Stock 5.3 HE V12 potential
#21
04-04-2018, 08:37 PM
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#22
04-04-2018, 09:23 PM
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The conversion has probably cost me over $2k so far in all the bits and pieces that are necessary. I honestly think I probably could have got just about as close using a set of late carbs with a manual choke off my DS420. The only thing I would have been lacking is elevation compensation that the EFI does very nicely.
You could spend a lot of time and effort and maybe get a few % better than a factory ECU. Or maybe never get to where a factory ECU is. My experience is it's not a good use of time and resources, unless you simply want the intellectual challenge of doing it for it's own sake.
#23
04-04-2018, 10:13 PM
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The issue is confounded because at the same time (1971-72) horsepower ratings were transitioning from SAE Gross to SAE Net manufacturers were also dropping compression ratios across the board....which obviously meant less power to begin with.
It's well accepted that manufacturers sometimes played things fast-n-loose with 'advertised horsepower'. Some of the more prosaic engines were over-rated; some of the high-performance types were actually under-rated.
Cheers
DD
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#24
04-05-2018, 01:09 AM
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I've converted a 1966 S Type to EFi using megasquirt. Don't expect miracles, it takes a lot of work, time, money and devotion to get anywhere close to factory drivability. I've been tweaking it for 7 years now and it's "acceptable"; it's nowhere near the drivability of a factory ECU. I think the documentation is somewhere around 400 pages with everything described, and like it or not you will have read it all many times and understood it all in order to get the car running reasonably well. It's about the furthest thing from plug and play there is.
The conversion has probably cost me over $2k so far in all the bits and pieces that are necessary. I honestly think I probably could have got just about as close using a set of late carbs with a manual choke off my DS420. The only thing I would have been lacking is elevation compensation that the EFI does very nicely.
You could spend a lot of time and effort and maybe get a few % better than a factory ECU. Or maybe never get to where a factory ECU is. My experience is it's not a good use of time and resources, unless you simply want the intellectual challenge of doing it for it's own sake.
The conversion has probably cost me over $2k so far in all the bits and pieces that are necessary. I honestly think I probably could have got just about as close using a set of late carbs with a manual choke off my DS420. The only thing I would have been lacking is elevation compensation that the EFI does very nicely.
You could spend a lot of time and effort and maybe get a few % better than a factory ECU. Or maybe never get to where a factory ECU is. My experience is it's not a good use of time and resources, unless you simply want the intellectual challenge of doing it for it's own sake.
#25
04-05-2018, 04:46 AM
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I have been busy at work and setting up my new home shop(milling machine and lathe). I'll be back working on the engine in a couple of weeks.
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#26
04-05-2018, 05:46 PM
#27
04-05-2018, 06:30 PM
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pic of Chevrolet engine BBC, making around 900HP, NO turbo's,, year 1968, these cars were faster than F1 Grandprix cars of that era!
you young guys have no idea what 20 of those BBC open exhaust , sound like coming onto the 1st corner straight, at full throttle
most were banned because they were to FAST, suspension and brakes were not good enough,, lot of guys were killed, so rules were made 1969.
then Porsche figured out how to Turbo there Flat twelves, 1500HP!
YUP that was the end of that crap racing!
you young guys have no idea what 20 of those BBC open exhaust , sound like coming onto the 1st corner straight, at full throttle
most were banned because they were to FAST, suspension and brakes were not good enough,, lot of guys were killed, so rules were made 1969.
then Porsche figured out how to Turbo there Flat twelves, 1500HP!
YUP that was the end of that crap racing!
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CaptainShakey (06-28-2021)
#28
04-05-2018, 11:23 PM
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If you want a bit more sound, try AJ6's TT exhaust: HIGH QUALITY XJS EXHAUST SYSTEMS from AJ6 ENGINEERING / AJ6 Engineering
I have a 94 6.0, and the PO removed the mufflers and left the rear resonators. Frankly, it sounds awful. It's a only a bit louder, but the sound quality is really bad. It sounds cheap and nasty, not refined like a V12 should.
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#29
04-06-2018, 04:30 AM
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#30
04-06-2018, 11:30 PM
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Has anyone tried to up the compression ratio? I don't recall coming across anything about that, the topic came up talking to my brother about that new Mazda engine with insane compression resulting in a super-efficient gasoline engine where ignition is achieved via compression alone.
Is there much benefit to higher compression in an old gas engine?
Is there much benefit to higher compression in an old gas engine?
#31
04-06-2018, 11:50 PM
Veteran Member
Has anyone tried to up the compression ratio? I don't recall coming across anything about that, the topic came up talking to my brother about that new Mazda engine with insane compression resulting in a super-efficient gasoline engine where ignition is achieved via compression alone.
