yager

16196396 / BDUZ / $9A - 95 C2500 truck tuning

Ok the other thread got my butt in gear to actually start some logging on my truck, its a 95 C2500 5.7 5 speed, 3.73s. Primarily used for towing my jeep and ocasional DD use.

Ive done some basic edits on my jeep enough to get it running and to do the RPM rev limiter hack etc.. This is my first real effort to log then tune. Ive read so much about peoples specifics I think ive lost the basic steps to learn to make my own decisions about what to do...

Some background on my truck...
1) The truck has 188k on the ticker, I believe the motor was swaped out to a 91 C1500 5.7 (not sure when) this is based on the EGR valve OEM # only fitting that 1 application when i swaped on a new one.
2) MPG isnt great DD but towing 7k load i get 10mpg which is what i expected getting the truck. Power isnt that great but my jeep sits tall on the trailer and is literally a brick with no aerodinamics... But id like to see a little better empty MPG without hurting the towing..
3) I've changed the EGR, TPS, fuel filter, air cleaner, coil, cap/rotor/wires/plugs all within last few months.. I still have an odd stumble 1200-1500 rpm when under slight load where the truck will buck/surge some. It has new u-joints/carrier but there still seems to be some good drive line slop, and i may just me lugging it to low..

3) It seems to run a little rich across the board and the numbers seem to support that ? (yes/no?)

This truck is bone stock but its possible the engine was changed, should I attempt to tune this bin, or possible seek out the original engines bin and see how that works?

Where do I start? What should i look at first ? I have a winaldl log from my 45min drive to work. Ive pulled it into excel, but am not sure what items to look at first and what all the data im a bit overwhelmed...

Where do I start? Any help appreciated.. (I have more data i can post. Thanks -mike


BLM
Wide Avg
RPM \ MAP 20 30 40 50 60 70 80 90 100
400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
800 114.0 119.6 119.3 118.0 117.8 118.3 0.0 0.0 0.0
1200 114.1 116.2 105.0 110.3 106.8 105.4 107.3 116.0 0.0
1600 116.4 114.3 108.7 106.3 105.5 106.9 111.3 119.5 121.7
2000 115.5 112.9 107.0 105.6 106.2 108.7 113.5 121.3 0.0
2400 123.5 115.5 107.0 106.8 108.0 110.6 113.5 123.0 120.0
2800 107.0 123.0 119.8 106.0 112.6 113.0 117.8 117.7 0.0
3200 0.0 126.0 105.0 0.0 126.0 126.0 116.5 115.7 0.0
3600 0.0 0.0 0.0 126.0 0.0 126.0 116.0 0.0 0.0
4000 0.0 0.0 0.0 126.0 0.0 0.0 0.0 0.0 0.0
4400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
4800 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5200 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5600 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

INT
Wide Avg
RPM \ MAP 20 30 40 50 60 70 80 90 100
400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
800 129.0 127.3 125.5 129.0 127.8 125.3 0.0 0.0 0.0
1200 126.3 127.5 127.0 123.8 118.2 117.5 120.9 130.0 0.0
1600 126.2 129.8 119.1 119.5 122.3 126.4 128.0 132.1 136.0
2000 127.7 127.1 117.2 120.2 123.9 129.3 129.3 132.5 0.0
2400 126.6 122.3 118.2 119.2 125.0 129.8 124.8 126.5 136.0
2800 128.0 126.0 127.0 119.0 128.8 117.5 125.0 129.7 0.0
3200 0.0 128.0 123.0 0.0 128.0 128.0 124.5 123.7 0.0
3600 0.0 0.0 0.0 128.0 0.0 128.0 125.0 0.0 0.0
4000 0.0 0.0 0.0 128.0 0.0 0.0 0.0 0.0 0.0
4400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
4800 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5200 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
5600 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6000 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
6400 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Grumpy

It's easy to lug some of the newer engines, since they have enough ignition and tuning to allow you to put the engine in really high effort areas, without having enough engine speed to actually work well there.

Get things as mechanically right as you can. You seem to have gotten that you don't want to chase a tune up problem, by tuning around it.

Start with a known stock .bin.
And when you have the tune pretty close, go back to it, and restart with the info you learned in doing the first one. Notes and repeating that cycle will work wonders for your learning curve.

Look to get the BLs with say 118-138. Close is OK there, then work on seeing if you have any knock, and drop the timing just before you see it starting, and possibly add a touch of fuel.
Do lots of MPG checks to see what amount of timing the engine really likes in cruise conditions. BTW, around town MPG can really mess up your MPG calcs, so be extremely diligent if you do any so as to repeat the fuel consumption accurately...

rooster433

Is the prom your using know a stock prom? Does it have a decently fresh Delco O2 sensor? Is the timing set to factory (believe 0 on those trucks... could be wrong) with the EST disconnected?

If so, than theres no real reason why you couldln't start working at the VE tables already.

What I would do is take your wide average BLM and divide it by 128 then multiply it by your VE in that particular RPM vs MAP cell. All your doing is coming up with a correction factor to change your fuels by.

