Opinions on CT26 Turbo
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- #22
Thanks guys. But what about the perfect aspect ratio's? What are the A/R's of the T-25 and the A/R's of the CT-26? The T-25 says it's for 1.2-1.8 liter engines. Someone said because it was designed for gasser that it would be perfect for the 3.4 liter diesel. If this is true i believe the Supra was a inline 6cylinder which would probably be a 3.0-4.0 liter motor(i'm guessing), which would mean the CT-26 would be way too huge for any 3B(if this theory was right). But people have run this turbo with fine results. So it's confusing to figure out which combo makes the best choice for my parameters. Again, i don't want low end(RPM) turbo. This 3B is torqey enough at low RPM. Infact, it jumps around 4-wheeling with very little throttle bumping. I was thinking something that would kickin strong when i'm merging into traffic, or climbing a steep grade, or passing a car. All of which means i'm probably already at 1500-1800 RPM. But i don't want to have to rev into the 3000 range to get this power. Hopefully that helps alittle more. Appreciate the responses.
A/R isn't really the aspect ratio. But I guess it describes it quite well.
There are two exhaust A/R's available in the T25 turbine (exhaust side), 0.49 and 0.64. The 0.49 is the one you want and the one you'll find on your typical 1.8-2 litre petrol engine.
On a 3.8 litre Isuzu I get 10psi boost at around 1400rpm and can get 20psi by about 1800rpm.
On a 3B you won't want to run more than about 12psi boost, simply scaling my results by engine capacity will get you very close.
I also agree that a turbo from a 3 litre petrol engine is far too big for a 3.4 litre diesel. Simply working out the airflow based on capacity and rev range will show the problem there.
But Eric seems happy, however he also reports a linear relationship of RPM and boost, which I have never seen before. 5psi at 1000rpm is indeed a strange claim. The smaller T25 doesn't spool until about 1200rpm.
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- #24
Thanks Dougal. O'kay, maybe you can clear this up for me: Why does a gasser(1.2-1.8 liter) compare to a diesel(3.4L) when it comes to turboing? I mean it's only air volume right? If a 4cyl.,1.8L gasser was idling at 600rpm and next to it a diesel 3.4L,4cyl. idling at 600rpm then the gasser breaths and exhausts twice the air volume as the diesel(right)? Hope that makes sense,obviously i'm still confused. And again,thanks for all the replies.I'll get this sooner or later.
Turbos on petrol engines are sized to work at full throttle for the top half of the rev range. Say 3500 rpm+
Turbos on diesel engines are sized to work in the middle of the rev range, say 1500-3500rpm.
Petrols and diesels process similar air at similar speeds if the petrol throttle is wide open. If the throttle is closed they have greatly reduced airflow and usually cannot produce any boost.
A petrol at 2000rpm at full throttle and a diesel of the same capacity at 2000rpm will process the same volume of air.
So basically. Take the T25 on a which on a 1.8L petrol spools around 3500rpm, stick it on a 3.8L diesel and similar airflow occurs at 1700rpm.
There are a lot of other factors at play as well (this is an extreme simplification), but you get the general idea.
Once you think you've found a suitable turbo, do your homework and see where else it's used. If you can find someone else using a similar turbo on a similar engine then it's a great second opinion.
It took me about 6 months to settle on the T25, shortly after I did I managed to buy a garrett turbo that was fitted to the later models of my engine. Interestingly enough it was a T25, minor differences to the cover (hose connection instead of bolt flange) and a non-wastegated turbine. But the compressor was identical.
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- #26
Hows the turbo know it's on a gasser(so its doesn't spool till 3500) or it's on a diesel(so it spools at 1700)? Yea i know, i',m a PITA! BTW- I just read the Turbo fundamental section on Garretts website. Very informative. It gives an excellent mapping program with formulas and mapping for the DIY'er. I don't know exactly all the info. to input for the graphs. If you get a chance, check it out. I would really be interested(as well as everybody) to see what garretts mapping would call for our 3B's. Thanks for the help.
