So I'm back tinkering my rolling experiment of an XJS.
The 5.3 has the manifolds from a 6.0 and intakes from AJ6.
Mechanically, it's fit, all the ignition & air/fuel systems are new or tested in working order.
Unfortunately, she's sputtering...
My master tech & I have already tinkered with the ignition believe it's getting more air than the ECU can figure out from the larger manifold & butterflies.
I'm planning to plug an ecu from a 6.0L and see what will happen.

Anyone have any suggestions?

This XJS is a rolling test bed for me (we've experimented on things like full electric fans using the original fan shroud & exhaust configurations with & without cats)

Cheers
Peter

 

No suggestions other than what you've already stated. However I'm interested in seeing the outcome!

 

Thanks,
I'm always open to suggestions.
At the moment, the paint is being stripped and likely go for paint in a few weeks.
Can't wait to get her running; weather permitting
Cheers
Peter

 

I'm in the process of changing out a blown V12 in my 83 with an 85 V12 and wondered what kind of modifications I could make as long as I'm in there (aside from removing all the cat-converters, airpump and stuff). So keep updating this and let me know if changing the intakes made any diffference in power?

 

Cowboy,

I have the same intake setup and it works fine. The ECU can adjust to the change.

I suggest you test your O2 sensors since they tell the ECU how to adjust the A/F mixture.

 

So Don, is there any advantage to switching to this setup?

 

Hey Don,
Are you using the ECU from the original 5.3?
I'll try your suggestion, thanks.
I've eliminated the resonator with straight pipes but kept the muffler; there was no noticeable increase in exhaust noise.
Thinking about the second cat to free the flow further but it might get stinky.
Cheers
Peter

 

Jamey,

There is no difference at lower speeds, but noticable improvement in acceleration at higher speeds.

 

Cowboy,

I used the stock F.I. ECU at first, but cut the trumpets off both air cleaners. I replaced them with short sections of 3" exhaust pipe for increased air flow (and a nice sound).

Later I bought an Enhanced F.I. ECU from Roger Bywater at AJ6 Engineering in the U.K.

BIG improvement in acceleration at all speeds when I installed that ECU!

 

Cowboy,
I had a similar situation, back when I punished myself (and my wallet) through a silly turbo adventure (no less) on my '94 straight six.

As designed, management systems are supposed to adjust fuel delivery to minor airflow increases from breathing improvement mods. In my case, the turbo pushed obviously just too much air through the mass airflow meter (MAF) making its voltage output exceed what's acceptable to the ECU by too much and the ECU just made the engine run like s... when under boost.

If what you've done has created a generous amount of airflow increase, your MAF may, just may, be providing your ECU with just a tad of voltage over the tolerance that the ECU was designed to accept. You can probably find a MAF test on your shop manual and see whether you're exceeding it over whatever the tolerance may be on your V12.

My problem, however, wasn't a "borderline" problem; I read and learned that modern MAF design can keep working with airflows that far exceed whatever the car was designed for (such as with a turbo) and that there were ways to stop the output from increasing at a desired point by using a voltage clamp. I bought and installed a voltage clamp and the problem stopped.

Hope this helps.

Reinaldo
Redondo Beach, CA

 

Bear in mind that the 5.3 doesn't use a MAF :-)


Cheers
DD

 

+1 on the Bywater enhanced ECU :-)

Cheers
DD