Hey guys,

I've been offered a set of 73 mm TBs for the V12. Incl. air filter boxes (I can't use the back plate due to ABS).

The seller says plug and play, but I don't think so... Does it need to be tuned with say an uprated ECU or higher furl pressure etc.?

The V12 uses a very simple EFI (in my opinion) and doesn't have any kind of mix check methode. Introducing higher amounts of air into an engine with no chance of it metering it (no MAF) seems a little risky!? Or am I missing something here? The air temperature sensor doesn't do much...

Cheers

Damien

 

I would not bother. The stock TB's flow about 500fcm each. 500cfm is good for over 600hp.

There are other bottle necks in the intake that WILL release more power/better efficiency.

 

Hmmmm.

Off the cuff I don't see a problem.

With the larger throttle bodies the ECU will provide fueling the same way it always does....in accordance to the Baro sensor reading.

Look at it this way:

Suppose you were cruising along a xxx-throttle opening. The ECU provides fueling to suit. So far, so good. Now, create a vacuum leak or even just open the throttle a bit more. What happens? The baro sensor responds, signals the change to the ECU, and the ECU adds more fuel. I don't see how a larger throttle body would change this dynamic.

The only possible issue that I can see would be at WOT. That is, with larger TBs would air drawn into the engine at WOT exceed the ability of the ECU to adjust injector pulse width to feed the cylinders when demand is at the max. At less than WOT I don't think you'd have a problem.

But I'll do some more mulling...and others will surely chime in

Cheers
DD

 

Would larger pipes into the air filter boxes help? The bloke has the larger bore air filter box lids in the kit... Instead of narrow pipes they are about twice as wide (2x opening size in an oval/oblong shape)...

 

Mine required no added involvement as such.

BUT

The backings needed a larger hole, 2 hours with a file sorted that one.

I also installed real cold air intakes, as in the pick up is from the oval hole in the body behind the bumper bar indicator lamps. A tad crude for the purists maybe, but they work, until a bird got sucked in the LH side at very hi speed, the V12 did not like that one bit. Took some digging out, as it went about a foot up the tube.

BUT#2

The larger discs will foul on the airfilter metal baffle at WOT, sounds like fun, its NOT. So I made my own foam airfilters, and allowed room for those discs to open and then close when required.

THEN

Since I dont run an AAV or a balance pipe, the throttle discs needed
"balancing" just like the old carby set up, glad I kept the balance meter. The throttle stops were the adjustment, and once done and locked, they do not move.

ALSO

I installed a 16CU in the boot, coz I had one, and it just sounded like a top idea.

Apart from that, no mods at all.

All that little stuff woke the beast up seriously, especially at highway speeds and above.

Cold Air Intakes.doc

 

Yes that'll help, the stock intake trumpets are very small. I made my own from 80mm PVC pipe, they are a bit big but I had it left over from my house down pipes. I didn't bother painting them black as I will be changing the intake system to what Jag did on the XJ40 with elbows into the TB, when I change the engine.

I noticed NO difference in performance with these intakes.

BTW my engine builder used stock TB's on race car engines making 500hp it wasn't until 600+hp in the boat that ITB's were used.

 

If you do decide to run cold air in from the side fender make sure you DO NOT terminate the intake inside the fender. It needs to run forward behind the bumper to a high pressure area, or the engine will have to suck harder to overcome the low pressure in front of the wheel.

Here is a good article on the subject

AutoSpeed - Siting Cold Air Intakes

 

Warren,

LUV the downpipe intakes, we Aussies waste NOTHING, HA.

Those tubes on mine do travel all the way down thru that panel, and the "mouth" is right out the front, in the flow as such. That bird was special, I saw it flutter on the roadside, whilst low flying across the Hay Plains, and then it was GONE, and the Beast coughed and spluttered, and dropped into "limp mode" which its too old to have. 45c outside, and I'm trying to dig out that bird, stupid me, eventually slid the hose off the air cleaner snout and sorted the bird in Nerandra.

Just did the same with the S Type, and used a redundant "mouth" on the LH side of the front bumper skirt. Originally thought those openings were for brake air, NOPE, just go into an aperture that goes nowhere. I think? the X202 onwards, have them actually doing something??

 

Doug,

That assumes the throttle plates/bodies are the greatest restriction to airflow into the engine. If the point of greatest restriction is the flow past the valves ( either intake or exhaust) or the manifold runners, then having a bigger throttle body will change nothing in terms of fueling, as it isn't the choke point.

The ECU tends to run rich at WOT anyway, so if it is the choke point and more air can flow through the engine it will lean out some, the question is how much and is it enough to worry about. From what I've read the TB's are not the choke point though.

The one disadvantage that I can see with a larger TB and a MAP metering system is that the manifold vacuum with drop faster for a given throttle opening. This may result in real world increase in fuel consumption without driving any faster. As the throttle opens the ECU will react to the plunge in vacuum and overfuel, then correct back more aggressively than at slower/smaller throttle openings. It may be harder to drive smoothly and economically at slow and city conditions than with the smaller TB. Obviously fast road conditions are different.

 

Thanks for your answers guys. I think I'll pass on these then...

 

Here's what AJ6 Engineering did for air intake, FWIW.

(I just stumbled across this pic so I thought I'd post it)

Cheers
DD

 

Dual snorkels !!! dual everything seems to impress we car guys!!!


My take is that adding airflow may not do a thing, of there are restrictions behind the throttle blades. Most likely the intake ports, followed by the ones for exhaust. And certainly not the exhaust system as a whole. And, cam timing. Duration, lift, etc.


On the whole increases are seen in these before the throttle plate systems is cooler air. air density.


I do have a spare chunk of sown pipe. Intended but didn't fit as I wanted. On the house, that is!!!


Carl


Carl
But

 

Number of points, here:


1. It has been mentioned over and over that the OEM throttles are big enough for even more HP, and so do not need to be enlarged.


2. But AJ6 do offer enlarged throttles, and they do this for a reason: it sharpens throttle response: for a given pedal position, more air is getting in, effectively meaning your foot would have had to have gone deeper with the standard throttles.


3. Power is made from air and fuel. Increasing air does not necessarily translate into more power. Unless the engine is already a bit over fueled (and it is) and the extra air can be used to good effect in terms of power generation. I am not sure on that point, here, but I am quite sure about point 2, above.


4. you can go too far with this: some have fitted quad throttles. This often worsens performance, because the tip in rate is too great and the engine bogs down. But if you have a programmable ECU, you might be able to deal with that.


5. I run the AJ6 SE ECU, and so the fuel map is already tarted up a bit. I had the throttles bored and finished by a machinist, apart from what AJ6 offers. I am pleased with the results.


6. If you fit these, BE SURE you are absolutely certain they do not foul the air filters. Once those disks reach the air filters, they do not return when you let up on the pedal (that is, they are stuck open, until you open the air boxes and pull the filter back to let them close). I made a wire bail that bows out from the throttle face, and pushes the air filter back, so that this cannot happen.