Kingtal0n

So I bought an L98 complete motorswap from transamcreations the other day

and I got a set of ebay turbo manifolds for $250- but I only need one of them.

Im taking a shorty header and making a crossover under the oil pan to feed exhaust into the turbo manifold on the other side- which holds the T4 flange.

The turbo I have selected is the precision 6776, good for between 500-800horsepower.
The L98 engine has reasonable compression iirc for this application. It should handle about 12-15PSI reasonably well and net me the power goal of 450RWHP.

The 92 is down to 3600lbs thanks to hacksaw type removal, but im going to replace the doors and hood and fenders and bumper next should get around 3400 if I am lucky. My goal is to be around 350Z weight (3200-3400) with a driver and a spare tire and toolbox for my daily driving fanatics.

To help the engine breath the 92 has a custom comp cam 224/234 @ .050 hydraulic roller grind for the rev range of 3500-6500RPM, Where I expect this turbo to provide a solid 400~ft.lbs of torque to redline @ 8-12PSI of boost.

To mate this combination to the wheels I am using a 700R4 that I built myself using pro-built performance transmission rebuild kit, everything including the new stator and trans-go shift kit for accumulated shifts.

The converter is an EDGE racing 9.5" with 3200~stall. She should powerbrake right into boost and be a blast to drive.

of course nothing is complete without the right gears. Im going to start with a 3.42 and try different tire sizes to get a feel for how she grips on the asphalt we all drive on. If it seems a bit too laggy/doggy ill jump to 3.73s in a heartbeat.

Yes I am using the stock longblock with AFR 190 heads and some typical fel-pro gaskets. I dont for-see 400ft.lbs of torque being a problem especially with the high quality intercooler/tuning scenario I have planned and the natural medium compression of the L98.

la tee da

Der91Z

iTrader: (1)

Sounds like a stout setup that should see high 9's without a doubt. Have you already purchased your turbo? Precision's new lineup of billet wheel 67mm turbos have proved to be superior over their older lineup.

Kingtal0n

Oh, you give this car way too much credit. It will be lucky to achieve 11's especially with me behind the wheel. What I desire is a real beast on the street. The turbocharger will do pump gas numbers around 500's to the wheels easily with the L98, it will be snappy and responsive, with lightweight components everywhere possible to give the automatic a real grab for the tires when it wants, lowering the boost requirement and increasing the headroom for making that sort of power at the wheels. I am trying to get the loss ratio as close to a fully equipped manual transmission vehicle in other words. even the converter clutches are designed to lockup under FULL THROTTLE.


I am leaving the part throttle accumulation tight as usual, the shift will be firm and short, but it will still have some slip to preserve drivetrain components and the longevity of the transmission, the necessary amount of course :-) remember the stall.


Precision 6776... I use this turbo because I have used it 12 times maybe more already and it has never failed me to make the expected power and live a long healthy life with the right size oil feed/return clocked any which ways.

Orr89RocZ

iTrader: (20)

Keeping stock TPI or doing somethign else there? Cam seems abit big for a L98 with TPI and seems to have alot of exhaust duration for a turbo cam but should work ok.

You will have no problems running your power goals tho and with near 500 whp and that weight, you will be capable of high 10's thats for sure

Kingtal0n

nice catch. Its got a holley stealth ram to help with the VE's, TPI is far too anemic for that RPM you are right.

I am using a very large exhaust side and a large diameter manifold with a T4 flange. Doing this will ensure a very low exhaust pressure ratio, giving the engine a very very flat fun torque curve. We wont be losing VE or getting the air hot since its overturbo'd just enough (on purpose)

Der91Z

iTrader: (1)

I think you will be quite surprised what it will do with a good drag wheel setup with that kind of power level. Pair it with a set of skinnies and a set of 28x10.5" ET Drags and it will put some good times up with some practice.

Jay_rich

iTrader: (4)

Should do high 10's low 11's if done right, I dont think a stock l98 is gonna take 12-15psi for very long unless your tune is spot on.

Also 3.42 will be good DO NOT GO TO 3.73's with a turbo you want a longer gear to build boost. a 3.73 will prob goes thru the gears to quick and not build boost as good.

