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1991 Hyundai Excel GS AWD Compound Turbo

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GSR-VR

Proven Member
111
5
Oct 7, 2012
Albuquerque, New Mexico
Since my Mirage project as went south I have decided to keep all the goodies and shoot for the same goal. The car will be "like stock appearance" and I want to run crazy low compression. Say 6.0-1. (Maybe it'll be a non-interference conversion?LOL) The reason why is to deal with the crazy boost levels of 50+psi. with the compound setup. Thanks Paul Volk for posting your setup and all the information you have shared with the DSM community! You've been a wealth of data!

Originally I saw Marc Evans compound turbo 2JZ31 and was very impressed. I sought out to do the same on my little project. (Thanks Marc, where ever you are, I'd like to speak with you one day)

Back on track, this is going to be a street car. A light to light car. I don't plan on taking to the track very often but when I do it'll be sand bagged.

List of parts thus far:
- DSM Link V3 with Eprom Conv.
- Various turbos ranging from EVO 3 16Gs to a Holset HX83.
- 4 bolt rear end with LSD
- 15" BBS ultra lite wheels with M+H slicks
- A few spare 6 Bolt 4G63 engines


The First order of business was to make sure the engine and transmission sat straight and "level" in the engine compartment of the Hyundai. This was not an easy task seeing as the previous owner saw fit to bash in the frame to squeeze in the 4G63. Now that was sorted I moved onto the issue of the engine mounts. I finally decided to go with a tube frame front end and relocate the alternator for maximum space. A "dummy" engine now sits in the bay with the new AWD 5spd trans with equal length half shafts to check fitment everywhere. My main issue is the rear mount. It seems I'll have to weld a plate to the firewall and then brace it accordingly.

I'll be getting a bone stock engine back from the machine shop next week or so and I'll start the fab process while the race motor is being built.
 
6:1 compression ratio??? i think you would have a problem even starting that thing, and it would take forever to spool even a smaller turbo
 
I was under the impression lower compression was easier to start? I was also reading that you want a low compression ratio to take full advantage of the astronomically high pressure I will be seeing with this setup. Also I if I recall correctly compression ratio has little to do with the actual "spooling" characteristics of the turbo. It just helps bridge the gap between off boost and on boost. I figure I have room to spare here seeing as the car with the AWD weighs in at 2340lbs. I think I can afford to run a low compression motor. Look at Honda builds, they lower their compression by 2, sometimes 3 full points when building a turbo motor. I'm just doing what I think is right. If someone else can shine some more light here I'd be very thankful of that, regardless weather I am correct or not.
 
i have never seen anyone build a that low compression on a motor, even a honda low compression motor is usually around 8:1

its all about FUEL you can build a 10.5:1 motor and boost 50psi if your using the right fuel.

https://secure.buschurracing.com/ca...d=150&osCsid=fd093a7d17aeac2cae796a0fc9e3ef99

one of the top names in DSMs and Evos sells a 900HP capable short block and uses a standard 9:1 comp ratio.

dont reinvent the wheel buddy, we have countless examples of how to make serious power its not a guessing game.

if you want to be different fine build it, but everyone will only laugh at you when it fails miserably
 
i have never seen anyone build a that low compression on a motor, even a honda low compression motor is usually around 8:1

* Does this mean its wrong? Does this mean that since YOU haven't seen it before it's going to fail?

its all about FUEL you can build a 10.5:1 motor and boost 50psi if your using the right fuel.

* In that case Top Fuel engine builders are wrong by running 5.0-1 compression and should listen to you?

https://secure.buschurracing.com/ca...d=150&osCsid=fd093a7d17aeac2cae796a0fc9e3ef99

one of the top names in DSMs and Evos sells a 900HP capable short block and uses a standard 9:1 comp ratio.

*I'm aware of Mr.Buschur and I'm very impressed with what he has done. However I'm not trying to be him or follow what he has done. I'm looking for torque out of a small engine via compound turbocharging. Its proven.

dont reinvent the wheel buddy, we have countless examples of how to make serious power its not a guessing game.

*Countless examples of what I'm not doing. If calculations based on hard, irrefutable data is guessing, then please by all means tell me what else I'm doing wrong.

if you want to be different fine build it, but everyone will only laugh at you when it fails miserably

*I'm not worried about anyone laughing at me. It's going to happen anyway. You're talking about a 1991 Hyundai. How could you NOT laugh at it?! :)
 
I ran 7.7 compression in my first high power 2.4 4g63. that engine rocked. lasted 15,000 hard miles before failed meth pump took out a rod. many years ago guys in so fla ran 7.5 for very reliable fast 600whp cars. ( very fast at the time)

I agree that compound turbo shoul use low compression . you have plenty of air with two blowers. lower compression = more fuel in chamber. chamber is bigger.

fischer buggies fastest turbo bug in world still runs 6.0-6.5 compression.

high compression became popular whe setting records for turbo size. with an airflow limit you have to raise compression to maximize power.

one of bigest challenges of compound turbo is dealing with very high compressor outlet temps. this is a good way to reduce detontion thresh hold.
 
