Numerous threads discuss the risks and rewards of ECU performance tuning, but having spent much of the week reading them I've observed that there's little emphasis on the actual science of ECU tuning. I'd love to invite others who share an interest in the topic to discuss what is known, what is theorized and what might still be discoverable.

As far as I can tell, the lists below represent a fair picture of how things stand today. There are some things we can assert with evidence, some which we believe (or want to believe,) and some that we honestly don't know.

Known:

• Factory tuning is somewhat conservative
• Artificial limits on top speed can be removed
• Dyno reports vary, but many show substantial gains
• Vehicle owners generally seem pleased with results
• Prices vary significantly among ECU tuning vendors
• Most ECU mods affect only data tables, not program logic

Theorized:

• XKR may be able to achieve power levels of XKR-S
• Damage to engine and vehicle are unlikely
• Gas mileage can be improved by 10-15%
• Performance limits may exist mainly to differentiate XKR and XKR-S
• Some vendors just resell software originally created by other vendors

Unknown:

• Long-term consequences of tuned vs. factory
• Specific rationale for factory's conservative choices
• Detectability of tuned vs. factory ECU software
• Probability of warranty denial issues after ECU tuning
• Specific differences in vendor tuning strategies

The last point is of extreme interest to me. I read a blog post by Jags Gill of ETG, widely regarded as one of the top experts in the field, in which he discussed getting actual software from an unmodified XKR-S and using it to compare with XK and XKR. He pinpointed both the similarities and the differences between each model's software, so I believe this is evidence to support his assertions about the XKR being able to meet or exceed the specs of the XKR-S with tuning. Have others like Eurocharged been able to get unmodified XKR-S software to make similar comparisons? Is one vendor's tuned software worth twice as much as another vendor's? I have no idea!

ECU tuning is a fascinating topic, and I hope we can avoid yet another pros & cons discussion and instead focus on gathering what we know about Jaguar ECU tuning from a more scientific perspective. It might help members decide what they feel is best for their own enjoyment of their cars.

Cheers,
Rick

 

Very interesting. I don't even know how the ECU works and what the "data tables" might contain from the factory!

 

We're having this discussion because operating characteristics of modern cars are electronically managed. Only the manufacture knows the true safe limits of stress that their cars can mechanically handle. There are so many components other than the engine that need to be protected. Some engines, such as the 5L SC, have a lot of reserved power held back by the manufacture as evident by various models, 510hp XKR, 550hp XKR-S, 495hp F-type, 600hp F-type R.


Only the manufacture and engineers of the drive train and chassis know the real limits of our cars. Our tuning and performance shops can tweak and play with the electronic management to get more out of the our cars to a certain point before components start to fail or other electronic management modules interfere. In order to properly tune a car all of it's limits should be known and all of it's relevant software maps need to be adjusted safely so the power can be delivered as expected and not bleed off.


If we were to ask all of the tune shops a list of questions, I doubt it if they would reply. Why? Do they buy the tune from an engineering company and are simply distributing it for profit with no knowledge of how the tune will effect other components or how other electronics communicate with it, like the TCU. I suspect this is so.


I don't see the science in evaluating a tune other than relying on the due diligence of the tune or performance shop's knowledge base and methodology. These shops need to lead with knowledge and disclosure for customers to rely on them to be safe and effective. For example, at what point does the TCU bleed off power to save the ZF transmission and what are considered safe limits. IMO, a good tune or performance shop will know these parameters and how to safely deliver any extra power available effectively to the wheels.


As far as the engine is concerned, I'm sure the 5L SC, can go to 850hp with some rather simple hardware mods, if they were available. We're only interested in the safe and effective release of any reserved power held back by doing an ECU tune safely following safe engine management best practice through a remap.


Our cars have already been engineered, all we can do is tweak them given the know how with safe parameters. The key is knowledge of these safe limits and related electronics for the power to be delivered. Engine management through remapping the ECU following safe practise is a study in itself.


Where do the available tunes for our cars come from? Do all the tuning shops make there own or do they buy them from an engineering company? I know Jags at ETG basis his tune on the XKR-S's map. All of this information needs to be disclosed to the us as the end user so we can trust it. Again, knowledge and disclosure is what we need to make a sound decision of how to select an ECU map. Some tuners also remap the TCU. Is the TCU map for the XKR different than the XKR-S because the XKR-S has a beefed up torque converter? Some people have experienced lost of power at the high end from their tune. Why? Is this because the SC pulley change or the TCU bleeding of the power? Knowledge, research and disclosure is what we need.


