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Post by kcswimrac on Apr 22, 2014 15:23:08 GMT -5
Hi there been following this forum for awhile, finally decided to make my first post. So I bought a carbed '89 Justy a few months ago for $500 as a car to toy around with and have some fun going places my non $500 car could only dream of. I bought it with a slight burning oil problem with the plan in mind that I am going to search this summer until I can find a FI engine somewhere, to rebuild along with aftermarket engine management (probably megasquirt). Currently the car gets used for forest exploring, driving spiritedly on loose surfaces and in snow. It has done triumphantly in snow and up 40° dirt hills and freeway driving. It spends most of its life from 1000 to about 3500 rpm. Now the questions that I pose is during my engine rebuild what machining, parts, or tactics can be used to increase low-end torque? I'm not looking for a horsepower monster 3 cylinder or a turbo. But a few steps in the right direction for a for a strong engine? My ideas so far are things like shaving the heads a tad to increase the compression ratio a little, perhaps Custom ground cam lobes, getting the heads well rebuilt maybe a port and polish, and probably get the weak points like rod bearings and anything else suggested friction coated. (Because only the best for my cheap justy lol.) Does anyone else have ideas to help? Also here is a picture of the justy, she has been preliminary named Joleen. Lol
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Post by Armageddous on Apr 23, 2014 22:34:27 GMT -5
Welcome!
You're on the right track with your build idea. My only other advice is do NOT lighten the flywheel, as it destroyed my low-end torque and do NOT build a large tube header, or a big fat exhaust.
The problem with shooting for low end in a Justy is due to the gearing in the transmission your engine is typically at 4000rpm on the highway, and if you're too far out of your efficiency range you will be paying for it later.
I'm not totally sure porting is a good idea, you don't want to increase airflow, if anything you want to restrict it so the engine isn't super responsive. Some of the torquey motors out there are low compression, with a small intake and carb, they are designed to operate at a certain RPM. The idea being they can provide fuel to rev the engine unloaded, but once they load up they are limited, and therefor will get good economy in that power band. Which brings upon the issue of EFI as most EFI manifolds are meant to perform at higher RPMS. You could put on a smaller throttle body though.
FYI I have a spare EFI engine if you live somewhere close to me, that I will be getting rid of fairly cheap.
Terry
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Post by kcswimrac on Apr 24, 2014 9:40:05 GMT -5
Thank you, I live in between California and Oregon between school and home. However, seeing how much difficulty I am having trying to find an efi engine I may just have to make that 10 hour trip. lol
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Post by madmatt on Apr 24, 2014 14:31:12 GMT -5
There is certainly room to deck the head... I've taken off nearly 1.5 mm with room to go and only just into the 10:1 range. Delta Cam Shafts has in in house spec on a slightly lumpier cam. My "re-build" thread is here. subarujusty.proboards.com/thread/2915/orange-rally-justy-returns?page=3I plan to dyno this spring eventually... my guess is un-tuned I'm making nearly 100 hp, and 90+ ft lbs. The carbs in my build are not likely what's making the power.
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Post by Armageddous on Apr 25, 2014 22:54:51 GMT -5
Come up any time madmatt has a pretty epic EF12, you can learn a lot from his thread if you're planning a performance build - But I doubt his is going to shine economically. Terry
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Post by madmatt on Apr 26, 2014 9:29:52 GMT -5
Terry, Whatever are you talking about I actually don't think it will be THAT bad cruising once fully tuned. But for sure right now running at 9:1 air:fuel at full throttle it's using a wee bit more then stock!
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Post by Armageddous on Apr 26, 2014 21:23:24 GMT -5
Rebuilt engine, high compression, triple carbs.. Something tells me your "cruising" days are over I'll be impressed if you can keep your foot off the floor. I did my swap 2 years ago and I still pull hard from lights.
kcswimrac - If you are serious about the potential trip up here, I will give you this engine for free. You can have an ECU and anything else you need to get going as well.
Terry
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Post by madmatt on Apr 26, 2014 23:08:49 GMT -5
Terry,
I re read your initial post to kcswimrac, you seen disappointed in your exhaust. I can't remember how big you went? I'm at 1.75" and it seems great, I thought you did 2" I can't see it falling on its face for that?... what size and length was your header? (I think you have gone back to stock)
also how much did you pull off the flywheel?
