Engine/Transmission (1998.5 - 2002) KSB1B - I want to lower the rpm at which boost starts to rise significantly

[rweis]

I have a KSB1B and I have to be at reasonably high rpm's (1800 +) before significant boost (10 psi +) starts to come in. I get the impression that I do not have enough exhaust drive pressure until I get to the higher rpm's to get the turbine fully spooled up.



I get the impression that I can change the size of the exhaust section to a smaller cm**2 and get faster spool up. The EGT temperatures would go up since it would have a smaller turbine cross section.



When I am at full throttle towing (13k) at the lower RPM's (less than 2000) I have PLEANTY of black smoke which leads me to think I have enough fuel, just not enough air.



What EXACTELY do I measure and WHERE to determine what my exhaust section cross section is? so I know where I am right now.



It is NOT wastegated. The maximum boost it will generate is about 20 psi and that is up around 2000 - 2400 rpm. It cruises towing (O/D out, 13k 5er) 62mph @ 2400 rpm at about 10 psi.



Ideas?, thanks in advance.



Bob Weis

 

[DHayden]

20 pounds of boost? I have a KSB1B also, mine starts building decent boost at 1400-1500rpm and is off like a shot by 1700rpm. My max boost is 42 pounds. I was going to ask about your elbow but your sig says you have a comp which comes with a new elbow so I'm somewhat at a loss.

 

[RHARVEY]

rweis,



You may be correct as far as not enough exhuast to spin it up. If you take a look at DHayden's signature he is running BDIII's compared to your DDII's. Currently my wifes's 2k has DDII's with only a PDR HX35/12wastegate housing and does just fine as far as egts. The truck was actually put together to pull a 12k 5th wheel. Even with this combination according to the guy we bought the truck from. . he had no issues with egts.

Truck was dyno'd at 353hp... There just may not be enough fuel to spin that bad boy...



Rick

 

[monkfarm]

??Fass system provides enough fuel??

Do you feel like you are getting enough fuel with the fass system hooked up?? I have a fass system that I haven't gotten around to hooking up. I'm hoping my starts the boost early. What is that "KSB1B"??

 

[tractorface]

somethin ain't right

I am far from an expert but if your smokin heavily at full throttle and only seeing the boost you reported I don't see how the setup could be working properly. Have you checked for Boost leaks, proper map sensor operation (don't assume no codes means a good sensor). Watsegate stuck open. Somethin is up. Your housing can't be big enough to cause those numbers in my opinion.

 

[PC12Driver]

What level do you have your Comp set at when you tow?



A turbo that works well for daily/empty driving may not work well and can take on a completely different personality while towing. I'm in the same boat with my Dodgezilla; it takes about 1,900 RPM to get "on" the turbo while towing. Anything under that and it's a lot of smoke and not much boost. More fuel would also spool the turbo, but when trying to maintain a constant speed while towing that isn't really an option.



A smaller exhaust housing could generate higher EGT's in the higher RPMs when the exhaust starts to get choked off. But at lower RPMs (read: normal operating range), your EGT's will probably decrease because the increased velocity through the exhaust housing will drive the compressor harder and generate more boost for a given RPM. This will bring the RPM at which your turbo lights off at down a bit lower. It's a trade-off; big compressors and housings are good for higher RPMs and/or heavy fueling, but they may not be the hot ticket for normal towing for the reasons you experienced.



Isn't there a -2 version of the KSB1B that has a smaller exhaust housing? That should pull the light-off RPM down a bit. Or a cam...

 

[Roger rodbolt]

Pressure test your system, serious boost leak. lc

 

[Cooker]

Something does not seem right. A Comp and DD2's should generate more than 20psi of boost



I would look to getting the truck "tuned" before I considered swapping exhaust housing. JMHO

 

[frijole]

Leak

You got a boost leak dude. Blowin' air out the hole instead of thru the intercooler/intake.

 

[frijole]

Leak

PS-- May also be a blown intake manifold gasket..... Air's goin' somewhere besides where it's supposed to.

 

[rweis]

Let's assume a boost leak for starters.



What's the best way to detect a boost leak? I assume you have to pressurize the intercooler system from the turbo outlet. Is there an adapter for that?, or do I improvise some sort of adapter. I have an air compressor which should be adequate to provide air.



Do you seal off the air system at the air horn where it bolts to the intake manifold? Is there an adapter for that? or do I improvise an adapter?



Then I would think you pressurize it to 20 psi or so and start looking for air leaks. Right?



Bob Weis



I'll go look up whatever proceedure there is in the SM, if there is one.

