Twin Turbo V12 planning stage
 

I have been thinking about FI for my baby for a while now and thought I would post up my thoughts and ideas for you all to comment on. This will be a 2011 project and at the moment I am in the research phase only.

I did consider supercharging but I don't want the 40kg + for 2 SC and a single SC would require new intake manifold fabrication PIA. So turbo it is.

The patient - 1989 build XJS V12 with marelli ignition, dodgy spark plug leads and questionable cooling. Oh it has ABS as well.

Phase 1
Will consist of an engine freshen. Bottom end new bearings gaskets etc upgrade the cooling and anything else that requires attention.

Lowering of the CR to 9.0-9.5 - I am planning on retaining the HE heads and either enlarging the chambers or new low compression pistons (Guys please chime in here).

Upgrade of the ECU and ignition Wolf, Haltech there are loads of good ones out there. If I'm feeling lucky I might even venture down the Megasquirt route.

General tidy up of the engine bay new injection harness - injector plugs are very brittle and anything else that needs attention.

Phase 2 this is the business end of the deal

Mounting 2 turbochargers on the stock manifolds. I guess I will learn how to weld.

After a little research I think the TD04 13 T turbos from the 2.5L WRX would work well between 2000-5500rpm. the compressors can flow 360CFM each which is enough for nearly 500hp. Not the ideal turbo's something a little bigger would be better but these are very common on the used market here in OZ with the guys upgrading their WRX's.

My other option is a T3 from a Jap import Nissan I will wait and see what is available at the time.

I guess at this point I will be upgrading rear cage, wheels tyres etc etc etc


cheers Warren

sounds like you will be busy.

most what you say is doable, IMO, the HE heads dont flow well, and are a big bottle neck for heat transfer into the coolant, causing over heat probs,especially for a turbo engine for a longer time period and the long exhaust port is a small steam boiler.

compression around your 9 to 1, is good but taking metal out of chamber will only make heat probs worse, and a low comp piston will be trickey because of the chamber shape.

a usable head would be the flat chamber from 72-79, much better control of heat(with a good cooling system) lots of info out there for same.

aftermarket ECU does away with Marrelli any way.

2.5l turbos sounds good, by two= 5 L.

injectors from early FI engines flow more fuel, than HE inj.

and if you are gonna learn to weld on a project of this level,, GOOD LUCK!!!!!!!!!!!!!

but YES go after it, the fun and learnin curve will be admirable.

just wondering...

What is your application for this awesome project?

grabbing popcorn

a car of course. LOL,, LOL

My originally thought was to use pre-HE heads until I found the Twin SC XJS of Bradly Smith this retained the HE heads and made well over my goal of 600hp. Having said that I am still open to suggestions and may go the pre HE route.

I am planning on buying a second engine to do the fabrication work on but Jag V12 engines are not readily available here in Aus, so I might buy an old XJ12 S1/11 for the motor. This will give me the flat heads....so who knows

I have done a lot of research on different turbos and the MHI TD05 16G are almost a perfect fit (original for EVO and STI).

I was going to keep the original injectors and add supplementary injectors in the plenum. My reasoning apart from the obvious is charge cooling. Moving the injectors to the start of the intake runners will cool the intake charge. I had a turbo Commodore in my younger days and we used this same approach. After a number of dyno runs the intake runners were so cold they had condensation on them.

Yeah the Marrelli will go

Because I can I love power and I love my XJS :icon_razz: what a combination

Certainly an interesting project!!

I cant wait to see/hear updates on the project!

While you are at it, I suggest you replace all the old wiring.

Solder the connections instead of using connector plugs.

That cleaned up up a lot of electrical problems with my V12.

update?

There will be no twin turbos in the foreseeable future. Mostly due to the NSW Government trying to introduce legislation to almost outlaw modified vehicles. The mods will now under the skin so I keep my original engine number, NO inspection required.

I do have a spare 94 6.0L engine, which is now in bits. My plan at this point is to rebuild my engine with the 6.0L rotating assembly and heads, using the 5.3L cams (These have more aggressive ramp and lift than the 6.0L).

Balance rotating assembly as a unit. Lighten conrods by removing some of the bigend balance pad and then weight match rods and pistons. CC chambers and muliangle valve job.

Ceramic coat pistons, chambers, valves and exhaust manifolds. Smooth and blend intake ports in head and match them to the 6.0L manifold. Enlarge exhaust manifolds and port match, then dual 2.0"x26" down pipes into 2.5" exhaust. All flanges will be pined for alignment.

Keep Marelli ignition hardware (dissy and ignition modules) but replace the 2 ECU's with a MegaSquirt. This will be installed before the engine is rebuilt so I can start both phases of the project with a working engine and electronics. I will also re-wire the engine bay and re-locate all fuses and relays to a single module.

The problems with the turbo manifolds is you need something like what the new nissian GTR has where the hotside is part of the manifold. You need a well built log manifold. But that is just SO MUCH HEAT.

We are doing an accord at my job and we are have to go way overboard to keep the turbo from melting all the electronics in.the engine bay. You could pipe a real low forward mount and jeep it.under your bumper to the side of the subframe. But that also is a ton of complexity.

Warron, I would try to sit the turbo either behind a headlight, or on the underside behind the oil filter.

pix of a GTR custom turbo set up ,done back in 2010! 3.8L V6

car made 850hp 1st time on the dyno,after a day of tuning that is,many hours.

heat can be controlled, not much of a problem with todays insulations and coatings!

if turbocharging was not practical it wouldnt be in many of the new factory cars, and race cars, i know people who have over a 100K on turbo cars