DIY Modification to Improve Performance and Fuel Economy of AJ16 and AJ6 Engines
#282
#283
Join Date: Feb 2014
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Hi Fazakerly,
Your symptom of extended cranking at startup may be associated with a failed or failing fuel pressure regulator (FPR), a very common issue on Jags. The FPR works in conjunction with the fuel pressure check valve or non-return valve to maintain pressure in the fuel rail, but when either the FPR or check valve fail, the fuel pump must repressurize the system at every startup, causing the extra cranking time.
Unfortunately, I don't think the X300 has a Schraeder valve on the fuel rail for attaching a pressure gauge. You can assemble a pressure gauge test rig to see how quickly the pressure in the rail is leaking down, but it's easier and less expensive to just replace the FPR. They're commonly available for as little as $40 on ebay, or about $80 for an OE Bosch if you shop around.
I think the check valve on an X300 is built into the Evaporative Loss Flange on the top of the fuel tank, so if the check valve fails, it is easier to just add a new check valve in the fuel line outside the tank.
Let me know if you're interested and I'll post links to photos of the FPR and adding a check valve in a new thread.
Excessive cranking can also indicate a crankshaft position sensor (CKPS) or camshaft position sensor (CMP) that is past its prime.
To make up for highjacking the thread about Andy's brackets, I'll add my endorsement: I installed his bracket in our '93 about 18 months ago and it's never coming out (unless I sell the car)! 0-60 times didn't change, but the engine revs more freely in the midrange and we gained 1-2 mpg in fuel economy. "The biggest no-brainer in the history of Earth!"
Cheers,
Don
Last edited by Don B; 06-30-2014 at 03:51 PM.
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XJ-Executive (09-10-2016)
#284
#285
As usual I didn't explain myself properly ....I wasn't concerned about slowing down the cranking speed, only that I recall from my Model T days that it was retard to start, advance to run....and that if I over advanced then starting would be harder ......because spark was occurring much too early ....
#286
#288
Just received and installed my bracket yesterday. (97xjr6) Had to do a few steps twice... took maybe two hours because of that, and that I cleaned the parts while they were out of the car. I didnt do a dyno before. I was excited to put it in. I did a standing start in the same place I always do them and the tires were broken free for more time than usual and it reached 60mph in a noticeably closer distance. Still zero chance for a tire slip during 1st to 2nd. It is nearly 10deg hotter and much more humid than last standing start I did. So performance may be even more so with better air. Around town I feel like the engine response is "lighter and more free" than before. And it seems to respond differently to how it handles shift points. Not so much where they are... but they seem to linger around more with light throttle if that makes any sense. Cold or warm crank time did not change. . I am glad I made the purchase. I am not used to the around town throttle yet. I feel like I am hunting for spots of torque that I used to know where they were. It may even be that it matters less now. Can't tell yet.
Last edited by swaschka; 07-01-2014 at 01:34 PM.
#289
Just received and installed my bracket yesterday. (97xjr6) Had to do a few steps twice... took maybe two hours because of that, and that I cleaned the parts while they were out of the car. I didnt do a dyno before. I was excited to put it in. I did a standing start in the same place I always do them and the tires were broken free for more time than usual and it reached 60mph in a noticeably closer distance. Still zero chance for a tire slip during 1st to 2nd. It is nearly 10deg hotter and much more humid than last standing start I did. So performance may be even more so with better air. Around town I feel like the engine response is "lighter and more free" than before. And it seems to respond differently to how it handles shift points. Not so much where they are... but they seem to linger around more with light throttle if that makes any sense. Cold or warm crank time did not change. . I am glad I made the purchase. I am not used to the around town throttle yet. I feel like I am hunting for spots of torque that I used to know where they were. It may even be that it matters less now. Can't tell yet.
The throttle/accelerator cables are well adjusted now, so that's not the issue. Wonder what would cause that initial hesitation?
Received my bracket this week too, thanks Andy! I haven't put it on yet since doing so on the SC engine takes about 2hrs based on his instructions. So that will be a weekend job. But look forward to the results!
.
#290
my 97 XJR will only spin the rear tires on a wet road. In fact, if I just "floor it", there is a very brief 1/2 second hesitation before it spins up... kind of similar to if the accelerator pump on a carb'd car weren't working quite right.
Ill be interested to get your feedback on the bracket. I drove the car around town 3 times today. I will say it makes the car feel lighter. power comes on seemingly a touch before the blower is whistling. Most noticeable to me is the way the car pulls with light pedal pressure from 50-70mph. You gotta figure even if it gave you 30hp thats just under 10% of what you have. so its prob not going to melt your tires. But I would say the bracket is akin to shaving some weight off the car. As many have said before. Your not going to find another mod for less that will do the same or more.
#291
I have posted this much earlier on in this thread,
but the Stoddart bracket is nicely complemented by a pod filter.
The old airbox is easily removed (and kept for later if needed) and replaced with a pod. It then breathes better at higher revs, and makes a nice muted induction noise that you don't get with the airbox (the narrow diameter pipe into the box keeps it quiet but also limits flow..)
I think bracket plus pod filter really livelies up my 3.2
but the Stoddart bracket is nicely complemented by a pod filter.
