V3 no longer virgin

How will I know if I have belt slip? What will the telling symptom be?

I know this post could spark a discussion about injector size and if so, thats fine. But, thats not what I'm after. I did some more testing tonight. I have good info, mainly because the air was cooler and denser tonight. I don't have any info about max boost yet, as I'm still focusing on AFR readings.

Disclosure: My 30lb injectors are maxed, especially if the fuel pressure is set at stock level (39psi hose off is stock, but you know that) . However, my FP is turned up above stock (50psi hose off) and the AFR prior to the pulley change had never went leaner than 11.5 at WOT redline. The chip was initially base tuned by All Out and I'm ecstatic about its performance and from the seat of my pants, I cant see how it can be improved upon. The rebuilt 302 is race balanced. The crank, damper and flywheel were balanced together as an assembly and all rods and pistons were matched in weight. Block and heads decked, Cometic, ARP head studs, blah blah blah.....

I gain info about AFR performance via PLX wideband O2 that I have installed. I have not turned up the pressure any higher since the pulley change, but I could if needed. On pulls to redline this evening I saw AFR lean up a tad (expected since smaller pulley would increase boost). Initially it was getting to 12.1 when the engine was cooler, earlier in the testing trip. Then, as I continued and the engine got a bit hotter the AFR enriched a bit to 11.8. Again, these numbers are WOT redline 6000-6200.

I know I should have bigger injectors so I wont argue about that. However, my PLX wideband is giving me real world data which I think I can trust. And 12.1 is on the edge but not critical right? I could crank the pressure up some more and richen it up. So, should I add some pressure to richen up a tad or am I safe at 12ish WOT redline? My timing is at base 10 degrees (spout out) as per All Out recommendation. I could drop that back too for safety I suppose.

I'm ready to stare at boost readings, but not until I'm convinced my AFR is safe.

a91what said:

FWIW I have run a hyper piston engine at 12.5afr and 24* timing making 10psi...
Not ideal for safety but made good power.

If you were above 12.3 I would be very hesitant, but it's hard to give good advice without knowing how much boost.
I like to keep anything above 10psi around 11.5

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Thanks for the response in context. I’ll take it as one vote to nudge the FP up a tad.

I’ll get some boost numbers soon.

I put the pressure gauge on the car. Beginning pressure with hose off is 50psi. I get 2lbs increase in pressure per 1/4 turn on the regulator. I took it up to 55psi and ready for a test drive. Post back soon.

I forgot to post that last message so this response will seem sooner than it should be, but here goes.

3/4 turns on FP regulator got me into the 10.9ish in AFR at wot. Here’s the vid. So, I dialed it back 1/4 turn and I’m now 11.3ish.

This is a 4th gear pull from 60 to 110mph.

View: https://youtu.be/ipaWNTMc1ss

Here’s another pull showing max boost. This is a hot engine and 82 degree ambient temperature. I’m sure cooler weather and cooler engine would yield more. But this test maxed at 9.9psi. This was a third gear pull from 40 to 75mph.

View: https://youtu.be/FxUNs_WXNAw

30lb SVO injectors (4 hole)

a91what said:

That is alot of fuel pressure.... remember that when under boost you are adding that much fuel pressure as well. so at full tilt you are running somewhere around 65psi of fuel pressure.... no bueno for the pump my friend....

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If it’s set at 54psi with hose disconnected, how does that translate into 65 psi under boost? Are you saying that the regulator sees the boost and increases the pressure beyond the (hose off) set point?

RangerJoe said:

Cool to see old school fuel pressure bump working for you. Does this mean that the injector is 100% duty cycle?

Joe

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Yes, the injectors are maxed out. So FP adjustments are letting me fine tune the AFR on the top end. I’ve discovered 1/4 turn on the regulator screw gives me about .4 in the AFR.

a91what said:

Yes [if the car is running with the hose connected]
vacuum lowers the pressure and boost raises it.
2" vac usually = -1 psi fuel pressure
1psi boost = +1 psi fuel pressure

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I will heed your caution on possibility of overworking the pump. I’ll check the specs on my particular pump and see if it’s up to snuff. Although the stock FP setting was designed to be lower for this car, there has to be other automotive applications that run higher pressure. So I’ll see if my pump is built to handle the extra work I’m putting it through.