Hey, everyone

Does anyone have experience with modifying the intake duct to 3" or 3.5" diameter? I know mina gallery sells a 3" one but I think that it is too expensive. Could I make one myself using some intake piping with two 90-degree elbows? Would I have to worry about running too lean or any other reliability issues? Since this adds more boost and am thinking of doing a smaller pulley upgrade, would I have to worry about running a higher octane fuel rating to avoid engine knock? What about the Mass Air Flow sensor, would it fit the mod?

I have a 1999 XJR.

Any advise or suggestion is welcomed.

Thanks.

 

do a search there's a number of posts on the subject.

 

Well the one thing you don't have to worry about, is the "adds more boost". Switching to a smooth intake will give a few HP gains, dyno proven by someone else in another thread I think. But as far as adding boost, not really the same as a pulley will. It'll help it breathe for sure though. The MAF might need to have some reducers to fit a 3/5" tube though.

That said, I have the Mina intake on mine, and a K&N filter. I've seen countless posts regarding those style filters causing havic with the MAF sensor, and if I'm completely honest, I can't say that I haven't had issues either. I can't narrow down if it's strictly the intake or a combination of other things, but I can say that I have seen more errors pop up from time to time after the install, than before. BUT, I believe what people are referring to, is the filter more than the intake. I'm going to try to switch back (if it'll fit) to the factory airbox but keep the smooth tube, as I understand that's where the most 'gain' from flow comes.

As of right now, I've been getting a constant 0171/0174 error once a day, but I did put the car in a ditch and might have knocked the intake slightly cockeyed and caused a leak somewhere. It's just been so miserable the last few days that I haven't been able to try to track it down. Is it related? Maybe, maybe not. Too many variables.

All that said, I'd do some regular MAF cleanings and stuff going forward to try to keep a handle on any possibilities, but I do like the results in spite of them.

 

CharlzO,

So would you recommend keeping the original airbox and adding a K&N panel filter (such as this one: Jaguar XJ8-XJR K&N Air Filter 98-03 4.0L, Eurotoys,Ltd.) instead of a cone filter, and then just modifying the intake duct? I want to keep it reliable, as it is my daily driver.

As for your problem, isn't there a method for finding leaks? I think there's one where you can use smoke or something like that, not sure if it'll work since there is a lot of ventilation under the hood even at idle.

 

K&N filters do zilch for power gains.

 

Right. The people that have mentioned issues, it seems to come back to more of the oil in the filter gumming up the MAF more than it does the style of filter. Just get a nice hi-flow factory filter for the box. There are ways to try to eliminate some of the sound-deadening tubes that branch off the air box, but you'll get more result from the smooth tube.

For mine, there are ways where you can spray nearby, carefully, and see if there's a change in the engine response. It's a project for whatever sunny morning I can find this week. I'm 90% sure it's just a leak somewhere, but I really did bounce around so who knows lol

 

Erasmo, a few things you might want to consider, Engine knock is an issue when you live where you do, I'd not bother with a cone as this doesn't help drawing cold air in the way the standard box does unless you fabricate a sealed surround like a few have done on here.

Having a larger bore induction tube needs thought from were the air is drawn and into the throttle body - have a search for max bore as some owners run 92mm TB's.

Modifying the airbox cold air snorkel, along with a good panel ITG/K&N etc - standard MAF fitting to a step up diameter pipe to the induction tube and onto the TB shouldn't be much of a job.

I'd say go for the upper pulley, again plenty of tips and pictures within threads all over this forum, XKR-XJR-Engines forums for all the info you'll ever need. There's twin screw conversions, water/meth kits / killer chiller kits, and some all on the same car. What I'm trying to say is, it's all been done before, and well documented on here.

Hope this helps.

 

CharlzO,

I ordered the K&N high flow panel filter, along with some 3.5" tubes and bends. I will attempt to assemble a new intake using parts from siliconeintakes.com and intakehoses.com. I also ordered an OBDII Bluetooth device that should allow me to read Mass Air Flow readings, so I will measure the difference after the installation and will document any findings, should everything work out.

 

Sean,

I did some reading and yeah, it seems like keeping the stock airbox is the better choice. But I noticed that some of the reliabilities concerns were not directly addressed in other threads. I might also do the bigger cold air snorkel as you suggested and maybe the pulley later when the money allows.

Thanks.

