Poor towing torque... recommendations?

[1995chevyTD]

So I've had this 1995 2500 since spring. About 200k on it.

Fairly stock engine when I bought it... relocated pmt, later injection pump, had a turbomaster and gauges installed, guy was only running about 5psi and a stock chip.

I added a 4" exhaust and larger crossover and tweaked the boost up to about 10psi. Plenty of torque towing and okay mileage, but I would trip the overboost regularly, so I kept down at 8psi or so.

So after reading the reviews, I bought a Heath towing chip and redjusted to about 10psi. Love the glowplug starting sequence, the transmission control is great, the exhaust temps are about 200 degrees cooler at the same boost level, and mileage is even better. Exhaust note is almost muted... sort of like when the stock chip would throw a code and defuel.

For several months I didn't have the occasion to tow more than 1000# or so, but when I did I was very unhappy. The problem is that while running unladen is just fine (and I can feel no power issues), once I hook a trailer to the truck it is gutless... far worse than with the stock chip at 8psi. I struggled to maintain 60mph on an only moderately hilly interstate towing a small enclosed trailer (only about 3000#) and the cooling system (but not the exhaust) would heat up quickly and mileage dropped to about 10mpg (I had been getting 14 towing the same weight on an open trailer before with the stock chip).

I took it to a local diesel guy who checked everything out (smoked the system, etc) and talked to Heath. His diagnosis was that the chip was designed for max power at 15psi and since I was only running 10 I was never getting into the "performance" arena... so the chip was not fueling for power... hence my lowered power. He recommended running 13-15psi to make the most of this chip.

He also said at 200k my turbo might be a little tired since about 12-13psi was about all it could maintain even with the TM.

So do I:
1. Run whatever the turbo will put out and live with the results?
2. Buy a chip that will give me more power at 10psi more like a stock chip but not trip the overboost?
3. Go all out and do an A-team turbo and tune?
4. Buy a 7.3? LOL...

I'm really just after a little more power and mileage than stock... and I don't think I have that currently.

Appreciate any thoughts...
Thanks!
Bill

 

[WarWagon]

I suggest you take a look at:
your fuel system for: bad lift pump, ops, or restrictions or air.
miles on injectors?
exaust for leaks.
possible plugged cat.
intake restrictions - the kind you cut out from factory.

Injectors are good for ~100K then you rebuild them.

With the turbo master tightened up you should get at least 15 PSI of boost with a load. Likely you are not getting enough fuel due to: a bad lift pump, plugged tank sock, plugged filter, kinked hose, sucking air at the top of the fuel tank pickup assy, or bad OPS explained here. http://www.thetruckstop.us/forum/sh...t-Pumps-amp-OPS-operation-and-troubleshooting

As far as towing with the POS factory turbo, GET RID OF IT! Here is why:

http://www.thetruckstop.us/forum/showthread.php?37051-maxxTORQUE-article-on-the-A-Team-Turbo

 

[Woody35]

If you want a lot of good towing power option #3 will give you the most out of that list except for maybe the 7.3. something is wrong with your turbo if it can only produce 12-13 psi with the tm cranked all the way down. Are you sure the wastegate is shutting all the way? If Heath says your tune needs 15psi your gonna need it to burn all the fuel its commanding or else its just going to hot smoky pig as you have found out which is detrimental for your engine especially while towing.

 

[sshewins]

X2 on everything that's already been mentioned. Plus, welcome to the stop!

 

[1995chevyTD]

Thanks for the feedback!
bad lift pump (did a quick test, seems fine, new one on hand to install but haven't)
ops (gauge works fine, LP seems to; have not tested further but for $30 I'll replace)
miles on injectors (unknown. newly rebuilt set on hand but not yet installed)
exhaust for leaks (all new)
possible plugged cat (no cat or soot trap)
intake restrictions - the kind you cut out from factory.(stock breather/assembly)

The issue I'm having is simply that I had significantly more torque with the stock chip at 8psi than the heath chip at 10psi... even given the other possibilities this seems strange (unless there was a coincidental simultaneous failure somewhere). I was satisfied with the stock chip's power level at 8psi... but on long runs I'd still sometimes throw an overboost code.) I'm tempted to throw a stock chip back in and see if my torque returns...

