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- #241
VTcruiser: This thread is a free for all.
The turbo in the picture, it that from Maarten?
The turbo in the picture, it that from Maarten?
12H-T performance Build (1 Viewer)
- Thread starter gbentink
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Yes it is. that's the damaged unit, my new CHRA has not arrived yet.
- Thread starter
- #243
VTcruiser - looks like a Supra comp wheel, or at least from the same family. Definately not a T04e, so you are safe. Anyway, buying from Maarten would be a safe option.
That's what I figured, thanks! I have to agree, Maarten is very knowledgeable and has been an absolute pleasure to deal with.
- Thread starter
- #245
- Thread starter
- #246
mudgudgeon
Resident galah
My 1HD-t is mated to a manual.
re supercharger, the thing that appeals to me is bottom end torque from idle especially with a manual. As deisels are low revving compared to petrol, the supercharger could be significantly overdriven and stay within its efficient range. Sounds like this is what your bro did?
compounded with the a turbo providing secondary boost, as the supercharger is approaching the top end of its stand alone efficiency range, the turbo will be feeding a greater volume of air than the supercharger would draw on its own, and the turbo has already compressed it. My thoughts are this is going to change the superchargers characteristics quite a bit.
I have found several s/c + t/c compounded vehicles with guys' experience supporting this idea
I have thought about setting it up with a clutch, but think it would complicate tuning of the mechanical fuel pump, same with bypass. If it was clutched or bypassed at idle, I think it would be very smokey. I think to get it to work best, I would set up the aneroid so that it didnt see any boost signal from the supercharger, and pick up boost signal from the turbo.
one thing I'm not sure about is if the supercharger was overdriven, would this put an ecxessive load on the engine at low RPM? I think the deisel is probably torquey enough to cope.
re supercharger, the thing that appeals to me is bottom end torque from idle especially with a manual. As deisels are low revving compared to petrol, the supercharger could be significantly overdriven and stay within its efficient range. Sounds like this is what your bro did?
compounded with the a turbo providing secondary boost, as the supercharger is approaching the top end of its stand alone efficiency range, the turbo will be feeding a greater volume of air than the supercharger would draw on its own, and the turbo has already compressed it. My thoughts are this is going to change the superchargers characteristics quite a bit.
I have found several s/c + t/c compounded vehicles with guys' experience supporting this idea
I have thought about setting it up with a clutch, but think it would complicate tuning of the mechanical fuel pump, same with bypass. If it was clutched or bypassed at idle, I think it would be very smokey. I think to get it to work best, I would set up the aneroid so that it didnt see any boost signal from the supercharger, and pick up boost signal from the turbo.
one thing I'm not sure about is if the supercharger was overdriven, would this put an ecxessive load on the engine at low RPM? I think the deisel is probably torquey enough to cope.
mudgudgeon
Resident galah
can you explain choke flow? and how would you tell if this is happening (apart from turbo desintegration 
.
I disconnected the waste gate after having problems with a bleed type boost controller. I was sure the wastegate wasnt opening at all, and the bleed valve was making a mess and didnt seem to be working properly.
I had chatted with a turbo rebuilder about ct26 and asked him what safe boost limit was. His opinion was that they are safe producing up to 22psi (I think he was talking about supra turbo), so I was happy enough to let mine peak at this pressure
.I disconnected the waste gate after having problems with a bleed type boost controller. I was sure the wastegate wasnt opening at all, and the bleed valve was making a mess and didnt seem to be working properly.
I had chatted with a turbo rebuilder about ct26 and asked him what safe boost limit was. His opinion was that they are safe producing up to 22psi (I think he was talking about supra turbo), so I was happy enough to let mine peak at this pressure
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- #249
Stating the turbo is safe to 22psi is correct, however the conditions where that is safe was not stated which has lead to your turbo failure; or at least contributed. One such condition, perhaps the most important, is the CFM's flowing through the compressor. I can categorically say that on a 1HDT, a good condition CT26 is safe at 22psi at 2000rpm. This is because at ~ 310cfm (based on 2000rpm, 4.16L engine, 87%VE, great intercooler) the turbo compressor has limited trouble drawing in the air through the compressor inducer. It is not safe at 3500rpm where it would be trying to pump probably 450cfm and it cannot because it is being "choked" at the inducer.
The turbo compressor rpm is controlled by many factors, but one important factor is how much "work" it is doing. With the condition of "exhaust gas flow approximating a fixed rate or energy", more compressor work means more load which means less shaft rpm, due to increased torque demands. Conversely, reduced work requirement means reduced torque requirement so the shaft speed will increase.
In a "choke" condition, and as you approach this condition, the air density right at the face of the compressor inducer decreases (so this means "thinner air and less work) shaft speed drastically increases because less work can be done by the compressor, but the drive power from the turbine is still present - especially in an overfuelled condition!
The best real world example that everyone can probably relate to is the increase in "pitch" of a vacuum cleaner when the vacuum orifice is blocked or restricted. The pitch change is due to an increase in the rpm of the electric motor. It may sound like the electric motor is doing MORE work, but the rpm increased because it is doing LESS work. The inducer diameter is effectively becoming a retsriction.
