k14 highway psi

[lilpig88]

something interesting to note:
Maybe it's my imagination as the seat of the pants isn't always the best gauge, but on my way home from work for the last 5 miles or so b/4 getting off I-90, I thought the car was cruising along with less effort than before (around 70 mph or so).  I looked at my boost gauge and saw a mere 4-5 psi and realized the screw that I had plugging the LDA end of my boost line (I had disconnected the LDA for my trip home for another experiment) had come out.  It goes without saying, but just for clarity the manifold pressure was leaking out of the open small LDA hose.  Maybe it's nothing, but maybe it's something...figured I'd mention it.

[R.O.R-2.0]

something interesting to note:
Maybe it's my imagination as the seat of the pants isn't always the best gauge, but on my way home from work for the last 5 miles or so b/4 getting off I-90, I thought the car was cruising along with less effort than before (around 70 mph or so).  I looked at my boost gauge and saw a mere 4-5 psi and realized the screw that I had plugging the LDA end of my boost line (I had disconnected the LDA for my trip home for another experiment) had come out.  It goes without saying, but just for clarity the manifold pressure was leaking out of the open small LDA hose.  Maybe it's nothing, but maybe it's something...figured I'd mention it.

usually, its easier to cruise down the road with 1-2 psi, or even no boost, rather than a considerable amount of boost (4-5psi)

back in the day, when i build my first diesel, i found that i made more power at 15psi, than at 35psi, just because i didnt have the fueling to support 35psi, but i had a turbo capable of producing it..

anyways, you CAN make more power with less boost alot of the times. there is kinda a magic number as far as boost goes. you gotta find the sweet spot tho. my car makes the most power with a good amount of fuel, and about 22psi boost (intercooled)..

[lilpig88]

Thanks.  I completely agree with you but am really curious as to the best way to achieve this.  As I originally posted, I'd love to get my cruising boost down (if that's possible) and am trying to learn how to attain that...Letting manifold pressure leak is not the answer

[vanbcguy]

Where's your boost gauge connected?  Is it 'teed' in to your LDA line? 

Advance is probably the biggest variable to fuel economy really.  If your pump has low internal pressure and isn't getting much dynamic advance, by 3K RPM you'd be running pretty retarded.  Retarded timing = increased EGTs / more boost.

Assuming all the driveline stuff (brakes/alignment/wheel bearings) are fine, checking on the pump internal pressure would be the next place I'd focus my attention.

[R.O.R-2.0]

Thanks.  I completely agree with you but am really curious as to the best way to achieve this.  As I originally posted, I'd love to get my cruising boost down (if that's possible) and am trying to learn how to attain that...Letting manifold pressure leak is not the answer

you could use an air switch, and set your wastegate low, so it opens at like 4-5 psi, hook up one side of the air valve to the wastegate, and not LDA.. then hook the other side of the valve to a boost controller set to a higher psi, say 10-12psi, and hook up the LDA o that side also. then when the switch is off, you have low boost, and no LDA.. when you switch it on, and use the other circuit, the LDA operates, and the boost controller holds the wastegate closed till 10-12psi..

and check your timing, because as was mentioned, retarded timing makes your boost and EGTs go THRU THE ROOF..

[lilpig88]

Thanks.
I'd been thinking about doing that (checking internal pressure) but have to do a little searching as to the best/simplest way to do it well.  I'll do some searching and see what I can find as far as internal pressure.  Or maybe when it warms up a bit I'll swap a different pump (a good one sitting on the shelf) on to see how/if that changes anything.
Thanks again.

[BlueMule]

         
________________________________________

“I'm looking for, like everyone, the best combo of power and efficiency so after a recent re-ring job of my '86 1.6td I threw on a good k14 I had sitting around.  I figured the higher gearing of an ACN tranny with a k14  would be a good experiment for better mileage.  However, it doesn't really seem to have helped when compared to the lower geared tranny and t3 I had on it before.”

Lil,

First, Mileage,

Some Data for you to consider.

IN 1986 the Nat’l speed limit in the US was still 55 mph, so all of the vehicles built were “geared” around this. HAHAHA geared, I kill me. So your gear ratios and “sweet spot” torque numbers would be set up for 55 in the “people’s republic of the US” at that time. This means when looking for mileage, you are possibly looking at a max around 2800 RPM for best Torque, at least that’s a VW spec.

