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Poor compound performance

6K views 67 replies 16 participants last post by  Broaner 
#1 ·
I believe my compounds aren't performing well. Or my expectations are high. First off, I know my top charger is small. Too small. I can go 1400+ in 2nd gear in a high tune, and loaded heavy on stock I have to milk it up hill to keep it under 1350. But my spool up is whats most disappointing. From a stop, I don't get on top of the chargers till around 2000rpm, but once I'm rolling, they spool around 1400rpm. Both are box charger with 360 bearing upgrades. 362 (62/65/12). 475 (75/96/1.32<I think) In my defense, the set came off of a 12v I had before this truck, so the top charger is small for a CR. I believe I am also suffering from a low stall converter (1200-1300rpm) that wasn't supposed to be low stall. But spool up isn't really why I'm writing this post. But feel free to comment about it. I know I need to restall. My egt's is my concern right now. I know my back pressure is up due to the small exhaust housing. Although I have never hooked up a gauge. I can be coasting downhill at 70mph and see 5lbs of boost. lol. My mpg is suffering from it as well. Both chargers are coming off soon and going to see tator. I have messaged him about options and its pretty much whatever i want. I was thinking going t4 on top, but In a compound setup, I think a wastegated secondary would serve better. So I was thinking 62/68/14 or 63/68/14. My fuel mods are below in sig. The primary will be untouched, minus one of his billet wheels. So will the 14cm housing give me enough flow? Opinions? Also keep in mind, the cost of bumping up to a 63mm compressor will cost $450 more in machine work. Not a determining factor, but something to keep in mind.
 
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#2 ·
have you spin the turbos by hand to see if they spin easy or rub anything? you checked for boost and exhaust leaks? is there any wastegate? air filter good? also, dont waste your money on a billet wheel for your primary.
 
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#4 · (Edited)
Interested to see how this plays out.
I have the same spooling issues with the same spec turbos at high elevation (7000-10,000' I realize spool can be a bear that high) while towing.
I'm thinking its converter related in mine and have the same converter as the op......
And I wouldn't say a 62/65/12 is to small of a turbo unless your trying to get into the 800-1000 club.... Even then I think it will do it..... Might be a little hot but it could do it.
 
#5 ·
#8 ·
What size injectors and tuning are you running? You should spool a 62 just fine so you might have issues elsewhere. I wouldn't say that it's too small either.
The 1.32 housing on the primary can spool a couple hundred rpms later compared to a 1.10 housing but I don't think that is your main problem. That is close to a set up that I'm switching to and is suppose to be great all around compounds. But I'll have a 63
 
#11 ·
If you have those injectors and tuning, definitely verify you have no boost or exhaust leaks. Also verify your wastegate is set correctly.
 
#13 ·
Well, I did check the waste gate. Regulated 30 psi to a blow nozzle and the gate just barely cracked open. Cranked it up to 50, it opened up all the way. So waste gate is good. Out of curiosity I pulled the charge pipe off, and seen oil. Pulled boot off of secondary charger, I had compressor wheel/cover contact. So found my spooling issue, But primary is also hurt. No contact yet, and no in and out, but it has what i feel is excessive side to side, enough you can hear a clunk when you do it. Out of curiosity, I started the truck, let it run for a few minutes, stood outside, reached through window, shut it off, jumped around to the front of truck, and both chargers had already stopped spinning. Kind of confirming my primary is on its was out too. Now that the issue has been solved. Lets change direction back to sizing. Im pretty sure I need to be a little bigger on the exhaust side of things to help ease flow. 62/68/12cm? 62/68/14cm? Or just leave the size alone.
 
#14 ·
I am running the stock HE351 as my secondary. That's smaller then yours and i have no issues. Your secondary is not too small to run in your set up.
 
#15 ·
Well, if the secondary needs rebuilt, rebuild it. Now whether or not you go modded and buy whatever you were talked into buying or not, that's obviously up to you.

High EGT and 5lbs at 70 isn't indicative of a too-small secondary, in my opinion. I mean, I'm far from a turbo expert or guru. I think I'm probably about 5-7psi cruising at 70ish, I'd have to verify. Might even be more. I can tell you my secondary is much smaller than yours.

