WTB p38 Rangie 4.6 lter plenum

[Lucus]

Hey Guys im chasing a 4.6 ltr plenum for my 93. Any ideas where i could source one?


thanks in advance

Luke

[andrew e]

whats the difference between this and a 3.9 one? taller? Bigger intake?

[Lucus]

Bigger throttle body and slightly taller/larger volume (as far as i know) I feel the 3.9 plenum on mu 4.6 is abit small.

[andrew e]

was considering the possibility of making a twin throttle body one, by cutting 2 in half and joining them together, biggest restriction would then be the AFM. Just a thought.

[Lucus]

yeah i have been toying with that idea too. i have a couple of 3.9 plenum's. My main concern was trying to sync two throttle bodies. Im running a wolf ecu with map sensing so i dot actually run and airflow meter anymore.

I've always understood that for best throttle response and torque a plenum should be have a volume thats at least 150% of engine volume. Which for the 4.6 equates to around seven litres. I'm not sure the 4.6 plenum would even go close to that?

[mickrangie]

biggest restriction would then be the AFM.

Get rid of the Lucas ECU and u could run a truck exhaust if you want with only an air temp sensor in it

[Philip A]

If you want torque , fit a Thor.
The runner length is about triple or more than a Vitesse type plenum.
You may lose 10% above say 4000, but you gain about 30% tapering from 1000-3000.
Regards Philip A

[Lucus]

Thanks Phillip. Any idea where you could source one and whats involved in fitting it?


cheers

Luke

[Philip A]

I bought mine on Ebay from a Rover wrecker at Mitcham in Vic. AVO?? They are around. I paid I think $550. Try Triumph Rover Spares in Adelaide.

A bit of fabrication involved
If you use the 14CUX
1 Fuel rail from a Range Rover(only Not Disco) 3.9 with the regulator on the RH rear will fit with a bit of grinding. You can use your old injectors then. The Thor cames with short injectors on a rail without a regulator as its in the tank, and the short injectors run at a higher pressure.
2 Stepper Motor. You have to fabricate a mount and hoses. You can use the alloy fitting from the rear of the plenum, and make a base from nylon bread board, and glue in an outlet pipe.
3. The throttle body is in a different place , so you have to relocate the air cleaner. Fab up a Silicone joiner between the MAF and throttle body with an outlet to the Stepper. You can use the old rubber pipe to match the MAF to the air cleaner. You have to cut off the MAF mount from the air cleaner.
You have to modify the throttle shaft to suit the TPS. Again this involves a bit of bread board. The Thor TPS seems to work differently.

4 . You have to shorten the throttle cable. This is pretty easy.

5 Most expensive part. You have to make a thermostat mount, as the Thor has only a two hole mount for a pipe on the front. I paid a machine shop to make a hole to match the thermostat housing, and make a ledge for the thermostat , and drill the holes. It cost me about $350!!!
You can DIY , but to be reliable I think it is important to have professionally done.
6 Kickdown cable!!!!! You have to fab a longer kickdown cable, and fab an arm to put on the throttle spindle. This is a "D" shape so calls for many happy hours calculating the ratio and drilling a small hole then increasing it with jewellers files. I fabbed the kickdown cable with a bike brake cable, and an intermediate relay. Thanks HSV Rangie!
7 You will probably already have a Unichip or aftermarket injection if you have 4.6 but if not you will need at least a Unichip to trim the fuel.
I think you need another vacuum hole in the manifold but this is just a matter of drilling a hole and putting in a spigot.
8 You need to drill out an existing boss at the front for the injection engine temp sensor, as the 3.9 has 2 sensors, 1 for the gauge and 1 for the ECU.
9 You have to fab up heater hoses. make sure you get the steel heater pipe which goes along the RH of the Thor. This is simple cut and paste.

I think that is all!!!

Unintended consequences!!! I have so much more torque now my torque converter is loose as a goose. At 1800 RPM on the level, if I hit a hill the revs rise to 2200. If I have to remove the trannie again, I will fit a 4.6 converter.
Regards Philip A

[Philip A]

A bit more.
The grinding at the back for the regulator. You have to also cut off the coil mounts .
This is a pity as, one of the things possible if you have a 4.6 block and are using a 4.6 flex plate is that you can fit EDIS at a later date. But when you cut the mounts off, and grind the back of the manifold to fit the regulator, you need somewhere else to fit the coils.
I felt it was worth it as I did not plan EDIS, and it is FAR safer to not break into or modify the fuel system at all.
The beauty of all this work is that ALL the sensors are as per 14CUX, so if you have to order something in the middle of nowhere there are no uncertainties about "what model Commodore is that sensor from????"
Regards Philip A

[DL]

Lot easier just putting a Chev in.

cheers, DL

[cloughy]

Lot easier just putting a Chev in.

cheers, DL

I got one of them I can sell you, with conversion kit to suit either 4 or 5 speed

[Philip A]

Yeah, I agree.
And I have really thought about a Gen111.
Its much easier to fit an engine with all its electronics intact than to update an old one.
I guess my problem is that to have something really reliable you would need about 20 grand.
I am told that To make a ZF live behind a Gen111 will cost about 8K.

The alternative of using a GM tannie is apparently a problem because of overall length and matching to LT230, to get RH side rear driveshaft.
Regards Philip A.

[Lucus]

Thanks for the in depth explanation Phillip. The Thor manifold defiantly wont be going on. I might look into makeing the stock plenum volume larger. i would love too loose the intake runners and side entry plenum for a front entry but at the end of the day i have my 550hp xrt6 ute when i want to go fast. The rangie only has to get me to and from work and tow the old trailer of garden cr@p so i think maybe i need a reality check....