V12: From U.S. to European Compression Rate?
#21
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Hi Daim.
Thanks for the answer, but everything is new.
I don´t know, if my questions are for this thread, or for new thread, but are about compression and US/UK difference.
Yes I have UK engine with US specs. It is good message.
But somewhere in my head I still have the following questions.
Has a different compression ratio (and other US-ECU for UK engine with O2 sensors), effect on:
- fuel batch for injectors ?
- ignition timing (is really 18°BTDC ?)
- must I adapt US ECU with potentiometr for UK engine ?
- my car (EFI Lucas) work in P or N in open loop mode. I think ?
- can I switch US ECU DAC4585 with UK ECU with O2 sensors ? Is the pin assigment the same ? It make sense ?
Uff. Thanks for the answers.
Thanks for the answer, but everything is new.
I don´t know, if my questions are for this thread, or for new thread, but are about compression and US/UK difference.
Yes I have UK engine with US specs. It is good message.
But somewhere in my head I still have the following questions.
Has a different compression ratio (and other US-ECU for UK engine with O2 sensors), effect on:
- fuel batch for injectors ?
- ignition timing (is really 18°BTDC ?)
- must I adapt US ECU with potentiometr for UK engine ?
- my car (EFI Lucas) work in P or N in open loop mode. I think ?
- can I switch US ECU DAC4585 with UK ECU with O2 sensors ? Is the pin assigment the same ? It make sense ?
Uff. Thanks for the answers.
#23
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Has a different compression ratio (and other US-ECU for UK engine with O2 sensors), effect on:
- fuel batch for injectors ? NO
- ignition timing (is really 18°BTDC ?) YES
- must I adapt US ECU with potentiometr for UK engine ? SEE BELOW
- my car (EFI Lucas) work in P or N in open loop mode. I think ? do not know but see below
- can I switch US ECU DAC4585 with UK ECU with O2 sensors ? Is the pin assigment the same ? It make sense ?See below
- fuel batch for injectors ? NO
- ignition timing (is really 18°BTDC ?) YES
- must I adapt US ECU with potentiometr for UK engine ? SEE BELOW
- my car (EFI Lucas) work in P or N in open loop mode. I think ? do not know but see below
- can I switch US ECU DAC4585 with UK ECU with O2 sensors ? Is the pin assigment the same ? It make sense ?See below
I am assuming you want the car as simple and reliable as possible, and that you would prefer a UK spec system. If this is true, then:
If you do not need to have the O2 sensors, best idea is to get rid of them and fit a UK spec ECU that was for cars that did not have them; ie a 16CU version of the ECU for Lucas cars up to 1987. Loads on Ebay, or Roger Bywater from AJ6 Engineering will convert yours. Then all the open loop stuff etc etc disappears. Also remove all the air pump stuff, if your car has it.
I have recently helped a friend do this exact change and the car went really well. If you can afford it, buy the AJ6 enhanced ECU and large throttle bodies too. It transforms the car.
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roman_mg (12-21-2017)
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.
jagboi; that is not completely true, there were some engines (probably UK only), that had over 10-1 comp. ratios, !
pic drawing from Jaguar of some info about pistons, .
notice piston with tight piston to head and large valve reliefs.
little known fact , is for the Pre-HE head , resurfacing deck face .050 thou. brings the effective ratio up about 2/3 tenths higher, best i can figure is my engine with 9-1 Euro pistons is around 9.2-1 now!
jagboi; that is not completely true, there were some engines (probably UK only), that had over 10-1 comp. ratios, !
pic drawing from Jaguar of some info about pistons, .
notice piston with tight piston to head and large valve reliefs.
little known fact , is for the Pre-HE head , resurfacing deck face .050 thou. brings the effective ratio up about 2/3 tenths higher, best i can figure is my engine with 9-1 Euro pistons is around 9.2-1 now!
Last edited by ronbros; 12-19-2017 at 05:58 PM.
