GMT900 6.2 PPV Build Log

[Marky Dissod]

So you are saying that the thicker head gasket, reducing quench/compression,
will be less efficient at keeping the engine from detonation,
and therefore require higher octane to compensate for the increased chance of detonation,
if I am understanding you correctly.

Purpose of quench, especially in a wedge combustion chamber, is to enhance mixture motion.
During the squeeze, the 'flat' area of the piston rises to nearly meet the 'flat' area of the head.
They may not be truly flat, they're shaped so that combustion canNOT take place in those areas.
They instead push the air/fuel mixture toward the largest part of the combustion chamber in motion like bellows.
The further apart the 'flats' are, the less mixture motion is induced.

Other ways to avoid ping / knock are to choose the cam carefully, to write the spark tables carefully,
to choose the correct octane, and to achieve finer fuel atomization, which GM combined with more quench.
Compare the Gen5 pistons to the Gen4 pistons, then compare the Gen4 pistons to the Gen3 pistons.
As the piston chamber has evolved, so has the static compression ratio.

 

[ls3_ppv]

I noticed the PPV was burning oil and needing topped up about every two weeks. This motor didn't live an easy life, it was loud but slow and I had places to be. It came with an ebay catch can on the passenger or PCV clean side and i did what any professional idiot would do and remove that to upgrade to an even bigger catch can! As a master level internet sleuth I set to reading about catch cans, how they work and why they are needed. Since I was catching oil here but burning more oil than was caught I tried to vent to atmosphere from both valve covers based on what the internet told me. (lol)

Here is the catch can the PO put on the car. He mentioned I should upgrade this and the HPtuners guy commented it was weird to only have a can on the PCV clean side instead of the dirty and clean side or just the dirty side. Blue line connected the corsa intake to the can and provided a filtered fresh air feed. Green line routed to the PCV connection on the passenger valve cover. Let's call this PPV PCV rev. 1


Anyways, lets throw that away and install another ebay catch can! Spoiler: it didn't work BUT I did learn how to make AN lines even if they are scuffed up. Actually it did work to catch crankcase vapors, problem was it simply saturated the filter and oozed oil simply venting to atmosphere. Oh and there is no vacuum on the crankcase which helps to seal up piston rings, maybe prevent oil loss. I'd come to learn the err of my ways even if the internet told me this is the way. Lets call this PPV PCV rev. 2

 

[ls3_ppv]

I went back to the drawing board, there was improvements that needed to be made to the PCV system on this car. So I came up with this terrible drawing and this contraption of a PCV catch can setup.


I didn't realize until now that I had come up with a viable PCV system for a naturally aspirated LS motor. We have vacuum at all times pulled through the crankcase via the top connection of intake manifold, blowby cannot push into the intake tube, the catch can is now on the PCV dirty side of this motor and we can still vent excess to atmosphere after going through the catch can. Let's call this PPV PCV rev. 3

This worked, it worked well I might add. This was installed in April of 2022 and used for about 5 months. Bit of foreshadowing here but the only change needed to make this suitable for boost is an additional check valve on the connection between the intake manifold. Easy day! And unfortunately this idea of boost was also poorly executed....

 

[RooTBeeRthe1st]

Got to say, I'm interested to see what the next 2.5/3 years of your ppv's life consists of.

 

[swathdiver]

My bone stock 6.2 L9H puts down 372 rear wheel horsepower through the traps in the quarter mile.

Before you mod the motor to try and bring the power up, change the gears.

You can put a trutrac in the 8.6 or you can get a 9.5" 14-bolt out of a RWD Escalalde/Denali with 3.42 gears and then re-gear it. A P265-70-17 tire, being taller than stock PPV, will help a little in keeping the tires planted. Of course, the choice of tire is important in this endeavor. Michelin Defenders serve us well at the drag strip and on the street.

Those LS9 head gaskets by themselves would have dropped your compression ratio. We don't know if the block and heads were milled down and what pistons are in it to know for sure. L9Hs require high octane gasoline or E85.

Drivetrain losses on my 5.3 and 6.2s are just under 8%, the 6L80 and 9.5" axles are very efficient. If your circle D torque converter is a billet type, it will sap a bit more horsepower to turn it with the extra rotational weight.

Fun stuff!

 

[ls3_ppv]

Fast forward to August 2022, I've spent a bunch of time reading the advantages of a blower vs a turbo and for me it boiled down to a couple things. I like the torque of a positive displacement blower but seemingly every LSA swap suffers from belt slip and you'd be reworking the factory accessory drive which was not cheap, pinning the crank, going to an 8 or 10 rib crank pulley, etc. Remedies were out there but I wasn't a fan of spending 4-8k for a boostdistrict LSA or magnuson package and needing to put a few thousand more into it potentially. The huge upside to a supercharger kit is that its bolt on, remove the stock intake manifold, slap on injectors and change your accessory drive bits and you are pretty much done. It's fully reversible and retains a good bit of value used if I ever need to sell. Install is a weekend ordeal and you are back on the road.