 Oh and this little tidbit from our friends at wiki

85 mph speedometers

On September 1, 1979, in a regulation that also regulated speedometer and odometer accuracy, the National Highway Traffic Safety Administration (NHTSA) required speedometers to have special emphasis on the number 55 and a maximum speed of 85 mph (137 km/h). However, on October 22, 1981, NHTSA proposed eliminating speedometer and odometer rules because they were "unlikely to yield significant safety benefits" and "[a] highlighted '55' on a speedometer scale adds little to the information provided to the driver by a roadside speed limit sign."

So depending on your tire size your MPH may look like this in 5th gear at 3500 rpm
ACH                     78
4S, AOP, AGS       84
ACN                     84

But the Plot thickens

With your ACN and stock tires 175 70 13 “22.6” in diameter your RPMs are at 2251, well within the torque range, with a little left over for passing.

With the stock tranny, ACH I believe, you would be at 2416, still enough room for passing, but a bit higher RPM.I really don’t think that 200 rpm would have that great of an effect on your mileage.

Now if you were able to get a final drive and 5th combo that brought the RPMs down to around 2500 or less at 70 mph, you would have a whole lot better mileage at 70 than you do now. Obviously, due the pesky laws of physics you will still get better mileage with the engine at 2500 RPMs at 55, than at the same RPMs at 70. But there is no doubt that bringing the RPMs down at 70 MPH will give better mileage than if they are at 3000 – 3500.

My guess would be that if you did this mod, because of the low numerical final drive/differential, you might lack some pep in town and your 5th , because of the lower numerical gear, would, in effect become a limited O/D, only useful for cruising. Now adapting a 6 speed on the other hand, Hmmmm where is that TIG???[/color][/color]


"So here is my question:
Is it normal to run 10 psi down the highway running 65-70 mph (again, 1.6td ACN and k14)?  If so, is there a way (besides going with no LDA) to avoid dumping more fuel than i have to with such high boost?  As far as efficiency goes, is there advantage to a large turbo running slightly lower boost at cruising speeds? Maybe most importantly, is there a way to get my cruising manifold pressure down?  Some folks say they run only 5 psi boost at 70 mph with a similar setup and I can't seem to get that to happen...would love some help.  I've had a recent alignment, newer wheel bearings, good tires with full air so the car rolls fine...
Any suggestions to try will be greatly appreciated.

Thanks!"


If everything is set right, timing, fueling, the “innards” of the pump, the easiest way to control boost is, wait for it, here it comes, with a boost controller, the Ricers use them and there are even manual ones that are modestly priced. I do not recommend using a regular air pressure regulator, they do not last and if the diaphragm blows out your car might get pregnant. No doubt someone from the Great White North will pop in here and say that they are using their Girlfriends hairdryer for a turbo, running on a power inverter and a standard air tool pressure regulator for the past 5 years eh with no problems eh. All I can say to that is “Hose off you hoser”

http://www.youtube.com/watch?v=GLsyM2Crhew

As far as your Turbo, you can see the Map here, but you will have to convert from US to Metric, I did this for my little T2, it was not that hard, and then you can actually plot it. Just something nice to know.

http://www.not2fast.com/turbo/maps/

As to why the high pressure, my guess is some kind of wastegate weirdness, in automotive repair always check the simplest thing first. How did you check the wastegate, if you moved it manually and it did not stick, well that would be the first step. The second step would be to apply air pressure to the wastegate and see how it reacts, even better would be to apply pressure, then use a cutoff valve and make sure the pressure stays in the wastegate can and does not leak out a porous, or cracked diaphragm, “pesky diaphragm again”. It’s possible that you are only getting partial opening due to an internal leak.

Anyway, if I missed something sorry, I’m old. And just Kidding with Our Brothers In The Great White North

Blue Mule

[Mark(The Miser)UK]

As Van says your pumps characteristics may not be correct for the 1.05 setting. Retarded is your symptoms. Simply advance the pump and take a trip up the road.

Simple to add a gauge for internal pressure check. Modify  spare output bolt, and use a thin extra banjo. Keyword search for other methods.

[R.O.R-2.0]

and just so you guys know, the LDA will be rockin and rollin by 10psi usually.. like well up its ramp.