XJR6 Engine ECU Successfully Remapped
#41
12-15-2012, 12:54 PM
missing when hot
XJREngineer
Last year I converted my 1997 Jaguar XJ6 to an XJR6 from a 1995 donor car, switching out the entire engine, gearbox, engine wiring harness and ECU's. I had a small problem with the after cat O2 sensors as I had crossed the plugs over (even though both plugs fit into each others receptors). Once that was sorted that car has been working great...that is until recently. When the car is cold it runs fine, all be it with a minor miss-fire on one of the cylinders. When it warms up it is constantly miss-firing/backfiring and will cut out almost immediately. The engine waring light comes on when it does this, but then goes back off again as it attempts to recover. We have plugged in a diagnostics computer and when it is cold the computer can see the various info of the ECU. When the car starts to misfire/engine light on, the diagnostics computer cannot see any of the information from the ECU. My colleague, who's diagnostics computer we are using, has suggested that the ECU is faulty and as it is getting hotter is causing the issue. Does this sound like a plausible explanation for these symptoms. If it is the ECU will have to obtain another one or at least the chips. P.S I am located in Florida, USA (although I am from Staffordshire) and the car is therefor American Spec.
If required could I use an ECU from a UK Jaguar XJR6.
Last year I converted my 1997 Jaguar XJ6 to an XJR6 from a 1995 donor car, switching out the entire engine, gearbox, engine wiring harness and ECU's. I had a small problem with the after cat O2 sensors as I had crossed the plugs over (even though both plugs fit into each others receptors). Once that was sorted that car has been working great...that is until recently. When the car is cold it runs fine, all be it with a minor miss-fire on one of the cylinders. When it warms up it is constantly miss-firing/backfiring and will cut out almost immediately. The engine waring light comes on when it does this, but then goes back off again as it attempts to recover. We have plugged in a diagnostics computer and when it is cold the computer can see the various info of the ECU. When the car starts to misfire/engine light on, the diagnostics computer cannot see any of the information from the ECU. My colleague, who's diagnostics computer we are using, has suggested that the ECU is faulty and as it is getting hotter is causing the issue. Does this sound like a plausible explanation for these symptoms. If it is the ECU will have to obtain another one or at least the chips. P.S I am located in Florida, USA (although I am from Staffordshire) and the car is therefor American Spec.
If required could I use an ECU from a UK Jaguar XJR6.
then found on the web someone else had the same problem and went away when he put back the old plugs. so i did the same. And it worked. i also measured the distance between the base of the plug at the end of the threads and the tip of the firing electrode and i found that the NGK's were about 1/16" shorter.
I hope it helps.
#43
12-20-2012, 08:46 AM
xjr ecu
I thought that some of you would be interested to read that I have now succeeded in remapping an XJR6 Engine ECU. I have spent the morning driving my 95MY manual XJR6 fitted with an engine ECU that has revised ignition and fuelling maps that I have created myself.
Last weekend I removed the standard ECU from my car and dismantled it. I removed the two EPROMs (Erasable Programmable Read Only Memory), otherwise known as “chips”, from the sockets that are soldered onto the printed circuit boards. I copied the hexadecimal data from these chips into a PC. I was then able to manipulate this data to advance the ignition timing and reduce the level of fuelling over-enrichment.
I then loaded the revised hexadecimal files into two new chips. These chips were then fitted to an ECU that had previously been fitted to a 3.2L X300. It is this ECU which I now have fitted to my XJR6.
Using this same process, I can, in principle, change any of the data in the ECU. There are over 600 constants and 200 maps in the ECU so the possibilities for making changes are enormous. The key is being able to find where any individual map or constant is located in amongst all the data and knowing by how much to change it. Fortunately, as I was originally responsible for creating much of this data when I worked at Jaguar, I have a big head start compared with anybody else trying to perform this process. I hesitate to refer to what I am doing as “chipping the ECU”, since the companies who “chip” cars rarely have access to the “inside information” that has allowed me to reprogramme these ECUs. Nonetheless, it is a term with which many of you are no doubt familiar.
