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Engine Specific Info and Questions => IDI Engine => Topic started by: saurkraut on August 12, 2009, 07:56:23 pm
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I've done it, and the results are lack luster. As a matter of fact, I'll call it down right horse-it
Granted, its on my 1.6TDblock/1.9head project, so there are other variables in play.
The Build: http://www.vwdiesel.net/forum/index.php?topic=15780.0
But I'm getting high EGTs with the same pump that I had on the same engine that used to have a 1.6 mechanical head. And that would only touch 1300º F occaisionally.
The boost seems to build a little slower, but the EGT shoots up past 1300º F as the boost climbs to about 25 PSI.
I rotated the boost pin back to a lower slope, and put the plastic collar back in, and its a little better, but I wouldn't run it through all five gears full throttle as it will probably go past 1500º F.
Pump timing is set at 1.04, injector break pressure is set at the upper limit. 2.5" exhaust, turbo to rear bumper. No intercooler.
I'm wondering if the K26 compressor doesn't like to make that much boost?
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Hmmm. I have an identical build with a T3 and i never hit 1300... 1200 is like a max with mine. the only difference is im using an intake off the TDI ALH engine and my head is hydrualic. It will get to 25 very quickly. Did you port or polish your manifolds or head?
I have no clue what my timing is set to or injector pressures. i have 2.5 inch from the turbo back to the rear tires where it splits to dual 2.5.
My high egt times are usually when the rpm is too low.
oh, PS. what advantage is it to remove the plastic collar? should i remove mine? :P more fuel on boost?
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The k26 compressor i used was off of a Audi 5000. I got a feeling this compressor flows really good at 10PSi then falls on its face.
I noticed the other folks who have made k24/k26 hybrids don't seem to share there observations.
Maybe that says volumes right there.
Oh, I polished the heck out of everthing, matched the ports to the manifolds, ported the head useing the david vizard article. It should go like a scalded cat, but the EGT is spiking rapidly.
I'll test it a little more, then yank it off the car and put it back to a standard K24.
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Which flavor k26 is the compressor from? You're right though, any version of K26 that I have seen a map for is WAY out of it's efficiency range at 25 psi.
Brendan
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Which flavor k26 is the compressor from? You're right though, any version of K26 that I have seen a map for is WAY out of it's efficiency range at 25 psi.
Brendan
Kind of begs the question, why even do it? The stock K24 does well up to 25 PSI
The compressor is out of an Audi 5000 turbo quatro (gas motor).
Well, I geuss I'll take it off, and put it back to a proper K24.
Should be in the FAQ, do you have any data you can post?
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I'll throw up a few quick calcs. After a quick google search, i can't seem to find which flavor of K26 the Audi 5000 had, I'm sure I could find it if I dug a little deeper, but these are the ones available up on squirrel performance's turbo calculator.
For reference, this is a 1.6L running about 25psi.
K26-1
(http://www.squirrelpf.com/turbocalc/graph.php?version=4&pr0=1&pr1=1.07&pr2=1.87&pr3=2.67&pr4=2.67&pr5=2.67&pr6=2.67&pr7=2.67&airflow0=1.8&airflow1=3.9&airflow2=8.4&airflow3=14.4&airflow4=17.5&airflow5=19.5&airflow6=21.1&airflow7=21.7&product_id=104)
K26-2
(http://www.squirrelpf.com/turbocalc/graph.php?version=4&pr0=1&pr1=1.07&pr2=1.87&pr3=2.67&pr4=2.67&pr5=2.67&pr6=2.67&pr7=2.67&airflow0=1.8&airflow1=3.9&airflow2=8.4&airflow3=14.4&airflow4=17.5&airflow5=19.5&airflow6=21.1&airflow7=21.7&product_id=105)
K26-2470R
(http://www.squirrelpf.com/turbocalc/graph.php?version=4&pr0=1&pr1=1.07&pr2=1.87&pr3=2.67&pr4=2.67&pr5=2.67&pr6=2.67&pr7=2.67&airflow0=0.014&airflow1=0.029&airflow2=0.064&airflow3=0.109&airflow4=0.132&airflow5=0.147&airflow6=0.159&airflow7=0.164&product_id=117)
K26-2664G
(http://www.squirrelpf.com/turbocalc/graph.php?version=4&pr0=1&pr1=1.07&pr2=1.87&pr3=2.67&pr4=2.67&pr5=2.67&pr6=2.67&pr7=2.67&airflow0=0.014&airflow1=0.029&airflow2=0.064&airflow3=0.109&airflow4=0.132&airflow5=0.147&airflow6=0.159&airflow7=0.164&product_id=118)
None of the K26's really are suited for that kind of boost pressure.
Brendan
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The last one is probably it; Audi 100, K26-2664G.
Screw it, I'm not going to run it with that compressor any more.
Off she comes.....
Thanks for the info! :)
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ship that bad boy over to me for a few days, let me see how it works on my 5000. i want to build one, but if you say its not worth it, then its not worth it. the biggest thing with the K26 tho, it flows alot better than the K24, it may not make more boost, but it has alot more air going through it at a set boost pressure than the K24 does.