Matt.
kcswimrac, hope you don't feel thread jacked. ..
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Post by Armageddous on Apr 27, 2014 11:03:27 GMT -5
I can't remember the size now.. It was a short tube, and a 2" front pipe going under the engine. I'm still using it. I took nearly half the weight of the flywheel off, I think that was a bad idea. I can barely let my clutch out without it trying to stall (of course I'm used to it by now). I couldn't believe the difference when I drove the parts car home how nice it drove Tho it couldn't scream at 6000rpm either. Terry
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Post by indkid87 on Apr 27, 2014 13:14:31 GMT -5
About the flywheel lightening... I plan on taking some weight off mine soon, but before I do I'm going to make a CAD model of it. This way I'll be able to make different cuts and see what effect they have on the mass of the flywheel. All on the computer model without touching the flywheel.
Now I just need to find the spare time.....
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Post by Deleted on Apr 28, 2014 15:58:52 GMT -5
This is an interesting topic. I have often thought of having a "performance build" done when it's time for me to have a rebuild, but mine would be more along the lines of making the engine happier around 4-5krpm. I drove my Justy in today and went up some pretty steep 2nd and 3rd gear hills today. Even from ~2500rpm this car has a wild amount of torque for a 1.2L engine of any type.
I would think the only way to really increase low-end torque with this car would be a low pressure turbo, but that would be quite in-efficient at higher RPM.
My engine looks like it's starting to weep oil from between the block and head, so it might be getting close to time for me. If we can lighten and balance the rotating assembly, if that is applicable to these engines, that might be what happens.
I have wanted to make up a custom exhaust manifold for years, mostly to relocate the cat and just make it make more sense, but it would be critically important to not lower back-pressure while doing this, or be able to bring it back up with a muffler or somesuch.
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Post by madmatt on Apr 29, 2014 13:36:28 GMT -5
Wombatsauce, while I agree with you comment about the general torque-iness of our beloved 1.2... I can't help but to interject on the notion of backpressure. exhaust backpressure does not help in anyway, it only hinders. what does help increase hp that is often confused with backpressure is scavenging. increasing exhaust diameter to the point of slowing the exhaust charge can hurt performance. so people think too big a pipe and the motor starts loosing power. there must not be enough backpressure now. in fact what has happened is the charge now has a larger volume to fill, and so is slower moving down the pipe. this reduces scavenging at valve overlap, and exhaust gas is left in the combustion chamber. I did a quick google, I'm on my phone so hard to access good stuff. .. but here is real info (not typical internet pondering, much like I am doing now. ..) www.veryuseful.com/mustang/tech/engine/exhaustScavenging.pdfand that is why I asked Terry about his exhaust size, because with out good modeling all we can do is compare this to that. I've was running 1.75" with no cat and a glass pack for years. trust me it didn't hurt. now I have a cat again, but it's huge and at the very end of the system. ask in an attempt to keep the charge screaming down the pipe! I make no apologies for loss of economy. given my car sees less than a couple thousand kms a year I don't care.
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Post by JustyRally on Apr 29, 2014 13:48:50 GMT -5
Megasquirt is the route im going when i build my engine. Super charger with a clutch to disengage it for highway driving. DustysJustys offers different compression ratio pistons 8:1 - 10.25:1 www.dustysjustys.com/home.htm
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Post by madmatt on Apr 29, 2014 13:54:45 GMT -5
and while I'm at it. .. I'm going to refute Terry's comment about porting etc.
the only way to increase torque from a given motor without making it bigger is:
increase the amount of fuel and air it sucks in.
or increase the compression ratio.
so port and polish help it suck in more air. but the justy head is "pretty good" and you could just as easily muck that up as opposed to improving it. note, I'm no engine builder. but I've had some pretty sharp folks help me.
higher compression till you ping will make more torque too.