I normally assess potential improvements in engine performance by measuring in-gear acceleration times. It is important to perform the tests on a level road, with the car at minimum kerb weight, AC off and at a typical ambient temperature in order to make comparisons. I log vehicle speed using software on a laptop PC connected to the car’s diagnostic connector.
From these measurements I have calculated that the in gear acceleration times over the full engine speed range has reduced by 7% compared with original road test of this car. I think this is quite an achievement for a car which is 17years old and has no mechanical modifications that would improve its performance.
I will be developing further changes to maps in the ECU to improve performance and fuel economy in the coming months. If anyone is interested in having their ECU reprogrammed then post your questions here or feel free to contact me directly.
I shall be concentrating my effort on reprogramming ECUs for XJR6 vehicles, as these tend to be driven by owners interested in high performance cars, but it would be possible to apply the same process to the ECUs for naturally aspirated 6 cylinder X300 cars (X304).
I will be continuing to offer my revised crank sensor bracket as an alternative method of providing increased ignition advance for all AJ6 and AJ16 engines.
Last weekend I removed the standard ECU from my car and dismantled it. I removed the two EPROMs (Erasable Programmable Read Only Memory), otherwise known as “chips”, from the sockets that are soldered onto the printed circuit boards. I copied the hexadecimal data from these chips into a PC. I was then able to manipulate this data to advance the ignition timing and reduce the level of fuelling over-enrichment.
I then loaded the revised hexadecimal files into two new chips. These chips were then fitted to an ECU that had previously been fitted to a 3.2L X300. It is this ECU which I now have fitted to my XJR6.
Using this same process, I can, in principle, change any of the data in the ECU. There are over 600 constants and 200 maps in the ECU so the possibilities for making changes are enormous. The key is being able to find where any individual map or constant is located in amongst all the data and knowing by how much to change it. Fortunately, as I was originally responsible for creating much of this data when I worked at Jaguar, I have a big head start compared with anybody else trying to perform this process. I hesitate to refer to what I am doing as “chipping the ECU”, since the companies who “chip” cars rarely have access to the “inside information” that has allowed me to reprogramme these ECUs. Nonetheless, it is a term with which many of you are no doubt familiar.
I normally assess potential improvements in engine performance by measuring in-gear acceleration times. It is important to perform the tests on a level road, with the car at minimum kerb weight, AC off and at a typical ambient temperature in order to make comparisons. I log vehicle speed using software on a laptop PC connected to the car’s diagnostic connector.
From these measurements I have calculated that the in gear acceleration times over the full engine speed range has reduced by 7% compared with original road test of this car. I think this is quite an achievement for a car which is 17years old and has no mechanical modifications that would improve its performance.
I will be developing further changes to maps in the ECU to improve performance and fuel economy in the coming months. If anyone is interested in having their ECU reprogrammed then post your questions here or feel free to contact me directly.
I shall be concentrating my effort on reprogramming ECUs for XJR6 vehicles, as these tend to be driven by owners interested in high performance cars, but it would be possible to apply the same process to the ECUs for naturally aspirated 6 cylinder X300 cars (X304).
I will be continuing to offer my revised crank sensor bracket as an alternative method of providing increased ignition advance for all AJ6 and AJ16 engines.
is not for xjr although it was listed as such, i am going to try to return it
my question is once i put in the vortech
if i keep the original ecu and change the maf and fuel injectors , do i have a chance to make it work beyond the air intake flow of the xj6?
alternatively 9 second question)
if i keep original ecu and maf and fuel injectors
what % increase in air flow rate and fuel supply is your guess the ecu can control?
#44
12-20-2012, 03:04 PM
The XJR6 ECU , MAF and injectors MUST be be used together. Using any of these parts without the others will result in poor engine running and possibly even engine failure.
