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getting great boost with the vacuum

chefmike

chefmike

Not just a truck... a project.
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Location
north GA mountains.
So I got my guage on.

I am seeing higher boost numbers than I thought. I have a stock vacuum system with a new solenoid. The boost seems to increase with the petal, hard acceleration runs it up to 15 pretty easy. It sits at 6 to 9 climbing hills at 2100 rpms and seems to be very steady.

I will have it out on the interstate tomorrow, so I will be able to get a good feel for the numbers on the way to the in laws. I will get my dog to shoot video :D I am pretty sure it is dropping down at cruising speed. I should be seeing less than 2 when cruising, correct?
 
Does it maintain 15? If it does I would suspect you have a chip.

I would see spikes of 13 and it would drop off.
 
On the stock '95 we see 9 maybe 10 on spikes. 6 sustained at sea level, 9 to maybe 10 at 6000' to 7000'.
 
The updated 95 PROM in mine would spike to 13-14, but would only maintain 8 at sea level. Origanal PROM would only spike to 11, and maintain 6.5. Cruise though with the origanal PROM was 2.5-3, and updated dropped down to 1.5-2 so milage went up about 2MPG.
 
I am interested to see what I do on the interstate. It holds 8 at 2100rpm climbing this hill into town at 45... not accellerating, sustaining, having dropped from higher (12?)

It is much higher than I expected to see.

I will let you all know. It will be Friday, as I do not think my MIL has internet and I am too cheap to pay for it on my phone.

So happy thanksgiving!
 
And it maintains, as it always sets a check engine light on the one hill I will hit tonight. I guess I can finally see what it hits.
 
Doubtful it has a chip if it's setting a code...have to checked yr vacuum line routing to be sure they are hooked up correctly?

I accidentally hooked mine up to the solenoid backwards once, mega boost like that.

A good chip setup correctly for the vacuum operated boost works very well IMO & IME.
 
Or instead of a "buy it and be happy with it" chip, you could do what I did with my 98:

Craig moates RTOBDII tuner (rebranded tunercat II) for around 900 bucks shipped and then a Lyndon Westers VDF for your truck at 99 bucks and tune it yourself. Not much difference than buying EFILive for a DMax truck (costs around 900-1000) except that EFILive can't tune the 6.5 trucks.

Gives you control over nearly everything: fuel, advance, boost, transmission, DTC's, emmisions, etc, etc...

Plus, it will tune nearly any other obdII vehicle you can get (or make) a VDF for.

The learning curve is STEEP though.

Buut, I've always been a bit of a "tinkerer" also....:)
 
Last edited:
Crankme69 said:
Doubtful it has a chip if it's setting a code...have to checked yr vacuum line routing to be sure they are hooked up correctly?
Click to expand...

In relation to the bracket on the solenoid, which feeds the wastegate?

Boost somewhat follows the pedal, so backwards hookup makes sense, as I would think the pump side would increase vacuum as rpms increase.

I have 8 to 10 lbs with mild accelleration (2100 rpm on a 3.73 rear)
I hold boost of 5 to 6 lbs running level at 65 to 70. Never drops. Steady.
The boost increases with speed. It throws the code at 80 mph (code 78 I bet, but I have to go pull the codes. I just got home. Unpack, beer, few projects for the wife, then computer.

I will go take a picture. of the solenoid, maybe just try swapping them for the trip to Home Depot here in a little bit.
 
If yours is a non EGR F vehicle there will be only 1 solenoid, if it's EGR'd there will be 3 yours being a burb should just be the one solenoid, if all is good and yours is stock as you think it is, possibly the MAP sensor is bad failed high indicating more boost than you are actually getting, you would have to have a scan tool to see that though or swap sensors.

Here is a picture of vac routing on OBD-II EGR setup
 

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bottom (yellow) is running to wastegate.

And what is that connector that has nothing on it? a test port, I hope!

attachment.php
 
chefmike said:
bottom (yellow) is running to wastegate.

And what is that connector that has nothing on it? a test port, I hope!

attachment.php
Click to expand...

Yup, someone has ben mucking around in the works. I don't even see the stock attaching bracket in there.

What is vin code for your engine: "F" or "S"?

Or you can look in the glove box for the sticker and see if it says L65 or L56 in the RPO codes.

The way your boost actuator (solenoid) is, it could be hooked up backwards. But if that is true, the vacuum from the pump should just be venting to atmosphere. And looking at the actuator it seems the lines are run correctly when looking at it's attachment tab. Maybe someone has the wrong actuator on there. The boost actuator should have a green dot on the top of it if it's the right one.

What you are describing sounds like constant vacuum to the wastegate.

It's possible your boost actuator has failed and stuck in the open position, thus allowing constant vacuum to the wastegate. But, these units usually fail closed, which doesn't allow the PCM/ECM to keep the wastegate closed and it makes little boost (or none).

My 1998 6.5 with the stock PCM and stock vacuum system will drop down to around .5 lbs of boost of the highway....
 
I swapped them around for a short run: had to get a christmas tree.

I had to put the petal down hard and it hit maybe 2 or 3 lb by 3000 rpm. Was not boosting on normal starts, but no black smoke anywhere. SO it sounds like they were swapped. I bought a napa unit before I had the guage and swapped it in, so it should be right for my vin F truck.

I am going to run like this until I get my chip in. I am looking to chip and keep the vacuum for now. Obviously it CAN make some serious vacuum.

Now onto other problems... glow controller unplugged. SIGH. I guess I need to test and see if I have voltage to the glows? She starts decent at 30degrees. First time, little bit of smoke but not much. The dash light cycles a few times.
 
no dice. I finally had her out on the road today. No boost and the ses light is blinking on and off every once and a while. I will pull the codes soon. I was running at 65 mph 2200 rpm, no boost showing.

I switched the hoses back the way I had it and no codes. Still sitting at 5-6 lbs cruising at 65mph on the return trip.
 
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