 

[DHayden]

I dont know how long your comp has been on, but you did replace your stock boost elbow right? I think the stock boost elbow is 20-21psi.

 

[PC12Driver]

He doesn't have a wastegate.

 

[rweis]

When I got the KSB1B from Kurt he said I did not need a wastegate, I would not be pushing pressures high enough with DD2's to need one.



This weekend I will look for boost leaks. I assume that I will build a adapter that I can put in low pressure air from the compressor into the piping between the turbo compressor outlet and the piping that goes into the intercooler.



Now on the other end (ie the engine end) do I need to make an adapter to block off the intake horn?, or will the cylinders and valves be sealed enough to test the intercooler piping and intercooler integrity?



It would not hurt to test the piping anyway, may not be it, but can not hurt to test it.



Bob Weis



Any idea what size of PVC pipe will fit into the intercooler rubber boot that is right after the turbo compressor outlet under the passenger side battery?

 

[PC12Driver]

I see your pump wire is not tapped. Do you tow with the box on or off?



The KSB1 is for "moderate to high" hp motors. Are 80hp injectors and an untapped Comp enough to drive the turbo properly (DHayden, what psi's do you see on level 1 or with the box off?). It would be nice to hear of some real world numbers about what he should expect (DDII/EZ/KSB1) before he starts ripping into his intercooler (from people that have actual experience... ).



I'd also start with checking the tubing between the manifold and the boost gauge and the associated fittings. I'd guess there'd be more of a chance of having a problem there than with the intercooler and boots. It would suck to tear into things if it turned out to be a simple gauge problem.



rweis, how are your exhaust temps under a load with the turbo spooled?

 

[rweis]

I tow with the box on, 1x4. Have to be very careful about the smoke at lower rpm's (<1800). I run with O/D out. Once the rpm's get over 2k then the turbo is about 10psi and it will run up to about 23 psi depending on throttle position. Once the boost gets to 10 psi it follows the throttle very well. Just a little increase in throttle will bring up the boost accordingly. Like driving with the cruise controll on and going over a overpass on the interstate.



The temps can get over 1250* if the boost is below about 8psi. Once the boost is in the 10psi range the temps run about 1000* and will slightly increase with throtle but when the boost rises accordingly the temps cool right back down. I can run it on cruise control (O/D out, 2400 rpm, 62 mph) once it gets up to 10psi and not worry about going over 1250 (here in flatland florida).



When I run empty (no RV) and push WOT it is somewhat sluggish till about 10psi (50 mph 2000 rpm O/D held out by throttle pressure) then it will go to 80 in about 3 seconds and the boost will go to 25 psi and the O/D shifts in about 75 mph and I run out of balls at 80 in a 55 zone



Bob Weis



It may be not enough fueling. I have been thinking of tapping the VP, but think it better for the VP if I do larger injectors (probably EDM 2. 0's or 2. 5"s) and not tap the VP.

 

[paulb]

Before you get too crazy with testing, do a visual inspection. One prime area on an 02 is the lower passenger side intercooler boot. The sheet metal comes very close to the boot and can cut it. The boots are really thin rubber and they blow up like ballons. Also check all the clamps and make sure they are tight.



my . 02 worth...



Paul

 

[DHayden]

He doesn't have a wastegate.

Mine is the same as his... trust me. It has an internal wastegate which is not operational. He still has a boost elbow, the stock boost elbow will only allow 20-21 pounds of boost. When I got the edge comp, it came with a new boost elbow. I understand his turbo's waste gate isnt activated, but i'm betting dollars to doughnuts he is still using his stock elbow.



The BD3's and DD2's are minimal difference, there is not a major hp difference, your DD2's should drive the B1 fine.

 

[rweis]

Well, that could be a possibility.



Where do I look? I have the Edge Comp paperwork at home and can read it when I get home from work in about 2 hours. What does the stock elbow look like? I have been over on that side of the engine quite a bit, but you often do not see the snake until you step on it. When I put the Edge Comp on I was pretty new at this.



I'll do a search for stock elbow as well. I "might" have "misplaced" the Edge elbow, what does it look like.



If this is it, then I will send you a gift certificate for dinner for two and gladly do so, or a fill up of diesel, your choice.



Bob Weis



ps later tonight: I called RIP to see what he might add. He said a KSB1B, DD2's, and an EZ (Comp on 1x4) should give about 35 # psi. So somewhere there is 15 # psi floating around.

 

[Alphacowboy]

just a hint by the way, if you are looking for leaks, when you pressurise the system, put a small amount of peppermint in there, you will be able to smell if it is leaking, and usually where it is leaking, as it is very stong smelling!





but yeah, sounds like the boost elbow.