It's not the rpms per se that spools the turbo...it's the amount of air flow....it takes the gasser that much more rpm to produce the same volume of air movement.
at least I think.....
at least I think.....
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- #28
O'Kay, if that's true, that makes good sense. So does anybody know(have the specs) how much air volume a 3B produces/requires? I'm sure in some tech manual there must be some formula based on the bore/stroke/liter/cyl.size-capacity/comp.ratio,etc. Also, isn't the garrett used in the turbo glide kit. Both ATX and turbo glide claim they build there turbo specific for the 3B. So somehow they(supposedly) found all the info to match a turbo.
...don´t wanna go into too much calculating but,
at 1000 rpm it should flow 45 CFM
at 2000 rpm it should flow 95 CFM
at 3000 rpm it should flow 150 CFM
this is with volumetric efficiency at 80% and a 200 Cu engine (3.3L)
this is a 4 stroke NA engine.
at 1000 rpm it should flow 45 CFM
at 2000 rpm it should flow 95 CFM
at 3000 rpm it should flow 150 CFM
this is with volumetric efficiency at 80% and a 200 Cu engine (3.3L)
this is a 4 stroke NA engine.
Gasp! "The smaller T25 doesn't spool till 1200RPM" sounds like you need to be more specific, on which engine? 3B?, farm tractor or what? Your could,should,might be opinions are becoming tiresome. Why don't you go out and buy a 3B and GASP!, a real Landcruiser then you can try your opinions in the real world. You post, opinion after opinion without any fact or experience as it relates to those opinions. Again you spout your opinion as fact. 5PSI at 1000RPM, is fact, not opinion, nothing strange there, in fact why don't you ask Irongiant about that "claim", he observed the exact results you claim that are "strange" this last weekend. There is most likely many things "you have never seen before" Linear relationship of RPM and boost, lets see a given engine is a fixed displacement, at X rpm the volume of air is Y. Increase X, and Y will increase also, physics 101, and which engineering school did you go to? BTW I am not just "happy" I am also satisfied with the results. Why is it so hard for you to understand your personal theories may not be accurate/or reflect reality.
eric
Here you go:
Airflow rate=CID x RPM x .05 x Ev/ 1728
CID=self explanitory
RPM=see above
0.5= 4stroke engine intake once every 2 revolutions
Ev= average volumetric efficiency of a normally aspirated engine, .85 for this purpose
1728= converts cubic inches to cubic feet
Airflow rate= pressure ratio x basic engine cfm
The above comes from pg 27-28 "Maximum Boost" by Corky Bell,
Amazon.com: Maximum Boost: Designing, Testing, and Installing Turbocharger Systems (Engineering and Performance): Corky Bell: Books $23.00 +/-
Do your own research, draw your own conclusions, there are no short cuts. In other words figger it out yourself, its not that hard, its been done before, Google comes up with lots of info.
eric
Take the turbo to ANY diesel/injection shop and get a rebuild/and/or kit. Coast injection in Salinas Ca. told me he could get a kit for about $70.00.
Here you go:
eBay Motors: Toyota Rebuilt CT-26 Turbo CT26 Supra MKIII (item 160223561787 end time Apr-03-08 18:00:42 PDT)
or:
eBay Motors: CT-26 Toyota Super DeluxeTurbo Genuine Rebuild Kit (item 150232115285 end time Apr-08-08 08:38:32 PDT)
or:
eBay Motors: Toyota turbo ct26 ct-26 celica supra used (item 230236336826 end time Apr-03-08 07:36:02 PDT)
Or for an even cheaper source try a local or not so local craigs list for lots of $50.00 CT26s.