I think from memeory the MAF for the naturally aspirated engine will measure up to about 650kg/hr airflow, so I don't think that if you modify the engine to make much more power than std then you won't be measuring the extra airflow and the engine will run less rich. This is exactly why I recommened changing to the XJR6 ECU, injecotrs and MAF. The std injectors on the naturally aspirated engines are sized for an engine that makes about 240bhp, so like the MAF are not suitable if you uprate the engine significantly.
I think from memeory the MAF for the naturally aspirated engine will measure up to about 650kg/hr airflow, so I don't think that if you modify the engine to make much more power than std then you won't be measuring the extra airflow and the engine will run less rich. This is exactly why I recommened changing to the XJR6 ECU, injecotrs and MAF. The std injectors on the naturally aspirated engines are sized for an engine that makes about 240bhp, so like the MAF are not suitable if you uprate the engine significantly.
The following users liked this post:
aldol (12-20-2012)
#45
12-20-2012, 06:02 PM
The XJR6 ECU , MAF and injectors MUST be be used together. Using any of these parts without the others will result in poor engine running and possibly even engine failure.
I think from memeory the MAF for the naturally aspirated engine will measure up to about 650kg/hr airflow, so I don't think that if you modify the engine to make much more power than std then you won't be measuring the extra airflow and the engine will run less rich. This is exactly why I recommened changing to the XJR6 ECU, injecotrs and MAF. The std injectors on the naturally aspirated engines are sized for an engine that makes about 240bhp, so like the MAF are not suitable if you uprate the engine significantly.
I think from memeory the MAF for the naturally aspirated engine will measure up to about 650kg/hr airflow, so I don't think that if you modify the engine to make much more power than std then you won't be measuring the extra airflow and the engine will run less rich. This is exactly why I recommened changing to the XJR6 ECU, injecotrs and MAF. The std injectors on the naturally aspirated engines are sized for an engine that makes about 240bhp, so like the MAF are not suitable if you uprate the engine significantly.
i will let you know how i make out
#47
12-21-2012, 04:48 PM
Senior Member
Granatelli Big Air Series Mass Air Meters
has anyone used one of these with Andys ecu reprogramming? Granatelli Big Air Series Mass Air Meters Custom Scaled 0-5 volts (equal to 0-2400kg/hr). I just sent off my sc to magnum powers to get the new rotor plate with larger vent ports, said to increase air flow by 10%. I will also be using larger lower sc pulley at 15%, what other changes should be done to ecu.?
#48
12-21-2012, 07:42 PM
Senior Member
#49
12-21-2012, 09:42 PM
Senior Member
Doc,
what changes did andy do to your ecu?, i am really thinking of going that way because of my upgraded supercharger, larger throttle body and larger lower sc pulley coming soon. Also, your headers look great!, my only question is do you have a smog pump on your car?, i dont see a connection on the headers for one.
what changes did andy do to your ecu?, i am really thinking of going that way because of my upgraded supercharger, larger throttle body and larger lower sc pulley coming soon. Also, your headers look great!, my only question is do you have a smog pump on your car?, i dont see a connection on the headers for one.
#50
12-23-2012, 07:43 AM
I remapped the ignition and fuel tables in the ECU that I reprogrammed for Doc. I also sold him the dxf computer files used to programme the machine that cut the exhaust manifold flanges from 304 grade stainless steel plate. Secondary air injection wasn't fitted on Australian spec cars.
I would be surprised if you can fit a 15% bigger supercharger crank pulley without clashing into other parts of the front end ancilary drive system. from my measurements the limit is about 10%. If your total airflow increae was limited to 10%, then I would suggest that running 10% less rich than std would be OK. However, if your modified supercharger really flows 10% more air at max power than you may need a revised fuel map to keep the engine sufficiently rich.
I would be surprised if you can fit a 15% bigger supercharger crank pulley without clashing into other parts of the front end ancilary drive system. from my measurements the limit is about 10%. If your total airflow increae was limited to 10%, then I would suggest that running 10% less rich than std would be OK. However, if your modified supercharger really flows 10% more air at max power than you may need a revised fuel map to keep the engine sufficiently rich.
