@Jagboi64 @Larry Louton @XJRengineer You told me 10:1 might be to much static compression... You know when I started this turbo project I told myself 4lbs of boost would be sufficient; I'm not a young kid anymore. But with the purchase of a boost controller I could not resist; 4lbs, then 6lbs, then 8lbs; I barely stopped at 10lbs, going almost immediately to 12lbs. After hearing my engine ping yesterday at 12.8lbs of peak boost I decided to stick a bore scope in the plug holes and have a look around. I can't tell for certain if the piston damage occurred at 4, 6, 8, 10 or 12lbs of boost; I did not pause very long at each interval to determine the pressure's effect. I'm now just running on the 4lb waste gate spring but fear the engine's days are numbered. It's quiet and still runs strong but I'm not sure I would get in it and drive it a 1000 miles and back. Options?
1. Tear this engine down and fit it with 8:1 pistons
2. Drive it till it fails and replace it with another AJ16 normally aspirated engine. If a piston does suffer a catastrophic failure, it's likely to take out my cylinder head and turbo.
3. Buy a used AJ16 SC engine and sell the induction components I'm not going to use. My instinct would be to try and build the SC engine to support at least 15lbs of boost.
4. Buy a one owner low mile XJR (1995-1997) and add my induction components to it.
5. Buy a low mile 2012 XJL SuperSport for an easy 500hp and call it a day.

Thanks to all who have waded in and been a part of this journey.

 

Cylinder #4 and 6 have definably had some detonation, you can see the erosion of the piston top. Note also that detonation and preignition are not the same thing. Preignition you can hear, detonation is silent, the only way to detect it at the moment it is happening is to measure the instantaneous angular acceleration of the crankshaft.

My worry at the moment is that you may have cracked or broken a piston ring. You'll probably see that in either low compression, increased oil consumption, or scoring of the bore. If everything checks out and continues to look ok, then I'd dial back the boost and use the best fuel you can. The SC engine has max 10 lbs of boost, you can probably figure out what boost would give an equivalent cylinder pressure with the 10:1 compression. Maybe 4-5 psi? That's just gut feel, no math being done.

The X300 engines were designed to run on 90 octane AKI (both SC and NA), so buying the the best fuel you can will help, but your margin of safety is quite small starting with a NA engine and adding boost, even with 94 octane ( if you can find it). An engines' octane requirement decreases with lower temperature and increasing elevation, so perhaps judge your days before cranking up the boost. High elevations and cold weather are your friend - as is high humidly, which doesn't occur in cold weather. If you're near a smaller airport you might be able to get 100 octane Avgas, but make sure it's not leaded. I think some (all??) of them are still leaded.

Of your list, option #5 is certainly the easiest - a problem solvable with cash! Having just bought a 2013 XF with the supercharged 3.0 and AWD it's an amazing car, and very fast. Almost too effortless is the power, it's difficult to drive slow, when I'm not even trying to go fast.

Option #2 is the cheapest. The NA engines are cheap at the self serve junkyards, and never seem to fail. $200 at a Pick Your Part place is probably the cheapest option if/when the current engine fails, and go gentle on the boost.

However, why not just buy an XJR if you want an X300? You'll have similar power to your turbo and factory reliability, plus the heavier duty transmission. I do fully understand the "I built it" sense of accomplishment though.

 

Sorry to read about your engine damage. Unfortunately, it is to be expected running such levels of boost with a 10.0:1 compression ratio, port injection and commercially available octane grade gasoline. Regarding your proposed options:-

1- damage may be more extensive than just pistons,e.g. liners, N.B XJR pistons (no longer available new from Jaguar) are 8.5:1 CR, so might be better to buy an XJR engine. ie option 3
2 - not recommended, for reasons you have suggested
3 - Allows you to keep what you have built, and the sense of achievement that goes with it. Make sure you retain the XJR fuel injectors to go with your XJR ECU and MAF. You will need a bigger fuel pump to maintain 3bar fuel rail pressure above manifold, at the fuel flow you will need
4 - You are likely to end up with similar performance to the standard XJR, but very different ride and handling to your current car. It depends if you want the better handling but firmer ride of an XJR. You will presumably have bought 2 cars in total, but only have one salable car at the end of the process
5 - It's a very different car, and has no " I built it" sense of achievement

It would be a real shame if all of your hard work fabricating the parts for your turbo conversion didn't end up being used.

 

Or really take it to the end, Find a Jaguar AJ16 SC complete engine and GM 4l80 transmission, Build that and attach your turbo charger to the inlet of the supercharger. The plumbing of that would be of great magnitude.