HOWEVER (lol) a turbo, well that's a value proposition for my lizard brain. Sure you gotta rework the exhaust completely, come up with intercooler piping custom for the vehicle, create a provision for the turbo oil drain, tap in somewhere for oil feed to the turbo. Unless you have some experience doing turbo installs in general or spend a lot for a well put together kit (huron speed, fahler maybe?) this is NOT a bolt on affair. So I did the only reasonable thing and bought about the cheapest kit I could find on ebay, it says it fits my year and model vehicle and they wouldn't lie about that would they? After all, I hate the exhaust setup still on this vehicle and installing a turbo would allow me to cut it all out so the additional hurdles are worth it to me.

I stumbled across MMI speed shop, hoo boy. On sale for less than half the cost of a basic LSA supercharger package and free shipping to boot! Wow what a steal, I couldn't hit the buy button fast enough. This place was offering a "complete" single turbo kit and I am here to tell you that I threw most of that damn kit in the trash. Their hotside and downpipe are decent but the intercooler, intercooler piping, turbo, brackets, wastegate and BOV are all dog water. I hadn't realized the headache I just bought myself.

Parts delivery and inspection:


Install day and removing this amateur hour exhaust system, you can see here I'm noticing that the AC and heater hoses are going to get crispy when that turbo goes in:

 

[ls3_ppv]

I didn't even try and use the MMI turbo kit intercooler, it was TINY! But I did have this unit sitting around, so it'll have to do. Had some spare exhaust piping and eyeballed the angles, fabbed a bracket to the core support, hit the intercooler piping with some black paint and put it in place. This intercooler was at least twice as tall and slightly wider than the one that came in the kit.



I am sure some of you will be right along to tell me how small this turbo is trying to feed a hungry 6.2 liter motor. And I would completely agree with you. It was a 62mm smol boi and with this big cam that wanted to breath up top in the RPMs it was also not matched well. Seems to be a theme for this vehicle.


Completely installed, base tune loaded to get it back home and if you'll notice there is also a Mighty Mouse breather on the passenger valve cover now. It is check-valved and I put it into place to be able to visualize the blowby, I noticed I was having some at idle now. But this is my first LS turbo and I thought maybe that's normal? (spoiler: no its not.) But damnit I have a boosted LS3 now and its making all the right noises that my pants stay tight starting this thing up and driving it around.


Turbo PPV first Cars & Coffee, I'm riding high on my sense of accomplishment and ran into another souped up gmt900 PPV. He had a 6.0L iron block and LS3 heads swapped in his. I took it as a sign of good luck!

 

[ls3_ppv]

When you add more air, you gotta add more fuel. So I made probably the first in the line of good decisions for this build and selected a drop in, bucketed 415LPH fuel pump and some 900cc injectors from Deatschwerks. I've been involved with a couple more LS motor builds and tuning since then and I cannot stress enough how important it is to select a reputable injector company that has responsive support and provides good injector data. Deatschwerks gets two thumbs up from me, I even got to chat with some of their engineering team at LSfest East. Great company to deal with!

DW400 pump 9-401-7015




I also picked up fuel pressure, boost and wideband gauges from AEM and installed them into a Glowshift triple gauge pillar. Very happy with these part choices, all of which are still in use. The serial and analog outputs from the AEM wideband work natively with HPtuners and can be used to activate things like lean safety controls too. Top notch products, quality and fitment from AEM and Glowshift here too.

 

[ls3_ppv]

Got to say, I'm interested to see what the next 2.5/3 years of your ppv's life consists of.

Going back over the saved photos and reliving this is more exciting that I expected it would be. Appreciate the kind words!

 

[ls3_ppv]

My bone stock 6.2 L9H puts down 372 rear wheel horsepower

This is good data, you will see further down the timeline soon that it was down on power with the cam before I went and put a turbo on it. BTR estimates something like 60-70bhp with the cam in a 6.2, I expected at least 400whp on the dyno and had a suspicion something was up. It ties in with the blowby I observed.

Before you mod the motor to try and bring the power up, change the gears.

Stellar idea, don't fear the gear! I've not yet decided what gear ratio I'll settle on when replacing this 3.08, maybe a 4.10? Need to pick between a eaton trutrac or yukon dura-grip too.

P265-70-17 tire

The non-ppv wheels that came with the car were on 265-65-18 tires. If I wasn't on these 18s, I don't know if the 4pot brakes would have fit under them. Wheels are on the list however. You mentioned going down the track, what size rear tire have you run? Anything in the 28x12.5 or even 31x12.5 range? Trying to get a grasp for what would fit.

If your circle D torque converter is a billet type

It is a billet 278mm converter, part number 07-09-07-2A. I think with my end goal of 6-700whp its a good addition to the build. Even better it came with the car when I bought it. I am glad that the 6L80 was gone through, rebuilt and some choice upgrades done like this converter and clutches. The horror stories I've read about stock converter/stock tune 6L80s blowing up is a bit scary.