I'd reccomend building a excel worksheet to do this quickly. After a few iterations you should see the average BLM's come closer to 128 and the driveablilty and gas mileage should improve.

87tpi7749

Try to drive it with the egr vacuum hose off. I've seen the wrong egr sold to people in the past, it can cause this tip in hesitation. If problem goes away. You need to take a close look at the egr operation. Do you have stock exhaust system?

yager

Thanks all for the input.

Yes ECM/Prom is factory, heavy dust coating and all. OEM exhaust and look like its the original 188k unit, muffler has some pin holes but still holding up.

EGR came in a box with when I bought the truck, off a friend, as was showing an EGR code so i needed that to at least pass inspection.

Ok so ill strart with a new O2. Im not 100% on the base timing so I will check that this weekend. Im not sure on the bin setting but ill look in the other bins to see what it is. (I havn't pulled mine out to read it yet) It defintly has EST connected, i doubt it'd get out of its own way if it wasn't.

After that ill log some more to see if ive made any changes, honestly i think ill will need to so i need to start on the TP XDF to do the edits. Ill find the VE tools ive seen to simplify the math/edits on those.

Q) After the VE stuff is cleaned up some. Is doing the timing as simple as adding in some more and watching the spark counts?

Q) Grumpy I know you've spoken about your burb and the tuning youve done with that, any advice for a towing specific tunes ? Things to be cautions of ?

Again thanks, im sure this is all old hat and i hope to have the whole process understood eventually...

HaulnA$$

Be careful with the timing. I have tuned many trucks and can offer this. The swirl port heads do not like a bunch of timing in a heavy truck. 30-32 degrees max with a stock setup. As for the cruise timing, the heavier the truck and/or load, the less timing the engine likes. Towing causes the engine load to change very abruptly with so the transition from cruise to high load timing becomes touchy. Make very small changes and log the data. There are significant gains to be made in the timing tables if you are diligent. HTH

Grumpy

I always leave alot of non-PE timing retard available. Nothing worse then a bad tank of gas when your towing, and having to not use the throttle cause it's pinging.

The leave all the 85+ areas or PE AFR on the rich side to help prevent letting the chamber temps running away.

Back down the max allowable timing a few degrees.

I have a 91 3/4t 454, that I've done all the above with that's really a pleasure to tow with. One trip was with the car and trailer, a 500 caddie engine, a SVO, and an AL SBF. Other then the car you'd hardly have known the extra stuff was even there.

Towing really is about using the least amount of timing that makes the engine happy.....

rooster433

I aggree.. I would try to keep the higher loads AFR on the fat side also to keep everything cool during long periods of high load like pulling up a hill.

TrofeoS/C

I have basically the same truck in a 4x4 (and 237K on the clock) I did a little tuning on it, more than anything to back off the throttle follower.

I gained ~2mpg and a noticeable increase in power by adding a couple degrees to the PE spark tables and backing the PE delay to 0.

I tried leaving a little delay in below 2400 RPM, thinking it might get a little better mileage, but found it annoying and didn't help any, so burned a chip without it at a Waffle House in Ohio...

yager

Today i checked the timing, it was at 2 BDC, sticker called for (edit) 0 / ZERO, so i set it back. And I also unhooked the EGR as suggested. While at the hardware store (house plumbing) i hooked the EGR back up to see if it was just the timing or the egr... Definitly EGR as it was doing the same random hicking up and bucking.. Was more noticiable after it was fixed, guess i was compensating with my driving and didnt realize it..

Anyway... timing corrected. So ill do some more logging next week..

EGR - Its a new valve and its not leaking vacume so could it be the EGR solinoid? Or an incorrect EGR not 100% on correct part... Will it hurt much with it unhooked?

Throttle follower ya its a bit much, but with the long throw on the nv4500 tranny, it matches my slow shift speed well.

The other thought i had was about using 2 burns - I noticed Moates has a twin shot deal for two burns with 1 simple toggle switch.. Q) If i was to make a tow oriented burn other than whats been suggested should i try anything else?

I know I can't get info about the towing until i log while Im actually tow. But last time I towed the jeep, I felt like my foot was on the floor on the hills but if i pump the pedal i can recover some lost speed.

Thanks you all for providing input.

Grumpy

Try replacing the EGR with just a flat plate of ~3/16" steel, and see what happens. Some EGRs use back pressure to aid/ open them, so you want to eliminate that possibility.

EGR takes timing and fuel to work.
Too little of either and you'll have a chuggle (EGR based, surge)

By totally eliminating the EGR and noting the results then you can tune from there, first without it to see what *good* is, and then with it to see if you can match *good*, of course this would be for off road use only.

HaulnA$$

Two things. First, TBI trucks are notorious for clogging the EGR passage in the intake manifold. With the milage on your engine, I'd bet good money that this is your problem. Second, it won't hurt to disable the EGR valve as long as you do it right and that means disabling it in the chip. The chip will add a bunch of timing when it thinks the EGR valve is on. Disable the error 32 test bit and set all the EGR enables to maximum. I usually go a step further and zero out all EGR related tables. HTH