Start posting some pics!

Also just for reference my 87 ran 11.70s on 411whp.

Jay

Kingtal0n

Those cast pistons are fragile indeed! Yes I have done much research regarding the safety issues of the L98 and its combustion chamber overall. I am really thinking about popping in a set of forged slugs so I can push the limitations of pump gas instead of being worried all the time.

Peak VE once the turbo reaches full boost should maintain VE until 6k~rpm, which means a nice flat torque curve. thats what I am going for. The timing should be between 11-14* for this, with an A/F of 12:1~ or richer. Probably shoot for the typical figure of 11.8:1 for coolness, watching the iat's for any trouble, and the coolants heat sink capacity for an idea of how much heat I am making. after a run, if the coolant picks up a bunch of heat, the next run will automatically have more activation energy with which to initiate combustion, so a second run may be less safe... that is why the setup requires testing, and a good set of heads lol.

my biggest safety factor in place is the head gasket. good tuning, yes, but Ae can surprise anyone. If the heat gets to it, it WILL try and fracture a piston, however, the very weak headgasket should go well before a piston casting goes. I am planning to blow a few headgaskets if I have to, heating this thing up, run after run, trying to beat the air to death to the point where I know its safe.
probably wont spend the $1.3k replacing the pistons unless one of them pops.

lorisk

hey mate,chiming in all the way from new zealand.
i just saw this thread searching for help with my L98.
m also turboing my L98 with a 228/236 cam and a gt3582 turbo
im lost as to what thickness head gasket i need standard being 0.051?..
or if i can stay with what i have. ill be running about 8-10psi and only chasing about 600whp
currently using the fel-pro gaskets.

Kingtal0n

I use LS engines these days. They are basically free here. Here is what I run in my daily, using a free high mileage 5.3 from a local scrap




Build thread in sig for process

lorisk

i wish i was in america haha..ls123 l98 l77 ect are real expensive here.
ive decided to turbo my l98. do i need to run a thicker head gasket? any tips for turboing the ls/l98?

Kingtal0n

Random Tips for turbo projects
1. Cleanliness is the most important thing keep the oil clean, dont touch parts with bare skin like cam lobes or spark plugs, dont leave the engine open for long in the air, pretend its a surgery patient
2. follow service manual and keep parts like factory specifcation
3. You must pressure test from compressor cover through intake manifold (video how to diy in my channel linked from build thread)
4. Evacuate the crankcase using turbo inlet like my picture shows, do not use any catch cans.
5. Replace OEM CHevrolet PCV valve with a Toyota Supra twin turbo 1995-1998 PCV valve because the Chevy pcv will leak boost into the crankcase

You should read my build because I put the other 99 tips in there for how I do everything

Headgasket thickness is practically negligible with respect compression and the downside of a large gap often outweighs the upside of slightly reduced compression so I would go with the tighter thinner head gasket on most engines.

lorisk

just flicked through it now. might get right into that thread real soon!. some of its way over my head but i can see how alot of its going to help.
thank you for replying to a 20year old thread to help me

​​​​​​​picture of my car im turboing

Kingtal0n

That thing looks newer. I am surprised you don't use a modern turbo 2L or 3L engine it would make similar power and be lighter and more simple to work on?

The only reason I went 5.3L LS was because they are free engines around here.
If I had a dime I would have used a 2L or 3L Nissan/Toyota inline sr20det/2jz-gte

lorisk

its a 2007 holden commadore from australia, i think in America its called a pontiac g8
its my weekend car that i take the kids out in, cammed, loud.. and now i want a turbo on it haha.

vorteciroc

I absolutely LOVE this swap!

First off, I really miss many of the Coupes that Japan had here, and the 240sx was great!
Second, that Engine Swap is so unexpected that it has a great Sleeper aspect to it!!
Third, if the exhaust on the car is relatively quiet, it would fool and destroy so many stuck-up Jerks with their newly purchased $100,000 whatever Sports-Car!!!

That looks like way too much fun! ...I hope it has a T56 in it!