#51
12-23-2012, 01:40 PM
Senior Member
The new sc plate with larger vent ports and coated rotors are said to flow 10% more air, generate less heat with less parasitic loss.... I have seen the Dynos and the numbers do show what they claim now all is left is to try it out on my car. Waiting for magnum powers to ship sc back and after i install i will check fuel trims. The larger pulley is advertised at 15% od but i dont know until i try it, seems i remember that you have developed a pulley at 10%. Is this true or am i imagining things?, let me know. Can I use a ecu from a 95-97 xj6 4.0 for your upgrades, would like to keep my ecu original.
#52
12-23-2012, 06:29 PM
I thought that some of you would be interested to read that I have now succeeded in remapping an XJR6 Engine ECU. I have spent the morning driving my 95MY manual XJR6 fitted with an engine ECU that has revised ignition and fuelling maps that I have created myself.
Last weekend I removed the standard ECU from my car and dismantled it. I removed the two EPROMs (Erasable Programmable Read Only Memory), otherwise known as “chips”, from the sockets that are soldered onto the printed circuit boards. I copied the hexadecimal data from these chips into a PC. I was then able to manipulate this data to advance the ignition timing and reduce the level of fuelling over-enrichment.
I then loaded the revised hexadecimal files into two new chips. These chips were then fitted to an ECU that had previously been fitted to a 3.2L X300. It is this ECU which I now have fitted to my XJR6.
Using this same process, I can, in principle, change any of the data in the ECU. There are over 600 constants and 200 maps in the ECU so the possibilities for making changes are enormous. The key is being able to find where any individual map or constant is located in amongst all the data and knowing by how much to change it. Fortunately, as I was originally responsible for creating much of this data when I worked at Jaguar, I have a big head start compared with anybody else trying to perform this process. I hesitate to refer to what I am doing as “chipping the ECU”, since the companies who “chip” cars rarely have access to the “inside information” that has allowed me to reprogramme these ECUs. Nonetheless, it is a term with which many of you are no doubt familiar.
I normally assess potential improvements in engine performance by measuring in-gear acceleration times. It is important to perform the tests on a level road, with the car at minimum kerb weight, AC off and at a typical ambient temperature in order to make comparisons. I log vehicle speed using software on a laptop PC connected to the car’s diagnostic connector.
From these measurements I have calculated that the in gear acceleration times over the full engine speed range has reduced by 7% compared with original road test of this car. I think this is quite an achievement for a car which is 17years old and has no mechanical modifications that would improve its performance.
I will be developing further changes to maps in the ECU to improve performance and fuel economy in the coming months. If anyone is interested in having their ECU reprogrammed then post your questions here or feel free to contact me directly.
I shall be concentrating my effort on reprogramming ECUs for XJR6 vehicles, as these tend to be driven by owners interested in high performance cars, but it would be possible to apply the same process to the ECUs for naturally aspirated 6 cylinder X300 cars (X304).
I will be continuing to offer my revised crank sensor bracket as an alternative method of providing increased ignition advance for all AJ6 and AJ16 engines.
Last weekend I removed the standard ECU from my car and dismantled it. I removed the two EPROMs (Erasable Programmable Read Only Memory), otherwise known as “chips”, from the sockets that are soldered onto the printed circuit boards. I copied the hexadecimal data from these chips into a PC. I was then able to manipulate this data to advance the ignition timing and reduce the level of fuelling over-enrichment.
I then loaded the revised hexadecimal files into two new chips. These chips were then fitted to an ECU that had previously been fitted to a 3.2L X300. It is this ECU which I now have fitted to my XJR6.
Using this same process, I can, in principle, change any of the data in the ECU. There are over 600 constants and 200 maps in the ECU so the possibilities for making changes are enormous. The key is being able to find where any individual map or constant is located in amongst all the data and knowing by how much to change it. Fortunately, as I was originally responsible for creating much of this data when I worked at Jaguar, I have a big head start compared with anybody else trying to perform this process. I hesitate to refer to what I am doing as “chipping the ECU”, since the companies who “chip” cars rarely have access to the “inside information” that has allowed me to reprogramme these ECUs. Nonetheless, it is a term with which many of you are no doubt familiar.