Bill

 

[JiFaire]

Hi Bill, welcome to the site!

Can you find somebody with a Tech-2 (or a laptop with OBD-I tuning software like autoengenuity or GMTDscan on it) and check the timing settings? If possible, you want to get the IP set to -1.94.

Check for exhaust leaks again, particularly in the crossover gaskets on each side... doesn't take much to make a GM-4 crap out.

Air filter... if you're still running the flat panel filter in your '95, make sure its clean and that the snorkle is removed from the fender.

Lift Pump and fuel restriction, you're already looking at. You might want to put a cheap gauge on your water drai fitting with about 7' of hose, run it out and tape it to a wiper so you can see fuel pressure when you're pushing on it. It should always be above zero, even at WOT.

Getting boost is about getting enough air in, enough exhaust out, and having enough fuel (at the right time) to create drive pressure. Fuel and air are a parasitic cycle... you need lots of fuel under load to produce boost, you need lots of boost under load to burn all that fuel. If you fix the inputs and outputs, then your timing is probably the missing piece.

 

[sshewins]

Almost forgot. Your stock lift pump is voltage sensitive. Which means make sure the ground is perfect or you lose some of the voltage needed to operate the LP.

 

[WarWagon]

...
intake restrictions - the kind you cut out from factory.(stock breather/assembly)
...

The issue I'm having is simply that I had significantly more torque with the stock chip at 8psi than the heath chip at 10psi... even given the other possibilities this seems strange (unless there was a coincidental simultaneous failure somewhere). I was satisfied with the stock chip's power level at 8psi... but on long runs I'd still sometimes throw an overboost code.) I'm tempted to throw a stock chip back in and see if my torque returns...

Bill

I have run the flat panel filter with good results. K47 filter box is an upgrade but not required for the issue at hand. The restriction is the part between the filter box and the fender. Factory narrowed it down to ~1/2 diameter. Cut the restriction out so it is open to the entire fender inlet. When you pull the part out you should see the restriction. The snorkel in the fender is the next thing to go IF it has one as some years did not.

I don't recommend throwing parts at a 6.5 without checking them first. Regardless, OPS unit have a switch in them for the lift pump that burns up often and will not affect the oil pressure gauge. Couple of pins into the lift pump connector with the engine running and lift pump plugged in should give you a voltage reading. Should be close to battery voltage as a bad OPS will be 7v or so and the lift pump will not be running.

Are you getting steady black smoke with the tune and low power? This would indicate lack off boost when you need it. No smoke means plenty of boost, but, not enough fuel. Timing affects smoke as well.

What was done with the IP being a later model? Possible different model pump? Maybe need a tune for the specific IP in use?

Maybe double check the Turbomaster installation as different years have different ways to install it at the WG lever.

 

[1995chevyTD]

Air filter box is already modified and snorkel removed.

No smoke at all except on startup... so a lean situation is indicated.

Hooked up my cheapie plastic fuel pressure gauge... not very reliable... but indicating only 3psi at idle (5psi engine off but pump running). I can get it to zero out without even winding up the engine. Think it's time to replace the lift pump and OPS (and buy a better gauge at some point)....

ASAIK, timing is stock...

 

[WarWagon]

Air filter box is already modified and snorkel removed.

No smoke at all except on startup... so a lean situation is indicated.

Hooked up my cheapie plastic fuel pressure gauge... not very reliable... but indicating only 3psi at idle (5psi engine off but pump running). I can get it to zero out without even winding up the engine. Think it's time to replace the lift pump and OPS (and buy a better gauge at some point)....

ASAIK, timing is stock...

Hopefully a lift pump will help it. If not there is a restriction like a kinked hose or a plugged tank sock. Best advice if you drop the tank is to loose the sock and use a Walbro with built in screen or prefilter before lift pump. Possible air leak.