I suspect most of these tunes offered are based on the XKR-S factory tune and have been tweaked by an engineering company. Most of the tune shops without an engineering department simply install the tune and hope for the best. If we were to give the tune shops a list of questions I bet none of them will reply with complete answers because they either don't know or don't care. Although, as owners these questions are very important because we live with the tune and have a stack in the game.

 

Hello Rick,

This is the first time I personally replied to a post, the forum is handled by someone else (Finding time to respond is very hard). I’m going to make it very brief (for a quicker response you can call 877-813-9700 x 5). I have been doing this now for 23 years and feel I can talk on the subject. The 470hp Jaguar has the same engine as 550hp XKR-S; the only difference is the software. You can find a dyno sheet on our blog where we got 66whp (76hp) before adaptation ‘with a stock pulley’ on a 470hp XJ, the dyno test was done by the customer. Recently we completed a F-Type for Lamborghini of Miami and when they tested the car the result was 618hp.

We released and installed the ECU/Pulley upgrade for the 5.0 supercharged engines back in 2009 (first car tuned was for Overfinch of NA). The car made great power with no issues and still drives perfectly until this day. We work on about 4 or 5 of these engines everyday including Range Rovers.

It’s always best to call the company tuning the car as oppose to hearsay. Again, it’s easier to reach me by phone.

Regards,
Jags

 

I would also love to hear from anyone who has tuned their 300 hp XK and what gains were achieved.

 

Great response. I don't think people are questioning whether the tunes actually work--I think we're all sort of wondering whether anyone, other than Jaguar engineers, knows the true limits of the engine.

How would one know whether a tune was the maximum safe output possible for the engine without actually destroying an engine in the process?

 

Just talked to ETG and they said it would give a regular 4.2L XK 30hp increase and a 24ft pounds of torque increase.
They send you a laptop and they talk you through it. $695 plus$95 for shipping of the laptop.
(Vs 55-60hp for 4.2L supercharged car, stock pulleys.)
Seems a bit high priced for 30hp for my XK.......maybe if we got group buy going we could get a discount. They sounded open to that. Anyone up for that?

 

I wish I knew the significance of a 30 hp gain. Would we even notice it? It equates to a 10% boost. That doesn't seem like much, but I have no reference with which to assess.

 

Perfect! What is the significance of a 30 hp gain? This is a great item we can try to methodically put it into perspective. There must be a set of calculations to help us understand the significance. Let's leave out the mandatory discussion that performance may be different at different altitudes, temperatures and humidities. We all know that, and still we can probably find a useful way to speak together about averages.

For example, on an XK with a curb weight of 3800-3950 pounds, what will that 30+ hp mean in your 0-60 mph time? How will it affect your ability to accelerate from 40 to 60 in order to pass someone on the street, or 65 to 85 to pass someone on the highway? If calculations cannot be done reasonably, then we can measure. The point is that it doesn't have to be subjective guesswork that leaves us doubtful and afraid.

I don't know about you guys, but I don't spend much time driving on dynos. Performance on a dyno is certainly meaningful, but performance when we're driving from point A to point B is much more meaningful, and I want to have the most possible fun doing so! I bet I'm not alone in wanting to understand how 30+ hp would feel, so I can make a good decision about whether to spend my hard-earned money to get it.

Cheers,
Rick

 

From the S-Type forum, there is little to be gained by tuning the 4.2 NA or SC unless you first do something else major, such as changing to a twin-screw. The tunes are dubious and very expensive for little gain otherwise. It's the same 4.2 as in XK8/R.

Back to the science - the very first thing is to dyno before making any changes. Hardly anyone does this!!

 

Thanks, Jags! It's so helpful to have someone as knowledgeable as yourself share your thoughts directly with the rest of us. Thanks for responding, and I hope we'll be able to have future discussions that you'll consider time well spent.

Useful data! It speaks to two points. First, that 2009 car is still purring 5 years later, so longevity is possible for Jaguars with performance tuned ECUs. Second, you do 4-5 tunings every day, so let's conservatively call it 1200 per year. That demonstrates a quantified level of practical experience that few can match. In other words, we can safely consider you an expert!

Really interesting questions may emerge as this topic develops, Jags. I hope you'll peek in from time to time and share any additional insights if you feel inspired.