Is there much benefit to higher compression in an old gas engine?
Is there much benefit to higher compression in an old gas engine?
If you do increase ignition you'd need a fairly sophisticated ignition system to combat detonation.
#32
04-06-2018, 11:56 PM
I had a Series III V12 sedan and the cats plugged off due to mechanical damage. I removed them and put on a European exhaust with no cats. I didn't do any serious measuring, but the seat of the pants meter said the car was no quicker.
If you want a bit more sound, try AJ6's TT exhaust: HIGH QUALITY XJS EXHAUST SYSTEMS from AJ6 ENGINEERING / AJ6 Engineering
I have a 94 6.0, and the PO removed the mufflers and left the rear resonators. Frankly, it sounds awful. It's a only a bit louder, but the sound quality is really bad. It sounds cheap and nasty, not refined like a V12 should.
If you want a bit more sound, try AJ6's TT exhaust: HIGH QUALITY XJS EXHAUST SYSTEMS from AJ6 ENGINEERING / AJ6 Engineering
I have a 94 6.0, and the PO removed the mufflers and left the rear resonators. Frankly, it sounds awful. It's a only a bit louder, but the sound quality is really bad. It sounds cheap and nasty, not refined like a V12 should.
#33
04-06-2018, 11:59 PM
Veteran Member
No, sorry. It's been a brutal winter here, -10C and snowing as I type, so the convertible is staying in it's winter storage for a while longer. Certainly until all the salt is off the roads, my X Type is white from all the salt on it. Poor car.
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ronbros (04-07-2018)
#35
04-07-2018, 02:00 AM
Veteran Member
No, the engine has a high enough ratio as standard. It is all, and only, about cylinder filling, which equals the ability of the engine to take in air. The HE engine is very efficient at normal highway revs, but at high revs the valve layout inhibits cylinder filling.
To make more power the cheapest way is to fit pre-HE heads, larger capacity liners, and take the hit on fuel costs in normal use.
Having said all that, when Warrjon's motor starts running, we may all be proved wrong!
To make more power the cheapest way is to fit pre-HE heads, larger capacity liners, and take the hit on fuel costs in normal use.
Having said all that, when Warrjon's motor starts running, we may all be proved wrong!
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ronbros (04-07-2018)
#36
04-08-2018, 03:11 AM
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Spark plug is offset in the cylinder (both planes front/back and left/right) this causes uneven pressure on the piston so some of force is lost pushing against the cylinder wall.
The deep pocketed exhaust valve tightens the turn in the port.
One of advantages is more torque than the pre-HE due to a better burn. The high swirl chamber provides a more homogeneous mixture leading to a more complete burn, in other words m ore of the fuel is burnt.
I remember reading an article by David Vizard on his Chrysler Avenger which did not have the top end power of BDA Cosworth Escorts but this this was soo much quicker because of its WIDE power band. His secrets were excellent low lift flow and tumble/swirl. This 1500cc pushrod all iron 4 walked all over the 1600 BDA Escorts.
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#37
04-08-2018, 11:11 AM
Member
#38
08-31-2019, 04:29 PM
Hi all. I recently became the owner of a 1986 Jaguar XJS V12. I purchased it to use the front end under my 1977 Chevrolet C10 pickup that I'm building and as I've not decided on an engine yet I wonder about the potential of the HE V12. I haven't delved too deep into it yet but what I do know is it hasn't run in years, has 89k miles on it, was parked up because the fuel pump failed, and amazingly still cranks! Given what the engine is to make only 265hp makes me ask what is holding it back? It has a large bore, short stroke, and high compression. Are the valves too small? the cams too small? the heads flow poorly? the engine management underdone? the injectors? the throttle body? Where is it being restricted? My thought is to put the engine in front of an overdrive toploader. I'll need to build a wiring harness for the engine. Is it worth using the factory engine management (I know I'll have to get it modified for the manual transmission) or building a MegaSquirt system for it? I know that's been done. What can I expect by way of power, torque, and drivability with a MegaSquirt system, larger throttle bodies (and injectors if necessary), and long tube headers? Do you need to change the cams in these engines? (I come from the world of Chevy engines were little more than an exhaust and and a cam wakes an engine up) What is this engine capable of with just a few simple modifications?
You don’t have to buy a lot of expensive parts just to look cool. It’s an all aluminum engine. Want pretty? Polish. Want simple Use carbs. ( yeh they will cost you 20 horsepower but you can get rid of the restrictions the stock “ computer” has.
Want that 20 horsepower back and then some? Cut off the dog leg in the stock system and switch to 2 inch SU carbs. That’s 30-40 horsepower for a little bit of welding.