6:1 compression ratio??? i think you would have a problem even starting that thing, and it would take forever to spool even a smaller turbo

Compression doesn't spool turbos, displacement does.

Also I if I recall correctly compression ratio has little to do with the actual "spooling" characteristics of the turbo. It just helps bridge the gap between off boost and on boost.

You are correct.
 
Less compression leaves more heat in the exhaust gas to perform work on the turbine. Spool threshold is a function of exhaust mass and energy. More dynamic compression for a given displacement makes it more thermally efficient.. meaning more heat from combustion is transferred to the crank, less in the outgoing exhaust to the turbine.

Its the same reason exhaust bypassing through the wastegate is hotter than the exhaust stream leaving the turbine. This is taken advantage of in some clever compound systems to electronically control the high pressure (small) turbine's wastegating to help bring the low pressure (big) turbine.

Even though there is often much less exhaust mass coming through the HP wastegate, it is often 300-500*F hotter then the turbine wheel outlet flow temp. It will also be moving faster.
 
Thank you everyone for chiming in. I will try and snag some pictures of the car's progress thus far into the build. However with my R34 GTR coming in Monday evening the build might be a little slower than expected.
 
Thank you everyone for chiming in. I will try and snag some pictures of the car's progress thus far into the build. However with my R34 GTR coming in Monday evening the build might be a little slower than expected.

Looks like I might end up eating my words and 10k... Its Tuesday morning and the transporter was stopped by NHSA+NMDOT to see what all the fuss was about. I'm having to sign a $#!+ ton of paperwork... It doesn't look like much gets passed them without them knowing...
 
Skyline is gone. I lost my job and so did my boss. Although the Hyundai is coming along nicely. I've been super busy making a manifold for my friend David. I hope he is pleased!
 
Hx83? You know thats like a 2ft turbo right? Compound or not.. Too big.

Hx35 on left
a5ysese7.jpg
 
You could light that sucker using an s300sx or a 37r on kill kode.. Just in time for redline.

Think 13-15k rpm needed at 2.0l displacement and a power goal far exceeding the most powerful current 4g63s to make that worthwhile as a primary charger. ~200lbs/min and very high PRs
 
I notice a theme here, a lot of talk, no pictures and no results. And some whoppers for stories.
 
Hx83? You know thats like a 2ft turbo right? Compound or not.. Too big.

Hx35 on left
a5ysese7.jpg

I should've clarified. I have one but didn't plan on using it in this application but its more so saying that I have a wide range of turbos to choose from.

You could light that sucker using an s300sx or a 37r on kill kode.. Just in time for redline.

Think 13-15k rpm needed at 2.0l displacement and a power goal far exceeding the most powerful current 4g63s to make that worthwhile as a primary charger. ~200lbs/min and very high PRs

I have a S256 but was unsure weather or not to use that.

I'm sure that 70+psi would have some interesting results on an HX83. However I do not have an unlimited budget. I am a student/fabricator. Not a millionaire playboy.

I notice a theme here, a lot of talk, no pictures and no results. And some whoppers for stories.

Nice Dodge, I've read that build on 4G61t.org. :thumb: Also congrats on the WR on a 4G61. Impressive. Please tell me, am I a liar as well because I own one of the fastest Starions that's still street legal?

as a single in a 26cm housing they come on at 4500RPM on a 6.6l v8 diesel

Mine is a 29cm housing T6 divied. I'm sure there is no "real" chance of spooling it. The only reason why I listed the HX83 in my original post is to say I have some options if I so desire. NOT that I'm going to attempt to spool the HX83.
 
Last edited:
How about posting a pic of it setting on top your motor? (HX83)
 
How about posting a pic of it setting on top your motor? (HX83)




Holset vs Borg Warner S256

AWD 4 Bolt fitment. A little tweaking left to do. Mounts are made of 1/4" steel. Details later.



Just finished it last week. Well the first part of it.



Best of 10.71 @ 134. Still 5spd. Still 4G54B SOHC. Pump Gas.


 
An S200sx in a divided T4 housing is a perfect base turbo IMO. Pretty fast spool and no MWE grooves so the piping can be cleaner.
 
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