Yeah I guess "expensive dead end" sums it up aptly. Again another useless expensive dead end opinion. What is it with you, do you have a basement full of GT25s in your basement you are trying to sell on eBay?
eric
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Go shopping for a new compressor wheel or exhaust housing to fit your CT26. Then you might understand why they're a dead end for parts. Especially when the $50 ones turn out to be in worse shape than the one you're trying to repair.
Airflow through a turbocharged engine is not linear with rpm. When the turbo spools it becomes an exponential rise.
Compare 1200rpm with 0 boost and 1500rpm with 15psi boost. At 1500rpm and 15psi it is now drawing 96% more air than at 1200.
On a nonturbo engine it's 25% more flow.
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Yeah, dead end, mine was brand new. The Supra performance community still uses the CT26 and there is plenty of demand for the parts.
eBay Motors: Toyota Supra CT-26 Turbo Compressor Wheel (item 160222951589 end time Apr-02-08 08:36:28 PDT)
See the previous post from Maximum Boost, those formulas were taken right from the book, not invented. Your opinion about exponential flows are just that opinion and in fact unreasonable, 0PSI at 1200RPMs and 15psi at 1500RPMS? My numbers were from PERSONAL observation, mine and Irongiants, if that doesn't coincide with your view of the universe, oh well. I am sorry that your turbo doesn't produce any boost at 1200RPM and comes on at 1500RPM with 15PSI. You might try a CT26 the boost production seems more linear than your turbo. I am gonna go ahead and recommend you get a CT26!
eric
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A supra wheel won't fit the CT26 that most people use on a 3B.
I'm afraid to make use of a forumula, you must first understand it's use.
Your formula is for air consumption without any boost.
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I used the Supra CT26. I will help you understand, first you need to know the displacement of the subject engine in cubic inches. You will then need to know the RPM of said engine. Efficiency is a constant.85 .0.5 is for a 4 stroke engine.
1728 is a cubic foot. You then take the end number and multiply that times the forced induction ratio. Pressure ratio= 14.7+ boost divided by 14.7.
There you go!
eric
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That approach will always give you the wrong answer. There is no such thing as a "forced induction ratio". You must use the air density ratio.
This requires knowledge of the inlet conditions (pressure and temp) along with an understanding of adiabatic compression and a map of the compressor efficiency.
Here is the process to find your density ratio, this example was posted up by me on 4btswaps.com on feb 16th last year. PR is 2.25 which is boost of roughly 18psi.
1. Start with intake conditions, pressure, temperature, density. Use PV=NRT to ensure you know all relevant conditions. Work in absolute temperature (Kelvin scale), My conditions are for temp 293K; pressure 101.3 kPa and air density of 1.2 kg/m^3
2. Find your pressure ratio, in this case 2.25
3. Apply adiabatic compression to find the outlet temperature relating to a 100% adiabatic compression. T2/T1 = compression^(gamma-1/gamma).
Gamma is 1.4 for air. Tout = 369.4K
4. Find the adiabatic temperature rise. This is your adiabatic outlet temp (369.4-273=76.4K) your adiabatic outlet temp.
5. Divide this temp rise by your compressor efficiency (0.65 in this case). This gives you your actual outlet temperature. (76.4/0.65+273 = 410.5K)
6. Use PV=nRT to find the the volume (and density) of the output charge using your pressure ratio and your actual outlet temp and density. Density = 1.93, intake density =1.2
density ratio =(1.93/1.2=1.61)
7. Divide original density by resulting density to get the density ratio. 1.2/1.93 = 1.61
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Gentlemen. this is your final warning!! Any more mudslinging below this post and the thread WILL vanish along with the info contained in it and we do not want to loose good info because of disagreements!
I'm not interested in getting into your "pissing contest" but in my copy of "Maximum Boost" the formula noted by Eric is prefaced by the following: "To calculate the airflow rate of and engine without a turbo - i.e. no boost"
You both need to be sure that your sources of info are correctly quoted and correctly applied. Please NO MORE mud slinging, I can and will delete the thread if necessary.