recently noticed the car falls flat at around 5000rpm to redline.
iv checked iats and there fine. Intercooler pump is fine. Air intake is standard.
any thoughts

car has mid length headers
fixed 74mm pulley
race cats
split cooling
killer chiller.

No codes at the moment but that is just checked by icarsoft.

gona pick up a fuel pressure tester and check fuel pressure early next week

This is the Dyno graph. Power does flatten off at 5500. Does this look like a normal power curve.

I purchased the car about 4weeks ago with the mods already done.

What are your iats when going on the pull ?

My max iat was 102f on 2nd-3rd gear pull. I’m in uk so it’s pretty cold at the moment at 42f.

i did just lift the bonnet and found that one of my intake tubes from the radiator to the air box wasn’t on at the radiator end properly And was pretty much closed up. So Iv sorted that out and will try it again tomorrow.

Check iat at top of 3rd gear pull

Read codes today on ixarsoft and came up lean bank 1 and lean bank 2. Going to smoke test tomorrow to see if I got any vacuum leaks.

Done smoke test no air leaks.

Done fuel pressure test and have 75psi. Could this be the problem as it should be 80psi

Another member and I fought this exact same problem for a long Time earlier this summer. It turned out to be aftermarket intake tube is collapsing where they connect near the radiator. The stock ones may do that as well. You should get a code with star for intercooler mechanical failure.

What happens if you keep it WOT & let it shift?

If I wot in 2nd it will pull like a train upto about 5000rpm. Then you will feel a significant drop in power as the revs increase further then it changes into 3rd then pulls like a train again until you get to around 5000rpm again. Surely these engines should pull to redline.
I’m going to remove the intake tubes and try that but I’m running standard intake tubes and can’t imagine that they are closing up.

Do do you think my standard injectors can cope. Not sure what the bhp they can handle. Or could it be belt slip. I do have a brk though.

This is EXACTLY what happened to me & another member. The tubes collapse under high boost, the supercharger completely cuts out and then after it shifts starts building pressure again. Remove the tubes and take it for a run, or put it back on the Dyno and see if you can watch it happen. You’re pulling a lot of air, especially with Pully and exhaust mods. I bought my car with this issue. the previous owner had given up on it. It took me three months to figure it out with the help of the forums.

Can you run these without the tubes safely. Or can you buy upgraded tubes.
Even the standard ones can collapse.

You can run it without the tubes to test our theory, but long-term you most likely don’t want to be sucking hot engine compartment air. I’ve been told the stock tubes are fine if they are properly installed on the Fittings behind the radiator. Make sure that everything fits tightly and maybe check your engine mounts to be sure they’re not worn out to the point where The engine is moving enough to pull the tubes off.

I think you was right about the intake tubes.

because my car has split cooling they have fitted a little reservoir for the intercooler circuit. But where they have fitted it the left hand intake pipe keeps coming of the radiator connection and pushing to the right causing it to be only on by half.

also the left hand intake boot on the throttle body is slightly distorted and slimmer than the right hand one so I recon that could be squeezing up as well.

Just by removing the left intake tube the car pulled much stronger past 5000rpm.

Wat is the best route to take as far as intake upgrades.

mine wont even go on properly due to this reservoir. So I’m going to move it to new location and fit intake tube properly. I would rather keep stock intake to be fair instead of going aftermarket.

I assume the small tank you’re referring to was probably the BMW power steering reservoir most people use. A lot of guys mount them in front of the radiator. If you re locate it, make sure you bleed your system. See the attached link If you end up needing new motor mounts.

http://eastcoasteuro.com/services/