The STR application may never be able to fit a 90mm throttlebody. If we could, I'm sure the answer would be 90mm upgrade for certain, but I think we are limited to modified stock throttlebody.

 

Wow, I didn't know that!

Reason I asked was because, on Avos's twin/screw write up, he includes the STR and goes on to say that Stage 2 kits include a 90 mm TB.

If you are correct, 220 HP will not be achievable with the T/S upgrade on the STR. So, what can we hope for? 140? 150?

 

Maxbore does create a new butterfly, but mine went from 75mm (stock) to 78.5mm

 

Guys I think you'll find there is a bigger TB from Maxbore already available.

So there you have it, 82mm.

 

Good to hear he is a Jaguar specialist, that can help.

You do get a new butterfly to match the new diameter, but there is no extra coating. As far as I understand the coating is there to lower the chance (i.e. extend the time) of carbon buildup. On EGR systems you do get a lot of it (probbaly due to the oil mist from the engine breathers mixing with the hot exhaust gases), just have a look in your TB already now, you'll be surprised. On the new intake system it will probably take much longer before that can happen, and now it’s also easy to access, so cleaning (if it does happen) is easy!

As said I am not sure what the maximum is you can get out of the system until I have finished the setup and done a dyno at least. It’s not that the 82mm will not bring you far, it’s just that with the 90mm version you can go further as that one at higher airflows has less restriction, so you can push it even further with pulley changes. To fit a 90mm, much more would be required, lowering the engine or increase the bulge in on the hood for more room, so that’s not worth the effort imho. The bored out 82mm stock TB is a big step over the stock 75mm once you suck more air thru with the KB unit.

The 82mm is a special order, as it is really the max you can go, so the unit must be handled with care.

I have in the meantime also updated the 1st page with more details, the Stage I and II parts where not for the STR.

 

Thanks Avos, I have now checked the Maxbore website - they don't specifically mention the STR, so I assume the TB used in the XJR AJ26 engine and in the STR are identical?

Your Stage 1 details call for the bypass valve to be returned as a core. Is there a chance that the final Stage 1 kit might also include the TB as a core exchange?

 

Very exciting stuff. 82mm upgrade through maxbore is great news.

I was considering upgrading to an 07+ XKR in the future, but with this TS kit on the horizon, I am very tempted to just keep my STR...

82mm throttlebody, ts kit @ 21psi, methanol injection for fueling supplement, 500whp should be possible on a 4.2L. What do you think avos?

 

does anyone know , or has it been mentioned as to the price of the twin screw for the STR should they become available?

 

No the throttle bodies are unique to the 4.2L STR and XJR (and XF). Completely different and incompatible to the earlier 4.0L engines, and even the 4.2L XKR is different again.

 

The TBs are totally different as Cambo also pointed out, its just accidental that they can be bored out the same.

Once the kit is done I will setup a special section for the 4.2 STR and 4.2 XJR, there is no need for the bypass valve to be returned for these models.

 

I think 500whp could be possible, but that may require some extra mods or higher pressure, but lets see how far I 1st get

 

Avos, I have a 4.2 XF. Will the STR kit fit my car? Or are you gonna tap into that market? Also , would boring out my throttle body have any benefit on my car without your kit? Thanks!!!

 

The STR kit will already fit the 4.2 XFR, and its certainly something I could do. But I would need to have a car here to do a 1st.

Boring out the TB for a stock setup would make little effect imho.

 

I apologize if this has already been addressed, but how will this affect the lifespan of my car (2001 XKR) if I were to have this installed?

 

It obviously wouldn't increase it, but as with any tuning, it becomes more critical to be alert on any issues you may have as with the extra power consequences can come quicker. Equally important is good maintenance and care, i.e. never floor the car when the engine oil isn’t up to temp yet. Last but not least, it will also depend on how you use the power, i.e. only street (meaning relatively short bursts of power, less demanding on the engine), or on the track (meaning long time of full power, more demanding on the engine).

I drive only on the street, but do several wots a day. On my original 4.0 engine I drove about 50Kmiles with TS setups, after 125Kmiles I swapped the engine (which was still in perfect shape) for a 4.2 engine. That one I have driven now for 115Kmiles with about 475-525 rwhp in that period.

 

Hi Andre,

How's the twin screw kit for 2008 (new shape 4.2) XKR coming along?

Thanks,
Neil.

 

Am still in preparation phase, one of the things I want to do is to add bigger injectors for the newer 4.2 XKs. I expect to receive them next week, and will install them quickly afterwards on my car and test them out.

 

Just found this thread and Iam shocked.
Sending a PM...
Anyone have this on 4.0 XJR already?

 

I've been waiting for this kit.......

 

I have received the new fuel injectors yesterday and have installed just now on my car. So far so good! Will do some good driving the next week to see how it works out.

@Bfarrell,
Am still commited to make one and the injector testing will be part of the of it as well.