" pipe plugs along the length of it somewhere.



Boost is more of an idicator of fuel used (power) than RPM. I would say that 25 lbs max boost was more than stock fueling, however I am not very familiar with the P-pump 2nd gen.



Yes, when you first stomp on the go pedal, after several hundred miles of just cruising around, you will get a blast of smoke. This will clear up after several high speed runs.



You started your post with [boostEGT} did you mean boost and EGT gauge? What are some of your EGT readings?





"NICK"

 

[WAnderstrom]

I have a 95 and mine won't rev past 2650. Also my stock boost was like 17 psi. I now with a 10 plate get 26#. I wonder what plate you have? Have you looked to see if it had been changed? My truck because of the 10 plate starts defueling in the upper RPM range and I see a drop in boost as well. I just caught my KDP creeping out a couple of weeks ago and hope it isn't far down on your list. One of our fellow members in Anchorage lost his and had a very sad Thanksgiving. Good luck.

 

[JJW_ND]

Sounds all normal for a 215hp

My 96 5sp would rev to 3K or slightly over stock. With 3GSKs you will rev to 3500 easy (driving ... . not just in neutral). Stock boost on mine was under 20psi until over 2K rpms. Your engine has lots of power potential depending how you want to use it. Timing even on a truck that will stay stock is a good think to check an make sure it is at least 15 degrees or slightly above.



You will get lots of advice here.



jjw

ND

 

[TurboFan]

You started your post with [boostEGT} did you mean boost and EGT gauge? What are some of your EGT readings?

"NICK"

Hi Nick. Actualy I did say Boost egt gauge. Anyway, My peak EGT so far has been 1080. That's high end rpm wot of course. I don't have much else as the gauge is only days old. No level cruise numbers either. Not much info I know. I'll get some more numbers.



I included it more as a comical confession, but as for the boost sensor, the sensor wouldn't fit in the factory provided hole (too close to the injector pump). so utilizing a couple of fittings, and a 5 inch long piece of tubing, I connected the factory hole to the sensor.

Like I said in the first post, it's below zero here (I work outside) and in order to mount the sensor on the manifold, I will have to drill and tap a new hole, which to me means pulling the top of the manifold. Too big a project for working in 20 below zero conditions. It will happen in the summer, or at least warmer winter temps.

It doesn't look like it will affect pressure readings. Maybe a momentary delay.



Thanks,



Greg

 

[TurboFan]

WAnderstrom



Hey neighbor. Wow, yours won't rev above 2650, and REFLOYD's won't go above 2550. JJW_ND's revs pretty high, but sounds at least likely I have a spring kit in there.

I'll have to open it up to see I guess. I want to see it all for myself sooner or later anyway. Same for the plate.



Yup, the KDP is a worry that I will get to with oportunity. Soon I hope.



Take care you guys

 

[JJW_ND]

215 hp engines in a different league ....

If your 96 - 98 215hp 5sp engine did NOT rev to 3K stock, there would be something wrong. Auto trucks were governed less with older years 94 - 95 the worst.



If you like the rpm range you have DONT TOUCH the Govenor springs! Govn springs have a big affect on cold weather starting and cold engine operation. If you don't want more rpms you can NOT improve on the stock springs or their setting in a 215hp truck.



The same applies when talking plates and injectors. Only compare 215hp trucks to 215hp trucks. A #10 plate in 94 auto would be a very modest power upgrade with no EGT issues. In your 96 5sp, it will run very high EGTs, add over 100hp or more. The stock 215 injectors are pretty decent. Unless you need insane HP, stay with them. A plate gives you much more control over power increases with its ability to be postition to increase or decrease power.



jjw

ND