If I let it bog, the boost pressure gets in that 12-15# range and it will surge/stall pretty good. So if it's a long grade I'll let it downshift and then the boost goes up, EGTs come down, surge goes away and if I'm not careful I'll actually gain speed! But seriously, with the AIS box I do notice it reduced this. Now I do admit some of my observation with this is probably because the AIS box is quieter so I'm not hearing it as clearly, but I can feel it is cleaned up too. So a little of both.

 

That's not where I was going to go. I was scratching my head trying to figure out why it happens with the 6637 and not with the stock filter. A filter change alone should not do that unless their flow characteristics are indeed drastically different. The engine does not know what filter is on there except to measure the air via sensors.

So I am wondering what is going on here with the barking and MPG differences.

 

Double post, sorry

 

The problem is contrary to Gene's math the stock air box IS the restriction so when you remove the major restriction the turbo can pull more air and produce more boost which can lead to turbo surge situations which causes you to have to back off the throttle slightly. where as with the stock box the turbo was prevented from producing enough to actually cause the surge issue.

 

Is that it? Or is the hot air being ingested? I make just as much boost as I ever did, the 6637 didn't really affect that IIRC. I'm constantly tripping the overboost code without even trying on my 80E tune.

 

I'm not trolling. The mpg increase is just under 1.5mpg and after the filter swap, it won't pull that grade.

On shifts at lower rpms when I'm getting on it, the turbo will make noise when I shift. When I'm getting on it and let it wind up above 2200rpms, the turbo doesn't make any noise during a shift.

Is the van turbo a ball bearing turbo? A local guy here said to stop messing around and get a ball bearing turbo. I don't listen to him much because he melted one turbo and had catastrophic tranny failure while throwing chips in his motor.

 

I was talking to to mechelement.

I was thinking what Monster was below, but I honestly didn't want to say it since I'm sure there'd be a long diatribe full of formulas why that can't possibly be right.

See above.... LOL

...or it could be that there's more air available like Monster's saying. Also could be that it was doing it to a lesser extent before, but because of the stock box muffling it, it couldn't be heard. Now, with the open element & more air, it can happen and be heard much easier. And that's why I like hearing my turbo -- if something's happening, I'll hear it easier than someone with the intake muffled.

 

So it IS happening during shifts and NOT while you're on the pedal? That is a much less severe issue than surge while trying to make power. Real "Surge" is when the turbo stalls when you're trying to make boost. If it's just "barking" or "breathing like Darth Vader" when you shift, it's not a big deal at all.

Sorry for the troll comment -- I was expecting it after the latest round of posts.

The van turbo is a stock turbo, with a 1.15 A/R exhaust housing. The larger exhaust housing reduces drive/back pressure substantially. That makes it really laggy with stock tuning, but it favors the top end and larger injectors.

 

The turbo sputters out/surges when trying to pull a 7% grade going 65mph which is under the 2200rpm+ range I've been told to stay in. But before the 6637 mod, it didn't do that.

Does your van turbo complement a DP tuner?

 

Okay, you're surging. Need to either down-shift to keep the RPMs up, or install one of the fixes. On my truck, 65 MPH = ~1800 RPMs, right where the stock turbo likes to surge. The Wicked Wheel or ATS housing *WILL* fix that.

The van turbo does complement tuning for a couple reasons. The stocker has a pretty small housing which compliments stock tuning -- it spools faster, which is good when stock. The larger housing REALLY lags running stock, but with tuning, a lot of fuel can be thrown at it minimizing the problem. It also lowers the drive pressures substantially, which decreases EGTs and surge problems. That means at the upper end, the turbo housing becomes less of a restriction. Before, my EGTs would spike over 1500 when really nailing it. Now, I barely get over 1300, and that's REALLY hammering it....

Basically, the van turbo lowers EGT & drive pressure, and opens up the possibility of going with larger injectors. However, you can get a 1.0 exhaust housing which does much of what I described, and is better with stock injectors. I'm basically running out of fuel with mine. There's more there, but I don't have enough fuel to push it.

EDIT: BTW, not sure why someone would tell you to keep it under 2200. If you're pulling up a hill, you'll need to bring the RPMs *UP* to keep surge from happening!

 

Ahhh. Good deal. I'm not sure what a 1.0 exhaust housing is.

I meant that I've been told to stay in the 2200+ rpm range when pulling that grade.

 

There are three exhaust housings for our turbos. The number is a ratio describing the size of the housing. On our trucks, the stock housing is .84 A/R ratio. It's pretty small, honestly. The 1.0 housing is an option, and is good if you just want to go with tuning and keep your stock injectors. The 1.15 is big, and is good if you want to go with larger injectors to take advantage of it. The reason they put it on the vans is because vans have no I/C. The larger housing while more laggy, decreases EGTs. Without an I/C, the EGTs would get waaaay up there on the van with if they went with a smaller housing.

Here is what the number means in terms of housing size:


And here is some good reading on how turbos work:
TurboByGarrett.com - Turbo Tech101
TurboByGarrett.com - Turbo Tech102
TurboByGarrett.com - Turbo Tech103

 

Since the subject of comparing HP from dyno runs using a "cold air intake" versus an "open element intake" has been raised by "Izzy" here's a good link to read on the general subject of dynos and if you do you'll see that comparing HP results between dyno runs and trying to draw meaningful conclusions is a complicated process that must be done with care! Summary of dyno operation... Bishop's Performance - Dyno Info ...

