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Discussion Starter · #1 ·
I originally wanted to set up a Twin-charged system in my Impala utilizing the stock GenIII M90 with some eBay turbo kit, but after being told again and again that it's inefficient, not worth the time, and a stupid idea altogether, I've decided to increase my budget by $5,000 and opt for a TWIN TURBO WITH THE SUPERCHARGER. Eat that ZZP.

All I really have right now is plans to adapt a junk yard Gen5 M90 onto my L67 and some theoretical twincharge diagrams I found on a Holden Commodore forum.

This is a big undertaking for someone who's only ever done stereo, oil changes, and ignition system maintenance. But I'm hoping I can achieve it with your guys' help. Though I'm not sure the 171k mile trans and engine are gonna handle any of this in the first place...

For now I just gotta deal with that U-bend!
 

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Sooo... you're talking about dealing with a U-bend, and leaping to building a TT twin-charged setup?

ZZP has the most experience previously building twin-charged setups, including getting the world's 1st 9-second pass with a front-wheel-drive 3800 car. When they tell you that it's not worth the time, they're not BS'ing you when they could be taking your money for a turbo kit and sending you on your way. There's a difference between YOU deciding to do something for kicks, and a company dedicating manpower to something they've already done multiple times, and to a higher degree than anyone on the planet.

TL;DR - build what you want, be ready to come up with solutions to issues that are specific to only your vehicle, and expect things to not fit/work right the 1st-2nd-3rd time/seem like it's not going to work/etc...

Until then, keep it maintained and enjoy.
 

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Discussion Starter · #3 ·
All of this is just an ultimate goal with no expectation of completion anytime soon, I'm expecting a lot of trial and error but that's every first-time project. I'm planning on getting all of my basic mods and preparation knocked about before I even touch anything relating to forced induction.

Just ordered my new downpipe and exhaust system and I've got a cart full of ZZP performance parts.

Hopefully next is going to be new cams & rockers, then on to the Gen5 M90 swap with all the supporting mods to go along with that.
 

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Twin turbos feeding into a gen 5 is like trying to swallow an entire thanksgiving turkey whole. That's just my .02, but I do wish you luck with your project

Something to note is that you can't run both a cam & high ratio rockers. Its one or the other otherwise you will have interference issues. The only rockers you will be able to run with a cam besides stock is 1.6 rollers or zzp's 1.65 rockers.
 

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Sooo... you're talking about dealing with a U-bend, and leaping to building a TT twin-charged setup?

ZZP has the most experience previously building twin-charged setups, including getting the world's 1st 9-second pass with a front-wheel-drive 3800 car. When they tell you that it's not worth the time, they're not BS'ing you when they could be taking your money for a turbo kit and sending you on your way. There's a difference between YOU deciding to do something for kicks, and a company dedicating manpower to something they've already done multiple times, and to a higher degree than anyone on the planet.

TL;DR - build what you want, be ready to come up with solutions to issues that are specific to only your vehicle, and expect things to not fit/work right the 1st-2nd-3rd time/seem like it's not going to work/etc...

Until then, keep it maintained and enjoy.
Zzp did not do it using the bypass valve as a turbo feed as far as I know. John Galm, for those of you who do not know him, made a twincharged Grand Prix that made 1100ft lbs at 3200rpm and just shy of 700hp at about the same rpm. He ran out of fuel at 3100rpm and chipped 2 pistons because of it and is currently rebuilding the car again and it’s the intent of showing zzp they should’ve stuck with twincharged. I am doing the same build in my 95 camaro with a th400 and plan to break the f body 3.8 record. with lots of collaboration with John I think I can do it. Twincharged has more potential than most people see
 

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The turbo does the brunt of the work for making power. (Edit) Also, there's a reason no other platform is commonly doing twin-charged builds to reach max effort potential... or it'd be the most common thing getting tossed into every foxbody build in every garage, instead of just choosing which turbo combination they're slapping on their LSx build. We only consider it in the 3800 world because M90's came on the top of our engines, and we hit a wall at ~400whp unless we change out the power adder. At this stage, a few folks decided to not change what was on top of the engine while adding the better power adder in the engine bay, and it is basically a novelty/extra headache to leave the s/c on the engine, still.

