21cm HX35, lost boost???

NickTF

NickTF

Single turbo turd.
Joined
Jun 4, 2007
Messages
5,887
Last night I managed to put in the new 5 x .016" injectors and the 21 cm exhaust housing on my hx35 replacing my stock 12cm waste gated housing. I've sense gone from 35ish psi to 27ish psi. I'm confused since i've added larger injectors (previously had 5 x .014" injectors) and went to the non waste gated housing. Has anyone out there run a 21cm turbine housing on their hx35 with any success? I understand there are success stories with the 18.5cm housing but does the few extra centimeters make that much difference?

Until I get an exhaust spacer for the exhaust neck of the turbine housing my down pipe is snug up agains the frame which does release a bit of black smoke during quick blips of the throttle. Being that's after the turbine housing though I don't think that would cause the loss of boost. I do intend to fix it via a spacer when I get around to it.

Also, going to replace a suspect clamp fastening the boot to the intake that bolts to the head but I was able to hit 35psi with it before so I don't think it's the problem.
 
21cm is a huge laggy housing. Not going going to make as much boost from what I understand.
 
haloman said:
21cm is a huge laggy housing. Not going going to make as much boost from what I understand.
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I figured it would lag more then stock but also figured I had enough fuel where the reduction in backpressure may be advantageous until I can afford a new turbo. Thus far it looks as if I was wrong but want to make sure before I swap back on the stock waste gated 12cm housing or try to find a 18.5.
 
Is this something to do with not having an AFC arm in the pump (gutted the AFC)??? If so i'm all ears on AFC replacement and tuning! Judging by the amount of smoke and my idle pre-injection pump fuel pressure of 25psi and 30psi above 1000rpm (measured at fuel canister) I'm guessing it's not a lack of fuel.

p.s. I was able to hit 35ish psi with the 12cm wastegated housing also not having the AFC arm in just to clarify.
 
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Smokem said:
You will see a loss of boost pressure when enlarging the AR ratio, I think you should be seeing more boost pressure than 27psi however.
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It doesn't feel strong either Weston, definitely feels like it lost power.
 
Since you don't have an AFC we can assume your rolling into the throttle slowly to simulate the AFC right?

You might have better luck going half throttle, then waiting for the boost to stop rising before you roll into it and put it to the floor. If that doesn't work its probably not an AFC/overfueling issue
 
dual k20s said:
Since you don't have an AFC we can assume your rolling into the throttle slowly to simulate the AFC right?

You might have better luck going half throttle, then waiting for the boost to stop rising before you roll into it and put it to the floor. If that doesn't work its probably not an AFC/overfueling issue
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That's exactly how I drive it since I don't have the AFC in there and it's still not coming up on boost equivalent to the other housing. I'm going to swap clamps tomorrow (when it arrives from dodge dealer) but I don't think that's the problem.
 
When I went to the 16cm housing from stock I lost boost all across the board but gained a little at the top because of the lack of wastegate. Yours should be the similar, but you might not gain any pressure with that big a housing

27 psi Seems low though, I expected 35-40 :what:
 
dual k20s said:
When I went to the 16cm housing from stock I lost boost all across the board but gained a little at the top because of the lack of wastegate. Yours should be the similar, but you might not gain any pressure with that big a housing

27 psi Seems low though, I expected 35-40 :what:
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Exactly my thoughts, I would have expected those kind of boost pressures too considering there is no waste gate on this 21cm housing:what:
 
Anyone have any ideas? I'm dying to know what's going on with this truck!
 
I agree with everyone else, while that 21cm might drop some boost I would think 27 psi is a bit low. You did both the housing and injectors at the same time I guess?
 
B18B1LS1 said:
I agree with everyone else, while that 21cm might drop some boost I would think 27 psi is a bit low. You did both the housing and injectors at the same time I guess?
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Yep, both at the same time!
 
NickTF said:
Like a solid black cloud is coming out, very thick!
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Unlless the spray pattern or pop pressure is significantly diferent with your new injectors, you'll be needing an 18.5 housing. go back to your 14 for now...it should haul azz, but watch for goofy EGT's.
Mine ran decent w/ a 21, but better w/ the 18.
I was on Marine 370's & a bunch of timing . 45psi is all I ever managed to get out of my 35/18.
 
My buddies '92 VE pumped truck ran 32 psi with just basic free mods and a 21cm housing. I believe the heads dont flow quite as well on a 1st gen but it was only a little VE pump! I would think your truck would at least match those numbers? Weird.

FWIW my 35/18 would only turn 40 psi
 
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Thanks for all the suggestions. I don't know how different these 5 x 16 injectors are vs. the 5 x 14 injectors I had, both came from Weston so I doubt that they are that different accept for normal items.

That kind of bothers me that a 1st gen was able to obtain that boost with much less in mods, my truck's a fueling animal so far as my educated guess can muster. Now granted if the heads of the 1st gen do flow significantly less then the 2nd gen that would explain higher boost but who knows for sure.

In any event i'm not really that happy with this 21 cm housing so I may swap back on my stock housing to see what happens.
 
sounds like something's up... I was able to get over 40psi out of my last 215 truck with stock injectors, custom plate, and AFC mods with an HX35 with an 18.5 on it. I can't imagine a 21cm housing would drop boost that dramaticly. ESPECIALLY with such big injectors
 
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