Can someone please explain "turbo surge" to me?

[MMiller]

No.

Wow, that was right to the point... . :-laf

You need to spend some time on the phone with Paul @ HTT.



Yes, John has a manual transmission in his 1993 W 250. He installed the HTT upgrade onto his OEM unit. It consisted of nothing more than comp. housing and a 60mm comp. wheel. He simply bolted it on. Nothing more.



Told me it surges when pulling a loaded trailer over hill & dale in WV. The boost needle bounces. I believe it was a cheap upgrade. I'd opt for the higher flow 60mm wheel along with a balance. Then again, it may be nothing more than the fact he had, at that time, a non-gated 14 exhaust housing. It could have added to the problem.

Thats why I have been dragging my feet on a 16 housing, I feel I am driving my turbo plenty hard with the big housing, a smaller exhaust housing won't probably help me. Heck, I'm already at 30# boost, on cooler days it gets upwards of 33. I really think(maybe I'm off base) that if I make the exhaust housing any smaller, my pryo will go up more, and surging will get worse because I will drive the turbo harder. I'm still not wanting a gated housing, I know how my dad's newer truck falls off lots quicker then mine.



I guess I just need to talk to HTT to get some more information.



Michael

 

[dpuckett]

My 91 did fine towing with a 18 cm housing. I also had a PDR HX35, so that is an apples to oranges comparison to a degree. I think with some porting, you could flow as well as a stock unported 16, and keep your top end flow.



Another thing to consider about the power falling off is how the pump is set up. If your dad's 95 falls off quickly, it may just be due to stock RPMs, and your increased fuelling higher up the RPM band.



Good discussion, guys; keep it up.



DP

 

[MMiller]

Another thing to consider about the power falling off is how the pump is set up. If your dad's 95 falls off quickly, it may just be due to stock RPMs, and your increased fuelling higher up the RPM band.







DP

Even when my first gen was stock, and so was dad's 95, there was as noticable difference in performance. Dad's 95 is a little quicker down low, but quicker to fall on its face as rpms increase. I've always accounted that to the 'gated turbo, quicker boost on down low, and dumping it as rpms/flow comes up.



Michael

 

[CSchafer]

There are ways of tuning the waste gate. You can make a wastegated housing non wastgated in a hurry :-laf . If the truck dies out and it is because of the wastegate a boost elbow can fix that problem.



Micheal, when does your truck surge? When you let off the go pedal too quick? I don't think a housing would hurt you much at all. The turbo is very safe at 35lbs and your egt's wont be effected that much with a 16 housing. But to really get your egt's down and spool better you are gonna have to spend some money. I love my htb2, spools good will be even better with some injectors, and it cools awsome. I can drive it as hard as I want for as long as I want and it wont hit 1000 deg. Could hit 1500 with the baby h1c if I tried. This is unloaded of course. It barkes pretty good if I let off to fast though.

 

[bmoeller]

Even when my first gen was stock, and so was dad's 95, there was as noticable difference in performance. Dad's 95 is a little quicker down low, but quicker to fall on its face as rpms increase. I've always accounted that to the 'gated turbo, quicker boost on down low, and dumping it as rpms/flow comes up.



Michael

Michael, does your dad have the stock governor springs still in the pump? If he does, that is his biggest problem. It is defueling earlier than yours. Probably around 22-2300 RPMs. Looking at the curve on my dyno sheet, I'm defueling hard at 2400 RPMs. Need a 3k GSK.



Also, may need an adjustable elbow or j-hook the wastegate.



Does he still use a stock fuel plate? The stockers suck. Grind it into a #10, and it will do better.



If my stock turbo had good bearings, I'd let you try it out on your truck. Or, I'll sell it cheap enough as a core, so you can rebuild it, and be worth the money if you don't like it. Was thinking of saving it for the top turbo in a set of twins, but I don't think I'll go there, yet.

 

[MMiller]

Cade, yes my turbo does it when I let off the pedal from full boost, that doesn't bother me, I can drive around that, and besides most manual trucks can probably do that stock anyways, just can't hear it with full air intake. When I am loaded, I take off, and if I don't wind the engine up almost until the governor for a shift, my turbo will surge, boost gauge will jump, and it makes a bunch of noise. That's not even something I worry too much about, I just let the old cummins wind, shift, and get into it again. Where it bothers me the most is when I'm heading down the road, trailer in tow, 70 mph, and I hit a hill big enough that it pulls the truck down to around 65, the turbo surges badly. Basically OD for me is useless anymore unless I can keep it above 70 mph. Then in order to keep the pyro happy, I run in 4th about 58 mph. Any faster, and the pyro gets upset, 4th gear, any slower then about 45 and it surges. The engine has plenty of grunt to keep things going, and the getrag does not mind those speeds, but at current fuel settings/hp setting the turbo surges.