1100ftlbs at 3k sounds like a pretty tall order, since the only 2 advertised 1000+whp builds have been stroker turbo Aussie builds in RWD platforms.

If it is something that the owners are trying to get out there, it'd be nice to see that stuff in some videos and postings, etc. rather than hidden in a back garage that doesn't help the community get new ideas. I really wish your first post was an intro post with some basic info about you/your car/current mods/plans/why you're here... and wasn't, "oh yeah? well I know a guy, you don't know him but I do, and he already made more power than anyone else... and I'm gonna be the fastest now, too"
 
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The turbo does the brunt of the work for making power. (Edit) Also, there's a reason no other platform is commonly doing twin-charged builds to reach max effort potential... or it'd be the most common thing getting tossed into every foxbody build in every garage, instead of just choosing which turbo combination they're slapping on their LSx build. We only consider it in the 3800 world because M90's came on the top of our engines, and we hit a wall at ~400whp unless we change out the power adder. At this stage, a few folks decided to not change what was on top of the engine while adding the better power adder in the engine bay, and it is basically a novelty/extra headache to leave the s/c on the engine, still.

1100ftlbs at 3k sounds like a pretty tall order, since the only 2 advertised 1000+whp builds have been stroker turbo Aussie builds in RWD platforms.

If it is something that the owners are trying to get out there, it'd be nice to see that stuff in some videos and postings, etc. rather than hidden in a back garage that doesn't help the community get new ideas. I really wish your first post was an intro post with some basic info about you/your car/current mods/plans/why you're here... and wasn't, "oh yeah? well I know a guy, you don't know him but I do, and he already made more power than anyone else... and I'm gonna be the fastest now, too"
I apologize for coming off that way. This man(John Galm) is in his 70’s I believe, he’s retired and does this for fun, his daily is another twincharged car and I don’t have a clue how much power that one makes. The only platform he’s on that I’ve found is Facebook and he’s very open to sharing his knowledge but doesn’t care or doesn’t know how to share it publicly like we do on forums, I stumbled upon him and am glad I did. I have been in the 3800 game for probably 4 years now and started with a bone stock base model 95 camaro with a 3.8. I did exhaust and intake like every other newbie and decided I wanted a turbo. I’ve had from a gt3582 all the way up to now my vsr72/96. On my camaro I have been through 7 4l60’s a couple stock the rest “built” with only one being fully built then swapped to a th400, destroyed a near stock one and I am now using a 2000hp rated th400 reverse manual transbrake deal. I had an l67 swapped s10 that I did the swap on. Started with a bare shell, dropped in an l36 with the s10 t5 and spun a cam bearing so I said screw it and put in the l67 then went through 4 clutches in 3 months, the last one being a centerforce 600hp rated clutch and said screw it to that and went to a built 4l60 and sold it a couple months later. The camaro is now my only project and it will once again be the daily. I work at an engine machine shop and have done the full 9 to the engine that’s going in my camaro now. I will be using the vsr 72/96 along with an m90 I have about 20 hours into porting for the 2.5” bypass valve. I ported my heads and built my motor entirely. It will be running in less than 2 months. So that’s my intro, I apologize for coming off harsh, I’ve been reading in these forums for years but never felt I knew enough to give any input but I’m making my way now. Also I tune with hp tuners as a side job and I have megasquirt Ms3x going into my camaro to get more tuning capabilities. Camaro is on engine #4 now, last one sent the factory l36 rod through the block daily driving on 605whp turbo application for 3 months. Now it’s built motor time
 

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Here’s the dyno graph from John. I guess it’s not quite 1100 but you get the point. He lost fuel pressure at the power drop there since he was using a single aem 400lph pump
 

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Ah, the ole torque flash that we do to alot of dynos. Still a good HP curve, similar to the harder-pushed turbo builds I'm trying to imitate myself.