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I hated my k24/26..... While I did not have any egt issues(I'm intercooled) but the lag was pretty bad and not really a useable rpm range for dding
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so, should i just keep my K24 on my audi like it is? i just made a boost controller yesterday, and set it to about 18 psi in the shop, but havent put it on yet. whats the upper limit for these? like 25 psi or something? whats safe? 20 psi?
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K26 on an Audi 2.0 TD @ 18psi (sea level, intercooled):
(http://www.squirrelpf.com/turbocalc/graph.php?version=4&pr0=1&pr1=1.07&pr2=1.65&pr3=2.23&pr4=2.23&pr5=2.23&pr6=2.23&pr7=2.23&airflow0=0.017&airflow1=0.037&airflow2=0.07&airflow3=0.114&airflow4=0.138&airflow5=0.153&airflow6=0.166&airflow7=0.171&product_id=118)
Not great. :P
Brendan
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k24 is better suited to the engine? i dont really know how to read turbo maps that well either.
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ship that bad boy over to me for a few days, let me see how it works on my 5000. i want to build one, but if you say its not worth it, then its not worth it. the biggest thing with the K26 tho, it flows alot better than the K24, it may not make more boost, but it has alot more air going through it at a set boost pressure than the K24 does.
Sorry, no dice. I'll need the K24 hot side and bearing housing to reassemble into a full K24 for my 1.6/1.9 project, and the K26 stuff i'll keep for my '86 TQW.
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I guess the issue is how the compressor works at a specfic boost pressure.
Since I haven't gotten around to installing an intercooler, we have a more or less direct comparison of the two compressors.
From my experiment, it can be seen that at 25 PSI, the K24 compressor does a better job than the K26 compressor. They both get to 25 PSI, but the k26 is heating the charge air a heck of allot more than the k24.
I wonder if it opposite at 10PSI?
I wonder if there is another K24 compressor that does a little better at 25 PSI?
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is it safe to run a K24 with the wastegate set at about 25psi with a wastegate still hooked up and boost controlled?
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is it safe to run a K24 with the wastegate set at about 25psi with a wastegate still hooked up and boost controlled?
I seem to have had no problems running one at 25 PSI for a few years. You can't get there by screwing in the set screw in the dash pot on the waste gate. Screwing it in makes very little difference until you get to the point where the spring coil binds and limits the amount the waste gate can open.
There are two solutions: Some sort of a boost controller, or disconecting the boost line to the waste gate and plugging the banjo bolt with RTV. The waste gate majically blows open from exhaust pressure right around 25 PSI and works just fine. The set screw in the dash pot can raise it even further. It seem to adjust better in this range. You can get to 30 PSI by overfulling, but that is boost creep mode and the EGTs get pretty high.
The only failure I've had is loseing a small piece of the trail edge of one of the turbine blades. But that was on a k24 that had over 400,000 miles on it.
http://www.vwdiesel.net/forum/index.php?topic=14895.0&highlight=
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They both get to 25 PSI, but the k26 is heating the charge air a heck of allot more than the k24.
That is very interesting as the idea gas law says the heat from compression should be the same... maybe the K26 is less efficient at that speed and imparts a lot of energy through more churning of the air (heat from mechanically moving the air around at high speed.) ???
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They both get to 25 PSI, but the k26 is heating the charge air a heck of allot more than the k24.
That is very interesting as the idea gas law says the heat from compression should be the same... maybe the K26 is less efficient at that speed and imparts a lot of energy through more churning of the air (heat from mechanically moving the air around at high speed.) ???
Yup, surprised the bejeepers out of me. Same pump settings, lower compression ratio, and the EGT goes nutz. It has to be the K26 compressor opperating beyond its capabilities.
I should have the K24 back togather and on the motor in a few days.
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I started a thread on my small block ford site. there are alot of really smart proffesional guys there. I asked with a quote from here about "15psi is 15psi" My custom cam grinder Jay Allen posted the below:
Quote from: par442k on Today at 01:11:51 am
Wouldnt a smaller turbo need to spin faster to move the same amount of air as the larger one, thus creating more heat.
Posted by Jay Allen:
This was where I was going to go with part #2 of the discussion.
Boost in fact is not boost. 15 psi is not 15 psi.
Indy car back when they had turbos on them used a pop off valve at 25 psi. At first there was 2 cars that seemingly had 100 more HP than everyone else. Hmmm.......Then whatever the name of the sanctioning body was stepped in and imposed a "maximum turbo size" as the fast guys were using a GINORMOUS turbo and it was barely working. The air was being bleed off so no one "really" thought about it.
Do you guys remember who this was? They could not keep engines together at Indy to save their life.
An air charge temperature sensor points this out, instantly. Boost is heat and hence why intercoolers kick ass. A smaller unit with a much higher impeller speed is going to create far more heat. So while "15 psi is 15 psi" in your mind and on the "boost" gauge, there is a significant amount of power to be had with a bigger unit that is not working near as hard.
Where you measure matters as well. Check boost at the turbo, in the intercooler (if there is one), at the blade of the throttle body, and then in the plenum.
Hope This Helps.
