Complete Build Thread, Daewoo Nubira

Are you still planning to use the intake manifold from the 1500? If so, what will that do to the power peak?

Nah, I got the science high school to pay for the materials so we're going to make two manifolds from aluminum sheet. We're going to use the fuel injector bungs and the base of the runners, and I'm going to cut out the bung for the brake booster. Everything else, except for the TB, is going to be ground up.

Today me and the kids took measurements of the engine bay and built prototype models out of cardboard. We'll check to make sure our models fit during the next meeting. We also looked at the stock manifold (I've bought two extras to chop up and use as the bases for our competing designs) and decided how to improve upon it. Honestly, improvement shouldn't be that big of a challenge. The 180 degree, sharp radius turn can't be good for flow and the runner length of 790 mm is clearly biased towards low end torque.

You can see just how huge the OEM part is by looking at it attached to the engine.

The middle school kids came up with something pretty conventional for their design. Basically they shot for small size and good flow. If I had to bet, I would assume this design actually ends up dynoing better, although I think it's going to end up killing low end torque. You can see the pictures below, but they essentially made a triangular box that is biggest near the TB and tapers towards the number 4 cylinder. This design is only 10 cm thick and will probably cut the weight of the stock manifold by 60%. Just looking at it compared to the old one, I'm guessing this manifold will be considerably more high rpm intensive.

The highschool kids, on the other hand, came up with something really, really cool. I really hope this works better because if it does, it could be such a neat proof of concept.

As for the concept, the idea is to build a reasonably compact manifold with short runners that still maintains good mid range power and a flat torque curve. The high school kids are trying to do this by separating the airflow from the reversion waves as much as possible. In theory, the airflow moves largely undisturbed under the triangular cutouts, but each triangular cutout is designed to reflect the reversion waves at a 90 degree angle and off a flat surface before bouncing them straight back down to the runner. This effectively lengthens the duration of the reversion wave heading back to the intake valve with only a tiny increase in the size of the plenum and no increase in the length of the runner. I was playing with some ideas and think I might take this concept further by trying echo chambers of varying sizes attached to the vertical faces of each triangle. If the concept works, it should be a simple matter to make the manifold more low RPM biased by increasing the size of the echo chamber.

The students then decided to flatten the torque curve by staggering the distances of the reversion wave reflectors (what I'm calling those triangles). This should result in each cylinder having a slightly different torque curve. Since it has the longest distance between the intake valve and a reversion surface, cylinder one should make the best low end torque. Cylinder four should make the best high rpm power.

Like I said, I've never seen anything like this and I'm not sure if it will work, but the idea is so creative and interesting I'm really rooting for it.

The 2.0L engine I had swapped into the car is a complete POS. It's got a blown head gasket, a trillion oil leaks and a rod knock. Gonna send this "special, grade A used engine" back to the company that sold it to me and get something else.

Once I realized there's no chance I will rebuild this engine in favor of just getting another one, I made the corresponding realization that I don't care if it blows up or not. Commence hooning. Below are the assumptions I started with and the ways they turned out.

When I did the swap I kept the 1.5L Nubira's transmission on the theory that it would give me better gearing than the long legged 2.0 Leganza box. Not sure the ratios, but a Leganza is doing about 2300 rpm at 60 mph in 5th gear, my Nubira is at exactly 3k.

When I got the 2.0 I saw how long the intake runners were and guessed that this engine was tuned for low end torque. Got on wikipedia and saw a quoted figure of 134 hp at 5400 rpm and that seemed to back up my assumptions (although wikipedia rates my 1.5 at 107 hp at 5800 rpm and the engine actually made about 75 whp at 6600 rpm/fuel cut).

I figured the combination of short gears and torquey engine would give me stout acceleration and the ability to use all five gears on my home track. I should point out here that first is only good to about 30 mph, second barely gets you over 50 mph, and I will be redline limited to a top speed of 130 mph, so this is about the shortest box you'll find on a street/family car.

So, on to hooning. I rolled onto the throttle at 2k in first gear and immediately got a combination of wild wheel spin and hold on for dear life torque steer. At this point I'm muttering incoherently and smiling like a 16 year old chess club captain who wandered into a strip club.

Grad second gear and try again. It's a little bit less like wrestling a crocodile smothered in Crisco but not so tame that it won't spin up the tires when you hit a bump. It also gave me time to realize that the torque curve isn't very linear at all. 2k-3500 rpm is peppy, 3.5 to 5.5 is where I'm worried about 2nd gear wheel spin and then the space between 5.5 and 6.5 (redline) is where the engine stops producing power, but at least it gets so loud your ears bleed. I really wish they did more autocrosses, because I think this car would be a really good cone dodger.

I also think that I may now own the world's most anti-social Daewoo.

Excellent update as always, neat to see what a little monster you've created. Here's rooting for the high school kids' intake design, that looks wild.

Thanks.

