Since our fuel systems are vacuum regulated, it really depends on engine vacuum at that load. (and of course vacuum leaks)
​​​​​It would make sense that a heavy load would drop vacuum, therefore opening the regulator and lessening the restriction, and since pressure is a measurement of restriction you should see some drop. And IMO what you saw wasn't that far out of norm.
But.. The real question should be, how long did that drop last, and did it fluctuate or decline within the length of the pull.
​​​​​​
The factory fuel pump should produce about 62 psi off the pump, the most you'll read off the Schrader Valve on the fuel rail is about 56-58 with the car idling (high vacuum, high restriction) I've seen my fuel pressure dip into the 40's for short periods early under WOT in the lower RPM'S, and then come back into the low to mid 50's.

I'd change the filter if nothing more than to take it out of the equation since it's not that expensive to do and has more to do with quality of fuel than overall millage.
Plus with those AFR's being so dangerously high (you want t to be 12.5 MAX for a very short period, at your boost levels) it may be a flow issue not a pressure issue.

Oh... As for the use of the 550cc injectors.
While the Cam, Header and S/C porting "may? Cause you to be at the limits of a set of 380's, it will definitely Max out a set of 330's, so future-proofing with the 550's would probably be money well spent. Esp. since the use and scaling of those had been figured out for years now.

didn't see that you had a 15% pulley.

Recommended approach, in this order:
- burn thru an entire tank of fuel
- while the injectors are being cleaned/replaced, replace fuel filter
- get injectors cleaned or replaced
- replace air filter
- fill it up
- get car re-dynoed at the same dyno, preferably under same weather conditions, keep an eye on AFRs -- compare your difference in dyno runs.

[Edit: changed order -- as a precaution for spills]

If you can do the compression and leakdown test cheaply/free... do it. It's good to have that data on hand, for tracking of it in the future. But, it's not likely to tell you the issue you're having, since your AFRs are rather high for an engine under load. I like to do compression/leakdown tests every year, as a part of my annual service on my vehicles, including oil analysis for every oil change. Like an annual physical for your engines.

Your '06 S was factory rated at 168hp, 162tq. Given a 15% driveline reduction, you should net out around 143hp at the wheel so you're not that far off a stock MINI. Compression loss could explain that. The fact that you're running a CAI and a 15% pulley and still not pulling more than stock numbers is a conundrum. A tune would absolutely be your best path forward. I run the same mods ('04 MC40) as your current car and a tune added 18hp (dynoed before/after). I also switched from an EMS2000 (pre-facelift) to MS5150 (post-facelift) ECU before the tune since the later ECU provides more tuning capacity. Touch base with "adriancl" on this forum for advice. He's remotely tuned around 40 MINI R53s on this site and knows his way around an R53.

Try cleaning the tmap sensors and then the 02 sensors..you'd be surprised how much power you get back when it's accurately monitoring air n fuel trims... and thinking about that , do you have inpa ? You should reset your fuel adaptions and trims as well as 02 monitors. I even have a 2nd inpa cable WITH the switch and install cd . Throw me 20$ plus shipping you can have it AND the injectors. You can also pm Adriancl and he's a MASTER with tuning and stuff and he could definitely help you plus if your looking for a tune. I HIGHLY HIIIIIIIIIIIGHLY SUGGEST using Adriancl .
also I didn't see it BUT are you running a step colder spark plug ?

Wow, thanks again for the input. I was surprised to hear that my pressure numbers weren't a concern. I was expecting to hear that they were low and to be concerned.

As advised I am going to replace the fuel filter. Cheap insurance. Then I'll work into the mods.

I will compression test this week. Fingers crossed the numbers are strong. I am now beginning to wonder if the lean numbers have anything to do with the stock tune and the 15% pulley?

I have already reached out to Adrian. But my purchase from Jan included a tune so I am going to start there. It's great to have support like Adrian. I have heard only good things.

FYI: I have usually seen a recommendation that the fuel level be 1/2 tank or less when changing fuel filter or pump, in order to reduce spillage. (Any spills will be inside the vehicle.)

Finally got to compression test today. I had two gauges and they both read differently. Go figure.

Cyl 1 - 145psi
Cyl 2 - 145psi
Cyl 3 - 135psi
Cyl 4 - 150psi

I couldn't get the gauges I had tight into the head because of the spark plug tubes vs a surface mounted plug. I was only able to hand tighten the rubber extension through the spark plug tube.

Nonetheless, no 3 was consistently low. I think with a better compression test I would see maybe 10 points higher. I did try dripping some oil in the no3 to see if compression increased. I saw about 145.

So there it is. At this point I'm lowering my expectations but moving forward with mods. I had planned a built motor for this car. It looks like that might be sooner than later if compression should be greater than 150 across the board on this engine.

Brad

This is the first time I've done a compression test solo. Just realized I botched it pretty badly. Engine was dead cold and I forgot to open the throttle. Maybe it's better after all. I'm obviously borderline even for a shade tree mechanic.