The old airbox is easily removed (and kept for later if needed) and replaced with a pod. It then breathes better at higher revs, and makes a nice muted induction noise that you don't get with the airbox (the narrow diameter pipe into the box keeps it quiet but also limits flow..)
I think bracket plus pod filter really livelies up my 3.2
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XJ-Executive (09-10-2016)
#292
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I have posted this much earlier on in this thread,
but the Stoddart bracket is nicely complemented by a pod filter.
The old airbox is easily removed (and kept for later if needed) and replaced with a pod. It then breathes better at higher revs, and makes a nice muted induction noise that you don't get with the airbox (the narrow diameter pipe into the box keeps it quiet but also limits flow..)
I think bracket plus pod filter really livelies up my 3.2
but the Stoddart bracket is nicely complemented by a pod filter.
The old airbox is easily removed (and kept for later if needed) and replaced with a pod. It then breathes better at higher revs, and makes a nice muted induction noise that you don't get with the airbox (the narrow diameter pipe into the box keeps it quiet but also limits flow..)
I think bracket plus pod filter really livelies up my 3.2
Hi AL NZ,
That's a very good point. Just to add another option, a compromise between the stock airbox and a pod filter is to simply replace the air cleaner housing inlet snorkel with a straight hose. It doesn't exactly double the airflow as I put it in my photo album at the link below, but it does make a significant improvement while preserving the more effective filtering of a good paper filter as well as the cold air supply of the air passage through the fender/wing:
Welcome to Jag-lovers - Members Photo Viewing Page
Cheers,
Don
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XJ-Executive (09-10-2016)
#293
Hi AL NZ,
That's a very good point. Just to add another option, a compromise between the stock airbox and a pod filter is to simply replace the air cleaner housing inlet snorkel with a straight hose. It doesn't exactly double the airflow as I put it in my photo album at the link below, but it does make a significant improvement while preserving the more effective filtering of a good paper filter as well as the cold air supply of the air passage through the fender/wing:
Welcome to Jag-lovers - Members Photo Viewing Page
Cheers,
Don
That's a very good point. Just to add another option, a compromise between the stock airbox and a pod filter is to simply replace the air cleaner housing inlet snorkel with a straight hose. It doesn't exactly double the airflow as I put it in my photo album at the link below, but it does make a significant improvement while preserving the more effective filtering of a good paper filter as well as the cold air supply of the air passage through the fender/wing:
Welcome to Jag-lovers - Members Photo Viewing Page
Cheers,
Don
I thought I had also noted someone fitting a smaller cone filter INSIDE the airbox, which may (or may not) have more surface area than the panel filter.
.
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XJ-Executive (09-10-2016)
#294
my approach to the filter has been basic:
Resistance to flow is proportionate, amongst other things, to length of pipe. So I put my cone straight on the intake where the airbox coupled, just in front of the flow meter. This does put the pod back a little from the 'cold' spot behind lights and the hole through into the wheelarch. I doubt there is much flow in the wheel arch however, just a lot of turbulence. I think long hoses/pipes to the wheelarch will introduce some resistance to flow at full throttle.
I think at open road speeds there will be enough flow through the headlights to have reasonably cool air around the pod. The exhaust is on the other side of the engine. On my humble 3.2, there is no supercharger heat source.
I think a flat panel filter has less surface area then a cylindrical pod with a second inner surface.
Of course, this is my uninformed opinion. I have made absolutely no measurements of any of this.
It also happens to be the easiest, laziest option!
Resistance to flow is proportionate, amongst other things, to length of pipe. So I put my cone straight on the intake where the airbox coupled, just in front of the flow meter. This does put the pod back a little from the 'cold' spot behind lights and the hole through into the wheelarch. I doubt there is much flow in the wheel arch however, just a lot of turbulence. I think long hoses/pipes to the wheelarch will introduce some resistance to flow at full throttle.
I think at open road speeds there will be enough flow through the headlights to have reasonably cool air around the pod. The exhaust is on the other side of the engine. On my humble 3.2, there is no supercharger heat source.
I think a flat panel filter has less surface area then a cylindrical pod with a second inner surface.
Of course, this is my uninformed opinion. I have made absolutely no measurements of any of this.
It also happens to be the easiest, laziest option!
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XJ-Executive (09-10-2016)
#295
#296
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Hi Al,
If you can get a torque wrench in there and read it, you're a better man than I! I just snug up the 10mm bracket screws with a 3/8" ratchet (which limits your ability to over-torque the screws), and then snug up the 8mm sensor screw to the bracket with a 1/4" ratchet, which further limits your ability to overtorque the screw (which doesn't need much torque at all).
Cheers,
Don
#297
#298
Hi Steve,
We just got your email this morning and Helen has sent a reply.
If anyone else wants to contact us regarding a bracket, then please email my wife Helen using helenstodart@gmail.com, as she is processing all enquiries on my behalf. Thank you.
We just got your email this morning and Helen has sent a reply.
If anyone else wants to contact us regarding a bracket, then please email my wife Helen using helenstodart@gmail.com, as she is processing all enquiries on my behalf. Thank you.