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https://www.ebay.co.uk/itm/Jaguar-V1...sAAOSwCkZZWhTj
Last edited by Greg in France; 12-20-2017 at 05:31 AM.
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Doug
If you look at the second page of Ron's photo of the Hassan book, he actually says the engine was developed on 10.6:1 CR and then subsequently the CR was reduced to 10:1 which was fine on 99 octane RON; then it was reduced further to accommodate much lower octane fuel, presumably for the USA market, as 99 was available everywhere at that time in the UK and Europe. It is not clear from his text whether these changes were made during development or after the engine was in a production car. So I googled the question and found Roger Bywater definitively saying the E type V12 was launched at a CR of 9:1 in 1971, with a lower CR for US and Canada.
Greg
If you look at the second page of Ron's photo of the Hassan book, he actually says the engine was developed on 10.6:1 CR and then subsequently the CR was reduced to 10:1 which was fine on 99 octane RON; then it was reduced further to accommodate much lower octane fuel, presumably for the USA market, as 99 was available everywhere at that time in the UK and Europe. It is not clear from his text whether these changes were made during development or after the engine was in a production car. So I googled the question and found Roger Bywater definitively saying the E type V12 was launched at a CR of 9:1 in 1971, with a lower CR for US and Canada.
Greg
Last edited by Greg in France; 12-20-2017 at 08:45 AM.
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Jagboi64 (12-20-2017)
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UK only. if only i could find a good set of the pistons with the valve cutouts??
Nahh, may as well have custom pistons made , forged aluminum lighter weight, comp. ratio of my choice,, better ring selection(reduced frictional drag), thermal coating on crown , low drag skirt coating.
coatings to keep combustion temps, away from the cooling jackets, i dont want to end up with a small steam boiler!!
#31
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Roman
I am assuming you want the car as simple and reliable as possible, and that you would prefer a UK spec system. If this is true, then:
If you do not need to have the O2 sensors, best idea is to get rid of them and fit a UK spec ECU that was for cars that did not have them; ie a 16CU version of the ECU for Lucas cars up to 1987. Loads on Ebay, or Roger Bywater from AJ6 Engineering will convert yours. Then all the open loop stuff etc etc disappears. Also remove all the air pump stuff, if your car has it.
I have recently helped a friend do this exact change and the car went really well. If you can afford it, buy the AJ6 enhanced ECU and large throttle bodies too. It transforms the car.
I am assuming you want the car as simple and reliable as possible, and that you would prefer a UK spec system. If this is true, then:
If you do not need to have the O2 sensors, best idea is to get rid of them and fit a UK spec ECU that was for cars that did not have them; ie a 16CU version of the ECU for Lucas cars up to 1987. Loads on Ebay, or Roger Bywater from AJ6 Engineering will convert yours. Then all the open loop stuff etc etc disappears. Also remove all the air pump stuff, if your car has it.
I have recently helped a friend do this exact change and the car went really well. If you can afford it, buy the AJ6 enhanced ECU and large throttle bodies too. It transforms the car.
Thank for the answer. The assumption is correct. I just needed a little thrust down the hill
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I still had in my head that the US Hess&Eisenhardt version will have value over time. But when and if, right? I'm 55 and I want to ride, not wait for money
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Only one bad thing. My car is in "registration certificate" marked as Euro 1 car with catalysators. I must find the way change this to non-cat, or buy (AJ6) ECU for Europe with catalysators (I think, that is emission type G for Germany). Or was in UK ECU (Lucas ignition) with cats ? Workshop say, that UK version was without cats, type B. But ...
All other things are clear. Large throttle bodies will be good.
I have a little work to do in the spring
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#32
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The workshop is correct, the UK was without cats until about 1993 or so. I'm pretty sure the ECU wiring was different between catalyist and non catalyist, so you'll have to match what wiring is in your car.
