Power gains from pump adj. vs. 16cm turbo

[Archive]

Now that I got my truck running again after turning up the pump #ad
, I was wondering how much more power I will gain with a 16cm housing on the turbo. The gain from adjusting the pump is impressive. I had max boost of 15-16lbs before and now I get 18 -19 unloaded in 5th going uphill. I am also routinely seeing 10-12lbs around town going thru 3rd and 4th gear with about 1/2 throttle. I used to get maybe 6lbs in 3rd and about 8lbs in 4th! The truck also feels much stronger down low at about 1100-1200rpm after shifting.

A few questions:

1. Will I see similar increases over and above what I've just gotten if I replace the turbo housing with a 16cm unit. (I assume I now have a 21???)

2. Can I turn the pump up more? I did 1 complete turn. Will I get even more if I turn up 1 more turn or 1/2 a turn? Is there a limit to it or will I just see diminishing returns by going farther?

3. Is it logical to think that I gained 25 to 30 horsepower with the pump adjustment since I went from 16lbs of max boost to 18 1/2 to 19lbs? Is it 10hp for every pound of max boost?

Thanks guys, I am lovin' this stuff! #ad
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Rob

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93 W250 LE, CC, 4x4, 5spd

 

[Archive]

RobM: Heres a few brief replys to your questions:
1) Yes. Your truck will love the 16cm housing compared to the 21cm. Your boost will climb quicker, and the seat of your pants will attest to it.
2) You may find you can turn the fuel screw in a little more, because of the added air/boost. Yes, there's a limit, and you'll reach it by more smoke, and no power gain.
modified injectors will take you to the next level, without over working the pump. Accurate advancing of the pump timing is recommended.
3) You may well find you have at least gained that.
You've mentioned "turning up" the fuel screw. . Did you complete the process by adjusting the AFC star wheel, rotating the diaphragm, and re-adjusting the idle screw?
If you fit up the 16cm turbo housing, You would want to take advantage of the increased boost/air by doing the adjustments.
I strongly recommend a boost/pyro gage set if you run any turned up fuel settings.
Lastly... the addition of a 16cm housing to replace a 21cm is one of the best $150. 00 investments you can do for that 12 valve engine.
Hope this helps.
Regards

 

[Archive]

Old School, Thanks for the info. I did adjust the diaphragm from 12 to 3 oclock or so but it still smokes significantly more than before the adjustment. Do I need to go farther clockwise? I haven't touched the actual star wheel though, should I? I also haven't reset the idle yet, it only raised about 100-150rpm to about 1000. This is high I know, so I'll probably try to lower it this weekend. Any tips on getting a wrench and screwdriver in there to adjust the idle?

BTW, I do have boost/pyro guages, didn't have that in my sig. when I last posted.

As impressed as I am with the newfound power of my truck, I can't imagine what fun some of you serious bombers are having with yours #ad
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Rob

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93 W250 LE, CC, 4x4, 5spd, 4. 10's, exhaust brake(tailgaters nightmare), turned up pump, boost/pyro guages, lund moon visor, weatherguard tool box.

 

[Archive]

Rob: Try adjusting the star wheel up (counterclockwise) in steps to clear the smoke.
When does it smoke? DURING ACCELERATION? (turn starwheel back up)
AT TOP OF SHIFTS? (turn diaphragm countercluckwise)
Hope this works.

 

[Archive]

RobM if your truck is a 93 your turbo housing is 18cm and you will probably not notice that much difference going to a 16cm. some people I know went from 18cm to 16cm and said they hardly noticed it. but going from a 21cm to a 16cm makes a big difference. from the kind of booste you say you are getting sounds like yours is 18cm

 

[Archive]

Don't get crazy with the fuel screw. The VE pump is not particularly capable of reliably pumping a lot more fuel.

If you need more fuel, I would suggest you change injectors. There are higher output injectors from BD, and some part numbers from Bosch and of course Cummins should know some as well.

The VE pump cam plate seems to be on the ragged edge of maximum loading now (they fail occaisionally), so really cranking the pump will only seriously overload it - and you won't get that much more fuel.

Another trick I have tried is to use the 215HP injector nozzles put in the holders from 91-up engines. The pattern seems to be right, and it does NOT smoke, even when cranked a bit. We have installed some of the freer flowing injectors, and if you crank the pump at all, it wants to smoke. In spite of that, however, they make serious performance gains.


They have to be custom built for you by an injection shop, but should not cost much more than any other injectors.


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Let's see, a tagline goes here. Something witty, perhaps? Maybe just profound? Naw. Can't think of a single thing to put here.
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Been a fuel injection tech for 13+ years. Someday, I'll actually LEARN this stuff...

 

[Archive]

RobM, -You will see a difference in the 16cm2 housing! Especially when the fuel is turned up. It might take a little more tweaking to get the desired results, but it is well worth it. I personaly have put a dozen 16cm2 housings on all year trucks. The early model trucks respond the best and the owners are the happiest. You must seriously think about getting a good after market exhaust system to really make the system work. I am getting 32psi boost out of my personal truck and seaking more.

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'89, CC, SB, 5sp, 3. 54, 16cm2 housing, maxed fuel, KN, Banks exh w/muffler, Autometer liquid filled gauges, Factory tach option, 100% Dyna-Mat, Horton fan clutch, Firestone air bags, Chrysler V-twin air comp, 2. 5" lift, Rancho Shocks, Alcoa LTS, BFG 255/85/R16 MTs (33. 3")

[This message has been edited by Stab (edited 02-11-2000). ]