weak injector pump or any other ideas???

[Shawnr001]

So I put a good working turbo on my 1996 GMC Suburban and there is a big improvement in performance, obviously. I also did the turbo master trick and on big long hills I can get up to 10PSI boost. But now I have to address some other issues.

When taking off I initially get good strong acceleration up to about 2100 rpm, but then even if boost pressure is still climbing performance slacks off. I see no black smoke so I'm thinking the injector pump is leaning out and can't deliver enough fuel. What do you think?

Also, to worsen the issue when the engine gets over 200degrees performance slacks off dramatically.

For example, If I'm doing any heavy pulling, I can start the day and the engine is at 185 degrees or lower I can pull a 8,000 trailer up to 70mph no problem, or 50mph up 5-6% grade. But if I let the temp reach over 210 performance drops like a rock. Especially if I get over 220. It's so bad that the only way to get up those 6% grade hills is by putting it into 1st gear and allowing the engine to run up to 2,800 rpm... At this point I'm only going about 20mph and really having difficulty keeping the temperature reasonable. If I try to shift into second and use some torque I risk overheating in a very short amount of time.

Any ideas?

 

[Will L.]

Sounds like your new good working turbo is a GM turbo. 2200 RPM is usually the chokepoint for these turbos. Above that it turns into a big hot air machine. Most of these guys have learned to keep their engines below 210°F I will push my little bit above that but for very very short periods of time. I will hit 220 maybe 225° for up to four minutes at a time. You go much beyond that will become very experienced inside of this engine.

As you can tell difference in temperature makes a lot more power. Put on and EGT gauge to monitor what's happening and do the cooling upgrades do you read about on this forum with the balance flow water pump, fan clutch, and Duramax fan. This will keep your engine coolant temperatures down and keep you in a better power range as well as a longer life and that engine. As the engine heats up it, works harder, it raises the EGT's. This intern raises the IAt's. The hotter air is already expanded and cannot allow The higher volume of air and fuel to give you more power. For people that are happy with their turbo don't want to change that and they're fighting the issues at the top end like you are that's why they look at WMI systems- It lowers the IAT's allowing for more power and helps in slowing the overheating process.

The GM Turbo was put on was not the most efficient turbo designed, they could come up with - it was the most economical. With my hummer I am stuck with the GM-6 turbo if there was any way I can do it, I would so gladly spend the $ for the ATT turbo. It will pay for itself in fuel economy And the added power is just a bonus.

Do you have a fuel pressure gauge installed? What's the fuel pressure at Idle and WOT? What kind and how old are your injectors & what are the pop pressures currently? There's a long line of improvements to be made for this engine if you read through the stickies on here. Lots to do before worrying about an IP.

 

[great white]

So I put a good working turbo on my 1996 GMC Suburban and there is a big improvement in performance, obviously. I also did the turbo master trick and on big long hills I can get up to 10PSI boost. But now I have to address some other issues.

When taking off I initially get good strong acceleration up to about 2100 rpm, but then even if boost pressure is still climbing performance slacks off. I see no black smoke so I'm thinking the injector pump is leaning out and can't deliver enough fuel. What do you think?

Also, to worsen the issue when the engine gets over 200degrees performance slacks off dramatically.

For example, If I'm doing any heavy pulling, I can start the day and the engine is at 185 degrees or lower I can pull a 8,000 trailer up to 70mph no problem, or 50mph up 5-6% grade. But if I let the temp reach over 210 performance drops like a rock. Especially if I get over 220. It's so bad that the only way to get up those 6% grade hills is by putting it into 1st gear and allowing the engine to run up to 2,800 rpm... At this point I'm only going about 20mph and really having difficulty keeping the temperature reasonable. If I try to shift into second and use some torque I risk overheating in a very short amount of time.

Any ideas?

Stock tables start pulling fuel above 2200 rpm:

that's part of your problem and one of the players in these things going "flat" above 2200. That's the OEM tables, mine are a little bit more....well, more.

Others, IIRC, are the fuel modifiers for ECT and IAT when they start pushing the upper limits.

You're not hitting overboost (pulls fuel) if you're barely getting 10 psig so that's not the problem.

GM turbo gets a bad rap most times, but it's not always the problem. IAT is probably not so great closer to 10 psig, things are getting hot at that point. I max out at 13-ish psig but I'm running water injection.

Recommendations?

Start with some cooling system work (cleaning, high flow pump, etc) and a toss in a decent recalibration.

Then gather up some cash for a little better exhaust if you're still OEM.

Popular thought is to go right to the turbo, but I play a little different game....

 

[great white]

I should also note that there are cells in the chart where fuel is pulled for a good reason. Absolute numbers don't always mean what you think the would when you're looking at them...

Lots of other goodies (like timing tables) play in to the final solution...

 

[WarWagon]

The factory turbo is restrictive. A restrictive exhaust keeps heat in the engine. The heat locks in the cooling fan taking away power. It also costs you fuel economy. The fuel on a factory rig is turned down in the upper RPM because the factory turbo won't let the engine get enough air to burn it all and it starts to smoke black.

Cooling improvements do help, but, it is just as well to also let the heat get out of the engine. Here is an in depth look at trying to make the factory turbo work for a living.

http://maxxtorque.com/dieselcommuni...ods/244-the-65-factory-equipped-asthma-attack