Retuning ECU for Larger Fuel Injectors
 

Can anyone point me in a direction to get my 2005 STR retuned for larger injectors?

Thanks, Tom

You will see benifits from a tune .
But the injectors are not the bottle neck .
The eaton supercharger is .
There are Many things you can do to complement an afermarket tune .
And many things you can do and then coplement them with a tune .
But from what I've seen the stock injectors are good for 500-550hp .
Sadly the eaton m112 will never let you get those numbers .

Thanks for the response, however that does not help. I need to run larger injectors and I need a way to scale the ECU.

Care to share why?

My company has developed a flex fuel conversion product and the stock injectors max out around 54% ethanol.

i was thinking the same thing -
my guess would be for ethanol ?

Tommy there are many tuning company's still tuning the 05 onward STR'S.
including i believe two local to these forums. if you have a search you will find .
most are a generic pre written re-map's / re-flash , so not going to be so easy to get custom to your requirements .

I only need the fuel trim values scaled by 75% Anyway, the STR runs great on ethanol. I will be offering a group buy to the forum members next month, but would love to be able to offer larger injectors and a tune to go along with it.

There are two types of engine ECU in the S-Type R depending on the model years.

VIN range M45255 to N52047, 2002.5MY to 2004.75MY
Uses the Denso 32-bit dual processor ECU, tuning options for this are very limited.

VIN range N52048-onward, 2006MY onward
Uses the Denso "PanPag" ECU same as later models like the X150 XK, the XF, etc

The PanPag is relatively easy to tune (can be done over the OBD port) the earlier ones are quite a pain, they can also be done however my understanding is that the injector size data is not freely available for that ECU, the guy who makes my tunes knows it, I don't think other tuners would have that information.

Have you actually measured the duty cycle with the stock injectors on the STR with your ethanol mix? I believe that it's not going to be the injectors that are maxed out, but the fuel table in the ECU.

The tuner I know did an E85 test on a 2007 4.2L XKR, and did not max out the stock injectors, although the injectors on that car are not the exact same ones as the pre-2006 S-Type R, I don't think they are any bigger than the earlier ones, it was related to the electronic changes with the newer ECU.

Yes, our product measures IDC, and my 2005 STR hits 100% DC withe E54, which is extending the pulse ~16.5%. If I don't redline the car drives around great on E85, I just have to avoid in redline pulls.

So checking my VIN it looks like myine is N20591....so does that fit in the first or second category?

N20591 is a 2004.75MY with the Denso 32-bit dual-processor ECU, the not-so-friendly one.

I'm surprised the injectors are maxxed out. I presume you have also looked at the fuel pressure, is it holding a steady ~70PSI at WOT? Not dropping off? The reason I ask is that the fuel pumps in these models are known to drop in performance with age, lots of STR and XJR have had replacement pumps fitted because of that, mine included.

If indeed you need to run bigger injectors, then it's a bit complicated, but do-able, the bigger problem is the equipment needed to actually flash a modified tune to the car, I don't really know anyone local to you.

I will look into replacing the fuel pump and see if that helps

You can see the pump pressure via OBD2, something like Torque App can see it.

Pressure at idle should be around 55psi, will ramp up to 70psi at WOT.

In my case the pressure was falling off from the initial 70psi to as low as 60PSI as the revs went up, the new pumps were solid 70PSI.

There are two electric pumps in an 03-05, one on each side of the tank.

But there are aftermarket ones available, you don't have to buy complete new ones, lots of threads here in the S-Type section about it, also in the X350 XJ section.

Oh dear... that's really low...

I'd be putting in a new fuel filter first, but yeah, seems like you really have a fuel delivery problem...

Interesting thread.

I'd suggest verifying the actual pressure with a mechanical gauge, in case the pressure sensor is out of whack.

I know zero about retuning, so this is just thinking out loud. If the pressure really is low, this seemed to increase the injector duty cycle to compensate. Once you get the pressure issue sorted out (new pump?), if you find the duty cycle still too high, how about this? Make sure the pump is capable of putting out good pressure and volume. Then tweak the sensor output to trick the pump to operate at a higher than normal pressure. That would increase the fuel flow and keep the duty cycle within limits.

​​​​​​I'm not sure how the sensor works, but if you needed to increase resistance, you could add a resistor in series. If you needed to reduce the resistance, you could add a resistor in parallel.

Such a tweak might get around the difficulties of retuning the computer, and would be easily reversible. No idea if it might cause other issues, though.

Hey Cambo,

My fuel pump retaining ring looks like the picture below. IT appears to have like a large hose clamp around it. Do I have to loosen that somehow or can the whole thing just unscrew?

Thanks, Tom

https://cimg3.ibsrv.net/gimg/www.jag...eb2401b9eb.jpg

The hose clamp is an after market safe gaurd against fuel leakage . It just tightens the thread , the white cap does just unscrew .yours does look a little differant to normal .
Yours looks like a Mercedes's e55 one I recently had to deal with .
There is a thread on here showing how to make a tool for that , you cut slots in a pvc gutter pipe so it fits the tangs .
There are two fuel pumps by the way , Primery and secondery , hence the duel pressures .

https://cimg2.ibsrv.net/gimg/www.jag...cf61442fc.jpeg

The stock jaguar retaining ring has pretruding tangs . So something up with yours for sure .

https://cimg5.ibsrv.net/gimg/www.jag...bfd75b1ed.jpeg