Thank you. Happy holidays.

Larry Louton

 

i’d skip the 4l80e and just run the xjr engine, i don’t think you’re anywhere near the real limit of the ZF.

 

At the risk of sounding like a killjoy, I am not really sure what your objective is, which is clouding which course to pursue, at least in my mind.

If you are trying to achieve outrageous performance on the highway, go for the 2012 XJ suoersport. No X300 will match it for performance, although it does look like s**t (IMHO).
If you are trying to establish that there is a limit to how much boost can be applied to an engine without damaging it, it would appear that you have succeeded with the NA AJ16. I suspect that there was an available body of research somewhere which could have predicted the approximate range in which damage would result, but in any event, it sounds like you have had a lot of fun proving it to yourself.

Repeating the experiment with a lower compression AJ16 engine will reach the same outcome, albeit with a different boost pressure. There will still be a limit, damage will still result as you reach it, and it is already known.

XJRengineer will know far more than me, but my sense is that when Jaguar were engineering the X300, Ford were acutely aware of the reliability issues which had dogged Jaguar, and realised they could not allow a repetition. At the same time, an M5 challenging car was important to revitalise the brand, hence what was quite a significant departure, down the supercharging route. The need for reliability was not forgotten, and in my view explains why some conservatism was built in. The "Andy bracket" sold by XJR Engineer is a clever way to trick the ECU into allowing the performance envelope to be extended beyond what Jaguar intended. Jaguar I suspect knew full well that there was more performance available, but preferred to trade it off in return for an absence of photographs of XJRs sitting at the side of autobahns with melted pistons having been thrashed to death by BMW / Mrecedes test drivers.

Fast forward to the present, the Andy bracket allows us all to easily dip in to a little bit of extra performance, but is not recommended for long term WOT / autobahn use. Since the cars were launched, the general suitability of pump fuel has declined, and of course the engines have aged somewhat, which would lead me to conclude that the optimal course of action is to simply enjoy the engines as presented by Jaguar. Any marginal untapped potential is likely de minimis, and comes at a significant reliability / existential risk. The AJ16 XJR in my view is an exceptional package, and extremely well suited to the realities of modern highway driving, at least where I live. That it looks so good is the icing on the cake, and puts it ahead of its successor the V8 XJR, which while more powerful and better geared, doesnt quite hit the same high note.

Whatever you decide to do, enjoy, and thank you for sharing your experience, as I have much enjoyed reading it.

 

The performance of the supercharged AJ16 engine is fundamentally constrained by the size of the supercharger, not an requirement to limit performance for durability reasons. At the time that we started the project at Jaguar, the M90 supercharger was the largest production supercharger that Eaton made. If they had made the M112 at the time, I'm sure we would have used it instead. The performance of AJ16 engines has been successfully increased well beyond the performance of of the standard supercharged AJ16 engine. I've been running one with an M112 supercharger for 13 years on the road. 5 years ago Gregg Parsons fitted a TVS1900 supercharger to an AJ16 engine in Australia and has dyno tested it at 430kW (577bhp) and 700Nm (516lb.ft). This vehicle has achieved a standing quarter in 12.55 seconds at a speed of 185km/h. A similar specification engine has been built by Swallows Jaguar and has been successfully raced for 2 seasons. Whilst neither of these engines have completed any OEM standard durability tests, I have personally worked on port-injected production engines with similar bore sizes and specific power outputs, so I know it is possible. I don't see any technical reason why the combustion system of an AJ16 engine should not function reliably at these performance levels, provided an appropriate compression ratio of say no more than 8.5:1 is used. The ignition timing and air:fuel ratio also needs to be mapped to avoid detonation. As far as I know, neither of these 2 engines fitted with TVS1900 superchargers were modified to incorporate piston cooling jets. This is a technology routinely used on engines producing in excess of 100bhp/litre, and is highly recommended. Mechanically speaking, the cylinder head gasket joint is the component / system of the AJ16 engine which I would suspect would have the least safety margin, as performance is increased, assuming that this is achieved within the standard maximum engine speed of 5950rpm. With the modifications proposed above, I'm confident that it would be possible to build a reliable turbocharged 600bhp AJ16 engine. Achieving this power output with a supercharged AJ16 engine would be considerably more challenging. This is because of the additional power required to drive the supercharger increasing the gas loads and thermal loads in the combustion chamber.