I normally assess potential improvements in engine performance by measuring in-gear acceleration times. It is important to perform the tests on a level road, with the car at minimum kerb weight, AC off and at a typical ambient temperature in order to make comparisons. I log vehicle speed using software on a laptop PC connected to the car’s diagnostic connector.
From these measurements I have calculated that the in gear acceleration times over the full engine speed range has reduced by 7% compared with original road test of this car. I think this is quite an achievement for a car which is 17years old and has no mechanical modifications that would improve its performance.
I will be developing further changes to maps in the ECU to improve performance and fuel economy in the coming months. If anyone is interested in having their ECU reprogrammed then post your questions here or feel free to contact me directly.
I shall be concentrating my effort on reprogramming ECUs for XJR6 vehicles, as these tend to be driven by owners interested in high performance cars, but it would be possible to apply the same process to the ECUs for naturally aspirated 6 cylinder X300 cars (X304).
I will be continuing to offer my revised crank sensor bracket as an alternative method of providing increased ignition advance for all AJ6 and AJ16 engines.
the s/c on the town car is now fine tuned and works to nuts i get 5 psi at 3000 rpm and 10 psi at 5000
car is a blast to drive as i love to smoke the little porsches at traffic lights with my big stealthy boat.
so.. the plan for the xj6 is as follows
install the vortech and a battery of gauges and determine by means of a wide a/f gauge what is the max psi i can run with existing maf ecu and injectors
then try increasing the fuel pressure and see if there is any gain
but ultimately to leave the ecu to control all functions but the fuel injectors and install a separate board and maf to control a new set of fuel injector.
the pump seems to be the same as the one on the xjr so it ought to be able to handle a least 300 hp
i'll let you know how i make out
ps
i'd like to run 10 psi and get 460 lb/ft torque ( 280 stock plus 180 from the 10 psi)
ps 2
i got 355/50 for the rear wheels on order
Last edited by aldol; 12-23-2012 at 06:33 PM.
#53
12-23-2012, 08:07 PM
Senior Member
ECU remap worthwile
Doc,
what changes did andy do to your ecu?, i am really thinking of going that way because of my upgraded supercharger, larger throttle body and larger lower sc pulley coming soon. Also, your headers look great!, my only question is do you have a smog pump on your car?, i don't see a connection on the headers for one.
what changes did andy do to your ecu?, i am really thinking of going that way because of my upgraded supercharger, larger throttle body and larger lower sc pulley coming soon. Also, your headers look great!, my only question is do you have a smog pump on your car?, i don't see a connection on the headers for one.
I did find out a month ago that my harmonic balancer must have come loose at some stage before I owned the car and was just tightened
when my Indie repaired the front seal he had a hell of a time getting the balancer of when he did he noticed my key was bent and bolt badly damaged he replaced the key and bolt reinstalled it and hey presto the hesitation from idle was gone after 5 years and trying everything known to man to try and fix the hesitation
The car is going better than ever but I will say that since Andy did the remap the car felt stronger with a slight rough idle
I have since been adding 1.9 ml per litre of TC-W3 rated outboard oil to the fuel the car runs so smooth now I have had mates ask me what I have done to the car it is so smooth I think I could stand a 50 cent piece up on the engine while running
The biggest difference was going to the 3.58 tail gears I have consistently seen higher top speeds since the gear change also the car cruises better before you had to push the throttle a fair bit to pick up speed to overtake on the motorway usually forcing a kickdown which in turn meant a screaming engine very un jaguar like the remap has also finally given this car better economy as well
I haven't taken the car on a long trip yet as I drove into the gate post a couple weeks ago overtired from working hard so she is parked up at the moment with a cover over her under the carport till next year to get the fender and bumper repaired then I will be driving her to Melbourne a 4,000 K round trip then
I will be able to fully check the economy my gut instinct tells me it more economical already
And thanks To Andy again if it wasn't for his knowledge and expertise I probably would have scrapped the car long ago it has taken 5 years to get this cat right but she is going fantastic
I have done more miles in the car this year than any other usually I drive my wife's car as I was a little embarrassed how the XJR went having had quite a few performance cars over the years
I am not embarrassed any more was even thinking of updating to a V8 XJR that idea is no longer in my mind
I still would like to do something to the inter-cooler radiator to get more even temps only because its very hot over here in summer seems to be a season for power loss in both cars
Last edited by doc; 12-23-2012 at 08:09 PM.
