I think the admin of xjr6.com has lost all interest. I signed up on the site nov 18 and still await approval.

Sorry about ot, but that site is where I read about this bracket first and I would be sad to see it disappear.

 

Absolutely.

It would be foolish in the extreme to try fiddling around when pre-made is available.

 

I must be missing something here if you retard the timing 5degrees that will cool down the exhaust but increase the head temps. I can't figure out why that might Improved performance and give me better fuel economy.

Please explain....

 

See post #1 ... he said advance.

 

I agree with Doug's comment. Andy's bracket works well.
Christian

 

Okay if you advance the timing on an engine it will increase the head temp and decrease the exhaust gas temp, so my question was how that alone would increase HP and fuel consumption, it was not to reject the idea I just wondered if someone can tell me how that happens. Saying he said ADVANCE tell me nothing only that I wrote the wrong word down.

Are we talking engine timing or cam timing here..?

 

Increasing the ignition timing allows the peak cylinder pressure to be achieved earlier in the power stroke. This increases the amount of work that the burning fuel:air mixture does in displacing the piston down the cylinder. If more useful work can be performed by burning a given amout of fuel, it follows that a reduced amount of fuel is required to do a given amount of work. For instance less fuel will be required by the engine in order to make sufficient power to propel the vehicle along the road at a steady 70mph. Because less fuel will be need, the engine will also need less air to burn the fuel, so in practice the throttle will be less open when crusing at the same vehicle speed. The driver wouldn't be able to feel the difference in throttle opening, but the difference in fuel consumption can be measured.

If an engine is run at a fixed engine speed and fixed throttle opening at the chemically correct air fuel (stoichiometric) ratio for complete combustion of the fuel, then varying the ignition timing will casue a significant variation in engine power output. This is know as a spark sweep. You would find this behaviour described in detail in many textbooks on internal combustion engine theory.

 

I used a Marine Simulator to test what you are saying and I don't mean in anyway to say you will not get better mpg from what you are doing. My concern was only what early timing can do to an engine. This plant is a B&W poppet valve Marine Engine putting out 17,000 KW of power. You will see from the attachment that by putting only 5 deg of early timing on one unit the KW drops by 10 KW and the head temp of that one unit increases by 147 deg C. Therefore using this if all units were timed the same I would have a loss of 60 KW this is a six cyl engine. I would be using the same fuel with a loss of 60 KW of power.

That's why I asked how my MPG can improve with early timing. I was not trying to upset anyone it was just a question..

In my industry we also work on charged air temp (air being fed into the engine) if the ambient outside is 30 degC then the air being fed into an engine should be 7 degrees higher and for every degree above the 7 the engine will loose one half of one HP. Anything below the 7 degrees your making water (dew point)..

 

If I understand your attachment correctly you are referring to a model of a two-stroke diesel engine in which you have changed the INJECTION timing, where as I am referring to a 4 stroke gasoline engine in which the IGNITION timing is being changed. In my opinion these two examples are not at all comparable.

Advancing the INJECTION timing on a 2 stroke diesel engine may well reduce power but advancing the IGNITION timing on a 4 stroke gasoline engine can definitely increase power.

 

Just to chime in ...

the factory design point is "3 degrees retarded from borderline knock" at steady state full load according to the opening post.

In other words, sustained operation at wide open throttle, and probably at the low limit of the specified fuel octane. The policy goal of course would have been to ensure that the engines never reached any knock limit no matter how badly abused by an owner. That would be a warranty and brand reliability image consideration.

Given that knock limiting sensors are part of the system, and that an owner is free to use higher octane fuel, and that sustained operation at WOT is unlikely, the opportunity is there to more fully optimise ignition timing for real world use.

In times past when automotive engine ignitions had tunable static advance, vacuum advance and centrifugal advance mechanisms, it was quite common for those seeking more power to advance the ignition beyond factory settings using those mechanisms.

The bracket simply applies some of the same principles in the face of the lack of those knobs that used to be available to tuners.

The bracket gives knowledgeable owners of the AJI6 and AJ6 engines the opportunity to operate closer to maximum efficiency by using more optimal ignition advance. That results in increased power and better fuel economy.

edit: posted without seeing XJREngineer's most recent post above

 

I'll check when I get time on a 4 stroke engine and see what the result are.