I can make the turbo surge with no trailer, but I have to shift up into a high gear, slow speed, and the getrag makes a lot of noise to sureg the turbo a few times.



Basically right now when pulling the trailer, I can't use 4th at all under 45 mph, and 5th at all under about 65. I regulated to 58 mph in 4th, and about 70-73 in OD, pulling trailer. I don't have a tach, and the speeds are to the best of my memory. It will only do it over about 20 psi of boost. At my current fuel settings, I am in the 250 RWHP ball park. 2 years ago on the dyno I ran 235hp/586tq, since then I've tweaked the timing, AFE air filter/Greenleaf tube, and ground the fuel pin.



Future plans are to drop the tire size from 305/70R16, to a 32" or so tire. This will greatly lower my overall gear ratio, and I know it will help pulling trailer. I also want to get 4" exhaust and look at improving/changing the turbo. I just want to do the turbo once on this truck. There is no plans for more fuel, more turbos, etc. Just a good 250/275 RWHP towing vehicle(I'm thinking with bigger exhaust and different turbo power will come up some more ). Unless a good buddy of mine wants to sell his BD twins cheep.



Michael

 

[MMiller]

Bryan, yeah dad's truck is basically stock, but in all reality I'd thought it should have ran better stock, then mine did stock. I drove both trucks when they were new, and bone stock. Mine defuels around 2400 on the dyno too.



I'll think about your turbo. The only problem would be getting exhaust worked out for a test. First gens are different, unless of course I put a 16 housing on it.



Like I said before, I just need a good answer to solve my problems, spend the money once and be done. I guess I really need to call some turbo guys.



Michael

 

[dpuckett]

Michael, if bmoeller is talking about his stock HX35, it will bolt right up to your stock 18cm housing.



I had a late 91 that would make the boost gauge flutter a bit and make a weird noise at lower RPM; say if I hit it in 5th at 45mph. Get up to 18psi by 50-52mph, and the needle would bounce about 1-2psi. I didnt think anything of it at the time, as the 444 Cummins in the Pete I drove at the time did it too. Now, after reading this thread, I think it was surging.



Daniel

 

[MMiller]

Michael, if bmoeller is talking about his stock HX35, it will bolt right up to your stock 18cm housing.



Now, after reading this thread, I think it was surging.



Daniel

Hmm, a feller by the name of Bill brought that up to me tonight on the phone... ... ... .



When I was running stock injectors, and tweaked pump, my truck would only do it at about 55mph in od, loaded heavy. Now with the larger injectors, and more fuel, and larger tires its is more tempermental, plus since adding the AFE you can really hear it in the truck.



Michael

 

[Greenleaf]

Michael,



Am I to assume you installed that pipe assy from the school bus or was that for the other truck?

 

[MMiller]

Michael,



Am I to assume you installed that pipe assy from the school bus or was that for the other truck?

Yes, the stuff you sent is on the 93. I've done nothing to the other truck(the 90), since I put the pump back on after SOP. I need to pull the pump of the 90 and fix the key.



Michael

 

[dpuckett]

I need to pull the pump of the 90 and fix the key.

Again, or still?

 

[MMiller]

Again, or still?

Still, I just parked it after the offroad run.

 

[CSchafer]

Michael,

I've never had that particular problem with surge. I don't tow so that is probably the difference. If your planning on staying at 250 hp I think a stock unit off of a 2nd gen would be all you need. But the 12 housing would up your egt's even more. Maybe a hybrid would suit you. I think they take a little heat out and still spool well. I have a non gated 14 housing not being used. I know it's probbly not what you want but you could see if it hurts or helps your surge problem and see how much it raises you egt's. It would give you a baseline on what you want to do. Pay for shipping and you can try it out. I can get it back at sop next year or something I have another stock 2nd gen unit I'm going to pick up this week so I really don't need the housing now any way. That housing requires you to take about an inch out of your down pipe though, It's the same length as a 2nd gen housing.