Diesel Place banner

1 - 15 of 15 Posts

·
Registered
Joined
·
771 Posts
Discussion Starter · #1 ·
I'm new to the forum, I've read through most of the FAQ's. lots of great info, its been a big help.

I'm still left with a few questions about my 6.5 and how it acts pulling a trailer. I have owned my 93 3/4 ton since new, everything is stock, the behavour of the engine has been the same since new. The problem or nature of the engine is, it does'nt like to rev or make little hp above 2300 rpm. The hp curve goes flat at 2300 rpm with this engine. I started wondering if the engine has ever worked properly since I seen a hp graph from a Banks brochure, it shows stock 6.5 making more hp with every rev up to 3400rpm. I don't think I have ever taken my 6.5 engine over 2600 rpm because it doesn't make hp after that just a little more smoke. Its the same trying to pull a trailer it makes no more power and the engine starts to heat in just a minute. I also have rarely used full throttle because the last 1/3 does,t make any hp almost seems to make less even at lower RPMs, just a little bit more smoke (not a lot). Under everyday no load driving it works great.

Is this the nature of the 6.5 engines or is it unique to this one?
Perhaps opening up the intake and exhaust will help it make more power in the higher revs? Or has there been something wrong with engine from new? I have recently had the IP timing, and turbo checked they were OK.

Any thoughts on the subject would be greatly appheciated.
 

·
Registered
Joined
·
189 Posts
Sounds like its not getting enough boost at higher rpm's. Sometimes have that problem with mine.
 

·
Registered
Joined
·
962 Posts
If it is smoking, then it is getting fuel, and not enough air. Sounds like a simple wastegate problem is all it is.

Eric
 

·
Registered
Joined
·
4,805 Posts
welcome.

factory exhaust is very restrictive. 3 or 4 inch exhaust will make a big difference. do a search for "downpipe"

your truck being a '94 I'll bet your downpipe looks like it was run over by a forklift before it went in your truck. That model year had VERY restrictive downpipes.

Do the exhaust first. You will notice an improvement, especially above 2300.

Smoke = not enough boost. check your vacuum lines.
 

·
Registered
Joined
·
771 Posts
Discussion Starter · #5 ·
My truck is a 93 but most likely if the 94 downpipe is bad then the 93 would be no different. I believe the wastegate to be OK because I had the turbo checked out not long ago. Do the factory mufflers have a lot of restiction? or is it the 2.75 Dia. pipe
 

·
Registered
Joined
·
8,014 Posts
If you want power you got to get it to breathe, all GM downpipes are worthless regardless of year, 3" is minimum required for exhaust I run a 3.5 Banks, GM factory program falls flat in fuel & boost dept, gears also a player check RPOs and see what you have. Go to performance thread in FAQ folllow it and depending how much $$$ you got will determine Hp you can make until you hit physical limits of the engines design
 

·
Registered
Joined
·
1,259 Posts

·
Registered
Joined
·
3,222 Posts
93= Mechanically injected engine, unless a transplant has been done here! What color is smoke? Black. Time maybe for a cat removal to help engine breathe better...downpipe help too. Just a few mods to help out before adding serious power that may harm the powerplant. Do your homework first, like getting gauges before getting too much extra in it.
 

·
Registered
Joined
·
771 Posts
Discussion Starter · #9 ·
It's performance has been this way since new, everything is original factory in the truck. The smoke is black and not a lot but it usally starts when the rpms/hp goes flat. I think what I'm hearing from most of the posts this isn't typical. I havn't drove anouther 6.5 to ever compare performance. I always felt like higher rpm performance was missing. I don't mind paying for good bang for buck performance increases but hate wasting money on snake oil.
 

·
Registered
Joined
·
3,222 Posts
A puff of black smoke, or continuous tinge of smoke, or billowing black smoke? Maybe an air filter/intake improvement too...
 

·
Registered
Joined
·
771 Posts
Discussion Starter · #11 ·
Are the crossover pipes a restriction, that is are they dinted or a problem from factory? Or you think it may be pinched from hitting a rock or such? I should take a look to see if the truck has a cat., I just assumed being a desiel it wouldn't. Also I'm from Canada (typically less polution requirements) and it is a Heavy Duty 3/4 ton.
 

·
Registered
Joined
·
771 Posts
Discussion Starter · #12 ·
About smoke, continuous and a little more than a tinge
 

·
Registered
Joined
·
771 Posts
Discussion Starter · #13 ·
Thanks nickg for the link I should have went to it before my last post. That crossover pipe in the picture is incredible!!!!!!! bad that is. You may have solved the problem. I think I will buy a bigger exhaust system after seeing that BS. It would really tick me off to think I've drove this truck all these years putting up with low power. But better late than never!!
 

·
Registered
Joined
·
378 Posts

·
Registered
Joined
·
538 Posts
Yes, Kennedy's mod is quite well described and an easy fix-up. I agree with the others in the boost department. My truck stock (don't know if electronic IP makes a diff.) would never smoke, even with a good foot in it. Unless thats the computer controlling fueling output im not sure.

Maybe a boost gauge is in order. That would give you a good idea.
 
1 - 15 of 15 Posts
Top