Monty

Bobs quote: &quot;The early ones would at times suffer from &quot;air separation&quot; at higher levels of boost. (that's just my somewhat &quot;old timers memory though)&quot;<br><br>I think I may be experiencing what you describe. Driving down the road no matter what gear, I can decelerate somewhat and the exhaust makes a fluttering noise. Kind of like a jake brake in a class 8, but not as harsh or loud. This has been going on for over a year now and even before the POD's were in. The amount of boost does not have any effect on whether or not it does it. It seems more pronounced at lower speeds, say 2nd and 3rd gear. Anyone else experience this symptom?<br>

Redleg

Ever since I had the turbo overhauld w/16cm housing, I get a loud woosh if I let up quick while accelerating. Mostly at low and mid range. I figured this may be a week version of the &quot;bark&quot; people describe with the other turbos. I do have a split in the exhaust right where the clamp holds the down tube, but that was there before the rebuild. I just figured the thing had too much slop previously for this to occur, haven't had any pros listen for their opinion yet. Boost jumps right to 25, power seems to be there, though I've never driven any other CTD's. Never really heard anything resembling a flutter. Wonder if that would apply to the 21 cm turbos. I know you guys changed the housing's, but maybe there was some other discrepency from the vendor. Shoot I have two different size/ color tint of floor tile bought off the same shelf at Home Depot, with matching name and stock number. Didn't notice the difference til I was trying to figure out why the lines were deviating. :.

Monty

Try to give yall a better explanation here<br><br>Going down the road at 40mph in 4th gear, you completely take your foot off of the pedal to decelerate. After your foot is off foor a couple seconds, put it back on and try to maintain a steady speed. This is when it does it. I have no idea what is causing it. But it will only do it when you have decelerated to a certain extent and then kept a steady pressure on the foot pedal.

Redleg

I'll try that a little on the way home. I have a 16cm housing as well, but stock exhaust to the muffler.

Jbolt001

My H1C did the same thing. I wondered if the compressor wheel was in a stalled state, engine taking in more air than the compressor is putting out (if thats possible). It started with the 16cm housing change but before the PODs. After the PODs and my tranny upgrade it barked anytime I let off the throttle so I picked up a used HX35. No problems since.

wannadiesel

Monty, now you've got my truck doing it. :'( Mine will make the noise you're describing in the lower to middle part of 4th and 5th gear under medium throttle. It's not loud enough to hear with the windows down, the straight pipe drowns it out. Can you hear yours over the stacks, or do you have to have the windows rolled up?

Monty

Yes, I can hear mine with the windows rolled up with the stacks. I posted this concern in the high perf section. And if I remember correctly, DonM said that it is the engine needing a certain amount of air that the turbo cant deliver. Which seems logical since it only happens when I let off of it and only keep my foot slightly on the pedal and when the boost is low.

Alec

If the engine &quot;needed air that the trubo can't deliver&quot; it would draw a vacuum in the intake manifold -- or conversly, that state would be happening all of the time when the smoke started to billow as you fella's tried to squeak a few more ponies out.

Do you get a fluctuation in your manifold pressure during this condition, or does the pressure stay steady?

Thanks,

Alec

Lil Dog

I have the fluttering too, but I get it under accelleration as well..

Scenerio is if I am at too low Rpm.. 6% grade trailer on and get caught behind slow truck.. Down to 1500 Rpm in 5th and goose it to get out and pass. It will go to 15 psi boost and then start to flutter until up to 1800, then the boost reaches 19 psi and the flutter goes away.

Also going empty through town if I am in 4th and boost it hard over 15 psi on accel and let off the throttle, I get the flutter as the turbo spools down.

The flutter in my case is that the turbo is outside of its performance map. Too much compression ratio at low turbine speed. I thought that maybe the 16 cm housings would fix that as the turbo would be spinning faster at low speeds, but it seems you guys have the same problems. It must be the compressor side that is not up to snuff..

J-eh

Alec

Okay J-eh -- This sounds like my problem exactly. I pretty much ONLY get it under acceleration. From say 1300 rpm up to 17 or 1800. What housing do you have? The 18 still? I never had this problem until I switched to the 12 . . . don't tell me I need to shell out $$ for an hx35 . . . or would that even solve the problem? I have seen ads for hx35's with extended maps (some sort of slots in the compresor housing) -- is this to combat this problem?

Where can I get some good info on understanding the performance maps on these turbos?

Well -- I just found this UnderstandingCompressorMaps which seems to be helping a lot . . . Even if the site is dedicated to a slightly different animal from our vehicles . . .


Thanks,

Alec

wannadiesel

If anyone wants to chuck parts at it, I found a company selling upgraded pinwheel/compressor housing combos. Just follow the &quot;Diesel Performance&quot; links http://www.htturbo.com/ , sounds like a poor man's HX35/40 hybrid.

Alec

Okay -- does anyone have a map for the H1C and the Hx35 and the Hx35MWE?

Based on the crude digram for the hx35 that is in the current Holset literature I found on their site, I would be right on the edge of the surge limit for a 35, so I guess I really am over it on the H1 . . .

Thanks all for your help, especially you J-eh.

Alec

Lil Dog

No thanks required...LOL

I've been battling this for a while and Yes I have the stock 18cm housing.

My buddy has a PSD and a Grand National both not stock.. So we have been toying with turbo maps for a while to see whats actually going on.

If you go to the GNTTYPE website they have bundles of good technical info on turbos and maps. Go to the resources tab and pull up technical info. But it sounds like you have basically the same info.

I think we are getting outside our compressor efficiency maps and surging the turbos. These engines weren't expecting what we are throwing at em..

FWIW I sometimes see this happen in my line of work if an improper turbocharger gets installed on a certain engine or is improperly rebuilt with the correct wheel etc...


J-eh

wannadiesel

Lil Dog-
As you seem to have experience with this, do you think a bigger compressor section could be the fix? The link I posted above says they want $200 for the pieces, which is a lot cheaper than a PDR HX35. They have 2 different upgrades, a 58 and a 60 mm, vs. the stock 56 mm.

Lil Dog

I was just reading through that while you posted.

Ya know, that looks like a pretty good upgrade for us sluggers instead of the whole turbo. They look like they know their stuff on the site, but it would be good to email them or call them to see if they are tested to handle the boost you are running.

I think this would definitely be worth checking out. The compressor upgrade seems like the logical upgrade for most of us. We all get caught up on the exhaust side of the fence, the compressor is important too...

Good Find!!!

J-eh