#54
12-31-2012, 12:26 PM
Aldol,
An XJ6 has a single in-tank pump.The XJR6 and XJ12 both have a secondary pump which switches in above 4,000rpm to maintain fuel pressure in the rail. If you uprate the engine in your XJR6 to make much more power than standard then you will need an uprated fuel pump.
If you increase the fuel pressure during closed loop fuelling operation, the engine ECU will learn a large negative fuelling correction. This will tend to cancel out the effet of increasing the fuel pressure. I would not recommend this approach, unless you have a pressure regulator which increases the differential prerssure acrosss the injector, as the reference pressure increases, but only above atmospheric prereesure. This MIGHT prevent the fuelling adaptions trying to correct for the cnage in fuel pressure.
An XJ6 has a single in-tank pump.The XJR6 and XJ12 both have a secondary pump which switches in above 4,000rpm to maintain fuel pressure in the rail. If you uprate the engine in your XJR6 to make much more power than standard then you will need an uprated fuel pump.
If you increase the fuel pressure during closed loop fuelling operation, the engine ECU will learn a large negative fuelling correction. This will tend to cancel out the effet of increasing the fuel pressure. I would not recommend this approach, unless you have a pressure regulator which increases the differential prerssure acrosss the injector, as the reference pressure increases, but only above atmospheric prereesure. This MIGHT prevent the fuelling adaptions trying to correct for the cnage in fuel pressure.
#56
01-02-2013, 06:40 PM
Hi Aldol,
XJRguy has already confirmed that X300s are OBDII compliant, albeit with a few bugs in the software. Incidentally, the airflow rate is measured in units of 0.1gm/sec.
I don't know of anyone other than me who replrogrammes ECUs for AJ16 engines, but then I would say that wouldn't I. Seriously, there isn't really enough demand for anyone to make a business out of modifiying these engines. If it wasn't for the fact that I wasn modifying my own cars I couldn't justify the time I have spent remapping the ECU.
As you have obviously spent quite a lot of time and effort on your XJ6 I assume that simply swapping it for an XJR6 is out of the question. However, a simpler solution than reprogramming your ECU would be to fit an ECU from an XJR6 along with the MAF and injectors, unless you think your centrifugal compressor is going to flow more that 1018kg/hr of airflow. Personally, I would be very cooncerned that your engine is going to be extremely knock limited if you retain the 10.0:1 compression ratio and fit a supercharger. The AJ16 supercharged engine has an 8.5:1 compression ratio and an ignition map to match. However, even if you use the ECU from an XJR6 with your modified engie, the ignition is likely to be far too advanced for the std AJ16SC ignition map. Your would certainly be testing the knock control system to the limit even if you ran it on the highest octane fuel that you can buy from gas stations.
Good luck with your project.
Hi Plums,
I'm sorry but I don't do any work on any versions of the Jaguar V8 engines.
XJRguy has already confirmed that X300s are OBDII compliant, albeit with a few bugs in the software. Incidentally, the airflow rate is measured in units of 0.1gm/sec.
I don't know of anyone other than me who replrogrammes ECUs for AJ16 engines, but then I would say that wouldn't I. Seriously, there isn't really enough demand for anyone to make a business out of modifiying these engines. If it wasn't for the fact that I wasn modifying my own cars I couldn't justify the time I have spent remapping the ECU.
