1500 rpm under no load...that a nominal level of boost would be generated
Maybe depending on what you mean by nominal, yes, but nothing significant. It only takes, what, maybe a tenth of throttle capacity to redline a motor without load? So, I don't know about that. I can't get boost to register on the gauge without load.
now control separately the rack position from the air throttle position
You mean like when I got that big vacuum leak?
one could increase boost pressure by simply increasing fuel delivery while leaving the air throttle undisturbed ... up to a point (sooty exhaust).
Once again, I guess maybe. But I don't think soot will push the turbine much. And I don't think the impeller will push much air past the butterfly. I don't envision much more than tons of black smoke. Not much different than the vacuum leak. All that fuel wouldn't even make the engine run free over about 1200 rpm. Don't see how it would actually push the compressor. Maybe Zen could go out and give it a try.
Whuchu seein'?
'82 standard cab 3 axle SD22 turbo
'89 int'l 9700 Cummins 444 (855 ci)
'29 HD FD export model
philip wrote: Now control separately the rack position from the air throttle position
You mean like when I got that big vacuum leak?
philip wrote:one could increase boost pressure by simply increasing fuel delivery while leaving the air throttle undisturbed ... up to a point (sooty exhaust).
Once again, I guess maybe. But I don't think soot will push the turbine much. And I don't think the impeller will push much air past the butterfly.
With a fixed air throttle position (RPM no load), pull off the pneumatic governor apply hose and see how the engine starts racing hard ... not high enough to attain max revs but more than enough to scare you when you're not expecting it. More fuel, more heat, more cyl pressure, more exhaust output. That's why the engine will race against the nearly closed air throttle.
Is your motor back in and ready to run yet?
-Philip Passed 08May2008
My friend, you are missed . . .
1982 Datsun 720KC SD-22
The temp before and after the turbo can vary ~100°F, so I've read.
Iron is red-hot at ~1290°F. Aluminum (unalloyed) melts at ~1220°F. I think pushing above 1000 or 1050°F for very long might compromise the piston crowns and valves. A passing maneuver at higher EGT would probably be OK, but a long grade might not.
What kind of max tempertaures are you running? I have read 1250 degrees at the limit. I plan on running 10psi with a max of that temp.
You won't be able to choose quite like that. EGT won't go too high until you've got the IP putting out more than the turbo can keep up with. That's more a function of how well fit the turbo is, but I'd say that might not be til over 20 lbs. Tuned back to half, your pre turbo EGT will probably be under 1000F.
I think 1200° would be a burst temp.: intermittant duty.
Until you blow it up it's all just theory. 1200° is ok on a motor with lower compression ratio but being unwilling to pay the price to know for sure, I'd also wager that it should be just a few seconds on an SD motor.
If measuring downstream from the turbo -- rather than at an exhaust port -- subtract at least 100° from those numbers.
The usual number is 300°.
Start a thread and let's see some pictures!
'82 standard cab 3 axle SD22 turbo
'89 int'l 9700 Cummins 444 (855 ci)
'29 HD FD export model
for what its worth (sd33 with homebrew turbo set up...using original ip and intercooler) i get 1112 f (600c) going up hill no problems and it will go higher if i let it..(i dont!)..that is 60mph overtaking steep hill..at this point i am throttling back to keep temps safe..it has MUCH
turbo it
(sd33t home turbo set up if anyone is interested..)
For what its worth.i know its not a sd22 but very similar...(sd33 with homebrew turbo setup..with intercooler and standard ip with fueling up half a turn and timing advanced abit EXTERNAL air intake free flow filter..it has 5 ring pistons(i suspect)and has piston oil squirters..it is euro spec)
on proper hill 60mph 5th gear (31 tyres 3.54 diffs) 2200rpm temps will easy reach 600c (1112f) thats PRE turbo temp..it will go higher if i let it.(i dont!)
it has much more to give as well but untill the revs reach 2500+egt's keep rising dangerously..after 2500 you can sustain 70-80mph up hill ang egt will not go over 1150f(ish)
i recon i can get temps down by changing the ip to the oem turbo one,which does away with the restricitive flapper throttle assembly..cos at anything other than drag racing right foot position the flapper is almost shut,this cant help egt's!...will find out soon...is there one for the sd22??or can you make something fit??
reguarding will it blow up..instal 1yr old now.car used everyday..no problems so far.( and yes my fingers are crossed Philip..hope you are mending quick!!)
turbo it
(sd33t home turbo set up if anyone is interested..)
zen wrote:SNIP- i recon i can get temps down by changing the ip to the oem turbo one,which does away with the restricitive flapper throttle assembly..cos at anything other than drag racing right foot position the flapper is almost shut,this cant help egt's!...will find out soon...is there one for the sd22??or can you make something fit?? -SNIP-
Galen has tried positioning the turbo between the air throttle and intake manifold. At present, he's trying the turbo ahead of the throttle. The injection pump is the OEM having the pneumatic diaphragm.
He's got another idea, using the other SD22 Marine which has no air throttle (primary).
Another alternative is to use the Bosch VE which also does not have an air throttle but ... the VE has some other problems to carry out.
-Philip Passed 08May2008
My friend, you are missed . . .
1982 Datsun 720KC SD-22
that works fine..thats how mine is..
ie turbo..intercooler..throttle..inlet..engine..
works a1...ip measures boost and fuels accordingly..(up to about 12psi unless one fiddles..)
only problem i have found is i think the throttle restricts air flow at anything other than flat out..(though it gets boost from 1000rpm) and this causes egt's to rise too quick..i think..dug out my turbo ip..mrs allowing(yes will be fitting it at work at night in the dark..atleast she wont know that i am working on the darn car again!!) will be done by this time next week..
turbo it
(sd33t home turbo set up if anyone is interested..)
zen wrote:that works fine..thats how mine is..
ie turbo..intercooler..throttle..inlet..engine..
works a1...ip measures boost and fuels accordingly..(up to about 12psi unless one fiddles..)
only problem i have found is i think the throttle restricts air flow at anything other than flat out..(though it gets boost from 1000rpm) and this causes egt's to rise too quick..
I think Galen would like to read your work, Zen.
Here's how Galen -used- to do things.
Last edited by philip17 years ago, edited 1 time in total.
-Philip Passed 08May2008
My friend, you are missed . . .
1982 Datsun 720KC SD-22
1200° is ok on a motor with lower compression ratio but being unwilling to pay the price to know for sure, I'd also wager that it should be just a few seconds on an SD motor.