I think you've got issues elsewhere. That thing should be nearly lightning quick spool. Obviously a turbo that's failing and hitting the housing isn't an ideal situation for driving.
 
#16 ·
Sounds like you might have a oil feed restriction issue to those turbos man.
 
#17 ·
Possibly oil drain blockage.
 
#20 ·
Verify that your feed/drain lines are clear, then check for adequate flow. Disconnect your feed lines at turbo and start your truck. One at a time. You can remove your oil fill cap and pump the oil directly back into the engine. You should see a strong, steady flow.
 
#22 ·
I think you might like your setup much better after playing with the wastegate. Mine didn't come with a spring for this kit because it was confusing buying 2 compound kits at the same time and info was lost.

I tried a few different springs and have settled on the one I have. I also have 2 settings for that spring. At the track I loosen it up BIG time and have about 8psi more coming from my primary. On the street It's much tighter for better spool and street manners. I'm sure I could ever find a spring that is Perfect for both.

Also I think mine cracks around 15 psi on the street.

There is a couple spreadsheets floating around for setting your PR on compounds when your done. Maybe the twin guys get in here thread IIRC
 
#24 ·
No mine is a modified S300. It uses the internal S300 gate also.
I ran that turbo solo first. The spring was set at 52psi and I never moved it when solo. That was WAY too strong of a spring when I tried it in the compound bracket.

I could no way make that same spring work in compounds. This compound kit has a bracket that the spring is held and adjusted at with a reach rod going down to the S300 factory gate lever.
 
#26 · (Edited)
Yes just like all the gated s300's that numerous companies build for our trucks marketed as "drop ins" I believe there is a few that use the factory type solenoid working on boost but the tuning of primary to secondary PR procedure is the same. You may need a boost elbow or other things to tune them. If you had one of those you'd be better off to buy somebodies spring gate bracket and hardware.
 
#27 ·
If you are truly convinced the stall is low that would really change the whole scenario. Tough to get anything spooling at 1300 with 100's even with dual pumps.

Also agree some full boost numbers would help alot. And you got any rail pressure readings? And whose tuning?
 
#28 ·
Tuning is done by hardway. Back when chargers were newer, I was able to push 78psi out of them. My RP holds steady at 24-25k at wot. Signing off for the weekend. Enjoy your labor day men!!!!!
 
#29 · (Edited)
I have the same turbos, same injectors but a manual trans.

I fought high EGT's for a while and various different issues. The biggest thing I was fighting was myself not knowing what I was doing.

One thing I had trouble with was the manifold bolts loosening on 5 and 6, making an exhaust leak. I would tighten and they would be loose again after a while. Knock on wood they have held for several months...

I was also trying to run my wastegate as a spring-gate. I had a similar issue as waywardtravel, my spring is too stiff to use without pressure helping it open. Even with only a round or two holding it shut it wouldn't open far enough to get rid of some of my drive pressure. After messing around with it like this for too long I rigged up a boost gauge for my primary and then spent a lot more time messing around with the wastegate trying to balance ratios. I FINALLY jerry rigged a cheap drive pressure gauge and figured out that I needed to open the wastegate more. I hooked it up to total boost and then I had to tighten down the wastegate so tight that I didn't have enough travel left in the spring, so I hooked it to primary boost and tinkered with it till I got good ratios, AND good drive pressure.
Long story short, I could have saved myself a ton of time and frustration by rigging up the drive pressure gauge in the beginning.

My final setup I hooked it to shop air and set it to open at 15 because that's what my primary was running at. This was too loose because the drive pressure, and the primary boost are both trying to open it, but I think it was good to start that way because then all I did was tighten a little, drive and watch gauges, tighten a little more etc. until I saw the drive climb above the boost and then I loosened it back a little. Currently running 65 drive 60 boost at full throttle. Egt's are better than they ever were and it runs better than it ever did.

Sorry for being long winded... here's a pic of my gauges on the cheap, one is primary one is drive.
 
#30 ·
Have you measured drive pressure? I would tune the wastegate as stated above. The 1.15 AR turbine for the s400 will help speed the spool up, maybe help enough to forgo re-stalling your converter.
 
#31 ·
Should still have the proper stall tc though just knowing that would make my Ocd explode haha


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#32 ·
Thats why I like those insta-stall converters. You know... that type with the 3rd pedal? :stirpot:
 
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