 

@countyjag Killjoys are always welcome and help to "round out" the conversation. My goal is to double the car's HP with out adding an LS3 or similar, fuel injected V8. These engines, it would seem, have a tremendous amount of potential and make power as smoothly as any I've experienced. I don't think this exercise a completely futile one; I've learned a lot and I hope others have as well; even if that lesson is, "Don't turbocharge your normally aspirated Jaguar without make a few mods or understanding where the "edge" is." @Larry Louton and I are busy conspiring on next steps that could include pulling my engine or a donor engine apart and building it back stronger; adding ceramic coated aftermarket pistons and the addition of large ARP head studs to make sure the head does not lift off. I thought the ability to control the fueling was enough to ensure the engine's survival; I realize now I will have to also control ignition timing; making sure to pull a lot of timing (1 degree per/lb of boost) under load. @XJRengineer You are not off the hook either, I appreciate your valuable input to date and do not envision any future "AJ16" success without your involvement. This current dilemma and my performance goal my current "drug" of choice and I'm confident (with everyone's input) I'll come out on top.

 

Hi Bob,
I've sent you a suggestion for a possible source of forged 8.5:1 compression ratio pistons. Replacing the standard head bolts with higher tensile strength studs is a good decision. This will allow a higher clamp load on the head gasket. These studs can take full advantage of the thread engagement possible in the block, which isn't the case with the bolts. You will need to develop a different tightening strategy for the nuts, as the standard head bolts are torque to yield. If you run the turbo engine with 8.5:1 CR pistons, then the ignition map from the supercharged engine ECU will give you the correct ignition map as a function of mass airflow and engine speed. If you use injectors from the SC engine, then the air:fuel ratio will also be appropriate. I remain available for ongoing consultancy. Usual rates apply.

 

Do guys know how much advance the NA ecu maps are demanding?

 

At the risk of being flipant,yes, I have the main ignition map. It's 2 dimensional with 16 speeds and 16 load sites, so there are 256 different answers to your question, ignoring the linear interpolation which occurs between all sites. The exact load site that is achieve at wide open throttle at any speed will vary with factors such as altitude, ambient temperature and inlet air filter condition. Anyone with decent scan tool software can log the ignition advance and engine speed parameters from the OBDII connector. If a wide open throttle acceleration test is performed, it is possible to generate a wide open throttle ignition curve, under the prevailing altitude and ambien temperature conditions.

 

@XJRengineer I do not think you can sound flippant Andy, and my question was badly formulated or better yet the wrong question completely. I guess work or something broke my train of thought.

Anyways I _think_ I was after the point that if Bob is running NA ECU that demands with full MAF load 39 degrees (number just making the issue more concrete not a real number) ignition and with increasing cylinder pressure (and thus higher temps in the combustion chamber) I am not completely surprised about the failure. Especially as the NA ignition mapping does not have "boost retardation" correction curve/map. Just to make it absolutely sure this is not to have any kind of schadenfreude on what happened or I told you so.

I was just curious how much the advance there is at NA maps at full load area over rev range as basic ignition map demand as I do have speed density based maps for XJR motor (motor is not in x300 chassis, and somewhat non std configuration, but the combustion intake tract, intake cooling characteristics are pretty much in the same ballpark) and the demanded ignition advance is between 10-27,6 degrees (see attached snippet) at top end of MAP values over the rev range


@bsparkman I hope you get thinks sorted out sooner than later, as this has been very interesting endeavor and still continues to be.

And I do hope I more coherent and or clear this time, still not tracking that well after christmas

[edit]

and what comes to the different options, build new NA based configuration just to see how much you can get out of it with SC ecu or other means actually have control over the ignition advance. Mostly because I do have one also lying around... just to be completely honest

 

Hi AnttiM,
Thanks for your understanding. The ignition timing in the top 3 rows of load sites are 3-18, 3-24 and 3-28deg as standard on the XJR map. The load axis is proportional to mass air flow per rev, so it is only possible to get close to load site 15 at maximum volumetric efficiency. At higher engine speeds, it is only possible to get to about load site 13. The scaling of the load axis on the naturally aspirated engines is different because the peak airflow per rev is lower. At the same airflow per rev (not same row of load axis) and engine speed the ignition map for the supercharged engine could have more ignition advance than the NA engine because the CR is only 8.5:1 compared with 10.0:1 for the naturally aspirated engines. The maps of supercharged and NA engines are therefore not comparable as the load site, and even the speed sites are different.

 

Hi Bob

is there been any development on the engine combo over the winter time?