 

I know there are many threads on upgrading the stock intake tube, but here is my documentation:

I bought some 3.5" tubing and constructed my own intake.
Here's what I bought:
2X(3.5" ID 6in straight tube): Intake Hoses, IntakeTubing, and Intake Clamps - Intakehoses.com Silicone Sleeve 3.5" ID X 6" Long - Gloss Black
2X 3.5" 90 deg bends: https://www.siliconeintakes.com/hols...-90-p-416.html
1X 3.5" 30 deg bend: https://www.siliconeintakes.com/30-s...30-p-1089.html
4X 3.5" steel joiners: https://www.siliconeintakes.com/turb...ing-p-380.html

Along with some black duct tape, a very sharp box cutter, a 3/4" vacuum hose, 4 hose clamps, some plastic connectors (from autozone), and some zip-ties.

I had to mash 2 of the steel joiners to make them oval-shaped for it to clear the hood; otherwise, the hood will not entirely close and will dent the hood (learned first hand). I also used the factory throttle body gasket except I had to cut the lip a bit for it to fit properly. I used the factory connector to the crankcase for the ventilation and cut the rest of the tube off and attached a 3/4' vacuum hose to the factory connector and at the other end, I attached one of the plastic connectors I bought from my local Autozone. I cut a small hole with 4 small cuts to the outside of the circle for it to fit.

The total cost was about $180, with about $30 for the supplies and about $150 for the parts plus shipping. I also took me about 5 hours to get everything the way it is now, and it still could use a little more refinement.

Overall, the inside isn't completely smooth due to the steel joiners, but it is a lot bigger than the stock intake. Performance wise, it does feel quicker from about +45 mph and the sound of the supercharger is slightly more pronounced.

Lastly, I bought a high-flow K & N panel filter from ebay.


Any suggestions or question are welcome.

 

https://www.jaguarforums.com/forum/x...-%2430-165898/

This is what I did. Around $30 for parts.

 

jackra_1,

Looks good, and very inexpensive. I didn't really know where to look as far as intake tubing so I read somewhere in the forums to check out silicone intakes.com so I automatically went there, and the prices where a bit more compared to the ones you found on ebay. I do feel like the intake for the x350 is very simple compared to the x308 intake.

 

AZjag, welcome to the world of 'marginal gains'. You've addressed one bottleneck, there's also throttle body, exhaust and pulley mods.

 

As a thought along the lines of an intake change... The Lincoln LS and the later V8s (like S Type, X350, ...) had the throttle body at the front of the engine. So basically the intake manifold spun around by 180° and the thermostat housing moved...

Would something like that aid? I mean, between the TB and the air filter is like a 70 cm long tube... Surely that can't really aid power... Also the placement of the TB at the rear of the engine isn't of an advantage... Maybe adopting the LS/X350/S-Type intake might do some magical tricks?

 

AZjag1999. After I posted I realized your x308 intake was quite different so you did a good job!

Most people do this sort of mod to hear a little bit more "whine" from the SC as any power gains are only achieved at high rpm.

I have done about as much as I can on my X350 in the way of mods and have learned a lot from others on this forum.

My biggest bottleneck is the fact that the TB is in the rear of the engine and sits on an "elbow" with a 90 degree bend into the rear of the SC.

This has been discussed quite a bit in "quest for 450 hp".

 

Sean,
Yeah, I might look at doing an upper pulley upgrade and possibly supercharger porting. Thanks.

Daim,
A smaller distance from the filter to the throttle body would help some, but I don't think that would be possible with the way the AJ V8 engine is designed and the lack of aftermarket parts regarding manifolds and TB's.

Jackra,
Thanks. And yeah, that was kind of my reason for doing it, just to hear that whine a little more. As far as your x350, would you be looking to port/bore your TB, or is it just poor design from the manufacturer and you can't modify?

 

Others have enlarged their TB on the X350 I believe however that still leaves the 90 degree elbow underneath where it joins/mates with the SC inlet as the bottleneck.

I did some minor porting here but it really is negligible in real world terms but I did it, because I could, while I had everything apart.

Cleaning out my charge coolers almost certainly had a huge effect.

 

There's no space at the front end of the car under the bonnet on the X308 for that (or the X150 XK for that matter- which is why the X150 stuck with the rear fed throttle). The XK/X150 had some detail mods, and even the X100 4.2 did (still rear fed) that lowered losses- not quite as low as the front fed X350 and X200s but still worth having.X150 XK 4.2 S/C went for twin air boxes with twin MAF