As you have obviously spent quite a lot of time and effort on your XJ6 I assume that simply swapping it for an XJR6 is out of the question. However, a simpler solution than reprogramming your ECU would be to fit an ECU from an XJR6 along with the MAF and injectors, unless you think your centrifugal compressor is going to flow more that 1018kg/hr of airflow. Personally, I would be very cooncerned that your engine is going to be extremely knock limited if you retain the 10.0:1 compression ratio and fit a supercharger. The AJ16 supercharged engine has an 8.5:1 compression ratio and an ignition map to match. However, even if you use the ECU from an XJR6 with your modified engie, the ignition is likely to be far too advanced for the std AJ16SC ignition map. Your would certainly be testing the knock control system to the limit even if you ran it on the highest octane fuel that you can buy from gas stations.
Good luck with your project.
Hi Plums,
I'm sorry but I don't do any work on any versions of the Jaguar V8 engines.
Xcceleration
sqrt((boost+14.7)/14.7) * CR = ECR
sqrt = square root
boost = psi of boost
CR = static compression ratio of the motor
ECR = effective compression ratio
ecr max= 12.5 or 12 for safety
i come up with 8.5 psi max on a xj6 that has a cr of 10.0
on my s'charged town car i get 10 psi actual and in fact the formula above gives me about 10psi as the tc has a cr of 9.4
on the vette i will be able to get only 5 psi as the vette has a cr of 10.5
_____________
#57
01-03-2013, 06:41 AM
Aldol,
I can't say i have ever come across the term "effective compresion ratio", as defined by this equation There are many factors which affect the optimum compression ratio for a boosted engine, beside the boost pressure including:-
fuel octane number
fuel injection technology (PFI or GDI)
charge motion
cylinder head cooling
combustion chamber shape
charge motion
I would suspect tha the equation that you have found would prove to be a gross over-simplification. I'm sure I could find plenty of engines that do not conform to this calculation.
Since I believe that you plan to use a centrifugal compressor (Vortex?), the boost pressure will vary dramatically with engine speed. The boost pressure will be much lower at low engine speeds, where the engine is most knock limited. In contrast the Roots type supercharged fitted to the XJR6 is a positive displacement pump, so produces a different boostcurve characterisitc to a centrifugal pump.
In your post you haven't actually asked a question. However, if you are asking whether it is a a good idea to pressure charge a Jaguar AJ16 engine to 8.5psi of boost whilst maintaining a 10.0:1 static compression ratio, then my answer would be No, if you plan to run it on normal 91 pump octane fuel and have no other means to reduce the inevitable knock sensitivty of the engine.
I can't say i have ever come across the term "effective compresion ratio", as defined by this equation There are many factors which affect the optimum compression ratio for a boosted engine, beside the boost pressure including:-
fuel octane number
fuel injection technology (PFI or GDI)
charge motion
cylinder head cooling
combustion chamber shape
charge motion
I would suspect tha the equation that you have found would prove to be a gross over-simplification. I'm sure I could find plenty of engines that do not conform to this calculation.
Since I believe that you plan to use a centrifugal compressor (Vortex?), the boost pressure will vary dramatically with engine speed. The boost pressure will be much lower at low engine speeds, where the engine is most knock limited. In contrast the Roots type supercharged fitted to the XJR6 is a positive displacement pump, so produces a different boostcurve characterisitc to a centrifugal pump.
In your post you haven't actually asked a question. However, if you are asking whether it is a a good idea to pressure charge a Jaguar AJ16 engine to 8.5psi of boost whilst maintaining a 10.0:1 static compression ratio, then my answer would be No, if you plan to run it on normal 91 pump octane fuel and have no other means to reduce the inevitable knock sensitivty of the engine.
