• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Open discussion on the factory VAC boost control

Status
Not open for further replies.
G

great white

Well-Known Member
Messages
4,007
Reaction score
109
Location
Canada's Ocean Playground
So, I'd like to discuss why the factory boost control system is seen to be "not so great".

I just finished installing my Auber boost guage and have a day or so of running with it.

From watching the readings, it seems the factory program does a relatively decent job in the way it manages the boost.

For example:

On just a drive to work, the boost is anywhere from 0-.5 PSI on a nice flat run once the throttle is steady and load% is leveled out. Good for MPG IMHO.

Throttle application brings the boost up pretty quick to around 5 psi and I have seen a max spike of around 11 PSI on heavy throttle punch (but only a few seconds and then it dials back). As the load comes down, so does the boost.

Climbing up a hill has the PSI at a pretty much steady value somewhere around 3-7 psi, depending on the hill, throttle position and load %.

Trans shifts have the boost backed off for shifting and then ramping back up after gear change. This makes sense from a longevity point of view.

From what I'm seeing, it seems like the factory program manages the boost fairly well for MPG and modest performance.

The "complexity" of the vac system isn't a big deal to me. Just another system to be maintained properly. Fact of life on "newer" vehicles.

Keep in mind, my truck is mostly a commuter, so my needs for boost might not be the same as someone towing heavy loads or looking for "speed" out of a 6.5.

I can make a short vid of my display and values if anyone wants to see for a frame of reference.

Feel free to discuss.....
 
throw a trailer behind and I think you'll feel differently. On mine even empty the boost would go away on a hard accel up a hill. I also never saw over 7-8 with vac. Now with TM I have 3-4 on a flat level cruise 12-14 under load.
 
I completely agree with AK... put a trailer of even medium weight behind you, and head for the hills.

If you still want to talk about how cool the factory vac system is after that experience, I'll buy the beers.

And for the fuel mileage argument, I admit I screwed up, changing the chip (from stock to Heath Maxetork) and boost control (from stock to TM) at the same time, but I was on the Holiday from Hell at the time, and after making these changes, my towing mileage went up a consistent 2 mpg, and my headaches and fear of hills disappeared at the same time.. any time you can get both more power and better mileage, grab it.

I have not once regretted changing out my factory boost control, over 4 years and about 120,000 km, with lots of heavy towing and lots of empty highway. Not one regret.
 
I side with above posters.

when mine was still stock boost was mostly none existend,top boost was only 3 at the most.Cruising there was none. There's plenty of get go now with the TM.

My wifes 95 is still stock (i got to change that this fall,she keeps on whining about it after driving my truck)and there is no comparison between the 2.
 
Jeez guys, I only want to discuss how the factory system works, what it does, how it does it and the reasoning behind why it works like it does.

I'm aware of the TM benefits from reading the forum. I may eventually end up with a TM for all I know.

You guys are like a pack of ravenous dogs sometimes.......;)
 
Sorry, BJ - I can't think of a lot of benefits to the Vac system. In theory, it works fine... it can be set to compensate for altitude changes, for load changes, to respond to variance in IATs, and to follow the fueling curve. It would be much better if the truck had the ability to read EGTs and airflow and factor those into the equation, and personally, I'd like it if the vacuum part were more reliable.

But the true TM tends to function very well between a fairly wide range of operating parameters, and is simple and foolproof, which is definitely an advantage when towing heavy in high ambients in the mountains. One really crappy experience in that situation tends to sort of sour one on the benefits of letting the GM engineers handle your boost...
 
I like the vac. system. With the right programing it works great. The factory programing sucks. As said, it cuts boost when needed most. But that can be changed with a chip or reflash.
I still believe a computer can be smarter than a spring. I don't think it's that big of a deal to keep working.
 
Well I am one of the few that is running the vac boost control with a custom chip. It works very nice & I think iirc correctly that I have read on the forums that even Mr. Heath will attest the vac boost control can far outperform the spring when it is tuned correctly.

This argument reminds me of the discussions that take place on the HTT Harley site about EFI vs carbed bikes or like when the auto industry went from points & condenser to electronic ignitions.
 