Feel free to start a new post when you want to share a profile and progress of the build.
 
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Discussion Starter · #10 ·
I really appreciate all the back and forth input y'all have put in, I've been going over this thread for the past couple days and I'll continue to do so as I continue my build. I just finished my exhaust system, so right now I'm just working on interior stuff like getting rid of the god awful quick release steering wheel I decided to put in.

Just started my research into E85 and I think the new plan is just twincharge on a modest turbo, get my M90, LIM, and TB ported, and run that with the E85.

I don't think I'm looking to push huge amounts of horsepower, the initial goal was 450whp but I'm fine with even hitting around 350-400.

I'm always open to learn and explore other solutions and learning it from the guys who've been in the game longer than I have is always a delight. I only just started getting into cars back in January of this year and here I am already running my own exhaust and sound system.
 

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Ported LIM's and TB's are snake oil, for the most part, aside from matching the opening to an intercooler. Upgrading to a 75mm Northstar TB is the simplest way to free some flow, primarily on a GenV M90 that utilizes the larger inlet design better.

I would get your feet wet with some initial upgrades that will start you off, and I guarantee by the time you are about $500-1,000 into the process, you'll know what/how you want to go (or not) from there.
 

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Discussion Starter · #12 ·
Ported LIM's and TB's are snake oil, for the most part, aside from matching the opening to an intercooler. Upgrading to a 75mm Northstar TB is the simplest way to free some flow, primarily on a GenV M90 that utilizes the larger inlet design better.

I would get your feet wet with some initial upgrades that will start you off, and I guarantee by the time you are about $500-1,000 into the process, you'll know what/how you want to go (or not) from there.
My bad I didn't mean ported TB, I actually do have the Northstar in my cart at ZZP already haha. As for the ported LIM, wouldn't porting that manifold be the only way to make use of the ported SC? Or should I just do an L32+GenV swap?
 

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The opening only needs to align to the outlet properly. Porting a Gen 3 M90 mainly removes the cast corners at the large end of the outlet triangle, along with smoothing the inlet path some (Gen V's corrected this from the factory). The LIM's already have this rectangle opened at that end. Some shops also knock out the bar between the M90 outlet and the bypass opening, without much reason besides possible exposure for more of the intercooler cores.

Focus on what big ticket items you want beyond basic bolt-on's... Intercooler, cam/valvetrain, turbo kit, exhaust header/manifold setup, etc. You can spend more than the value of the car real quick, depending on what you do, so be aware of that. And this isn't counting transmission, suspension, and cosmetic parts.
 

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Discussion Starter · #14 ·
The opening only needs to align to the outlet properly. Porting a Gen 3 M90 mainly removes the cast corners at the large end of the outlet triangle, along with smoothing the inlet path some (Gen V's corrected this from the factory). The LIM's already have this rectangle opened at that end. Some shops also knock out the bar between the M90 outlet and the bypass opening, without much reason besides possible exposure for more of the intercooler cores.

Focus on what big ticket items you want beyond basic bolt-on's... Intercooler, cam/valvetrain, turbo kit, exhaust header/manifold setup, etc. You can spend more than the value of the car real quick, depending on what you do, so be aware of that. And this isn't counting transmission, suspension, and cosmetic parts.
Just wanna make sure I read that right, and thanks for all the tips.

So no need to port the LIM because it'll match up with the ported M90 anyways?

Also the car actually came with aftermarket headers when I bought it and I threw a 304 Stainless steel exhaust kit on recently. As for an intercooler I wanted the ZZP Short Stack but I haven't seen it in stock for months.
 

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The short stack is not a great choice, due to sealing issues of the odd plate/hose design, and being much less effective than the full size for the same install effort. Their Stg2.5 looks to be the best new product they've updated in that area in recent years, too.

If you're doing an intercooler, I'd just open the LIM towards the bypass to match the core somewhat.
 
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