I'm having a ton of fun doing this. There's almost nothing we've done so far that I couldn't have done faster alone, but getting the kids involved makes the process much more enjoyable. Before my projects were just me playing with a car. Playing with cars is fun, but if we're honest I'm really not that good a mechanic and I always ended up working with people who were less motivated than I am and/or had different goals with their own projects.

Now I'm managing a team, getting into the physics of suspension/aerodynamics/resonance/etc, practicing my Korean language skills and pretty much writing the first rule book for building a Nubira track car. I love a challenge and I love doing things nobody has tried before and this project has given me lots of both.

BTW, here's a drawing I made to explain the theory behind the high school kids' design.

There may or may not be a 2.0L TS20D engine in my Nubira these days. It may or may not be capable of burning the tires all the way through second gear on a moist road.

I may or may not be really irritated that Korea has suddenly decided to do its best frozen tundra impression.

Also lowered the rear suspension 1cm to try and get the roll center down a little bit. I'd love to tell you how this changed the handling, but black ice and handling tests don't play nicely together. Hopefully this will cure my rapid transition, sort of on the edge of jacking in the back problem.

What I can tell you is that the new engine is definitely optimized for low end torque. It's strong by 2,000 rpm, hits its peak around 4,000 rpm and is comprehensively out of breath by 5,800 rpm, which kind of sucks since the redline is 6,600 rpm. I can also tell you I will no longer be the slow moving shicane on the front straight of Taebaek Racing Park this summer. Torquey 2.0 plus 4.10 gears (1.5 stock gears instead of the 2.0 stock 3.54 gears) plus relatively small car equals an absolute hooligan.

Maybe the engine isn't quite as strong as I thought. There's a bushing in the front suspension that's going bad and flexing whenever I hit the gas, which explains the wheelspin.

Guess I'm going to go yell at the guy who sold me those bushings tomorrow ...

we just a nubira in the yard call if you need something 352 795 junk

DoD is Korea, Karl. The shipping would be rick-diculous.

@Karl,

Thanks but I'm an awfully long ways away. There are also a lot of Korean/American market specific nicks and nacks I'd avoid having to deal with, so I'll probably just keep dealing with the local junkyards.

Finished cutting out all the pieces of our custom intake manifold today and got the stock base quasi square, ready for welding. Pictures soon. It's held together by tape right now, but still, looks pretty epic.

My Korean friends all told me to expect smart kids at the science highschool and, holy crap, they were right. Hard workers too. They stayed with me until midnight on Thursday (would have stayed later but we ran out of cutting wheels) and then asked me if it was okay if they sacrifice their Saturday morning to finish the mockup.

Finally figured out the weird handling stuff with the car.

When I installed the poly bushings I noted that the car got much pushier and suddenly became insensitive to alignment changes. I had the weird episode where I thought the camber bolts slipped.

Turns out one of the front bushings was improperly sized and moving under load. Finally caught it and, wouldn't you know, the Nubira is turning in very nicely and allowing all sorts of trail throttle oversteer.

I also lowered the rear suspension 1cm in an effort to lower the roll center. I did this because under really good grip conditions in transition I could feel the rear start to jack up. The adjustment seems to be working as I know have less body roll overall (less of a stinkbug effect, I think) and a much more planted feel in the rear.

In a related note, goddamn canyon carving just got fun again.

I'm back in the US now but I had to leave the Daewoo until I return. While in the States I have access to a 528e, a Kia Sephia and a Dodge Ram.

Goddamn they are boring. None of them will even launch me into the roof if I go too fast over a speed bump.

I miss the Woo.

DaewooOfDeath wrote: I'm back in the US now but I had to leave the Daewoo until I return. While in the States I have access to a 528e, a Kia Sephia and a Dodge Ram. Goddamn they are boring. None of them will even launch me into the roof if I go too fast over a speed bump. I miss the Woo.

What gen Sephia?

If it's the one i'm hoping it is, i can help you do terribly evil things to that.

In reply to 92CelicaHalfTrac:

The dumpy one. With an auto. And hippy stickers.

Booooooooooooooooooooooo!!!

There's debate as to what motor the 1.8 really is if you have it... there's a good chance it's still a Mazda BP assembled by Kia.

BOOST IT.

I think my sister would object ...

Paddock picture because it makes me happy. :)

Moved to the build threads section.

In reply to Alan Cesar: Thankyou sir.

Great thread, thanks for sharing!

Because it would be a shame to damage something so priceless and artistically virtuous as the Nubira, I have bought guages. Volts, which I don't care about, oil pressure, which I do care about, and oil temperature, which I care about a lot.

Got the set for 17 dollars. Spent 170 bucks on an oil cooler setup that I'm getting in a couple weeks that will support all these guages.

This build is what GRM is all about, IMO. Please keep the updates coming!

I think you need to make box flares out of HVAC ducting.

Sky_Render wrote: I think you need to make box flares out of HVAC ducting.

YES! I want $32 worth of box flares. SO MUCH WANT!