Yep - a friend of mine has one of Lyndon Wester's custom chips (Lyndon's generic chips are what SSDiesel sells, and what John Kennedy used to sell before he bought Lyndon's programming interface and equipment and started working on his own).

He swears by his chip and by the vac system. Even when one of his lines cracked and he limped home with his 5er, he still swears by it. He also replaced his vac pump when he got the chip, 'cause his was making a rattling noise. It's been fine since.

He doesn't have more power than me, he doesn't get better mileage than me, but he swears by it. For the most part, reliability hasn't been an option.

Despite being no better than his system, I swear by my TM. It has no extra moving parts, doesn't suck up any extra HP or have any wear factor. It's simple and reliable.

So we're both happy. He likes his, I like mine. We both defend each other's right to have their system, but both recommend what we have and like :D

Gotta love freedom of speech, eh?
 
I have never heard Heath say the Vac system is good. IN fact he doesn't like it at all. Kennedy is the one who supports it with his tune. I just chucked mine and put a TM on,. Wayyyy better.
 
Those who have replaced a faulty (for whatever reason) OE controlled waste gate with the spring, well, they think they died and gone to Heaven. They'd be equally impressed if they corrected the fault in the vac system.

However, far less moving parts with a spring, no more worry about vac pump, solenoid, etc. failing, though they are removing the factory protection the (yes, somewhat complicated, and somewhat conservative system) provides.

The OE system generally provides trouble free service for ~150,000 miles, but YMMV...

I recall early on gmctd had a concern about wastegate component wear with the spring, as it is constantly flapping to relieve boost, that's the chatter you may hear buzzing under hood, he stuck with the boost fooled, vac actuated system...

We're starting to see a few examples of that now on these forums, though very few, so probably not of great concern.

When the 6.5 first hit the road, those using for towing were quickly looking for more boost than GM programmed, and a boost fooler was invented over at the Page, John Kennedy sells a variable plug and play version, which works fine to this day.

The pre-94 6.5 turbo diesel had a similar arrangement to the Heath spring, except was dampened so as to not chatter.

A spring is a good solution for those without the wherewithal to diagnose and maintain a GM designed digitally controlled waste gate.

Only my observations, but I'm sticking with my vac system, quite happy with it, and so far it seems have competent enough to maintain it.
 
Please gents, let's not polarize on either sides of an argument here. There isn't supposed to be an argument at all.

The benefits of the TM are well discussed in other threads and a know quantity. I'd like to fully explore the factory system before I "rip it off and chuck it in the skip".

This thread is intended to discuss the factory vacuum system. It's benefits, it's drawbacks and tweaking it.

Please try to keep on track.

:)

(good input CHB)
 
OK ,IMO the vac system works fine as long as every thing associated is up to par and if the truck is only used to get groceries or haul the dog to the vet.

There is a vacpump,waste gate actuator,vac lines and solenoids involved,all of them subject to failure(usually far from any service center) at any time and resulting in extra costs and downtime.

Plus the vac system dont provide the boost when one realy needs it.

A TM gets rid of the whole vac shebang and is fool proof,what more can one ask.
 
great white said:
Please gents, let's not polarize on either sides of an argument here. There isn't supposed to be an argument at all.

The benefits of the TM are well discussed in other threads and a know quantity. I'd like to fully explore the factory system before I "rip it off and chuck it in the skip".

This thread is intended to discuss the factory vacuum system. It's benefits, it's drawbacks and tweaking it.

Please try to keep on track.

:)

(good input CHB)
Click to expand...



I had a similar decision to make when my vac pump died and my feedback on the DP forum was similar get the turbo master. I really wanted to but... when you factored the Heath's kit it was round $500 to do it right and replacing my vac pump was only $130. So the benefit for me was purely a financial one. The last two posts in the thread below pretty much sums up the options I explored and why I stayed stock... for now.

http://www.dieselplace.com/forum/showthread.php?t=301066&page=2

hope this helps
 
Status
Not open for further replies.
Back
Top