Quick back story: I previously had installed a +4 lower pulley, giving me 18-19 psi of boost ( +8 over stock) Thinking I could be risking running out of fuel supply with the stock set up with 4.0 injectors, I added a Kenne Bell Boost a pump which ran the pumps at 17.5 volts when on boost.

Then, in a rare (and obviously fleeting) moment of sanity, I decided to remove the lower pulley/go back to stock lower and planned to add an upper 1.5 lb pulley for a target of 15 psi.
Soooo, I sold the Boost a pump.

Then, somehow the lower pulley came loose (after being torqued 260 ft lbs) and damaged the inside of the stock pulley. I had a mechanic look at it and they found the locking ring had been damaged and was the likely culprit. Short story, no more stock pulley.

So I'm interpreting this in the only way that is possible (heh) which is that the car is telling me it reallly prefers to breath more with the lower +4 pulley. So having no stock pulley immediately available, and having the +4 lower sitting on my shelf, I had the +4 ("race car pulley" as it has come to be referred to) re-installed.

So, now I'm back to my 18 psi of boost, and think I need more fuel supply than stock, since I've heard the stock system can only deliver up to approx 20% more (+74 hp more over the 370 stock).

Soooo, before I decide if I need to add a boost a pump I've added an additional 2nd parallel set of 10 guage wires with posi tap connectors to and from the pumps. So, to clarify: The existing stock wires are intact, and I've added an additional set of wires. This was done to reduce the voltage losses over arguably too small stock wires.

Now that the fuel pump wires have been upgraded I feel confident enough to go get a dyno and closely watch the AFR and make sure the operator will also CLOSELY watch the afr, so that if the car goes lean at high boost, we can hopefully get off the throttle fast enough to avoid damage. Even if this happened while on a dyno with a good afr, the dyno would then just be a very expensive idiot light. "We have some very good data of your engine melting sir..." is something I want to avoid.

Now I can run it on a dyno which should then give me enough info if my existing fuel supply is enough, or if I need to add more fuel supply, and if I can do just one adjustable voltage BAP on the 2nd pump, or if I need more than that...


Any predictions?

 

I upgrade my pump wires on almost every car I modify and its made a difference. It will help with potential voltage dropoff but its never helped me when I actually needed a larger pump. Definitely a good safety precaution. Are you able to upgrade the injectors? It would seem the dual pump setup wouldn't be the limiting factor at this hp level. Ive been reading up on all your posts. Will definitely save me a bit of time in my quest for more hp

 

I am no electrical engineer, but.....

Unless you run the wires all the way from power source to pump, you are still running all the power through the original, smaller gauge wires for the short distance out of the fuse block and into the fuel tank to the pumps.

This doesn't really help your power supply situation.

Kind of like building an eight lane highway to bypasses a gravel road, but them running it back into the gravel road at the end.
Vector

 

Exactly what i was going to say. From an electrical point of view, it do not make any sense

 

Doesn't matter to me anymore since I'm now running stock pulleys. I'm actually in the process of putting the car back completely stock.

Even though I've just finished updating everything, new primary and 2ndary tensioners, all new hoses, brakes, tires, etc, etc, etc, etc, I'm thinking of selling this XJR and keeping the XJ8 because when the wife and I ever travel any distance, We always take the pretty blue XJ8 with the softer suspension and doggy, my co-pilot gets to ride in the back. I've put less than 1500 miles on the XJR in the last year. It is a true garage queen.

I've access to the 2700 lb, 580 RWHP Pantera for all out track days, the X308 XJ8 for comfortable trips, and believe it or not, I just picked up a new little toy car, modified little red Miata which is a surprisingly fun car/go cart. It's like a real car, only smaller. If the brakes fail, you can just reach out and grab the tire to stop. Everything is tiny, I bought some super light 8.6 lb wheels for it.