For a fixed boost level, as your rpm increases, so does your compressor speed in order to cope with the additional airflow. Most turbos get fairly near maximum safe rpm at peak power. There is a safe operating area that can be operated in that allows extra boost typically, however using up all of this safety combined with hitting the choke flow can cause an overspeed situation, and BANG. Also combined with a turbo that is out of balance due to years of fine debri might mean a bad resonance + overspeed = BANG.
Choke flow is gradual and if you look on the right side of a compressor curve and see rpm lines, you will see they rapidly head near verticle as you increase cfm and boost.
The supra with a 45.5mm or 47mm inducer, has less restriction and therefore the safe rpm for 22psi boost is higher
You can work out if it is happening by looking at the size of the compressor and the boost you plan to run on the size of the engine you have; this far and away the best thing to do - it is a pure science in that calcs work in practice. Turbos from factory come fairly well sized, so you are heading in danger territory if you change things over stock - I guess that should be obvious. It is having an understanding on where you can change things that is the key.
On a practicle level it is hard to judge when getting choke flow because turbine energy is very much fuel controlled, even under choke flow, so you cant simply look at how EGT's change. Lower is ALWAYS good, but going higher doesnt always mean choke flow, it may mean too much backpressure because of exhaust turbine sizing.... Since both choke flow and backpressure are bad, EGT's are GREAT to keep an eye on.
If you can control max fuel (make it independant of boost), adjust boost up and notice a EGT decrease, then you are not at choke flow. This is cumbersome way to test because you have to then keep adjusting your fuel up, then adjust fuel up and so on until you notice that increased boost does not reduce your EGT's. then of course, as mentioned above you could be getting too much back pressure of hitting choke flow. I use the term hitting, however it is not a brick wall (close though).
In my opinion, soon to be tested, the most usable power and optimum modified std (still CT26) setup on both 1HDT and 12HT is to use stock turbine housing and assuming a big "turbine back exhaust" and a "great intercooler" is to lightly clip the turbine and fit a Mitsubishi 16G6 compressor. Should be 180kw @ flywheel minimum at ~21-25psi boost. I used an 18G with unclipped turbine on my 1HDT and in retrospect I consider it was a bit over sized with too much exhaust backpressure. Clipping the exhaust should improve flow ~ 5-10% (so I hear) and fitting a 50 trim 68mm compressor wheel should increase the efficiency and thus reduce the drive power slightly.
So convinced am I of this that I just bought a compressor wheel to do just that. Of course, the Supra 47mm wheel is probably good for 18-20psi and 160-170kw anyway under the same conditions.
A dirty tune might give 5-15% more power than that.
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- Thread starter
- #250
Clutch operation would be straightforward if you want a simple setup and a bypass could be a vacuum controlled throttle such as the one used on the 12HT (and 2H?) to turn off the engine (used in reverse).
Overspeeding the SC is NOT a good idea just like overspeeding a turbo is NOT a good idea
My Brothers Patrol made great torque down low and the delivery of the torque was even more impressive, however it didnt make good power up top and used HEAPS of fuel beacuse it was consuming engine torque pumping in air that most of the time was not required. I would call it a BAD idea, generally.
I would only setup a SC to be from a certain throttle setting. For example, on a 4.2, up to ~ 250nm torque, it is not beneficial, so only contributes to poor economy. Depending on your gearing, a typical 4.2 non factory turbo diesel only needs ~ 200-250nm at cruise anyway.
mudgudgeon
Resident galah
Hmmmm!
sounds like I should edit my earlier post! My turbo probably didnt suicide, It was choked!!:whoops:
One reason I increased boost was due to lower EGTs for the same fuel delivery.
Exhaust back pressure definitely wouldnt have been a problem, I have a 4" engine/dump pipe that reduces to 3" to pass the transfer case, then exits at the back, its all mandrell bent, the tightest bend would be 70* with a single straight through muffler.
intercooling is on the wishlist.
will you be using the mitsubishi compressor wheel in supra housing?
sounds like I should edit my earlier post! My turbo probably didnt suicide, It was choked!!
:whoops:One reason I increased boost was due to lower EGTs for the same fuel delivery.
Exhaust back pressure definitely wouldnt have been a problem, I have a 4" engine/dump pipe that reduces to 3" to pass the transfer case, then exits at the back, its all mandrell bent, the tightest bend would be 70* with a single straight through muffler.
intercooling is on the wishlist.
will you be using the mitsubishi compressor wheel in supra housing?
gbentink and Dougal,
have either of you considered using a supercharger in compound with a turbo?
I have a Eaton m112 supercharger I am contemplating using on my 1HD-T with a large turbo for secondary boost.
I have read of guys having a lot of success with this on petrol V8s, beyond a lot of peoples expectations.
The supercharger provides boost from Idle and helps the turbo spool up quicker due to scavenging action and increased exhaust volume. Once the turbo is producing boost it increases the volume of air available for the supercharger to pump.