Cheers,
Rick

 

I think it's fair to say:


There are a number of companies that provide an ECU tune. Most of these tunes are based on some sort of variation of the XKR-S map for the 5L SC. Most members who have taken the leap of faith are happy with the performance gains. Dyno charts posted on this forum show gains of 100hp are not unreasonable. However, there are some charts that show the gain is bleed off at the high end but does not drop off below a stock tune. The formula used to calculate the 100hp gain is (Tuned Dyno#/.85) -Stock # where the power loss is assessed to be 15% from the fly wheel to the wheels. This is in line with what the tune shops say and would certainly provide a different driving experience.


There is a thread on the XFR forum where a member is going to measure the boost from a stock, a pulley only, and a tuned/pulley XFR. This is not scientifically sound because it will be measured on 3 different cars. however, it may offer some insight for what it is worth:
https://www.jaguarforums.com/forum/x...x-pipe-111588/




The TCU will communicate to the ECU to back off if its set power parameters are exceeded. Consequently, if an XKR (with out the beefed up torque converter on the XKR-S) has an upgraded ECU and TCU tune transmission damage is possible. If the TCU is not upgrade it should function as designed to protect the transmission.


These tune shops provide an engine tune in isolation with little consideration given to the whole car. The first buyers of the tune take a leap of faith as beta testers. Most brave beta test owners are happy with the results reporting no damage to date from operating their beloved Jags with the upgrades.


In conclusion, after beating this topic around for awhile, on many threads, IMO, I believe most tunes are very similar and do not pose any immediate damage to our cars if the increased power is used conservatively and is respected. I'm sorry I could not be completely scientific in my comments. I hope everyone makes the right decision so they can get the most enjoyment out of their beloved Jags.

 

Nice posting and summary, DGL. Thanks!

This TCU <=> ECU interaction sounds like important stuff. Do we only know generalities, or are there sources for specific details about how the TCU and ECU interact?

Also, is anyone aware of any known cases of transmission damage that were caused by the higher horsepower and torque of an ECU tuned engine? It is certainly plausible to believe it could happen, but do we have any hard evidence that it actually has happened?

Cheers,
Rick

 

Why do we even want to do this? As it is the tires spend way to much time spinning from the current HP. I suppose that it would increase the top speed that you can go but I've never had the car over 85 MPH. As far as damage goes do to to much HP, there is not a single line between good to go and need a tow track. It's simple going to move the probability curve of something happening closer to yes then no. With that said I'm thinking about doing it myself...

 

In the Jaguar work shop manual the ECU is referred to as the ECM (Engine Control Module) and the TCU is referred to as the TCM (Transmission Control Module). The Jaguar work shop manual can be purchased at jagdocs.com and is only around $25.00. Compared to Mercedes Benz the manual is much better written, easier to navigate, and so much cheaper. I'm not sure if the ECM communicates directly with the TCM or through the main bus (not show what Jaguar calls their main bus). The workshop has a wealth of information and I'm sure you will find it very useful over the years.

 

TCM communication page from WS manual is posted below. I'm not exactly sure to what extent the TCM protects the transmission. However, if we don't track our cars every week and don't drive like a hooligan I think we will be fine.

 

An excellent thread indeed.

I am going to call Jags when I get a moment. Would be nice to know too, what difference 30HP will make. I have been procrastinating for a while but planning on getting my baseline dyno very soon. I also wonder how much a smaller pulley will actually decrease horsepower over time due to increased heatsoak.

And I'd also like to find out about being able to restore the tune in case the car should ever need to be serviced and the ECM reflashed by the dealer.

 

Get better tires!

 

Awesome tip, and jagdocs.com looks like a great resource for any Jaguar enthusiast. Thanks!

BTW, I bought 6-7 documents, and they automatically applied a quantity discount that seems to have saved about 20%. Really nice.

Cheers,
Rick

 

From the S-Type forum, there is little to be gained by tuning the 4.2 NA or SC unless you first do something else major, such as changing to a twin-screw. The tunes are dubious and very expensive for little gain otherwise. It's the same 4.2 as in XK8/R.

Back to the science - the very first thing is to dyno before making any changes. Hardly anyone does this!!


Thanks JagV8, that makes a lot of sense. I have more horse power than any car I have ever owned, 420. But I want more power even if I can just say I have 500hp. I really don't need it and I don't want to hurt the car but the forum seems to say it gives you more power, more mpg and runs better. The idea of plugging in a gismo and getting 60 or 70hp sounds great.