Want 10% more? Switch to E85. All you have to do is ream the jets out to flow 60% more flow. ( nope not 60% bigger, more flow)
cam shafts will help make power but at a cost of bottom end power. Isky, Crower, heck my neighborhood cam grinder can get me more lift than the .375 the stock ones have. And longer duration.
But you’ll be faster leaving the cams stock. AJ6 engineering has a nice explanation. Kinda depends on if you want bragging rights or win races.
I hope someone does does a good job with a megasquirt. and comes on and explains it all here. I’ve picked up two cars the owners have given to me out of frustration trying to get the mega squirt system to work. I’ve read and tried to follow but to my knowledge if you want to retain the EFI and want more out of it your only choice is AJ6 engineering. . They aren’t cheap.
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CaptainShakey (06-28-2021)
#39
08-31-2019, 04:31 PM
More streetable power affordable
Hi all. I recently became the owner of a 1986 Jaguar XJS V12. I purchased it to use the front end under my 1977 Chevrolet C10 pickup that I'm building and as I've not decided on an engine yet I wonder about the potential of the HE V12. I haven't delved too deep into it yet but what I do know is it hasn't run in years, has 89k miles on it, was parked up because the fuel pump failed, and amazingly still cranks! Given what the engine is to make only 265hp makes me ask what is holding it back? It has a large bore, short stroke, and high compression. Are the valves too small? the cams too small? the heads flow poorly? the engine management underdone? the injectors? the throttle body? Where is it being restricted? My thought is to put the engine in front of an overdrive toploader. I'll need to build a wiring harness for the engine. Is it worth using the factory engine management (I know I'll have to get it modified for the manual transmission) or building a MegaSquirt system for it? I know that's been done. What can I expect by way of power, torque, and drivability with a MegaSquirt system, larger throttle bodies (and injectors if necessary), and long tube headers? Do you need to change the cams in these engines? (I come from the world of Chevy engines were little more than an exhaust and and a cam wakes an engine up) What is this engine capable of with just a few simple modifications?
You don’t have to buy a lot of expensive parts just to look cool. It’s an all aluminum engine. Want pretty? Polish. Want simple Use carbs. ( yeh they will cost you 20 horsepower but you can get rid of the restrictions the stock “ computer” has.
Want that 20 horsepower back and then some? Cut off the dog leg in the stock system and switch to 2 inch SU carbs. That’s 30-40 horsepower for a little bit of welding.
Want 10% more? Switch to E85. All you have to do is ream the jets out to flow 60% more flow. ( nope not 60% bigger, more flow)
cam shafts will help make power but at a cost of bottom end power. Isky, Crower, heck my neighborhood cam grinder can get me more lift than the .375 the stock ones have. And longer duration.
But you’ll be faster leaving the cams stock. AJ6 engineering has a nice explanation. Kinda depends on if you want bragging rights or win races.
I hope someone does does a good job with a megasquirt. and comes on and explains it all here. I’ve picked up two cars the owners have given to me out of frustration trying to get the mega squirt system to work. I’ve read and tried to follow but to my knowledge if you want to retain the EFI and want more out of it your only choice is AJ6 engineering. . They aren’t cheap.
#40
08-31-2019, 11:14 PM
Gross horsepower VS DIN
[QUOTE=ronbros;1870415]lets remember back 20yrs before Jag HE , american engines were putting out over 400HP++.HP
Chevies of old have Gross horsepower ratings. That 400 horsepower was gross, adjusted for the drag or water pumps, oil pumps, etc. Pre smog compliance, using leaded gasoline high compression to take advantage of the leaded gas.
When rated under the new net horsepower ratings complying with current smog rules etc. that so called 400 horsepower in a Corvette engine turned into 160 horsepower or less. At that time the Jaguar V12’s made 242 horsepower. Three years later while Corvettes were saddled with 160 horsepower the early EFI made 264 in California and 289 in the rest of the world. Later ( 1980 ) making 299 while California ( and much of the country ) stayed at 264 until the 6.0 came out with 314
Short version. 400 horsepower wasn’t the same.
Chevies of old have Gross horsepower ratings. That 400 horsepower was gross, adjusted for the drag or water pumps, oil pumps, etc. Pre smog compliance, using leaded gasoline high compression to take advantage of the leaded gas.
When rated under the new net horsepower ratings complying with current smog rules etc. that so called 400 horsepower in a Corvette engine turned into 160 horsepower or less. At that time the Jaguar V12’s made 242 horsepower. Three years later while Corvettes were saddled with 160 horsepower the early EFI made 264 in California and 289 in the rest of the world. Later ( 1980 ) making 299 while California ( and much of the country ) stayed at 264 until the 6.0 came out with 314
Short version. 400 horsepower wasn’t the same.
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Greg in France (09-01-2019)