I know lots of people regard superchargers as a parasitic drain on the engine, but it seems to me that S/C and T/C would work beneficially with each other and give the best of both worlds.
just wondering if you guys have any thoughts on this without hijacking gbentink's thread too much
No, I don't consider superchargers and diesels to make a good match.
Firstly they're a parasitic loss that's always there. Reducing economy and power.
Secondly, the need for boost in a diesel continually varies, turbos match this quite well, where a supercharger is almost never going to be giving what you need.
I've got a turbo that's currently giving me more boost than my engine can smoothly use, so more boost down low won't offer me any benefit.
Have you noticed that there are no factory supercharged diesels? Only turbocharged.
mudgudgeon
Resident galah
re: supercharger, my terminology might be wrong (I cant keep up with you guys in the Jargon stakes )
I wasnt considering 'overspeeding' the S/C.
Eaton publish the m112 efficiency range from 4000rpm to 14000rpm, on a deisel that redlines at ~4200rpm, this means the pulley ratio can be about 3:1 with out exceeding the superchargers efficient rpm. If this was done the supercharger would use approx 10hp to drive it at 4000rpm (engine speed approx 1300rpm)
If a clutch was used with a S/C and T/C compounded, with aneroid set up to increase fuel once turbo came on boost, how would you overcome the problem of overfueling when the supercharger was disengaged?
I was thinking an elctric clutch, switched to engage/disengage at part throttle.
One small dificulty is finding a clutch and pulley off the shelf that suits 8 ribbed belts for the m112
My 80 has standard gearing apart from 35" tyres (change of 10%)
) I wasnt considering 'overspeeding' the S/C.
Eaton publish the m112 efficiency range from 4000rpm to 14000rpm, on a deisel that redlines at ~4200rpm, this means the pulley ratio can be about 3:1 with out exceeding the superchargers efficient rpm. If this was done the supercharger would use approx 10hp to drive it at 4000rpm (engine speed approx 1300rpm)
If a clutch was used with a S/C and T/C compounded, with aneroid set up to increase fuel once turbo came on boost, how would you overcome the problem of overfueling when the supercharger was disengaged?
I was thinking an elctric clutch, switched to engage/disengage at part throttle.
One small dificulty is finding a clutch and pulley off the shelf that suits 8 ribbed belts for the m112
My 80 has standard gearing apart from 35" tyres (change of 10%)
mudgudgeon
Resident galah
Why is this so? I would guess cost and simplicity of manufacture would play a big part?
I am sure I read somewhere recently that one of the big car makers had developed a compounded s/c+t/c system for a small diesel passenger car? could be wrong.
I know Nissan built a car a decade or so back, using s/c+t/c. it was only available in Japan and was developed so it could be used for rallying
could you explain this? I would have thought having forced induction is always going to be a good thing?
It isn't just cost stopping them from supercharging. The economy and performance loss is a major too. Economy diesels are turbocharged, hot-rod diesels are turbocharged.
VW currently produce a twin charge engine (supercharged and turbocharged), but they're petrol. They overlap the supercharger and turbocharger to get a wide torque curve. Diesels don't have the same rev range and can take higher boost so it's not a problem.
I haven't heard of that Nissan, we get all the JDM cars imported here (New Zealand) used.
Since diesel engines speed is controlled by fuel, there's no point in pumping more air than is needed. It takes a lot of power to produce boost and doing so when not needed costs fuel economy among other negatives.
That's the best thing about a turbo. When the engine works harder the exhaust temps rise which drives the turbo harder and creates more boost.
So boost is balanced to the need for it (in a well matched system).
I'll see if I can find out.
Here's my set up: ~'93 1HZ in an '86 HJ60, 2.5" downpipe (tight quarters!) to 3" exhaust, no intercooler (yet...), standard boost at 8 psi. I've only had the turbo on for a couple weeks so I was keeping it conservative. I'd eventually like to run up to 12-15psi but I am not sure how much the ID head can handle efficiently. This cruiser is being set up for expedition, so frankly power is third behind reliability and fuel economy. For that reason, i have no dyno numbers so the only measure of power I have is the smile on my face.
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- Thread starter
- #257
Hi Dougal. The twincharge engine being referred to is the 990cc engine used in the Nissan March. It was used for a while. They may still make it
Tapage
Club 4X4 Panamá
Actually beyond the CT26 quality and capabilites ... I'm much more concern about the 12H-T or 1HD-T block and head resistance to up boost levels like 18 PSI plus PSI :.
Rods, pistons, studs, head etc ..
Rods, pistons, studs, head etc ..
Oh right, we missed out on that one. Plenty of boring Nissan March's around here but none like that.
Japan has tax laws based on vehicle size, engine size and engine output. They make for some really strange and interesting vehicles in the JDM market.
VTCruiser, I'd expect an engine with higher compression to have a lower exhaust gas temp for the same fuel loading. In addition the IDI head loses more gas temperature to the coolant.
Maybe they just liked the engine to rev more with the bigger housing?
