I recently purchased an S-Type R with only 26.000km and full service history at Jaguar (verified).

If on "P" (neutral) and engine at normal running temperature I accelerate to approx 3000rpm a few times (like 1 acceleration each 2 seconds... you know the rumm... rumm... rumm... ) and on deceleration I hear like some small "explosions" (like a small backfire) apparetnly from the engine bay, like if unburned petrol were ingniting.

I do not hear that noise when on the road...

Is that a problem or "normal" in this car?
have any of you experienced it?

I found this page:
What is Car Engine Backfire Through the Intake or Exhaust - 2CarPros

could it be a preassure leakage somewhere creating an intake manifold backfire?
does any of you know if the STR is prone to a particular type of preasure leakage or frop in fuel preasure?

Thanks!

 

Doesn't appear to be normal but I don't know what it is - however, sounds are very hard to figure out without a recording.

 

bean burritos have the same effect on me...

 

Jorge,

I read the article and found to use incorrect or misleading terminology and deals with older technology not present on modern cars. A 'popping noise' out of the exhaust is an afterfire, not backfire.

In your previous post on this subject you mentioned the noise was coming from the exhaust. Now you think it's coming from under the hood.

Please clarify.

 

You are running into the rev limiter. Jaguar has placed a limit in P and N of 3000 rpm. Hold the gas pedal all the way to the floor when in Park. The engine will not exceed 3000 rpm. All the strange noises you hear are from this. You don't hear them on the road because the car now has different rev limit which is supposed to be 6100 rpm.

All perfectly normal and nothing is wrong.
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Many thanks! I didn't know that it had a rev limiter on P. I knew that the A6s have it but my other Stype (3.0L V6, on sale) doesn't have one

Thanks again!

 

So..... How do you like it so far

 

Would a rev limiter cause it to pop? Could it be an aftermarket exhaust?

 

tbird hit the 3000 rpm "rev limiter" on the head. The back-popping from the exhaust is the ECU igniting the unburnt fuel upon the next cycle as a means to not foul the plugs/chamber/wash down the cylinder walls. It was jagv8 who enlightened me to this last year when I was a new comer and concerned about the revs in neutral.

 

The noise can be caused by many things. When the engine rpm is limited or cut back it can be done several ways. You can kill the ignition or cut off the gas. Since the STR has an electronic throttle this gives Jaguar a third method by chocking off air flow. But I really don't know what method or blend of methods is used.
Does anybody know how Jaguar limits the rpm??
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I never knew the rev limit causes popping (but yeah I'd read about the limit). Interesting.........

 

Well, it is a big change from the 3.0L V6 manual Stype I still have It seems quick but the problem is that I haven't had the chance to really test it well yet.

One thing that my wife gets a bit nervous about, at least at the beggining, is the whining noise from the compressor when accelerating and the downshifts...

That is also something that I still have to get used to. It is the first time that I have an automatic, and not having full control over the gear change is a bit strange to me. I find some times that it would have been faster if I had shifted myself instead of waiting for the computer to decide shifting. The thing about manual gears is that I can shift in advance of what I'm going to do. For example when overtaking in automatic the computer downshifts once I start accelerating but if I had a manual I would shift before starting the overtake so I can be much faster.

The other option is to use the left side of the J-Gate to simulate manual... but I find it too "soft" and too easy to jump from 4th to 2nd if you are not very careful with the shift. Do you know what would happen if I shift from 4th to 2nd when still going too fast for 2nd? will it over-rev or would the computer not allow to engage 2nd?

Don't know, automatic is ok, but I would have preferred a manual if they had existed, really... I'm planning to buy a Porsche 996 turbo may be next year... with this experience I know now that I want it manual

Well, let's see if I can really test it well, (without my wife on it ) and I can give more feed back.

 

With the power it has I'm surprised you find it an issue. Have no worries about the J-gate (which sounds looser than mine) as the car will protect itself from over-revving.

 

Sport button will quicken shifts, J-Gate isn't the best manumatic but really with the power in this car, overtaking really doesn't require much in the way of messing around. Hammer it and hold on.

 

May be it is a psicological thing, after 22 years overtaking with first a reduction preparing for the oposite lane to be clean and then accelerating when clean, mind you that I do it also with the Porsche 964 with 272cv which has a 0-100km/h of 5.4s which if I do not remember wrong is the same than the STR.

So it is quite a mind change to just accelerate without the previous reduction. Also I don't know if I'll take the STR to a track day ever... may be it will be interesting to time a couple of laps with the 964 and then with the STR... but I guess that the extra weight will penalise it significantly.

If I ever take the STR to the track I'm not sure how I'll manage the gear changes... would it make the reductions when braking hard before the turning and would it keep engaged the correct gear when I start accelearing in the apex?

Has anyone here taken the STR to the track? Any comments?
By the way I guess you all have seen the STR accident in a track when driven by a professional...

Cheers

Jorge.

 

Hi Jorge, I know what you mean - I always preferred a stick but without one available for the STR then it is what it is. Hard to give you proper advice since everyone drives a little different, but in my experience the STR will reduce gearing as you slow when in Sport, not as much as you would like and the timing can be nebulous however. This is where I would take matters to the J-Gate and manually shift.

The weight is a pretty hefty penalty you are correct, you'll notice a good bit more tire scrub than you are used to in your Porsche. Once you clear the apex and hammer it, she will go though.

So you'd want to tinker a bit and figure out what you like, and if you want to keep DSC on or off while lapping.

The traits won't be very similar to your Porsche, but that's not really an expectation.

I've tried to forget about that horrible accident!

Best of luck!