The following users liked this post:
aldol (01-03-2013)
#58
01-03-2013, 08:34 PM
Hi, just new to forum, have just converted my 1997 XJR to manual 5 speed, also removed cats and fitted K&N air filter, also just fitted a revised crank speed sensor bracket, now having cold start problems and sometimes cutting out at traffic lights, fine when running, now read about ECU remapping and think this may solve my problems
cheers
cheers
#59
01-03-2013, 10:20 PM
Aldol,
I can't say i have ever come across the term "effective compresion ratio", as defined by this equation There are many factors which affect the optimum compression ratio for a boosted engine, beside the boost pressure including:-
fuel octane number
fuel injection technology (PFI or GDI)
charge motion
cylinder head cooling
combustion chamber shape
charge motion
I would suspect tha the equation that you have found would prove to be a gross over-simplification. I'm sure I could find plenty of engines that do not conform to this calculation.
Since I believe that you plan to use a centrifugal compressor (Vortex?), the boost pressure will vary dramatically with engine speed. The boost pressure will be much lower at low engine speeds, where the engine is most knock limited. In contrast the Roots type supercharged fitted to the XJR6 is a positive displacement pump, so produces a different boostcurve characterisitc to a centrifugal pump.
In your post you haven't actually asked a question. However, if you are asking whether it is a a good idea to pressure charge a Jaguar AJ16 engine to 8.5psi of boost whilst maintaining a 10.0:1 static compression ratio, then my answer would be No, if you plan to run it on normal 91 pump octane fuel and have no other means to reduce the inevitable knock sensitivty of the engine.
I can't say i have ever come across the term "effective compresion ratio", as defined by this equation There are many factors which affect the optimum compression ratio for a boosted engine, beside the boost pressure including:-
fuel octane number
fuel injection technology (PFI or GDI)
charge motion
cylinder head cooling
combustion chamber shape
charge motion
I would suspect tha the equation that you have found would prove to be a gross over-simplification. I'm sure I could find plenty of engines that do not conform to this calculation.
Since I believe that you plan to use a centrifugal compressor (Vortex?), the boost pressure will vary dramatically with engine speed. The boost pressure will be much lower at low engine speeds, where the engine is most knock limited. In contrast the Roots type supercharged fitted to the XJR6 is a positive displacement pump, so produces a different boostcurve characterisitc to a centrifugal pump.
In your post you haven't actually asked a question. However, if you are asking whether it is a a good idea to pressure charge a Jaguar AJ16 engine to 8.5psi of boost whilst maintaining a 10.0:1 static compression ratio, then my answer would be No, if you plan to run it on normal 91 pump octane fuel and have no other means to reduce the inevitable knock sensitivty of the engine.
i did the same on the town car, town car has cr of 9.4 and i have been running 93 octane and 10 psi with no knocking.
i am cutting new gears and gearbox for the vortex in order to increase the gear ratio from 3.5:1 to 6:1 so i can use a larger pulley and avoid belt slipping.
but first i will try my contraption on the Hummer or the Mark vlll because the jag has no commercial tuning software available. and of course i need to retard the timing quite bit.
also on the jag i need to control the fuel injectors with a separate ecu and maf. trick the stock ecu on reading the stock maf .
same deal with timing map. so i will do the jag last
Last edited by aldol; 01-03-2013 at 10:22 PM.
#60
01-27-2013, 10:51 PM
Senior Member
Price info please
Andy,
Big fan of your bracket and am leaning towards the ecu remapping, I drive a 95 xjr6. i have a spare ecu from a 97 xj6 na part number LNB1410AD, would this be ok for the ecu remapping or do you prefer the ecu off my xjr?. I only ask because I would like to keep my ecu original and swap out the remapped one if possible. also can you let us know the price for this service. thank you, David
Big fan of your bracket and am leaning towards the ecu remapping, I drive a 95 xjr6. i have a spare ecu from a 97 xj6 na part number LNB1410AD, would this be ok for the ecu remapping or do you prefer the ecu off my xjr?. I only ask because I would like to keep my ecu original and swap out the remapped one if possible. also can you let us know the price for this service. thank you, David