So I’d like to include this Dyno graph of my 06 STR. The first picture is the stock power respectively. Car made 328whp/347RWTQ on the first run, and dropped down from there after the 2nd and 3rd runs due to heatsoak.


Second picture is with my Jag having been tuned by alpha jag tuning, and a lower temp thermostat installed along with programming. Second picture is also before I installed the caldoofy intake, as well as having done the cat delete and eventually pulley. These STR’s can certainly make wonderful power, just would check up on yours again.

3rd picture is the most recent run after having installed caldoofy’s intake. Car was tuned before the intake was installed, so it’ll need to be retuned. Even with slightly wheel spin it managed a low 13 second 1/4 mile.


Stock power



Green line was stock power

Yeah, 350 at the wheels is 440-ish at the crank. Yours is in great shape indeed, no wonder it runs those 0-100 times

Certainly so! Even before hand the car made 328whp stock so it seems to be quite stout. Ever need anything feel free to give me a shout or pm.

Thanks. We will investigate and try to solve the issues. Now that I know it's missing a good 100 hp (or actually 140 with some mods on top of a healthy car), I don't want to sell it anymore, just fix it, it should be plenty fast for my needs

That’s the spirit! 👍😃

Gents, how would we go about testing the cats for being clogged? I assume we can't just remove them and do a test run since then the sensors will provide bad data and the car might just run badly anyway? What's the proper way of doing this? I've read that removing cats could actually reduce torque because of the loss of backpressure, but in my case - if they are indeed clogged - could we see an actual improvement?

Also, what about a MAF? Are there some specific readings we should be seeing in live data that would indicate it being healthy or in turn bad?

So when it comes to noticing weather or not the cats are clogged, the way I found out and eventually had them removed was when I was data logging my tuner noticed the boost levels were higher than normal even though I don’t have a upgraded pulley. I’ve got a Bluetooth OBD2 device plugged in, and have an app on my android that we are able to data log with. My sensors have been reading fine, but that’s how we were able to noticed the cats were clogged. I ended up having them removed and I’ll shortly have my car retuned since having them deleted.

Main reason for doing so for me was clogged cats produce a lot of extra heat among a bunch of other pitfalls, so I was concerned they could catch something on fire. As far as seeing an improvement with clogged cats that’ll shouldn’t be the case from what I know. It’s always better to get cats that are either not clogged or just remove them.


Also had a similar issue with the maf where it was dirty due to dirt and such, so I used some Mass Airflow Sensor Cleaner from Orileys or your general auto parts store and that seemed to sort things out pretty well. Didn’t cost me more than $10 dollars for the cleaner & it saved me from having to buy a new sensor.

AS per my sig
Acronyms https://www.jaguarforums.com/forum/s...-jaguar-78910/

There are lots of posts about fuel trims so just read some...

Thanks. No, I meant we might see an improvement with the cats off, even though normally that could reduce torque due to lack of backpressure.

Anyway, next week we'll finally get the chance to record some live data - similar to how you did - so hopefully we'll know a bit more after that. Will also try to clean the MAF first for sure.

Cheers, will do

Sounds like a plan. I’m expecting some positive gains with the cats off as well, especially after getting retuned. Will have to have the car dyno’d again after the current mods.

Cleaning the MAF should definitely help. I noticed a difference after cleaning mine.

Here is another stock STR dyno plot. Does not seem too far off from what you got? 322 Hp with 312 FT-LB TQ?

I drove my 2005 STR for almost 100K miles. A very great car for me but I think what you seeing was my biggest complaint?
Any RWD car with 400HP or so needs a LSD rear end. Otherwise one tire goes up in smoke the RPM's hit the rev limiter and it's all over. Even worse is trying to accelerate from a stop while turning. Then that inner tire is just way too easy to spin. Great torque from that 4.2L SC engine!

So why did none of the Jaguar's in that time era have one? One answer that has been posted was during that time Ford owned Jaguar and Aston Martin. Ford was trying to keep the two separate but they were still very similar. All the AM's got a LSD but no Jaguar's as AM was further up the product line at Ford. Remember this is when Ford was trying to make a PAG (Premier Auto Group) concept. They owned JLR, AM, Volvo and was trying to include Lincoln in this and that resulted in the Lincoln LS which was co-developed with Jaguar's S-Type.
PAG

As we all know Ford just about went broke with GM in 2008 BUT they saved the company by selling off all these recent acquisitions. Note that when Jaguar was sold they immediately installed LSD in most of their car line. We finally got the wonderful E-Diff. Which should have been installed in your STR!!
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I assume that's 322 whp which means you have a healthy 400-ish bhp. Mine was 290 at the crank!

As for the rest, sure, I agree, the car would be enhanced by an LSD but even without one people are able to run 0-100 kph in around 5.5s or a bit lower, which is in line with the factory claims. Mine's almost 1.5 secs slower :P

Right it is possible BUT it will take a lot of practice launching the car. The open rear end makes wheel spin a given so it's a modulated roll of the throttle that's required.
Not easy and you have to keep the car right on the edge of breaking traction.

With Dyno's there is so much variability I don't think 290 is very far from 322? You are down a bit but not much.

What tires are you running on the rear? Size and brand?
I bet with some practice you will improve a bunch.
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Again, your figures are probably whp. You need to divide that by ~0.8-0.85 to get the crank figures, which is right about 385-400 hp. Mine was 290 at the crank. A 100 less than yours, and what it should be.

Yes it takes practice to launch the car well, but when I measured it with dragy I had 3 pretty good launches. It was consistently 6.7-ish, which is only to be expected if the car is missing a 100 horses.

Keep looking and see if you can find the problem? Hard to say as it seems the car is running fine with no codes?
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