Hello Everyone. I'm considering boring out my 03 XJR's throttle body for more HP gains. Has anyone done this? If so, what documented Dyno improvements did you see (HP gains, Torque gains, low-range, mid-range or top end etc.?) Also, what was you final bore out measurement over stock?

 

Mine went from 75mm stock to 82mm. 19.56% more surface area.

Sorry, no before/after dyno.

 

I've got a new TB on it's way from ASI, and I'm going to get Maxbore to bore it out before sending it over.
I'll keep you posted on the results

 

I've actually had Maxbore do 2 TBs for me.

The first went from 75 to 82.5mm, and the 2nd from 75 to 82 mm.

As I said before, no dynos, just a video taped run of 0-100 mph in 10.5/6 seconds.

Getting the Eaton to breath properly is what it is all about. Good at moving air, not so good at compressing it...

By having the 92mm MAF, big intake, and ported all the way through-ported tb, elbow, blower, intake manifolds, and even a little on the charge coolers, I was getting a solid 18 psi with a stock upper pulley and just a +4 lower while spinning the blower only 14,500 rpm. Given my boost was still climbing at red line, it pretty much proves it was not starving for air.

 

Please do a before and after DYNO test to see if you made any HP/TQ gains!

 

You get gain only if 75mm is too small for your setup and it's your bottleneck for air flow. Better that you measure your current intake vacuum before and after Maxbore. One TS kit got 70% intake vacuum decrease, which meant boost of two more PSI = 20-30bhp. Most probably engine with Eaton gets less benefit since it's smaller and requires less air. The next question is the MAF size.

 

Sadly I missed out on going to a dyno day just the other week as I had other engagements
I will see if I can organise something though, as I'm also keen to see if it makes a difference

 

Throttle body should be with Maxbore now
Just a question, do I need to buy a new gasket, or are the old ones reusable? Would rather know in advance, rather than being charged ridiculous amounts for a genuine gasket by the local dealer

 

You are going to have to grind away some of the inside of the gasket to port match it.
I just reused this gasket, but used a small amount of black silicon to seal it on both sides for cheap insurance.

 

Sweet. The local Jag dealer will be doing the work, so I'll just talk nicely to them about it.
It's a pity I can't get the elbow ported to match too, but I don't have the gear to change the TB myself, so have to get it done there

 

You get reusuable gasket matched to new bore from Maxbore. Cost $10.

 

Anyone know what Max bore charges? I am sending my M112 off to be rebuilt soon, and would like to get my TB done at the same time.

 

Two years ago AJ26 TB: $225 for the TB boring, $10 for the gasket, $35 for the shaft . 2012 he charged same $99 for all single TBs.
Maxbore.com throttle body boring service
http://www.maxbore.com/index3.html

 

Just a point - water dragon - silicone is not great with engine inlet, or pressure - Master gasket (515) is rated up to 0.5mm at 3,000PSI - and resistant to most fluids -
I ditched all inlet gaskets when it was match ported. (except bellows and Kennebell outlet gasket.)
General comment, I have just spent AU50K on a AJ 26/33 the smallest area in the inlet is the rectangular area at the inlet to the intercoolers. From memory mine were 95mm X 25mm = surface area of 4750mm square
TB before it was bored was 4500mm square - after bore 5130mm square -
I have altered the inlet to the intercoolers now over 5500mm total area -- I run a 3 1/2" cold induction - with a 3 bar map, and aftermarket ECU
I never did a before and after on the TB - because it was done in conjunction with Kennebell and lots of other mods.
I seriously doubt much of a performance increase by just boring a TB - the inlet to the Inter coolers is only 250mm square larger than a standard TB. in reality, you are only gaining about the size the finger nail on your ring finger (15mm X15mm)
Assembling top end this weekend
Cheers

 

Yes....finally.