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Post by kcswimrac on Apr 29, 2014 19:20:04 GMT -5
Yay look at that, it looks like I may have started something good here. With my ever inquiring engineering student attitude I tend to agree with the "Less back pressure, more scavenging" belief. When I do my engine build I'll be looking all over to see if I can find a spare EFI head and someone with a flow test bench and hopefully, if we're lucky, we'll find out just how much a justy head can be improved. Also something that I found while internet surfing: is increasing the amount of intake/chamber swirl to help increase power. performancetrends.com/swirl.htmSo current build ideas: high compression (pistons if dusty justy has them, or deck the head if not), maybe a lite/mild porting and a nice polish ( because smooth quick air in the intake is important), a custom exhaust with length and size tuned to optimize scavenging at lower speeds (I'll have to do some calculations to figure out length), reshaped cam-lobes (I have to see what I can find on that), anti-friction coat the bearings, pistons, (and anything else I can afford to send off to get coated), then finally megasquirt. Any other ideas?
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Post by Armageddous on Apr 29, 2014 21:22:06 GMT -5
Don't polish up too much or you will lose air turbulence and fuel atomization, which will affect your burn efficiency and bottom line power.
Terry
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Post by justyjuggler on Apr 29, 2014 22:25:32 GMT -5
Does anyone else have ideas to help? Check compression/timing, Ensure gearbox(it's a 5spd?) dipstick is the pull-out, not screwed-in kind, Understand '89s are the most underpowered American Justy out there & never, ever let the coil to distributor wire touch the booster vacuum line…
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Post by madmatt on Apr 30, 2014 0:49:01 GMT -5
Don't polish up too much or you will lose air turbulence and fuel atomization, which will affect your burn efficiency and bottom line power. Terry Terry, you are more correct than my misleading post. .. I should have been more precise. porting helps. .. when there is a restriction. polishing is pretty much a wash. and it seems in must cases, textured surfaces allow for better fuel atomization , while boundry layer physics say there is little if anything to be gained with a smooth surface when the charge is "wet". also the same principle applies to intake with to large of a runner. but that is the whole runner. so necking down a throttle body is not going to increase torque. a narrow runner along its length might.
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Post by Deleted on May 1, 2014 10:45:02 GMT -5
Wombatsauce, while I agree with you comment about the general torque-iness of our beloved 1.2... I can't help but to interject on the notion of backpressure. exhaust backpressure does not help in anyway, it only hinders. Sigh... Yes. Okay. Technically that is correct. Though, I am looking at it much more simply than that since, like most of us, I would not really be able to apply all the fancy exhaust scavenging knowledge in the world if I had it, and create my own exhaust header/custom exhaust at this current time. Even all of that would be worthless without the ability to actually test and compare to find out real results. So, back here in the real world... Here is what I am talking about. If I go up a hill and experience the Justy's amazing torque, and then remove my muffler in the rear, toss it in the hatch, and go up the hill again, the experience will be decidedly different. The engine may pull more readily to redline, but the low end torque will be gone, and the top end "performance" is not worth the expense of the lost torque (in my personal experience/conditions/etc). That is the limit of my "scientific testing" at this point, and why I simply said exactly what I said. So, while it is technically correct that backpressure hinders and we are really talking about scavenging, simply reducing backpressure in the Justy's stock system by removing the rear muffler has a "real world" effect of reducing the beloved torque that makes the car very tractable and useful in metro areas. For all I know, it may post a higher straight-line acceleration time due to potentially more hp at higher rpm as a result of the reduced backpressure, but that is not important or what I am talking about here. The next level would be actually taking all of this neat-o theoretical/general exhaust know-how and apply it to some actual tests with an actual vehicle. For now, we know, if we remove our rear muffler, thus reducing backpressure in general, we experience a real-world reduction in torque. I have done this on two EFI Justys at this point. It even sounds neat without the muffler and pulls harder up top, but the reduction in torque makes the car more challenging to drive in places like San Francisco where you need a bit of oomph as you cannot always be at 4krpm.
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Post by Armageddous on May 2, 2014 20:44:27 GMT -5
A note on the scavenging, this is the reason I made a short header and used the angles to my advantage. My outside ports come in at 45deg angles to the center tube, I envisioned a venturi effect. No idea if this actually happens or not but that was my theory.
The phenomenon you're describing with removing the muffler does make sense. And here's how I see it. The idea of having back pressure in the exhaust is to help heat it up. Hot air flows much better than cold air. If you have a straight pipe exhaust, it is not getting up to temperature so the engine is pushing all this super hot air in to a (relatively) cold exhaust, and you lose the scavenging effect as the flow consistency is affected.
Terry
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