" Ideally, every dyno pull would be done under identical atmospheric conditions. This is seldom the case, so a power correction factor (CF) is applied to a measured power reading to compensate for changes in barometric pressure, temperature, and humidity. It is important to remember however that a CF is only intended to compensate for small atmospheric differences and doesn’t correct for other factors, such as engine and oil temperatures." ..."Correction factors assist in the comparison of these measurements under various test conditions, making computer hardware and software necessary to obtain, interpret, and display the data."

Before proceeding the astute reader has probably recognized that the link I gave is to a "motorcycle" dyno site so why didn't I give a link to a "diesel" dyno site instead??? Well you'll have to read some of the links I gave at the beginning of my post #10 here... Confused about HP vs TQ, and what a dyno measures?... HP, TQ, Dynos, a new beginning... - TheDieselGarage.com ...to see a more complete answer but the short version is that in general "motorcycle sites" demonstrate a much better knowledge of the "Physics" involved in dynos and internal combustion engines than "diesel sites" do!!! Yes this is a sad but true fact that I'm trying to rectify!

In the following quotes everyone and especially "Izzy" please note...

"Correction Factors are used to compensate engine horsepower measurements for differences in operating conditions during engine testing. The typical correction factor (CF) is calculated based on the absolute barometric pressure, air temperature and water content of the air used for combustion by the engine under test. It attempts to predict the horsepower that would be developed if the engine were tested at sea level under standard pressure and temperature conditions."

"Air temperature is the temperature of the air entering the intake system of the engine under test. In some cases this is ambient air temperature, but in other cases the intake air is significantly heated by the engine and is different than ambient air. Heat tends to spread air molecules apart. So as temperature increases, there are less molecules in a liter of air and less air is swallowed during the intake stroke."

...the parts about... "temperature ...of the air used for combustion by the engine under test" ...in the first quote and the part about... "but in other cases the intake air is significantly heated by the engine and is different than ambient air" in the second quote ... because this is the key feature that determines the difference in dyno run HP when testing a "cold air intake" versus an "open element intake"!

In my previous post on this thread I've already given the evidence that air filter restriction doesn't effect dyno run HP so now I'm investigating mechanism #2) provide a lower air filter intake air temperature, which is what a "cold air intake" does compared to an "open element intake"!

"Dynojet’s WinPEP (Performance Evaluation Program for Windows 95) software uses the SAE’s latest correction formula (June 1990) ...The formula used is: CF=(1.18)x{(29.22)/(Bdo)}x{(To+460)/(537)}-(0.18) ...Where: Bdo=Dry ambient absolute barometric pressure and To=Intake air temperature in degrees F."

Now everyone and especially "Izzy" please note that the above equation for how the hotter air... "To=Intake air temperature in degrees F" ...from an "open element intake" degrades measured dyno run HP isn't some "witchcraft equation" that's been conjured up from one of my "computer models" but rather it's the equation used in "Dynojet’s WinPEP software" which determines the corrected output graph of dyno run HP!!!

If you plug the standard reference barometric pressure of Bdo=29.22" Hg into the Dynojet CF equation you get... CF=(1.18)x{(To+460)/(537)}-(0.18). Now let's do a "thought experiment" dyno run comparison "with the hood closed" between a "cold air intake" which ingests 70 F ambient air so that To=70 F and an "open element intake" which ingests hotter 115 F air from the engine compartment so that To=115 F.

Ok so where did I get the To=115 F for the "open element intake"??? I got it from this thread... TheDieselStop.Com Forums: TYMAR CFM ? Dale I ? ...and it's a direct quote from Dale Isley who's the vendor for the Tymar intake. In a post about half way down the thread Dale states... "...Sitting and idling the max tested was about 45 degrees over ambient..." so you add 45 F to the 70 F ambient for the "cold air intake" and that gives To=115 F for the "open element intake"!

So the baseline CF for the "cold air intake" is ...CF=(1.18)x{(To+460)/(537)}-(0.18)=(1.18)x{(70+460)/(537)}-(0.18)=(1.18)x{(0.978)}-(0.18)=0.985 ...and the baseline CF for the "open element intake" is ...CF=(1.18)x{(115+460)/(537)}-(0.18)=(1.18)x{(115+460)/(537)}-(0.18)=(1.18)x{(1.071)}-(0.18)=1.084 and this means that since the ratio {(1.084)/(0.985)}=1.101 the "cold air intake" is expected to produce 10.1% more dyno run HP than the "open element intake" produces!!!

Now in that same post Dale also says... "...Although hot engine compartment air does affect density, diesels do not burn to an air/fuel mixture and turbo's can produce density by compressing more. The theory behind the open elements is to lower the intake restriction to a point where the addition compression makes up for the loss in density..."

...so guess what folks "Izzy", "Pocket" and others have been accusing me of employing false "theories" to prove that a "cold air intake" produces more HP than an "open element intake" produces and all along the notion that Dale's 6637 is a better choice than a "cold air intake" is based on his "theory" that "open elements ...lower the intake restriction to a point where the addition compression makes up for the loss in density..."!!!

Since I've already shown in this thread that "air filter restriction doesn't effect dyno run HP" and in other threads I've shown that a turbo and an intercooler "can't undo the adverse effects of ingesting hotter intake air" I'll borrow one of "Izzy's" favorite words and just say that Dale's "theory" is pure 100% BS!!!

 

Yeah, pay attention Izzy! I have some work to do before I jump in the beer can, I will check back later.

 

I'm not reading that. Sorry. I've had it up to "here"...

Took a Vic for my sore back and maybe a Corona later. Or two.