 

You know It doesn't matter what kind of ignition you have, if the advance curve is not set properly it won't make any power. If you advanced the ignition so as to reach peak cylinder pressure right after TDC (top dead center).And if the spark comes too soon the burning fuel will try to push the piston back down the cylinder before it reaches TDC, resulting in a loss of power and possible engine damage. And this is all I have to say on this matter.. It;s not worth continuing as we seem to be going around in circles.
XJR the engine doesn;t know or care were the ignition comes from as long as the air/fuel mixture ignites.

 

This has really been a lifelong issue and why afteermarket tuning can pull more power from said engines. A manufacturer and engineering team finds peak performance, reduced emissions, fuel economy, and reduced warranty costs. Then somewhere in there compromises are made to the public offerings IN MASS. Now Manufacturers and technology has march right along and strides are made to the point that there are not as much to be gained as there once was through mods like this. not only that, but its expensive and time consuming to crack and rewrite proprietary software to retune. Yes there are companies doing it, but only where there is a market. Lets look at the engine in the XJR6 4.litres super charger,
around 290hp
today normally aspirated 5litre is around 400hp
and the supercharge version now up to around 550
So a non supercharged engine today is putting out 100+hp more than yesturdays supercharged engine, and is cleaner burning and more fuel efficient.
Why because computers are faster and tech has grown to the point that such compromises are not as drastic as they used to be. Hell a good dual exhaust system and headers on a 60-70 model v8 netted a good 100hp and improved fuel economy back then. Now exhuast might get a handfull of hp and really just a more favorable tone to the owner and a much lighter wallet. It is not a good bang for the $$ like yesturyear.
So back to the advanced ignition. it depends on the engine, cams specs, cam timing. dish dome or flat top piston and combustion chamber design and other variable. But yes most production engines will benefit from an ignition advance, a leaner afr under power when most factory tunes go rich to ward off detonation and maintain a cooler combustion chamber and less likely to lean out and burn holes in cast pistons or detonate. And even cam advancing which is why VVT operation is such a big benefit, it advances/retards cam timing to give an engine with a dual purpose power band, Good power on the bottom and midrange and great power on the top end all things that just where not possible years ago. you either picked you power band rpm range and lived with it. now youcan have both. As soon as I read this thread i bought the last one he had and is being shipped to me, there was no discussion or questions needed here. I know the value of the part.

 

Glad you cleared that up

 

I sent Andy an inquiry roughly 8 pm on the 18th (Central time zone)

Unfortunately, I didn't have or make time (can't remember which) to check email/computer until the 20th...when I did, I found Andy had replied at 2:47 on the 19th to tell me he had one remaining, dispositioned on first come, first served basis....reading this thread, I noticed Brutal posted this one sometime after 3 pm:
So a quick mental calculation that "last night" was about the same time I sent my inquiry and I knew I'd lost No matter, I wasn't quite ready to do the install then anywho (see mgmt direction I rec'd in Off topic) so I replied on the 20th yielding to my foreknowledge that Brutal probably beat me and telling Andy to let me know when he had additional copies (his first reply indicated that he planned to make another order but parts were a coupla weeks out, yet. So there is hope for us slowbies....

 

I feel I must respond to Simprof's last remarks regarding whether an engine will benefit from advancing the ignition timing. I was the engineer at Jaguar who programmed the ignition map which is in the ECU in every XJR6 which is on the road. I know that this engine will produce more torque across the whole engine speed range if the ignition timing is advanced beyond the mapped value. I know this because I have varied the ignition timing on a steady sate engine dyno and seen the torque vary. Its not just a theoretical benefit it is one that I have personally measured.

 

That's great thanks for the info..

 

I ran out of these brackets following all the initial interest. I've had another batch of 10 made, so if anyone else would like one then please get in touch with me directly by email or PM.

 

Just had my bracket installed 3 days ago on 1995 3.2L X300. My initial impression is that the old girl has a new lease on life.
She is just a little more peppier and responsive to the throttle, more eager to please. Unfortunately this means that I won't be getting a true fix on any economy at the pump until I get over the novelty of the extra power. Maybe I should take the XKR for a spin to get it out of my system, and then get back to "Nana Driving" the XJ!!
Very pleased with the bracket!

 

Ok I can't help it but this seems to going around and around, can someone please tell me what improvement in MPG you are getting with this bracket installed, and what does the bracket cost? I have no interest in more HP my 1997 XJR has more than I need to be honest..