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maybe things should be reworded .....
15 psi is 15 psi , only if the temp of the compressed air is the same .......
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air is air wether its at 0 psi or 4000 psi, its still air. when it gets hot or cold tho, then its not the same, since air expands and contracts quite a bit.
so, witch ever turbo keeps the air the coolest will push more, since it will still be slightly shrunk. but if you have a turbo that heats up the air at the same amount of boost, it will effectively move less air. thats why boost drops when you add an intercooler, the air shrinks and it can compress more to make up for it.
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The K26 compressor is off, the K24 compressor is back on, and EGTs are back in the ball park.
The boost builds faster too.
The K24 compressor makes 25 PSI boost at a cooler temperature than the K26 compressor.
Go figure.
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really? im gonna scratch the idea of a hybrid then, if the 24 performs better, lol.
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Saurkraut, it's great that you did this research, and had some before and after comparisons. I know I had K24/K26 hybrid on my mind too. Sounds like I'll stick with the K24 and call it a day.
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15 pis to 15 psi argument eh??? ;D A little post I read years ago explained it perfectly, this is based on Ford Cosworth YB engine but it is apt to the discussion.
quote:
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Foolishly, sorry, Originally Posted by erm.. someone
Look at it this (simple way so you understand ), imagine a 1 ft diameter balloon inflated to 15psi. Then imagine a 2ft ballon inflated to 15psi - are you trying to tell me that both have the sane volume of air in them?
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That balloon is actually bigger so yes it holds more volume, but this is not applicable to an engine because even if we take all the inlet valves out and pressurise the system with our turbochargers, we are still presenting each turbocharger with the same volume to fill, lets say 2000cc for the cylinders and 1000cc for the intake of the head and the plenum / hoses.
So we have a 3000cc volume to pressurise with air. This does not change unless the engine begins to operate. An engine will only generate more power by shifting more air at the correct AFR. SIMPLE.
The engine will only shift more air if we do one of the following:
1) Improve the airs route into the head.
2) Increases the pressure we push it in with.
3) Improve the mapping.
4) Improve the volumetric efficiency.
So,
We still know a T4 WILL make more power than a T3 at the same boost so why is that?
We don’t appear to have done any of the above mods do we?
The head hasn’t been ported.
We are running the same boost.
So have we changed the engines VE?
Good question, and back to turbo’s.
A T3 50trim with our desired pressure ratio of 2.4 (14.7psi inlet +20psi outlet divided by 14.7psi inlet) will be spinning at 134,000 rpm with a compressor efficiency of 70%.
A T4 60 trim with our desired pressure ratio of 2.4 (14.7psi inlet +20psi outlet divided by 14.7psi inlet) will be spinning at only 97,000 rpm with a compressor efficiency of 82%.
Now lets go to the turbine housing.
The T4 P trim wheel flows a lot more air than the Std T3 trim rear wheel. (They are all the same as std on T3) but it conversely takes more to spin it to speed.
We now have an exhaust backpressure IMPROVEMENT due to a better flowing rear wheel!!!!!!!
Secondly,
We now have a wastegate that will open much sooner and much wider than it would on the T3 as less exhaust volume is required to spin the turbine as we have a 37,000 rpm improvement in efficiency at our 20psi.
HEY, we have another exhaust backpressure IMPROVEMENT.
If our T4 is using a bigger housing, and it IS if compared to a T3 we have another exhaust backpressure IMPROVEMENT!!
So lets go to boost at the intake:
Now our exhaust backpressure is reduced, our cylinders demand for air has increased. We have overlap efficiency gains, we have thermal efficiency gains so we can suck more air and we can suck it with a greater pull because we are actually revving more freely so our peak piston velocity has increased.
So we are CONSUMING more air and this T4 can supply it for fun… But… we aren’t making more power because the T4 pumped more air at 20psi.
We are making more power because this turbo improved the volumetric efficiency of our engine mainly through exhaust backpressure reductions and an improvement in outlet temperatures at the compressor outlet due to Adiabatic Efficiency which we may or may not discuss later.
It's ALLLL about back pressure and operating within compressor ranges people. ;D
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so i wasnt wrong. not at all. a bigger turbo does flow more air at a certain boost level than a smaller turbo at the same boost. the bigger turbo is working more efficiently. and heating the air alot less too i bet. the bigger turbo moves more air at the same boost because it can also flow more air out the turbine more easily.
so, whoever told me i was wrong, is sadly wrong.
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The 'bigger' compressor in this instance appears to be the k24.
I was going to do some measurements of the K27 inlet and oulet to just for for s*** and giggles, but I was in a hurry to get the K24 right.
Side by side, the K27 compressor looks skinnier, so maybe that's its downfall.
It flows just dandy at 10 PSI on a bigger engine, but does a hors-it job at higher booste on a smaller engine. Keep in mind the hot side stayed the same, so the turbine flow/restriction was the same.
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You need to think of it more in a relationship to the turbine, it may be bigger and flow more with the K26 front end but the back end is still K24 so it is trying to force more air through the same restrictions....
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true, witch is probably why his EGT's were through the roof. those K24 turbine housings are TINY!