I was going to ask if those were cold or warm numbers, then I saw your followup. Will be interested to see updated readings.

So I thought I'd update. I know that aesthetics are each person's taste. I have tackled a lot since the last post. Cleaning everything up and adding a lot of updated and new parts.

Parts included since this thread started is as follows; new fuel filter, Ported and ceramic coated intake with phenolic gasket,. Ph2/dominator cam,. Rmw header, m7 aero blanket, msd wires, brisk plugs, painted valve cover, 550cc injectors, ported and ceramic coated right side supercharger snorkel, rebuilt, ported m45 supercharger, TPE charge pipe, vibra technics mount, gtt catch can and pro alloy tmic.

I am going to finish putting the car back together in the next few days. Hopefully I'll be able to get it running on the canned rmw tune. Then it's back to the Dyno to see if the fueling issues are resolved. I'll tweak the tune with either rmw or Adrian.

I just thought I'd drop in an update even though there isn't a whole lot to report yet.

I did want to mention that installing the pro alloy intercooler was a bear. There may be a secret and I just didn't figure it out. But I did finally get it installed. I really hope I don't have to take it off. I looked the end tank and built in snorkel design and thought it made sense. However, having to line up the studs on the intake manifold, the bypass valve, and the passengers side snorkel was not easy. The perceived fragility of the TPE duct pipe also left little ability to bend or massage the duct pipe. Like I said, I really don't look forward to having to take it off again at some point.

^^^ Shown aesthetics are very nice! For reasons stated with your Pro IC, I'm not anxious to remove my water-to-air IC, WRT coolant plumbing and related loss/burping simply with objective of "looking deeper" to determine details how my engine was modded long ago. The risk/reward thing compels me to leave it alone, however I continue to enjoy your own discovery and upgrade progress!

That's quite an update. Looks great! What paint did you use on the valve cover?

I have enjoyed your thread and am jealous of your car. Bought my low ish mileage 06 with the idea of building it exactly how I wanted. Not the best route for the pocket book! I've already spent 2x what I paid for the car in parts alone. But when finished it will be like new and I'll have done everything myself. It's a fun project to start out retirement. The costs involved aren't for the faint of heart though.

this is what I used. I've had great luck with vht caliper paint on my Porsches. I thought I'd try it on my valve cover. I think it looks great and I stink at paint work. Basically I'm a hack at everything, but I do my best.

I think it looks great too. Congratulations on how your build is coming along. Great start to your retirement. I'm about 2 1/2 months from retiring and looking forward to spending more time working on the Mini (and anything else that I feel like doing).

Quick update. I was putting everything back together when I noticed the fan assembly was touching the TPE duct/charge pipe. I added their spacers then added additional ones at the upper driver's side radiator mount. I was hoping to get more room, but the screw on the fan assembly just touches.

I contacted TPE who was very responsive and he advised additional spacer/ compensating plates. Those are ordered now.

Moral of the story. This is why TPE says no aftermarket radiator. There's no room. I'm stock and it's still gonna be really snug. It makes a lot of sense why the factory duct pipe has a big ole flat section in it.

Thank you for that valuable info!
I'm still considering the TPE charge pipe. Seeing that my Mini is my daily and I don't have a garage - It's really nice to know what I'd be getting into.
BTW: Beautiful work on your resto!

Swapped out the fuel filter today while I wait on the spacer plates. Attached are a couple of pics. I'm starting to put 2 plus 2 together on this car. I am guessing that premium fuel was used sometimes but likely not routinely. I think maintenance was minimal and consisted of oil changes and air filters. Lots of aluminum oxidation, luckily zero rust. When I'm done everything will be new so it's a moot point.

Back to the filter. It was filthy. Even the fuel stained my hands black. Between the injectors and fuel filter I think I found my restriction. Here's hoping I installed it all correctly.

Unfortunately, that's probably how 95% of all R53 filters look.
That's because the local "quickie-lube" is not going to offer a fuel filter change on a Mini.

That's what my fuel filter looked like as well. It seems that the previous owners of your car and mine had a similar maintenance philosophy. The air filter in my car was the worst I've ever seen. I'm surprised the car ran at all.

Word of caution: When reinstalling the filter assembly ensure that the top is twisted and locked completely in place (it's difficult to accomplish). Took me three times to get it right (you'll think it's sealed but it's not). Your car will not start unless the seal is perfect.

Thanks for that. I am not sure it's locked completely. I twisted as hard as i could. Is there a way to know that it's locked properly? Will it be obvious that it's the fuel filter, ie leaking etc if the car won't start? I appreciate the help.

Likely obvious that I haven't done this R&R but would a rubber strap wrench help?

H-F Rubber Strap Wrench Set, 2 Pc.

I think that's a great idea. I'll pick up a set today and try again.