Looking back at your original question, you would need a USA market ECU to correctly run everything. Your fuel economy does seem bad, I would expect motorway economy ( say max speed 110 km/h) to be in the 12-13 L/100km range. When you are using as much fuel as that look at the vacuum advance mechanism to the distributor, it may not be getting proper vacuum. The dump valve can be a suspect. It's complex, make sure everything was hooked correctly when the engine was switched.
See a description here: http://www.jagweb.com/aj6eng/vacuum.php
Looking back at your original question, you would need a USA market ECU to correctly run everything. Your fuel economy does seem bad, I would expect motorway economy ( say max speed 110 km/h) to be in the 12-13 L/100km range. When you are using as much fuel as that look at the vacuum advance mechanism to the distributor, it may not be getting proper vacuum. The dump valve can be a suspect. It's complex, make sure everything was hooked correctly when the engine was switched.
See a description here: http://www.jagweb.com/aj6eng/vacuum.php
Last edited by Jagboi64; 12-21-2017 at 11:21 AM.
#33
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Only one bad thing. My car is in "registration certificate" marked as Euro 1 car with catalysators. I must find the way change this to non-cat, or buy (AJ6) ECU for Europe with catalysators (I think, that is emission type G for Germany). Or was in UK ECU (Lucas ignition) with cats ? Workshop say, that UK version was without cats, type B. But ...
All other things are clear. Large throttle bodies will be good.
I have a little work to do in the spring![Smile](https://www.jaguarforums.com/forum/images/smilies/smile.gif)
All other things are clear. Large throttle bodies will be good.
I have a little work to do in the spring
![Smile](https://www.jaguarforums.com/forum/images/smilies/smile.gif)
#34
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I haven't found anywhere online that specifies an engine code suffix etc.
Anyone?
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WELCOME TO AJ6 ENGINEERING / AJ6 Engineering
When you find out, let us know!
Cheers
DD
#36
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SOHC V-12 Engines
7Sxxxxx 5.3 Liter E-type7P1001 5.3 Liter XJ12/Daimler Double SIx Series 1 w/carburetters
7P4000 5.3 Liter XJ12 & D6 Series 2 w/carburetters
7P25001 5.3 Liter XJ12 & D6 Series 2 w/fuel injection
7P42300 5.3 Liter XJ12 Series 3 Pre-HE (suffix ? = 9:1, suffix HA = 10:1)
7P45001 5.3 Liter XJ12 Series 3 HE
8S1001 5.3 Liter XJS non-H.E.
8S18001 5.3 Liter XJS H.E.
Last edited by Greg in France; 01-04-2019 at 08:48 AM.
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Doug (01-04-2019)
#37
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From memory, the pre-HE high comp engines were rated at 272 SAE net HP and the low-comp versions with cats rated at 244 SAE Net HP. How accurate were the "advertised horsepower" ratings? That's a question for the ages. But, the above seems plausible.
Personally I don't think cat converters, providing they're not clogged, make as much of a difference as some would like to believe. More than a few have reported no 'seat of the pants' difference after gutting or removing them. A very unofficial and broad rule-of-thumb is that a 20 HP increase should be easily detectable by the driver. So my guess would be a 5-10 horsepower increase without cats.
Cheers
DD
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Jagboi64 (01-07-2019)
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Don't take this to the bank but it appears that 7P42300 is the beginning of "Lucas EFI" (as opposed to Bosch D Jetronic) but retained the older Lucas OPUS ignition (as opposed to Lucas CEI). The "HA" variant being the 10:1 hot rod engine
8S1001 5.3 Liter XJS non-H.E.
8S18001 5.3 Liter XJS H.E.
8S18001 5.3 Liter XJS H.E.
But if you have a pre-HE with the later EFI and the older ignition, and a build date from mid 1980 to early 1981, you might have the hit rod engine. I wonder if the "HA" suffix applies to the XJS as well?
Cheers
DD
#40
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About when the decal went on compression dropped back to 7.8-1